Effects of heat stress on production, somatic cell score and conception rate in Holsteins

• DOI: 10.1111/asj.12617
• Publication Date: 2016-04-26T20:41:59Z
• Authors: Koichi Hagiya; Kiyoshi Hayasaka; Takeshi Yamazaki; Tatsuo Shirai; Takefumi Osawa; Yoshinori Terawaki; Yoshitaka Nagamine; Yutaka Masuda; Mitsuyoshi Suzuki
• Keywords: Heat index

Abstract We examined the effects of heat stress (HS) on production traits, somatic cell score (SCS) and conception rate at first insemination (CR) in Holsteins Japan. used a total 228 242 records milk, fat protein yields, SCS for three lactations, as well CR heifers first‐ second‐lactation cows that had calved time between 2000 2012. Records from 47 prefectural weather stations throughout Japan were to calculate temperature–humidity index (THI); areas categorized into regional groups: no HS (THI < 72), mild (72 ≤ THI 79), moderate ≥ 79). Trait HS‐region groups treated different traits trivariate animal models used. The genetic correlations milk yields very high (0.91 0.99). Summer calving caused greatest increase SCS, second lactations this became greater increased. In cows, was affected by interaction group month: with summer early autumn insemination, there reduction CR, it much larger mild‐ moderate‐HS than no‐HS group.