Long-term trends in rangeland sward dynamics (species composition, structure, productivity) were examined on three trials established between 1989 and 1996 at Kokstad Research Station in the Highland Sourveld, while animal performance (average daily gain and gain per hectare) was examined on two of the trials. The region enjoys moderate rainfall of 782mm per annum, with hilly topography, and soil depths ranging from >1m to <20cm. The first trial was labelled the simulation trial, as it simulated a four-paddock rotational grazing system, in which animals spent two weeks in each of three paddocks while the fourth was rested for the entire season. The rested paddock was rotated each year. The trial tested two stocking rates (0.5 and 1.0 AU.ha-1) at five ratios of cattle to sheep, ranging from cattle only to sheep only. The trial was unreplicated, and was established in 1989 on flat topography with deep soils. The second trial (labelled the flat two-paddock trial) was established in 1992 adjacent to the simulation trial. The trial examined two stocking rates of sheep weaners (0.5 and 1.0 AU.ha-1 seasonally) in a continuous grazing two-paddock system, in which one paddock of each treatment was burned and grazed continuously while the second paddock was rested, to be burned and grazed in the following season. The trial was replicated twice. The third trial (labelled the steep two-paddock trial) mimicked the grazing system of the flat trial, but was located on a steep (c. 20%) West-facing slope with shallow soils. The trial incorporated two additional treatments: an intermediate stocking rate of 0.7 AU.ha-1 and an ungrazed treatment. Species composition of the sward was recorded biennially on all trials using the nearest plant-point technique with between 200 and 800 points per paddock. Sward standing crop was measured in the rested seasons of the simulation trial and at the beginning, middle and end of each season in one paddock of each two-paddock treatment of the two-paddock trials. In the two-paddock trials, sward standing crop was measured within and outside permanently placed exclosure cages. Animals were weighed fortnightly. The response of species to grazing pressure or animal type was mediated by soil depth and slope, as well as the grazing system. Tristachya leucothrix declined on all grazed treatments. The ungrazed treatments remained relatively stable over ten years. On the low stocking rate treatments of the steep trial, unpalatable species increased, but so did Themeda triandra. The heavily grazed treatment of the steep trial was surprisingly stable, with little significant change in relative abundance of key species other than an increase in the unpalatable Alloteropsis semialata and decline in T. leucothrix. The medium stocking rate treatment on the steep trial showed significant shifts in relative abundance of key species, with declines in T. triandra and T. leucothrix and increases in A. semialata and the unpalatable wiregrass D. filifolius. These trends were not repeated on the flat trial, however, with T. triandra and A. semialata increasing and all other key species declining or remaining stable. On the simulation trial, species responded largely unpredictably with species abundances often fluctuating considerably over time. Microchloa caffra and A. semialata increased substantially in both the low and high stocking rate sheep-only treatments, with a concurrent decline in T. triandra in the high stocking rate but not the low. Changes in composition over time, as measured by Euclidean distance, showed that shallow soils, high stocking rates and a high proportion of sheep caused greater shifts in species composition over time than deep soils, low stocking rates or more cattle. Three treatments, the sheep-only treatments on the simulation trial and the high stocking rate on the steep trial, showed an initial rapid shift in composition over about 6 years, before stabilising in subsequent seasons. The flat trial showed no substantial shift in composition over time. This general pattern of change was confirmed by Non-Metric Multidimensional Scaling. On the simulation trial, total standing crop was influenced by stocking rate and by the proportion of sheep in most seasons. On the two-paddock trials, increasing stocking rate significantly reduced sward vigour, and vigour declined over time. Stocking rate reduced total standing crop on both trials at the end of the 2004/05 seasons and the crop of unpalatable species on the steep trial. Total palatable plants were unaffected by stocking rate on both trials. The classic Jones-Sandland model of animal performance as influenced solely by stocking rate was not supported. Sheep performance was influenced by stocking rate and the interaction of stocking rate and seasonal rainfall. There was no difference in average daily gain between treatments over time, and hence cumulative animal production per hectare increased with increasing stocking rate. Animal performance was possibly influenced by many factors beyond the scope of this study, including the effect of predator attacks on surviving animals, and resource availability such as shade and shelter and high-production patches in some paddocks and not others. Scale effects on ecology are being increasingly investigated and a meta-analysis of this type shows that, even in one research farm, slight differences in management and environment can have significant effects on plant and animal responses to grazing. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

