Comparative effects of dry lot feeding and triticale grazing as prebreeding nutritional strategies on reproductive outcomes in yearling beef heifers

Our objective was to compare prebreed-ing nutritional management systems of either a dry lot (DLOT) ration or grazing of winter triticale (TRIT) on reproductive performance of yearling Bos tauru s heifers. In each of 4 yr, heifers (n = 168, 86, 97, and 103, respectively) were allotted to treatment 39 ± 8.3 d before artificial insemination (AI). Dry lot heifers received a growing ration (10.6% to 14.5% CP) composed of ranch-produced forages supplemented with corn and distillers grain. Winter triticale ranged in CP from 28.6% at the start of the study to 16.9% at AI. Estrus was synchronized with a 14-d controlled internal drug-release device (CIDR) plus prostaglandin F 2α (PG) fixed-time AI protocol, with AI 66 h after PG. Estrus-detection patches were used to determine estrous response after CIDR removal and before AI. Serum samples were collected at PG administration and at AI for determina-tion of serum urea nitrogen and nonesterified fatty acid analysis. Starting BW and BCS were not significantly different between management systems. Also, estrous response after CIDR removal or at AI did not differ significantly because of management. Body con-dition change tended to be greater for TRIT (0.45 ± 0.14) than DLOT (−0.02 ± 0.14). Pregnancy rate to AI was greater in DLOT (59.1 ± 3.2%) than in TRIT (42.1 ± 3.2%). Serum urea nitrogen concentrations were greater in TRIT than in DLOT at PG administration and at AI. Grazing triticale be-fore breeding can improve heifer body condition. However, heifers that graze triticale may have reduced pregnancy rates compared with those fed in a dry lot at least 30 d before breeding.