Evaluation of the effect of cow exterior on calf size at parturition

Article Details: Received: 2020-09-29 | Accepted: 2020-11-27 | Available online: 2021-01-31 https://doi.org/10.15414/afz.2021.24.mi-prap.20-24 The aim of this research was to evaluate the effect of cow exterior on the weight of the calf at parturition and the size of the calf’s head. 453 purebred Holstein Friesian dairy cows at a selected farm were analysed within this research, and the measurements of the withers height, hip width, backside width and ischial width were taken from each specimen. Considering the calves, the measurements taken were the width and length of the head and weight at parturition. The research did not prove any significant (p>0.05) effect of the cow body conformation on any of the measured proportions of the calf. There was, however, a significant (p<0.05) difference in the head length and weight in calves in relation to the calving ease. As opposed to our expectations, the parturition weight of calves going through a more difficult parturition was lower (30.36 kg, as opposed to 36.57 kg in the less difficult parturition) and the length of the head was lower as well (23.47cm, as opposed to 23.98 cm in a less difficult parturition). At the same time, the weight and head length increased with each undergone lactation cycle of the mother – more specifically, this trend of increasing was observed from the first to the fifth lactation cycle. The parturition weight of calves was significantly affected by the gestation length itself. Another factors that had an effect on the weight and size of the calves were the season during which calving took place and the effect of the father bull. The results show a possibility of using the data collected in this research for breeding value estimation in difficult parturitions, since the effect of the father of the calf has to be taken into consideration as well as the effect of the the cow’s father. Keywords: Holstein, Width, Weight, Exterior, Calving References BURES, D. et al. (2008). Calving difficulty as related to body weights and measurements of cows and calves in a herd of Gascon breed. Czech Journal of Animal Science , 53(5), 187-194. DOI: https://doi.org/10.17221/312-CJAS DHAKAL, K. et al. (2013). Calf birth weight, gestation length, calving ease, and neonatal calf mortality in Holstein, Jersey, and crossbred cows in a pasture system. Journal of Dairy Science , 96, 690–698. DOI: https://doi.org/10.3168/jds.2012-5817 KERTZ, A. F. et al. (1997). Body  Weight,  Body  Condition  Score,  and  Wither  Height of  Prepartum  Holstein  Cows  and  Birth  Weight  and Sex  of  Calves  by  Parity:  A  Database  and  Summary. Journal of Dairy Science , 80, 525–529. LINDEN, T. C. et al. (2009). Calf birth weight and its association with calf and cow survivability, disease incidence, reproductive performance, and milk production. Journal of Dairy Science , 92, 2580–2588. DOI: https://doi.org/10.3168/jds.2008-1603 NOGALSKI, Z. (2003). Relations between the course of parturition, body weights and measurements of Holstein-Friesian calves. Czech Journal of Animal Science , 48(2), 51–59. NUGENT, R. A. et al. (1991). Body measurements of newborn calves and relationship of calf shape to sire breeding values for birth weight and calving ease. Journal of Animal Science , 69, 2413–2421. DOI: https://doi.org/10.2527/1991.6962413x VOSTRÝ, L. et al. (2015). Genetic relationships among calving ease, birth weight and perinatal calf survival in Charolais cattle. Animal Science Papers and Reports , 33(3), 233–242.

The aim of this research was to evaluate the effect of cow exterior on the weight of the calf at parturition and the size of the calf's head. 453 purebred Holstein Friesian dairy cows at a selected farm were analysed within this research, and the measurements of the withers height, hip width, backside width and ischial width were taken from each specimen. Considering the calves, the measurements taken were the width and length of the head and weight at parturition. The research did not prove any significant (p >0.05) effect of the cow body conformation on any of the measured proportions of the calf. There was, however, a significant (p <0.05) difference in the head length and weight in calves in relation to the calving ease. As opposed to our expectations, the parturition weight of calves going through a more difficult parturition was lower (30.36 kg, as opposed to 36.57 kg in the less difficult parturition) and the length of the head was lower as well (23.47 cm, as opposed to 23.98 cm in a less difficult parturition). At the same time, the weight and head length increased with each undergone lactation cycle of the mother -more specifically, this trend of increasing was observed from the first to the fifth lactation cycle. The parturition weight of calves was significantly affected by the gestation length itself. Another factors that had an effect on the weight and size of the calves were the season during which calving took place and the effect of the father bull. The results show a possibility of using the data collected in this research for breeding value estimation in difficult parturitions, since the effect of the father of the calf has to be taken into consideration as well as the effect of the the cow's father. Original Paper the pelvis and head measurements were taken with a pair of measuring compasses. The weight of the animals was measured through digital weighing scales designated for animal weighing.

