Effects of genotype, liveweight, pasture type and feeding level
on ovulation responses in ewes
P.V. Rattray and K.T. Jagusch, J.F. Smith, G.W. Winn, K.S.
MacLean
Whatawhata Hill Country Research Centre, Hamilton and Ruakura
Agricultural Research Centre, Hamilton
Proceedings of the New Zealand Society of Animal Production.
1981, 41: 174-182
In a multifactorial experiment, groups (n=25/group) of
Coopworth, Commercial (C) Romney and Waihora (W) Romney ewes,
differentially fed over summer to achieve either high (H) or low (L)
pre-flushing weights (54-57 v 41-43 kg), were offered 3 levels of clover
or ryegrass dominant pasture for 6 weeks prior to a synchronised mating.
Pre-flushing weight and pasture type significantly influenced ovulation
rate. W Romney ewes responded differently from the other genotypes as
feeding level increased. Probability of a multiple ovulation was 0.62
and 0.75 for the L and H ewes; and 0.75 and 0.61 for the clover and
ryegrass pastures, respectively. For increasing feeding levels,
probabilities for the Coopworth were 0.34, 0.78 and 0.72; C Romney 0.48,
0.70 and 0.65; and W Romney 0.71, 0.76 and 0.88, respectively. By
inclusion of both pre-flushing and pre-mating weight in the model
probability contours were derived for each genotype.
Keywords: NZSAPAB;
Last Updated 12-09-1998
