The objective of this study was to determine if increasing the energy and protein intake of heifer calves would affect growth rates, age at puberty, age at calving and first lactation milk yield. A second objective was to perform an economic analysis of this feeding program using feed costs, number of nonproductive days and milk yield data.

Holstein heifer calves born at the Michigan State Dairy Cattle Teaching and Research Center were randomly assigned to one of two dietary treatments (n=40/treatment) that continued from 2 days of age until weaning at 42 days of age. The conventional diet consisted of a standard milk replacer [21.5 percent crude protein (CP), 21.5 percent fat] fed at 1.2 percent of body weight (BW) on a dry matter basis and starter grain (19.9 percent CP) to attain 0.45 kg of daily gain. The intensive diet consisted of a high-protein milk replacer (30.6 percent CP, 16.1 percent fat) fed at 2.1 percent of BW on a dry matter basis and starter grain (24.3 percent CP) to achieve 0.68 kg of daily gain.

Calves were gradually weaned from milk replacer by decreasing the amount offered for 5 and 12 days before weaning for the conventional and intensive diets, respectively. All calves were completely weaned at 42 daysof age and kept in hutches to monitor individual starter consumption in the early postweaning period.

Starting from 8 weeks of age, heifers on both treatments were fed and managed similarly for the duration of the study. Body weight and skeletal measurements were taken weekly until 8 weeks of age and once every 4 weeks thereafter until calving. Calves consuming the intensive diet were heavier, taller and wider at weaning. The difference in withers height and hip width was carried over into the early post-weaning period, but a BW difference was no longer evident by 12 weeks of age. Calves fed the intensive diet were younger and lighter at the onset of puberty. Heifers fed the high-energy and protein diet were 15 days younger at conception and 14 days younger at calving than heifers fed the conventional diet. Body weight after calving, daily gain during gestation, withers height at calving, body condition score at calving, calving difficulty score, and calf BW were not different. Energy-corrected, age-uncorrected 305-d milk yield was not different, averaging 9,778 kg and 10,069 kg for heifers fed the conventional and intensive diets, respectively. However, removing genetic variation in milk using parent average values as a covariate resulted in a tendency for greater milk from heifers fed the intensive diet. Preweaning costs were higher for heifers fed the intensive diet. However, total costs measured through first lactation were not different. Intensified feeding of calves can be used to decrease age at first calving without negatively affecting milk yield or economics.

Source: Journal of Dairy Science