An example of reproduction management in organic sheep farming

Abstract

Sheep artificial insemination (AI) programs use hormonal treatments to synchronize ovarian cycles and ovulation, but these methods cannot be used on organic farms, limiting potential genetic improvement. This work reports the use of AI during a 3 year period (2008-2010) on an organic Sardinian sheep farm (40 °44’6” N) using controlled reproduction management without hormonal treatment. Every year 60 Sarda sheep were isolated from the males at the end of March for 6 weeks. Each animal had daily access to natural pasture and 450-600 gr of concentrate. Five teaser rams were introduced in the flock during the second week of May (Day 0) to induce synchronization and ovulation, and were left there until the start of the presumptive first oestrus (Day 17th). From day 15 to 25, ewes were checked for oestrus 4 times a day (8:00 AM; 12:00 PM; 4:00 PM; 8:00 PM) using teaser rams. The females in heat detected at 12:00 PM; 4:00 PM; 8:00 PM were inseminated by cervical AI 24 h after oestrus detection with fresh semen chilled to 15 °C (400 million spermatozoa/ dose). The percentage of females in heat between day 15 and 25 was calculated for each of the three years. Lambing and prolificacy rates were calculated for years 2008, 2009 and 2010. Throughout the 3 years, 83% of the females were detected in heat. The fertility rate of the 125 artificially inseminated animals was 46.4%. The prolificacy rate of the 58 ewes that lambed was 129.3%. These data show that alternative reproduction management might achieve results comparable to more traditional reproduction programs in Sarda breed.