Foram utilizados 192 leitões Daland de 15,68±1,48 kg de peso vivo dos 49 aos 132 dias de idade em um experimento com o objetivo de avaliar a utilização de um complexo enzimático em dietas e seu efeito sobre o desempenho e rendimento de carcaça . Os animais foram distribuídos em 48 baias, sendo cada unidade experimental composta por quatro leitões. O delineamento experimental utilizado foi o de blocos ao acaso em esquema fatorial 2 x 3: dois sexos (machos e fêmeas) e três níveis nutricionais (convencional, reduzido + complexo enzimático e reduzido) totalizando seis tratamentos com oito repetições. Os tratamentos foram: TCM Dieta basal controle para machos, TRM Dieta reduzida para machos, TEM Dieta reduzida com adição da enzima fornecida para machos, TCF Dieta basal controle fornecida para fêmeas, TRF Dieta reduzida fornecida para fêmeas e TEF Dieta reduzida com adição da enzima fornecida para fêmeas. A redução nutricional foi de 110 kcal/Kg, 0,15 % de fósforo disponível, 0,16% de cálcio e 1,4% em todos os aminoácidos e proteína. A ração experimental foi constituída de milho, farelo de soja, vitaminas e minerais mais a adição do complexo enzimático (50g/ton), para alguns tratamentos. As características zootécnicas avaliadas foram o ganho de peso (kg), o consumo de ração (kg) e o índice de conversão alimentar. Todos os animais foram pesados no início e no final de cada fase, ocasião em que também foi realizado o controle do consumo das rações experimentais. Também foram avaliadas a tipificação de carcaças pelo método SEUROP. Os resultados demonstraram que o uso de carboidrases+fitase é uma ferramenta nutricional muito importante para a nutrição de leitões, pois melhora as suas características produtivas. Além disso, foi importante observar que os leitões, machos e fêmeas, apresentam comportamentos diferentes quando recebem o complexo enzimático. / One hundred ninety two piglets Daland, 15.68 ± 1.48 kg body weight, from 49 to 132 days of age were used in a trial with the aim of evaluate the use of a enzyme complex in the diet on performance and carcass yield. The animals were divided into 48 pens with four piglets each. The experimental design was randomized blocks in factorial 2 x 3: two sex (male and female) and three nutrient levels (conventional, reduced + enzyme complex and reduced) totalizing six treatments with eight replicates. The treatments were: TCM Basal diet control for males, TRM - Diet reduced for males, TEM - Diet reduced with the addition of the enzyme for males, TCF - Basal diet control for females, TRF - Diet reduced for females and TEF Diet reduced with the addition of the enzyme for females. The reduction on nutrition levels was 110 kcal / kg of energy, 0.15% of phosphorus, 0.16% of calcium and 1.4% for all amino acids and protein. The experimental diet consisted of corn, soybean meal, vitamins and minerals plus the addition of the enzyme complex (50g/ton), for some treatments. The husbandry characteristics evaluated were weight gain (kg), feed intake (kg) and feed conversion ratio. All animals were weighed at the beginning and end of each phase, at which was also performed to control the consumption of the experimental diets. We evaluated the classification of carcasses by the method SEUROP. The results demonstrated that the use of carbohydrases + phytase is an important nutritional tool for the nutrition of pigs because it improves their performance. Furthermore, it was important to note that the piglets, male and female, behave differently when they receive the enzyme complex.

Made available in DSpace on 2017-07-10T17:47:56Z (GMT). No. of bitstreams: 1 Edson_Richart.pdf: 998274 bytes, checksum: 1e2e2ed50b8a45af5839a0ad5d66aef4 (MD5) Previous issue date: 2013-08-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In order to conduct a nutritional evaluation of meal from tilapia filleting industrial waste (FRIFT) for barrows from 15 to 30 kg, three experiments were accomplished: energy digestibility, amino acids digestibility and animal performance. In the first experiment, the chemical composition and digestible and metabolizable energy of FRIFT was determined, using eight crossbred barrows with average initial weight of 15.10kg ±0.74kg were used, which were distributed individually in metabolism cages. The experimental design was completely randomized with two treatments and four replicates per treatment. The FRIFT replaced 20% the reference diet, based on corn, soybean meal, vitamins, minerals and amino acids. The experimental period lasted 12 days, of which seven to adapt to the cages and the experimental diets and five days for collection of urine and feces. The values of fat, Ca and P of FRIFT, corresponding to 16.82, 6.98 and 3.52%, were higher than those found in the literature. The values of digestible and metabolizable energy of FRIFT corresponded to 3,632 and 3,260 kcal/kg, respectively, for crossbred barrows from 15 to 30 kg. In the second experiment, the coefficients of ileal digestibility of amino acids of FRIFT were determined, having been used 8 crossbred barrows, with an average initial weight of 15.00 ± 0.27 kg, in a completely randomized design with two treatments and four replications and the treatments consisted of a basal diet whose the only protein source was FRIFT, and other protein-free diet, in order to determine the excretion of endogenous amino acids. The basal diet was formulated with sugar, starch, rice hulls, soybean oil, vitamins, minerals and additives. The chromic oxide was used as an indicator in determining the digestibility coefficients. The animals were fed twice daily, based on metabolic size, during 6 days. The pigs were then submitted to the collection of ileal digesta, by the method of sacrifice. The dry matter, crude protein, amino acid and chromic oxide of digesta, rations and feeds were determined. The endogenous loss of amino acids was variable, as leucine and threonine showed the greatest losses, of 33 and 28 mg / kg DIP consumed, respectively. The coefficients of true ileal digestibility of amino acids of FRIFT for arginine, lysine and methionine were 84.46, 76.60 and 82.43%, respectively, similar to those proposed in contemporary literature. In the third experiment, the growth performance and economic were evaluated for barrows fed diets containing different levels of FRIFT. A total of 40 crossbred barrows with an initial weight of 15.00 ± 0.87 kg were used in a randomized block design, with five treatments (0, 5, 10, 15 and 20% FRIFT), 4 replicates and 2 animals per experimental unit, distributed in treatments based on kinship and initial weight. The animals were housed in demonstrative experimental nursery endowed with elevated metal pens, polypropylene floor and screened sides, equipped with semi-automatic feeders and nipple drinkers, located in masonry building. The experimental diets were formulated based on corn, soybean meal, minerals, vitamins, amino acids and additives. Levels of 0 to 10% of FRIFT inclusion in the diets did not affect the final weight (FW) and average daily gain (ADG) of pigs by Dunnett test (P<0.05), but 15% of FRIFT inclusion resulted in decrease of FW and ADG. The average values of feed conversion (FC) were different (P<0.05) by Dunnett test only for the highest level of FRIFT inclusion in relation to the reference diet. For this level (20% FRIFT), there was increase in FC and therefore worsening in pigs performance. There was decreasing linear effect of levels of FRIFT on variables FW (P=0.01), ADG (P=0.01) and increased linear effect on FC (P=0.01). There was no difference (P>0.05) for the total cost of ration (TCR) in any level of