Variation factors of pregnancy rates after oestrus synchronization treatment in French Charolais beef cows.
An epidemiological study was conducted in Bourgogne (France) in Charolais herds sampled in 1990 (sample 1:54 herds) and from 1991 to 1993 (sample 2:33 herds). The aim was primarily to quantify, at both herd and individual levels, the factors that result in variations in the response to synchronization treatment as estimated by pregnancy rate after first insemination. The second goal was to test a similar model in sample 2, which included only primiparous cows. In sample 1,329 cows of the 627 studied (52%) became pregnant compared with 122 primiparous cows of the 249 studied (49%) in sample 2. Pregnancy rates after treatment per herd ranged from 0-100% across the herds. Mixed logistic regression was used to calculate the odds ratio (OR) and to take into account both individual and herd level variables for each sample. In the first sample, multiparous cows were more likely to become pregnant after synchronization treatment than primiparous cows (OR = 2.4, P < 0.001). The following individual variables also influenced the response to synchronization: body weight at implant insertion (OR = 1.006, P = 0.017) and calving difficulty (OR = 0.33, P = 0.008). In the second sample, results varied with the year of data collection (OR = 3.46, P = 0.016) and with two herd-level variables: presence of a bull (OR = 0.48, P = 0.047) and type of housing (OR = 2.5, P = 0.004). In conclusion, the results after synchronization depended on both herd-level and individual variables and it was necessary to take into account two levels of factors to reduce variability after treatment.
Ponsart
C
C
Laboratoire d'épidémiologie et gestion de la santé animale, Ecole nationale vétérinaire Alfort, France.
Sanaa
M
M
Humblot
P
P
Grimard
B
B
Jeanguyot
N
N
Ponter
A A
AA
Viel
J F
JF
Mialot
J P
JP
D000818:Animals; D002417:Cattle; D004971:Estrus; D005260:Female; D005602:France; D007314:Insemination; D008297:Male; D016017:Odds Ratio; D010298:Parity; D011247:Pregnancy; D018873:Pregnancy Rate; D011270:Pregnancy, Animal / Q000502:physiology*; D012044:Regression Analysis