|Rexroad Jr, Caird|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/1997
Publication Date: N/A
Citation: N/A Interpretive Summary: This experiment was based on extensive research with the larger Danish cattle produced maximum milk in first lactation when they had daily gains of 600 grams at body weights from either 100 or 150 up to 300 kilograms. Raising these same heifers at daily gains of 900 grams for this same period of body weight reduced milk production to 80% of the maximum. We raised 75 Holstein heifers from 175 to 325 kilograms of body weight at intended daily gains of 725 or 950 grams using diets based on either alfalfa silage or corn silage plus soybean meal. The alfalfa silage diet contained more digestible protein and less digestible energy than the corn silage plus soybean meal diet but both diets were adequate in energy and protein. Low gain on alfalfa was 793 and high gain on alfalfa was 992 grams per day. Low gain on corn silage was 776 and high gain on corn silage was 997 grams per day. From the end of the experimental growth until calving all heifers were on the same diet; those previously raised for low gain grew enough to eliminate any differences with an average body weight of 508 kilograms after calving. A single total mixed ration, which contained 17.1% crude protein and 3.12 megacalories of digestible energy per kilogram of dry matter, was fed during lactation. Neither feed intake, milk production, milk component production, nor milk composition were affected by either experimental diet or experimental growth rate. This lack of an effect on milk production is consistant with six other studies on US Holesteins.
Technical Abstract: Seventy five prepubertal heifers were fed diets based on either alfalfa silage or corn silage plus soybean meal for daily gains of either 725 or 950 g/d in a 2 2 factorial from 175 to 325 kg of body weight (BW). The alfalfa diet contained more digestible protein and less digestible energy than the corn silage plus soybean meal diet. Actual gains were: pre-experimental, 633; experimental low, 785; experimental high, 994; post-experimental low, 546 and post-experimental high, 494 g/d. Compensatory post- experimental gains on a common diet allowed calving age at 732 d, post-calving BW at 508 kg and pre-calving height at 134 cm. A total mixed ration containing 17.1% CP and digestable energy at 3.12 Mcal/kg of dry matter was fed during lactation. Feed intake, milk or milk component production, and milk composition were not affected by either experimental diet or growth rate. Milk production was related to age of calving and was more strongly related to BW after calving as covariates but no differences occurred during growth treatments. Differences in protein and energy concentrations in experimental growth diets did not affect lactation performance. About 75% of gains of 776 to 997 g/d from 180 to 330 kg of BW occurred before puberty but they did not affect milk production. This lack of an effect of our prepubertal growth rates on primaparous milk production is consistat with six other similar recent studies.