Genetic parameters were estimated for egg defects, egg production, and egg quality traits. Eggs from 11,738 purebred brown-egg laying hens were classified as salable or as having one of the following defects: bloody, broken, calcium deposit, dirty, double yolk, misshapen, pee-wee, shell-less, and soft shelled. Egg quality included albumen height, egg weight, yolk weight, and puncture score. Body weight, age at sexual maturity, and egg production were also recorded. Heritability estimates of liability to defects using a threshold animal model were less than 0.1 for bloody and dirty; between 0.1 and 0.2 for pee-wee, broken, misshapen, soft shelled, and shell-less; and above 0.2 for calcium deposit and double yolk. Quality and production traits were more heritable, with estimates ranging from 0.29 (puncture score) to 0.74 (egg weight). High-producing hens had a lower frequency of egg defects. High egg weight and BW were associated with an increased frequency of double yolks, and to a lesser extent, with more shell quality defects. Estimates of genetic correlations among defect traits that were related to shell quality were positive and moderate to strong (0.24-0.73), suggesting that these could be grouped into one category or selection could be based on the trait with the highest heritability or that is easiest to measure. Selection against defective eggs would be more efficient by including egg defect traits in the selection criterion, along with egg production rate of salable eggs and egg quality traits.

The first objective of this study on broiler breeders was to investigate the genetic basis of variability in hatchability over age using a longitudinal model. Weekly percentage hatch of fertile and hatch of set eggs were available for 23,250 dams mated to 3,106 sires of the same age between the 28th and 54th week of life. Hatch of set was very highly correlated with fertility and showed a similar pattern through lay. There was a genetic contribution of the dam but not the sire to hatch of fertile; its heritability was about 6% from peak lay onward but lower earlier. The second objective was to investigate the relationship between hatchability and internal and external egg quality traits measured at 48 wk of age. These traits, specific gravity, weight loss, egg weight, and Haugh units, had moderate to high heritabilities, 0.53, 0.38, 0.65, and 0.38, respectively. Parameters of the genetic trend in weekly hatchability (mean and persistency) were significantly correlated with these egg quality traits, suggesting that in a bulk mating situation in which individual recording of hatchability is not possible, these quality traits could provide some indication on the trend in flock hatchability.

Dairy cattle production in Ireland is dominated by the Holstein Friesian (HF) breed which is the sire breed of over 90% of dairy cows in Ireland. Current trends however indicate an increase in the number of crossbred and non HF breeds cows that are milk recorded. Yet genetic evaluation to date has been available only for HF bulls and cows. Interest in the genetic evaluation of other dairy breeds of cows and bulls can be attributed to the ICBF philosophy of utilising all available data to supply information useful to farmers. It can also be attributed to the desire for suitable information to guide dairy farmers in the selection of replacement cows within, as well as between, breeds. Where domestic information is absent, farmers have resorted to the selection of bulls of other breed based on foreign information which does not include performance records for the bulls’ daughters in Irish herds. Evidence of genotype by environment interactions suggests that ranking of bulls in different environments might be different when genetic evaluation is based on performance records in the different environments.

Setting up a breeding program involves the definition of a breeding goal and the design of a scheme capable of delivering genetic progress in line with the set goal. The practical aspect of setting up a cattle-breeding program is very much to do with the management of people and resources as much as it has to do with the application of principles of genetics and animal breeding. Each aspect of the breeding program involves many processes, individuals and, sometimes, organisations.

The effect of reducing the frequency of official milk recording and the number of recorded samples per test-day on the accuracy of predicting daily yield and cumulative 305-day yield was investigated. A control data set consisting of 58 210 primiparous cows with milk test-day records every 4 weeks was used to investigate the influence of reduced milk recording frequencies. The accuracy of prediction of daily yield with one milk sample per test-day was investigated using 41 874 test-day records from 683 cows. Results show that five or more test-day records taken at 8-weekly intervals (A8) predicted 305-day yield with a high level of accuracy. Correlations between 305-day yield predicted from 4-weekly recording intervals (A4) and from 8-weekly intervals were 0.99, 0.98 and 0.98 for milk, fat and protein, respectively. The mean error in estimating 305-day yield from the A8 scheme was 6.8 kg (s.d. 191 kg) for milk yield, 0.3 kg (s.d. 10 kg) for fat yield, and -0.3 kg (s.d. 7 kg) for protein yield, compared with the A4 scheme. Milk yield and composition taken during either morning (AM) or evening (PM) milking predicted 24-h yield with a high degree of accuracy. Alternating between AM and PM sampling every 4 weeks predicted 305-day yield with a higher degree of accuracy than either all AM or all PM sampling. Alternate AM-PM recording every 4 weeks and AM + PM recording every 8 weeks produced very similar accuracies in predicting 305-day yield compared with the official AM + PM recording every 4 weeks.

