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摘要
Background: Ammonia nitrogen (N) in alfalfa silage is used to evaluate silage quality, but its eff ect on dairy cows production is unknown. Objective: A meta-analysis was conducted to assess the eff ects of ammonia-N concentration in alfalfa silage on dairy cow performance. Methods: Thirty-four comparisons from 10 studies were analyzed with linear and quadratic models by the mixed-eff ect models of the R program using study as a random eff ect. The variance explained by the models was evaluated calculating marginal R-2 (m) and conditional R-2 ((c)). Results: Dry matter intake declined (DMI; p = 0.007), and milk production and milk fat yield tended to decrease linearly in response to increasing ammonia-N concentration (p = 0.08). Milk fat and milk protein percentages were unaff ected. Milk protein yield, however, showed a positive linear trend eff ect (p = 0.07) along with a signifi cant quadratic eff ect (p = 0.01) in response to increasing ammonia-N concentration. Values of R-2 ((m)) and R-2 ((c)) indicated less variation for signifi cant models. Conclusion: Increased ammonia-N in alfalfa silage reduced DMI, negatively impacting milk production and milk fat yield. The quadratic response in milk protein yield might be explained by the initial reduction in milk production, and the subsequent utilization of ammonia-N to produce more rumen microbial protein, which results in more milk protein.
- 出版日期2017-9
