RELATIONSHIP BETWEEN CALVING COURSE AND CALF BODY WEIGHT AT BIRTH AND CALF/COW BODY WEIGHT RATIO

Tomasz Przysucha¹, Henryk Grodzki^2
1 Department of Animal Breeding, Faculty of Animal Science, University of Life Sciences - SGGW, Poland
² Faculty of Animal Science, Animal Breeding & Production Department, Cattle Breeding Division, University of Life Sciences - SGGW, Poland

ABSTRACT

The aim of the study was to estimate the relationship between calving course and calf body weight at birth and calf/cow body weight ratio for heifers and multiparous cows of the following beef breeds: Angus, Hereford, Limousin and Charolais. Data concerning 22 989 deliveries (6838 heifers and 16 151 multiparous cows) of the above mentioned breeds included calving course evaluation as well as information about calving number, calf body weight at birth and its sex. Relationship between calving course, breed, calving number, calf sex and calf body weight at birth (kg) and calf/cow body weight ratio (%) was examined. The frequency of difficult calvings depending on calf/cow body weight ratio was also investigated. The breed had significant influence on both examined traits. Charolais calves were the heaviest whereas the Limousin ones – the lightest. Calf/cow body weight ratio was as follow: 6.29% (LMS),  6.50% (AAG), 6.49% (CHL) and 6.74% (HEF). Calf body weight at birth and calf/cow body weight ratio were influenced (P ≤0.01) by calving number and calf sex. Highly significant relationships between calf body weight at birth, calf/cow body weight ratio and calving course were observed. For all the breeds the share of difficult calvings was higher when calf/cow body weight ratio increase. Thus, calf/cow body weight ratio seems to be useful for calving course estimation in breed comparisons.

Key words: beef breeds, calving course, calf/cow body weight ratio.

INTRODUCTION

Calving course of beef breed cows depends on many factors, among which (beside breed, calving number, calf sex) body weights of cow and calf at birth are always listed [2,10,11,12,13,14]. The influence of the above mentioned factors on difficult calving frequency is widely reported [3,6,8,9], however there are few papers considering calf/cow body weight ratio as a factor. The aim of the study was to estimate the relationship between calving course and calf body weight at birth and calf/cow body weight ratio for heifers and multiparous cows of the following beef breeds: Angus, Hereford, Limousine and Charolaise.

MATERIAL AND METHODS

The data base of the Polish Beef Cattle Breeders & Producers Association concerning recording results of Angus (AAG), Charolaise (CHL), Hereford (HEF), Limousine (LMS) in the years 1995-2004 was analysed. Data concerning 22 989 deliveries (6838 heifers and 16151 multiparous cows) of the a/m breeds included calving course evaluation (A – easy or with a little assistance, B – difficult, with assistance of a vet. or mechanical means) as well as information about calving number (1st, 2nd and further), calf body weight at birth and its sex. Relationships between calving course, breed, calving number, calf sex and calf body weight at birth (kg) and calf/cow body weight ratio (%) were examined by analysis of variances method using SPSS software [1]. Pearson's χ² test was used to determine frequency of difficult calvings in relation to calf/cow body weight ratio (≤5%; 5.1–5.5%; 5.5–6.0%; 6.1–6.5%; 6.6–7.0%; 7.1–7.5%; > 7.5%).

RESULTS AND DISCUSSION

The influence of chosen factors on calf body weight at birth as well as calf/cow body weight ratio was presented in Table 1. The breed significantly influenced both investigated traits. Charolaise calves were the heaviest, whereas limousine ones – the lightest. For Angus and Hereford (breeds of rather small caliber) calf/cow body weight ratio was the highest 6.50 and 6.74%), whereas for Charolais and Limousin – the lowest. The heaviest calves were delivered by the heaviest Charolaise cows, but their body weight comparing to their mothers' body weight is relatively low. In spite of that, the frequency of difficult calving is higher than in the other breeds. According to American sources the main breeder's goal should be obtaining of  a calf weighting in average 7% (heifers) to 9% (multiparous cows) of its mother's body weight [7]. Calf body weight at birth and calf/cow body weight ratio were influenced (P ≤ 0.01) by calving number. Calves delivered by the heifers were by 1.7 kg lighter than the ones delivered by multipara, but calf/cow body weight ratio was higher by 0.66% in heifers. It results from the fact, that 2 years old  heifers weight about 85% of the mature cows of the breed, and often deliver calves as big as the ones delivered by the older cows. Consequently the possibility of difficult deliveries is much higher [4,5]. Calf sex had a significant (P ≤ 0.01) influence on both analysed traits. Born males were heavier by 1.3 kg than females, and the ratio of their body weight to body weight of their mothers was higher by 0.22%. Calf body weight at birth and calf/cow body weight ratio high-significantly influenced calving course. The calves born with assistance of a vet. or mechanical means were heavier by 3.7 kg than those born easily or with a little assistance. The ratio of calf/cow body weight was higher by over 0.66%.

Table 2 shows the influence of chosen factors on interaction between calf weight at birth and calf/cow body weight ratio. All investigated interactions were statistically significant (P ≤ 0.01). The primiparous cows of all breeds delivered calves lighter by 1.88 kg (AAG), 2.46 kg (CHL), 0.94 kg (HEF) and 1.45 kg (LMS) than the older ones, but calf/cow body weight ratio was higher for heifers by 0.78; 0.57; 0.70 and 0.61% respectively. Beside less developed reproductive tract of the heifers, that high calf/cow body weight ratio is probably the main reason of  a bigger frequency of difficult calvings in comparison with multipara. Calves born in difficult deliveries were heavier by 6.42 kg (AAG), 2.66 kg (CHL), 4.23 kg (HEF) and 1.65 kg (LMS). Body weight ratio was higher by 1.15; 0.18; 0.96 and 0.37% respectively in case of deliveries with assistance of a vet. or mechanical means than born easily. Male calves were born heavier than female calves both in heifer group and multiparous cows, and the ratio of their body weight to body weight of their mothers was higher than of female ones. Calves born in difficult deliveries were heavier by 3.91 kg than the ones born easily. In multiparous cows this difference amounted to 3.57 kg. In case of difficult calving calf/cow body weight ratio was respectively higher by 0.70 and 0.63% for heifers and multipara. The frequency of difficult calvings depending on calf/cow body weight ratio is presented in a graph (Fig.1). The difficult calvings and the range of calf/cow body weight ratio was close to linear. The share of difficult calvings increased along with calf/cow body weight ratio. Other authors indicate the same tendencies [3,6,8]. 

CONCLUSIONS

The results obtained indicate, that beside of calf body weight, calf/cow body weight ratio had a big influence on calving ease. Calf/cow body weight ratio seems to be useful for comparing calving course in different breeds.

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Accepted for print: 4.08.2008

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