The influence of slowly and rapidly degradable concentrate protein on nitrogen balance, rumen fermentation pattern and blood parameters in dairy cattle.
AbstractIn a crossover trial, 4 cows were given concentrates containing rapidly and slowly degradable protein in combination with prewilted grass silage. Diets were given in 2 equal daily portions according to DCP and net energy requirements. The trial consisted of 3 main periods of 3 weeks each, with faeces, urine and milk collected and measured during the final week. On 1 day during this week samples of rumen fluid were taken and on 2 days blood samples were taken, directly before the morning feed and 1, 2, 3, 4 and 8 h later. N digestibity and N retention were the same on both rations. A concentrate with slowly-degradable protein resulted in a significantly higher rumen pH and acetate:propionate ratio. Ammonia concn. tended to be lower. Slowly-degradable concentrate protein led to a significantly higher concn. of urea and a lower concn. of insulin in blood. The concn. of several of the essential amino acids, and of the glucogenic amino acids and glycine was significantly lower. There were no significant effects of type of protein on milk yield or milk composition, but there was a tendency for these parameters to increase with ration containing slowly-degradable protein. Results suggest the ration containing slowly-degradable concentrate protein produced a more even rumen fermentation, which promoted a higher acetate:propionate ration in the rumen. On this ration there was a tendency for more gluconeogenesis from amino acids to occur. (Abstract retrieved from CAB Abstracts by CABI’s permission)