J Philipsson

Genetic and Environmental Correlations Among Female Fertility Traits and Milk Production in Different Parities of Swedish Red and White Dairy Cattle

The main objective of this study was to estimate genetic correlations between fertility and production traits in first, second and third lactations as well as between fertility traits measured in the same way at different ages. The fertility traits studied were: number of inseminations per service period, number of treatments for reproductive disturbances, interval between first and last inseminations, interval between calving and first insemination, and interval between calving and last insemination. Early milk production was measured as the average of the energy-corrected milk yield at the second and third monthly testdays in a lactation. The number of records was approximately 450 000, 350 000, 180 000 and 75 000 in the heifer period, first, second, and third lactations, respectively. A linear, trivariate model that included the effects of herd-year, year, month, age and sire of the cow was applied. To reduce the effect of ongoing selection, 305-days kg protein production in first lactation was included as a variate in all of the analyses. Correlations between the herd-year effects indicated that factors of herd-year level conducive to increased production had a tendency to increase the number of inseminations as well as the number of reproductive treatments, although there was an earlier start and termination of the insemination period. Genetic correlations between fertility traits and production were in the range of 0.2-0.4, all of them unfavourable and higher at later parities. The genetic correlations between fertility traits in the heifer period and the same traits in first lactation were 0.7. Genetic correlations between the first and second lactation varied between 0.7 and 0.9, and between the second and third lactation they were all 0.9 or higher. In conclusion, fertility and production traits need to be selected for simultaneously if fertility is going to be maintained along further genetic improvement on production, and such selection should include fertility results from lactating cows.

Genetic aspects of female fertility in dairy cattle

Abstract The problem area of female fertility in dairy cattle has been discussed, especially as regards its genetic variation and correlation with production, in the light of recently published results. Furthermore, the implications for selection of the parameters found have been illuminated. It is concluded that the magnitude of the additive genetic variance in several fertility traits is considerable, despite the generally low heritability values of individual insemination results. The genetic effect of cow culling within herds for poor fertility is almost negligible, while progeny testing of bulls for daughter fertility offers valuable information for selection purposes. Several recent investigations appear to indicate antagonistic relationships between production and fertility. However, the findings are somewhat ambiguous. When unfavourable, even though not very strong, correlations do exist, detrimental effects on fertility will occur as a consequence of intense long-term selection for yield if the fertility of daughters is not considered simultaneously with production in selection programmes.

Somatic cell count as a selection criterion for mastitis resistance in dairy cattle.

Abstract The purpose of this study was to investigate whether it is possible to increase the resistance to clinical mastitis by selecting for bulls siring daughters whose milk has a low somatic cell count. Data from the animal disease recording scheme, including all veterinary treatments for clinical mastitis, were used in the analysis. A total of 1462 progeny tested Swedish Red and White bulls (SRB), and 911 Swedish Friesian bulls (SLB), with nearly 750 000 effective daughters, were included. Effects of alternative selection criteria on response to clinical mastitis were studied by using selection index theory. Correlations between relative breeding values for clinical mastitis and somatic cell count were 0.45 for SRB bulls and 0.41 for SLB bulls. Corresponding genetic correlations were indirectly estimated to be 0.79 and 0.71. The relationships were found to be linear. It was concluded that it is possible to improve resistance to clinical mastitis by selecting for a low somatic cell count. Due to the higher heritability of the somatic cell count selection based on this was more efficient than selection directly on clinical mastitis to improve mastitis resistance when only small progeny groups (less than 100 daughters) were available. However, a combination of both measures was about 20% more efficient than the former alone. There were no significant differences in relative breeding values for clinical mastitis between bulls differing in their proportion of Holstein-Friesian genes.

Estimates of longevity and causes of culling and death in Swedish warmblood and coldblood horses.