Keywords
The effect of each factor on the body conformation of new-born calves was tested through the GLM method (SAS software) using the following model equation: where y is the dependent variable (calf weight, calf head width or length), and b1-b5 are the regression coefficients showing the relation of y to the gestation length (ges), withers height (wheight), hip width (hwidth), backside width (bwidth) and ischial width (iwidth). As the categorical variables there is the calving ease (ce, 3 levels), used breeding male -the calf's father (bull, 30 levels), the effect of the calving season (cs, 5 levels), the number of lactation cycle (lac, 6 levels) and the effect of the calf sex (sex, 2 levels: 1, bull -47%, 2, heifer -53%). The calving season consists of the month of parturition (the months are grouped into 4 seasons -December to February, March to May, June to August and September to November) and the year of parturition.
The subsequent statistical evaluation of the differences in averages of the levels of each factor entered into the GLM was done through the Tukey-Kramer method. To set the regression coefficients, or correlation between the factors, the REG procedure, or more precisely the CORR procedure in the SAS software, was used.

Results and discussion
The analysed herd of 453 Holstein Friesian cows had the average pregnancy length of 278.05 days. The average withers height of a cow was 146.39 cm, the average hip width was 55.18 cm, average backside width was 49.54 cm and average ischial width was 43.85 cm ( Table 1). The average calf weigh was 35.62 kg, the calf head length was 24.35 cm and width 10.13 cm on average. The analysed herd was large enough, which has been proven by the low standard error value in all the analysed values. The highest variability coefficients (CV) were found in the data about new-born calf weight (CV = 17.93%), which is caused by the big span of weights in the calves. A quite high variability was also found in the backside width of cow (CV = 13.12%), mainly as opposed to the hip width (CV = 5.07%). The lowest variability (CV = 1.73%) was found in the gestation length, where the majority of cows went into calving a week earlier than is usually stated for a gestation length in cattle. Similar values in gestation length are stated for example by Dhakal et al. (2013). Kertz et al. (1997) Dhakal (2003) states this value to be 39.6 kg and the calf head width to be 11.4 cm on average. The significance of the effect of each factor on the calf weight and head size is shown in Table 2. As of the calf head length, a statistically significant relation of this measurement to the calving ease (p <0.05), to the calf's father, to the season in which calving took place, and the number of lactation cycles the mother had undergone before (p <0.01) was proven. A similar relation was found between the head width and the previously stated factors. From the factors analysed by this study, the calf birth weight (p <0.05) was mainly affected by the choice of a father, the season in which the calving took place, the number of lactation cycles the mother had undergone before and the gestation length. The parturition weight is also closely tied to the calving ease (p <0.05). Our research has not proven any significant (p <0.05) effect of the analysed measurements of the cow and the calf's sex on the calf weight and head size. Similar results were reported by Dhakal et al. (2013), Kertz et al. (1997) and Nugent et al. (1991). The differences in averages according to the categorical variables (calving ease, calving season, parity, and sex) and their probabilities are stated in Table 3. The calf head size (length and width) closely corresponded with the calving ease. The research found a provable difference (p <0.05) between the average head size in parturitions graded as difficulties 1 and 2. As of the complicated parturitions (grade 3), no significant relation between the head size and the calving ease has been proven. However, an interesting fact arose -the more difficult parturitions occurred in calves with lower weight and smaller head size.
As of the effect of the calving season, the research shows that during the summer and autumn months, the calves were born with significantly (p <0.05) lower head width (9.63 in summer, 9.77 in autumn months). As of the head length, a significant (p <0.05) difference was found between the December-February 2015 season (20.92 cm) and the rest of the seasons, where the calf head length was 3 to 4 cm higher.
The lowest birth weight and smallest head sizes were recorded at calves born from the cows going into their first parity. The research found that with each new lactation cycle there was a significant (p <0.05) increase of the calf head length and width, as well as an increase of the birth weight. This trend stopped at the cows going into their 6 th to 9 th lactation cycle, where an insignificant (p >0.05) decrease of the birth weight, as well as a decrease of the size of the calf head, took place.
The relation of exterior measurements of the mother and those of calf can be described by the correlation coefficients (Table 4). The highest correlation coefficient value (r = 0.4036) was found between the calf head length and the mother's hip width. A strong relation was proven only between the hip width and backside width (r = 0.7544) and a mid-strength relation was observed between the hip width and ischial width (r = 0.6765) and between the calf head length and width (r = 0.5378).

Conclusions
The results show that the pelvis size of the cow has no significant effect on the birth weight and head size of the calf.
However, there appears to be a relation between the calving ease and the weight and head size of the calf. A significant impact of the calf's father, the calving season, and the number of lactation cycles on the calf's size and weight has been proven in this research. As of the parturition weight, another key factor is the gestation length and mother's age. The results, as shown in this paper, point to a possibility of taking the new-born calves' weight and size into consideration during the breeding processes, as it might lead to less difficult calving.