Effect of hay quality and breed on the onset of puberty and subsequent reproductive performance in beef heifers

Abstract

The effect of hay quality on the onset of puberty and subsequent reproductive performance was evaluated in 51 3/4 Hereford x 1/4 Angus (HA) heifers and 47 3/4 Hereford x 1/4 Brahman (HB) heifers. Two qualities of alfalfa hay were fed ad libitum. along with an average of 3.1 lbs/hd/day of ground sorghum grain. HB heifers were heavier and carrying more backfat and body condition (P<.05) at the start of the experiment and they maintained their weight advantage through out the experiment. A higher (P<.05) percent of the UB heifers reached puberty by 14 and 15 months of age and became pregnant during a 45 day artificial insemination breeding period. HA heifers reached puberty at a lighter (P<.05) average weight. Heifers fed high quality alfalfa hay were heavier (P<.05) by the start of the breeding season and were carrying more (P<.05) backfat and body condition. A higher percent (P=.08) of the heifers receiving higher quality hay reached puberty by 16 months of age and a higher (P=.10) percent became pregnant during the breeding period. Heifers inseminated at their pubertal estrus had lower (P=.04) first service conception rates than heifers inseminated at their second or later estruses (52% vs. 88%).