title: Modelling temperature effects on milk production: a study on Holstein cows at a Japanese farm.
abstract: Milk yield and its composition vary according to individual cows as well as to a variety of different environment conditions, such as temperature. Previous studies suggest that heat exerts considerable negative effects on milk production and its composition, especially during summer months. We investigate the production and fat composition of milk from individual dairy cows and develop a modelling framework that investigates the effect of temperature by extending a traditional lactation curve model onto a more flexible statistical modelling framework, a generalised additive model (GAM). The GAM simultaneously copes with multiple different conditions (temperature, parity, days of lactation, etc.), and, importantly, their non-linear relationships. Our analysis of retrospective data suggests that individual cows respond differently to heat; cows producing relatively high quantities of milk tend to be particularly sensitive to heat. Our model also suggests that most dairy cows studied fall into three distinct cases that underpin the variation of the milk fat ratio by different mechanisms.
authors.affiliation: Jiyu Gakuen College, 1-8-15 Gakuen-cho, Higashikurume-shi, Tokyo, 203-8521 Japan.
authors.forename: Machiko
authors.initials: M
authors.lastname: Yano
authors.affiliation: School of Biology, Centre for Biological Diversity and Scottish Oceans Institute, University of St Andrews, Dyers Brae House, St Andrews, Fife KY16 9TH UK ; Department of Mathematics, Keio University, 3-14-1 Hiyoshi Kohoku, Yokohama, 223-8522 Japan.
authors.forename: Hideyasu
authors.initials: H
authors.lastname: Shimadzu
authors.affiliation: Jiyu Gakuen College, 1-8-15 Gakuen-cho, Higashikurume-shi, Tokyo, 203-8521 Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Endo
keywords: Heat stress; Lactation curves; Milk fat; Milk production; Modelling; Test-day data
references.citation: J Dairy Sci. 1997 Nov;80(11):3040-9
references.pmid: 9406097
references.citation: Trop Anim Health Prod. 1976 Feb;8(1):38-46
references.pmid: 3871
references.citation: J Anim Sci. 1988 Jan;66(1):112-25
references.pmid: 3366700
references.citation: J Dairy Sci. 2000 Sep;83(9):2120-5
references.pmid: 11003246
references.citation: J Dairy Sci. 2001 Oct;84(10):2314-20
references.pmid: 11699464
references.citation: J Dairy Sci. 2011 Sep;94(9):4502-13
references.pmid: 21854922
references.citation: J Dairy Sci. 2007 Apr;90(4):1947-56
references.pmid: 17369235
references.citation: J Dairy Sci. 2003 Jan;86(1):232-42
references.pmid: 12613867