inclusion of FRIFT by Dunnett test, compared with the reference diet. Even though, the proportional gain of pigs (PGP) and bioeconomic index (BI) had the best results (P<0.05) only for the reference diet, and 5% of FRIFT has worsened in results. The ratio proportional gain of pigs: feed cost (PGP:FC) worsened (P<0.05) with 10% of FRIFT inclusion in the diets. Levels up to 10% of FRIFT inclusion in diets for barrows from 15 to 30kg, replacing soybean meal, did not harm the ADG and FC of the animals. However, the inclusion of 5% FRIFT impaired the economic performance, making it impracticable to include this food in diets for starting pigs / Com o objetivo de realizar uma avaliação nutricional da farinha dos resíduos industriais de filetagem da tilápia (FRIFT) para suínos, machos castrados, dos 15 aos 30 kg, foram realizados três experimentos: digestibilidade da energia, digestibilidade dos aminoácidos e desempenho zootécnico. No primeiro experimento, foi determinada a composição bromatológica e os valores de energia digestível e metabolizável da FRIFT, utilizando-se 8 suínos, com peso médio inicial de 15,10kg ± 0,74kg, os quais foram distribuídos individualmente em gaiolas de metabolismo. O delineamento experimental foi inteiramente casualizado, com dois tratamentos e quatro repetições por tratamento. A FRIFT substituiu em 20% a ração referência, à base de milho, farelo de soja, vitaminas, minerais e aminoácidos. O período experimental teve duração de 12 dias, dos quais sete de adaptação às gaiolas e às rações experimentais e cinco dias de coleta de urina e fezes. Os teores de gordura, Ca e P da FRIFT, correspondentes a 16,82; 6,98 e 3,52%; foram superiores aos encontrados na literatura. Os valores de energia digestível e metabolizável da FRIFT corresponderam a 3.632 e 3.260 kcal/kg, respectivamente, para suínos mestiços, machos castrados, dos 15 aos 30 kg. No segundo experimento, foram determinados os coeficientes de digestibilidade ileal dos aminoácidos da FRIFT, tendo sido utilizados 8 suínos, mestiços, machos castrados, com peso médio inicial de 15,00 ±0,27 kg, em delineamento experimental inteiramente casualizado, com dois tratamentos e quatro repetições, sendo os tratamentos constituídos de uma ração basal, cuja única fonte protéica era a FRIFT, e outra ração sem proteína, com a finalidade de determinar a excreção endógena de aminoácidos. A ração basal foi formulada à base de açúcar, amido, casca de arroz, óleo de soja, vitaminas, minerais e aditivos. Utilizou-se o óxido crômico como indicador na determinação dos coeficientes de digestibilidade. Os animais foram arraçoados duas vezes ao dia, com base no tamanho metabólico, durante 6 dias. Os suínos foram então submetidos à coleta das digestas ileais, pelo método do sacrifício. Foram determinados os valores de matéria seca, proteína bruta, óxido crômico e aminoácidos das digestas, rações e dos alimentos. A perda endógena de aminoácidos foi variável, sendo que leucina e treonina apresentaram as maiores perdas, de 33 e 28 mg/kg de DIP consumida, respectivamente. Os coeficientes de digestibilidade ileal verdadeira dos aminoácidos da FRIFT, para arginina, lisina e metionina foram de 84,46; 76,60 e 82,43%, respectivamente, sendo semelhantes aos propostos na literatura contemporânea. No terceiro experimento, foi avaliado o desempenho zootécnico e econômico de suínos alimentados com rações contendo diferentes níveis de FRIFT. Foram utilizados 40 suínos, com peso inicial de 15,00 ±0,87 kg, distribuídos em um delineamento experimental de blocos casualizados, com 5 tratamentos (0; 5; 10; 15 e 20% de FRIFT), 4 repetições e 2 animais por unidade experimental, distribuídos nos tratamentos com base no parentesco e peso inicial. Os animais foram alojados na creche demonstrativa experimental, dotada de baias metálicas suspensas, piso de polipropileno e laterais teladas, dotadas de comedouros semi-automáticos e de bebedouros tipo chupeta, localizada em prédio de alvenaria. As rações experimentais foram formuladas à base de milho, farelo de soja, minerais, vitaminas, aminoácidos e aditivos. Níveis de 0 a 10% de inclusão de FRIFT nas rações não alteraram o peso final (PF) e o ganho de peso diário (GPD) dos suínos, pelo teste de Dunnett (P<0,05), sendo que a partir de 15% de inclusão de FRIFT já houve decréscimo no PF e GPD dos animais. As médias da variável conversão alimentar (CA) diferiram (P<0,05), pelo teste de Dunnett, apenas para o último nível de inclusão de FRIFT em relação à ração referência. Para este nível (20% de FRIFT), houve aumento no valor da CA e, portanto, piora no desempenho os suínos. Houve efeito linear decrescente dos níveis de inclusão de FRIFT sobre as variáveis PF (P=0,01), GPD (P=0,01) e efeito linear crescente sobre a CA (P=0,01). Não foi observada diferença (P>0,05) para o custo total da ração (CTR) em nenhum dos níveis de inclusão de FRIFT, pelo teste de Dunnett, quando comparados com a ração referência. Ainda assim, as variáveis ganho proporcional de suínos (GPS) e índice bioeconômico (IBE) apresentaram os melhores resultados (P<0,05) apenas para a ração referência, sendo que a partir de 5% de inclusão de FRIFT já houve piora nos resultados. Já a relação ganho proporcional de suínos:custo da ração (GP:CR) apresentou piora (P<0,05) a partir de 10% de inclusão da FRIFT nas rações. Níveis de até 10% de inclusão da FRIFT, em rações para suínos, machos castrados, dos 15 aos 30kg, em substituição ao farelo de soja, não prejudicaram o GPD e a CA dos animais. Entretanto, a inclusão de 5% de FRIFT influenciou negativamente as variáveis de desempenho econômico, tornando inviável a inclusão desse alimento em dietas para suínos na fase inicial

Foram utilizados 192 leitões Daland de 15,68±1,48 kg de peso vivo dos 49 aos 132 dias de idade em um experimento com o objetivo de avaliar a utilização de um complexo enzimático em dietas e seu efeito sobre o desempenho e rendimento de carcaça . Os animais foram distribuídos em 48 baias, sendo cada unidade experimental composta por quatro leitões. O delineamento experimental utilizado foi o de blocos ao acaso em esquema fatorial 2 x 3: dois sexos (machos e fêmeas) e três níveis nutricionais (convencional, reduzido + complexo enzimático e reduzido) totalizando seis tratamentos com oito repetições. Os tratamentos foram: TCM Dieta basal controle para machos, TRM Dieta reduzida para machos, TEM Dieta reduzida com adição da enzima fornecida para machos, TCF Dieta basal controle fornecida para fêmeas, TRF Dieta reduzida fornecida para fêmeas e TEF Dieta reduzida com adição da enzima fornecida para fêmeas. A redução nutricional foi de 110 kcal/Kg, 0,15 % de fósforo disponível, 0,16% de cálcio e 1,4% em todos os aminoácidos e proteína. A ração experimental foi constituída de milho, farelo de soja, vitaminas e minerais mais a adição do complexo enzimático (50g/ton), para alguns tratamentos. As características zootécnicas avaliadas foram o ganho de peso (kg), o consumo de ração (kg) e o índice de conversão alimentar. Todos os animais foram pesados no início e no final de cada fase, ocasião em que também foi realizado o controle do consumo das rações experimentais. Também foram avaliadas a tipificação de carcaças pelo método SEUROP. Os resultados demonstraram que o uso de carboidrases+fitase é uma ferramenta nutricional muito importante para a nutrição de leitões, pois melhora as suas características produtivas. Além disso, foi importante observar que os leitões, machos e fêmeas, apresentam comportamentos diferentes quando recebem o complexo enzimático. / One hundred ninety two piglets Daland, 15.68 ± 1.48 kg body weight, from 49 to 132 days of age were