1Instituto de Ciencias Agrícolas, Universidad Autónoma de Baja California, Mexicali, B.C. Av. Obregón y Julian Carrillo S/N, Mexicali. B.C. México C.P. 21100.
2Facultad de Medicina, Universidad Autónoma de Baja California, calle Dr. Humberto Torres, Sanginés S/N Centro Cívico, Mexicali, B.C. México. C.P. 21100.
3Facultad de Zootecnia, Universidad Autónoma de Chihuahua, Perif. Fco. R. Almada Km 1, Chihuahua, Chih. México. C.P. 31453.
*Corresponding author: E-mail: acorrea@uabc.mx
In order to evaluate artificial cooling and timed artificial insemination (TAI) protocol on fertility during summer months, 90 Holstein heifers were randomly and equally assigned to three treatments: a) control group (S) with visual heat detection and insemination a.m-p.m after heat detection; b) a group (TAI+C) using a norgestomet ear implant (3 mg) plus an injection of 3 mg of norgestomet and 5 mg of estradiol valerate. The implant was removed after 9 d and 500 IU i.m of eCG were administered at the same time, plus a cooling period with spray and fans beginning at time of implantation until 21 d after AI; c) a third group (C) with heat detection and AI a.m-p.m, starting the artificial cooling when animals initiated in the treatment until 21 d after AI. Temperature-humidity index (THI) averaged 85 during the trial. T3 concentration increased in treatment groups. Conception rate among treatment groups was similar (P>.05). Artificial cooling increased heifers comfort and TAI plus cooling did not show any improvement on fertility.
Holstein heifers, heat stress, conception rate, artificial cooling, fixed time insemination
