It has been suggested that United Kingdom recommendations for feeding the neonatal calf (,500 g milk replacer (MR)/day; ,200-230 g CP/kg milk powder) are inadequate to sustain optimal growth rates in early life. The current study was undertaken with 153 high genetic merit, male and female Holstein-Friesian calves (PIN 2000 5 £48) born between September and March, with heifers reared and bred to calve at 24 months of age. Calves were allocated to one of four pre-weaning dietary treatments arranged in a 2 MR feeding level (5 v. 10 l/day) 3 2 MR protein content (210 v. 270 g CP/kg dry matter (DM)) factorial design. MR was reconstituted at a rate of 120 g/l of water, throughout, and was offered via computerised automated milk feeders. Calves were introduced to pre-weaning diets at 5 days of age and weaned at day 56. During the first 56 days of life, calves offered 10 l MR/day had significantly higher liveweight gains ( P , 0.001) than calves fed 5 l MR/day. No significant differences in liveweight gain were found between calves fed 210 g CP/kg DM MR and those fed 270 g CP/kg DM MR from birth to day 56. Differences in live weight and body size due to feeding level disappeared by day 90. Neither MR feeding level nor MR CP content affected age at first service or age at successful service, and with no milk production effects, the results indicate no post-weaning benefits of increased nutrition during the milk-feeding period in dairy heifers.

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Sixty-five Holstein-Friesian calves were randomly allocated to one of eight nutritional treatments at 4 days of age. In this factorial design study, the treatments comprised of four levels of milk replacer (MR) mixed in 6 l of water (500, 750, 1000 and 1250 g/day) 3 two crude protein (CP) concentrations (230 and 270 g CP/kg dry matter (DM)). MR was fed via automatic teat feeders and concentrates were offered via automated dispensers during the pre-wean period. MR and calf starter concentrate intake were recorded until weaning with live weight and body measurements recorded throughout the rearing period until heifers entered the dairy herd at a targeted 24 months of age. There was no effect of MR protein concentration on concentrate or MR intake, and no effect on body size or live weight at any stage of development. During the pre-weaning period, for every 100 g increase in MR allowance, concentrate consumption was reduced by 39 g/day. While, for every 100 g increase in the amount of MR offered, live weight at days 28 and 270 increased by 0.76 and 2.61 kg, respectively (P , 0.05). Increasing MR feed levels increased (P , 0.05) heart girth and body condition score at recordings during the first year of life, but these effects disappeared thereafter. Increasing MR feeding level tended to reduce both age at first observed oestrus and age at first service but no significant effect on age at first calving was observed. Neither MR feeding level nor MR CP content affected post-calving live weight or subsequent milk production. Balance measurements conducted using 44 male calves during the pre-weaning period showed that increasing milk allowance increased energy and nitrogen (N) intake, diet DM digestibility, true N digestibility and the biological value of the dietary protein. Increasing the MR protein content had no significant effect on the apparent digestibility of N or DM.

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Results of a recent study (Wicks et al. 2005) indicate that increasing the protein content of the milk replacer fed to autumn-born Holstein-Friesian calves reduced growth rates in the first 8 weeks of life. Van Amburgh et al., (2001) previously suggested that increasing both milk replacer intake and protein content maximised the growth of calves during this early phase of life. An experiment was undertaken to investigate the influence of level of milk replacer and crude protein content on calf performance during the first 8 weeks of life of spring-born calves.