Pelvic growth, calf birth weight and dystocia in Holstein x Hereford heifers.
The pelvic area was measured in 129 Holstein x Hereford heifers at 10, 16 and 22 months of age. The heifers were fed an all forage diet. Pelvic growth was not linear over time, changing from an increase of 0.27 +/- 0.2 cm(2)/day during the first 6 months of the study to 0.13 +/- 0.13 cm(2)/day during the last 6 months (P<0.01). The relationship of pelvic area to body weight, height at hooks, and distance from hooks to pins did not change with age, and a moderate correlation between the pelvic area and these other measures (R=0.20 to 0.80) was noted. The pelvic area was measured within 24 hours after calving in 76 of the heifers. The rate of increase of pelvic area/day increased significantly (P < 0.01) in the month prior to calving from 0.14+/-0.13 cm(2) to 1.15 +/- 0.88 cm(2). As a result, the pelvic area at calving had a moderate correlation (R=0.29 to 0.52) to the pelvic area prior to calving. Logistic regression and discriminant analysis techniques were used to model the influence of the pelvic area and calf birth weight on the incidence of dystocia. Ratio of the pelvic area at calving to calf birth weight significantly (P < 0.01) influenced the incidence of dystocia. Logistic regression techniques were not superior to discriminant analysis; both correctly predicted 73% of the cases. Pelvic area measurement at any time other than calving was not associated with dystocia (P >0.05). Pelvic area and calf birth weight are important determinants of dystocia in heifers. The high degree of variation noted in pelvic growth, in particular during the month prior to calving, resulted in low correlation between pelvic area at calving and the precalving measurement. Therefore, we were not able to predict dystocia by measuring the pelvic area prior to calving.
Gaines
J D
JD
School of Veterinary Medicine, University of Wisconsin-Madison USA.
Peschel
D
D
Kauffman
R G
RG
Schaefer
D M
DM
Badtram
G
G
Kumi-Diaka
J
J
Clayton
M K
MK
Milliken
G
G