Accelerated Growth and Early Breeding of Holstein Heifers

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Abstract
Holstein heifers (24) were fed grain and alfalfa hay ad lib for accelerated growth from 91 kg body wt until verification of pregnancy (Treatment A). Grain then was deleted until near time of freshening. They were bred at 2nd estrus if they weighed at least 305 kg. An additional 24 heifers were fed a conventional roughage ration to allow a growth rate corresponding to the Beltsville growth standard and were bred when 15-16 mo. of age (Treatment S). Observations were of growth rate, reproductive and productive performance, and length of herd life under normal culling. The A heifers gained 38% faster to 364 kg body wt (1.1 vs. 0.8 kg/day). Average weights and ages were 1st estrus 275 kg, 8.3 mo. (A), 288 kg, 10.2 mo. (S); 1st breeding 319 kg, 9.6 mo. (A), 392 kg, 16.8 mo. (S); and 1st calving 560 kg, 19.7 mo.(A), 26.9 mo. (S). Differences in body dimensions at given weights were negligible. Treatment effects on dystocia were inconclusive. Lactation number, numbers of animals milked 100+ days, and average milk yields (kg) were: 1st lactation 24, 4436 (A), 22, 5415 (S); 2nd-22, 5295 (A), 18, 5903 (S); 3rd-12, 6278 (A), 10, 6407 (S); 4th-6, 7181 (A), 5, 5269 (S). Mean accumulative milk yields per animal to 36 mo. of age were 7173 (A) and 4853 kg (S). Accelerated growth and early breeding did not affect herd life.