An experiment was conducted using forty-one Bonsmara steers (age ± 7 months) to determine the effect of zilpaterol hydrochloride (ZH) on the growth performance and carcass characteristics. The trial was structured using a completely randomized design with two treatments, control and ZH group. The steers were fed ZH for 28 consecutive days at the end of the finishing period and ZH was withdrawn from the diet 2 days prior to slaughter of the animals. The steers were placed in individual pens and weighed fortnightly throughout the 4 months trial. Zilpaterol hydrochloride (ZH) was included in the diet at a rate of 8.3 mg/kg of DM. Feeding of ZH increased (P< 0.05) body weight (BW) gain and ADG (1.102 vs. 1.444) and tended to increase (P = 0.067) feed efficiency (F:G) during the last month of the finishing period. There were no significant differences (P> 0.05) in daily dry matter intakes (DMI). For the control group, high treatment weight gains were significantly associated with high initial weight (r = 0.424, P = 0.049) and also high pre-treatment body weight (r = 0.678, P= 0.001). Treatment weight gain increased as the initial and pre-treatment weight gain increased in the control group. For the steers that were fed ZH, there was no significant correlation between the treatment body weight gain with initial weight (r = 0.097, P = 0.694) and also pre- treatment live weight (r = 0.393, P = 0.096). Supplementation of ZH significantly increased (P < 0.0001) the dressing percentage (56.4% vs. 58.4%) and had no significant (P>0.05) effect on the carcass weight. The outcome of the study suggest that supplementation of ZH in the diet during the last month of the finishing period enhances growth performance and shows the repartitioning capacity of the feed additive as a beta- agonist. / Agriculture and  Animal Health / M. Sc. (Agriculture (Animal Science)

Made available in DSpace on 2015-03-26T13:55:24Z (GMT). No. of bitstreams: 1 texto completo.pdf: 614632 bytes, checksum: eac726a0efd1eec87578c9745a474e81 (MD5) Previous issue date: 2014-02-26 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work aimed to evaluate the effects of ruminal and/or abomasal protein supplementation in cattle fed tropical forages on nutritional variables, degradation of insoluble fiber, activity of fibrolytic enzymes and rumen bacterial communities profile. Two experiments were carried out sequentially, and in the same way, differing only on the forage quality that was defined based on crude protein content: medium quality (784 g of crude protein/ kg of dry matter) and high quality (986 g of crude protein/ kg of dry matter). Four Nellore young bulls, averaging 227±11 kg body weight and fitted with ruminal and abomasal cannullas, were used. The following treatments were evaluated: control (only forage), ruminal nitrogenous compounds supplementation (daily supply of 230 g of crude protein in the rumen), abomasal nitrogenous compounds supplementation (daily supply of 230 g of crude protein in the abomasum), and ruminal and abomasal nitrogenous compounds supplementation (daily supply of 230 g of protein, being 115 g in the rumen and 115 g in the abomasum). Casein was used as protein source for supplementation and basal diet consisted of Tifton 85 (Cynodon spp) hay. Two 4 x 4 Latin squares experimental trials, balanced for residual effects, with four treatments, four animals and four experimental periods lasting 29 days each, were implemented sequentially, one for each forage as stated above. There were no effects (P>0.05) of supplementation scheme or forage quality on organic matter (OM) intake. On the other hand, neutral detergent fiber (NDF) intake was higher (P<0.05) when animals were fed high quality forage. The total digestibility of OM was increased (P<0.05) by supplementation and by increasing forage quality. The digestibility coefficient of NDF was not affected by supplementation scheme (P>0.05), but was increased by the enhancing in forage quality. The apparent ruminal nitrogen balance (RNB) was increased (P<0.05) when animals were supplemented in rumen or in both rumen and abomasum cannula. It is worth highlighting