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Effects of Energy Intake and Number of Lambs Suckled on Milk Yield, Milk Composition and Energetic Efficiency of Lactating Ewes

Cornell University, Ithaca, New York

Abstract

Twenty western ewes of mixed Rambouillet and Columbia breeding, 10 with single lambs and 10 with twin lambs, were used in a 2 x 2 factorial experiment to study the effect of two levels of digestible energy and the number of lambs suckled on milk production and composition, and on lamb growth, during the first 90 days of lactation. The DE values were approximately 96% and 113% of the requirements of the lactating ewe for the first 8 to 10 weeks of lactation, as recommended by the National Research Council (N.R.C., 1957). The ewes were individually fed a 55%-roughage: 45%-concentrate ration in pellet form. The lambs had access to limited quantities of the same ration in individual creep pens.

Milk production was determined by hand milking following injections of a purified oxy-tocic principle at the beginning and end of a 2-hr. interval during the first 8 weeks of lactation and 3-hr. intervals the 10th and 12th weeks. Test milk values were obtained in lactation weeks 1, 2, 4, 6, 8, 10 and 12. Each milk sample was analyzed for dry matter, protein, fat, ash and caloric content.

Efficiencies of the ewes in converting feed energy into milk energy were determined. Estimations of the caloric contribution of body weight losses of the ewes were used in these determinations. The results are summarized as follows:

1. Ninety-day milk yield, milk calorie production and lamb weights were significantly (P<.05) increased by feeding the ewes approximately 17%; more DE and were significantly (P<.01) higher for ewes suckling twin lambs than for those suckling singles.
   
2. Feeding levels of DE had no significant effect on milk composition. Percent dry matter, fat and caloric value of the milk were significantly (P<.05) higher for ewes suckling twin lambs.
   
3. Variation in feed intake by ewes did not result in significant differences in converting feed energy into milk energy. Ewes suckling twin lambs were more efficient (P<.01) in converting feed energy into milk energy.
   

¹ Department of Animal Husbandry.

² Taken from thesis data submitted by the senior author to the Graduate School, Cornell University, in partial fulfillment of the requirements for the Ph.D. degree.

³ Appreciation is expressed to L. Hunt, R. Eckhardt and C. Rounsevell in caring for the animals, and to Mrs. S. Swackhamer, Mrs. E. Lloyd, R. Kaufman and David Wolfe, for assistance with analyses.