Effects of heat stress on production, somatic cell score and conception rate in Holsteins.
We examined the effects of heat stress (HS) on production traits, somatic cell score (SCS) and conception rate at first insemination (CR) in Holsteins in Japan. We used a total of 228 242 records of milk, fat and protein yields, and SCS for the first three lactations, as well as of CR in heifers and in first- and second-lactation cows that had calved for the first time between 2000 and 2012. Records from 47 prefectural weather stations throughout Japan were used to calculate the temperature-humidity index (THI); areas were categorized into three regional groups: no HS (THI < 72), mild HS (72 ≤ THI < 79), and moderate HS (THI ≥ 79). Trait records from the three HS-region groups were treated as three different traits and trivariate animal models were used. The genetic correlations between milk yields from different HS groups were very high (0.91 to 0.99). Summer calving caused the greatest increase in SCS, and in the first and second lactations this increase became greater as THI increased. In cows, CR was affected by the interaction between HS group and insemination month: with summer and early autumn insemination, there was a reduction in CR, and it was much larger in the mild- and moderate-HS groups than in the no-HS group.
Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan.
Koichi
K
Hagiya
NARO Institute of Livestock and Grassland Science, Nasushiobara, Tochigi, Japan.
Kiyoshi
K
Hayasaka
NARO Hokkaido Agricultural Research Center, Sapporo, Japan.
Takeshi
T
Yamazaki
National Livestock Breeding Center, Nishigo, Fukushima, Japan.
Tatsuo
T
Shirai
National Livestock Breeding Center, Nishigo, Fukushima, Japan.
Takefumi
T
Osawa
Rakuno Gakuen University, Ebetsu, Japan.
Yoshinori
Y
Terawaki
Nihon University, Fujisawa, Japan.
Yoshitaka
Y
Nagamine
Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan.
Yutaka
Y
Masuda
Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan.
Mitsuyoshi
M
Suzuki
D000818:Animals; D002417:Cattle / Q000235:genetics* / Q000502:physiology*; D005223:Fats / Q000032:analysis; D005260:Female; D005306:Fertilization / Q000235:genetics* / Q000502:physiology*; D018869:Heat-Shock Response / Q000235:genetics* / Q000502:physiology*; D006358:Hot Temperature; D006813:Humidity; D007314:Insemination; D007774:Lactation / Q000502:physiology*; D008892:Milk / Q000737:chemistry / Q000166:cytology; D008894:Milk Proteins / Q000032:analysis; D019655:Quantitative Trait, Heritable; D012621:Seasons; D013696:Temperature
D005223:Fats; D008894:Milk Proteins
Holsteins; genetic correlation; heat-stress; temperature-humidity index (THI)