Relation of the length of productive life and the body conformation traits in Slovak Simmental breed

Data obtained from the evaluation of longevity in 118 646 dairy cows of the Slovak Simmental breed were analyzed. The average length of productive life reached 1 451 days (3.88 years). Based on the analysis of the length of productive life for the whole cattle population, we calculated the ratio of cows that reached more than 12, 24, 36, 48, 60, 72 and 84 months respectively. The most important effects were the sire (F=53.43, P<0.001) and the farm effect (F=26.32, P<0.001). The milk production at first lactation was an important factor, too. The effects of conformation traits on the length of productive life were analyzed in a group of 6 585 culled cows. From the main conformation traits the most important effects were recorded for body frame, udder, feet and legs. For a detailed evaluation, the level of the effects of a particular body conformation trait were tested. The most important effects were rump angle, croup height and body depth. The analysis of udder traits showed that the most important effects were udder depth, teats length, rear udder attachment and rear udder. From the feet and legs traits the most important effects were recorded for fetlock, foot and rear legs.


Introduction
Longevity, reproduction and total milk production in cows become the important traits among selection criteria criterions, which have tight connections to economic effectiveness of milk and beef production (MESZAROS et al. 2008) for Pinzgau Cattle, (SZAJKO 1987, DISTL 2001, CUE and ONGE 2002, BERGFELD and KLUNKER 2002, SWALVE 2003).
The fundamental problem of the selection for longevity is its low heritability.DUCROCQ (1987) calculated the heritability coefficient of longevity h 2 =0.09 in Holstein cattle.KARRAS et al. (1985) calculated h 2 from 0.05 to 0.09 for Simmental cattle in Germany and SöLKNER et al. (2000) h 2 =0.1 in Austria.One possibility is the selection based on the highly positive genetic and phenotype correlations between milk yield at first lactation and longevity traits.Several authors state the genetic correlation between 0.2 and 0.6 and the phenotype correlation between 0.2 and 0.4 ( VAN RADEN and KLAASKATE 1993, SAWA and KREZEL-CZOPEK 2009, DAKAY et al. 2006, TEKERLI and KOCAK 2009).
Positive relations or genetic correlations between production traits, morphological traits, QTL, body conformation traits and longevity are stated by several authors (VUKAŠINOVIČ et al. 1995), HANSEN et al. 1999, FREYER and ERHARDT 2000, JUSZCZAK et al. 2001, BUENGER et al. 2001, VALENCIA et al. 2004).BOUŠKA et al. (2007) present that heifers with the lowest intensity of growth have a significantly longer productive life than other animals (P<0.01).
The positive genetic correlation between longevity and the evaluation of the udder and teats is presented by VUKAŠINOVIČ et al. (1995) in Brown Swiss cattle and by LARROQUE and DUCROCQ (2001) in Holstein breed.
The relations between functional traits, body conformation traits and direct herd life were analyzed by MIGLIOR et al. (2001).They determined an order of traits by impact on direct herd life: mammary system, feet and legs, somatic cell count, rump angle, milkability and calving ease.Animals with low somatic cell count, excellent legs and udder, high milking speed, easy calving and correct rump angle have a higher tendency to survive longer than the mean of the herd.Some traits like body size, chest width and body depth (r=−0.21,−0.22 and −0.25) had negative relations to direct herd life.
POWELL and VAN RADEN (2003) evaluated longevity and the relation of longevity to other traits in 11 countries.The correlations between length of productive life and somatic cell count and body conformation traits are on similar levels in all investigated countries.The correlations of milk production traits to the length of productive life were different, according to the system of evaluation of longevity by direct herd life or functional herd life in cows.The authors state that the longevity is an indicator of fitness and keeper satisfaction, but evaluated traits are defined and analysed in various ways in each country (SöLKNER et al. 2000).Correlations in longevity between selected production and functional traits ranged from −0.27 to 0.51, but the coefficients are a little bit higher in countries which use direct herd life instead of functional herd life.VACEK et al. (2006) found negative correlations between herd life or production life and teat length and udder depth as well as rump angle and rear leg set.Despite that most of the body traits had slightly positive correlations to the herd life, i.e. larger cows live longer.SöLKNER et al. (2000) andBAUMUNG et al. (2001) underline that longevity in cow is an integral part of selection in cattle breeds with dual purpose.Auxiliary traits which indirectly influence the length of productive life in dairy cows are body conformation traits, classified during body conformation classification, mainly feet, legs and mammary system.
The aim of this paper was the evaluation of the length of productive life in the Slovak Simmental cattle population.In addition, the paper focusses on the testing of effects that affect the length of productive life and the analysis of relations between conformation traits and the length of productive life.

