Response of ewes of Mediterranean sheep breeds to subcutaneous implants of melatonin
This study was done to examine whether pregnancy rates and prolificacy could be improved by treatment with melatonin before introduction of rams during seasonal anestrus. Three trials were conducted on four farms with a total of 481 ewes of three breeds, Rasa Aragonesa, Churra and Talaverana. Ewes isolated from rams since lambing were treated for 5 weeks with subcutaneous melatonin implants (Regulin®), or served as controls. Percentages of ewes with luteal activity at ram introduction did not differ between melatonin-treated and control groups (tested in Trial 1 and on Farm A in Trial 2). No differences were found in the mean interval from ram introduction to lambing or the distribution pattern of lambing. Significant differences in pregnancy rates were found only in Trial 1, 53% in treated vs. 38% in control ewes (P < 0.05). Rasa Aragonesa ewes which had lambed previously an average of 10 days earlier had a 19% higher pregnancy rate in Trial 1 (P < 0.01). Melatonin increased prolificacy only in Churra ewes (Trial 2, P < 0.10), by 0.24 on Farm A and 0.13 on Farm B. It is concluded that the potential of Spanish sheep to respond to supplementary melatonin varies in relation to breed, month and reproductive history. © 1991.
| Main Authors: | , |
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| Format: | journal article biblioteca |
| Language: | English |
| Published: |
Elsevier
1991
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| Subjects: | Melatonin implants, Reproduction, Sheep, |
| Online Access: | http://hdl.handle.net/20.500.12792/2440 http://hdl.handle.net/10261/293618 |
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