Evaluation of the Field Fertility Rate of Two Semen Extenders and a Novel Natural Approach using Cryptorchid Rams to Control Estral Activity in Sarda Sheep for Artificial Insemination

Artificial insemination (AI) is a key tool for genetic improvement in dairy sheep; however, its use in Sarda sheep remains limited due to variable fertility, management constraints, and reliance on hormonal estrus synchronization. This doctoral thesis aimed to evaluate practical and sustainable reproductive strategies to improve AI efficiency and reproductive management in Sarda sheep under field conditions. The thesis includes a general overview and three experimental studies. The first part reviews genetic, nutritional, managerial, and health-related factors affecting reproduction in Sarda sheep, with emphasis on AI and estrus control. The first experimental study assessed field fertility of Sarda ewes inseminated with semen diluted in skim milk or a commercial soy lecithin–based extender (OviXcell®) and stored at 15 °C. Fertility, lambing rate, prolificacy, and sex ratio were analyzed considering ram, ewe, farm, and year effects. Semen extender type significantly affected fertility outcomes. The second study investigated cryptorchidism in Sarda rams, evaluating incidence, testicular morphology, ultrasonography, seminal traits, endocrine profile, and sexual behavior. Despite severe alterations, cryptorchid rams retained behavior suitable for reproductive management. The third study evaluated cryptorchid rams as a natural, hormone-free method to induce the ram effect and synchronize estrus in ewes destined for AI. Cryptorchid rams effectively induced estrus and achieved acceptable reproductive performance. Overall, the results demonstrate that both optimized semen extenders and hormone-free reproductive strategies could represent feasible and sustainable approaches to improve artificial insemination programs in Sarda sheep, while enhancing animal welfare and reducing reliance on exogenous hormones.