Two meta-analysis of effects of yeast culture and monensin in lactating dairy cows were first performed. Secondly, two experiments were performed to evaluate the effects of live yeast (LY) or monensin (M) or both (LY+M) on gas production and fermentation by rumen micro-organisms in vitro in low (40 %) and high (60 %) concentrate diets of dairy cows. Rumen contents were collected from one cannulated lactating Holstein cow. Gas production was measured from 0 to 48 h of incubation. Volatile fatty acids and ammonia nitrogen concentrations were measured after 48 h. Meta-analysis of monensin indicated decrease dry matter intake (DMI) and increasing milk yield, consequently improving feed efficiency. Meta-analysis of yeast culture did not show improved performance. These results highlighted the importance of the meta-analysis as a useful tool that can be employed to both summarize effects across studies and to investigate factors explaining potential heterogeneity of response. The batch fermentation showed that in high concentrate diet, M significantly increased ammonia nitrogen, decreased acetate, but tended to increase propionate concentration (7.9, 63.2, 18.6 vs. 6.3, 66.8, 14.2 mmol/l; respectively). Addition of LY increased acetate concentration (64.2 vs 66.8 mmol/l). Supplementation with M, LY and LY+M reduced total gas production by 37.1, 22.5 and 26.9 %, respectively, compared to control at 48 h. In low concentrate diet, M and LY+M decreased and increased acetate (60.1 and 69.7 vs. 7.1 mmol/l; respectively). Adding LY and LY+M produced 8.6 % less gas, and M treatment 3.4 % more gas than the control. Overall, at 48 h, high concentrate resulted in less gas than low concentrate diets. High concentrate diets showed increased ammonia (7.9 and 6.4 vs. 5.21 and 4.7 mmol/l) decreased acetate (63.0 and 63.2 vs. 67.0 and 69.7 mmol/l) with a tendency to increased propionate (18.6 and 18.9 vs. 14.6 and 14.1 mmol/l) compared to low concentrate in M and LY+M treated diets. These results indicate that the effects of M and LY on rumen fermentation are substrate dependent, the high-concentrate diet showing the greatest response / Agriculture / M. Sc. (Agriculture)

Manure production and nutrient management in pasture-based dairy production systems by Walter Svinurai The effect of dietary treatments on nutrient excretion was determined and an attempt to improving the retention of excreted nitrogen in stored manure using Aloe ferox leaf gel (AFLG) and pine bark was conducted at a pasture-based dairy farm. The animal mass-balance method was used to determine nutrient excretion by cows fed on three dietary treatments, Lolium perrene-based treatment (LP), Lolium multiforium-based treatment (LM) and Lolium perenne- Trifolium repens -based treatment (LTF). In separate experiments, slurry from dairy cows fed LM was amended with AFLG and pine bark at concentrations of 25, 50, 75 and 100 g/l and stored under anaerobic conditions for 16 days. The highest and lowest excretions of N, P and K were observed in LM and LP treatments, respectively. Increasing dietary N improved K and N retention in milk and, consequently increased milk urea nitrogen (MUN) and N excretion (P < 0.05). The concentrations of AFLG affected N and P retention in manure (P < 0.05). The highest retention in total Kjeldahl nitrogen (TKN) of the initial was 42% AFLG at 25g/l inclusion rate. Ammonium nitrogen (AMN) concentration increased significantly due to the interactive effect of AFLG inclusion rate and time. Pine bark powder significantly improved N and P retention in manure at all concentrations. The retention in TKN was higher (P < 0.05) at 25g/l pine bark powder than other concentrations. The interaction effect of inclusion rate and time increased iii AMN (P < 0.05). Dietary treatments significantly affected nutrient excretion, and AFLG and pine bark considerably improved N retention in stored slurry. Findings from the filed trial suggest the need for more attention on managing dietary nutrients in the post-rainy and cool-dry season when growth of pasture influenced choice of dietary treatments that led to high nutrient excretion. Field simulation of the additives to determine their efficacy and environmental hazards was recommended.