that no supplementation or exclusively abomasal supplementation led to negative values of RNB. The apparent nitrogen balance (NB) was increased (P>0.05) when high quality forage was fed to the animals and by supplementation, no matter if the supplement was infused into rumen, abomasum or both. Ruminal supplementation enhanced (P<0.05) the concentration of rumen ammonia nitrogen (RAN). Although, animals supplemented in rumen and abomasum or exclusively in abomasum did not exhibit increase in RAN concentrations (P>0.05) when compared to no supplemented animals. The bacterial richness and diversity (Shannon-Wiener index) associated with the solid phase of rumen digesta were not affected (P>0.05). However, richness and diversity associated with the liquid phase were increased (P<0.05) by the improvement in forage quality. NDF degradation rate (kp) was enhanced (P<0.05) by ruminal supplementation. Carboximetilcellulase activity was decreased (P<0.05) by the abomasal and ruminal/abomasal supplementation. Xylanase activity was decreased (P<0.05) by both post-ruminal supplementation schemes, when high quality forage was fed to the animals. It was not detected correlations among variables associated with bacterial diversity and activity and variables associated with nutritional performance, excepted for the positive correlation between kp and RNB Clustering analyses based on the Unweighted Pair Group Method (UPGMA) evidenced that distinct bacterial communities are associated with liquid and solid fraction, independently of the forage quality. Clustering analyses also showed that forage quality affects the diversity of liquid phase associated bacteria, even though, effects on solid phase was not clear. None of the evaluations related to the microbial community were able to detect clear effects of supplementation on the microbial community diversity. Improving forage quality enhances fiber digestibility, nitrogen balance and modifies the bacterial community associated with liquid phase. On the other hand, protein supplementation enhances the nitrogen retention in animal body. / Objetivou-se avaliar os efeitos da suplementação proteica ruminal e/ou abomasal em bovinos consumindo forragens tropicais sobre as características nutricionais, a atividade enzimática fibrolítica, a degradação in vitro da fibra insolúvel e o perfil da comunidade bacteriana ruminal. Dois experimentos foram realizados sequencialmente diferindo apenas na qualidade do feno ofertado, sendo de média qualidade (78,4 g de proteína bruta/kg de matéria seca) e alta qualidade (98,6 g de proteína bruta/kg de matéria seca), respectivamente. Os procedimentos experimentais foram os mesmos para ambas as forragens. Foram utilizados quatro novilhos Nelore, não castrados, com peso corporal médio de 227±11 kg, fistulados no rúmen e no abomaso. Foram avaliados os seguintes esquemas de suplementação: controle (somente forragem); suplementação nitrogenada ruminal (fornecimento diário de 230 g de proteína suplementar no rúmen); suplementação nitrogenada abomasal (fornecimento diário de 230 g de proteína suplementar no abomaso) e suplementação nitrogenada ruminal e abomasal (fornecimento diário de 230 g de proteína suplementar, sendo 115 g no rúmen e 115 g no abomaso). A alimentação volumosa basal foi constituída por feno de tifton 85 (Cynodon spp) e como fonte de compostos nitrogenados suplementares foi utilizada a caseína (caseína pura, Labsynth). O experimento foi conduzido segundo delineamento em quadrado latino 4 x 4 balanceado para efeitos residuais, sendo dois quadrados sequenciais, um para cada forragem, com quatro esquemas de suplementação, quatro animais e quatro períodos experimentais com 29 dias em cada quadrado. Não foram observados efeitos (P>0,05) da qualidade da foragem ou do esquema de suplementação sobre o consumo de matéria orgânica (MO). Por outro lado, o consumo de fibra em detergente neutro (FDN) foi superior (P<0,05) quando forragem de alta qualidade foi ofertada aos animais. O coeficiente de digestibilidade total da MO foi incrementado (P>0,05) pela suplementação e pela melhoria na qualidade da forragem. O coeficiente de digestibilidade da FDN não foi afetado pelo esquema de suplementação (P>0,05), mas foi superior quando os animais receberam forragem de alta qualidade (P<0,05). O balanço aparente de compostos nitrogenados no rúmen (BNR) foi ampliado (P<0,05) pela suplementação no rúmen e no rúmen-abomaso. Ressalta-se que a ausência de suplementação ou a suplementação exclusiva no abomaso proporcionam valores negativos de BNR. O balaço aparente de compostos nitrogenados no organismo animal foi ampliado (P<0,05) pelo fornecimento de suplemento, independentemente do local de suplementação, e pelo fornecimento de forragem de melhor qualidade A suplementação no rúmen incrementou (P<0,05) a concentração de nitrogênio