The aim of this study was to estimate the perinatal and neonatal mortality rates from day 2 to 30 in Slovenian calves and to evaluate risk factors for increased losses. We analysed data on 1,333,765 calves of different dam breeds, born in Slovenia in the period from January 1 to December 31st, 2012. Data were obtained from the Central register of bovine animals. The average perinatal calf mortality, including abortions and stillbirths, was 5.57% and 2.68% from day 2 to 30. The most significant effects on perinatal calf mortality rate were the number of calves at calving, age of the dam at calving, the herd size, while herd size and calving season were the most influential in the following neonatal period from day 2 to 30. Calves from Holstein Friesian dams showed much higher perinatal and neonatal mortality rates than calves from Simmental, Brown and other dam breeds. With increased herd size, the perinatal and neonatal mortality rate increased. This increase was more pronounced in Simmental, Brown and other dam breeds than in Holstein Friesian dams

Marko Čepon

Mojca Voljč

Silvester Žgur

Špela Malovrh

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69Agriculturae Conspectus Scientifi cus . Vol. 82 (2017) No. 2 (69-73)ORIGINAL SCIENTIFIC PAPERSummaryTh e aim of this study was to estimate the perinatal and neonatal mortality rates from day 2 to 30 in Slovenian calves and to evaluate risk factors for increased losses. We analysed data on 1,333,765 calves of diff erent dam breeds, born in Slovenia in the period from January 1 to December 31st 2012. Data were obtained from the Central register of bovine animals. Th e average perinatal calf mortality, including abortions and stillbirths, was 5.57% and 2.68% from day 2 to 30. Th e most signifi cant eff ects on perinatal calf mortality rate were the number of calves at calving, age of the dam at calving, the herd size, while herd size and calving season were the most infl uential in the following neonatal period from day 2 to 30. Calves from Holstein Friesian dams showed much higher perinatal and neonatal mortality rates than calves from Simmental, Brown and other dam breeds. With increased herd size, the perinatal and neonatal mortality rate increased. Th is increase was more pronounced in Simmental, Brown and other dam breeds than in Holstein Friesian dams.Key wordscalf mortality rate, perinatal, neonatal, dam breedTh e Eff ect of Dam Breed on Calf Mortality in the First Month of Life in Slovenia Mojca VOLJČ ( )Marko ČEPONŠpela MALOVRHSilvester ŽGURUniversity of Ljubljana, Biotechnical Faculty, Department of Animal Science, Groblje 3, SI-1230 Domžale, Slovenia e-mail: mojca.voljc@bf.uni-lj.siReceived: April 29, 2017 | Accepted: July 27, 2017ACKNOWLEDGEMENTS The authors would like to thank the Msc. Marjana Drobnič from Animal Identification and Registration and Information System Division from Ministry of Agriculture, Forestry and Food for provided data.Agric. conspec. sci. Vol. 82 (2017) No. 270 Mojca VOLJČ, Marko ČEPON, Špela MALOVRH, Silvester ŽGURIntroductionGood reproduction performance is one of the most impor-tant factors of sustainable and profi table milk and beef produc-tion. Calf death represents economic loss and is also an indicator of poor animal welfare and health (Martin and Wiggins, 1973; Mee, 2008). For Norway, Østerås et al. (2007) computed total annual losses of approximately 10 million € due to dairy and beef calf mortality up to 6 months of age. In the UK up to 6% of all calves born die before 6 months of age and annual costs to dairy industry were estimated at around 70 million € (DEFRA, 2003). Meyer et al. (2001) estimated the probability for stillbirth around 10% for primiparous and 5% for multiparous Holstein cows which represented costs to the US dairy industry at more than 125 