Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2014-12-01T14:28:31Z No. of bitstreams: 2 Tese - Marcondes Dias de Freitas Neto - 2013.pdf: 1087626 bytes, checksum: 5d73742a83d30839bc40216d924038d3 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2014-12-04T14:01:25Z (GMT) No. of bitstreams: 2 Tese - Marcondes Dias de Freitas Neto - 2013.pdf: 1087626 bytes, checksum: 5d73742a83d30839bc40216d924038d3 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-12-04T14:01:25Z (GMT). No. of bitstreams: 2 Tese - Marcondes Dias de Freitas Neto - 2013.pdf: 1087626 bytes, checksum: 5d73742a83d30839bc40216d924038d3 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-12-10 / (Sem resumo em outra língua) / Objetivou-se, com este estudo, avaliar o desempenho e a eficiência alimentar em bovinos selecionados oriundos do programa de melhoramento genético Nelore Qualitas. Para isso, foi realizado um teste de eficiência alimentar em animais selecionado para ganho de peso pós desmama, utilizado o CAR como medida. Existem várias medidas de eficiência alimentar, a mais utilizada é a conversão alimentar (CA). A CA apresenta correlação com o peso adulto, com isso eleva o peso das matrizes o que não é desejável, pois, pode diminuir a eficiência econômica. Uma alternativa para seleção de animais mais eficientes é o consumo alimentar residual (CAR), que é calculado pela diferença entre o consumo esperado e o consumo observado. O consumo esperado é obtido pela regressão do consumo de matéria seca em função do peso corporal metabólico e o ganho em peso médio diário. Assim animais que apresentem CAR negativo (consumo observado menor que o consumo esperado) são considerados eficientes e animais com CAR positivo (consumo observado maior que o consumo esperado) ineficientes. Paralelamente, foi conduzido outro experimento para avaliar o desempenho em confinamento de animais que participaram da avaliação do programa de melhoramento genético, no entanto não receberam CEIP. Recentemente trabalhos nacionais foram publicados mostrando a diferença entre rebanhos selecionados e não selecionados quanto a desempenho e eficiência alimentar. A maioria dos trabalhos apresentaram melhor desempenho para os animais selecionados. No presente estudo foi observado que o CAR pode ser utilizado como medida de eficiência alimentar por apresentar grande variação entre os indivíduos avaliados. Além disso, os animais com maiores índices dentro do programa de melhoramento genético apresentaram melhor desempenho que os demais.

O objetivo deste estudo foi avaliar o fornecimento crônico de leptina recombinante ovina (oLeptina) e do nível de energia da dieta na idade, peso vivo (PV), escore de condição corporal (ECC) e composição corporal à puberdade, assim como avaliar seus efeitos no desenvolvimento dos folículos ovarianos e no consumo de matéria seca (CMS). Foram utilizadas 36 novilhas da raça Nelore, com média de 18 a 20 meses de idade, 276,1 ± 17,9 kg PV e ECC de 4,7 ± 0,46, distribuídas aleatoriamente em três tratamentos: A) Dieta de alta energia; B) Dieta de baixa energia, BL) Dieta de baixa energia com administração subcutânea de oLeptina. Os animais foram alojados de 2 baias coletivas de acordo com a dieta oferecida. As dietas foram formuladas para promover um ganho de peso médio diário (GMD) de 0,3 kg PV/dia e 1,0 kg PV/dia. O controle de consumo foi feito através da pesagem diária das sobras e manutenção dessas entre 5 e 10% do total oferecido. Os animais foram pesados e tiveram o ECC avaliado duas vezes por semana, para acompanhamento do GMD. Foi administrado 12 g de óxido de cromo/animal/dia por deglutição forçada por 10 dias, com coleta de amostras de fezes, dieta e sobras nos últimos 5 dias, para estimativa do consumo individual de MS e energia, através da determinação do cromo nas fezes e do FDNi nas fezes, dietas e sobras. O grupo BL recebeu 4,8 µg de oLeptina/kg PV, via subcutânea, duas vezes ao dia (6:00 e 18:00 horas) por 56 dias, enquanto os grupos A e B receberam 2 ml de solução salina. O diâmetro máximo do folículo dominante (FD) e a presença de corpo lúteo (CL) foram avaliados através de ultrassonografia transretal duas vezes por semana, até o momento da puberdade. No momento da ultrassonografia, foram coletadas amostras de sangue, por punção da veia jugular, para dosagem da concentração sérica de progesterona. A idade à puberdade foi considerada como a idade na primeira detecção de um CL, confirmado como sendo funcional por dosagem de progesterona acima de 1 ng/ml. Após a confirmação da puberdade os animais foram abatidos para estimativa da composição corporal, através da determinação do teor de água em cortes da 9a-10a-11a costelas. O maior teor de energia na dieta reduziu a idade e aumentou o ECC à puberdade (P<0,05). A leptina não teve efeito na idade, PV ou ECC à puberdade (P>0,05). Tanto o maior consumo de energia quanto a leptina aumentaram a velocidade de crescimento e determinaram maior diâmetro médio do FD (P<0,05), entretanto a velocidade de crescimento do FD do grupo BL voltou a diminuir, igualando-se à do grupo BL, após cerca de 30 dias de tratamento, comportando-se de forma quadrática à análise de regressão. O maior consumo de energia determinou maior teor de extrato etéreo e menores teores de proteína, matéria seca e matéria mineral no corpo vazio, além de maior espessura de gordura subcutânea e área de olho de lombo na carcaça (P<0,05). A aplicação de leptina não alterou a composição corporal das novilhas à puberdade (P>0,05). Não houve diferença no CMS (kg MS/dia) entre os grupos, entretanto o grupo A teve menor CMS em % PV, além de maior consumo de energia digestível, metabolizável e líquida para ganho (P<0,05). A leptina não reduziu o CMS das novilhas (P>0,05) tanto em kg MS/dia quanto em % PV. A energia acelera a obtenção da puberdade e altera a composição corporal à puberdade de novilhas zebuínas. A aplicação de leptina não acelerou a obtenção da puberdade de novilhas zebuínas em baixo consumo de energia, mas aumentou temporariamente a taxa de crescimento folicular desses animais. / This study was carried out to evaluate the effects of chronic administration of recombinant ovine leptin (oLeptin) and the energy level of the diet on age, body weight (BW), body condition score (BCS) and body composition at puberty, as well as to evaluate its effects on dominant follicle (DF) development and dry matter (DM) intake. Thirty six Nellore