Feeding concentrate versus forage-based starter diets during early life to Holstein Friesian bull calves: growth, rumen fermentation, metabolic response, feed efficiency and beef production

The objective of this study was to compare the effect of artificially rearing Holstein Friesian bull calves with either forage- (FS) or concentrate-based starter diets on rumen fermentation and blood metabolite profiles to 4.5 mo, residual feed intake (RFI) at 10 mo, lifetime growth, and carcass traits and meat quality at slaughter in a pastoral grazing system. Holstein-Friesian bull calves were allocated to FS or PS diets (n = 20/group). The FS calves grew slower than PS calves following MR weaning up to 100 kg BW but tended to grow faster up to 18 wks while grazing pasture with no difference in BW observed thereafter. Rumen fermentation profiles differed at wk 7 and 12 but not thereafter. Residual feed intake (RFI), age and weight at slaughter and meat yield/quality were similar between groups. These results highlight that artificially reared Friesian bulls fed a FS compared to PS starter diet take slightly longer to reach 100 kg BW but are better prepared for weaning onto pasture, with no long-term differences in RFI, growth and beef production/quality. This study highlights the opportunity for beef producers to utilise a whole of life grain-free alternative feeding system to meet specific market requirements.