Cow survival and fertility are together with calving difficulty, gestation length, calf mortality, weaning weight and cull cow carcass weight proposed in a maternal beef cattle index. Beef breeding values for cow survival and fertility are predicted with one multiple trait sire model for reappearance, lifespan and calving interval including beef, dairy and crossbred information. Since information on cow survival or reappearance is scarcely available in historical beef data, reappearance curves are proposed as survival indicators for animals that did not reappear within 300-450 days. Different breed effects were accounted for with a regression on the sire and dam breed percentage. Average lifespan for beef breeds was almost 3 years and survival ranged from 0.73 to 0.79 in parities 1 to 3. This was slightly lower than for dairy breeds with the difficulty of having more missing and censored records. Reappearance fractions as survival indicator were included in 8.3% to 2.4% of the censored records in parities 1 to 4. Heritability (first parities only) was 2% for cow survival and calving interval respectively and 7% for lifespan; correlations were -0.37 and -0.47 for reappearance and lifespan with calving interval and 0.91 for reappearance with lifespan. Using lifespan, reappearance fractions and multiple breed data, including dairy and crossbreds, allowed multiple breed evaluation for cow survival and fertility in Irish beef cattle.

We have recently developed a Fertility Index for UK dairy cattle (Wall et al., 2003). After examining national data it was decided that the Fertility Index should be based on sire PTAs for calving interval (CI) and nonreturn rate (NR) after 56 days weighted by their relative economic weights. However, just under half of the available bulls have no milking daughters in the UK. It would take about 4 years from the time of first use in the UK, for a bull to have sufficient daughters for a reliable fertility proof. Waiting this long for fertility information on which to base selection decisions will slow genetic progress and is undesirable as many of these bulls could have fertility proofs in their country of first test. This study examines the feasibility of converting foreign fertility proofs to UK equivalents.

Presently, the national evaluation for fertility in Ireland is carried out for calving interval and survival using a 13 trait animal model. Breeding values are predicted from a joint analysis of calving interval, survival and milk yield in the first 3 lactations and 4 linear type traits (Angularity, Body condition score, Foot Angle and Udder depth) as predictors of calving interval and survival (Olori et al., 2002 and Pool et al., 2002).

Poor fertility has become a major reason for involuntary culling of dairy cows in the UK. Research in the UK has recently developed a Fertility Index for dairy cattle. After examining national data it was decided that fertility proofs in the UK would be based on calving interval (CI) and non-return rate after 56 days (NR56) weighted by their relative economic weights (independent of culling). Sire PTAs for these traits were produced from a hexavariate BLUP run of fertility traits (CI, NR56; days to first service (DFS) and number of inseminations per conception (INS)) and correlated traits (milk yield in kgs at test nearest day 110 (MILK); body condition score on a scale of 1-9 (BCS)). There was an unfavourable genetic correlation between the fertility traits and milk yield and BCS. PTAs produced were similar in size and range to those produced in other studies and genetic trends were as expected. Results are encouraging and have lead to a fertility index that will help to improve national dairy cow fertility (Wall et al., 2003).

There is an intricate relationship between milk production, fertility and survival of cows, which is further confounded by management decisions on the farm. Holsteinization and selection for high milk production can be associated with reduction in cow fertility (Pryce et al., 1998; Silvia, 1998; Harris and Winkelman, 2000) because of its impact on physiological factors affecting reproduction such as energy balance, ovarian function, heat detection and conception in dairy cows (Buckley et al., 2000; Snijders et al., 2001; Westwood et al., 2002).

Poor cow fertility has been identified as a growing problem in Irish dairy herds. In this seasonal calving and the grass based production system, poor fertility results in a significant loss in farm income (Veerkamp et al., 2001) due to forced culling or a shift in calving pattern. In order to arrest this trend, subsequent calving interval (CIV) and survival to the next lactation (SUV) has been introduced as objective traits in the dairy breeding goal, as measures of cow fertility and longevity (Veerkamp et al., 2001). Calving interval was chosen as a measure of fertility because of its relationship with direct measures of fertility, direct relevance in the seasonal calving production system and availability of data from milk records.

In a grass-based production system with seasonal calving, fertility is of major economic importance. A delay in conception due to poor fertility prolongs intercalving interval and causes a shift in calving pattern, which can lead to culling. Calving interval (CIV) information is readily available from milk records; analyzing it, however, presents a problem, as it is only available for cows that conceive and calve again. Calving interval should therefore be treated as a censored trait. In this study, survival to the next lactation (SUV) was analyzed jointly with CIV in a multivariate linear model to account for the selection in CIV data. Genetic parameters for first lactation calving interval were estimated with a sire model for Holstein Friesian cows in Ireland. SUV was preadjusted for production within herd-year-season (HYS), while milk yield was included as a third trait in the analysis to account for the large effect it has on both traits. The residual covariance between CIV and SUV was fixed as 3 times the sire covariance within the model, as it was inestimable because of the structure of the data. Breeding values were estimated with various models to test the effect of culling and milk yield. Heritability was 0.04 +/- 0.006 for CIV and 0.01 +/- 0.003 for SUV, while the genetic correlation between them was -0.28 (+/-0.11). The genetic standard deviation was around 4% for SUV and 7 d for CIV. Sire predicted transmitting abilities for progeny tested bulls ranged between -5 and 3% for survival rate and between -4 and 8 d for calving interval. Differences between the best and worst bull varied with model. Including SUV and milk yield as traits in the model reduced the mean and variance of sire predicted transmitting abilities but increased the coefficient of variation by 30% compared with the univariate model. The current model is expected to account for most of the genetic variation in fertility that is possible from calving dates and future extensions, such as the use of linear type trait or additional lactations for predicting survival, appear straightforward. These traits now form part of the national index for selecting dairy bulls in Ireland.