heifers, 18 to 20 months old, with 276.1 ± 17.9 kg BW and BCS of 4.7 ± 0.46 were randomly distributed into three treatments: H) High energy diet; L) Low energy diet; LL) Low energy diet with subcutaneous administration of oLeptin. Heifers were housed in two collective pens according to the diet offered. Diets were formulated to promote an average daily gain (ADG) of 0.3 kg BW/day and 1.0 kg BW/day. Intake was controlled daily by weighting the orts and keeping it between 5 and 10% of the total offered. Heifers were weighed and had their BCS was evaluated twice weekly, in order to control the ADG. Heifers received 12 g of chromic oxide/animal/day by forced swallowing for 10 days, while feces, diet and orts were sampled in the last 5 days, in order to estimate individual DM and energy intake, which was done by feces determination of chromic oxide, and diet and, feces and orts determination of iNDF. The LL group received 4.8 µg oLeptina/kg BW, subcutaneously, twice a day (at 06:00 and 18:00), for 56 days, while H and L groups received 2 ml of saline solution. Maximum DF diameter and presence of corpus luteum (CL) were evaluated twice weekly by transrectal ultrasound, until heifers achieved puberty. At the time of ultrasound evaluation, blood was sampled by jugular venipuncture for serum progesterone determination. Age at puberty was considered as age at first detection of a CL confirmed to be functional by serum progesterone above 1 ng/ml. After puberty confirmation heifers were slaughtered for body composition estimation, which was done by water determination on 9a-10a-11a rib cuts. High energy intake reduced age and enhanced BCS at puberty (P<0.05). Leptin administration did not affect age, BW or BCS at puberty (P>0.05). The high energy intake as well as leptin administration accelerated the DF growth and determined greater DF diameter (P<0.05), however the rate of growth on the LL group decreased after around 30 days of treatment equaling the rate of growth of the L group, and behaving in a quadratic manner at regression analysis. High energy intake enhanced ether extract and lowered protein and minerals proportion on empty body (P<0.05). It also enhanced carcass subcutaneous fat and the longissimus muscle area (P<0.05). Leptin administration did not alter the body composition of heifers at puberty (P>0.05). There was no difference on DM intake (kg DM/day) between groups, however the H group had higher DM intake in terms of % BW, as well as higher intake of digestible, metabolizable and net energy for gain (P<0.05). Leptin did not reduce DM intake neither in terms of kg BW/day nor % BW (P>0.05). Energy intake accelerates the onset of puberty and alters body composition at puberty of zebu heifers. Leptin administration did not accelerate puberty onset of zebu heifers receiving low energy diet, but temporarily enhanced the follicular growth rate of these animals.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Two experiments were carried out in the Sheep Division of the Universidade Federal de Santa Maria (UFSM), to determine energy and protein requirements of meat purpose wool lambs. Thirty 16 11 Texel 16 5 Ile de France crossbred intact male lambs, weaned at 42 days of age (16.2 ± 2.1 kg live weight (LW)) were used in trial 1 (comparative slaughter trial). After ten days of management and diet adaptation five lambs were randomly chosen and slaughtered (reference animals). Fifteen lambs were fed ad libitum and slaughtered at 25, 30 or 35 kg LW, and the remaining lambs were randomly assigned to 2 levels of DMI (either 70 or 55% of the ad libitum intake), being slaughtered together with lambs fed ad libitum and slaughtered at 35 kg LW. Total body N, fat and energy contents were determined. In the trial 2 (digestibility trial), six 16 11 Texel 16 5 Ile de France crossbred lambs (30.4 ± 2.6 kg LW) were housed in metabolic cages in a double 3 x 3 Latin Square Design. Nutritional value of the diet under the distinct feeding levels was evaluated. Decreased dry matter intake (DMI) resulted in linear increase of the digestibility and energy concentration of the diet (P<0.05). Body fleecefree protein content decreased with empty body weight (EBW) increasement. However, when protein in fleece was considered, total body protein was constant. Body fat content varied from 72.7 to 125.9 g/kg EBW, respectively for 13.1 and 28.2 kg EBW. Endogenous nitrogen loss was 243.2 mg/kg LW0.75/day, corresponding to a net protein requirement for maintenance of 1.52 g/kg LW0.75/day. Metabolizable protein requirement for maintenance was 2.31 g/kg LW0.75/day, and efficiency of protein use was 0.66. Net and metabolizable energy requirements for maintenance were 58.6 and 91.0 kcal/kg LW0.75/day, respectively. Consequently, estimated efficiency of energy use for maintenance (km) was 0.64. Net protein and energy requirements for weight gain of lambs at 15 and 35 kg LW, and daily LW gain of 250 g, were 32.5 and 33.1 g/day and 424 and 553 kcal/day, respectively. Efficiency of energy use for weight gain (kg) was 0.50, while efficiency of protein use for weight gain (knf) and wool growth (knw) were, respectively, 0.71 and 0.46. Growth pattern of the wool has a high influence on protein requirements of sheep. Texel x Ile de France crossbred growing lambs have lowest nutritional requirements than those recognized by most international Systems. / Com o objetivo de determinar as exigências energéticas e protéicas de cordeiros lanados de aptidão carne foram realizados dois experimentos nas dependências do Laboratório de Ovinocultura da Universidade Federal de Santa Maria (UFSM). No experimento 1 (abate comparativo), foram utilizados trinta cordeiros 16 11 Texel 16 5 Ile de France, machos nãocastrados, desmamados aos 42 dias de idade com peso vivo (PV) médio de 16,2 ± 2,1 kg. Transcorridos dez dias para adaptação dos animais às condições experimentais, cinco cordeiros foram aleatoriamente sorteados e abatidos. Dentre os remanescentes, quinze animais foram alimentados ad libitum e abatidos aos 25, 30 ou 35 kg de PV, sendo, os demais, submetidos a dois níveis de restrição alimentar (70 ou 55% do consumo ad libitum). O abate destes últimos foi realizado juntamente com aqueles alimentados ad libitum e abatidos aos 35 kg de PV. Foram determinados os conteúdos corporais de nitrogênio, gordura e energia. No experimento 2 (ensaio de digestibilidade), seis cordeiros 16 11 Texel 