million $ annually. Nevertheless, a lost calf does not represent the present value of the calf alone, but also the loss of genetic potential for the herd improvement. Heinrichs and Radostis (2001) subdivided lost calves in four groups, depending on the age at time of death: abortions or prenatal losses (still-born calves from 40 and 270 days of gestation), perinatal losses (stillborn calves aft er 270 days of gestation as well as liveborn calves that died 24 hours aft er birth), neonatal losses (losses of calves between the 1st and 28th days of age) and other losses of calves between 1 and 6 months of age. Th e mortality rate de-creased with increased age, being the highest during perinatal time (Bleul, 2011, Fuerst-Waltl and Fuerst, 2010, Gates, 2013). Th e review of Mee et al. (2008) showed that perinatal mortality rate could vary from 2 to 10% and pointed out several risk fac-tors, which had been associated with increased mortality rate in cattle (dystocia, gestation length, foetal gender, breed, twin-ning, age at fi rst calving, primiparity, season of calving). Bleul (2011) and Gates (2014) reported diff erences among breeds and eff ects of herd size in Switzerland and the UK as well. Several studies showed an increased mortality rate in the last years (for review see Compton et al., 2017). Th e aim of the study was (1) to asses risk factors for in-creased calf losses in the fi rst month of age, and (2) to estimate the diff erences in mortality rates of calves among diff erent dam breeds in Slovenia. Material and methodsData were obtained from the Central register of bovine ani-mals in Slovenia. Records of 1,333,765 calves born in Slovenia from January 1st 2005 to December 31st t 2012 were analysed. Th e record for each calf comprised of the date of birth, sex, the number of calves born in the same calving, breed and age of the dam at calving and the size of the herd. Th e number of calves was defi ned as singletons, twins and triplets or more. Age of dams at calving was classifi ed into six classes: age < 2.5 years, 2.5 to < 3.5 years, 3.5 to < 4.5 years, 4.5 to < 5.5 years, 5.5 to < 6.5 years, age ≥ 6.5 years. Th e breed of dams was classifi ed as Holstein Friesian, Simmental, Brown and other breeds with cross-breds included. Th e calving season based on calf birth dates was classifi ed as spring (March to May), summer (June to August), autumn (September to November) and winter (December to February). Th e time of death of calf was classifi ed as perinatal (aborted, stillborn and death within 24 hours aft er birth) and as neonatal (from the day 2 to ≤ 30). Calves whose dams were younger than 14 months or older than 23 years at calving were excluded from the analysis. Th e fi nal data set for analyses in-cluded 1,333,647 animals.Th e mortality rate in each age group was computed accord-ing to the total number of calves born. We analysed data using the statistical program SAS / STAT (SAS 9.4), the procedure GENMOD (Generalised Linear Models, SAS, 2013). For the mortality rate in each age group, we assumed a binary distri-bution and used the logit(p)=log(p/1-p) link function. Risk fac-tors, the year of birth, the season of birth, the number of calves at birth, dam breed, and age of the dam at calving were includ-ed in the statistical model as fi xed eff ects and herd size as co-variate. Herd size was log transformed prior to the analyses. By using the ODDSRATIO option, we estimated the odds ratio. As we defi ned comparisons, odds ratio measures the ratio of odds (i.e. how many times the probability for death in the fi rst group is greater compared to the other group. Results and discussionMost of the analysed calves had Simmental dams, followed by Holstein Friesian, all other and Brown dams. Slightly more than one fi ft h of calves were born in herds