Growth and lactation performance of dairy heifers raised in confinement or on pasture

Raising heifers on pasture may be a strategy for reducing economic cost of heifer rearing. However, few studies have compared heifers raised in confinement versus on pasture and their long-term effects on first lactation performance. Therefore, the objective of this study was to evaluate the impact of raising dairy heifers on pasture or in confinement on their first lactation performance, as well as to conduct an economic evaluation of each system. Thirty-six Holstein heifers were raised under 2 contrasting strategies (treatments): (1) 18 heifers were rotationally stocked on cool-season grass pastures during the grazing season, or (2) 18 heifers were housed and fed under confinement management. During winters, all heifers were housed in confinement and fed similar diets. Initial and final BW and BCS as well as ADG were recorded throughout the study. During the winter period, prepartum, and lactation, animals were fed and managed under similar conditions. Milk yield and composition (i.e., total fat and total protein), DMI, and BW were recorded through lactation (at 50, 100, 150, and 200 DIM). Income over feed cost (IOFC) was calculated to evaluate potential economic differences between the 2 treatments. The ADG and final BW were both lower for heifers raised on pasture (-0.11 kg/d and -20 kg, respectively), compared with confinement heifers. In the winter, no differences in BCS, final BW, and ADG were detected through the winter. In the second grazing season, BW, BCS, and ADG did not differ between treatments. On performance during the cow's first lactation, pasture-raised heifers produced 3.40, 3.90, 4.10, and 6.30 kg/d of milk and 4.60, 4.30, 4.80, and 7.60 kg/d of ECM greater than confinement-raised heifers at 50, 100, 150, and 200 DIM, respectively. The greater milk production resulted in greater IOFC for pasture-raised heifers than in the confinement-raised heifers at 50, 100, 150, and 200 DIM (US$+1.13, US$+1.59, US$+1.81, and US$+2.53, respectively). At the end of the first lactation, pasture-raised heifers produced 1,230 kg more milk and 79.3 kg more milk protein than confinement-raised heifers. Therefore, heifers raised on pasture and supplemented to support the recommended growth for dairy heifers demonstrated similar growth, lower feed cost, and improved performance during first lactation, compared with heifers raised in confinement, resulting in more milk production and greater DMI capacity.