Efeito da suplementação com uma cultura de Saccharomyces cerevisiae na degradação in situ de forragens em vacas alimentadas com uma dieta com elevada participação de alimento concentrado
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2017
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Nas últimas décadas, para dar resposta ao aumento produtivo dos animais ruminantes
criados em sistemas de produção intensiva, a componente forragem da dieta tem sido
progressivamente substituída por níveis crescentes de alimentos concentrados. O elevado
teor em hidratos de carbono muito fermentescíveis, o baixo teor em fibra e partículas de
tamanho reduzido, são fatores que tendem a elevar digestibilidade da dieta, mas a prevalência
de distúrbios digestivos tem tendência a aumentar. A utilização de aditivos na alimentação
animal, como por exemplo a Saccharomyces cerevisiae (SC), ganhou assim maior interesse,
passando a ser um desafio importante para a nutrição animal conhecer ao certo os seus
efeitos no trato digestivo do animal, quais os mecanismos pelos quais influenciam não só a
eficiência digestiva, mas também a saúde e bem-estar do animal. O trabalho experimental
realizado no âmbito desta tese incidiu sobre os efeitos da adição de uma cultura comercial de
leveduras vivas SC nos parâmetros de fermentação no rúmen e na degradação da fração fibra
do detergente neutro de 10 amostras de silagens de milho conservadas com origem em vários
países. O estudo envolveu quatro vacas da raça Holstein Frísia, não lactantes, multíparas,
com peso inicial de 665 ± 56 kg, fistuladas no rúmen. A dieta, constituída por 25 kg de silagem
de milho e 10,2 kg de alimento concentrado (50:50 na MS), era fornecida duas vezes por dia.
Os animais receberam esta dieta (dieta controlo, sem levedura, tratamento LEV-) e,
posteriormente, a mesma dieta suplementada com 0,5g de uma cultura de leveduras vivas
SC, contendo 2x1010 UFC/g (tratamento LEV+). Cada período experimental compreendeu 21
dias de adaptação. As amostras de silagens foram incubadas no rúmen, durante 12, 24 e 36
h. Foram recolhidas amostras de fluído ruminal às 0, 2, 4 e 8 h após a refeição da manhã,
sendo lido de imediato o pH. Posteriormente estas foram analisadas e determinado o teor em
azoto amoniacal (N-NH3), lactato e o perfil em ácidos gordos voláteis (AGV). Concluiu-se que
não ocorreu qualquer efeito da incorporação diária de SC na dieta no pH e na concentração
de lactato (P>0,05). No entanto, houve uma tendência para a concentração de lactato ser
superior na dieta com adição de levedura (P=0,13). Relativamente aos AGV totais, os
resultados não foram significativamente afetados pela dieta (P>0,1) e, individualmente, houve
efeito da suplementação com SC (P<0,05) apenas no acetato. Constatou-se que o efeito do
tempo de recolha foi significativo (P<0,0001) para todos os AGV analisados. O teor em N-NH3
variou significativamente com a dieta (P<0,01) e com o tempo de recolha (P<0,0001). Embora
a inclusão de levedura na dieta não tenha tido efeito significativo (P>0,05) na degradação da
fração NDF das silagens após 12 e 24 h de incubação, foi observada uma redução significativa
após 36 h. Na generalidade dos resultados, constatou-se que a suplementação com SC não teve efeito nos parâmetros de fermentação ruminais nem na degradação da fração NDF das
silagens estudadas.
