Effects of month of breeding on reproductive efficiency of Holstein cows and heifers inseminated with sex-sorted or conventional semen in a hot environment.
The main objective of this study was to assess the effect of month of breeding on reproduction performance of Holstein heifers and cows inseminated with sex-sorted or conventional semen in a hot environment. Pregnancy per artificial insemination (P/AI; 64,666 services over an 8-year period) both in heifers (n = 22,313) and cows (n = 42,353) from a large dairy herd in northern Mexico (26°N) were evaluated with the GENMOD procedure of SAS, with respect to month of AI. Overall, P/AI with sex-sorted semen was greater (P < 0.01) in heifers (41.6 %) than cows (17.3 %). P/AI for cows serviced with conventional semen was 10 % points higher (P < 0.01) in January and December (31 vs. 21 %) than cows serviced with sex-sorted semen. While there was no difference in P/AI between the sex-sorted sperm and conventional semen in cows inseminated in July (16 and 18 %, respectively), P/AI plummeted for both groups of cows during the summer and fall (more severe heat stress). P/AI was not different between heifers serviced with sex-sorted or conventional semen during the hottest months of the year (July to October). However, during the coldest month of the year (January and February), P/AI was 10 percentage points greater (P < 0.01) in heifers serviced with conventional than sex-sorted semen. It was concluded that in this hot climate cow and heifer fertility declined in the summer and fall when inseminated with conventional semen. However, the use of sex-sorted semen during summer and fall did not compromise the breeding success in heifers. Thus, this data suggest that sex-sorted semen promotes some embryonic thermoprotective mechanism, which leads to a marginal summer and fall fertility depression with this type of semen in this particular hot environment.
Department of Animal Nutrition, Autonomous Agrarian University Antonio Narro, Saltillo, Coahuila, 25315, Mexico.
Miguel
M
Mellado
Edgar
E
Sepulveda
Ulises
U
Macias-Cruz
Leonel
L
Avendaño
Jose E
JE
Garcia
Francisco G
FG
Veliz
Alvaro
A
Rodríguez
D000818:Animals; D002417:Cattle / Q000502:physiology*; D005260:Female; D005298:Fertility / Q000502:physiology*; D006358:Hot Temperature; D007315:Insemination, Artificial / Q000662:veterinary*; D008297:Male; D008800:Mexico; D011247:Pregnancy; D018873:Pregnancy Rate; D012621:Seasons; D012743:Sex Preselection / Q000662:veterinary*