1Department of Animal and Dairy Sciences, Mississippi State University, Mississippi State 39762, USA.
2Department of Mathematics and Statistics, Mississippi State University, Mississippi State 39762, USA.
3College of Veterinary Medicine, Mississippi State University, Mississippi State 39762, USA.
4Dairy Records Management Systems, Raleigh 27603-3435, USA.
†For correspondence: Boulevard Delta s/n, Ejido Nuevo León, B.C., México, 21705; phone (686)52300-88; fax (686)523302-17; E-mail: lar62@hotmail.com
*Present affiliation: Instituto de Ciencias Agrícolas, Universidad Autónoma de Baja California, Ejido Nuevo León, Valle de Mexicali, Baja California, México.
To estimate the relationship between heat stress during the last 60 d prepartum, body condition score and certain productive traits in the subsequent lactation of Holstein cows, 564 multiparous and 290 primiparous cows from four dairy herds in Mississippi state were used. Maximum temperature-humidity index (MTHI) was calculated to quantify the degree of heat stress and was included in multiple regression models. Animals were scored for body condition at dry off, at calving and at 60 d postpartum. In multiparous cows, prepartum MTHI (MPTHI) had a negative effect on milk production at 200 d postpartum. One point of decrease in BCS from calving to 60 d postpartum in multiparous cows was associated with 246 kg more milk during the first 100 d of lactation. One point of increase in BCS from calving to 60 d postpartum was associated with 1.85 kg of less milk at peak of milk production. There was no effect of MPTHI on postpartum production performance in primiparous cows. Heat stress prepartum, considering ambient temperature and relative humidity, reduced milk production.
Milk production, body condition score, heat stress, temperature-humidity index
