Simulated impacts of new reproductive technologies on the
productivity of beef production systems
D.C. SMEATON
AgResearch, Private Bag 3123, Hamilton, New Zealand
E-Mail:
Proceedings of the New Zealand Society of Animal Production 2001. 61:
112-115
A computer simulation model was developed to explore how new
reproductive technologies could improve beef productivity through embryo
transfer (ET), sex ratio control and use of small cow breeds pregnant to
'high growth rate' calf genetics. Assumptions were made about conception
rates, embryo losses, sex ratios, cow and calf survival, animal weights,
and the feed requirements of small and large cows rearing large calves.
A range of pregnancy rates from ET (40 to 67%) were assumed compared to
natural mating (67%) and it was also assumed that a small cow breed,
such as a Jersey, could rear calves to similar weights of those from
Hereford x Friesian (H x F) cows. Cow efficiency values were derived as
the estimated intake of metabolisable energy by the cow plus calf unit
per year per kg of calf weaning weight. The model was based on averages
with variance information from fieldwork used for @Risk analyses. In the
model, H x F cows subjected to the new technologies such as ET
(involving synchronised calving) and sex ratio control were up to 9%
more efficient than the 'status quo' mating system. Using a small cow,
however, gave gains in efficiency of up to 20%. These benefits were
highly dependent on the assumptions used, in particular ET pregnancy
rate and cow and calf losses at calving, all of which, singly or
together, above threshold values, could destroy the gains or even create
losses in efficiency.
Keywords: NZSAPAB;
Small cow; large cow; Jersey; Hereford x Friesian; embryo
transfer; sex ratio; efficiency; weaning weight, feed intake
Last Updated 7/08/01