Degradation kinetics of carbohydrate fraction of commercial concentrate feeds for weaned calves, heifers, lactating and dry dairy cattle / Variations in composition and disappearance of nutrients in dairy cattle feeds are dictated by ingredients, methods of processing, storage while milk production levels depend on the animal, environmental factors and largely on pools of available carbohydrates, proteins, vitamins and minerals in the concentrate feeds. There is a wide variety of concentrates for dairy cattle on the formal and informal markets and dairy farmers need to be astute in selecting feeds appropriate for specific production periods and animals to sustain their businesses. Composition of nutrients displayed on concentrate containers is however inadequate for in-depth assessment of products. This study determined nutrient composition, rumen dry matter disappearance and microbial colonization on residual substrate on commercial concentrate feeds and simulated total mixed rations for dairy calves, heifers, lactating and dry cows based on common feeding guidelines. Equivalent feeds for each herd group were obtained from three suppliers in the formal markets in Gauteng province of South Africa, making a total of twelve. An analysis of the data on container labels for the herd groups displayed similar feed values, as also reflected on the recommendation Tables of Act 36: Feeds and Fertilizer bill 1947 of South Africa. / Agriculture, Animal Health and Human Ecology / M.Sc. (Agriculture)

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The effect of Acid Buf and combinations of Acid Buf and Sodium bicarbonate in dairy cow diets on production response and rumen parameters The objective of this study was to determine the effect of Acid Buf alone, or in combination with sodium bicarbonate, on milk production, milk composition and selected rumen parameters. A high concentrate TMR, formulated to be potentially acidotic, was used to construct four dietary treatments in which Acid Buf (AB), the skeletal remains of the seaweed Lithothamnium calcareum, was used alone or in combination with sodium bicarbonate (BC). The diets contained 3.5 g/kg of AB (Treatment 1) or 1.75 g/kg of AB and 1.75 g/kg of BC (Treatment 2) or 3.5 g/kg of AB and 3.5 g/kg of BC (Treatment 3) or 3.5 g/kg of AB and 5.2 g/kg of BC (Treatment 4). The response to treatment was determined using eight ruminally cannulated lactating Holstein cows randomly allocated to treatments according to a 4 x 4 (n=2) Latin square design, with four treatments and four periods. The total experimental period was 100 days in which every cow received each diet for a period of 18 days prior to a data collection period of 7 days. Rumen pH was monitored continuously over 2 days using a portable data logging system and in-dwelling electrodes. Samples of rumen fluid were collected for volatile fatty acid (VFA) analyses. During each data collection period, milk production was recorded twice daily for 7 days, whereas milk was sampled twice daily for five consecutive days for component analysis. Cows were fed ad libitum and dry matter intake was recorded individually. Treatment had no significant effect on milk production, milk composition or feed intake. Ruminal pH profiles of all the treatments indicated that the diets were well buffered. Average pH over 24 hours was 6.0, 6.1, 6.1 and 6.2 for Treatments 1, 2, 3 and 4, respectively. The pH did not go below 5.8 for any of the treatments and increasing levels of sodium bicarbonate increased the diurnal profile such that at the highest level (Treatment 4), the pH profile ranged from 6.1 to 6.5. Although not significant, Treatment 1 (Acid Buf alone) numerically resulted in the highest milk output without compromising milk quality. It is proposed that high rumen pH may impact negatively on milk output by increasing the acetate:propionate ratio to the detriment of rumen efficiency. Treatment had no significant