Modelling THI effects on milk production and lactation curve parameters of Holstein dairy cows

Naceur M'Hamdi; Cyrine Darej; Khaoula Attia; Ibrahim El Akram Znaidi; Refka Khattab; Hanane Djelailia; Rachid Bouraoui; Rahma Taboubi; Lamjed Marzouki; Moez Ayadi

doi:10.1016/j.jtherbio.2021.102917

Modelling THI effects on milk production and lactation curve parameters of Holstein dairy cows

J Therm Biol. 2021 Jul:99:102917. doi: 10.1016/j.jtherbio.2021.102917. Epub 2021 Apr 21.

Authors

Affiliations

¹ Research Laboratory of Ecosystems & Aquatic Resources, National Agronomic Institute of Tunisia, Carthage University, 43 Avenue Charles Nicolle, Tunis, 1082, Tunisia. Electronic address: naceur_mhamdi@yahoo.fr.
² Research Laboratory of Ecosystems & Aquatic Resources, National Agronomic Institute of Tunisia, Carthage University, 43 Avenue Charles Nicolle, Tunis, 1082, Tunisia.
³ Department of Animal Production, Higher Agronomic Institute of Chott-Meriem, University of Sousse, Tunisia.
⁴ Department of Animal Production, Higher School of Agriculture of Mateur, Carthage University, Tunisia.
⁵ Ministry of Agriculture, Pasture, and Livestock Office, Tunisia.
⁶ Unit of Functional Physiology and Bio-Resources Valorization (BF-VBR), Higher Institute of Biotechnology of Beja, University of Jendouba, 9000, Beja, Tunisia.

PMID: 34420599
DOI: 10.1016/j.jtherbio.2021.102917

Abstract

The main objective of this study was to determine the potential impact of heat stress (HS) on milk production and lactation curve parameters of Holstein dairy cows. Milk, fat, protein, and somatic cell count test-day records collected between 2013 and 2019 from 947 cows in 23 herds were combined with THI calculated from meteorological data recorded between 2013 and 2019. The temperature-humidity index (THI) was used to investigate the effect of heat stress. The severity of heat stress was measured using the temperature-humidity index (THI) and the impacts of different THIs-low (≤68), moderate (68-72), and high (≥72) on production performance and lactation curve parameters were measured. The nonlinear model of Wood was applied for modeling the lactation curve. Analysis of variance was applied to test the effects of three levels of THI on milk production, its composition, and lactation curve parameters. Results showed losses due to heat stress. A decrease in milk yield and fat and protein content was reported. Fat and protein contents tended to decrease steadily with increasing values of THI. Milk yield ranged from 17.882±0.064 (68<THI<72) to 16.503 ±0.035 kg/j (THI>72), fat and protein contents ranged from 3.551 ±0.041 to 3.449 ±0.026 and from 3.246 ±0.031%, to 3.113 (0.029) for 68<THI<72 and THI>72, respectively. Somatic cell score was marked by an increase (from 4.143 to 4.358) at the highest ranges of THI>72 and decreased values (from 4.143 to 3.857) at the lowest ranges of THI. Heat stress showed a significant effect on the parameters of the lactation curve. The increased value of THI showed a significant effect on milk yield THI was in a significant negative correlation with the yield, and quality of milk. The effect of THI was highly significant (P < 0.05) for all parameters of the lactation curve and milk yield. Cows exposed to THI between 68 and 72 achieved the highest peak milk yields and the highest total yield of 305 days of lactation (Y305).

Keywords: Dairy cattle; Heat stress; Holstein; Lactation curve; THI.

MeSH terms

Animals
Cattle / physiology*
Dairying
Female
Heat-Shock Response / physiology*
Hot Temperature
Humidity
Lactation*
Milk / chemistry
Models, Biological*