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Effect of level of food intake at mating on the reproductive performance of ewes passively immunized against testosterone

Published online by Cambridge University Press:  02 September 2010

S. M. Rhind ,
B. A. Morris ,
Jill Clayton  and
G. Gittus
S. M. Rhind
Affiliation:
Hill Farming Research Organisation, Bush Estate, Penicuik, Midlothian EH26 0PY†
B. A. Morris
Affiliation:
Division of Clinical Biochemistry, University of Surrey, Guildford GU2 5XH
Jill Clayton
Affiliation:
Division of Clinical Biochemistry, University of Surrey, Guildford GU2 5XH
G. Gittus
Affiliation:
Hill Farming Research Organisation, Bush Estate, Penicuik, Midlothian EH26 0PY†
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Abstract

In a 2 × 2 × 2 experiment, 296 Scottish Blackface ewes were fed to achieve one of two levels of body condition (high: condition scores ^2·75; low: condition scores ^2·50) by 2 weeks before joining with rams. Half of the ewes of each condition score were fed dried grass pellets ad libitum and 300 g hay per head daily, between 2 weeks before and 8 days after joining, while the remaining ewes were offered a live-weight maintenance ration comprising 750 g pellets and 400 g hay per head daily. From 8 days after joining the intake of all ewes was gradually changed, over a 2-week period, to 1250 g pellets and 400 g hay per head daily. Two days before joining, half of the ewes of each condition/intake group were passively immunized against testosterone. A total of 99 ewes were slaughtered 18 days after joining and their ovulation rate at the first mating determined. Ovulation rates were significantly affected by immunization (immunized: 2·31, control: 1·86, pooled s.e. = 0·055; P < 0·01) and food intake (ad libitum: 2·24, maintenance: I 92, pooled s.e. = 0·055; P < 0·05) but not by body condition at mating (high: 2·15, low: 2·02, pooled s.e. = 0·059; P > 0·05). Lambing rates were dependent on treatment (immunized: 1·82 control: 1·62, pooled s.e. = 0·044; P < 0·01), food intake (ad libitum: 1·85, maintenance: 1·59, pooled s.e. = 0·043; P < 0·01) and body condition (high: 1·82, low: 1·62, pooled s.e. = 0·044; P < 001). In ewes in a high body condition at mating, the effects of intake and immunization were additive but in ewes in low condition, immunization induced little improvement in performance in ewes fed ad libitum. Circulating antibody titres were lower in ewes fed ad libitum than in ewes offered a maintenance ration (1: 416 v. 1: 534, pooled s.e. = 14; P < 0·001), but ovulation rates and litter sizes were not related to titres.

Type
Research Article
Information
Animal Production , Volume 45 , Issue 1 , August 1987 , pp. 81 - 85
Copyright
Copyright © British Society of Animal Science 1987

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References

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