effect on total VFA concentration, but there seemed to be a tendency for increased total VFA concentration as the level of sodium bicarbonate increased. The acetate:propionate ratio of Treatment 1 (2.91) was significantly lower than Treatment 4 (3.65) (P<0.05). The use of buffers which react to increasing acidity in the rumen may therefore provide an efficient, safe solution to rumen acidosis. This study confirmed previous results indicating that a daily intake of 80 g of Acid Buf by cows receiving high concentrate diets would support high milk production without compromising milk solids contents. / AFRIKAANSE OPSOMMING: Die effek van Acid Buf en kombinasies van Acid Buf en Natriumbikarbonaat in melkkoeidiëte op melkproduksie, melksamestelling en rumenparameters Die doel van die studie was om die invloed van Acid Buf alleen, of in kombinasie met natriumbikarbonaat, in melkbeesdiëte op melkproduksie en melksamestelling, asook op bepaalde rumenparameters, te bepaal. ‘n Volledige dieet met ‘n hoë kragvoerinhoud, wat geformuleer is om potensieel asidoties te wees, is gebruik om vier dieetbehandelings saam te stel waarin Acid Buf (AB), die skeletoorblyfsels van die seegras Lithothamnium calcareum, alleen of in kombinasie met natriumbikarbonaat (BK) gebruik is. Een basale diet is dus geformuleer en die behandelingsdiëte het onderskeidelik 3.5 g/kg AB (Behandeling 1) of 1.75 g/kg AB en 1.75 g/kg BK (Behandeling 2) of 3.5 g/kg AB en 3.5 g/kg BK (Behandeling 3) of 3.5 g/kg AB en 5.2 g/kg BK (Behandeling 4) bevat. Agt rumen-gekannuleerde lakterende Holsteinkoeie is ewekansig aan die behandelings toegeken in ‘n 4 x 4 (n=2) Latynse vierkantontwerp met vier behandelings en vier periodes. Die totale eksperimentele periode was 100 dae, waartydens elke koei elke behandeling vir 18 dae ontvang het voor die datakolleksieperiode van 7 dae. Rumen pH is voortdurend, elke vier minute, oor ‘n twee-dae periode gemeet met behulp van draagbare dataloggers en pH elektrodes wat binne-in die rumen gesetel was. Rumenvloeistof is versamel vir die bepaling van vlugtige vetsuurkonsentrasies. Gedurende elk van die datakolleksieperiodes is die melkproduksie twee maal per dag geneem vir sewe agtereenvolgende dae en melkmonsters is tweemaal per dag versamel vir vyf agtereenvolgende dae vir komponent–analise (samestelling?). Koeie is ad libitum gevoer en voerinnames is individueel bepaal. Die behandelings het geen betekenisvolle invloed op melkproduksie, melksamestelling of voerinnames gehad nie. Rumen pH profiele van al die behandelings het aangedui dat die diëte goed gebuffer was. Die gemiddelde pH oor 24 uur was 6.0, 6.1, 6.1 en 6.2 vir Behandeling 1, 2, 3 en 4, onderskeidelik. Die pH het nie onder 5.8 gedaal vir enige van die behandelings nie en die toenemende vlakke van natriumbikarbonaat het ‘n verhoging in die daaglikse pH-profiele tot gevolg gehad. By die hoogste buffervlakke (Behandeling 4) het die pH-profiel tussen 6.1 en 6.5 gevarieer. Hoewel nie betekenisvol nie, het Behandeling 1 (slegs Acid Buf) numeries die hoogste melkproduksie getoon, sonder dat melkkwaliteit beïnvloed is. Dit is voorgestel dat te hoë rumen pH ‘n nadelige impak op melkproduksie kan hê, as gevolg van ‘n verhoogde asetaat:propionaat verhouding wat rumen doeltreffendheid benadeel. Behandelings het geen betekenisvolle invloed op totale vlugtige vetsuurkonsentrasies gehad nie, maar daar was ‘n neiging vir hoër totale vlugtige vetsuurkonsentrasies namate die vlakke van natriumbikarbonaat verhoog het. Die asetaat:propionaat verhouding van Behandeling 1 (2.91) was betekenisvol laer as dié van Behandeling 4 (3.65). Die gebruik van buffers wat reageer op toenemende suurheidsgraad kan dus aangewend word as ‘n doeltreffende en veilige oplossing vir rumen asidose. Die studie het bevestig dat ‘n daaglikse inname van 80 g Acid Buf deur koeie wat ‘n hoë kragvoerdieet ontvang, hoë melkproduksie ondersteun sonder dat melksamestelling nadelig beïnvloed word.

