HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Sefidbakht, N. Articles by Farid, A. Search for Related Content PubMed PubMed Citation Articles by Sefidbakht, N. Articles by Farid, A.

Effect of Early Weaning and Hormone Treatments on Induction of Estrus, Conception and Lambing of Fall-Lambing Karakul Ewes^{1 ,2,}

Pahlavi University, Shiraz, Iran

Abstract

The effects of early weaning and exogenous hormones on postpartum estrus, conception and lambing performance were evaluated with 124 fall-lambed Karakul ewes. The broad outline of the experiment consisted of two lactation periods (nursing for 48 hr or 60 days postpartum) and four hormone treatment groups as follows: (1) a single injection of 2 mg estradiol-17ß on day 4 postpartum and on the same day a silicone rubber implant impregnated with 375 mg progesterone was implanted for 14 days, (2) same as (1) but 36 hr after withdrawal of implants a single injection of 700 IU PMS was given, (3) same as (2) but 16 days after the first injection of PMS another 700 IU PMS was injected, (4) untreated controls.

During the first 60 days after lambing, estrus was monitored by use of fertile rams. Neither suckling nor hormone treatment had significant effects on interval to first estrus in days (within 60 days postpartum) or percentage of ewes that exhibited estrus. Ewes in the early weaned group required an average of 189.3 days between lambings as compared with 193.7 days for ewes in the late weaned group (P<.05). Hormone treatments did not have a significant effect on the interval between lambings.

Percentage of ewes that lambed after experimental treatments was higher (P<.05) for the early weaned group as compared to the late weaned group (65 vs 48%). Early weaning also seemed to be associated with an increase (P<.05) in lambing percentage (78 vs 53%) and number of lambs weaned per ewe 60 days postpartum (.64 vs .35 lamb). The same trends also were found for weight of lambs born and weight of lambs weaned per ewe exposed to rams for 60 days postpartum.

Total number of lambs born per ewe over two lambing periods was higher (P<.05) in the early weaned group than in the late weaned group (1.82 vs 1.56). The same trends were observed for total weight of lambs born.

Total weight of lamb per ewe 60 days after lambing was higher (P<.05) in the late weaned group than in the early weaned group (22.92 vs 18.58 kg). This difference is attributed to the artificial rearing at the first lambing which increased mortality and stunted the growth of early weaned lambs. Hormone effects on different aspects of lamb production were not significant.

¹ This study was supported in part through a grant from Pahlavi University Central Research Fund; Agricultural Research Center and Ministry of Sciences and Higher Education.

² The authors would like to thank Dr. W. C. Foote for providing us required hormones and encouragement.

³ Present address: Texas A&M University Agricultural Research and Extension Center, San Angelo 76901.

⁴ Department of Animal Science.