with a size of ≤10 cattle or 10-20 cattle, whereas only 8% of calves originated from herds with more than 100 cattle. Great diff erences in herd size were found among dam breeds. Only 1.29% of Holstein Friesian dams belong to herds with ≤10 cattle and 30.57% to herds with more than 100 cattle. In the Simmental breed, the percentage was reversed, because 29.32% dams were from herds with ≤10 cattle and 1.72% from herds with more than 100 cattle. Th e distribu-tions of dams of Brown breed and other breeds were similar to the distribution of Simmental breed (Figure 1).Estimated calf mortality rate from Holstein Friesian dams in perinatal period was 8.08% and 4.28% in the neonatal period from day 2 to 30. Th is is consistent with the current prevalence of bovine perinatal mortality between 2% and 10% given by Mee et al. (2008). Bleul (2011) reported only 2.4% perinatal mortality rate for Switzerland, whereas Zucali et al. (2013) and Lombard et al. (2007) reported as much as 8.8% and 8.2% for Italy and Colorado. In Simmental, Brown and other breeds, the calf mor-tality rate was much lower than in the Holstein Friesian breed. Consequently, perinatal calf mortality rate was 1.7 and 1.6-times higher than in Simmental and Brown dams (Table 1). Th e diff er-ences in calf mortality rate in neonatal period were even higher. Th e multivariate logistic analysis (Table 2) showed that all in-cluded eff ects were statistically signifi cant (p<0.05).Th e most signifi cant eff ects (the highest Chi square value) on perinatal calf mortality rate were the number of calves at calving, age of the dam at calving and the herd size. In the fol-lowing neonatal period from the day 2 to 30, the most impor-tant risk factor was herd size, followed by calving season (Table 2). For the most of the calves died in the perinatal period, the breed of the sire was not known. Inclusion of this eff ect in the model would probably explain some addition variation in the calf mortality rates.Th e comparison among dam breeds in calf mortality rate in the perinatal period as well as in the neonatal period until 30 days of age exhibited statistically signifi cant diff erences among all dam breeds (p<0.05), except the diff erence between Brown and other breeds. Th e likelihood of calf death in the perinatal Agric. conspec. sci. Vol. 82 (2017) No. 271The Effect of Dam Breed on Calf Mortality in the First Month of Life in Sloveniaperiod was 1.6- and 1.4-times higher in calves from Holstein Friesian dams compared to Simmental and Brown breed dams, and 0.9-times lower in Brown dams compared to Simmental dams. Diff erences among breeds in the neonatal period from the day 2 to 30 were smaller, and the diff erence between Simmental and Brown dams was not signifi cant (p>0.05). Th e likelihood of calf death was only 1.1-times higher in calves from Holstein Friesian dams compared to Simmental and Brown dams (Table 3). Perinatal mortality rates in Switzerland (Bleul, 2011) of 4.0% in Red Holstein and 2.8% in Holstein calves were much higher than in Braunvieh (2.3%) and Simmental calves (2.0%). Similarly, the mortality rates from the day 2 to 28 were higher in Red Holstein and Holstein (1.9 and 2.1%) than in Braunvieh and Simmental calves (1.8 and 1.0%). Gates (2014) reported for the UK much lower mortality rate within 180 days of age in calves from dams of beef breeds (2.5%) than dairy breeds (7.4%). Within dairy breeds, mortality rates from calves from Holstein Friesian and Holstein dams (7.7 and 8.4%) were slightly lower than from Brown Swiss dams (8.5%). Figure 1.The distribution of calves according to dam breed and herd size classMortality rate  Effect of  Birth year Calving season Num. of calves  at calving  Age of the dam at calving  Breed of  the dam Log10 herd size (breed of the dam) D.F. 7 3 2 5 3 4 PM χ2 381.3 110.2 19863.0 8081.7 394.2 1163 P-value <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 M 2-30 χ2 199.8 1018.0 464.2 361.8 13.0 4642.1 P-value <0.0001 <0.0001 <0.0001 <0.0001 0.0046 <0.0001 PM – perinatal mortality rate (aborted, stillborn and death within 24 hours after birth); M 2-30 – neonatal mortality rate from the day 2 to 30.  