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Comparative aspects on genetics of stillbirth and calving difficulty in Swedish dairy cattle breeds

Steinbock, Lena (2006). Comparative aspects on genetics of stillbirth and calving difficulty in Swedish dairy cattle breeds. Uppsala : Sveriges lantbruksuniv.
ISBN 91-576-7151-6
[Licentiate thesis]

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The stillbirth rate in first-calvers in the Swedish Holstein (SLB) dairy cattle population has increased. At later calvings in SLB, and in the other main Swedish dairy breed, the Swedish Red and White (SRB), by contrast, there has been little change in stillbirth rates over the last two decades. The overall objective of this study was to investigate and compare genetic variation in the calving traits of these two breeds, and to propose improved methods by which to select for a reduction in calving problems. The SLB heritabilities were 3-6% for stillbirth and calving difficulty at first calving. At second calving they fell to below 1%. In SRB the heritabilities were lower, at 0.5-2%, and the difference between first and second calvings was less pronounced. The heritabilities for direct effect were always slightly higher than those for maternal effect. Genetic correlations between direct and maternal effects were in all cases close to zero. In SLB a large variation (3-16%) was observed in the stillbirth rate of sires and maternal grandsires. Approximately half the genetic variation in stillbirths remained after adjusting for calving difficulty. In SLB the genetic correlations between parities for stillbirth and calving difficulty were medium-high (0.4-0.5). Thus stillbirth and calving difficulty at first calving cannot be considered the same traits in heifers and cows. In SRB the genetic correlations between first- and second-calving results were high (0.7-0.8). Here, therefore, stillbirth and calving difficulty are determined to a much greater extent by the same factors and genes at first and later calvings. Thus although the two breeds differ genetically from each other at first calving, at second calving there are no obvious differences. In both breeds bulls should be evaluated both as sires and maternal grandsires, and both stillbirth and calving difficulty should be included in the genetic evaluations. In SLB it is unlikely that the accuracy of a bull’s estimated transmitting ability (ETA) can be increased by including information from second calving. In SRB, on the other hand, the accuracy of breeding values will be considerably improved by using information from both calvings. A bivariate or a repeatability model would be equally appropriate here. In the SLB study we concluded that heritabilities from linear analyses adjusted from the visible to the underlying scale corresponded well with those directly estimated by threshold models. For SRB, threshold analyses were unsuccessful as a result of the low incidences and low heritabilities in the calving traits. At present, therefore, there is no reason for using a more time-consuming method that also is very sensitive to the structure of the data. The studies reported here indicate that heifers of both breeds should be at least 24 months at calving, as this will minimise the rates of stillbirth and calving problems. For the same reason, it would be advantageous to encourage calvings in late summer or early autumn.

Authors/Creators:Steinbock, Lena
Title:Comparative aspects on genetics of stillbirth and calving difficulty in Swedish dairy cattle breeds
Year of publishing :April 2006
Number of Pages:22
ALLI. Steinbock, L., Näsholm, A., Berglund, B., Johansson, K. and Philipsson, J. 2003. Genetic effects on stillbirth and calving difficulty in Swedish Holsteins at first and second calving. J. Dairy Sci. 86; 2228-2235. II. Steinbock, L., Johansson, K., Näsholm, A., Berglund, B. and Philipsson, J. 2006. Genetic Effects on Stillbirth and Calving Difficulty in Swedish Red and White Dairy Cattle at First and Second Calving. (Submitted).
Place of Publication:Uppsala
ISBN for printed version:91-576-7151-6
Publication Type:Licentiate thesis
Full Text Status:Public
Agrovoc terms:dairy cows, dairy cattle, bulls, parturition, foetal death, genetic parameters, breeding value, linear models, sweden
Keywords:stillbirth, calving dificulty, dairy cattle, genetic parameters, correlations between parities, calving age, linear and threshold models
Permanent URL:
ID Code:1082
Department:(VH) > Dept. of Animal Breeding and Genetics
Deposited By: Lena Steinbock
Deposited On:06 Apr 2006 00:00
Metadata Last Modified:02 Dec 2014 10:09

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