Effects of feeding a high-grain diet at a restricted intake on lactation performance and rebreeding of ewes

Fifty-six mature Polypay ewes were used in two experiments to examine the effects of feeding a high-grain diet at a restricted intake on milk production and composition, lamb performance and out-of-season breeding. Ewes were fed either a high-grain diet (85% concentrate and 15% forage) or a high-forage diet. The high-forage diets were 68% forage and 32% concentrate in Experiment 1 and 80% forage and 20% concentrate in Experiment 2. Forage source was orchardgrass hay (Experiment 1) or alfalfa cubes (Experiment 2). Feed intake of the high-grain diet was restricted by 20% (compared with ewes fed high forage) so that intake of energy was similar for both dietary groups. Daily milk production was 19% higher (P 0.05) in Exp. 1 and 8% higher (P 0.10) in Exp. 2 for ewes fed high grain than for those fed high forage (2.71 vs 2.28 kg/d and 3.18 vs 2.95 kg/d in Exp. 1 and 2, respectively). Milk protein percentage and daily amount of milk protein were higher (P 0.05) and the percentage of milk fat was lower (P 0.03) for ewes fed the high-grain diet than for those fed the high-forage diet. Diet did not affect milk fat production (grams/day) or lamb growth rate. In both experiments blood insulin concentration was higher for ewes fed the high-grain diet than for those fed the high-forage diet; however, no improvements in reproductive performance were observed. Limit feeding high-grain diets is an effective alternative to forage for lactating ewes