16 5 Ile de France (30,4 ± 2,6 kg) foram mantidos em gaiolas metabólicas individuais, sob delineamento duplo Quadrado Latino 3x3, com objetivo de avaliar o valor nutricional da dieta sob os distintos níveis de consumo. A redução do consumo de matéria seca resultou em aumento linear da digestibilidade e da concentração energética da dieta (P<0,05). A concentração de proteína no corpo livre de lã diminui com o aumento do peso de corpo vazio (PCV). Quando considerada a proteína retida na lã, contudo, a concentração protéica corporal foi pouco variável com o avanço da maturidade. A concentração de gordura corporal variou entre 72,7 e 125,9 g/kg PCV, respectivamente, para os PCV de 13,1 e 28,2 kg. A excreção endógena de nitrogênio foi de 243,2 mg/kg PV0,75/dia, e correspondeu a exigência de proteína líquida para mantença de 1,52 g/kg PV0,75/dia. Por sua vez, a exigência de proteína metabolizável para mantença foi de 2,31 g/kg PV0,75/dia, com eficiência de uso (knm) igual a 0,66. A exigência de energia líquida para mantença foi de 58,6 kcal/kg PV0,75/dia e a de energia metabolizável de 91,0 kcal/kg PV0,75/dia. A eficiência de utilização da energia metabolizável para mantença (km), por sua vez, foi de 0,64. As exigências de proteína e energia líquidas para ganho de peso de cordeiros com 15 e 35 kg de PV, e ganho médio diário de 250 g, foram de 32,5 e 33,1 g/dia e 424 e 553 kcal/dia, respectivamente. A eficiência de utilização da energia metabolizável para ganho de peso (kg) foi de 0,50, e da proteína metabolizável para ganho de peso (knf) e crescimento da lã (knw) de 0,71 e 0,46, respectivamente. O padrão de crescimento da lã possui grande influência sobre as exigências protéicas de ovinos. Cordeiros 16 11 Texel 16 5 Ile de France em crescimento possuem exigências nutricionais inferiores às reportadas por grande parte dos Sistemas internacionais.

Embora possua o maior rebanho comercial do mundo, o Brasil está longe de liderar pesquisas relacionadas ao melhoramento genético de bovinos de corte para eficiência alimentar. Alguns países investiram em estudos para seleção de animais eficientes e identificação de marcadores moleculares associados a esta característica. A seleção genética de animais eficientes representaria economia de alimentos, reduziria o impacto ambiental e aumentaria a rentabilidade da atividade. Obviamente é um desafio identificar animais mais eficientes em um rebanho de 205 milhões de cabeças, pois, além da mensuração ser cara, os resultados são obtidos a longo prazo. As associações entre eficiência alimentar e desempenho de bovinos de corte são conhecidas, porém avaliações envolvendo os impactos da seleção para eficiência sobre composição corporal e qualidade de carne de novilhos Nelore ainda são incipientes. O objetivo neste trabalho foi estudar relações entre eficiência alimentar, composição corporal, características de carcaça e qualidade da carne em bovinos Nelore confinados. Foram confinados, em dois anos, 322 novilhos para avaliação de características de carcaça e qualidade de carne. Deste total, 159 foram confinados em baias individuais, dos quais 92 foram avaliados quanto ao consumo alimentar residual (CAR). Foram calculadas a eficiência alimentar, eficiência parcial de crescimento, taxa relativa de crescimento, índice de Kleiber e CAR. No abate foram obtidos dados de rendimento, comprimento e profundidade de carcaça, área de olho de lombo, espessura de gordura subcutânea, peso do coração, fígado, rins e gordura interna. Foram obtidas variáveis de qualidade da carne de amostras não maturadas do Longissimus dorsi (pH, força de cisalhamento, cor da carne e gordura, perdas por cocção, capacidade de retenção de água e extrato etéreo). Foram analisados os coeficientes de regressão linear entre as variáveis avaliadas e o CAR. Animais mais eficientes apresentaram consumo no mínimo 12% menor que os ineficientes (P <0,05). A variação do CAR em 1 kg MS/dia melhorou a eficiência alimentar em 7% para o mesmo ganho de peso. Houve relação positiva entre CAR e espessura de gordura subcutânea (P <0,05). Características de carcaça, peso do coração e do fígado, gordura interna e parâmetros de qualidade da carne não foram relacionados com CAR (P>0,05). No entanto, a diminuição do CAR reduziu a deposição de gordura subcutânea, avaliada por ultrassom (P<0,05). Consistente com essa redução, o conteúdo de gordura intramuscular diminuiu (P = 0,08), indicando uma relação positiva entre CAR e deposição de gordura. A energia retida, estimada pela composição corporal, foi reduzida em 0,4 Mcal / dia. Isto significa que mudanças na composição corporal foram capazes de explicar 36% das diferenças no consumo de alimentos entre animais eficientes e ineficientes quanto ao CAR. A margem de contribuição (lucro) foi positivamente relacionada ao CAR (P<0,05), mas foi muito melhor correlacionada com a eficiência alimentar e ganho de peso. A associação de CAR com rentabilidade foi tão boa quanto medição de área de olho de lombo. O CAR está associado com a composição do ganho dos animais e pouco correlacionado com a lucratividade em confinamento. Animais eficientes quanto ao CAR apresentaram redução na deposição de gordura subcutânea. / Although Brazil has the largest commercial beef cattle herd of the world, research on genetic improvement of beef cattle for feed efficiency is incipient. Some countries have invested in studies to identify feed efficient animals and to find molecular markers associated with this characteristic. Genetic selection of efficient animals can resulting lower costs, reduced environmental impact and increased profitability. Obviously identifying the most efficient animals is a challenge in a herd of 205 million head as measurement of feed intake is expensive. Associations between feed efficiency and performance of beef cattle are known, but possible impacts of selection for efficiency on body composition and meat quality of Nellore are still unknown. The objective of this study was to investigate relationships of feed efficiency with corporal composition, carcass characteristics and meat quality in Nellore steers finished in the feedlot. To evaluate carcass characteristics and meat quality, 322 steers were fed over a two year period. Of this total, 159 were housed in individual pens and 92 were evaluated for feed consumption. Feed efficiency, residual feed intake (RFI) partial efficiency of growth, relative growth rate