amoniacal ruminal (NAR). Por outro lado, animais recebendo suplementação no rúmen e abomaso ou exclusivamente no abomaso apresentaram concentrações de NAR similares (P>0,05) a animais não suplementados. A riqueza e a diversidade microbiana da fase sólida da digesta ruminal não foram afetadas (P>0,05). Entretanto, a riqueza e a diversidade bacteriana associada à fase líquida da digesta ruminal foram incrementadas (P<0,05) pela melhoria na qualidade da forragem. A taxa de degradação da FDN foi ampliada (P<0,05) pela suplementação no rúmen. A atividade da carboximetilcelulase foi reduzida (P<0,05) pela suplementação no abomaso e rúmen-abomaso. A atividade da xilanase foi deprimida (P<0,05) pela suplementação pós-ruminal somente quando forragem de alta qualidade foi fornecida aos animais. Não foi observada correlação (P>0,05) entre as variáveis associadas à atividade enzimática e diversidade microbiana e as características ligadas ao desempenho nutricional, exceção feita à correlação positiva (P<0,05) entre a taxa de degradação da FDN e o BNR. A avaliação multivariada da diversidade permitiu evidenciar que comunidades bacterianas distintas estão associadas às frações líquida e sólida, independente da qualidade da forragem ofertada. Percebeu- se que a variação na qualidade da forragem influencia a diversidade microbiana associada à fração líquida do fluido ruminal, embora não tenha exercido tal efeito sobre a fração sólida. Em nenhuma avaliação percebeu-se efeito claro do esquema de suplementação sobre o perfil da comunidade microbiana ruminal. A melhoria da qualidade da forragem amplia a digestibilidade da fibrae a retenção de nitrogênio e é capaz de modificar a comunidade bacteriana associada à fração liquida do conteúdo ruminal. A suplementação proteica, por sua vez, independentemente do local de suplementação, amplia a retenção de nitrogênio no organismo animal.

Text in English / Cow size influences biological efficiency of individual animals, which influences herd composition and stock flow. This in turn influences the economic efficiency of the herd. This research followed the thread from animal size, to biological efficiency, to economic efficiency for beef cattle production under a typical production system in semi-arid South Africa. Cattle were grouped into three groups namely small, medium and large cattle, with mature weights of 300kg, 450kg and 600kg respectively. The net energy requirements of individual cattle were calculated for maintenance, growth, lactation and foetal production, for each of the three sizes. Growth rates, milk yield, reproduction rates, and management practices were assumed from existing research. Next the stock flow for a herd of small, medium and large cattle were calculated from the above. Income and expenses as commonly used in the research area were calculated from the stock flow. Gross profit above allocated costs were subsequently calculated for the three herds under the above-mentioned conditions. When assuming similar reproduction and growth rates for small, medium and large mature cattle, the following results were obtained: more heads of small cattle could be held on a set resource base, but the total live weight of a herd of large cattle that could be held on the same resource base was greater. This was mostly due to proportionately lower maintenance energy requirements in the herd of large cattle. In the simulation in this study, maintenance energy requirements for the herd of large cattle was 71.2%, compared to 72.0% for the herd of medium cattle and 73.1% for the herd of small cattle. Income from the herd of small cattle was the lowest, as less kilograms of beef were available to sell. Allocated costs for the herd of small cattle were the highest, due to a large number of expenses being charged per head of cattle. As a result, the herd of large cattle were more economically efficient than their smaller counterparts. Income above allocated costs for the herds of large, medium and small cattle were R1,182,865, R1,085,116 and R946,012 respectively. Larger cattle generally have a lower reproduction rate under similar conditions. No equation exists that directly links size to reproduction rates, especially considering the vast number of variables that influences reproduction rates. However, in the form of scenarios, it could be calculated that, given a reproduction rate of 80% for mature small cattle, when reproduction rates of large cattle were 24.7% lower than that of small cattle and the reproduction rates of medium cattle were 15.4% lower than that of small cattle, the large and medium herds became less profitable than the small herd. Smaller cattle mature faster than larger cattle which provides the opportunity for early breeding. When small cattle were bred early, at 15 months, at a calving rate of only 44.5% it was more profitable