Material and methods
The starting point for the analysis of the productive life duration were records of 118 646 culled cows from the database of the State Breeding Institute of the Slovak Republic and the Slovak Simmental Cattle Herd Books from the years 1997 to 2006.
The duration of the productive life was calculated in days for each dairy cow in the database of culled cows, the average of the length of productive life taken from the whole group and then we analyzed the number and ratio of the dairy cows which survived the defined levels 12, 24, 36, 48, 60, 72 and 84 months after first calving, respectively.
Using information from literature sources and stated hypotheses, we picked up effects, which can affect the length of productive life considerably: farm, milk production at 1st lactation, breeding group (S 0 , S 1 , S 2 ), sire, year of culling and age at first calving.Breeding group is defined in accordance with the Slovak Simmental Herdbook: S 0 -pure breed cows, S 1 -crossbreeds with 12.5 up to 22 % of other breeds, S 2 -crossbreeds with 25.1 up to 50 % of other breeds.
The impact of the evaluated effects on the length of productive life in cows was calculated by a simple linear model where Y ijklmno is the length of productive life, μ is the mean, M i is the effect of i-milk production at first lactation, F j is effect of j-farm, B k is the effect of k-breeding group, S l is the effect of l-Sire, C m is the effect of m-year of culling, R n is the effect of n-reason of culling, A o is the effect of o-age at first calving and e ijklmno is the residual error.Calculated significantly positive effects will be regarded in the genetic evaluation of the length of productive life.
Since the 1.10.1997, the »System 97« -an integrated European system for type classification in Simmental cattle -is used for type classification in Slovakia.
We have evaluated the relations between conformation traits and the length of productive life in a group of 6 298 cows, for which we obtained official records of type classification.The precise estimation of the interactions between the effects was done by a general linear model in the statistical software SAS 9.1.In the present study the impact of main and partial traits and groups of conformation traits on the length of productive life was tested.
For the main traits: where Y ijklm is the length of productive life, μ is the mean, B i is the i-body frame, M j is the j-muscularity, L k is the k-legs, U l is the l-udder, C m is the m-udder cleanness and e ijklmn is the residual error.Similar linear models were used for the estimation of the impact of udder, legs and body measurement traits.The rate of the effects was calculated as the sum of squares of a particular trait divided by the total sum of squares.

The evaluation of length of productive life in dairy cattle
In this paper was evaluated the level of the reached real length of the productive life in a population of the Slovak Simmental breed.The average length of the productive life in the analyzed group of 118 646 cows was 1 451 days (3.88 years), which represents an average level of 3.4-3.6lactations in dairy cows, under suitable reproduction conditions.EGGER-DANNER (2005) found out that the length of the productive life decreases in cows of a particular breeds in Austria.Simmental-Fleckvieh cattle reached 3.56 years of age in 2004, Holstein cattle reached 3.21 years of age and Pinzgau reached 3.53 years of age.The author suggests the stricter selection at farms as the reason for this tendency, because the genetic trends for the productive production lifetime are relatively fixed.
An analysis of the length of productive life in a whole population of culled cows of the Slovak Simmental breed shows that 87.16 % of the cows reach 12 months of age, 24 months of age are reached by 72.39 % of the cows, 36 months of age by 58.16 % and 48 months by 44.11 %. Results for the length of productive life are presented in Figure 1.The relatively high rate of cows reached the 72 and 84 months of age (30.77%).By this fact it can be stated that up to third dairy cows of Slovak Simmental breed survive A relatively high rate of cows reached 72 and 84 months of age (30.77 %).From this fact it can be stated that up to a third of the dairy cows of the Slovak Simmental breed survive up to 6-7 lactations in herds, which generates conditions for the achievement of the maximal milk production at the 4th and 5th lactations.Changes in survival of cattle are interesting from an historical point of view, too.AVERDUNK and GEOURGOUDIS (1985) present the persistence data of cows of particular breeds by year of birth from 1970 to 1978 in Bavaria in Germany.
The mean of 48 months survival in cows ranged from 60.6 % to 76.8 %, 60 months survival ranged from 43.0 %-61.5 %, 72 months survival ranged from 30.3 % to 50.5 % and 84 months survival ranged from 20.7 % to 40.9 %.PSOTA (1993) presents the persistence of cows in Slovakia at the age of 48 months from 53.4 % to 86.2 %, at the age of 60 months from 26.2 % to 55.9 % and at the age of 72 months from 13.9 % to 31.9 %.In Saxonia, functional longevity was reduced from 39 to 30 months from 1994 to 2001 (BERGFELD and KLUNKER 2002).
A relatively low rate of culled cows was recorded in cows at the first lactation, which indicates moderately applied selection of cows by milk production at first lactation, at first milk recording or at 100 and 200 days of first lactation.
In the present study a more intensive culling (14.77 %) was recorded during the second lactation, which is evidence for a noticeable selection by information about milk recordings at first lactation and first recordings at second lactations.This recording has a most important role in the next position of the cow in the herd.This is evidence for the breeders' experience in milk production in this dual purpose breed, in which a considerable increase of milk production is recorded just at the beginning of the second lactation, in contrast to pure milk breeds.CASANOVA and SCHMITZ (1987) evaluated the longevity of Simmental cattle in Switzerland in a total number of 34 583 daughters of 2 887 Sires, which first calved in 1979.The persistence of the whole evaluated group was 92.5 % at 36 months, 68.6 % at 48 months, 52.7 % at 60 months, 39.8 % at 72 months and 28.2 % at 84 months of age.The decrease of persistence between the 36 months and the 48 months level suggests a considerable level of culling due to low milk production.The length of the productive life increased with a higher milk yield at the first lactation.An increasing milk production at the first lactation had a positive effect on the longevity, but conversely, the high yielding dairy cows (with a production over 4 000 kg of milk per lactation) had an average longevity lower than dairy cows with a production under 4 000 kg milk per lactation.The positive relation between the breeding value of milk production traits and the length of productive life is also suggested by ABDALLAH et al. (2002).