used in a trial with the aim of evaluate the use of a enzyme complex in the diet on performance and carcass yield. The animals were divided into 48 pens with four piglets each. The experimental design was randomized blocks in factorial 2 x 3: two sex (male and female) and three nutrient levels (conventional, reduced + enzyme complex and reduced) totalizing six treatments with eight replicates. The treatments were: TCM Basal diet control for males, TRM - Diet reduced for males, TEM - Diet reduced with the addition of the enzyme for males, TCF - Basal diet control for females, TRF - Diet reduced for females and TEF Diet reduced with the addition of the enzyme for females. The reduction on nutrition levels was 110 kcal / kg of energy, 0.15% of phosphorus, 0.16% of calcium and 1.4% for all amino acids and protein. The experimental diet consisted of corn, soybean meal, vitamins and minerals plus the addition of the enzyme complex (50g/ton), for some treatments. The husbandry characteristics evaluated were weight gain (kg), feed intake (kg) and feed conversion ratio. All animals were weighed at the beginning and end of each phase, at which was also performed to control the consumption of the experimental diets. We evaluated the classification of carcasses by the method SEUROP. The results demonstrated that the use of carbohydrases + phytase is an important nutritional tool for the nutrition of pigs because it improves their performance. Furthermore, it was important to note that the piglets, male and female, behave differently when they receive the enzyme complex.

Physicochemical properties of different fibrous ingredients were used to determine the influence of feed bulk on voluntary feed intake and gut capacity in weaner and finishing pigs. Physicochemical measures of bulkiness determined on feed ingredients were DM, crude protein (CP), ether extract, ash, water holding capacity (WHC), bulk density, crude fibre (CF), neutral detergent fibre (NDF) and acid detergent fibre (ADF). Among the fibre sources, maize stover had the highest WHC, followed by veld grass, then lucerne hay, maize cob, sunflower husks, groundnut haulms, rice bran and saw dust. The greatest bulk densities (1.4 g DM/ml) were observed in lucerne hay and saw dust, whilst sunflower husk had the lowest (0.7 g DM/ml) (P < 0.001). Rice bran, maize cob and groundnut haulms were the most fermentable fibrous ingredients (P < 0.05). Based on differences in physicochemical properties, six fibres namely lucerne hay, maize cob, maize stover, veld grass, saw dust and sunflower husk were selected and used in formulating fibrous diets fed to growing pigs based on wideness in ranges of their bulk properties. Thirty-one complete diets were formulated by dilution of a conventional weaner feed with increment levels of each fibre source at 0, 80, 160, 240, 320 and 400 g/kg. Each of the diets was offered ad libitum to four of 124 pigs weighing 18.1 (s.d. 1.37) kg body weight, in individual pens, for four weeks. There was a linear decrease in scaled feed intake (SFI) (P < 0.001) as bulk density of the feeds increased. There was a quadratic relationship between SFI and WHC, NDF and ADF, respectively, whereby SFI increased up to a point when it reached its maximum and then started to decrease as bulkiness increased (P < 0.001). By use of the broken stick model, the maximum SFI marking the gut capacity of pigs was attained when WHC = 4.5 ± 1.25 g water/g DM (P< 0.001), NDF = 367 ± 29 g/kg DM (P < 0.001) and ADF = 138 ± 77 g/kg DM (P < 0.01), respectively. The SFI decreased linearly with an increase in bulk density of the feeds (P < 0.001). Four of 84 finishing pigs in individual pens, at 65 (s.d. 1.37) kg body weight were given, ad libitum to each of 21 diets containing graded levels of lucerne, maize cobs, saw dust and sunflower husk. There was a linear decrease in SFI (P < 0.001) as WHC increased. There was a quadratic decrease in SFI as CF (P < 0.001) and NDF (P < 0.01) increased. As CP increased, there was a quadratic increase in SFI (P < 0.01). In weaner pigs, an increase in WHC, NDF, ADF and bulk density constrains feed intake, thereby providing relationships that can be used to predict gut capacity. Conversely, measurements of feed bulk cannot provide relationships with intake that can be used to predict gut capacity in finishing pigs. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg.

To study the effects of feeding and diet on postnatal development of the small intestine in newborn piglets during the time 0 - 24 hours after birth, three studies were conducted: 1. Unsuckled newborn piglets were fed from a bottle with colostrum or milk from either sows or cows, infant formula, or water. After 24 hours intestinal development was compared with that in piglets at birth and others naturally suckled. Sow colostrum caused greater increases in weight and length of the small intestine than did any of the other diets. The increases were due to mucosal cell swelling caused by cellular protein accumulation, hyperplasia and, in the duodenum, hypertrophy. Feeding sow colostrum increased mucosal lactase activity. Cow colostrum caused decreases in mucosal RNA levels. Increases in the DNA content of the intestinal mucosa occurred in all groups, including the water fed group. Colostrum feeding also enhanced pancreatic growth and feeding infant formula increased liver weight. 2. The effects of enteral feeding on small intestinal development were investigated by feeding nutrient solution to unsuckled newborn piglets by orogastric tube or parenterally. Both groups after 24 hours had greater intestinal development than did the piglets at birth. The development was most pronounced in the duodenum and lower ileum. Apart from a greater small intestinal length in the orogastrically fed piglets there were no significant differences between the orogastrically and parenterally fed groups. 3. To investigate the effects of sucking per se on small intestinal development, groups of unsuckled piglets were fed for 24 hours with either sow colostrum or infant formula by orogastric tube or being allowed to suck from a bottle. Sucking did not affect intestinal development whereas colostrum, regardless of how it was fed, had significantly greater effects on intestinal development than did infant formula. For the colostrum fed piglets the intestinal length, tissue weight, circumference, wall thickness, villous height and width, RNA content, protein:DNA ratio and RNA:DNA ratio were all significantly greater than for those fed infant formula. In the duodenum the estimated cell migration rate was faster and mucosal cell replacement time was shorter than in other parts of the small intestine, regardless of the diet fed. The greater villous height in the piglets fed sow colostrum was most likely due to the combined effects of cellular swelling and an increase in the number of villous cells. These results indicate that (a) sow colostrum causes cellular swelling related to colostral protein accumulation, cell hyperplasia and, in the duodenum, hypertrophy, (b) there is a basal rate of mucosal cell division which contributes to mucosal growth regardless of diet and method of feeding, (c) the duodenum exhibits a greater growth and sensitivity to the trophic effects of colostrum compared to other parts of the small intestine, (d) feeding cow colostrum to newborn piglets causes a pronounced decrease in mucosal RNA content and (e) diets affect postnatal development of the small intestine whereas the route or method of feeding has no significant effects on small intestinal development in piglets during the first 24 hours after birth.

