Milk-fed calves: 1. The effect of milk intake upon the herbage intake and performance of grazing calves

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Abstract
SUMMARY: Two trials were conducted, using 18 and 30 castrated male calves respectively, to investigate the importance of milk in the diet of calves during the first 8 months of life and its effect on herbage intake and live-weight change. Reconstituted milk substitute was fed in a manner that simulated the supply of milk for lactation, yields of 2101, 1635 and 1165 kg (Expt 1) and 1906, 1609, 1304, 1005 and 701 kg (Expt 2) over a 240-day period. Calves were purchased in mid-February, when approximately 1 week old, and housed individually until turned out to graze at 10 weeks of age. At pasture, the calves were strip grazed on swards of Lolium perenne cv. S. 23 or S. 24 and given a daily herbage allowance of 60 g D.m./kg live weight.The live-weight gain response to milk consumption was 81 g/kg milk fed during the housed period and 50 g during the grazing season. Herbage and milk intake per unit live weight were inversely related but because the grazing season responses were confounded with the treatments during the housed periods, it was not possible to determine true replacement rates. Herbage intake per head increased with time but there was no general trend when intake was expressed per unit live weight.