Data derived from a long-term grazing trial were used to determine short-term effects of mixed grazing by cattle and sheep in Highland Sourveld. Five cattle to sheep ratio treatments (viz. 1 :0, 3:1, 1 :1, 1 :3, 0:1) were applied, each at three stocking rates (viz. 0.5 (low), 0.71 (medium) and 1.0 (high) animal unit equivalents (AUE) ha¯¹). Ratios were expressed in terms of AUE cattle: AUE sheep. Stocking rate and ratio treatments were balanced at the start of each grazing season. Fourteen-month old Hereford steers and 'two-tooth' Merino wethers were used as experimental animals. The trial comprised two components, viz. an animal production component and a simulated component. The animal production component was conducted only in the medium stocking rate treatment where the effect cattle to sheep ratio on the performance of cattle and sheep was determined for each of four grazing seasons (viz. 1989/90, four-paddock rotational grazing The low and high stocking rate 1990/91, 1991/92, 1992/93). A management system was applied. treatments were implemented by simulating a four-paddock rotational grazing system and using a single paddock for each stocking rate/ratio combination. Grazing of the simulated treatments coincided with the grazing of a specific 'test' paddock in each ratio of the medium stocking rate treatment. These 'test' paddocks and the simulated treatment paddocks were monitored to determine the impact of mixed grazing by cattle and sheep on individual grass plants and the sward. The whole of the experimental area was rested during the growing season prior to the start of the trial and all paddocks were burnt in the dormant season just before the start of the first grazing season. The trial therefore commenced with a with a uniform sward of immature herbage in all paddocks allocated to each group of animals. ln the second and subsequent growing seasons only those paddocks which had been rested in the previous season were burned prior to the onset of growth in early spring. Rainfall for the first three grazing seasons was similar to the long-term mean of 790mm whilst the last season was considered 'dry' with 554mm recorded during 1992/93. In all grazing seasons, as the proportion of cattle in the species mix increased, sheep performance increased. A decline in sheep performance was recorded in each ratio treatment from the first to the third season. This decline was attributed to the increased maturity and thus lower quality of herbage on offer to the sheep, and the fact that only one paddock available to the animals in the second and third grazing seasons had been burned prior to the start of the season. Sheep performed best during the 'dry' season where herbage quality was maintained for longer into the grazing season than in previous seasons. In contrast, cattle performance was affected by the stocking rate (animals ha¯¹) of cattle rather than the presence of sheep. As the quantity of herbage on offer per steer declined steer performance declined. Animal performance data were also used to predict the effects of adding cattle to a sheep production enterprise and vice versa. The general trends were that the introduction of cattle into a low stocking rate, sheep-only production enterprise would allow for an increase in the stocking rate of sheep while maintaining the performance of the sheep. In this way the carrying capacity of a farm may be improved. Stocki ng rate and ratio treatments varied from those established at the start of each grazing season due to the differential performance of the cattle and sheep in each treatment. As the proportion of cattle in the species mix increased, stocking rate increased and the ratio widened in favour of cattle. Stocking rate (AUE ha¯¹), calculated a posteriori for each season, was the major influence on the severity of grazing on individual plants and within patches. As stocking rate of cattle and sheep at the various ratios increased, the extent and severity of grazing increased. At stocking rates in excess of O.8AUE ha¯¹ however, sheep-only grazing resulted in a greater proportion of plants, per species and per area, being grazed more severely than was the case for an equivalent stocking rate (AUE ha¯¹ ) of cattle. Furthermore, cattle and sheep had similar effects on patch size distribution when stocked at the same number of AUE ha¯¹. There were no measurable effects of stocking rate and ratio on proportional species composition and basal cover over a two year monitoring period. A technique for estimating basal cover in tufted grasslands was developed and is presented as an appendix to the thesis. Data were also used to evaluate the use of AUE as an integral part of the grazing capaci ty concept. Results indicated that cattle and sheep cannot be equated in terms of AUE when referring to the grazing impact. It is suggested that the definition of grazing capacity should include the species of livestock and assume a grazing management system appropriate to the grazing habit of the animals concerned. Resul ts of the trial provide strong indications that, in the long-term, the current recommendations of grazing cattle together with sheep in order to prevent the degradation or loss of veld condition which occurs in sheep-only grazing systems, will not succeed. A four-paddock rotation grazing system does not appear to be an appropriate veld management system for sustainable sheep production in sour grassveld. An alternative approach to veld management is suggested in which the sheep are confined to only those areas of the farm which were burnt at the start of the grazing season. Ideally, sheep should not allocated to the same paddock for two consecutive grazing seasons. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.