and Kleiber´s index were calculated. Variables evaluated were: dressing, yield carcass linear measurements, loin eye area, fat thickness and weights of heart, liver, kidneys and internal fat. Longissimus dorsi pH, shear force, color of meat and fat, cooking losses, holding water capacity and ether extract were collected. The linear regression coefficients between these variables and RFI were calculated. Efficient and inefficient animals were separated as those that had 1 unit difference in RFI. The efficient animals intake were 12% lower than the inefficient animals (P<0.05). The variation of RFI by 1 kg DM/day improved feed conversion efficiency by 7%. There was a positive relationship between RFI and subcutaneous fat thickness (P<0.05) as well as with fat thickness deposition (P<0.05). Carcass characteristics, heart and liver weight, internal fat and meat quality parameters were not related to RFI (P>0.05). Consistent with the reduction in subcutaneous fat deposition there was a decrease in the fat content (P=0.08), indicating a positive relationship between RFI and fat deposition. The retained energy, estimated by the difference in body composition, was reduced by 0.4 Mcal/day in inefficient vs efficient animals. This means that the change in estimated body composition was able to explain 36% of the difference in feed intake between RFI efficient and RFI inefficient animals. Individual profit was calculated and it was positively associated to RFI (P<0.05). However, profit had much greater association with feed conversion efficiency (r=0.75) as well as with weight gain (r=0.53). The association of RFI with profitability was low (0.23) and about as good as the measurement of loin eye area (r=0.20). In this work RFI was associated with leaner composition of weight gain and was not well correlated with profitability in the feedlot.

O objetivo deste estudo foi avaliar o fornecimento crônico de leptina recombinante ovina (oLeptina) e do nível de energia da dieta na idade, peso vivo (PV), escore de condição corporal (ECC) e composição corporal à puberdade, assim como avaliar seus efeitos no desenvolvimento dos folículos ovarianos e no consumo de matéria seca (CMS). Foram utilizadas 36 novilhas da raça Nelore, com média de 18 a 20 meses de idade, 276,1 ± 17,9 kg PV e ECC de 4,7 ± 0,46, distribuídas aleatoriamente em três tratamentos: A) Dieta de alta energia; B) Dieta de baixa energia, BL) Dieta de baixa energia com administração subcutânea de oLeptina. Os animais foram alojados de 2 baias coletivas de acordo com a dieta oferecida. As dietas foram formuladas para promover um ganho de peso médio diário (GMD) de 0,3 kg PV/dia e 1,0 kg PV/dia. O controle de consumo foi feito através da pesagem diária das sobras e manutenção dessas entre 5 e 10% do total oferecido. Os animais foram pesados e tiveram o ECC avaliado duas vezes por semana, para acompanhamento do GMD. Foi administrado 12 g de óxido de cromo/animal/dia por deglutição forçada por 10 dias, com coleta de amostras de fezes, dieta e sobras nos últimos 5 dias, para estimativa do consumo individual de MS e energia, através da determinação do cromo nas fezes e do FDNi nas fezes, dietas e sobras. O grupo BL recebeu 4,8 µg de oLeptina/kg PV, via subcutânea, duas vezes ao dia (6:00 e 18:00 horas) por 56 dias, enquanto os grupos A e B receberam 2 ml de solução salina. O diâmetro máximo do folículo dominante (FD) e a presença de corpo lúteo (CL) foram avaliados através de ultrassonografia transretal duas vezes por semana, até o momento da puberdade. No momento da ultrassonografia, foram coletadas amostras de sangue, por punção da veia jugular, para dosagem da concentração sérica de progesterona. A idade à puberdade foi considerada como a idade na primeira detecção de um CL, confirmado como sendo funcional por dosagem de progesterona acima de 1 ng/ml. Após a confirmação da puberdade os animais foram abatidos para estimativa da composição corporal, através da determinação do teor de água em cortes da 9a-10a-11a costelas. O maior teor de energia na dieta reduziu a idade e aumentou o ECC à puberdade (P<0,05). A leptina não teve efeito na idade, PV ou ECC à puberdade (P>0,05). Tanto o maior consumo de energia quanto a leptina aumentaram a velocidade de crescimento e determinaram maior diâmetro médio do FD (P<0,05), entretanto a velocidade de crescimento do FD do grupo BL voltou a diminuir, igualando-se à do grupo BL, após cerca de 30 dias de tratamento, comportando-se de forma quadrática à análise de regressão. O maior consumo de energia determinou maior teor de extrato etéreo e menores teores de proteína, matéria seca e matéria mineral no corpo vazio, além de maior espessura de gordura subcutânea e área de olho de lombo na carcaça (P<0,05). A aplicação de leptina não alterou a composição corporal das novilhas à puberdade (P>0,05). Não houve diferença no CMS (kg MS/dia) entre os grupos, entretanto o grupo A teve menor CMS em % PV, além de maior consumo de energia digestível, metabolizável e líquida para ganho (P<0,05). A leptina não reduziu o CMS das novilhas (P>0,05) tanto em kg MS/dia quanto em % PV. A energia acelera a obtenção da puberdade e altera a composição corporal à puberdade de novilhas zebuínas. A aplicação de leptina não acelerou a obtenção da puberdade de novilhas zebuínas em baixo consumo de energia, mas aumentou temporariamente a taxa de crescimento folicular desses animais. / This study was carried out to evaluate the effects of chronic administration of recombinant ovine leptin (oLeptin) and the energy level of the diet on age, body weight (BW), body condition score (BCS) and body composition at puberty, as well as to evaluate its effects on dominant follicle (DF) development and dry matter (DM) intake. Thirty six Nellore heifers, 18 to 20 months old, with 276.1 ± 17.9 kg BW and BCS of 4.7 ± 0.46 were randomly distributed into three treatments: H) High energy diet; L) Low energy diet; LL) Low energy diet with subcutaneous administration of oLeptin. Heifers were housed in two collective pens according to the diet offered. Diets were formulated to promote an average daily gain (ADG) of 0.3 kg BW/day and 1.0 kg BW/day. Intake was controlled daily by weighting the orts and keeping it between 5 and 10% of the total offered. Heifers were weighed and had their BCS was evaluated twice weekly, in order to control the ADG. Heifers received 12 g of chromic oxide/animal/day by forced