Effects of late-gestation heat stress independent of reduced feed intake on colostrum, metabolism at calving, and milk yield in early lactation of dairy cows.

Autor:	Seyed Almoosavi SMM; Department of Animal and Poultry Nutrition, Faculty of Animal Science, Gorgan University of Agriculture Science and Natural Resources, Gorgan 49138-15739, Iran. Electronic address: sm_smusavi@yahoo.com., Ghoorchi T; Department of Animal and Poultry Nutrition, Faculty of Animal Science, Gorgan University of Agriculture Science and Natural Resources, Gorgan 49138-15739, Iran., Naserian AA; Department of Animal Science, Ferdowsi University of Mashhad, Mashhad 91779-48978, Iran., Khanaki H; Faculty of Veterinary and Agricultural Sciences, Dookie Campus, The University of Melbourne, Victoria 3647, Australia., Drackley JK; Department of Animal Sciences, University of Illinois, Urbana 61801., Ghaffari MH; Institute of Animal Science, Physiology Unit, University of Bonn, 53115 Bonn, Germany. Electronic address: morteza1@uni-bonn.de.
Jazyk:	angličtina
Zdroj:	Journal of dairy science [J Dairy Sci] 2021 Feb; Vol. 104 (2), pp. 1744-1758. Date of Electronic Publication: 2020 Dec 11.
DOI:	10.3168/jds.2020-19115
Abstrakt:	The objective of this study was to differentiate the effects of acute heat stress (HS) from those of decreased dry matter intake (DMI) during the prepartum period on metabolism, colostrum, and subsequent production of dairy cows. Holstein dairy cows (n = 30) with similar parity and body weight were randomly assigned to 1 of 3 treatments on 45 d before calving: (1) cooled (CL, n = 10) conditions with ad libitum feed intake, (2) HS conditions with ad libitum feed intake (n = 10), and (3) pair-fed cooled (CLPF, n = 10) with reduced DMI similar to the HS group while housed under cooled conditions. The reduction in the amount of feed offered to the CLPF cows was calculated daily as the percentage decrease from the average DMI of HS cows relative to the CL cows. For CLPF and CL cows, barns provided shade, sprinklers, and fans, whereas the HS cows were provided only with shade. Cows in all groups received individually the same total mixed ration. Cows were dried off 60 d before the expected calving. Cows in the HS group and, by design, the CLPF cows had reduced DMI (~20%) during the experiment. Heat stress decreased gestation length, first colostrum yield, and calf birth weight compared with CL and CLPF cows. Milk yield decreased 21% (5 kg) in the HS and 8% (2 kg) in CLPF cows, indicating that reduced feed intake during late gestation accounted for 60% of the total reduced milk yield. The CLPF cows exhibited an elevated NEFA concentration compared with the CL and HS cows. The HS cows had a greater mRNA abundance of HSP70 in the peripheral blood leukocytes at 21 d prepartum compared with the other groups. At calving, the mRNA abundance of HSP70 was greater in HS cows, followed by CLPF, compared with the CL cows. In conclusion, HS during the late gestation period caused metabolism and production differences, which were only partially attributed to reduced feed intake in dairy cows. (Copyright © 2021 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)
Databáze:	MEDLINE
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