Studies on the number of ewes joined per ram for flock matings under paddock conditions. I. Mating behaviour and fertility

Abstract

In a series of six experiments rams were joined either singularly or in groups to varying numbers of ewes so that the number of ewes joined per ram varied between 25 and 100. Under the conditions of these experiments, decreasing the number of ewes joined per ram was associated with more rams serving each oestrous ewe, a greater proportion of ewes served during the first 2 weeks of joining, less ewes remaining unserved at the end of a 6 week joining period, and higher fertility (the proportions of ewes lambing and ewes twinning to ewes joined). A highly significant interaction (P < 0.001) between number of ewes joined per ram and ram age was found. Joining 25 ewes per ram gave higher fertility than 50 ewes per ram when 1½ -year-old rams were used, but similar fertility with 3½–5½-year-old rams. Older rams were more fertile than 1½-year-olds when joined at 50 ewes per ram, but not at 25 ewes per ram. These findings are discussed in relation to other factors that may influence the effect on flock fertility of varying the number of ewes joined per ram.

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

“…These data are in agreement with Allison (1975) and other New Zealand reports (Haughey 1959;Edgar 1965), but contrary to reports with Merino sheep in which increasing the number of ewes per ram has usually resulted in a lower proportion of ewes mated during the first 2 weeks of mating, more ewes remaining unmated, fewer rams mating each oestrous ewe, and a lower percentage of ewes lambing (Lightfoot & Smith 1968;Croker 1970;Dawe et at. 1974).…”

“…1971(Mattner et at. , 1973 and semen quality (Lightfoot 1968), which result in a reduction in the number of ewes mated (Croker & Lindsay 1972) and in ewe fertility, particularly at higher numbers of ewes per ram (Lightfoot & Smith 1968;Croker 1970). Also Dobbie (1974) has recorded low fertility in some flocks mated with a low percentage of 1 1/z-year-old rams in New Zealand, supporting Haughey's (1959) suggestion that "shearling" rams were of lower fertility than older rams.…”

Flock mating in sheep

“…Australian work with Merinos has shown that two-tooth rams mate with fewer ewes and sometimes are not as fertile as older rams (Lightfoot & Smith 1968;Croker 1970;Croker & Lindsay 1972;Mattner et al 1971Mattner et al , 1973. Two ram age groups joined with different numbers of ewes per ram were compared in two experiments to provide information on the Romney breed.…”

The mating behaviour of rams in a pedigree pen-mating system in relation to breed and fertility

“…Lightfoot and Smith (1968) found a ratio of 25 : 1 satisfactory for 1^-yr-old Merino rams used in paddock mating. The difference in fertility found between the young exotic and the mature naturalized groups of rams was unexpected in view of the general similarity of the behavioural observations between the groups.…”