The incidence of difficult calvings in the beef cattle in the Slovak Republic

© Slovak University of Agriculture in Nitra Faculty of Agrobiology and Food Resources


Introduction
Calving difficulty is considered very important reproduction trait.It affects the economics of the breeding directly through costs for the labor and veterinarian assistance and indirectly through the consequent production and fertility of the cow and calf (López de Maturana et al., 2007, Atashi et al., 2012).The incidence of the difficult calvings varies across the populations.According to De Amicis et al. (2018) incidence of difficult calvings is more frequent in dairy cattle.In the beef cattle authors reported 6.6% and 6.2% of difficult calvings in Charolais and Hereford primiparous cows (Eriksson et al., 2004), 3.7% of difficult calvings in Canadian Simmental (Jamrozik and Miller, 2014).It was showed that difference in incidence exists between primiparous and multiparous cows (Fuerst and Egger-Danner, 2003).Some authors Mõtus et al. (2017), Juozaitiene et al. (2017) even reported increased incidence of difficult calvings after the second one.
In the Slovak Republic the calving difficulty in beef cattle is part of the performance recording, however, these data are not used in the genetic evaluation.This study presents the first insight into the data in order to make further decisions on its use.

Materials and methods
The data on beef cattle performance recording are collected by the Breeding Services of the SR, s.e, and provided to the Institute of Animal Production Nitra on regular basis.In this study the data on 288,346 calvings in 5 major Slovak populations (Charolais, Limousine, Slovak Simmental, Pinzgau, Beef Simmental) during the period 1990-2017 were exploited.The calvings of twins were excluded from this analysis.
The recording of the calving difficulty in the Slovak Republic is based on the four-point scale with 1 referring to easy calving (no assistance needed) and 4 referring to caesarian section, and with additional category 0 referring to unobserved calving.Based on the practice the unobserved calvings (n = 19,383) were included in easy calvings category (Phocas and Laloë, 2004).Based on published findings (Carnier et al., 2000, Steinbock et al., 2003), distinction was made between the first and later calvings.Females, which gave first birth by the age of 3 years were considered heifers and females which gave consecutive birth (first birth record was available) were considered multiparous cows.There were 75,734 calvings, where the parity was doubtful.These were mainly cows with the first recorded birth at higher age, which could resulted from moving animals from dairy to beef herd, or abortion (not recorded).The incidence of difficult calvings according to sex (males, females), parity (heifers, cows) and season (spring, summer, autumn, winter) was tested by chi-square test within SAS software (Statistical Analysis System, Version 9.1, 2004).Since the large sample size was used and high significant levels were expected, the Cramers` V test was also applied to obtain strength of associations.

Results and discussion
The incidence of difficult calvings according to the breed of dam is summarized in Table 1.It is obvious that the most of the calvings were recorded as easy and overall only 4.9% of calvings required some form of assistance.When comparing the incidence of difficult calvings among the breeds (purebred) the lowest rate of calvings requiring assistance was observed in Limousine (5.1%).In other three breeds incidence of these calvings was similar (6.2-7.7%).The incidence of calvings requiring assistance was lower in all breeds when crossbred matings were compared.
Due to large sample size statistical significance of chisquare is doubtful.The Cramers` V test showed that there are only very weak associations between the difficulty of calvings and the sex of calves (0.028), parity (0.036) and season (0.011).Indeed, when comparing the calvings according to the sex of calves, only slight difference was observed between the births of males and females (5.43% vs. 4.22%).This observation is in agreement with findings, that the males are born heavier and incidence  of difficult calvings is higher in this group (Atashi et al., 2012, McHugh et al., 2014).
The similar pattern was observed when parity of calving was considered.Slightly higher incidence of the difficult calvings was observed in heifers (6.52%) compared to multiparous cows (4.4%).Higher incidence of difficult calvings in heifers was similar to those reported in beef populations by Eriksson et al. (2004).Higher rates of assisted calvings in beef populations were reported by Phocas, F. and Laloë, D. (2004).
Negligible difference in the incidence of difficult calvings among seasons was observed.Authors (Uematsu et al., 2013; Mekonnen and Moges, 2016) reported higher incidence of difficult calvings in the winter and spring period.However, this was not observed in our study.Moreover, the lowest incidence was observed in the winter.This could result from keeping the beef cattle in barns during this period and allowing better control during calvings.

Conclusions
The overall incidence of 4.9% was observed in the 5 major populations in the Slovak Republic.Slight differences in the incidence were observed among the breeds.Also only slight differences in the incidence were observed between the difficult calvings and the sex of calves, parity and season of the calving.Further analysis including other smaller beef populations and analysis of herd management on the calving difficulty will follow.