Three experiments were designed to find the most efficient and cost-effective method of meeting the changing amino acid requirements of male and female pigs during the growing period, using the minimum number of feeds. Trial one involved 144, and trial two 192 commercial crossbred (Landrace x Large White) pigs, eight to a pen, with sexes separate. Trial three involved 24 commercial crossbred (Landrace x Large White) pigs and 24 Dalland pigs each penned separately. The amino acid requirements (g/d) for the pigs in all three trials were determined for male and female Landrace x Large White pigs, respectively, using the Pig Growth Model (EFO Software Natal, 1995). Parameter values used for males and females were: growth rate (B, Id) 0.0107 and 0.0120; protein at maturity (Pmat, kg) 39.0 and 28.0; and lipid at maturity (Lpmat, kg) 2.60 and 3.89 respectively. In trials 1 and 2 two iso-energetic (DE 13.8 MJ/kg) basal feeds were formulated; Basal A being a high crude protein (CP) (347g CP/kg) feed designed to meet the amino acid requirements of a male at 20 kg liveweight, while Basal B was a low protein feed (l34g CP/kg) designed to meet the amino acid requirements of a female at 88 kg, thus providing for the most- and the least-demanding pigs on the trial. In the third trial, two iso-energetic (DE 13.8 MJ/kg) basal feeds were again formulated; Basal A being a high crude protein (CP) (347g CP/kg) feed designed to be 20% higher than the amino acid requirements of a male at 20 kg liveweight, while Basal B was a low protein feed (l34g CP/kg) designed to be 20% lower than the amino acid requirements of a female at 88 kg, once again providing for the most- and the least-demanding pigs on the trial. Trials 1 and 2 began when the median weight of pigs in each pen reached 20kg, and were terminated at a pen median of 85 kg liveweight. In the third trial each pig was started on trial when it reached 20kg and was terminated at a weight of 85kg. The first trial involved a phase feeding schedule (20-40, 40-60 and 60-85kg liveweight). The two basal feeds were blended in different proportions to create three feeds per phase: lysine contents in each of the phases in Treatment 1 (TI) were: 11, 8.68 and 7.26g/kg; in T2 they were 9.93, 7.58 and 6.24g/kg; and in T3, 8.85, 6.48 and 5.22g/kg. From the analysis it was established that ADO and time to reach 85kg were the only variables to show significance. ADO exhibited a significant sex x treatment interaction. There were significant differences between treatments for time taken to reach slaughter weight. In addition to a treatment effect there was a sex x treatment interaction for time to slaughter weight. It was expected that males on Tl and females on T3 would exhibit the most efficient performance for their respective sex since these treatments were specifically formulated to meet their requirements. Midway through the trial the pigs contracted enteritis, this affecting the outcome of the trial by inhibiting the potential growth of the pigs. The results of the trial indicated that dietary protein level affected the time taken to reach slaughter weight. This led to the second trial where four treatments were applied. Three of the four treatments followed a fixed feeding schedule, making use of the two basal feeds and a 1: 1 blend of these. The fourth treatment followed a phase feeding schedule, differing between the males (20-65, 65-75 and 75-85 kg liveweight) and the females (20-35, 35-75 and 75-85 kg liveweight). This treatment also made use of the two basal feeds and a 1: 1 blend of these. From the analysis it was found that there were no significant effects of sex and no interactions between feeding treatments and sex; however, ADO, FI, FCE, back fat thickness, time taken to reach 85kg and cost/kg gain were all significantly affected by the feeding treatments. Carcass lean, carcass lipid and total body lipid were also significantly affected by the feeding treatment. This trial was conducted to determine the extent to which differences in growth rate, food intake and carcass lipid could be altered by dietary means. The effect of the level of feed protein was once again shown to be of importance when feeding growing pigs. The third trial was designed to test the efficiency with which two strains make use of the dietary protein supplied. Three treatments were applied: Tl was a choice-feeding treatment in which the pigs were offered the two basal feeds simultaneously. T2 and T3 followed a phase feeding schedule (20-40, 40-60 and 60-85kg liveweight). The two basal feeds were blended in various proportions to create three feeds per phase: the lysine contents in each of the phases in T2 were: 12.2, 10.0 and 7.26g/kg; and in T3 8.1, 6.7 and 5.1g/kg. There were significant sex effects as well as strain x feeding treatment interactions. All variables, ADG, FI, FCE, time taken to reach 85kg and cost/kg gain, with the exception of back fat thickness, showed significance. It was expected that the Dalland strain would perform better than the Cross strain; however, this was not the case, indicating the need for further research into the possibility of feeding according to the genetic makeup of the animal. The importance of meeting the amino acid requirements of the growing pig was evident when summarising the results of the three trials reported here. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

This study was conducted to determine the influence of factors on the efficiency of protein utilization and the rate of lipid deposition and withdrawal in growing pigs. Two experiments were conducted in total. The first experiment involved fifty-two crossbred entire Large White x Landrace male pigs, individually penned, which were used to test the proposition that the efficiency of protein utilisation is influenced by the body composition of the pig at the start of the trial. The experiment was divided into two phases: in the first period, starting at 20kg liveweight, when 3 pigs were slaughtered to determine the initial body composition of the pigs on the trial, the remaining 48 pigs were divided into three groups, two of which were fed ad libitum, with 11 pigs being offered a feed high in crude protein (HP, 1979 CP/kg) and 19 pigs being offered a low CP (LP, 166g/kg) feed. The remaining 19 pigs were fed HP on a restricted basis; the daily allowance being 0.7 of the mean intake of those pigs fed HP ad libitum. The objective of this initial period was to create three groups of pigs differing in body lipid content. As each pig achieved a protein weight of approximately 5.9kg, predicted to occur when the pigs on the three treatments reached live weights of 35, 39 and 34kg respectively, the pig entered phase 2 of the trial. At this stage three pigs from each treatment (a total of 9 pigs) were slaughtered for carcass analysis, the protein contents being approximately 5.9kg, and lipid contents being 85,98 and 87g/kg for the 3 treatments respectively. During phase 2, the 8 pigs fed HP in phase 1 continued to be fed HP in phase 2; 8 pigs were chosen at random from those fed LP in phase 1 and were allocated the high CP basal feed, while the remaining 8 were given LP; and 8 of the pigs feed-restricted in phase 1 were randomly chosen and fed HP, while the remaining 8 were given LP. All pigs were fed ad libitum during phase 2. Four pigs from each treatment in phase 2 were slaughtered after 1 week and the remaining 4 a week later for analysis of body composition In the first week of the second phase of the trial protein gain