Observations on the effect of litter size, pregnancy nutrition
and fat genotype on ewe and foetal parameters
J.L. Owens, B. Kyle and P.F. Fennessy
Invermay Agricultural Centre, Ministry of Agriculture and
Fisheries, Mosgiel
Proceedings of the New Zealand Society of Animal Production.
1986, 46: 41-44
Fat and lean Coopworth ewes that were daughters of fat and lean
rams were joined with rams from the Invermay lean and fat selection
lines to study the effects of genotype (fat, lean) and mid-pregnancy
feeding level on foetal weight and ewe carcass measurements at day 135
of gestation. Ewes offered a high level of feed during days 30 to 100
of gestation gained 3% while those on a low level lost 9% of their day
30 live weight. All ewes were offered the same level of feeding from
day 100 until slaughter on day 135. Mid-pregnancy nutrition had no
effect on foetal weight. Litter size had significant effects on foetal
weight (single 4.56 kg, twin 3.99 kg, triplet 3.24 kg). The weight of
foetuses of the lean genotype adjusted for litter size and nutrition was
270g heavier (P<0.01) than that of the fat genotype. The weight of
placenta, and placentome number/foetus decreased with litter size and
were associated significantly with foetal weight. Fat genotype,
however, had no effect on placental weight or placentome number. Fat
genotype of the ewe and foetus did not affect a number of foetal
skeletal size parameters but influenced foetal weight despite ewe
nutrition. Consequently it appears that this influence on foetal weight
is independent on any effect of the placenta per se.
Keywords: NZSAPAB;
Lean; fat; foetal weight; pregnancy nutrition; placenta; sheep
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Last Updated 18-03-1997