swallowing for 10 days, while feces, diet and orts were sampled in the last 5 days, in order to estimate individual DM and energy intake, which was done by feces determination of chromic oxide, and diet and, feces and orts determination of iNDF. The LL group received 4.8 µg oLeptina/kg BW, subcutaneously, twice a day (at 06:00 and 18:00), for 56 days, while H and L groups received 2 ml of saline solution. Maximum DF diameter and presence of corpus luteum (CL) were evaluated twice weekly by transrectal ultrasound, until heifers achieved puberty. At the time of ultrasound evaluation, blood was sampled by jugular venipuncture for serum progesterone determination. Age at puberty was considered as age at first detection of a CL confirmed to be functional by serum progesterone above 1 ng/ml. After puberty confirmation heifers were slaughtered for body composition estimation, which was done by water determination on 9a-10a-11a rib cuts. High energy intake reduced age and enhanced BCS at puberty (P<0.05). Leptin administration did not affect age, BW or BCS at puberty (P>0.05). The high energy intake as well as leptin administration accelerated the DF growth and determined greater DF diameter (P<0.05), however the rate of growth on the LL group decreased after around 30 days of treatment equaling the rate of growth of the L group, and behaving in a quadratic manner at regression analysis. High energy intake enhanced ether extract and lowered protein and minerals proportion on empty body (P<0.05). It also enhanced carcass subcutaneous fat and the longissimus muscle area (P<0.05). Leptin administration did not alter the body composition of heifers at puberty (P>0.05). There was no difference on DM intake (kg DM/day) between groups, however the H group had higher DM intake in terms of % BW, as well as higher intake of digestible, metabolizable and net energy for gain (P<0.05). Leptin did not reduce DM intake neither in terms of kg BW/day nor % BW (P>0.05). Energy intake accelerates the onset of puberty and alters body composition at puberty of zebu heifers. Leptin administration did not accelerate puberty onset of zebu heifers receiving low energy diet, but temporarily enhanced the follicular growth rate of these animals.

Thesis (BSc. Agriculture (Animal Production)) -- University of Limpopo, 2019 / An experiment was conducted to determine the effect of bovine colostrum feeding period after hatching on performance and carcass characteristics of male Ross 308 broiler chickens. The experiment was based on 0, 12, 24, 36, 48 and 72 hours of liquid bovine colostrum feeding after hatching of broiler chickens. The experiment commenced with 180 male Ross 308 broiler chicks with an initial live weight of 42 ± 2g per bird and was carried out for six weeks. The chicks were randomly assigned to six treatments with three replications, resulting in 18-floor pens with 10 chicks per replicate. A complete randomized design was used in this experiment. Data was analysed using the General Linear Model (GLM) procedures of the Statistical Analysis of system, Version 9.3.1 software program. Where there were significant differences, mean separation was done using the Turkey test at the 5% level of significance. A quadratic regression model was used to determine the optimum productivity of the experiment while a linear model was used to determine the relationships between bovine colostrum feeding period and responses in the variables measured. Feed intake during Week 1, growth rate during Week 3 and feed conversion ratio (FCR) during Weeks 2 and 3 of the growing period of male Ross 308 broiler chickens were not affected (p>0.05) by bovine colostrum feeding periods after hatching. Similarly, bovine colostrum feeding had no effect (p>0.05) on diet dry matter (DM), neutral detergent fibre (NDF), acid detergent fibre (ADF) and ash digestibilities in male Ross 308 broiler chickens aged 14 to 21 days. Bovine colostrum feeding period after hatching had no effect (p>0.05) on nitrogen retention (N-retention) in male broiler chickens aged one to 21 days. Similarly, gut organ digesta pH, length and weight of male Ross 308 broiler chickens aged 21 days were not improved (p>0.05) by bovine colostrum feeding after hatching. However, bovine colostrum feeding improved (p<0.05) feed intake during Weeks 2 and 3 of the growing period of male Ross 308 broiler chickens. Similarly, bovine colostrum feeding after hatching improved (p<0.05) crude protein (CP) digestibility in male broiler chickens aged 14 to 21 days. Metabolisable energy (ME) intake of male Ross 308 broiler chickens aged one to 21 days was improved (p<0.05) by bovine colostrum feeding period after hatching. Similarly, growth rate of male broiler v chickens during Weeks 1 and 2 was improved (p<0.05) by colostrum feeding after hatching. Feed conversion ratio of male broiler chickens during Week 1 was improved (p<0.05) by bovine colostrum feeding period after hatching. Bovine colostrum feeding after hatching improved (p<0.05) live weight of male Ross 308 broiler chickens at the ages of 7, 14 and 21 days. Nitrogen retention and FCR of male Ross 308 broiler chickens aged 22 to 42 days were not affected (p>0.05) by bovine colostrum feeding after hatching. In addition, live weights of male Ross 308 broiler chickens aged 35 and 42 days were not affected (p>0.05) by bovine colostrum feeding period after hatching. Similarly, bovine colostrum feeding had no effect (p>0.05) on gut organ digesta pH, large intestine lengths, breast and drumstick weights and breast meat juiciness of male Ross 308 broiler chickens aged 42 days. However, bovine colostrum feeding improved (p<0.05) feed intake and growth rate of male Ross 308 broiler chickens aged 22 to 42 days. Live weights of male Ross 308 broiler chickens aged 28 days were improved (p<0.05) by bovine colostrum feeding period after hatching. Similarly, bovine colostrum feeding after hatching did not affect (p<0.05) diet DM, CP, NDF, ADF and ash digestibilities in male Ross 308 broiler chickens aged 35 to 42 days. Metabolisable energy intake of male broiler chickens aged 22 to 42 days was improved (p<0.05) by bovine colostrum feeding period after hatching. Similarly, GIT, small intestine and caecum lengths and crop, proventriculus, gizzard, small intestine, caecum, large intestine, carcass and thigh weights of male Ross 308 broiler chickens aged 42 days were improved (p<0.05) by bovine colostrum feeding after hatching. Bovine colostrum feeding after hatching improved (p<0.05) breast meat tenderness, flavour and shear force of male Ross 308 broiler chickens aged 42 days. It is concluded that reasons for differing responses to bovine colostrum feeding periods of up to 72 hours after hatching are not clear. Therefore, further studies in which longer bovine colostrum feeding periods are used after hatching are recommended. / National Research Foundation (NRF)

