Classification and regression tree analysis to predict calving ease in Sussex heifers using pelvic area dimensions and morphological traits

Objectives: The objective of this study was to assess the relationship between pelvic measurements viz pelvic width (PW), pelvic height (PH) and pelvic area (PA), and linear body measurement traits viz body weight (BW), shoulder height (SH), chest depth (CD), Hindquarters width (HW), rump length (RL), hip height (HH), body length (BL) and also calve birth weight (CBW) under different calving ease scores viz no assistance, gently pull and hard pull. Material and methods: A total number of fifty-one first calf Sussex heifers at 24 months old, weighing approximately 450 kg were used for this study. A number of two, two-year-old bulls, weighing approximately 800 kg were used for mating the fifty-one heifers with a bull to cow ratio of (1:30 and 1:21). The fertility of bulls was assessed by a private veterinarian before the mating season. Calving ease was scored as follows: 1 = no assistance during parturition (normal), 2 = heifer assistance as gently pull, 3 = heifer assistance as hard pull, 4 = heifer cannot calf, 5 = heifer calved a dead calf, and 6 = heifer calf with abnormal position. Results: Descriptive statistics indicated that PH (p < 0.01) and RL (p < 0.05) were significant different among calving ease scores. Correlation findings for no assistance score revealed that CBW was positively significantly correlated (p < 0.05) PH and low significant (p < 0.01) with HW, HH, RL, PW, CD and SH, respectively. CART results demonstrated that HH and PH play an important role in predicting calving ease on Sussex heifers. Conclusion: The findings suggest that there is a relationship between pelvic areas and linear body measurements. This study might help farmers during breeding to lower incidents of dystocia during parturition. However, further studies need to be done in CART modelling with the main aim of reducing dystocia in Sussex heifer or larger sample size. [J Adv Vet Anim Res 2021; 8(1.000): 164-172]