Variable reproductive performance of rams

Researchers in Wyoming and Utah evaluated the reproductive performance of rams in three producer range flocks. Rams were classified as either low or high performers, based on the number of offspring sired. The number of lambs expected to be sired by each ram was determined and based on the expectation that each ram would sire the same number of offspring.

Prior to being joined with ewes, rams underwent a breeding soundness exam. DNA was extracted from blood samples collected from each ram and from approximately one-third of the lambs and their dams. Microsatelllite makers were used to determine parentage of lambs. Paternity was established for over 80 percent of the lambs sampled.

Rams which had higher than expected numbers of lambs made up 23–29% of the ram population but sired from 39.4% to 70% of the lamb crop. Low performing rams (23–43% of the ram population) sired from 3.2% to 16.2% of the lamb crop.

Poor mating behavior increases ram costs and extends the lambing season while decreasing genetic progress.

Source: Abstract. Small Ruminant Research, October 2012.