Thesis (M.Sc. (Animal Production)) --University of Limpopo, 2019 / Two experiments were conducted to determine the effect of dietary threonine level on production performance and carcass characteristics of Ross 308 broiler chickens. In each experiment the diets were isocaloric and isonitrogenous but with different dietary threonine levels.The first part of the study determined the effect of dietary threonine level on feed intake, growth rate, mortality and carcass characteristics of Ross 308 broiler chickens aged between Day 1-21. A total of 150 unsexed day-old chicks were used in a complete randomized design having 5 treatments (6.4, 7.5, 8, 8.5 and 9g of threonine/kg DM feed), replicated three times and having ten chickens per replicate. The second part of the study determined the effect of dietary threonine level on feed intake, digestibility, growth rate, mortality and carcass characteristics of male Ross 308 broiler chickens aged between Day 22-42. Seventy-five male chickens were used in a complete randomized design having 5 treatments (6.4, 7.5, 8, 8.5 and 9g of threonine/kg DM feed), replicated three times and having five chickens per replicate. A quadratic regression model was used to determine the optimal productivity of the chickens while a General Linear Model (GLM) procedures for the statistical analysis of variance was used to detect dietary treatment effects. Where there were significant differences (P<0.05), Turkey’s honestly significant difference test (HSD) was used for mean separation. The chickens were slaughtered at the ages of 21 and 42 days for Experiments 1 and 2, respectively, following ethical standards as recommended by the University of Limpopo Animal Research Ethics Committee (AREC/12/2017: PG). Two chickens per replicate for both studies were slaughtered for the determination of carcass characteristics (carcass and organ weights, gut organ digesta pH and gastro-intestinal length measurements). Dietary threonine levels used in this experiment affected (P<0.05) feed intake, growth rate, live weight, metabolisable energy (ME) intake, nitrogen retention, feed conversion ratio and gut organ weights and lengths of unsexed Ross 308 broiler chickens aged 21 days. Dietary threonine level did not affect (P>0.05) diet digestibility. Feed conversion ratio, pH of the proventriculus digesta, gut intestine length and caecum length of unsexed broiler chickens were optimized at different dietary threonine levels of 9.6, 8.5, 6.6 and 8.4 g/kg DM, respectively. Dietary threonine levels had an effect (P<0.05) on feed intake, diet digestibility, metabolizable energy, live weight, proventriculus pH values, GIT length, gut organ and carcass organ weights of male Ross 308 broiler chickens between 22 to 42 days of age. Proventriculus and large intestine weights were optimized at different dietary threonine levels of 7.5 and 9.1 g/kg DM feed, respectively. Dietary threonine level did not affect (P>0.05) growth rate, feed conversion ratio of male Ross 308 broiler chickens between 22 to 42 days of age. It is concluded that dietary threonine levels used in this study affected production performance of younger broilers (Day 1-21) more than that of older birds (Day 22-42). However, production variables were optimized at different dietary threonine levels. This has implication on diet formulation for the chickens and no linear response could be established / National Research Foundation (NRF), and the Department of Agriculture, Forestry and Fisheries (DAFF)

(M.Sc. (Animal Production)) -- University of Limpopo, 2014 / Two experiments were conducted to determine the effect of dietary threonine level on productivity and carcass characteristics of indigenous Venda chickens. In each experiment the diets were isocaloric and isonitrogenous but with different dietary threonine levels. A complete randomized design was used in both experiments, the starter (1-7 weeks old unsexed chickens) and finisher (8-13 weeks old female chickens) experiments. The treatments were CT4 (4 g of threonine/kg DM), CT5 (5 g of threonine/kg DM), CT6 (6 g of threonine/kg DM), CT7 (7 g of threonine/kg DM) and CT8 (8 g of threonine/kg DM). A quadratic type of equation was used to determine dietary threonine levels for optimal feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy intake and nitrogen retention of unsexed Venda chickens aged one to seven weeks. Dietary threonine level affected (P<0.05) feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy and nitrogen retention. However, feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy and nitrogen retention of indigenous Venda chickens were optimized at different dietary threonine levels of 6.218, 6.437, 6.331, 6.655, 5.979 and 6.158 g/kg DM feed, respectively. Dietary threonine level did not affect (P>0.05) mortality rate of the chickens. The treatments for the second experiment were FT4 (4 g of threonine/kg DM), FT5 (5 g of threonine/kg DM), FT6 (6 g of threonine/kg DM), FT7 (7 g of threonine/kg DM) and FT8 (8 g of threonine/kg DM). Dietary threonine level had effect (P<0.05) on feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy and nitrogen retention of female Venda chickens aged eight to 13 weeks. Feed intake, growth rate, feed conversion ratio, live weight, metabolisable energy intake and nitrogen retention of chickens were optimized at dietary threonine levels of 6.054, 6.142, 6.442, 6.201, 5.72 and 6.088 g/kg DM, respectively. However, dietary threonine level had no effect (P>0.05) on pH values of crop, proventriculus, gizzard, small intestine, large intestine and caecum of female Venda chickens aged 91 days. Carcass weights of female Venda chickens were affected (P<0.05) by dietary threonine level. Carcass, breast, drumstick, thigh, gizzard and liver weights of female Venda chickens aged 91 days were optimized at dietary threonine levels of 6.183, 6.201, 5.712, 5.847, 4.820 and 6.180 g/kg DM, respectively. Dietary threonine level v had effect (P<0.05) on crude protein and threonine contents of female Venda chicken meat. Meat crude protein and threonine contents of female Venda chickens aged 91 days were optimized at dietary threonine levels of 5.9 and 5.7 g/kg DM, respectively. Dietary threonine level had no effect (P>0.05) on meat flavour, tenderness and juiciness of female Venda chickens. However, meat flavour, tenderness and juiciness of female Venda chickens aged 91 days were optimized at dietary threonine levels of 5.977, 6.103 and 5.977 g/kg DM, respectively. No chicken deaths were observed. / National Research Foundation (NRF)