than when the same cows were bred at 24 months. When medium cattle were bred at 15 months, a calving rate of 37.0% was needed to be more profitable than when they were bred at 24 months. Even when the herd of small cattle were bred at 15 months with a reproduction rate of 100%, it could still not match the profitability of the herd of large cattle bred at 24 months given the reproduction rates of all other classes of animals were similar. When the herd of medium cattle were bred at 15 months, at a calving rate of 53.7%, it matched the profit of the herd of large cattle that were bred at 24 months, when the reproduction rates of other classes were equal. Scenarios were considered were feed intake was limited. When feed was limited to a specific amount, smaller cattle were more biologically efficient and cattle with potential for small mature sizes would grow to a larger size than cattle with potential for medium and large mature sizes. When feed was limited by a factor of the calculated energy requirements of small, medium and large cattle, large cattle were more effective. This is because large cattle use proportionately less energy for maintenance, which allows more energy to be allocated to growth, lactation and foetal production. When energy was limited to an amount per unit of metabolic weight, small cattle were more efficient than medium and larger cattle in the growth and production phases. Small, medium and large cattle were equally efficient (or inefficient) in the maintenance and lactation phases. Energy requirements of cattle in South Africa are commonly calculated using the Large Stock Unit (LSU). The LSU typically overestimates energy requirements for cattle, except in the lactation phase. When using the LSU to match small, medium or large cattle to a resource base, the LSU overestimates energy requirements of large cattle proportionately more than that of small and medium cattle. This is excluding the lactation phase, where energy requirements for all three sizes are underestimated and that of large cattle underestimated proportionately more. There are more considerations when matching cow size to managerial practices. A smaller body size is a natural adaptation to a semi-arid environment and this adaptation can be expressed in different ways. The number of animals on a resource base has implications on management practices. Having more heads of cattle on a resource base increases genetic variation of the herd, allowing for genetic progress to be made faster than in herd of fewer cattle. / Agriculture and  Animal Health / M.Sc. (Agriculture)

This study investigated the effects of Brevibacillus laterosporus and live yeast (LY) on rumen fermentation, nutrient digestibility and microbial protein synthesis. The basal diet was a total mixed ration formulated to fulfil the minimum nutrient requirement of early lactating 600 kg Holstein cow producing 40kg of milk with 3.5 % fat and 3.3 % protein using CPM-dairy software (NRC, 2001). Treatments were: T1 (Control: basal diet with no additive), T2 (Basal diet + Brevibacillus laterosporus), T3 (Basal diet + Live yeast), and T4 (Basal diet + Brevibacillus laterosporus + Live yeast). In situ degradation, in vitro batch fermentation were performed. Data obtained were subjected to analysis of variance (ANOVA) using PROC GLM (SAS Institute, 2009). The effective dry matter (DM) degradability evaluated at low (0.02) and medium (0.05) ruminal passage rate (ED1 and ED2) were higher (p<0.05) in T1 compared to T2 and T3, but did not differ (p>0.05) between T2, T3 and T4, and between T1 and T4. When evaluated at fast passage rate (0.08) the effective DM degradability (ED3) was higher (p<0.05) in T1 compared to T3 and T4, but did not differ (p>0.05) between T1 and T2. The difference in ammonia nitrogen production was observed only between T1 and T2, and was higher (p<0.05) in T1. The total VFA’s concentration was higher (p<0.05) in T3 compared to the control. All additives decreased the molar percentage of acetate (P<0.05). The concentration of acetate was lower (p<0.05) in T3 and T4 compared to control. Propionate concentration was higher (p<0.05) in T3 and T4 compared to other treatments and lower (p<0.05) in the control compared to the rest of treatments. Butyrate concentration was higher (p<0.05) in T2 and T4 compared to the rest of the treatments, and lower (p<0.05) in T3 than other treatments. The microbial protein synthesis measured as purine derivate done on residues was higher (p<0.05) for T3 compared to T1 and T2, but did not differ between T1, T2 and T4, and between T3 and T4. These results showed that the two additives have different individual effects on DM and CP degradability, but also associative effects in some fermentation parameters such as propionate production. / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)