Tender, juicy and flavoursome are desirable meat traits in the grading system
of Meat Standards Australia. There are 3 critical growth phases affecting
these traits in domestic trade cattle: birth to weaning (phase I), weaning to
feedlot entry (phase II), and feedlot finishing (phase III). In the study
reported in this paper we examined the effects of supplementary feeding of
cows and/or calves in phase I on calf growth rate during each of the 3
growth phases and assessed whether differences in early growth were recorded
in carcass weights and meat quality at slaughter (16.5 months old). The calves
were weaned on to high quality pastures (phase II) and then finished in a
feedlot on a grain-based diet (phase III).
One-hundred Hereford cows with Angus-sired calves, and 24 Hereford cows, with
Hereford-sired calves were allocated to treatments in a 2 × 3
factorial study of calf growth rate during phase I. The treatments consisted
of nil or 4.2 kg twice-a-week of cottonseed meal to the cows for 145 days from
calving to mid-lactation, and calves either had access to a high protein
barley-based supplement in a ‘creep’ from 75, or from 150 days old
until weaning. There were 4 replicate groups for each treatment during phase I
with 24 paddocks. Weaners were grazed as a single herd during phase II of the
study and separated into 10 feedlot pens in phase III. At slaughter, after
phase III, M. longissimus et laborum muscle was sampled
from half the carcasses and graded by a taste panel according to Meat
Standards Australia.
Calves, suckled by cottonseed meal-supplemented cows, were heavier at weaning
than those calves suckled by non-supplemented cows (201
v. 170 kg; phase I) with a trend for younger calves with
access to ‘creep’ feeding (from 75 days old) to be heavier than
calves without access to ‘creep’ feed (196
v. 175 kg). During phase II, liveweight change was
higher for weaners from non-supplemented cows than for weaners from
supplemented cows (679 v. 593 g/day). During phase
III this trend was reversed in favour of weaners from cottonseed
meal-supplemented cows (1.54 v. 1.46 kg/day).
Similarly, carcasses of calves from cottonseed meal-supplemented cows were
also heavier than other carcasses from other calves (226
v. 212 kg) with a greater depth of rib fat (7.0
v. 5.8 mm). In contrast to carcass weight,
M. longissimus et laborum muscle samples from calves
which did not have access to supplement during phase I were assessed as being
more tender, more flavoursome and having a higher overall Meat Standards
Australia score than M. longissimus et laborum muscle
from calves that had access to supplements. The carryover effects of nutrition
from the preweaning growth phase of calves highlight the importance of early
life nutrition for achieving higher carcass weights and meat quality. However,
the findings that M. longissimus et laborum samples from
calves with lower growth rates before weaning were more tender and graded
higher than samples from calves with higher growth rates was both unexpected
and unexplained.
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