An increased plane of nutrition of ewes before mating (flushing) has been associated with an increased number of lambs per ewe. The following study was done to investigate a possible mechanism for the flushing effect. During the summer, 98 Hampshire and Suffolk ewes grazed pastures with 50 of the ewes supplemented with .45 kg of corn grain X head-1 X d-1. For approximately 12 d before fall mating, each ewe received daily either .45 kg of a corn grain-soybean oil meal mixture, an oral dose of 1 g phenobarbital or no treatment. Liver biopsies were collected from 23 ewes, representing all treatment combinations, 3 d after initiation of pre-mating treatment for determination of concentration of hepatic mixed function oxidase enzymes (MFO). Summer supplementation vs no summer supplementation resulted in ewes with heavier (P less than .05) body weights near mating (75.6 vs 71.1 kg), higher (P less than .01) mating condition scores (3.2 vs 2.9), a greater (P less than .01) number of ovulations (1.99 vs 1.74), but little difference (P greater than .10) in number of lambs born per ewe lambing. Pre-mating treatment with phenobarbital or grain mix resulted in a greater number of ovulations (P less than .01, P less than .10, respectively) than no pre-mating treatment (2.14, 1.85, 1.60; respectively). Ewes given phenobarbital had more (P less than .10) lambs per ewe than ewes given no treatment (1.71 vs 1.40). Both phenobarbital and grain mix resulted in a significant increase in concentration of MFO compared with no treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Three trials, involving a total of 365 ewes, were conducted to determine the influence of the time when feed is available on the distribution of parturitions. In the initial trial, ewes were fed at either 0800, 1600 or 2400 h. Births were unevenly distributed throughout the day with 29% of parturitions occurring between 0400 and 0800 h (P < 0.01). The time of day when feed was available influenced the time of parturition (P < 0.01) with 64.9% of lambings occurring between 4 h prior to 8 h after feeding. In subsequent trials, feeding for 4 vs. 8 h, beginning in the morning, did not influence the proportion of ewes giving birth during the day (0600–1800 h) or during the late night (2200–0600 h). Feeding late in the morning (1200 h) compared with feeding at 0800 h did not significantly increase the proportion of parturitions occurring during the day (65.1 vs. 61.2%, respectively) but tended to reduce late night lambings (19.8% vs. 31.6, respectively; P = 0.06). It was concluded that a large proportion of daytime births can be achieved by feeding in the morning, and late morning feeding is indicated to reduce late night parturitions. Key words: Sheep, parturition, feeding, diurnal
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