Reference : Evaluation of Heat Stress Effects on Production Traits and Somatic Cell Score of Hols...
Scientific journals : Article
Life sciences : Animal production & animal husbandry
Life sciences : Genetics & genetic processes
Evaluation of Heat Stress Effects on Production Traits and Somatic Cell Score of Holsteins in a Temperate Environment
Hammami, Hedi mailto [Université de Liège - ULiège > Sciences agronomiques > Zootechnie >]
Bormann, Jeanne [Administration of Agricultural Technical Services, L-1019 Luxembourg, Luxembourg > > > >]
M'Hamdi, Naceur [High Institute of Agronomy of Chott-Mariem, TN-4042 Sousse, Tunisia > Animal Science > > >]
Montaldo, Horacio Hugo [Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Ciudad Universitaria, D.F. 04510, Mexico > Genética y Bioestadística > > >]
Gengler, Nicolas [Université de Liège - ULiège > Sciences agronomiques > Zootechnie >]
Journal of Dairy Science
American Dairy Science Association
Yes (verified by ORBi)
[en] thermal indices ; heat stress ; temperate climate ; dairy cattle
[en] This study was aimed to evaluate the degree of thermal stress exhibited by Holsteins under a continental temperate climate. Milk, fat, protein, and somatic cell count test-day records collected between 2000 and 2011 from 23,963 cows in 604 herds were combined with meteorological data from 14 public weather stations in Luxembourg. Daily values of six different thermal indices (TI) weighted in term of temperature, relative humidity, solar radiation, and wind speed were calculated by averaging hourly TI over 24 hours. Heat stress thresholds were firstly identified by a broken-line regression model. Regression models were thereafter applied to quantify milk production losses due to heat stress. The tipping points at which milk and protein yields declined were effectively identified. For fat yield, no valid threshold was identified for any of the studied TI. Daily fat yields tended to decrease steadily with increasing values of TI. Daily somatic cell scores (SCS) pattern was marked by increased values at both lowest and highest TI ranges with a more pronounced reaction to cold stress for apparent temperature indices. Thresholds differed between TI and traits. For production traits, they ranged from 62 (TI1) to 80 (TI3) for temperature-humidity indices (THI) and from 16 (TI5) to 20 (TI6) for apparent temperature indices. Corresponding SCS thresholds were higher and ranged from 66 (TI1) to 82 (TI3) and from 20 (TI5) to 23 (TI6), respectively. The largest milk decline per unit of mild, moderate, and extreme heat stress levels of 0.164, 0.356, and 0.955 kg, respectively, was observed when using the conventional THI (TI1). The highest yearly milk, fat, and protein losses of 54, 5.7, and 4.2 kg respectively were detected by TI2, the THI index that is adjusted for wind speed and solar radiation. The latter index could be considered as the best indicator of heat stress to be used for forecast and herd management in a first step in temperate regions under anticipated climate changes.
Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS
Researchers ; Professionals ; Students ; Others

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