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Milk production responses to pre- and postcalving dry matter Intake in grazing dairy cows
journal contributionposted on 2023-05-16, 18:19 authored by Roche, JR
Sixty-eight multiparous grazing dairy cows were randomly allocated to two precalving pasture allowances to achieve differential dry matter intakes (DMI) for 29 Â± 7.7Â d precalving (Low or High DMI; 4.8 or 11.9Â kg DM). At calving, cows within each precalving treatment were randomly allocated to one of two levels of feeding (Low or High DMI; 8.6 or 13.5Â kg DM) for 35Â d postcalving in a completely randomized design and a 2 Ã— 2 factorial arrangement of treatments. Following treatments all cows grazed together and were fed pasture and pasture silage. Daily milk yields were recorded, and fat, protein and lactose concentrations determined weekly for 15Â weeks. Blood was sampled weekly pre- and postcalving and analysed for indicators of energy status, growth hormone (GH) and insulin-like growth factor-1 (IGF-1). Body condition score (BCS) at calving was reduced by precalving restriction (P < 0.001; 2.8 and 3.0 for precalving Low and High treatment groups, respectively). Precalving restriction reduced milk fat production by 8.4% during the first 5Â weeks postcalving, but differences were not significant subsequently. Postcalving feed restriction reduced yield of fat corrected milk (FCM), fat and protein by 23, 21 and 28%, respectively, during the first 5Â weeks postcalving. Decreased (P < 0.05) yields of FCM, fat and protein (11, 10 and 9%, respectively) were also evident for 10Â weeks after the feed restriction finished. There was a tendency (P < 0.1) for a precalving Ã— postcalving DMI interaction in milk protein yield during the first 5Â weeks of lactation with no effect of precalving level of feeding in cows that were restricted postcalving. The plasma concentrations of non-esterified fatty acids (NEFA), Î²-hydroxybutyrate (BOH) and GH were elevated in restricted cows precalving, and IGF-1 concentration was reduced. Plasma NEFA and BOH concentrations were elevated postcalving in restricted cows, but no effect of postcalving DMI on GH or IGF-1 concentration was evident. Results suggest that under grazing systems milk production responses to precalving DMI are small, but energy restrictions in early lactations result in significant carryover effects in milk production. Â© 2006 Elsevier B.V. All rights reserved.
Publication titleLivestock Science
Department/SchoolTasmanian Institute of Agriculture (TIA)
Place of publicationNetherlands