Photoperiod manipulations are widely used throughout the Atlantic salmon (Salmo salar) farming industry as a means of producing a product of uniform quality all-year round. However, farmers still remain sceptical over their effectiveness to regulate growth and maturation during the on-growing stage. Furthermore, reports of a characteristic growth-dip following light exposure suggest that light may negatively affect the physiological performance of fish in the short-term. Thus, this thesis investigates the effects of light characteristics (spectral quality, intensity and photoperiod) on growth and maturation of salmonid fish and addresses some of the uncertainties surrounding photoperiod use currently reported within the industry. Rainbow trout (Oncorhynchus mykiss) are seemingly an ideal model species for examining photoperiod effects on growth. Consequently, the application of constant light exposure (LL) at two different intensities (28W and 16W) during two different thermal conditions (summer and winter) was examined on individually tagged fish. Feed intake and growth appeared to be related to the ambient water temperature and did not appear to be affected by intensity or photoperiod, although the onset of constant light did appear to initially affect growth rate. This may indicate that LL has a limiting effect on the growth of trout or that the prevailing water temperature at which light is applied may override the photoperiodic effect. Furthermore, the lack of enhanced growth in trout exposed to LL, unlike that demonstrated for other salmonids, suggest that there may be a species-specific response to environmental variables. Thus, questions regarding photoperiod effects should be limited to the species in question. The main source of variation in results observed under photoperiod manipulations stems from the salmon industry. Atlantic salmon post-smolts were reared in seawater tanks and either maintained under a natural photoperiod (NP) or exposed to a simulated natural photoperiod (SNP), constant light superimposed on the natural light (NPLL) or constant light only (LL). Artificial light onset, irrespective of photoperiod, resulted in an apparent trend for a reduced appetite lasting up to 60 days. Furthermore, the onset of constant light resulted in a significant chronic elevation of plasma cortisol levels and changes to growth and thyroid hormone levels, providing direct evidence that constant light exposure induces stress. In addition, fish exposed to SNP failed to exhibit a stress response despite a low feed intake. However, differences in the plasma melatonin levels during twilight times, as compared to NP, suggest that gradual changes in the natural light intensity throughout the day, particularly around dawn and dusk, may be important for synchronizing daily events. No differences in growth were observed between the NP and NPLL regimes, although fish reared in an enclosed regime (SNP and LL) exhibited a significantly lower weight gain than fish in an open environment (NP and NPLL). This further highlights the impact that the rearing environment has on the growth performances of fish and the need for commercially run trials. Advances in lighting technologies and a greater understanding of how light is transformed through the water column have focussed research on the spectral sensitivity of fish. Therefore the lighting efficiency of novel blue narrow bandwidth LED lighting units through the water column and their effects on growth and maturation performances of salmon reared in commercial production cages were compared against the standard metal halide units currently utilized throughout the industry. LL application, irrespective of intensity or spectrum, reduced the numbers of fish maturing as compared to fish reared under a natural photoperiod. However, this was greatest under the standard metal halide units reflecting a greater light penetration and perception as determined by plasma melatonin levels. The metal halide groups exhibited the greatest relative weight gain over the trial period as compared to control fish. No evidence was observed for a growth-dip under metal halide light, although blue lit treatments exhibited an initial significant reduction in food consumption, suggesting a possible welfare issue. Nevertheless, the prototype blue LED units showed possible potential for commercial application by penetrating the water depth at half the distance of the metal halide units for only one eighth the power and one fifth the brightness. However, further tests of these prototype spectral units are required to examine the potential welfare and physiological growth and reproductive effects. These studies have shown that the efficacy of artificial light regimes is largely dependent upon the effectiveness of the light source through the underwater environment and its perception by fish, providing a sufficient intensity is emitted exceeding the physiological threshold level for the species cultured. Moreover, whilst the onset of artificial light may elicit a stress response and demonstrate a trend for a suppression of appetite for salmon reared in experimental tanks, no compelling evidence for a suppression of appetite or growth was found under normal commercial cage conditions. This suggests that the growth-dip observed within the industry may in part be a combination of a physiological response to the onset of light further exaggerated by the farmer’s perception and altered judgement in feeding. In addition, the results obtained from this study have helped to standardize the use of light regimes within the industry. Nevertheless, further studies are necessary to fully elucidate the underlying mechanisms which may govern growth and maturation in fish following the onset of light exposure.