was highest (264g/d) on the pigs previously restricted and then fed HP, followed by those previously fed LP and then HP (242g/d), with pigs previously restricted and then fed LP depositing the least amount of protein (192g/d). Pigs fed LP or HP throughout, had protein gains of 217 and 210g/d, respectively. Efficiencies of utilization of dietary protein did not differ significantly between treatments, however, the highest being measured in pigs fed LP throughout (461g/kg), followed in order by those fed LP and then HP (457g/kg), those fed HP throughout (404g/kg), those previously restricted and then fed LP (394g/kg), with those previously restricted and then fed HP being the least efficient (372g/kg). The second experiment involved twenty-six male and twenty-six female crossbred Large White x Landrace pigs, individually penned, which were used to determine the maximum rate at which growing pigs can gain lipid. The experiment was divided into three phases: In the first, starting at 20kg live weight (56 days old), when two males and 2 females were slaughtered to determine the initial body composition of the pigs on the trial, the remaining 24 males and 24 females were randomly allocated to their various treatments. The treatments consisted of a feed high in crude protein (H, 197g/kg), a feed low in CP (L, 166g/kg) and three blends, namely 5OH/5OL (180g/kg) (male diet), 30H/70L (167g/kg) (both male and female diets) and 20H/80L (162g/kg) (female diet). Six pigs from each sex were allocated to each treatment. The EFG Pig Growth Model was used to determine the fat contents (lipid index) on the two feeds available and the three blends, to estimate the best times to sample pigs. It was estimated that phase 1 would terminate at 63 d, phase 2 at 70 d and phase 3 at 77 d of age. At the end of each phase two pigs from each sex and treatment were slaughtered. The lipid contents differed significantly between treatments at the end of phase 2 for the male pigs, with the highest being measured in pigs fed L (108g/kg), followed in order by those fed 70L/30H (86g/kg), those fed 5OL/5OH (74g/kg), and those fed H (68g/kg) with the least lipid content. The lipid contents of the female pigs were highly significantly different at the end of phase 3, with the highest being measured in pigs fed L (147g/kg), followed in order by those fed 80L/20H (124g/kg), those fed 70L/3OH (116g/kg) and the least lipid content from those fed H (115g/kg). As estimated by the EFG Pig Growth Model, the male and female pigs fed L treatment had the highest lipid content and those fed H treatment, achieving their target rate of lipid deposition, with the lowest lipid content. This study indicates that the response in protein gain and in efficiency of utilization of protein of pigs to a given feed is dependent on the amount and quality of the feed given to the animals previously. Also, the maximum rate of lipid deposition can be achieved by monitoring the changes in lipid deposition over a period of time, which enables an enhanced understanding of the theory of food intake regulation in a growing pig. As a result, accurate changes can be made when designing a phase-feeding program for growing pigs. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

The objectives of the research were to examine the effects of high dietary levels of fibrous feeds, and of supplementation with Roxazyme® G2 (RX), on the digestive metabolic and physiological responses of growing pigs fed maize-soybean diets. The nutrient and dietary fibre (DF) composition, the swelling and water-binding capacities of maize (MM), its hominy chop (HC) and cobs (MC), dehulled soybean (dSBM) and the hulls (SH), brewer’s grains (BG), lucerne hay (LH) and wheat bran (WB) were evaluated using standard procedures. Feed fibre fractions were isolated by simulating upper tract digestion in an Ankom® DaisyII Incubator, whereby each feed was digested in pepsin (porcine, 200 FIP-U/g, Merck No, 7190), followed by pancreatin (porcine, grade IV, Sigma No P-1750), with recovery of the fibrous residues. In a third step to complete the simulated pig gastro-intestinal digestion, the pepsin-pancreatin fibre extracts were digested by RX or Viscozyme L ® V2010 (VZ). Enzyme activity was measured as the coefficients of partial degradability (solubilisation) of the washed fibre extracts. The kinetics and products of fermentation of the DF were evaluated in an AnkomRF gas production system, using buffered faecal inoculum. Among the feed ingredients, dissimilar, fibre source-dependent activities between RX (0.02 to 0.12) and VZ (0.04-0.33) were observed. The lowest RX activities were observed on the maize and soybean derived fibres, with similarly low VZ activity on MC fibre. Variation in the activity of faecal microbial enzymes was similarly indicated by the variable production of fermentation gas (51.8-299.4 mL g-1 DM) and short chain fatty acids (SCFA) (2.3-6.0 mMol g-1 DM). Soy hull, dSBH, MM and HC fibres were highly fermentable, with low fermentability of BG, MC and WB fibres. The fibres differed in the composition of fermentation SCFA, whereby SH, LH and MC shifted fermentation to Ace, and BG, dSBM, WB, MM, HC favoured Pro, while MM and HC favoured But production. The same nutritional properties were similarly evaluated in complete diets which were formulated from the ingredients for growth, and metabolic trials. For the growth trial, a standard (STD) (control), 141 g total dietary fibre (TDF) kg-1 dry matter (DM) maize-soybean growing pig diet, and five iso-nutritive, 246 g TDF kg-1 DM nutritionally balanced diets were formulated. The high DF was achieved by partial replacement of the MM and dSBM in the STD diet with MC, SH, BG, LH or WB. The differences in RX and VZ activities and in the fermentation characteristics which were observed on the fibre extracts from the high fibre ingredients were reflected in the DF from the respective complete diets in which they were included. However, the fibre from the basal dietary ingredients reduced the absolute values and the variation in the activities of RX (0.03-0.06) and VZ (0.16-0.22), and similarly reduced the variation in gas (126.6-187.6 mL g-1 DM) and SCFA (4.1-5.4 mMol g-1 DM) production of the DF from the fibrous diets. Enzyme activities on the STD DF were low for RX (0.03) and high for VZ (0.25). The STD DF produced 205.3 mL gas g-1 DM, which was similar to SH DF, and higher than all the other diets. The STD DF produced 5.0-mMol SCFA g-1 DM, which was quantitatively, and not statistically higher than the other fibres. The composition of SCFA was similar across all diets, except for the high percent Ace, with low Pro by the SH DF. Compared to the STD, the high DF diets increased percent Ace, with reduced Pro and But. The STD, MC, SH, BG, LH and WB diets were each prepared in duplicate mixes, one of which was fortified with 200 mg RX kg-1 feed (as fed). Seventy-two intact Large White X Landrace, male, 32.0 ± 5.6 kg live weight (LW) pigs were allocated to the diets in two completely randomised weight blocks in a 2 (fibre source) X 2 (enzyme) factorial arrangement. The pigs were fed ad libitum for 10 weeks. Cumulative LW gain and feed intake were measured at different stages of growth, and at slaughter. Apparent total tract digestibility (ATTD) of nutrients was estimated at 65-70 kg LW, using 0.2% (as fed) chromium oxide as the indigestible marker. Ileal tissue was sampled 50 cm above the ileo-caecal valve, on which villi height and area, and crypt depth were evaluated by computerised image analysis. Blood was sampled at slaughter from the severed vena jugularis, 16 hours after feeding. Serum urea, creatinine, triglycerides, glucose, and total cholesterol were analysed chemically. The serum metabolome was further explored using Proton Nuclear Magnetic Resonance Spectroscopy (1H -NMRS). There was fibre X RX interaction for villi height, whereby the enzyme reduced the villi height in pigs on the SH, STD and WB diets, with an opposite effect on pigs on the MC, BG, LH diets. The soluble fibre content was negatively correlated with crypt depth. Chemical analysis did not detect differences in metabolite concentration between the STD and the high fibre diets. However, more serum cholesterol was observed in pigs fed the WB compared to the LH and MC diets. 