Data on several different horse populations were analysed and compared regarding length of life and diseases or injuries leading to death or culling. In order to include information for horses still alive, a failure time (survival) analysis was used. The first material included 1847 warmblood horses born between 1968 and 1982, that had participated in the Swedish Riding Horse Quality Test (RHQT) as 4-year-olds. The next two materials included 344 warmblood and 204 coldblood horses owned by the Swedish Cavalry Horse Foundation (CHF), born between 1970 and 1975. The last population consisted of 481 warmblood brood-mares born between 1965 and 1967. According to this study it was important to estimate the median length of life separately for each sex. For warmblood brood-mares and mares that had participated in the RHQT, comparable figures of 18.6 and 18.3 years were found. Close agreement was also found between geldings of the CHF and males that had participated in the RHQT; the estimates were 14.7 and 13.9 years, respectively. There was a positive trend in the median length of life over time for horses that had participated in the RHQT, and the median length-of-life curve increased more steeply for mares than for males. This study showed a longer median length of life for coldblood geldings, 17.6 years, than for the mares, 16.4 years. The most common causes of death of warmblood horses were diseases of the musculoskeletal system (56-57%), respiratory diseases (8-9%), diseases of the digestive system (5-6%) and accidents (3-9%). The primary causes of death of coldblood horses were temperamental disorders (23%), diseases of the musculoskeletal system (14%) and hoof diseases (8%).

Sire evaluation standards and breeding strategies for limiting dystocia and stillbirth. Report of an E.E.C./E.A.A.P. working group

In most European countries, calving problems exert a significant influence on the economics of cattle breeding. In order to reduce the incidence of dystocia and stillbirth, a variety of breeding schemes are in use. Sampling techniques and definitions differ between countries and organizations as do methods of calculation, publishing and utilization of results. An E.E.C. working group was therefore set up with the task of establishing standards which should lead to a greater uniformity in this field of breeding work. The most important recommendations of the group can be summarized as follows. To characterize calving problems the two traits, dystocia and stillbirth, should both be used. Definitions for the criteria are given. In order to minimize the expense of testing programs, already existing information from milk recording or A.I. should be utilized. Additional information necessary for progeny testing is described. For sire evaluation it is recommended that heifer results be used when possible, as the heritability of cow results is extremely low and also because the genetic correlations with heifer results are so moderate. As sires of the calves (direct effect) as well as sires of dams (whole maternal and half of the direct effect), bulls exert an appreciable effect on the incidence of dystocia and stillbirth. Consequently, breeding values should be estimated for both types of effect. The accuracy of progeny tests is discussed in relation to heritability level and number of calvings required. The genetic merit of a bull should be stated as breeding values, either absolute, relative or in five classes, according to an earlier E.A.A.P. recommendation. If more than one character is recorded it may be worthwhile constructing a selection index. The types of effect which should be combined into a total index for a bull, depend on the breeding goal and the breeding strategy applied. Finally the advantages and disadvantages of three possible breeding strategies are discussed and the possible expected gains are illustrated.

Genetic correlations between field test results of Swedish Warmblood Riding Horses as 4-year-olds and lifetime performance results in dressage and show jumping

Abstract The main objective of this study was to estimate genetic correlations between traits of young sport horses (4 years old) evaluated in the Swedish Riding Horse Quality Test (RHQT) and later competition results in dressage and show jumping. The data comprised 3708 Warmblood horses born between 1968 and 1982 that had participated in the RHQT as 4-year-olds and 25 605 horses born between 1953 and 1995 with competition records. According to the criteria between 1206 and 1879 horses were common to this two files and were available for the estimations of the genetic correlations. Competition performance traits were cumulative points and cumulative placings received during a horse’s lifetime, and a log 10 transformation was used to achieve a more normal distribution of the data. Genetic correlations between gait traits scored in the RHQT and competition results in dressage were favourable, in the range 0.63–0.75, and between jumping traits scored in the RHQT and results in show jumping 0.83–0.93. Estimated heritabilities for gait and jumping traits scored in the RHQT were in the range 0.09–0.27 and 0.10–0.18, respectively. Estimated heritabilities for the cumulative points and cumulative placings in dressage and show jumping were 0.17/0.16 and 0.23/0.27, respectively. Thus, the results from the RHQT have proved to be useful for early genetic evaluation and selection of both mares and stallions for sport performance traits.

