PSXII-16 - Fertility affects in yearling beef heifers grazing triticale before artificial insemination

Our objective was to compare two systems of pre-breeding heifer development, drylot (D) or grazing winter triticale (T) on heifer fertility. In each of 4 years (yr), Black Angus heifers (n = 168, 86, 97 and 103, respectively) were allotted to treatment (trt) 32 to 50 days (d) prior to artificial insemination (AI). Each year a 14-d CIDR PG protocol was used to synchronize estrus (d-30 to d-16: 1.38 g progesterone intravaginal insert, CIDR; d 0: 25 mg dinoprost tromethamine injection; + 66 hours: 100 µg gonadorelin hydrochloride injection, and AI). Starting body weight and body condition were similar between treatments but differed by year (P < 0.01). After CIDR removal, 83% were in estrus by d -10 and did not differ with trt or yr. Weight at AI was greater (P < 0.01) for T (384 kg ± 2) than D (378 kg ± 2) with a trt by yr interaction. Body condition change between start of treatment and AI was greater (P < 0.01) for T (0.44 ± 0.03) than D (-0.02 ± 0.04) with a trt by yr interaction (P < 0.01) due to the magnitude of difference. A trt by yr interaction occurred for estrous response before AI (P < 0.01). Treatment means for AIPR were 59.1% (143/242) for D and 42.1% (101/240) for T (trt; P < 0.01). AIPR was similar between treatments in yr 1 and higher for D than T in subsequent yr (trt x yr, P < 0.05). Blood urea nitrogen was greater (P < 0.05) in T than D on d 0 and at AI. At the time of AI, triticale was more mature in yr 1 when there was no difference in AIPR. Grazing triticale during estrus synchronization and AI resulted in acceptable gains but decreased fertility in yearling beef heifers.