1H-NMRS indicated that feeding pigs the WB diet increased serum Cys and His, while supplementation of RX increased serum formate, glucose, and urea. There was diet X enzyme interaction for fructose, glucose, Arg, Cys, Ser, and Trp, whereby RX increased the levels in pigs on MC and WB, with an opposite effect in pigs on the other diets. There was large DF source-dependent variation among diets in ATTD of DM (0.80-0.85), organic matter (OM) (0.81-0.87), gross energy (GE) (079-0.85) and CP (0.81-0.85), whereby, relative to the STD diet, high DF reduced the ATTD of DM (all diets except SH), organic matter (OM) and energy and CP (all diets except the MC). Positive correlation was observed between fermentability and the ATTD digestibility of DM, OM, energy, ADF, NDF, and fat. Negative correlation was observed between the swelling capacity and the ATTD of DM, OM, energy and protein, between DF solubility and DM, OM, protein, ADF and NDF, and between water binding capacity and ATTD of DM and OM, energy and NDF. At slaughter, there was similarly large, and DF source-dependent variation among the high fibre diets in feed intake (2.31-2.71 kg as fed day-1), live weight gain (0.75-0.86 kg day-1), and feed: gain ratio (2.73-3.00). Corresponding values for the STD diet were 2.44 kg day-1, 0.83 kg day-1and 2.86 kg day-1, respectively. Relative to the STD, LH reduced feed intake and live weight gain, and MC increased the feed: gain ratio. Predictions based on the in vitro fermentability of DF and feed intake suggested that due to poor fermentability, and or restriction of feed intake, relative to a standard fibre diet, high dietary levels of MC, WB and BG may reduce fermentation in the lower gut, while similar dietary levels of SH and LH may result in substantial increases in fermentation. At 50 kg LW, the fermentability of DF was positively correlated with feed intake and with weight gain, while water binding capacity and solubility of DF were negatively correlated with feed intake. At slaughter, the solubility of DF was negatively correlated with feed intake and feed: gain ratio. Large variation among the high fibre diets was also observed in the slaughter weight (89.2-96.8 kg), dressing % (68.6-76.4), meat colour (80.4-82.3), lean % (69.5-71.2), and fat % (10.1-12.6). In comparison, pigs on the STD diet scored 94.7 kg slaughter weight, 75.1% dressing, 81.6 cm carcass length, 82.5 meat colour, 68.4% lean, and 15.0% fat. Relative to the STD, LH reduced dressing and fat %. Lucerne hay and WB increased the lean%. For the metabolic trial, two iso-nutritive, mixed high fibre (319 g TDF kg-1 DM), nutritionally balanced diets were formulated to contain DF of high (HF) versus low (LF) fermentability. The diets had similar content of soluble DF and similar swelling and water binding capacities. Viscozyme was more active than RX on both the HF (0.20 versus 0.04) and the LF (0.17 versus 0.07) DF. The combination of RX and VZ statistically increased the enzyme activity on the HF (0.25) and quantitatively increased enzyme activity on the LF (0.18) DF, suggesting additive or synergistic effects. More gas was produced by the HF (159.5 mL g-1 DM) compared to the LF DF (96.6 mL g-1 DM). More SCFA were produced by HF (5.0 mMol g-1 DM), compared to the LF DF (3.6 mMol g-1 DM). Compared to the STD, HF DF increased percent Ace, with reduced Pro and But. The LF DF increased percent Ace, with quantitative, and not statistical reduction of Pro and But. In a metabolic trial, the HF and LF diets, and their duplicates containing 0.270 g RX kg-1 DM of feed (as fed) were fed ad libitum to eight ileum T-cannulised, intact Large White X Landrace male pigs weighing 65.0 ± 5.1 kg. The diets were allocated to the pigs in a duplicate 4 x 4 Latin Square design, in a 2 (enzyme) x 2 (fermentability) factorial arrangement. Each period consisted of two weeks of adaptation followed by five days of sampling. The ileal digesta was collected in each period and was similarly subjected to the fermentation test. Apparent ileal digestibility (AID) and ATTD were determined using 0.2% (as fed) chromium oxide as the indigestible marker. N excretion in faeces and urine were measured, and N retention was calculated. Blood was sampled by vena jugularis puncture on the last day of each period. Two blood samples were collected, the first 15 hours after removal from feed (15-hour serum), and the second 3 hours after re-introduction to feed (3-hour serum). Serum metabolites were evaluated by both chemical analyses and by 1H-NMRS, as described for the growth trial. Roxazyme did not affect the fermentation characteristics of the ileal digesta. In similar proportion to the fermentability of the PP digesta, the HF ileal digesta was more fermentable (65.4 mL gas g-1 DM and 6.1 mMol SCFA g-1 DM) than the LF ileal digesta (46.7 mL gas g-1 DM and 4.4 mMol SCFA g-1 DM SCFA). Prediction based on the in vitro fermentability of DF and feed intake suggested the HF diet could support one half times more fermentation in the lower gut compared to the LF diet. The HF diet had higher AID of DM (62.5 vs. 58.6), OM (65.6 vs. 62.1), energy (64.4 vs. 61.0), fat (85.8 vs. 81.7) and ash (41.8 vs. 32.7). The AID of HO-Pro, Met and Val were higher for the LF diet. There was diet X enzyme interaction on the AID of Met, whereby the RX reduced the AID of met in the LF diet, and not that of the HF diet. The ATTD was higher for the HF diet for DM (74.2 vs. 68.4), NDF (64.7 vs. 57.4), and ADF (35.1 vs. 21.0). There was positive correlation between the fermentability of DF and the AID DM, OM, ash, ash, fat and energy. The solubility of DF was negatively correlated with the AID of DM, OM, ash, fat, ADF and energy, and with the ATTD of DM, OM, ash, fat, energy, NDF, and ADF. Negative correlation was also observed between the swelling capacity of DF and the AID of protein, Trp and Lys. The solubility of DF was positively correlated with Ser, Ala, Val, Iso-Leu and His. There was diet X enzyme interaction for urea in the 15- hour serum, whereby RX tended to reduce the urea in the LF diet, while it increased that of the HF diet. Fermentability negatively correlated with urea in the 15- hour serum, and positively correlated with serum glucose in the 3-hour serum. In the 3-hour sample, 1H-NMRS indicated higher fucose, Pro and cholesterol in the LF diet. 1H-NMRS also indicated fermentability x RX interaction for Ser, Tyr, Lys, creatine, and possibly, glucose or fructose, glycerol or Gly and His or Arg, whereby RX increased the levels in the LF diets, with opposite effect in the HF diet. In conclusion, enzyme activities and fermentability were higly variable among different DF sources, and the effects were evident in the fibrous complete diets. The results of the in vitro studies supported the application of the methods to formulate fermentable insoluble fibre-rich, maize-soybean-mixed co-product diets. Correlation analyses suggested that DF fermentability, and solubility, swelling and water binding capacities explained significant proportions of the variances of the metabolic and physiological responses of the pigs to different feeds. Predictions based on the in vitro fermentability of DF and feed intake suggested that a strategy whereby pig diets are enriched in DF after the feedstuffs are screened on DF fermentability could substantially increase fermentation in the lower gut. Overall, the results suggested that productivity can be maintained in growing pigs fed diets containing up to twice the standard levels of DF, provided producers target co-product feeds that contain highly fermentable DF. The use of RX to improve nutrient digestion and to stimulate gut fermentation was not justified. / Environmental Sciences / Ph.D. (Environmental Sciences)