The effects influencing the length of the productive life
The factors farm, milk at 1st lactation, breeding group, sire, year of culling and age at first calving were used for the analysis of the evaluated group of 118646 culled cows of Slovak Simmental breed.The analysis shows that all factors have considerable effects on the length of productive life.The degree of the effects varied (Table 1).The most important effects were the sire (46.59%,F=53.43,P<0.001) and the farm (14.02%,F=26.32,P<0.001) which confirms equity of the selection for longevity while otherwise exploiting the breeding values for the length of productive life in the selection indexes in the cattle (SöLKNER et al. 2000, BAUMUNG et al. 2001).Similar results are presented by OJANGO et al. (2002).
The milk production at first lactation also plays an important role (2.37 %, F=7736.88,P<0.001).This fact shows the trend to a more intensive increase of he milk efficiency in the Slovak Simmental breed.VALENCIA et al. (2004) found out, that the genetic correlation between traits of longevity and milk production at first lactation raged from 0.33 to 0.64, between milk production at first lactation and body conformation traits from −0.27 to 0.48 and between persistence at 48 months of age and body conformation traits from −0.30 to 0.69.Also SAWA and KREZEL-CZOPEK (2009) found positive genetic and phenotype correlations between total milk production traits, criteria of longevity and milk production at first lactation (r=0.64-0.92).MÉSZáROS et al. (2008) suggest an importance of milk production at first lactation, too.Cows with milk yields of 1.5 standard deviations below the herd mean were 5.3 times more likely to be culled than cows with an average production.
Less or not important effects on the length of productive life were calculated for year of culling (1.5 %, F=26.32,P<0.001), age at first calving (0.84 %, F=2759.81,P<0.001) and breeding group (0.22 %, F=18.09,P<0.001).Contrarily, POWELL and RADEN (2003) mention the high importance of the year of birth and the year of culling on the longevity and length of productive life in cows.High negative correlations for the age at first calving (from r=−0.28 to r=−0.45) are presented by RIZZI et al. (2002), too.The importance of the year of culling and the year of birth may be caused by a generally increasing intensification of milk production and milk efficiency, an increasing intensity of the turnover in the herds, the decreasing care for dairy cows, and the increasing strain to the organism of the cows that's also connected to the increasing milk yield too.
The considerable effects of the tested factors confirm the accuracy of they selection (Table 1).

