Season and supplementation effects on ovarian activity in fine-wool ewes grazing native range or in confinement

TitleSeason and supplementation effects on ovarian activity in fine-wool ewes grazing native range or in confinement
Publication TypeConference Proceedings
Year of Publication1988
AuthorsHamadeh S.K., Hulet, Clarence V., Ross T.T.
Conference NameProceedings of the Annual Meeting, Western Section, American Society of Animal Science
Volume39
Pagination86-89
Date Published1988
Abstract

Effects of season and supplementation on incidence and rate of ovulation in multiparous, non-lactating ewes were investigated under range and dry-lot conditions over a 1-year period. In the range trial, 45 ewes received one of three nutritional treatments, range forage alone (R) and range forage supplemented with either 0.33 kg•head-1 • d-1 pinto beans (RB) or 0.45 kg•head -1 •d-1  alfalfa pellets (RP). Another 45 ewes were maintained in dry lots and fed 1.33 kg•head-1  •d-1  prairie hay (H) and either pinto beans (HB) or alfalfa pellets (HP) at the same rates used in the range trial. Ovarian structures were observed by laparoscopy at monthly intervals, except during breeding season (September-January). Supplemented ewes in both trials were heavier (P<.05) than R and H ewes during most of the study. In the range trial, incidence of ovulation and ovulation rate tended to be higher in RB ewes in April (P = .21) and June (P = .33 and P = .24 respectively) compared to R and RP ewes. In the dry-lot trial, ovulation rate tended to be higher in HB ewes (P = .21) in February and in HP and HB ewes (P = .13) in March compared with H ewes. Except for those trends, seasonality of ovulation was ,not influenced by supplementation (P>.40). Incidence of ovulation approached zero in  dry-lot ewes in April, May, June and July. In contrast 43%, 27%, 35% and 21% of range ewes were ovulating during those same months.

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