Estimation of milk consumption in beef calves using a tritiated water dilution technique

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Abstract
The milk intake of crossbred and Angus calves in the first 6 weeks of life was estimated from their water turnovers measured using tritiated water (TOH) dilution. Corrections were made for increase in TOH space occurring during the periods of measurement. The corrections were smaller than those noted in lambs at a similar stage of life, and there were no consistent differences between breeds or weeks. In crossbred calves, estimated milk intake rose (P < 0.05) from 8.65 1 day-1 in week 1 to 11.21 l day-1 in week 6. The corresponding intakes for Angus calves were 6.31 and 10.02 l day-1 but the difference between breeds was not significant. Liveweight gains ranged from 659 to 1170 g day-1 for crossbred calves and from 532 to 925 g day-1 in Angus calves. Total liveweight gain and dryweight gain were closely related to total milk intake (r= 0.94, P < 0.001, and r= 0.85, P < 0.01, respectively). Dryweight gain was also closely related to dry matter intake (r= 0.85, P < 0.01). Estimated milk intakes are compared with those previously reported, and it is concluded that, provided changes in pool size are taken into account, the TOH dilution technique is well suited to the estimation of milk intake in beef calves. It is suggested that, in converting water turnovers into milk intakes, an assumed factor of 0.96 would save time and effort, and involve little error.