Relations between the length of productive life and body conformation traits
One implication of the indirect selection for longevity in dairy cows is the application of the correlated traits, which show the potentioal of the individual from a young age and are related to its survival in the herd.From the main and partial traits mainly the body conformation traits, the legs and the udder conformation were regarded.
The analysis done by a linear model in the investigated group (6 298 cows) shows a considerable effect of the main trait body frame (F=17.39,P<0.001) on the length of productive life (Table 2).VUKAŠINOVIČ et al. (1995) present a genetic correlation between longevity and body length (r=0.39) and body depth (r=0.42).A positive relation between body size or body height and longevity is presented by CASSANDRO et al. (1999) andSTRAPAK et al. (2005).
The length of the productive life was considerable affected by udder (F=9.43,P<0.001) and legs (F=6.41,P<0.001), the same results are presented by BURKE andFUNK (1993), DEKKER et al. (1994) and in populations of Simmental cattle by SöLKNER and PETCHINA (1999) and HAMANN and DISTL (2002).
The detailed analysis of the partial traits from the body frame group shows the considerable effects of rump angle (F=13.29,P<0.001), body depth (F=6.63,P<0.001) and croup height (F=5.66,P<0.001).
The correlation analysis of partial traits of the legs to the length of productive life (Table 2) shows the most important effects fetlock conformation (F=9.1,P<0.001), feet (F=5.47,P<0.001) and rear legs set (F=1.88, P<0.001).The cows with sound conformation of the rear legs, the fetlock and the feet reach a longer productive life.The results of the present paper confirm conclusions of authors which found unalterable positive relations between leg conformation and longevity regardless of the breed (SöLKNER and PETSCHINA 1999, HAMANN and DISTL 2002, STRAPAK et al. 2005).BURKE and FUNK (1993) found a longer productive life in cows with a correct rear leg set in all husbandry systems.VUKAŠINOVIČ et al. (1995) found low or moderate genetic correlations of rear leg posture (r=0.35),foot angle (r=0.25) and fetlock (r=0.21) in Brown Swiss cattle.
The analysis of partial traits of the udder shows that the most important effects on the length of productive life result from udder depth (F=26.04,P<0.001), rear udder (F=2.09,P<0.01) and rear udder attachment (F=2.16,P<0.001).The udder suspensory ligament shows a relatively considerable effect on the production lifetime, too.VUKAŠINOVIČ et al. (1995) found significant genetic correlations between longevity and the evaluation of the udder and the teats (r ranged from 0.38 to 0.66).Similar findings are presented by BURKE and FUNK (1993), especially for simmentalized breeds in Europe.STRAPáK et al. (2005) andVACEK et al. (2006) suggest well attached fore udder, high attached rear udder, strong central ligament, close front teat placement and moderately long teats as important traits for a long productive life with P-values of <0.05-0.001.
From the evaluated traits of the teats in the present study the most important and significant effect on longevity was calculated for teat length (F=18.49,P<0.001).The positive effect of the teat conformation on the production lifetime is confirmed by VUKAŠINOVIČ et al. (1995) andROGERS et al. (1998).The present results shows that dairy cows with less shallow udder but well attached, wide and long rear udder and moderate teat length reach a higher longevity in herds.
The results of the linear model for the estimation of the effects of all partial traits together confirm the effects of the same traits as in the partial models of the body measurements, the udder and the legs.The most important were the effects of the udder depth, teat length and rump slope.

Figure 1 Figure 1
Figure 1Percentage of cows that reached particular levels of length of productive life in days (n=118 646).Anteil der Kühe, welche die einzelnen Nutzungsjahre erreichten(Zahlenangaben in Tagen)

Table 1
Analysis of the effects of the factors on the length of productive life (n=118 646) Faktorenanalyse für die Dauer produktiven Lebens der Kühe

Table 2
(SöLKNER and PETSCHINA 1999)ial traits of type classification on the length of productive life in cows (n=6298) Einfluss der untersuchten Merkmale auf die Dauer des produktiven Lebens der KüheHANSEN et al. (1999)found out that dairy cows of the Holstein breed with smaller body size reached a higher length of productive life at the levels of 72 months of age and 84 months of age in comparison with dairy cows with bigger body size.The difference between groups was 88 days (2.9 months) i.e. 15.4 %.At the level of 72 months the difference was statistically significant.Similar results are confirmed for Simmental cattle mainly in Germany and Austria, which have populations of the Slovak Simmental cattle with different body size(SöLKNER and PETSCHINA 1999).Apart from the above mentioned, the present study evaluated cows culled from 1997 to 2003 and during this period the body size in the Slovak Simmental cattle population increased 4.3 cm, which can considerable affect results of the presented paper.