Three experiments compared ruminal, physiological, and performance responses of beef steers consuming hay ad libitum and receiving grain-based supplements with (CAM) or without (CO) inclusion of camelina meal. In Exp. 1, 9 steers fitted with ruminal cannulas received CAM (2.04 kg of DM/d) or CO (2.20 kg of DM/d). Steers receiving CAM had reduced (P = 0.01) total DMI and tended to have reduced (P = 0.10) forage DMI compared to CO. No treatment effects were detected (P ≥ 0.35) for ruminal hay degradability parameters. In Exp. 2, 14 steers receiving CAM (1.52 kg of DM/d) or CO (1.65 kg of DM/d) were assigned to corticotropin-releasing hormone (CRH; 0.1 μg/kg of BW) and thyrotropin-releasing hormone (TRH; 0.33 μg/kg of BW) challenges. Steers receiving CAM had greater (P < 0.05) serum concentrations of PUFA compared to CO prior to challenges. Upon CRH infusion, mean plasma ceruloplasmin concentrations increased at a lesser rate in CAM compared with CO (P < 0.01). Upon TRH infusion, no treatment effects were detected (P ≥ 0.55) for serum TSH, T₃, and T₄. In Exp. 3, 60 steers were allocated to 20 drylot pens. Pens were randomly assigned to receive CAM (2.04 kg of DM/steer daily) or CO (2.20 kg of DM/steer daily) during preconditioning (PC; d -28 to 0). On the morning of d 0, steers were transported for 24 h. Upon arrival from transport on d 1, pens were randomly assigned to receive, in a 2 x 2 factorial arrangement, CAM or CO during feedlot receiving (FR; d 1 to 29). During PC, CAM had reduced (P < 0.01) forage and total DMI, and tended to have reduced (P = 0.10) ADG compared to CO. Plasma linolenic acid concentrations increased during PC for CAM, but not for CO (P = 0.02). Steers that received CAM during FR had greater (P < 0.05) mean plasma concentrations of PUFA, and reduced mean rectal temperature and concentrations of haptoglobin and ceruloplasmin during FR compared to CO. Therefore, camelina supplementation reduced forage and total DMI, did not alter thyroid gland function, increased PUFA concentrations in blood, and attenuated the acute-phase protein reaction elicited by neuroendocrine stress responses. In conclusion, camelina meal is a feasible ingredient to reduce stress-induced inflammatory reactions and potentially promote cattle welfare and productivity in beef operations. / Graduation date: 2012

Twenty four Jersey calves were randomly blocked according to sex and birth date, to determine the effects of supplementing Carica papaya seed (Linn) meal (CPSM) on health and growth performance of calves. In the first study, calves were fed CPSM for only 2 days to determine faecal pathogen population. In the second study; calves were randomly assigned at birth to three treatments and fed until weaning at 42 days. Each treatment had six calves. Treatments were; 1) a control group, which did not receive additive; 2) a group that was supplemented 5 g/d of Carica papaya seed meal (CPSM) and 3) the last group that was supplemented 5 g/d of a commercial product containing Lactobacillus acidophilus (Lact). After receiving milk with colostrum from their dams for 3 consecutive days after birth, calves had commercial starter pellet and fresh water ad lib. Treatments were added to whole milk from day 4 and fed to calves before being allowed to suckle from the dams for 30 min three times a day (08:00; 12:00 and 17:00). Calf starter dry matter intake (DMI) was evaluated daily while body weight (BW) and body structural growth were measured weekly. Faecal samples were collected directly from the rectum on day 7 and 10, before and after receiving CPSM respectively. The DMI; DMI/BW; BW and BWG of calves did not differ among treatments, and averaged 305.4 g/d; 7.7 g/d per BW; 39.4 kg and 32.1 kg, respectively. The initial BW, 22.2 ± 1.49 kg did not differ among groups, but the weaning BW was higher (p<0.05) for CPSM fed calves compared to control diet fed calves. It did not differ between control and Lact calves. Calves in Lact and CPSM treatments had similar average daily gain (ADG) and heart girth (HG), which were higher (p<0.05) than calves fed the control treatment. Calves fed CPSM had higher (p<0.05) hip width (HW) and shoulder height (SH) than control