Ovarian cyclicity and serum progesterone and luteinizing hormone in fine-wool ewes supplemented with alfalfa or pinto beans.
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).
Hamadeh
S K
SK
Department of Animal and Range Sciences New Mexico State University Las Cruces, NM 88003-0009 USA.
Hulet
C V
CV
Ross
T T
TT
Hallford
D M
DM