Effects of Metabolic Imprinting on Growth and Reproductive Performance of Early-weaned Beef Heifers

This study evaluated the effects of calf management following early weaning (EW) on growth and reproductive performance of beef heifers. On d 0, Brahman x British heifers (n = 40; body weight [BW] = 187 ± 37 lb; age = 69 ± 12 d) were stratified by age and BW, and randomly assigned to be normally-weaned on d 177 (NW), or 1 of 3 EW treatments: (1) EW and grazed on ryegrass pastures for 67 d then on bahiagrass pastures until d 177 (Ryegrass); 2) EW and limit-fed a high-concentrate diet in drylot until d 177 (Drylot); or 3) EW and metabolically imprinted by limit-feeding a highconcentrate diet for 94 d then grazed on bahiagrass pastures until d 177 (MI). Heifers were assigned to 1 of 2 pens per treatment. On d 177, heifers were grouped by treatment and grazed on bahiagrass pastures until the start of breeding season (d 335). Heifers on pastures were supplemented at 1.0 % BW until d 177 and 1.5 % BW from d 177 to 335. On d 177 and 335, Ryegrass heifers were lightest (P < 0.01) and Drylot heifers heaviest (P < 0.001) compared to all other treatments and NW and MI heifer BW did not differ (P ≥ 0.42). Heifers placed on highconcentrate diets achieved puberty sooner (P < 0.01) than NW and Ryegrass heifers, with no differences (P = 0.59) on age at puberty between NW and Ryegrass heifers. On d 330, MI and Drylot treatments increased (P = 0.002) the percentage of pubertal heifers compared to NW and Ryegrass heifers, but did not affect (P = 0.64) the percentage of pregnant heifers. Thus, heifer management systems after EW result in significant differences on BW at the time of normal weaning and increased puberty achievement prior to the breeding season.