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

Replacement heifers are important in the dairy herd because they are the next generation lactating cows, but the costs to raise them is a major expense. This implies that dairy farms must find ways to balance between supporting satisfactory growth, while also minimizing the costs associated with raising heifers. Thus, various feeding and management strategies are aimed to decrease production costs without negatively impacting the future productive life of the heifer. Mostly, heifers are raised indoors for many reasons, including improved monitoring and implementation of precise feeding regimes that will optimize feed efficiency as well as reduce nutrient excretion, but the rearing cost is a major expense, second only to feed cost. This implies that dairy farms must explore ways to balance between supporting satisfactory growth while also minimizing the associated costs. Although satisfactory results are obtained raising heifers indoors, harvesting, processing and transporting feed sources to heifers in confinement increases rearing cost.

Raising heifers on pastures offers a viable alternative to reduce feed cost, and it provides additional benefits: From an animal welfare perspective, pasture accessibility may reduce health issues such as lameness and tarsal joint lesions in cattle, which may increase longevity of the cows in the herd. From an ecological perspective, pasture areas are important for water storage capacity, nutrient cycling, and carbon sequestration, which directly impact overall sustainability. 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 the study cited 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 two 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 body weight (BW) and body condition score (BCS) as well as average daily gain (ADG) were recorded throughout the study. During the winter period, pre-calving, and lactation, the heifers were fed and managed under similar conditions. Milk yield and composition (i.e., total fat and total protein), dry matter intake (DMI), and BW were recorded through lactation [at 50, 100, 150, and 200 days in milk (DIM)]. Income over feed cost (IOFC) was calculated to evaluate potential economic differences between the two treatments.

The ADG and final BW were both lower for heifers raised on pasture (−0.11 kg/day 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, the pasture-raised heifers produced 3.40, 3.90, 4.10, and 6.30 kg/day of milk and 4.60, 4.30, 4.80, and 7.60 kg/day 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 their first lactation, compared with heifers raised in confinement, resulting in more milk production and greater DMI capacity.

Comment: Although the confinement system is not typical in South Africa, the pasture system showed interesting compensatory benefits in the first lactation period, which may be associated with improved health issues compared to confinement.