Effect of dietary protein concentration and source on the growth rate and on body composition of Holstein-Friesian male calves

摘要: Holstein-Friesian male calves, aged 160 to 450 days, and of live weight 180 530 kg, were used determine the effects dietary nitrogen level source on performance. Experiment 1, tested level, involved two trials with three dietary-nitrogen levels equal metabolizable energy (ME) 11·7 MJ/kg dry matter (DM). The crude protein (CP) was reduced in course by 40 g/kg, experimental average CP diets being 146, 126 106 g/kg for high (HP), medium (MP) low (LP) diets, respectively. urea space (US) estimation body deposition rumen volume calculation empty measured trial A experiment 1. 2 four ME concentrations; (11-7 DM), which contents but from different sources: (a) 110 all it true (TP), negative control; (b) 130 TP; (с) CP, 20 is poultry litter (PL) protein; (d) PL protein. Significantly lower US ratio found calves LP diet, age 265 days than other diets. significantly decreased increasing treatments. Until 300 higher diet Calves HP had highest daily gain carcass gain. recommendation reduce as increased 120 caused a reduction retained not impaired. Protein impaired when below recommended National Research Council. inclusion concentration maintained, did rate live-weight gain, improved food conversion efficiency.