A new application of pelvis area data as culling tool to aid in the management of dystocia in heifers1

Abstract

Although fetomaternal disproportion is the major cause of dystocia in heifers, pelvis area (PA) is not recommended as a culling tool due to its relatively low importance and genetic correlation with calf birth weight (BWT), the most important factor associated with dystocia. The objective of this observational study of 484 limited bred yearling beef heifers was to compare the effects of different methods of adjustment of PA data for culling to select against dystocia. Multivariable analyses were used to determine predictors of PA, calf BWT, and dystocia. Hypothetical culling rates of 10 and 20% were then applied after ranking heifers by each of the following: unadjusted PA, PA adjusted to 365 d of age by subtracting 0.27 cm 2 per day of age difference between each heifer's age and 365 d (APA), PA:prebreeding BW ratio (PA:BW), PA adjusted to the median BW of the group using the regression coefficient of PA on BW within age group (BWPA), and PA similarly adjusted to the median lean BW (LBWPA). Dam parity, sire, prebreeding age, prebreeding BW, and prebreeding BCS were associated with PA whereas dam parity, sire, own BWT, PA, AI bull, and calf gender were associated with calf BWT (P < 0.05). Dam parity, calf BWT, and either BWPA or LBWPA were the only independent predictors of dystocia (P < 0.05). Adjusting PA to BW or lean BW (LBW) improved the sensitivity and specificity to predict dystocia. After hypothetical culling by PA, retained heifers were heavier and had a higher calving rate and calves tended to be heavier at birth compared to culled heifers, but dystocia rates were not different. Culling by APA resulted in similar effects, except that dystocia rate tended to be lower in retained heifers. Culling by PA:BW resulted in lower dystocia rate in retained than in culled heifers, but retained heifers had lower prebreeding BW than culls. Culling by BWPA and LBWPA resulted in lower proportions with dystocia and a tendency towards higher calving rates in the retained heifers, without affecting the prebreeding BW or calf BWT. It is concluded that pelvimetry is a useful culling tool to aid in the management of dystocia in yearling heifers and that adjustment of PA to median BW or LBW within age group improves its accuracy and avoids the undesirable side effects.

Evaluation of pre-breeding reproductive tract scoring as a predictor of long term reproductive performance in beef heifers

“…The farming system and breed type have been described previously (Paterson et al, 1980, Schoeman and Jordaan, 1998, Holm et al, 2008, 2009, 2014. In brief, the Bovelder is a South African composite beef breed, and Johannesburg Water Northern Farm is a semi-intensive system using irrigated ryegrass, kikuyu and clover pastures with additional maize or sorghum silage.…”

Ultrasonographic reproductive tract measures and pelvis measures as predictors of pregnancy failure and anestrus in restricted bred beef heifers

“…The farming system, breed and location have been described previously [5,7,20,[23][24][25]. Farm data collected included the following: birth weight and birth date, parity of dam, sire, bull allocated and first to fourth AI day numbered from the mating start date (MSD).…”

“…The interpolar length of the left and right ovaries, the diameter of the left and right ovaries at the deepest point (2008 cohort only), the presence and diameter of a CL, the diameter of the largest follicle and diameter of the left uterus horn near the base (UD) were recorded. Finally internal vertical diameter (VD) and transverse diameter (TD) of the pelvis were measured by transrectal placement of a 5 caliper type pelvimeter (Rice pelvimeter, Lane Manufacturing, Denver, Colorado) [20,28,29]. Farm management and staff were blinded to all the measured pre-breeding data throughout the trial, except for the pre-breeding BW.…”

“…Maximum follicle diameter is correlated with uterus, cervix and vaginal diameter, and increases in the 10 weeks prior to first ovulation in heifers, due to increased LH pulse frequency [13,[15][16][17][18][19]. Larger pelvis area has been associated with early onset of puberty in heifers and improved libido in bulls [20][21][22].…”

Analysis of the relationship between insulin-like growth factor 1 receptor gene polymorphisms in Montbeliarde cows and the birth weight of their calves

“…The body weight of the cow is associated with the stature, and has a direct impact on the course of parturition (larger cows tend to have a larger area of pelvic canal) and the weight of the calf at birth, which next to nutrition has a significant impact on daily gains of calves during rearing (Nogalski and Mordas 2012). The pelvis size does not increase together with the increase of the cow's weight but is rather constant and cannot be adjusted by environmental conditions (Holm et al 2014). Therefore, selecting an appropriate time of the first fertilization may probably be important, and according to Wathes et al (2014) it can also affect the length of maintaining cows in the herd and reduce the possibility of conception complications.…”