Growth of Heifers Fed 100 or 115% of National Research Council Requirements to 1 Year of Age and Then Changed to Another Treatment

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Abstract
Eighty-nine Holstein heifers were used from 3 mo of age until 21 d before their estimated calving date to determine the effect of two feeding programs on growth and onset of puberty. From 3 to 12 mo of age, heifers were fed either 100 or 115% of 1989 NRC nutrient requirements for heifers gaining .7 kg/d. At 12 mo, the treatments were switched (100 to 115% and 115 to 100%) until 21 d before calving. When the 115% diet was fed from 3 to 12 mo of age, rate of BW gain, BW at 12 mo, body condition score, and heart girth increased. Heifers fed the 115% diet from 3 to 12 mo of age were 22 d younger at onset of puberty than those fed the 100% diet, but BW at onset of puberty was similar (281 vs. 278 kg, respectively). When diets were switched at 12 mo of age, the rates of BW gain and growth for the heifers switched from 115 to 100% decreased, but rate of BW gain and growth increased for the other group. At 24 mo of age, BW and body size did not differ between treatments. Neither feeding program resulted in a clear advantage for any trait measured, but the results provide further evidence that extra nutrients fed beyond the NRC requirement for .7 kg/d of BW gain enhance various growth traits in Holstein heifers.