Effect of concentrate feed level in late gestation on subsequent milk yield, milk composition, and fertility of dairy cows

The effects of level of concentrate feeding in late gestation on feed intak e, milk yield, milk composition, and fertility in the subsequent lactation were evaluated in a randomized block design experiment involving 60 cows. G rass silage was offered ad libitum for the last 28 d of gestation either as the sole diet (OC) or supplemented with 5 kg/d of concentrates (5C). Follo wing calving, the cows were offered the same grass silages supplemented wit h 7 kg/d ofconcentrates. For treatments OC and 5C, total dry matter intakes were 9.28 and 11.03 kg/d of dry matter, respectively, during the last 4 wk of gestation. During wk 1 to 12 of the subsequent lactation, treatment 5C increased milk fat concentration but did not alter feed intake, milk yield, or protein concentration relative to treatment OC. Treatment 5C increased the interval to first progesterone rise and the number of services per conc eption relative to treatment OC. Cow parity, BF depth assessed at d 28 befo re parturition, and treatment provided the best fit relationships for the y ields of fat and fat plus protein (R-2 relationships = 0.65 and 0.64, respe ctively) during wk 1 to 4 of lactation. It was concluded that, other than m ilk fat concentration, supplementation with additional concentrates in late gestation did not alter milk yield or composition and dairy cow fertility. Furthermore, despite the very large differences in cow characteristics at d 28 before parturition, there was no evidence of any interaction between t reatment and specific cow characteristics on animal performance in the firs t 12 wk of lactation.