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Consequences of low (mean 28.0 kg, n = 77) and high (mean 38.4 kg, n = 77) birthweight followed by slow (mean 548 g/day, n = 75) or rapid (mean 859 g/day, n = 79) growth to weaning for feedlot growth, intake and efficiency from 26 to 30 months of age were determined in Wagyu × Hereford (n = 81) and Piedmontese × Hereford (n = 73) cattle. Cattle were selected for study based on birthweight and preweaning growth rate, from multi-modal distributions achieved by imposition of low or high maternal nutrition during pregnancy and lactation, with the objective of achieving as close as possible to a 30% difference in birthweight and a 2-fold difference in preweaning growth rate between progeny groups. High birthweight cattle entered the intake test 57 kg heavier, grew 100 g/day more rapidly, and ate 1.0 kg dry matter /day more than the low birthweight cattle. The high birthweight cattle tended to have a higher feed conversion ratio than low birthweight cattle, but net feed intake did not differ due to birthweight group. Cattle grown rapidly to weaning entered the intake test 29 kg heavier, grew at an equivalent rate, and ate 0.7 kg dry matter/day more than the cattle grown slowly to weaning. No differences in feed conversion ratio or net feed intake were observed between the preweaning groups. When assessed at the same liveweight, differences in dry matter intake and/or feed conversion ratio due to birthweight or preweaning growth were no longer apparent. Interactions between prenatal and preweaning growth, or between sire genotype and early-life growth, were not evident for feedlot growth, intake or efficiency. It is concluded that severely restricted growth during prenatal life or from birth to weaning results in cattle that are smaller and consume less feed at the same age as their well grown counterparts; however, long-term effects of growth during early life on efficiency of utilisation of feed are not evident. |
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