Dam breed  Holstein Friesian Simmental Brown Other Total PM 8.08 4.69 5.04 5.56 5.57 M 2-30 4.28 2.15 2.36 2.57 2.68 Overall 12.36 6.84 7.40 8.13 8.25 PM – perinatal mortality rate (aborted, stillborn and death within 24 hours after birth); M 2-30 – neonatal mortality rate from the day 2 to 30. Dam breed Dam breed Odds ratio 95% CI P-value PM Holstein Friesian Simmental 1.579 1.540-1.619 <0.0001 Holstein Friesian Brown 1.397 1.354-1.442 <0.0001 Holstein Friesian Other 1.428 1.387-1.470 <0.0001 Simmental Brown 0.885 0.863-0.908 <0.0001 Simmental Other 0.904 0.884-0.924 <0.0001 Brown Other 0.826 0.677-1.008 0.0603 M 2-30 Holstein Friesian Simmental 1.125 1.084-1.168 <0.0001 Holstein Friesian Brown 1.089 1.040-1.141 0.0003 Holstein Friesian Other 1.084 1.038-1.131 0.0002 Simmental Brown 0.968 0.933-1.004 0.0801 Simmental Other 0.963 0.933-0.994 0.0217 Brown Other 0.995 0.935-1.038 0.8172 PM – perinatal mortality rate (aborted, stillborn and death within 24 hours after birth); M 2-30 – neonatal mortality rate from day 2 to 30. Table 1. Calf mortality rates (%) in dam breeds in two periodsTable 3. Estimated odds ratios for mortality rate in perinatal period and in postnatal period until 30 days of age among calves of diff erent dam breeds at average herd sizeTable 2. Analysis of variance for calf mortality rate in the perinatal period and in neonatal period from the day 2 to 30 of ageAgric. conspec. sci. Vol. 82 (2017) No. 272 Mojca VOLJČ, Marko ČEPON, Špela MALOVRH, Silvester ŽGURIn Table 4, the eff ect of herd size within breed is presented. For every log10 increase in herd size in Holstein Friesian dams, the risk of calf dying in perinatal period increased by a factor of 1.146. In Simmental and Brown dams, these increased risk factors were higher 1.445 and 1.408. Th e comparison of risk factors revealed signifi cant (p<0.05) diff erences between calves from Holstein Friesian dams and from dams of all other breeds (Table 5), whereas no signifi cant diff erences were found among calves from Simmental, Brown and other breeds of dams. In the neonatal period from day 2 to 30, the risk of calf death by increasing herd size even increased. For every log10 increase in herd size, the risk factor increased by a factor of 2.295 in dams of other breeds to 2.616 in Brown dams. In this period no sig-nifi cant diff erences (p>0.05) were found among calves from Holstein Friesian, Simmental and Brown breed dams, whereas calves from all above-mentioned breeds signifi cantly diff ered from dams of other breeds (p>0.05). Some other authors like Bleul (2011), Guliksen et al. (2009), Kayano et al. (2016) and Silva del Rio (2007) observed increased perinatal mortality rate in larger herds, too. All mentioned authors speculated that higher mortal-ity rate in larger herds was associated with less intensive calving management. All above-mentioned studies included herd size as a class eff ect. Gates (2014), who treated herd size as a covari-ate in the model, reported higher risk of calf dying in the period within 280 days aft er birth for dairy than beef calves. For every log10 increase in herd size, the risk of a beef calf losses increased by a factor of 1.25 and of a dairy calf by factor of 2.10. Th us, his results are just the opposite of ours, which indicates less evident eff ect of herd size in Holstein Friesian. However, other authors (Mee et al., 2008, Fourichon et al. 2010) did not observe any re-lation between herd size and perinatal