Growth of cattle in relation to nutrition in early life

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Abstract
Two experiments with monozygous twins showed that mature body weight of cattle can be modified by under-feeding the calf during the first 16 weeks after birth. Compensatory growth failed to make up the differences caused through retarded early growth by the time cf slaughter, at approximately 35 months of age in one experiment, and by 13 months of age in the other. Early nutritional treatments did not affect carcass composition. The effects of differential feeding on later live-weight growth were most evident when under-feeding lasted for 16 weeks after birth. Shorter periods of feed restriction, 8 and 4 weeks, also reduced later live weights but to a lesser absolute degree. Between animals within treatments the growth rates from 200 to 400 days of age, and from 200 to 550 days, were positively associated with the live weights recorded at 16 weeks of age in one experiment, but not significantly so in the other. High rank correlations of co-twins reared differently were recorded for live and carcass weights and carcass components. The results are discussed in the context of commercial beef production and the implications for central growth performance and progeny tests of beef animals in a genetic selection programme. Differential early rearing may seriously affect the evaluation of genetic merit when animals are brought together later in life for comparative growth testing, but when animals are reared together the level of rearing imposed may not markedly affect their performance ranking.