calves. There were effects of time (p<0.001) for starter DMI/BW, ADG and all structural body parameters, and effects (p<0.05) of interaction between time and treatments for only starter DMI/BW, ADG and HG. The CPSM treatment reduced faecal coliforms and E. coli (p<0.05) by 93.6% and 96.1%, respectively; and tended to reduce Enterobacteriaceae (p=0.056) by 96.4%. The present study revealed that feeding CPSM to calves during the pre-weaning period increased growth performance by improving average daily gain, feed efficiency and enhancing health status due to low faecal pathogen count / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)

Made available in DSpace on 2015-03-26T13:55:25Z (GMT). No. of bitstreams: 1 texto completo.pdf: 417808 bytes, checksum: ecda1eac9d6d0454a9a2d4ffa4e6b8fe (MD5) Previous issue date: 2014-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The basic objective established for this study was to quantify the consumption of dry matter, nutrients and digestible energy of cattle depending on the supply of fiber in the diet. The experiment was conducted in two latin square and balanced for four treatments. Four levels of daily supply of insoluble neutral detergent fiber (3, 6, 9 and 12 g / (kg.dia)), scaled to the body mass of animals were used. Eight crossbred steers, four with 298 ± 27 kg and four with 219 ± 16 kg, were randomly divided, at the beginning of the experiment, as columns in latin squares. Consecutive experimental periods lasted for 21 days, as follows: adjustment period of 14 days and the collection period of seven days. Samples of diets offered, orts and feces were dried, ground and analyzed for dry matter, crude fat, ash, crude protein, neutral detergent insoluble fiber and gross energy. The nutrient intake, digestible nutrients, digestible energy and the amount of feces produced daily were scaled to metabolic size. The exceptions were for the intake of fiber and lignin, corrected for W1 (g/(kg.dia). The linear mixed model was fitted to the variables described staggered, after logarithmic transformation. The statistical model was fitted using the Proc Mixed of SAS, using the method of restricted maximum likelihood (REML). The probability likelihood of the different structures of variance and covariance was assessed using the Akaike information criterion, corrected for small samples. Null hypotheses on the treatment factor and the respective linear and quadratic components were rejected when P < 0.05. The relationship between digestible energy intake and fiber intake, and intake of digestible protein and fiber intake were analyzed considering the allometric model and five hypotheses. The models in these assumptions were adjusted using Proc Mixed of SAS. The same variance and covariance structures listed above were considered and employed the same criteria of verisimilitude already described for the choice (s) best (s) event (s) represent the reality of the data. The adjustment of the variables, using different structures of covariance showed that the structure of variance components was the best choice for most variables, followed by unstructured variance-covariance, heterogeneous structure composed symmetry, Spatial and Spatial power. The variables FAsh , RAsh , RLig , FLig , FFC e DFC showed a quadratic effect, while the other variables showed a linear effect, which can be seen by their equations. With the increase of fiber content in the diet, there is a growing incidence of observed values for variables neutral detergent fiber, dry matter, ash and lignin. However, close to the level of 12 g, there is a tendency of stabilization of the predicted values. In terms of these variables, just the curve of mineral matter excretion in feces presents different behavior, being more stable to level 3 g up to 6 g, and growing from this level. Variables compounds neutral detergent soluble, organic matter, dry matter, crude protein and gross energy showed predicted values with linear growth, which indicates a non-limiting consumption of these variables by increasing the fiber content in the diet. However, the nonfiber carbohydrates and crude fat results showed constant intake and digestibility, indicating that increasing