Ewe and ram fertility in commercial flocks mated with differing numbers of ewes per ram

Abstract

Groups of four or five rams were mated with groups of ewes at two ram-to-ewe ratios on each of five commercial properties. Crayon colours indicative of mating were recorded 17, 34, and 51 days after the start of the experiments. The number of ewes pregnant was determined 120 days after the start of mating. Doubling the number of ewes per ram in comparison with traditional practices had no detrimental effects on percentages of ewes mated, returning to service, or pregnant at the time of diagnosis. As the number of ewes per ram increased the number of ewes mated by each ram also increased, and in four of five experiments the mean number of rams mating each ewe decreased (P < 0.01). In three experiments return-to-service rates were higher in ewes mated by one ram only than in ewes mated by two or more rams (P < 0.01). There was no indication that P/2-year-old rams were less active than older rams.

Mating Conditions and Management Practices Influence Pregnancy Scanning Outcomes Differently between Ewe Breeds

“…Too few rams (less than 1%) can result in lower conception and ovulation rates, possibly due to crowding of the ram by ewes in estrus [ 58 ]. Increasing the ram to ewe ratio increased the number of times a ewe was mated, pregnancy rate and the number of twin lambs born [ 59 , 60 , 61 ]. Reasons for sub-optimal performance at high ram percentage may involve mating behaviors or nutrition.…”

The importance of clinical examination and reproductive evaluation of rams.

“…Μολοταΰτα, σε κοπάδια, στα οποία οι κριοί παραμένουν με τις προβατίνες καθ' όλη τη διάρκεια της περιόδου των οχειών, αναλογία έως και 1:100 (1% των θηλυκών ζώων) έχει θεωρηθεί επαρκής 6 . Αντίθετα, σε περιπτώσεις ρύθμισης του οιστρικοΰ κύκλου των προβατίνων η απαραίτητη αναλογία κυμαίνεται από 1:5 έως 1:10 (10 έως 20% των θηλυκών ζώων) 7 .…”