title: Environmental, genetic and social factors affecting the expression of estrus in beef cows.
abstract: Genetic, social and environmental factors affecting behavioral estrus were evaluated in Angus (n = 10), Brahman (n = 10) and Senepol (n = 10) cows during a PGF2alpha synchronized estrus and subsequent spontaneous estrus. Cows were equally stratified by breed to two groups of 15. Both groups were pre-synchronized with a modified two-injection PGF2alpha protocol. At the start of the experiment, cows were treated with 25 mg PGF2alpha followed by a second and third administration of 12.5 mg PGF2alpha, 11 and 12 days later to induce synchronized estrus. The subsequent estrus was designated as spontaneous estrus. Behavioral estrus data including the onset and end of estrus, estrous duration and the total number of mounts received for the synchronized and spontaneous estruses were collected using HeatWatch". Interval from the third PGF2alpha, treatment to the onset of a HeatWatch" estrus occurred earlier (P < 0.05) in Angus (31 +/- 5 h) than Brahman (53 +/- 7 h) or Senepol (53 +/- 4 h) cows, with dominant Senepol and Brahman cows taking longer to exhibit estrus after PGF2alpha than subordinate cows. The duration of the synchronized estrus tended to be shorter (P < 0.06) in Senepol (12 +/- 3 h) than in Angus (19 +/- 2 h) or Brahman (17 +/- 2 h) cows. Behavioral estrus data between the two periods were confounded by greater temperature-humidity index (THI) values during spontaneous estrus. The THI during spontaneous estrus appeared (P = 0.09) to affect the duration of estrus (9 +/- 1 h versus 16 +/- 1 h) and did affect (P < 0.0001) the total number of mounts received (8 +/- 4 mounts versus 34 +/- 4 mounts) during spontaneous estrus compared to synchronized estrus. Breed had no effect (P > 0.10) on the duration and total number of mounts received during synchronized and spontaneous estruses. In conclusion, type of estrus (synchronized or spontaneous), THI, social dominance and breed exerted significant effects on characteristics associated with behavioral estrus in beef cattle in subtropical environments.
authors.affiliation: College Veterinary Medicine, Large Animal and Clinical Sciences, University of Florida, Gainsville, USA.
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Landaeta-Hernández
authors.forename: Joel V
authors.initials: JV
authors.lastname: Yelich
authors.forename: J Willard
authors.initials: JW
authors.lastname: Lemaster
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Fields
authors.forename: Than
authors.initials: T
authors.lastname: Tran
authors.forename: Chad C
authors.initials: CC
authors.lastname: Chase
authors.forename: D Owen
authors.initials: DO
authors.lastname: Rae
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Chenoweth
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D015237:Dinoprost / Q000008:administration & dosage; D004777:Environment; D004971:Estrus / Q000235:genetics* / Q000502:physiology*; D004972:Estrus Detection; D004973:Estrus Synchronization; D005260:Female; D006813:Humidity; D012726:Sexual Behavior, Animal; D012931:Social Environment; D013045:Species Specificity; D013696:Temperature; D013997:Time Factors
chemical_list: D015237:Dinoprost