Fertility following fixed-time AI in CIDR-treated beef heifers given GnRH or estradiol cypionate and fed diets supplemented with flax seed or sunflower seed》.pdf

Theriogenology 61 (2004) 1115–1124 Fertility following fixed-time AI in CIDR-treated beef heifers given GnRH or estradiol cypionate and fed diets supplemented with flax seed or sunflower seed a b ´ a a M.G. Colazo , J.P. Kastelic , M.F. Martınez , P.R. Whittaker , R. Wildeb c c a,* , J.D. Ambrose , R. Corbett , R.J. Mapletoft aDepartment of Large Animal Clinical Sciences, Western College of Veterinary Medicine (WCVM), University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan, SK, Canada S7N 5B4 bAgriculture and Agri-Food Canada, Research Centre, Lethbridge, AB, Canada T1J 4B1 cAlberta Agriculture, Food and Rural Development, Edmonton, AB, Canada T6H 4P2 Received 13 November 2002; accepted 20 June 2003 Abstract The objectives were to determine pregnancy rates following fixed-time AI (FTAI) in heifers: (1) given GnRH or estradiol cypionate (ECP) to synchronize follicular wave emergence and ovulation in a CIDR-based protocol; and (2) fed diets supplemented with flax or sunflower seeds. At two locations, Angus and crossbred Angus heifers (n ¼ 983) were examined ultrasonically to confirm reproductive maturity and randomly allocated to six synchronization groups in a 2 3 factorial design. On Day 0 (start of synchronization treatments), heifers received a CIDR and either 100 mg GnRH i.m. (n ¼ 492) or 1 mg ECP plus 50 mg progesterone i.m. (n ¼ 491); in these groups, CIDR removal and PGF treatment were done concurrently on Days 7 and 8.5, respectively. Heifers were re- randomized to receive 0.5 mg ECP i.m. at CIDR removal or 24 h later (with FTAI 58–60 h after C