Relationships between conformation, performance and health in 4-year-old swedish warmblood riding horses

Abstract The correlation between conformation and performance traits of 195 tested 4-year-old riding horses was estimated using a quantitative method for measuring certain conformational details as well as by traditional judging of conformation. Performance was assessed by scoring gaits and jumping under saddle. Furthermore, medical and orthopaedic status was recorded. It is concluded that the inclusion of certain quantitative conformational measurements would improve the traditional judging system as a means to predict performance, and especially gaits under saddle. Conformation, including evaluation of walk and trot at hand, accounted for 43% of the variation in gaits under saddle. Correlations between conformation and jumping ability and health were much weaker (R 2 =7–10%). The femur proved to be the most important of the quantitative conformation measurements, as a long and forward sloping femur places the hindleg further forward under the horse, which facilitates the function of the hindleg and improves balance.

Estimation of Genetic (Co)variance Components for International Evaluation of Dairy Bulls

Abstract Within- and across-country genetic parameters need to be estimated prior to an international genetic evaluation of dairy bulls. A procedure based on the Expectation Maximization algorithm to produce restricted maximum likelihood estimates of such parameters, using national evaluation results from different countries, was tested by simulation. Individual performance records were generated for two populations of dairy cattle with separate breeding programmes but considerable genetic exchange to create ties between the populations. A genotype-by-country interaction effect was generated by simulating the data according to a genetic correlation of 90 between performance in the two countries. Within-country national evaluations were computed with animal models. The estimation procedure was tested using bull national evaluation results. The impact of factors such as data connectedness, time period, and bias in national evaluations on estimated parameters was investigated. When all data were included in ...

Genetic parameters for traits at performance test of stallions and correlations with traits at progeny tests in Swedish warmblood horses.

Abstract Genetic parameters for traits evaluated in the Swedish stallion performance test (SPT) and correlations between stallion performance test traits and 4-year-old offspring results from field tests were estimated. Heritability coefficients were on average 0.40 for individual gaits under rider and 0.23–0.47 for jumping traits at SPTs. Repeatabilities between tests at 6-month intervals were 0.75–0.77 for gaits and 0.38–0.58 for jumping traits. The genetic correlation between the gaits ranged from 0.30 to 0.71. Positive genetic correlations were found between gaits under rider and jumping traits (0.14–0.54), thus breeding for both characteristics is facilitated. Free jumping results were highly correlated (0.93) to results in jumping under rider, and because of their higher heritability the former are very suitable for selection purposes. Genetic correlation estimates between a trait in SPT and the same trait at 4-year-old offspring field test were unity for gaits under rider and jumping. The genetic correlations between gaits and jumping at the two different tests were 0.26–0.35. It was concluded that the field tests are well suited for early progeny testing of the stallions, and will improve the accuracy in selection of stallions for performance traits.

Genetic variation in competition traits at different ages and time periods and correlations with traits at field tests of 4-year-old Swedish Warmblood horses.

For many years, the breeding value estimation for Swedish riding horses has been based on results from Riding Horse Quality Tests (RHQTs) of 4-year-olds only. Traits tested are conformation, gaits and jumping ability. An integrated index including competition results is under development to both get as reliable proofs as possible and increases the credibility of the indexes among breeders, trainers and riders. The objectives of this study were to investigate the suitability of competition data for use in genetic evaluations of horses and to examine how well young horse performance agrees with performance later in life. Competition results in dressage and show jumping for almost 40 000 horses from the beginning of the 1960s until 2006 were available. For RHQT data of 14 000 horses judged between 1988 and 2007 were used. Genetic parameters were estimated for accumulated competition results defined for different age groups (4 to 6 years of age, 4 to 9 years of age and lifetime), and for different birth year groups. Genetic correlations were estimated between results at RHQT and competitions with a multi-trait animal model. Heritabilities were higher for show jumping than dressage and increased with increasing age of the horse and amount of information. For dressage, heritabilities increased from 0.11 for the youngest group to 0.16 for lifetime results. For show jumping corresponding values increased from 0.24 to 0.28. Genetic correlations between competition results for the different age groups were highly positive (0.84 to 1.00), as were those between jumping traits at RHQT and competition results in show jumping (0.87 to 0.89). For dressage-related traits as 4-year-old and dressage competition results the estimated genetic correlations were between 0.47 and 0.77. We suggest that lifetime results from competitions should be integrated into the genetic evaluation system. However, genetic parameters showed that traits had changed during the over 35-year period covered due to the development of the sport, which needs to be considered in future genetic evaluations.