RESUMO

OBJECTIVE: Feed additives that modify rumen fermentation can be used to prevent metabolic disturbances such as acidosis and optimize beef cattle production. The study evaluated the effects of liquid and powdered forms of polyclonal antibody preparation (PAP) against Streptococcus bovis and Fusobacterium necrophorum on rumen fermentation parameters in ruminally cannulated non-lactating dairy cows that were adapted or unadapted to a high concentrate diet. METHODS: A double 3×3 Latin square design was used with three PAP treatments (control, powdered, and liquid PAP) and two adaptation protocols (adapted, unadapted; applied to the square). Adapted animals were transitioned for 2 weeks from an all-forage to an 80% concentrate diet, while unadapted animals were switched abruptly. RESULTS: Interactions between sampling time and adaptation were observed; 12 h after feeding, the adapted group had lower ruminal pH and greater total short chain fatty acid concentrations than the unadapted group, while the opposite was observed after 24 h. Acetate:propionate ratio, molar proportion of butyrate and ammonia nitrogen concentration were generally greater in adapted than unadapted cattle up to 36 h after feeding. Adaptation promoted 3.5 times the number of Entodinium protozoa but copy numbers of Streptococcus bovis and Fibrobacter succinogens genes in rumen fluid were not affected. However, neither liquid nor powdered forms of PAP altered rumen acidosis variables in adapted or unadapted animals. CONCLUSION: Adaptation of cattle to highly fermentable carbohydrate diets promoted a more stable ruminal environment, but PAP was not effective in this study in which no animal experienced acute or sub-acute rumen acidosis.

RESUMO

This study was carried out to evaluate the effects of chopped hay levels in high-concentrate diets with whole corn grain (WCG) on performance and carcass traits of finishing Nellore cattle. One hundred and eight 24-month-old Nellore intact males (453 ± 75 kg) were fed one of three WCG-based diets that differed in roughage level: without roughage (WCG), with 5% chopped hay included (WCG5), or with 12% chopped hay included (WCG12) in a block design (based on initial body weight) for 86 days. Animals fed WCG5 or WCG12 had significantly improved on final body weight, dry matter intake, average daily gain, feed efficiency, hot carcass weight, and dressing percentage when compared to those fed WCG. The Longissimus muscle area (P = 0.1108), backfat thickness (BFT; P = 0.6089), and rump fat thickness (P = 0.1798) were not affected by roughage levels. Therefore, using WCG diets without roughage negatively affects the performance of feedlot Nellore cattle but does not affect carcass traits and does lead to the minimum BFT required by the industry.

Assuntos

RESUMO

Replacing regular urea (RU) by slow-release urea (SRU) at two levels of non-protein nitrogen (NPN) in concentrate, offered with low-quality roughage, was evaluated in beef steers on dry matter intake (DMI), ruminal fermentation parameters, plasma urea nitrogen (PUN), total tract apparent digestibility of diets and in situ degradability of nitrogen sources. Eight ruminally cannulated steers were allocated into two 4x4 Latin squares, totalizing four treatments: 40 NPN/0 SRU: 40% of concentrate crude protein (CP) as NPN, resulting from 0% of SRU and 100% of RU; 40 NPN/50 SRU: 40% of concentrate CP as NPN, resulting from 50% of SRU and 50% of RU; 40 NPN/100 SRU: 40% of concentrate CP as NPN, resulting from 100% of SRU and 0% of RU; 80 NPN/100 SRU: 80% of concentrate CP as NPN, resulting from 100% of SRU and 0% of RU. Results showed that partial substitution of regular urea by slow-release urea did not alter dry matter intake, pattern of ruminal fermentation or plasma urea nitrogen concentrations and increased the total tract apparent digestibility of crude protein in steers diets. The increase in non-protein nitrogen content in crude protein of the concentrate could compromise feed intake and the efficiency of nutrient utilization in the steers fed complete diets based on low quality forage.