In the last decades, in order to respond to the productive increase of ruminant animals in intensive production systems, the forage component of the diet has been progressively replaced by increasing levels of concentrated feed. The high content of very fermentable carbohydrates, low fiber content and small particles are factors that tend to increase diet digestibility, but the prevalence of digestive disorders tends to increase. The use of additives in animal nutrition, such as Saccharomyces cerevisae (SC), has gained greater interest, becoming a major challenge for animal nutrition to know its effects in the digestive tract of the animal, what mechanisms Influence not only the digestive efficiency, but also the health and well-being of the animal. The main aim of this work was the evaluation of the performance of a commercial product containing a preparation of SC in rumen fermentation and degradation of the NDF fraction (in sacco) of ten maize silages from different countries. Four dairy cows (Holstein Friesian), non-lactating, multiparous, with an initial weight of 665 ± 56 kg and with a rumen cannula took part in this study. The diet was based on 25 kg of maize silage and 10.2 kg of concentrated feed (50:50 on dry matter) was supplied twice a day. During the experimental period, the diet established in the experimental adaptation was used (LEV-) followed by the same diet but supplemented with 0.5 g/day of a culture of live yeast SC containing 2 x1010 CFU/g (LEV-). Each experimental period included 21 days of adaptation. Feed samples were incubated in the rumen during 12, 24 and 36 h. Samples of rumen fluid were collected, during two non-consecutive periods, at 0, 2, 4 and 8 h after the morning meal. After pH measure, samples were used to determine ammonia nitrogen (N-NH3) and lactate and the volatile fatty acids (VFA) by chromatography. In conclusion, there was no effect of the daily incorporation of SC in the diet at pH and lactate concentration (P > 0.05). However, there was a tendency for the lactate concentration to be higher in the diet with addition of yeast (P = 0.13). Regarding total VFA, the results were not significantly affected by diet (P > 0.1) and, individually, there was effect of supplementation with SC (P < 0.05) only on acetate. It was found that the effect of the collection time was significant (P < 0.0001) for all the AGVs analysed. The N-NH3 content varied significantly with the diet (P < 0.01) and the time of collection (P < 0.0001). Although the inclusion of yeast in the diet did not have a significant effect (P > 0.05) on the degradation of the NDF fraction of the silages after 12 and 24 h of incubation, a significant reduction was observed after 36 h. In general, SC supplementation had no effect on ruminal fermentation parameters or degradation of the NDF fraction of the studied silages.
In the last decades, in order to respond to the productive increase of ruminant animals in intensive production systems, the forage component of the diet has been progressively replaced by increasing levels of concentrated feed. The high content of very fermentable carbohydrates, low fiber content and small particles are factors that tend to increase diet digestibility, but the prevalence of digestive disorders tends to increase. The use of additives in animal nutrition, such as Saccharomyces cerevisae (SC), has gained greater interest, becoming a major challenge for animal nutrition to know its effects in the digestive tract of the animal, what mechanisms Influence not only the digestive efficiency, but also the health and well-being of the animal. The main aim of this work was the evaluation of the performance of a commercial product containing a preparation of SC in rumen fermentation and degradation of the NDF fraction (in sacco) of ten maize silages from different countries. Four dairy cows (Holstein Friesian), non-lactating, multiparous, with an initial weight of 665 ± 56 kg and with a rumen cannula took part in this study. The diet was based on 25 kg of maize silage and 10.2 kg of concentrated feed (50:50 on dry matter) was supplied twice a day. During the experimental period, the diet established in the experimental adaptation was used (LEV-) followed by the same diet but supplemented with 0.5 g/day of a culture of live yeast SC containing 2 x1010 CFU/g (LEV-). Each experimental period included 21 days of adaptation. Feed samples were incubated in the rumen during 12, 24 and 36 h. Samples of rumen fluid were collected, during two non-consecutive periods, at 0, 2, 4 and 8 h after the morning meal. After pH measure, samples were used to determine ammonia nitrogen (N-NH3) and lactate and the volatile fatty acids (VFA) by chromatography. In conclusion, there was no effect of the daily incorporation of SC in the diet at pH and lactate concentration (P > 0.05). However, there was a tendency for the lactate concentration to be higher in the diet with addition of yeast (P = 0.13). Regarding total VFA, the results were not significantly affected by diet (P > 0.1) and, individually, there was effect of supplementation with SC (P < 0.05) only on acetate. It was found that the effect of the collection time was significant (P < 0.0001) for all the AGVs analysed. The N-NH3 content varied significantly with the diet (P < 0.01) and the time of collection (P < 0.0001). Although the inclusion of yeast in the diet did not have a significant effect (P > 0.05) on the degradation of the NDF fraction of the silages after 12 and 24 h of incubation, a significant reduction was observed after 36 h. In general, SC supplementation had no effect on ruminal fermentation parameters or degradation of the NDF fraction of the studied silages.
Descrição
Dissertação de Mestrado em Engenharia Zootécnica
Palavras-chave
Vaca leiteira , Aditivo alimentar , Saccharomyces cerevisiae , Silagens de milho , in sacco , Fibra em detergente ácido