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Natural Reproductive Management in Sarda Sheep: Use of Cryptorchids to Induce a Ram-Effect in Ewes Destined for Artificial Insemination
by
, , , , and
Charbel Nassif
1,*,
Laura Mara
2,
Fabrizio Chessa
2,
Marilia Gallus
2,
Federico Melis
2,
Ignazio Cossu
2
,
Antonello Ledda
1,
Antonello Cannas
1 and
Maria Dattena
2 1
Department of Agriculture, University of Sassari, 07100 Sassari, Italy
2
Department of Animal Science, Agricultural Research Agency of Sardinia, 07100 Sassari, Italy
*
Author to whom correspondence should be addressed.
Animals 2025, 15(23), 3444; https://doi.org/10.3390/ani15233444 (registering DOI)
Submission received: 28 October 2025
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Revised: 25 November 2025
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Accepted: 27 November 2025
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Published: 28 November 2025
(This article belongs to the Special Issue Recent Advances in Reproductive Biotechnologies—Second Edition)
Simple Summary
Farmers relying on hormones to induce estrus in ewes for artificial insemination (AI) spend a lot of money, and this raises welfare and consumer concerns. This study explored a hormone-free, natural way to synchronize reproduction in Sarda sheep using cryptorchid rams. These are naturally sterile males, due to undescended testes, who still show normal behavior toward females. To prove their efficiency, ewes were first kept away from any contact with rams and then exposed to cryptorchids. The results showed that these males successfully induced and synchronized estrus in most ewes, with conception and lambing rates comparable to traditional hormone-based methods. This approach offers a safe, hormone-free, cost-effective, and sustainable alternative for managing sheep reproduction and artificial insemination naturally, supporting both genetic progress and welfare-friendly farming practices.
Abstract
Cryptorchidism is a genital defect in which ram testicles fail to descend, causing azoospermia, while maintaining normal behavior towards females. We investigated whether cryptorchid rams can induce a ram-effect in ewes that would then be subjected to artificial insemination (AI). Therefore, ewes were isolated from any contact with rams for 6 weeks, then exposed to cryptorchid rams for 14 days. From day 15 to day 24, estrus was checked using a cryptorchid teaser four times daily (at 08:00, 12:00, 16:00, 20:00). Ewes detected in estrus were inseminated 24 h later. Experiment 1 included ewes (n = 31) all exposed to the cryptorchid ram-effect (CRE): 70.9% showed estrus, lambing rate after AI was 45.5%, and prolificacy was 1.40. Experiment 2 compared CRE (n = 80) with a control group with no prior exposure to males (n = 39). Estrus occurrence differed significantly (75.0% vs. 23.1%, respectively, p ≤ 0.001). Lambing rate from AI was 44.1% and prolificacy 1.27. These results show that cryptorchid rams effectively induce and synchronize estrus in Sarda ewes. AI fertility results on natural estrus following CRE yields outcomes comparable to those previously reported after hormonal synchronization for this breed.
