EFFECTS OF LIMIT FEEDING A HIGH-GRAIN DIET ON PUBERTY AND REPRODUCTIVE-PERFORMANCE OF EWES

In Exp. 1, 39 ewe lambs (initial BW 29 +/- .1 kg) were used in a 2 x 2 factorial arrangement with two breeds (Polypay and Targhee) and two d iets (high-forage and high-grain) to examine the effects of restrictin g intake of a high-grain diet on onset of puberty and lamb performance . The experimental diets were fed from 13 to 40 wk of age. The high-fo rage diet was composed of 80% alfalfa cubes and 20% supplement. The hi gh-grain diet was 90% concentrate and 10% alfalfa cubes. Feed intake o f the diets was controlled so that lambs fed the high-grain diet had t he same growth rate as those fed the high-forage diet. Plasma insulin concentration was higher (P < .001) for lambs fed the high-grain diet than for those fed the high-forage diet. However, no diet effect on ag e at puberty was observed. In Exp. 2, 88 mature Targhee ewes were used to determine the effects of limiting intake of a high-grain diet on p regnancy and number of lambs born per ewe. Intake of the high-grain di et was restricted to achieve similar ME intake between diets. There we re no diet effects on number of lambs born per ewe or subsequent lamb performance. Ewes fed the high-forage diet had a lower (P < .001) weig ht gain than those fed the high-grain diet. It was concluded that rest ricting intake of high-grain diets is an effective alternative to feed ing high-forage diets for meeting the nutrient requirements of ewe lam bs and gestating ewes; however, no improvements on reproductive perfor mance were observed.