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2005. / The demand for protein for human and animal nutrition in South Africa is increasing and it will continuously increase. The effect of replacing soybean oilcake meal as protein source for broilers and full-fat soybean meal for weaner pigs, with different levels of sweet lupins (Lupinus angustifolius), canola oilcake and full-fat canola was examined. A basal diet with soybean oilcake as protein source was mixed with a diet using either sweet lupins or canola oilcake or full-fat canola in ratios of 100%, 67% and 33% respectively. In the broiler trial the test diets were fed for a period of six weeks with or without the enzyme Vegpro (Alltech). Pigs were fed the test diets, with and without Roxazyme® enzyme, ad libitum from 8.5 to 25 kg live weight. The fatty acid content of the fat pads of the broilers raised on the different diets was determined. The pigs were kept in the trial up to the grower- finisher phase. The fatty acid content of the carcass fat and muscle of pigs raised on the different diets was determined. The inclusion of enzymes had no effect on the growth, feed intake or feed conversion ratio of broilers fed the test diets. The provision of external dietary enzymes to the weaner pig diets failed to improve either dry matter intake or growth rate, but improved the feed conversion ratio. Broiler weights at six weeks of age were significantly higher for the control diet compared to the 20% lupin diet. There was no significant difference in the feed intake as the lupin content of the diets increased. The feed conversion ratio did not differ significantly between the control diet and the 6.6% lupin diet but became significantly poorer as the lupin content increased to 13.2% and 20% of the test diet. There were no significant differences in production performance of the control diet and the canola oilcake containing diet. The broiler weights at six weeks decreased significantly with each increase in the canola oilcake content of the diets. The feed intake of the 20% canola oilcake diet at week six was significantly less than the intake of the control diet, but not significantly less than the 6.6% and 13.2% canola oilcake diets. The feed conversion ratio of the control diet was significantly better than the 13.2% and 20% canola oilcake diets. No significant differences were found in week six between the 6.6% full-fat canola diet and the control diet for broiler weights and feed intake. The feed conversion ratio of the broilers fed the 13.2% and 20% full-fat canola diets was significantly poorer than the control diet. The final body weights of the weaner piglets fed the control diet were significantly higher than the final body weights of weaner piglets fed the lupin containing diets. The average daily gain of the weaner piglets fed the control diet was significantly higher than the gain of the weaner piglets fed the lupin containing diets. No significant differences in the feed intake and feed conversion ratio between the different lupin inclusion levels were detected. There were no significant differences in body weight, feed intake, average daily gain and the feed conversion ratio, between the various full-fat canola containing diets and the control diet. A significant difference in body weight was found between the weaner piglets fed the 20% canola oilcake diet and the weaner piglets fed the control diet. There were no significant differences in feed intake between the various inclusion levels of canola oilcake. The control and 6.6% canola oilcake containing diets had significantly higher average daily gains than the 20% canola oilcake containing diet. In the final trial the finisher pigs fed the test diet containing 25.00% lupins, had a final body weight significantly lighter than the final body weight of the finisher pigs fed the other test diets. The finisher pigs fed the test diet containing 25.00% lupins, also had a significantly reduced average daily gain and feed intake. The feed intake of the 25.00% canola oilcake diet was significantly lees than the feed intake of the 16.75% full-fat canola containing diet. The feed conversion ratio of the 25.00% lupin containing diet was significantly poorer than the feed conversion ratio of the 16.75% lupin containing diet, 8.25% lupin containing diet, 16.75% full-fat canola containing diet, 25.00% canola oilcake containing diet and the control diet. In a choice feeding trial growing pigs were offered four diets with four different protein sources: sweet lupins (25% inclusion level), canola oilcake (25% inclusion level), full-fat canola (25% inclusion level) and soybean oilcake (25% inclusion level), while their daily intakes were recorded. In a second choice feeding trial pigs were offered ten different diets with increasing levels (6.6%, 13.2%, 20%) of either sweet lupins, canola oilcake meal or full-fat canola meal. The pigs consumed significantly more of the soybean oilcake containing diet compared to diets containing the alternative protein sources. Pigs consumed significantly less of the full-fat canola diet compared to the sweet lupin and canola oilcake diets. Ten different canola cultivars were collected from two different locations in the Mediterranean rainfall area of South Africa namely the Western Cape (Swartland) and Southern Cape (Rûens) grain producing areas. The sinapine and glucosinolate content of various canola cultivars was compared and the influence of locality on the sinapine and glucosinolate content of the canola cultivars was determined. There were no significant differences (P < 0.05) in sinapine content when the canola produced in the Western and Southern Cape were compared. Varola 54 and Rainbow cultivars had significantly higher (P < 0.05) sinapine contents compared to the Varola 50 cultivar. Samples of lupins, field peas, faba beans and narbon beans were collected and analysed for amino acids, alkaloids, non-starch polysaccharides, tannin and starch. The digestible energy value of these alternative protein sources for pigs was determined. Significant differences were found in the amino acid content of the various crops. The alkaloid content of the lupins varied significantly between the sweet and bitter lupin varieties. Sweet L. angustifolius cultivars contained ca 50mg/kg and the bitter L. angustifolius cultivars ca 15000mg/kg alkaloids. The mean alkaloid content of L. albus cultivars was ca 1300mg/kg. The faba beans, narbon beans and peas had significantly higher values for tannins and starch, compared to lupins.

