Social and breed effects on the expression of a PGF2alpha induced oestrus in beef cows.
Social organization and breed effects following PGF2alpha were studied in mature Angus, Brahman and Senepol cows allocated into two groups (each A = 5, B = 5 and S = 5). Variables including interval to oestrus onset (IEO), oestrous duration (DE), total mounts received (TMR), and oestrous intensity (IE) were derived via HeatWatch. Breed-type influenced IEO (B = 42.6 +/- 6.7 h; S = 54.6 +/- 6.0 h; and A = 27.8 +/- 5.8 h; p < 0.003). Within breeds, dominant B (69.4 +/- 13.3 h) and S (65.5 +/- 7.4 h) cows were slower (p < 0.05) to be detected in oestrus than subordinate (38.1 +/- 4.4 h) and intermediate (40.6 +/- 6.0 h). However, within A, dominant cows (16.4 +/- 12.5 h) were detected in oestrus earlier (p < 0.05) than intermediate (44.3 +/- 9.2 h) and subordinates (32.7 +/- 5.1 h). Angus (21.5 +/- 2.4 h) and B (22.1 +/- 3.0 h) cows had longer (p < 0.01) DE than S (9.1 +/- 2.8 h). Dominants (20.4 +/- 3.0) and intermediates (20.2 +/- 2.3 h) cows had longer DE (p < 0.04) than subordinates (12.1 +/- 2.1 h) although the interaction breed x social order showed that dominant S had shorter DE than dominant A and B (10.1 +/- 3.3; 34.8 +/- 6.0 h; and 20.0 +/- 6.4 h, respectively; p < 0.001). Angus cows had less TMR than B (p < 0.02) and tended to be less than S cows (p < 0.06). Overall, greatest (p < 0.008) IE occurred in the first 9 h after onset of oestrus with no breed effect (p > 0.05). Dominant cows tended (p < 0.10) to have less TMR (3.2 +/- 0.7 mounts) than subordinate (4.1 +/- 0.4 mounts) and intermediate (4.7 +/- 0.6 mounts) throughout, especially 3-6 h after oestrus onset (p < 0.07). Breed and social order both influence PGF2alpha-induced oestrus behaviour.
Landaeta-Hernández
A J
AJ
Facultad de Ciencias Veterinarias, Universidad del Zulia, Av Guajira, Ciudad Universitaria. Maracaibo, Venezuela. landaetaa@yahoo.es
Palomares-Naveda
R
R
Soto-Castillo
G
G
Atencio
A
A
Chase
C C
CC
Chenoweth
P J
PJ
D000818:Animals; D001947:Breeding; D002417:Cattle / Q000502:physiology*; D015237:Dinoprost / Q000494:pharmacology*; D004971:Estrus / Q000187:drug effects / Q000502:physiology; D004972:Estrus Detection; D005260:Female; D006608:Hierarchy, Social; D012726:Sexual Behavior, Animal / Q000187:drug effects* / Q000502:physiology*; D012930:Social Dominance
D015237:Dinoprost