O consumo alimentar residual (CAR) é uma medida de eficiência alimentar independente da taxa de crescimento e do peso adulto. Pouco se sabe sobre associações entre o CAR e as características de produtividade dos animais selecionados para este parâmetro, bem como os mecanismos relacionados ao aumento na eficiência alimentar dos animais selecionados para o CAR. O objetivo deste estudo foi avaliar as associações entre CAR, desempenho, crescimento dos componentes da carcaça e digestão do amido em bovinos Nelore, em confinamento, e avaliar a utilização dos parâmetros fecais, (porcentagem de amido, proteína, matéria seca e pH), como indicadores da digestão do amido. Noventa e seis touros da raça Nelore selecionados como elite ou superior na prova de ganho de peso a pasto e classificados quanto ao seu temperamento, medido pela distância mínima de aproximação, foram confinados e alimentado ad libitum (68% NDT, 13,5% PB, 28,1% amido) durante 68 dias com peso vivo médio inicial de 408±33 e idade de 645±52 dias. A ingestão de matéria seca (IMS) e o ganho médio diário (GMD) foram medidos individualmente. As pesagens e as mensurações da espessura de gordura subcutânea (EGS), espessura de gordura na picanha (EGP) e a área de olho de lombo (AOL) foram realizadas a cada 21 dias. Os animais foram classificados como sendo de alto CAR (DP>0,5), baixo CAR (DP<0,5) e intermediário. O amido das amostras da ração e da sobra coletadas durante sete dias consecutivos, no final do experimento, foi determinado por análise laboratorial e a quantificação do amido fecal foi feita através do NIRS e a digestão do amido estimada. Durante o confinamento, novilhos com baixo CAR tiveram menores IMS e conversão alimentar que novilhos com alto CAR, mas nenhuma diferença foi observada no GMD, no PV final, AOL, EGP, EGS, temperamento e ganho de peso durante a prova de ganho de peso. Animais mais eficientes também não diferiram dos demais quanto à digestão do amido, no entanto, animais mais eficientes tiveram menores quantidades de proteína fecal. O CAR foi positivamente correlacionado com a IMS, consumo de amido, proteína fecal e eficiência alimentar e negativamente correlacionado com a conversão alimentar, no entanto não houve correlação entre o CAR e o GMD na prova de ganho de peso a pasto e temperamento. A digestão do amido foi positivamente associada com a PB fecal e negativamente correlacionada com a MS e o amido fecal. Não houve associação entre o CAR, o GMD a pasto e o temperamento, talvez porque são filhos de vacas selecionadas para essas características e também foram os que tiveram os melhores desempenhos na prova a pasto. / Residual feed intake (RIF) is a trait of efficiency independent of growth rate and mature weight. Little is known about the association between RFI and productivity and the mechanisms associate on improve efficiency in RFI. This work aimed to study the association between RFI, performance, growth of carcass traits and starch digestion in Nellore bulls and to investigate the utilization of fecal parameters like crude protein, dry matter and pH, as indicators of starch digestion. Ninety six Nellore bulls, with 645±52 days, 408±33kg initial body weight, previously selected as elite or superior in performance test on pasture and classified according to their temperament, were fed a finishing ration (68% TDN, 13,5%CP and 28,1% starch) on an ad libitum basis, for 68 days. Daily dry matter intake (DMI) and body weight gain (BWG) were measured individually. All animals were weighed and had ultrasonic measurements of Longissimus muscle area (REA) and backfat thickness (BF) on the 12th and 13th ribs obtained every 21 days. RFI was calculated as the difference between actual DMI and predicted DMI for a common mid-test BW0.75 and daily BWG and the animals were classified as high (SD>0,5), low (SD<0,5) and intermediary RFI. The starch of the diet and orts was determinate by laboratory analyses and the fecal starch was determinate with NIRS, and the starch digestion estimated. Low RFI bulls had low DMI and feed:gain than high RFI bulls, but no difference were observe in daily BWG, final BW, REA, BF, temperament and daily gain in the pasture performance test. More efficient bulls had no difference in starch digestion, however low RFI bulls had lower crude protein in the feces. RFI was positively correlated with DMI, starch intake and feed efficiency, but RFI was not correlated with daily BWG in the pasture performance test and temperament. Starch digestion was positively associated with Fecal CP and negatively associated with DM and starch. There was no association between RFI and daily BWG on pasture and temperament, perhaps because these animals belonged to a herd that was selected for these characteristics and also were the animals that had the best performance on pasture test.