mortality rate.ConclusionsSince calf mortality rate is among the most important factors of sustainable and profi table milk and beef production, more at-tention should be given to risk factors that affect it. Higher peri-natal and neonatal mortality rates were found in calves of Holstein Friesian dams. Therefore, more consideration should be paid to calves of this breed.ReferencesBleul U. (2011). Risk factors and rates of perinatal and postnatal mortality in cattle in Switzerland. Livest Sci, 135: 257–264Compton C. W. R., Heuer C., Th omsen P. T., Carpenter T. E., Phyn C. V. C., McDougall S. (2017). Invited review: A systematic liter-ature review and meta-analysis of mortality and culling in dairy cattle. J Dairy Sci 100:1–16DEFRA. (2003). Improving calf survival. http://www.adlib.ac.uk/resources/000/020/709/calfsurvival.pdf (28. 2. 2017)Fourichon C., Beaudeau F., Bareille N., Seegers H. (2001). Incidence of health disorders in dairy farming systems in western France. Livest Prod Sci 68: 157–170.Fuerst-Waltl B., Fuerst C. (2010). Mortality in Austrian dual pur-pose Fleckvieh calves and heifers. Livest Sci 132: 80–86Gates M. C. (2013). Evaluating the reproductive performance of British beef and dairy herds using national cattle movement records. Vet Rec, 173: 499Gulliksen S. M., Lie K. I., Løken T., Østerås O. (2009). Calf mortal-ity in Norwegian dairy herds J. Dairy Sci. 92: 2782–2795Heinrichs A. J., Radostitis O. M. (2001). Health and production management of dairy calves and replacement heifers. p. 335. In: Herd Health - Food Animal Production Medicine. Radostitis O. M., ed. W. B. Saunders Company, Philadelphia, PAKayano M., Kadohira M., Stevenson M. A. (2016). Risk factors for stillbirths and mortality during the fi rst 24 h of life on dairy farms in Hokkaido, Japan 2005–2009. Prev Vet Med 127: 50–55Lombard J. E., Garry F. B., Tomlinson S. M., Garber L. P. (2007). Impacts of dystocia on health and survival of dairy calves. J Dairy Sci 90: 1751–1760Martin S. W., Wiggins A. D. (1973). A model of the economic costs of dairy calf mortality. Am J Vet Res 34:1027–1031Mee J. F., Berry D. P., Cromie A. R. (2008). Prevalence of, and risk factors associated with, perinatal calf mortality in pasture-based Holstein-Friesian cows. Animal, 2:4, 613–620.  Odds ratio 95% CI P-value PM Holstein Friesian 1.146 1.106-1.187 <0.0001 Simmental 1.445 1.404-1.488 <0.0001 Brown 1.408 1.330-1.490 <0.0001 Other 1.497 1.434-1.562 <0.0001 M 2-30 Holstein Friesian 2.553 2.422-2.650 <0.0001 Simmental 2.555 2.447-2.669 <0.0001 Brown 2.616 2.403-2.847 <0.0001 Other 2.295 2.156-2.444 <0.0001 PM – perinatal mortality rate (aborted, stillborn and death within 24 hours after birth); M 2-30 – neonatal mortality rate from the day 2 to 30.  Dam breed Dam breed Odds ratio 95% CI P-value PM Holstein Friesian Simmental 0.793 0.757-0.830 <0.0001 Holstein Friesian Brown 0.814 0.761-0.870 <0.0001 Holstein Friesian Other 0.765 0.724-0.809 <0.0001 Simmental Brown 1.026 0.963-1.094 0.4241 Simmental Other 0.965 0.917-1.016 0.1808 Brown Other 0.941 0.8761-1010 0.0910 M 2-30 Holstein Friesian Simmental 0.991 0.931-1.055 0.7871 Holstein Friesian Brown 0.969 0.880-1.066 0.5141 Holstein Friesian Other 1.104 1.022-1.192 0.0122 Simmental Brown 0.977 0.888-1.074 0.6304 Simmental Other 1.113 1.032-1.201 0.0057 Brown Other 1.140 1.026-1.266 0.0151 PM – perinatal mortality rate (aborted, stillborn and death within 24 hours after birth); M 2-30 – neonatal mortality rate from the day 2 to 30. Table 4. Th e eff ect of herd size on mortality rate in perinatal and postnatal period until 30 days of age in diff erent dam breedsTable 5. 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The Effect of Dam Breed on Calf Mortality in the First Month of Life in Slovenia

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