the fiber content in the diet did not influence these data. The relationship between digestible energy intake and fiber intake was analyzed according to the assumptions described in the methodology, and the one that most fit to the data of the present study was the hypothesis 5, whatever they are &#945;1 , &#945;2 , &#946;1 and &#946;2 . The variance-covariance structure that best fit the hypothesis was variance components, with a significant quadratic effect of level of NDF actually consumed. The relationship between consumption of digestible protein and fiber intake was also analyzed and showed similar results to the assumptions previously tested and the variance- covariance structures. Therefore, it can be concluded that the consumption of fiber per dairy crossbred cattle exhibits a tendency towards stabilization, near the level of supply of NDF in the diet of the order of 10.9 ± 2.6 g/(kg.day). The intake and excretion of lignin are coincident within the range of 3 to 7 g/(kg.day) supply of NDF in the diet. This may explain why lignin be characterized as a nutritional entity digestion trials conducted maintenance level, whose offer of NDF find yourself situated within the limits of the present study. / O objetivo básico estabelecido para o presente trabalho foi o de quantificar o consumo de matéria seca, nutrientes e energia digestível de bovinos em função da oferta de fibra na dieta. O experimento foi conduzido em dois quadrados latinos simultâneos e balanceados para quatro tratamentos. Foram utilizados quatro níveis de oferta diária de fibra insolúvel em detergente neutro, escalonada para a massa corporal dos animais: 3, 6, 9 e 12 g/(kg.dia). Oito bovinos mestiços, quatro com 298 ± 27 kg e quatro com 219 ± 16 kg, foram divididos aleatoriamente, no início do experimento, como colunas nos quadrados latinos. Os períodos experimentais consecutivos tiveram duração de 21 dias, assim distribuídos: período de adaptação de 14 dias e período de coleta de sete dias. Amostras das dietas oferecidas, sobras e fezes foram secas, moídas e analisadas para matéria seca, gordura bruta, cinzas, proteína bruta, fibra insolúvel em detergente neutro e energia bruta. O consumo de nutrientes, de nutrientes digestíveis, de energia digestível e a quantidade de fezes produzidas diariamente foram escalonadas para o tamanho metabólico. As exceções foram para a ingestão de fibra e lignina, por seus turnos, corrigidas para W1 (g/(kg.dia). O modelo linear misto descrito foi ajustado às variáveis escalonadas, após transformação logarítmica. O modelo estatístico foi ajustado utilizando-se o Proc Mixed do SAS, por meio do método de máxima verossimilhança restrita (reml). A probabilidade de verossimilhança das diferentes estruturas de variâncias e covariâncias foi avaliada a partir do critério de informação de akaike, corrigido para pequenas amostras. Hipóteses nulas sobre o fator tratamentos e seus respectivos componentes linear e quadrático foram rejeitadas sempre que P<0,05. As relações entre o consumo de energia digestível e o consumo de fibra, e consumo de proteína digestível e consumo de fibra foram analisadas considerando-se o modelo alométrico e cinco hipóteses. Os modelos constantes nestas hipóteses foram ajustados por meio do Proc Mixed do SAS. Foram consideradas as mesmas estruturas de variâncias e covariâncias listadas anteriormente e empregados os mesmos critérios de verossimilhança já descritos para escolha da(s) melhor(es) hipótese(s) a representar(em) a realidade dos dados. O ajuste das variáveis, utilizando diferentes estruturas de variância-covariância, mostrou que a estrutura de componentes de variância foi a melhor escolha para a maioria das variáveis, seguido por variância- covariância não estruturada, estrutura heterogênea, simetria composta, Spatial power e Spatial. As variáveis FCinza , RCinza , RLig , FLig , FCF e DCF apresentaram efeito quadrático, enquanto as demais variáveis apresentaram efeito linear, o que pode ser observado pelas suas equações. À medida que aumentou-se o teor de fibra na dieta, observa-se um crescente aumento dos valores observados para variáveis fibra em detergente neutro, matéria seca, cinzas e lignina. No entanto, próximo ao