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Development of the Polypay breed was undertaken to combine into a composite breed the potential for greatly increased reproductive capacity along with desirable growth rate and carcass quality. Four breeds were selected for the foundation of the new breed--the Rambouillet and the Targhee for hardiness, large body size, long breeding season, herding instinct and fleece characteristics; the Dorset for carcass quality, milking ability and long breeding season and the Finnsheep for early puberty, early postpartum fertility and high lambing rate. Dorset X Targhee and Finnsheep X Rambouillet matings were first made in 1968, and reciprocal Dorset-Targhee X Finn-Rambouillet matings were initiated in 1969. Beginning in 1970, the respective two-breed crosses and the four-breed cross (Polypay) were each mated inter se and selected, along with straightbred Rambouillets and Targhees, for lamb production when given two opportunities to lamb/year. Initial comparisons among straightbreds and inter se mated groups showed few important differences in meat-type body conformation, body condition or growth rate, but superior annual reproductive performance by Polypays. Fertility of Polypays at 1 yr of age was high and comparable to that of the Finn-Rambouillets. Response of Polypays to twice-a-year lambing was superior to responses of Rambouillets. Targhees, Dorset-Targhees or Finn-Rambouillets. The 1974 to 1975 annual production of young Polypays was about 13% more lambs weaned than from Finn-Rambouillets and 18% more weight of lamb weaned than from Dorset-Targhees, the best of the other groups for these traits. The current (1979 to 1981) reproductive performance of Polypay ewes selected for high once-a-year lambing rate under typical range management conditions is very competitive with that of 1/2 Finn crossbreds. Annual production of mature Polypays on the twice-a-year lambing schedule was 1.78 lambs weaned and 58.6 kg of lamb weaned/ewe put into fall breeding.

Effects of season, nutritional environment, and presence of rams on incidence and rate of ovulation in fine-wool sheep in southern New Mexico were investigated over 14 months (February 1983-March 1984). Number of corpora lutea (CL) were observed each month by laparoscopy in random samples from six ewes in each subgroup. Seasonality of ovulation in fine-wool sheep managed on range was much more marked than in animals managed on alfalfa hay in drylot. Incidence of ovulation approached zero in range-managed ewes during May, June, and July (8%, 0%, 4%) but was higher (P<0.05) in the alfalfa-drylot group (42%, 17%, 75%), respectively. Although the incidence remained lower (P<0.05) in August in range-managed than in drylot ewes (50% and 83%, respectively), both groups were ovulating at a high rate during September through January. Incidence of ovulation dropped dramatically both years in the range-managed group in February compared with that of the alfalfa-drylot group (48% and 36% vs 100% and 83%). Mean ovulation rate per ewe ovulating did not differ (P>0.10) between nutrition groups within the 14 months. Body weight was related to CL number during periods of seasonal transition only. Continuous or intermittent presence of a ram had no real effect on either incidence or rate of ovulation during the transitional months. Nutritional environment can affect seasonality of breeding in fine-wool range sheep. This effect may not be consistently modified by presence of rams.

A debilitating condition affecting mature ewes was found to be associated with the visceral form of caseous lymphadenitis, chronic progressive pneumonia, and Corynebacterium pyogenes infections. The condition was termed thin ewe syndrome. Affected and normal ewes were compared for reproductive efficiency by breed and age; differences in reproductive efficiency between affected and normal Rambouillet and Columbia ewes were highly significant (P less than 0.01). Although not statistically significant, the trend in Targh ee ewes was similar. There was a direct correlation between occurence of the syndrome and increasing age for all breeds.

Effects of season and supplementation on the incidence and rate of ovulation and hormone profiles in multiparous, nonlactating ewes were investigated under range and drylot conditions during anestrus (February through August). Ninety ewes received one of six nutritional treatments: 1) range forage, 2) range forage plus 0.33 kg.hd(-1).d(-1) pinto beans, 3) 0.45 kg.hd(-1).d(-1) alfalfa pellets, 4) dry lot plus 1.33 kg.hd(-1).d(-1) prairie hay only, 5) pinto beans or 6) alfalfa pellets at rates used on the range and prairie hay. Supplemented ewes were heavier (P < 0.05) than ewes fed range forage or prairie hay during most of the study. Seasonality of ovulation, in terms of incidence and rate, was not affected (P > 0.40) by supplementation in range ewes. The ovulation rate tended to be highest in prairie hay plus pinto bean drylot ewes in February (P = 0.21) and in prairie hay plus alfalfa pellet and prairie hay plus pinto bean ewes in March (P = 0.13) compared with prairie hay ewes. Generally, seasonality of ovulation was not influenced by supplementation (P > 0.40). The incidence of ovulation approached zero for drylot ewes in April, May, June and July, while it was 43, 27, 35 and 21% for range ewes, in those same months. Supplementation did not affect serum progesterone during the estrous cycle. Luteinizing hormone (LH) concentrations were similar (P > 0.50) among drylot treatment groups before a 50-ug gonadotropin releasing hormone (GnRH) challenge. Pinto bean supplementation enhanced serum LH response to GnRH (P < 0.10).