HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lewis, G. S. Articles by Collier, R. J. Search for Related Content PubMed PubMed Citation Articles by Lewis, G. S. Articles by Collier, R. J.

Effects of Heat Stress during Pregnancy on Postpartum Reproductive Changes in Holstein Cows¹

University of Florida^,3,4,, Gainesville 32611

Abstract

Effects of heat stress during the last third of gestation on reproductive changes postpartum were studied in Holstein cows. Cows and heifers 160 to 190 d of gestation were assigned in June 1978 to shade (n = seven cows and two heifers) or no shade (n = eight cows and two heifers) management treatments. After parturition, all cows (n = 19) were moved to the milking herd and managed uniformly. On the day of calving and on each Monday, Wednesday and Friday thereafter until d 50 postpartum, jugular blood samples were collected. Beginning approximately 7 d postpartum, the reproductive tract of each cow was examined rectally after collection of blood samples. Estrus was monitored twice daily and cows were inseminated after d 45 postpartum. Prepartum heat stress increased 13,14-dihydro-15-keto-prostaglandin F₂ (PGFM) concentrations postpartum and increased the rate of uterine involution. Regardless of prepartum treatment, progesterone concentrations indicated that luteal phases had begun by d 12.4 ± 1.3 postpartum, which was about 3 d before PGFM was basal. The first luteal phase lasted only 10.7 ± .9 d. First estrus was not detected until d 32.3 ± 4.8 postpartum. The previously gravid uterine horn had a negative effect on ovarian volume, diameter of the largest follicle and percentage of ovaries with a corpus luteum. However, prepartum heat stress attenuated this effect. This study indicates that heat stress prepartum had residual effects on postpartum reproductive changes, and that the previously gravid uterine horn exerted some control, which was attenuated by heat stress, over ovarian recrudescense. Even though heat stress prepartum affected sensitive measures of postpartum reproductive function, it did not alter days to first estrus, days open (102.3 ± 13.1) or services/conception (2.5 ± .3).

¹ Florida Agr. Exp. Sta. Journal Ser. No. 4460.

² Present Address: Reproduction Laboratory, USDA, Animal Science Institute, Agricultural Research Center, Beltsville, MD 10705.

³ Dairy Sci. Dept. Institute of Food and Agr. Sci.

⁴ Dept. of Reprod., College of Vet. Med.