Fertility of Holstein cows and heifers submitted to timed artificial insemination and receiving one or two doses (12 h apart) of semen |
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| Authors: | Miguel Mellado Lucía M Treviño María I Chavez Francisco G Véliz Ulises Macías-Cruz Leonel Avendaño-Reyes José E García |
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| Institution: | 1. Department of Animal Nutrition, Autonomous Agrarian University Antonio Narro, Saltillo, Mexico;2. Department of Veterinary Science, Autonomous Agrarian University Antonio Narro, Torreon, Mexico;3. Institute of Agriculture Science, Autonomous University of Baja California, Mexicali, Mexico |
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| Abstract: | The objective of this retrospective study was to assess the effect of receiving a single (n = 50,285) or double (n = 4392) artificial insemination (AI), 12 h apart, within a timed artificial insemination protocol on pregnancy per AI (P/AI) in nulliparous heifers (inseminated with either sex-sorted or conventional semen) and pluriparous Holstein cows in a commercial dairy herd. Also, this study aimed to investigate the relationship between temperature-humidity index (THI) and time of the first AI and fertility. Fertility of cows receiving two AI with normothermia (THI <68) was higher (p < .05) than cows receiving a single AI (42.9% vs. 36.4%). P/AI of cows receiving two AI with severe heat stress (THI >85) was higher (p < .05) than cows receiving a single AI (21.0% vs. 12.6%). Regardless of heat stress conditions, applying the first AI in the morning increased (p < .05) P/AI in cows with double AI than in cows whose first AI occurred in the afternoon (38.4 vs. 33.3%). With moderate heat stress, and sexed-sorted semen, P/AI to timed AI was higher (65.0 vs. 51.9%; p < .05) in heifers receiving double AI than those serviced once. It was concluded that double AI, 12 h apart, enhanced fertility at timed AI than herd mates with a single AI, particularly with heat stress at breeding. |
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| Keywords: | artificial insemination fertility heat stress Ovsynch pregnancy |
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