The effects of early initiation of first service for dairy heifers on their fertility and productivity up to the third lactation were examined under constant raising and management conditions. Eight Holstein heifers in their early breeding regimens and eight Holstein heifers in their late breeding regimens were initiated to be bred at 12 and 15 months of age, respectively, and were first calved at 21.5 and 25.1 months of age, respectively, with bodyweights of 563 and 638 kg after calving, respectively. Early first breeding resulted in a lower bodyweight and a lower body condition score, but it did not affect the fertility or milk production during the first lactation of heifers as cows. The calving intervals of cows to the second and third calving were similar in early and late bred heifers. Although the early bred heifers had a significantly lower fat-corrected milk yield at the second lactation than that of the late bred heifers, early breeding did not impair the productivity indicated by the mean milk yield per day from birth to the end of the third lactation with a shorter production period.

We estimated the genetic parameters of fat-to-protein ratio (FPR) and the genetic correlations between FPR and milk yield or somatic cell score in the first three lactations in dairy cows. Data included 3,079,517 test-day records of 201,138 Holstein cows in Japan from 2006 to 2011. Genetic parameters were estimated with a multiple-trait random regression model in which the records within and between parities were treated as separate traits. The phenotypic values of FPR increased soon after parturition and peaked at 10 to 20 days in milk, then decreased slowly in mid- and late lactation. Heritability estimates for FPR yielded moderate values. Genetic correlations of FPR among parities were low in early lactation. Genetic correlations between FPR and milk yield were positive and low in early lactation, but only in the first lactation. Genetic correlations between FPR and somatic cell score were positive in early lactation and decreased to become negative in mid- to late lactation. By using these results for genetic evaluation it should be possible to improve energy balance in dairy cows.

Genetic variation of the behaviour of racehorses is one of the major concerns for racehorse breeders. In this study, the heritabilities of behavioural responses to the inspections of conjunctiva, auscultation and blood sampling and the genetic correlations among them were estimated in the Thoroughbred racehorse. The estimation was done with Bayesian analysis with Gibbs sampling based on the univariate or bivariate threshold animal models. The behavioural responses were scored with four categories at the first entrance quarantine in Miho Training Center of Japan Racing Association from 1993 to 1995. The behavioural responses were treated as categorical or binary traits, with both showing similar results. The estimated heritabilities were in the range of 0.23-0.28, suggesting a genetic component in the variation on these traits. The estimated genetic correlations among the traits were very high (approximately 0.9), suggesting that these behavioural responses may be measures of the same trait. Because of the high genetic correlations, repeatability threshold model was applied assuming the responses to be a genetically identical trait measured with three different tests. The estimated heritabilities (approximately 0.23) were at the lower bound of the former estimates. The revealed high repeatabilities (0.97-0.98) suggest a strong contribution of the individual temperament on the behaviour of racehorses.

Longevity is a crucial economic trait in the dairy farming industry. In this study, our objective was to develop a random regression model for genetic evaluation of survival. For the analysis, we used test-day records obtained for the first 5 lactations of 380,252 cows from 1,296 herds in Japan between 2001 and 2010; this data set was randomly divided into 7 subsets. The cumulative pseudo-survival rate (PSR) was determined according to whether a cow was alive (1) or absent (0) in her herd on the test day within each lactation group. Each lactation number was treated as an independent trait in a random regression multiple-trait model (MTM) or as a repeated measure in a random regression single-trait repeatability model (STRM). A proportional hazard model (PHM) was also developed as a piecewise-hazards model. The average (± standard deviation) heritability estimates of the PSR at 365 d in milk (DIM) among the 7 data sets in the first (LG1), second (LG2), and third to fifth lactations (LG3) of the MTM were 0.042±0.007, 0.070±0.012, and 0.084±0.007, respectively. The heritability estimate of the STRM was 0.038±0.004. The genetic correlations of PSR between distinct DIM within or between lactation groups were high when the interval between DIM was short. These results indicated that whereas the genetic factors contributing to the PSR between closely associated DIM would be similar even for different lactation numbers, the genetic factors contributing to PSR would differ between distinct lactation periods. The average (± standard deviation) effective heritability estimate based on the relative risk of the PHM among the 7 data sets was 0.068±0.009. The estimated breeding values (EBV) in LG1, LG2, LG3, the STRM, and the PHM were unbiased estimates of the genetic trend. The absolute values of the Spearman's rank correlation coefficients between the EBV of the relative risk of the PHM and the EBV of PSR at 365 DIM for LG1, LG2, LG3, and the STRM were 0.75, 0.87, 0.91, and 0.93, respectively. These results indicated that the EBV of PSR could predict the genetic contribution to survival. The EBV based on the PSR of the STRM was highly correlated with that of the MTM (0.83-0.96). Furthermore, the calculation load of the STRM was lighter than that of the MTM because the rank of the matrix of the STRM was smaller than that of the MTM. These results indicated that the STRM is an appropriate model for estimating survivability by using random regression models.

Increasing herd-life length and culling parity with increasing conception rate (CR) is necessary to increase lifetime profit from dairy cow production. Economic values of days open (DO) were determined by calculating changes in fertility traits, herd-life length, and milk yield when the simulated CR were changed in increments of 1% from −5% to 5% from the basal levels, which were obtained for Hokkaido and regions other than Hokkaido separately. When CR increased, number of artificial inseminations, DO, and milking length decreased. Furthermore, culling parity, and annual milk yield increased. Herd-life length increased in Hokkaido and decreased in the other regions. The economic values of CR were 1,623.8 to 946.8 yen and of DO were 857.4 to 399.0 yen. Relative economic values of milk yield to days open per genetic standard deviation were higher in the other regions than in Hokkaido where the economic effect of selection for DO was expected to be equal to selection for 305-day milk yield and herd life. If the survival rate of multipara cows in the other regions increases, then the economic value of DO would similarly increase in Hokkaido.