Effect of feeding of different sources of NPN on production performance of dairy cows

Abstract

The aim of the study was to analyse the effect of feeding of different sources of NPN on nutrient utilization and production performance of dairy cows under field conditions. Balancing diets for crude protein without consideration of protein quality or rumen degradability often led to overfeeding of nitrogen and less than optimum production. High yielding dairy cows separated in two groups with 85 resp. 80 cows in each were set up for the trial. Groups were consistent according the stage of production and reproduction cycle as well as age structure. Both groups were fed concentrate mixture with the same composition with only difference in NPN/microbial protein source, with same dosage of 100 g per cow and day. Field trial was performed for period of 3 subsequent months. Performance data were collected in accordance with official milk recording. In both groups majority of cows were on first lactation. Significant differences in daily milk production were observed 2.87 kg (P<0.01) for group 2, in fat content 0.07% for group 2 non-significant, whereas in protein content 0.18% for group 1 significant (P<0.01) in case of first lactations. If considering first tree lactations, group 2 produced 1.7 kg milk per day more (P<0.08), with 0.05% fat more and 0.002% protein less than group 1. The space created in dry matter intake by a concentrated slow-release NPN can be filled with high quality forage that could reduce the cost of feeding while maintaining levels of production.