Milk production, fertility, longevity and health records, were extracted from databases of two milk recording organisations in the United Kingdom for the first three lactations of the Holstein-Friesian breed. These included data related to health events (mastitis and lameness), voluntarily recorded on a proportion of farms. The data were analysed to calculate disease incidence levels and to estimate genetic parameters for health traits and their relationships with production and other functional traits. The resulting dataset consisted of 124 793 lactations from 75 137 animals of 1586 sires, recorded in 2434 herds. Incidence of health events increased with parity. The overall incidence of mastitis (MAS) and lameness (LAM), defined as binary traits, were 17% and 16%, respectively. Heritability estimates for MAS and LAM were 0.04 and 0.02, respectively, obtained from repeatability linear sire models. Heritability estimates of mastitis and lameness as count traits were slightly higher, 0.05 and 0.03, respectively. Genetic correlations were obtained by bivariate analyses of all pair-wise combinations between milk 305-day yield (MY), protein 305-day yield (PY), fat 305-day yield (FY), lactation average log e transformed lactation average somatic cell count (SCS), calving interval (CI), days to first service (DFS), non-return at 56 days (NR56), number of inseminations (NINS), mastitis (MAS), number of mastitis episodes (NMAS), lameness (LAM), number of lameness episodes (NLAM) and lifespan score (LS). As expected, MAS was correlated most strongly with SCS (0.69), which supports the use of SCS as an indicator trait for mastitis. Genetic correlations between MAS and yield and fertility traits were of similar magnitude ranging from 0.27 to 0.33. Genetic correlations between MAS with LAM and LS were 0.38 and 20.59, respectively. Not all genetic correlations between LAM and other traits were significant because of fewer numbers of lameness records. LAM had significant genetic correlations with MY (0.38), PY (0.28), CI (0.35), NINS (0.38) and LS (20.53). The heritability estimates of mastitis and lameness were low; therefore, genetic gain through direct selection alone would be slow, yet still positive and cumulative. Direct selection against mastitis and lameness as additional traits should reduce incidence of both diseases, and simultaneously improve fertility and longevity. However, both health traits had antagonistic relationships with production traits, thus genetic gain in production would be slower.

Premature mortality and culling causes great wastage in the dairy industry, as a large number of heifers born never become productive or are culled before their full lactation potential is reached. The objectives of this study were to characterize survival and estimate genetic parameters for alternative longevity traits that considered (1) the survival of replacement heifers and (2) functional longevity of milking cows in the UK Holstein Friesian population, using combined information from the British Cattle Movement Service and milk recording organizations. Mortality of heifers was highest in the first month of life and was proportionately highest in calves born during winter months. Heifer mortality tended to decrease with age until about 16 mo onward; it then gradually increased, expected to be associated with culls due to reproductive failure or problems during pregnancy and calving. In milking cows, days of productive life (DPL) was analyzed as an alternative to the current trait lifespan score. Cows that died in 2009 on average lived for 6.8 yr with an average production of 4.3 yr. Heritability estimates were low for both heifer and cow survival and were ~0.01 and ~0.06, respectively. The positive genetic correlation between heifer survival with lifespan score (0.31) indicates that bulls that sire daughters with longer productive lives are also likely to have calves that survive and become replacement heifers. However, the magnitude of the genetic correlation suggests that survival in the rearing period and the milking herd are different traits. Genetic correlations were favorable between DPL with somatic cell count and fertility traits indicating that animals with a longer productive life tend to have lower somatic cell count, a shorter calving interval, fewer days to first service, and require fewer inseminations. However, an antagonistic relationship existed between DPL with milk and fat yield traits.

