Effect of dietary crude protein concentration on milk productivity traits in early lactation dairy cows
Latvia University of Life sciences and Technologies, Faculty of Agriculture, Institute of Animal Sciences, Liela Street 2, LV-3001 Jelgava, Latvia
*Correspondence: diana.ruska@llu.lv
Abstract:
The evaluation and control of nitrogen balance at the farm and its relation to milk productivity traits are becoming essential in dairy farming. Increasing in milk productivity farmers tend to increase protein content in feed. The research complied into three (A, B, C) dairy cow groups (8 cows in each group) with LB and HM breed’s cows in the early lactation period divided into three phases (I, II, III) from 10 till 30 lactation days and lasting to 90 lactation days. Each group cows were feeders with total mixed ration (TMR) with different CP content (approx. 17.0%; 16.0%; 15.0% accordingly). The amount of feed consumed by each cow were recorded and feed samples collected during the study. Feed samples were analysed for CP and other feed quality descriptive traits. Milk yield ( kg d-1) and milk samples were collected at day 21 of each phase for analysis. Milk samples were analysed for fat (%), total protein (%), casein (%), and urea content (mg dL-1). The statistical analyses were conducted using ANOVA and descriptive parameters. To evaluate the feed CP conversion efficiency estimated part of that in the yield of milk protein for each cow and on average for the study group in each study phase. The conversion efficiencies of feed CP in milk were ranged from 28.5% to 40.7% in study phase I, and from 33.0% to 39.9% in phase II, and the differences were statistically significant. In phase III, the range from 30.4% to 36.3% were not statistically significant.
The objective of this study was to evaluation of feed protein conversion efficiency for dairy cows in the early lactation phase and define the optimal crude protein (CP) content in the feed.
Key words:
feed crude protein, milk total protein, milk urea, milk yield