Effects of nutrition and shearing during pregnancy on birth
weight in highly fecund Booroola-cross sheep
J. Orleans-Pobee, P.R. Beatson
Animal and Veterinary Sciences Group, Lincoln College,
Canterbury
Proceedings of the New Zealand Society of Animal Production.
1989, 49: 285-290
Effects of liveweight change during pregnancy and ewe shearing
on lamb birth weight were studied using highly fecund Booroola-Merino
cross Coopworth ewes. Following stratification on the basis of ewe live
weight (mean 53.7 kg), age, breed, condition score, and previous (187)
litter size, ewes were randomly allocated to a high (H) or low (L) early
pregnancy (0.-49 days) nutritional treatment. Ewes on treatments L and
H were offered sufficient feed to change their average live weight by 0
and 3 kg respectively between mating and 7 weeks post-mating. On the
basis of litter size estimated by ultrasound scanning on day 50 of
pregnancy, each of the 2 ewe groups was subdivided and allocated to one
of 2 mid-pregnancy nutritional treatments (h and L) designed to change
ewe body weight (live weight less conceptus weight) by 3 and 0 kg
respectively in 7 weeks. One hundred and nineteen days after mating,
half the ewes in each of the 4 nutritional subgroups were shorn and fed
to the estimated metabolisable energy (ME) requirement of unshorn ewes.
Lamb birth weights were recorded twice daily and within 12 hours of
birth for 221 lambs born to 102 ewes conceiving at synchronised oestrus.
High level of nutrition of ewes in early pregnancy increased birth
weight of lambs by 46 (±17) g/kg of live weight gained by ewes in the
first 7 weeks of pregnancy (P<0.05). Ewe liveweight change in mid-
pregnancy did not affect lamb birth weight (P>0.05).
In highly fecund sheep, lamb birth weight was affected by ewe liveweight
change in early pregnancy. Nutritional levels that cause a loss of ewe
live weight immediately after mating and up to 6 weeks of gestation are
detrimental to lamb birth weight.
Keywords: NZSAPAB;
Nutrition; ewe; sheep; fecundity; shearing; birth weight; live
weight; pregnancy
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Last Updated 18-03-1997