nível de 12 g, observa-se uma tendência de estabilização dos valores preditos. Em relação a essas variáveis, apenas a curva de excreção de matéria mineral nas fezes apresenta comportamento diferente, sendo mais estável do nível 3 g até o 6 g, e crescendo a partir desse nível. As variáveis nutrientes digestíveis solúveis, matéria orgânica, matéria seca, proteína bruta e energia bruta apresentaram valores preditos com crescimento linear, o que indica uma não limitação do consumo dessas variáveis pelo aumento do teor de fibra na dieta. Contudo, as variáveis carboidratos não fibrosos e gordura bruta apresentaram resultados constantes de consumo e digestibilidade, indicando que o aumento do teor de fibra na dieta não influenciou esses dados. A relação entre o consumo de energia digestível e o consumo de fibra foi analisada segundo as hipóteses descritas na metodologia, e a que mais se ajustou aos dados do presente trabalho foi a hipótese 5, quaisquer que sejam &#945;1 , &#945;2 , &#946;1 e &#946;2 . A estrutura de variância-covariância que melhor se ajustou à hipótese foi componente de variância, sendo significativo o efeito quadrático do nível de FDN efetivamente consumido. A relação entre consumo de proteína digestível e consumo de fibra também foi analisada e apresentou o mesmo resultado para as hipóteses testadas anteriormente e das estruturas de variância-covariância. Portanto, pode-se concluir que o consumo de fibra por bovinos mestiços leiteiros apresenta tendência à estabilização, próximo ao nível de oferta de FDN na dieta da ordem de 10,9 ± 2,6 g/(kg.dia). O consumo e a excreção de lignina são coincidentes dentro da faixa de 3 a 7 g/(kg.dia) de oferta de FDN na dieta. Tal fato pode explicar o porquê de a lignina ser caracterizada como entidade nutricional em ensaios de digestão conduzidos em nível de mantença, cuja oferta de FDN encontre-se situada nos limites encontrados no presente estudo.

The assessment of the level of nutrition of dairy cattle in relation to their milk pruduction was carried out under operating conditions. The focus was on the quality of the roughage feed, the feeding technique, the contents of the diet and the supply of nutrients. On the basis of operating and economic indicators, the milk production costs as well as an overall evaluation summing the individual observed periods have been calculated. The results of the observation of the level of nutrition over a three-year period indicate that the feed rations are prepared according to the optimal standards. In the observed periods, first quality* corn silage and first or second quality** corn silage was always used. The average efficiency of a cow reached 7 000 kg of milk per year. The average cost of one litre of thus produced milk was 9,30 CZK in an average day, and the average sum of money needed came in at 138,37 CZK.

Variations in composition and disappearance of nutrients in dairy cattle feeds are dictated by ingredients, methods of processing, storage while milk production levels depend on the animal, environmental factors and largely on pools of available carbohydrates, proteins, vitamins and minerals in the concentrate feeds. There is a wide variety of concentrates for dairy cattle on the formal and informal markets and dairy farmers need to be astute in selecting feeds appropriate for specific production periods and animals to sustain their businesses. Composition of nutrients displayed on concentrate containers is however inadequate for in-depth assessment of products. This study determined nutrient composition, rumen dry matter disappearance and microbial colonization on residual substrate on commercial concentrate feeds and simulated total mixed rations for dairy calves, heifers, lactating and dry cows based on common feeding guidelines. Equivalent feeds for each herd group were obtained from three suppliers in the formal markets in Gauteng province of South Africa, making a total of twelve. An analysis of the data on container labels for the herd groups displayed similar feed values, as also reflected on the recommendation Tables of Act 36: Feeds and Fertilizer bill 1947 of South Africa. / Agriculture, Animal Health and Human Ecology / M.Sc. (Agriculture)