The effect of subclinical paratuberculosis (or Johne's disease) risk status on performance, health, and fertility was studied in 58,096 UK Holstein-Friesian cows with 156,837 lactations across lactations 1 to 3. Low-, medium-, and high-risk group categories were allocated to cows determined by a minimum of 4 ELISA milk tests taken at any time during their lactating life. Lactation curves of daily milk, protein, and fat yields and protein and fat percentage, together with log-transformed somatic cell count, were estimated using a random regression model to quantify differences between risk groups. The effect of subclinical paratuberculosis risk groups on fertility, lactation-average somatic cell count, and mastitis were analyzed using linear regression fitting risk group as a fixed effect. Milk yield losses associated with high-risk cows compared with low-risk cows in lactations 1, 2, and 3 for mean daily yield were 0.34, 1.05, and 1.61kg; likewise, accumulated 305-d yields were 103, 316, and 485kg, respectively. The total loss was 904kg over the first 3 lactations. Protein and fat yield losses associated with high-risk cows were significant, but primarily a feature of decreasing milk yield. Similar trends were observed for both test-day and lactation-average somatic cell count measures with higher somatic cell counts from medium- and high-risk cows compared with low-risk cows, and differences were in almost all cases significant. Likewise, mastitis incidence was significantly higher in high-risk cows compared with low-risk cows in lactations 2 and 3. Whereas the few significant differences between risk groups among fertility traits were inconsistent with no clear trend. These results are expected to be conservative, as some animals that were considered negative may become positive after the timeframe of this study, particularly if the animal was tested when relatively young. However, the magnitude of milk yield losses together with higher somatic cell counts and an increase in mastitis incidence should motivate farmers to implement the appropriate control measures to reduce the spread of the disease.

Genetic parameters were estimated in a joint analysis of log(e)-transformed somatic cell count (TSCC) with either mastitis as a binary trait (MAS) or the number of mastitis cases (NMAS) in Holstein-Friesian cows for the first 3 lactations using a random regression model. In addition, a multi-trait analysis of MAS and NMAS was also implemented. There were 67,175, 30,617, and 16,366 cows with records for TSCC, MAS, and NMAS in lactations 1, 2, and 3, respectively. The frequency of MAS was 14, 20, and 25% in lactations 1, 2, and 3 respectively. The model for TSCC included herd-test-day, age at calving and month of calving, fixed lactation curves nested with calving year groups, and random regressions with Legendre polynomials of order 2 for animal and permanent environmental effects. The model for MAS and NMAS included fixed herd-year-season, age at calving and month of calving, and random animal and permanent environmental effects. All analyses were carried out using Gibbs sampling. Estimates of mean daily heritability averaged over a 305-d lactation were 0.11, 0.14, and 0.15 for TSCC for lactations 1, 2, and 3, respectively. Corresponding heritability estimates for MAS were 0.05, 0.07, and 0.09. The heritabilities for NMAS were similar at 0.06, 0.07, and 0.12, respectively, for lactations 1, 2, and 3. The genetic correlations between lactations 1 and 2, 1 and 3, and 2 and 3 were 0.75, 0.64, and 0.92 for computed 305-d lactation TSCC; 0.55, 0.48, and 0.89 for MAS; and 0.62, 0.42, and 0.85 for NMAS, respectively. The genetic correlations between MAS and TSCC were positive and generally moderate to high. The genetic correlations between computed 305-d lactation TSCC and MAS were 0.53, 0.61, and 0.68 in lactations 1, 2, and 3, respectively. Similar corresponding genetic correlations were obtained between computed 305-d lactation TSCC and NMAS in the respective parities. Mastitis as a binary trait and NMAS in the same lactation were very highly correlated and were genetically the same trait. It is intended that the new parameters will be used in setting up a national evaluation system for the joint analysis of TSCC and MAS.

The UK national scrapie plan (NSP) for sheep is based on selection for the resistant ARR/ARR genotype and elimination of susceptible types of the ovine prion protein (PrP) gene. The aim of this study was to estimate the possible association of the PrP genotype and performance traits by using data from the CAMDA Welsh Mountain flock. Four alleles (ARH, ARQ, ARR and VRQ) and 10 genotypes covering all five NSP risk groups were present in the CAMDA flock. Overall, the most common allele was ARR (35.2%), and VRQ was the least common (5.4%). The commonest genotypes were ARR/ARQ (23.7%) and ARR/AHQ (23.1%). The most resistant genotype, ARR/ARR, and the most susceptible genotype, VRQ/VRQ, were found in 10.2% and 0.3%, respectively, of the population tested. The associations of PrP genotypes with weight and ultrasonically scanned traits were investigated in three analyses, the first using genotypes, the second using risk categories and the third using number of alleles. These associations were evaluated by univariate analysis of each trait using an animal model with maternal effects where appropriate, and PrP was included as a fixed effect. Selection for scrapie resistance will not adversely affect progress in the traits considered and is consistent with improvements in muscle depth.