Elsevier

Livestock Science

Volume 135, Issues 2–3, February 2011, Pages 257-264
Livestock Science

Risk factors and rates of perinatal and postnatal mortality in cattle in Switzerland

https://doi.org/10.1016/j.livsci.2010.07.022Get rights and content

Abstract

There have been many studies on perinatal and postnatal mortality in calves, but most are limited to small numbers of breeds or herds. The goal of this study was to determine the perinatal (first 24 h) and postnatal mortality rates during the first four months in 22 breeds and cross-breeds commonly occurring in Switzerland and to identify possible risk factors. From 2005 to 2007, 2,122,184 calvings were analysed, which yielded an overall perinatal mortality rate of 2.4%. There was a significant yearly increase in the mortality rate. The postnatal mortality rates from days 2 to 7, 8 to 28 and 29 to 120 were 0.5%, 1.3% and 0.7%, respectively. Dystocia was associated with a relative risk of perinatal mortality of 12.2, and significantly affected the postnatal mortality rates in all time periods investigated. The overall dystocia rate associated with bull calves was more than twice that of heifers, but there was no sex-related difference in Dexter, Hereford, Highland cattle, Hinterwälder, Jersey und Normande breeds. There were significant correlations between the mean birth weights of the different breeds and the dystocia rate (r = 0.6), and between the mean difference in male and female birth weights of the different breeds and the dystocia rate (r = 0.6). Perinatal mortality was also significantly affected by age of dam, gestation length, sex and weight of calf, season and herd size. Breed had a significant effect on perinatal and postnatal mortality rates, and there were significant interactions between breed and other risk factors of mortality. The identification of breed-specific risk factors of perinatal and postnatal mortality could help to develop strategies to alleviate the problem.

Introduction

In cattle the perinatal and early postnatal periods are characterised by high mortality rates. The definition of perinatal mortality varies among studies but the term generally refers to the mortality of full-term calves at parturition and up to 24 or to 48 h after birth (Gulliksen et al., 2009, Lombard et al., 2007, Mee, 2008). Perinatal calf mortality rates generally vary from 2% to 10% (see Mee, 2008 for review). It is possible that the large variation is caused, at least in part, by different methods of recording perinatal mortality. In some European countries, recording is mandatory and occurs at a national level, whereas in others it is only done by milk marketing boards, breeding companies or veterinary practices. However, regardless of the recording methods used, mortality rates have increased over the last few years in the United States as well as in several European countries (Berglund et al., 2003, Hansen et al., 2004, Mee, 2008, Meyer et al., 2001, Steinbock et al., 2003). In addition, mortality rates of calves up to the age of six (3%; Gulliksen et al., 2009) or seven months (4%; Svensson et al., 2006) are higher than those of older cattle.

Various genetic and non-genetic factors of perinatal and postnatal mortality have been identified (Gulliksen et al., 2009, Gundelach et al., 2009, Johanson and Berger, 2003, Lombard et al., 2007, Mee, 2008). Dystocia is a factor that has been consistently identified as the primary cause of perinatal mortality (Heins et al., 2006, Meyer et al., 2001). An increase in the dystocia rate has also been reported in Switzerland (Bleul, 2008), although rates for both heifers and cows were slightly lower than those reported in the literature (6.0% versus 8.0% and 3.5% versus 4.5%, respectively; Steinbock et al., 2003). Dystocia rates may vary among different cattle populations studied, and it should also be noted that the definition of dystocia is not uniform among different studies. There are considerable differences in dystocia rates among different cattle breeds (Bleul, 2008). Most published studies have been limited to single breeds or cross-bred cattle involving a small number of breeds (Berglund et al., 2003, Bicalho et al., 2007, Heins et al., 2006, Linden et al., 2009, Mee, 2008, Meyer et al., 2001, Steinbock et al., 2003), which could account, at least in part, for the discrepancy among reported mortality rates. In small studies, the effects of local production and management factors are difficult to separate from those of genetic factors.

Perinatal mortality rates vary widely among individual herds; the one-year mortality rate ranged from 0 to greater than 25% in a study involving 125 herds of predominantly Norwegian Red dairy cows (Gulliksen et al., 2009), and from 0 to 31% in a study involving 250 Holstein herds (Fourichon et al., 2001). This illustrates the difficulty in comparing perinatal mortality rates among studies that involve different herd management systems and different breeds of cows.

In the present study, an attempt was made to show the effects of genetic and non-genetic factors on perinatal and postnatal mortality by analysing all calf births from all cattle herds in Switzerland. The purpose of the large number of herds included in the study was to minimise management effects, which has not been achieved in many previous similar studies. A secondary objective of the study was to quantify the effect of breed on calf mortality during the perinatal period and up to 4 months of age. To the author's knowledge, this has not been investigated in previous studies using such large numbers of cows of different breeds.

Section snippets

Population

In Switzerland slightly more than 20% of cattle herds are in alpine regions. Most dairy herds use a combination of tie stalls and yards, whereas most beef herds are kept in free stalls. Eighty percent of cows are artificially inseminated and approximately 50% of frozen semen is imported. All births of calves are registered in a central database (www.tierverkehr.ch); births in 2005, 2006 and 2007 were analysed in the present study. Recorded data included date of birth, sex and breed of the calf,

Time of calf loss

The overall perinatal mortality rate was 2.4% (n = 51,429); 71.6% of these calves were stillborn and the remainder died within 24 h of birth. The overall perinatal mortality rate increased from 2005 (1.8%) to 2006 (2.7%) and to 2007 (2.8%; P < 0.0001), although it did not change during the study period in cattle of the Angus, Dexter, Galloway, Hereford, Highland cattle, Normande, Piemontese, Red Holstein and Belgian Blue breeds.

The seasonal incidence of calvings was 31.1% in autumn, 27.5% in winter,

Discussion

Perinatal mortality has been identified as a growing problem in different parts of the world (Berglund et al., 2003, Mee, 2008, Meyer et al., 2001, Steinbock et al., 2003). An overall increase in perinatal mortality from 1.8% in 2005 to 2.8% in 2007 was also documented in the present study. However, these rates were lower than those reported for Holstein calves in studies from Sweden and the USA. In the Swedish study, perinatal mortality of calves born to first- and second-parity Holstein cows

Conclusion

The perinatal mortality rates of calves reported from different regions of the world as well as from different herds within a country vary widely. This means that the rate depends on many factors that may be specific to the population investigated. In the present study, which involved a large number of calf births from 22 breeds in Switzerland, several risk factors of perinatal and postnatal mortality were identified. In addition, perinatal mortality rates were much lower compared with similar

Acknowledgement

The author would like to thank the Tierverkehrsdatenbank for access to their database.

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