RESUMO

A capacidade dos bovinos de selecionar volumoso e concentrado em suas dietas em função de diferentes temperaturas foi estudada em 12 vacas fistuladas, durante 30 dias. Utilizou-se delineamento inteiramente casualizado com dois tratamentos: conforto (galpão, 21oC) e estresse (câmara bioclimática, 38oC), sendo a dieta composta por cana-de-açúcar acrescida de ureia e concentrado, alimentos oferecidos separadamente e à vontade. A capacidade de seleção dos animais foi identificada pela comparação da composição da dieta selecionada nos dois diferentes ambientes, assim como pelos parâmetros ruminais e digestibilidade. Foi observada redução (p < 0,05) de 22% no consumo diário de matéria seca nos animais em estresse térmico, enquanto que a relação concentrado:volumoso selecionada foi semelhante em ambos os tratamentos. Os parâmetros de fermentação ruminal mantiveram-se iguais em ambos os tratamentos. Entretanto, a digestibilidade da matéria seca e algumas de suas frações foram diminuídas nos animais estressados. Concluise que os animais mantidos sob estresse térmico reduziram a ingestão total de matéria seca, sem alterar a concentração de energia ou de fibra das suas dietas, provavelmente na tentativa de manter estável o ambiente ruminal.(AU)

The ability of cattle to select the roughage and concentrate in their diets under different environmental temperatures was studied in 12 cannulated cows, during 30 days. The experimental design was completely randomized with two treatments: thermal comfort (21oC) and thermal stress (climatic chamber, 38oC). Cows were fed a diet of sugar cane plus urea and concentrate mixture, which were offered separately and ad libitum. The ability of cows to select their diets was identified by comparing the composition of diet selected in different environments, as weel as ruminal parameters and diet digestibility. A significant decrease (p < 0.05) of 22% on total dry matter intake was observed in animals kept under heat stress compared to animals kept under comfort temperature, while concentrate:roughage ratio chosen was similar for both treatments. Ruminal parameters were equal for both treatments, while digestibility of dry matter and some of its fraction were reduced in stressed animals. Animals under heat stress decreased dry matter intake without changing dietary energy or fiber levels, probably attempting to maintain the stability of ruminal environment.(AU)

Assuntos

RESUMO

A capacidade dos bovinos de selecionar volumoso e concentrado em suas dietas em função de diferentes temperaturas foi estudada em 12 vacas fistuladas, durante 30 dias. Utilizou-se delineamento inteiramente casualizado com dois tratamentos: conforto (galpão, 21oC) e estresse (câmara bioclimática, 38oC), sendo a dieta composta por cana-de-açúcar acrescida de ureia e concentrado, alimentos oferecidos separadamente e à vontade. A capacidade de seleção dos animais foi identificada pela comparação da composição da dieta selecionada nos dois diferentes ambientes, assim como pelos parâmetros ruminais e digestibilidade. Foi observada redução (p < 0,05) de 22% no consumo diário de matéria seca nos animais em estresse térmico, enquanto que a relação concentrado:volumoso selecionada foi semelhante em ambos os tratamentos. Os parâmetros de fermentação ruminal mantiveram-se iguais em ambos os tratamentos. Entretanto, a digestibilidade da matéria seca e algumas de suas frações foram diminuídas nos animais estressados. Concluise que os animais mantidos sob estresse térmico reduziram a ingestão total de matéria seca, sem alterar a concentração de energia ou de fibra das suas dietas, provavelmente na tentativa de manter estável o ambiente ruminal.

The ability of cattle to select the roughage and concentrate in their diets under different environmental temperatures was studied in 12 cannulated cows, during 30 days. The experimental design was completely randomized with two treatments: thermal comfort (21oC) and thermal stress (climatic chamber, 38oC). Cows were fed a diet of sugar cane plus urea and concentrate mixture, which were offered separately and ad libitum. The ability of cows to select their diets was identified by comparing the composition of diet selected in different environments, as weel as ruminal parameters and diet digestibility. A significant decrease (p < 0.05) of 22% on total dry matter intake was observed in animals kept under heat stress compared to animals kept under comfort temperature, while concentrate:roughage ratio chosen was similar for both treatments. Ruminal parameters were equal for both treatments, while digestibility of dry matter and some of its fraction were reduced in stressed animals. Animals under heat stress decreased dry matter intake without changing dietary energy or fiber levels, probably attempting to maintain the stability of ruminal environment.

Assuntos