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Reproductive performance of group-synchronized Merino d'Arles and Romanov crossbred ewes. 1. A note on the effects of lactation on fecundity

Published online by Cambridge University Press:  02 September 2010

F. J. Galindez ,
M. Prud'hon  and
G. Reboul
F. J. Galindez
Affiliation:
Station de Physiologie Animale, Institut National de la Recherche Agronomique, Place Viala, 34060 Montpellier-Cedex, France
M. Prud'hon
Affiliation:
Station de Physiologie Animale, Institut National de la Recherche Agronomique, Place Viala, 34060 Montpellier-Cedex, France
G. Reboul
Affiliation:
Station de Physiologie Animale, Institut National de la Recherche Agronomique, Place Viala, 34060 Montpellier-Cedex, France
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Summary

Fifty-six Merino d'Aries and 56 Romanov × Merino crossbred lactating ewes were divided into two treatment groups, one (T1) with a ewe-to-ram ratio of 48: 1 (24 Merino and 24 crossbred) and the other (T2) of 64: 1 (32 Merino and 32 crossbred).

Intravaginal sponges with 40 mg FGA (Searle) were inserted in two subgroups at 8-day intervals and withdrawn after 12 and 16 days in situ, in four equal groups at 4-day intervals. A dose of 400 IU pregnant mare's serum gonadotrophin (PMSG) was applied at sponge withdrawal.

Fertility after two oestrous cycles was equally satisfactory in both treatments, though it was lower in treatment group T2. This could be due to the significantly low (P<0·01) number of Merino ewes raddled by the T2 ram (0·33 Merino against 0·92 crossbred) suggesting preferential behaviour by the ram in this treatment.

Comparisons between breeds show a slight superiority in the fertility of crossbred ewes and a highly significant superiority in prolificacy These results suggest that using the described method, 2% of rams seems more than adequate to mate with progestagen-synchronized ewes with a satisfactory fertility level. It is, however, recommended to use homogeneous groups of ewes.

Type
Research Article
Information
Animal Production , Volume 24 , Issue 1 , February 1977 , pp. 113 - 116
Copyright
Copyright © British Society of Animal Science 1977

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References

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