Two experiments were conducted for this thesis, to determine whether an animal should be fed to its genetic potential in spite of this not being achievable due to an on-farm constraint. The first experiment was designed to compare the response of pigs housed either individually or in groups to a range of feeds limiting in lysine between 40 and 85 kg live weight. Two hundred and eighty-eight entire male Large White x Landrace pigs were used. The experiment was divided into two growth periods, i.e. from 40 to 60 kg and from 60 to 85 kg. In each period, pigs were subjected to feed containing one of four dietary lysine concentrations. In Period 1, the lysine concentrations were 11.03 (L1); 9.54 (L2); 8.00 (L3) and 6.51 (L4) g/kg, while in Period 2 these were 7.82 (T1); 6.71 (T2); 5.55 (T3) and 4.40 (T4) g/kg. Pigs fed an L1, L2, L3 or L4 diet in Period 1 were fed a T1, T2, T3 and T4 diet in Period 2, respectively. Three buildings provided the following group sizes and floor-space allowances: House 1 contained eight pigs per pen at 1.94 m2/pig; House 2 contained four or eight pigs per pen at 1.72 or 0.86 m2/pig; and House 3 contained one pig per pen at 1.72 m2/pig. The individually-housed pigs were divided into three feeding levels, i.e. ad libitum, or pair-fed so that feed intakes would match those of ad libitum-fed pigs housed in groups of either 4 (restricted-4) or 8 (restricted-8) pigs per pen in House 2. For all group sizes, feed intake increased linearly as the dietary lysine content increased. However, this increase was significantly lower for 8, when compared with 1 and 4 pigs per pen. The linear increase in feed conversion efficiency with dietary lysine content was similar for all group sizes. However, at any dietary lysine concentration, pigs housed in groups of 8 had significantly higher efficiencies than the pigs housed individually or in groups of 4. Average daily gain increased linearly as lysine intake increased, this increase being the same for all group sizes. However, pigs in smaller groups grew significantly faster than those in larger group sizes for any lysine intake. Protein and lysine retention were unaffected by group size, increasing linearly as lysine intake increased. The efficiency of lysine utilisation (0.45) was not impaired by group size. The pair-fed pigs housed individually (restricted-4 and -8) consumed significantly less feed than the individually-housed pigs fed ad libitum, and this was reflected in their average daily gains, which increased linearly as lysine intake increased, but with the restricted-8 growing significantly slower than the ad libitum or restricted-4 pigs. In all three treatments feed conversion efficiency increased linearly with dietary lysine content, although the restricted-4 and -8 had significantly higher efficiencies than the ad libitum-fed pigs at any dietary lysine content. Protein and lysine retentions were unaffected by feeding level and increased significantly with lysine intake. However, at any lysine intake the restricted-8 pigs had a significantly lower efficiency of lysine utilisation than the ad libitum or restricted-4 pigs. The pigs with floor-space allowances of 0.86 and 1.94 m2/pig consumed significantly less and grew slower than the pigs with floor-space allowances of 1.72 m2/pig at any dietary lysine content. Feed conversion efficiency was unaffected by floor-space allowance and increased significantly with dietary lysine content. Similarly, protein and lysine retentions were unaffected by floor-space allowance and increased linearly as lysine intake increased. The efficiency of lysine utilisation (0.45) remained unaffected by floorspace allowance. It was concluded that when animals are socially stressed, feeding according to the requirement for maximum protein growth produces the best biological performance and carcass composition, with the corollary that, if profitability and biological efficiency is to be maximised, pigs housed in stressful conditions, or those whose future performance is predicted to be below potential because of external stressors, should not be given feed of an inferior quality. The second experiment was designed to determine the extent to which grouping or floorspace allowance would alter the nutrient content of feed chosen by pigs given a choice of two feeds differing in protein: energy ratio between 40 to 85 kg live weight. Three hundred and eighteen entire male Large White x Landrace pigs were used. Two buildings provided the following group sizes and floor-space allowances: House 1 contained nine and eighteen pigs per pen at 1.72 or 0.86 m2/pig; House 2 contained four, nine and fourteen pigs per pen at 1.72; 0.86 or 0.49 m2/pig. Animals were given simultaneous ad libitum access to a high (236 g protein/kg as fed) and a low crude protein feed (115 g protein/kg as fed) in two hardened plastic self-feeder bins placed side-by-side. A training period of six days was used prior to the start of the trial, during which the two feeds were alternated daily. The reduction in the proportion of high protein feed chosen over time was significantly higher for the groups of four and eight, in comparison to the groups of nine and eighteen, contrasting with the steady increase for the groups of fourteen pigs. Similarly, the significant increase for pigs with floor-space allowances of 0.49 m2/pig differed from the significant decrease for pigs with floor-space allowances of 0.86 and 1.72m2/pig. Pigs housed in larger group sizes and smaller floor-space allowances consumed significantly less and grew slower than pigs housed in smaller group sizes and larger floorspace allowances. However, the feed conversion efficiency remained unaffected by group size and floor-space allowance. The non-significant effect on protein retention with increasing group size contrasted with the significant increase associated with increasing floor-space allowance. The results of the two studies were compared to determine whether pigs chose differently depending on the degree of stress and the implication of this choice. Average daily gain was significantly reduced as the group size increased for pigs fed a fixed lysine content and choice-fed. However, this reduction was less severe with choice-feeding than when feeding a fixed lysine content. Increasing the group size significantly reduced the feed intake in pigs fed a fixed lysine content only. The efficiency of protein utilisation remained unaffected as the group size increased for the pigs fed a fixed lysine content. However, at any group size pigs fed lower lysine contents had higher efficiencies than pigs fed higher lysine contents. On the contrary, increasing the group size significantly increased the efficiency of protein utilisation in choice-fed pigs. The average daily gain and feed intake was significantly improved as the floor-space allowance increased but was similar for pigs fed a fixed lysine content and choice-fed. Although the efficiency of protein utilisation remained unaffected by increasing the floor-space allowance for the pigs fed a fixed lysine content and pair-fed, at any floor-space allowance pigs fed higher lysine contents had higher efficiencies than pigs fed lower lysine contents. The results indicate that providing socially stressed pigs a choice between an appropriate pair of feeds differing in protein: energy ratio, does not overcome the reduction in potential growth, but does result in performance similar to that of pigs fed a fixed lysine content. It was concluded that the social stress of grouping or floor-space allowance has no influence on the ability of the animal to select an appropriate dietary combination allowing the expression of potential growth within the constraint(s) of the production system. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.