New Zealand Journal of Agricultural Research abstracts
Optimum liveweight, feed intake, reproduction, and calf output in beef cows on
North Island hill country, New Zealand
D. C. SMEATON
M. D. BOWN
J. B. CLAYTON
AgResearch
Ruakura Research Centre
Private Bag 3123
Hamilton, New Zealand
Abstract Hereford x Friesian beef cows were managed on one of
five lifetime liveweight profiles with the relative differences maintained
throughout the 4-year period of the project. The objective was to determine
optimum beef-cow liveweight profiles for use by farmers. In the first year, 115
in-calf heifers entered the trial in January 1991 at age 18 months. This
process was repeated annually to replace culled and empty cows so that in the
second, third, and fourth years there were 139, 152, and 144 cows,
respectively, on the trial with 4 age classes on the trial in the fourth year.
Four times each year (pre-calving, early lactation, mid lactation, and post
weaning) dry matter intake by the cows was estimated using slow release chromic
oxide capsules, faecal grab sampling, and estimates of in vitro
digestibility of pasture samples. The cows and their calves were weighed every
4 to 6 weeks, and the calves were weaned at about 180 days when they left the
trial. During most of the trial, mean cow liveweight spanned a range from 350
to 500 kg. The profiles were significantly different, as were their effects on
cow condition score, cow pasture intake, calf liveweights, and, sometimes, cow
reproduction. For every kg extra that the cows were heavier, dry matter intake
increased by 15 to 60 g d-1 depending on physiological status. When
cow mating weight was fitted in regressions against cow reproductive items,
optimum cow liveweight was estimated to be 440 kg with very little change in
output over the range 420 to 450 kg liveweight. Calf growth rate showed a
linear response of 1.2 g additional daily gain per kg increase in cow mating
weight. Over 180 days from birth to weaning, this amounted to 0.22 kg extra
calf weaning weight per kg of cow mating weight.
Keywords beef cows; optimum liveweight; feed intake; calf;
reproduction
New Zealand Journal of Agricultural Research, 2000, Vol. 43: 71-82
0028-8233/00/4301-0071 $7.00/0 (c) The Royal Society of New Zealand
2000
PDF file of entire paper: medium quality (874K); (scanned from paper original: notes about this process)
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