The routine mixing of pigs causes aggression that cannot be greatly reduced by low-cost environmental changes. The variability and heritability of aggressiveness are discussed and both appear adequate to make selection against aggressiveness worthwhile in grower-stage pigs. Selection would require rapid phenotyping of many animals for which a validated indicator genetically correlated to aggressive behaviour is required. Three potential indicators are discussed (attack latency, number of skin lesions and relationship to non-social behavioural traits). Attack latency correlates with post-mixing aggressiveness under research conditions but attacks are delayed under commercial conditions reducing the practicability of the trait for selection. Correlations between aggressiveness and responses to non-social challenges, such as the back-test, are not always consistent. Lastly, the counting of skin lesions is rapid, and the number of lesions has a moderate heritability and is genetically correlated with involvement in aggressive behaviour. The wider effects of selection against post-mixing aggressiveness are discussed. Examining the behavioural strategies of unaggressive pigs, especially their response to defeat, would reveal how selection may alter aggressive tactics. Selection against lesions from mixing is also expected to reduce their number in more stable social conditions, but the implications for aggression between sows and that of sows towards their piglets and humans needs to be investigated. Aggressiveness is genetically correlated with response to handling involving components of social isolation, human presence and novelty. Identifying how unaggressive pigs respond to other challenging situations differing in these components may be worthwhile. Selection against aggression using skin lesions appears to be achievable although the full value of this would benefit from estimations of the genetic correlations with the traits outlined above.

Farm assurance schemes can set standards to assure compliance with specific requirements relating to animal welfare. As such, standards can be set to address genetic-related welfare problems in farm animals, such as those associated with fast growth rates in meat chickens (broilers) (Gallus gallus domesticus). Based on discussions with broiler breeding companies, broiler producers and in line with published research, the RSPCA placed a maximum limit on the genetic growth rate potential of broilers that could be used within its own farm assurance scheme — Freedom Food. Despite the introduction of this requirement, the number of birds reared on the scheme increased from 25 million to 55 million per year over a three-year period, with all of these birds meeting the genetically slower growing requirement. In addition, the two largest global broiler breeding companies responded to this change in the market by each developing a genetically slower growing bird. This demonstrates that assurance schemes can have a pivotal role in tackling genetic welfare problems in farm animals, such as those associated with fast growth in broilers.

The breeding of domestic dogs for dog fighting has resulted in numerous genetic alterations in a breed widely acknowledged to be the most successful fighting dog: the American Pit Bull Terrier (APBT). Much of the genetic foundation underlying the motivation and ability for pit fighting can be traced back to the earliest use of dogs for hunting purposes and continued through the selective breeding for use of dogs in wars and bull and bear baiting. In the development of the APBT as a fighting dog, there were two main breeding criteria. The first was, and remains, fighting success. The trait most prized by breeders of fighting dogs and considered most contributory to fighting success is ‘gameness’, which is the perseverance at a task even under extreme adversity, such as injury, pain, or fatigue. The second criterion was the absence of human-directed aggression. Since dogs are handled extensively before, during, and after the fights, dogs that showed aggression toward humans were eliminated from the gene pool. Indeed, anecdotal reports suggest that breeding may have been carried beyond that of simply selecting against human aggressiveness to a degree of enhanced affinity for humans. The result is that today's fight-bred APBT is genetically predisposed — but not predestined — to aggressiveness toward other dogs and a strong social attraction to humans. The human affinity trait is a highly valuable characteristic that ought to be preserved. With the appropriate breeding decisions, the power of genetic selection suggests that this goal, along with normalising the genetic disposition for conspecific aggressive tendencies, should be ultimately achievable.

Primates are bred in captivity for a number of purposes, from zoo-based captive breeding programmes for conservation to breeding for biomedical research. In each case, breeding animals that are fit for purpose, either as viable candidates for reintroduction or as valid research models, has presented challenges and resulted in steep learning curves. The breeding of animals for biomedical research has become increasingly focused on the production of animals that are less stressed by captive (specifically laboratory) environments. This is because elevated, particularly chronic, stress responses can result in altered physiological, neurological and behavioural states that have the potential to compromise the validity of scientific results. Selective breeding in captivity to, for example, maximise production, select for docile temperament or specific genotypes for biomedical research, is likely to be counter to natural selective pressures for evolutionary fitness. Given that many natural selective pressures active in the wild are absent in captivity, this paper reviews the selective breeding of primates (especially Old World monkeys) in captivity, its potential negative effects, and options that exist for ameliorating these negative effects.

Animal production is a fundamental component of the food supply chain, and with an increasing global population production levels are set to increase. Ruminant animals in particular are valuable in their ability to convert a fibre-rich forage diet into a high-quality protein product for human consumption, although this benefit is offset by inefficiencies in rumen fermentation that contribute to emission of significant quantities of methane and nitrogenous waste. Through co-operation between plant and animal sciences, we can identify how the nutritional requirements of ruminants can be satisfied by high-quality forages for the future. Selective forage plant breeding has supported crop improvement for nearly a century. Early plant breeding programmes were successful in terms of yield gains (4% to 5% per decade), with quality traits becoming increasingly important breeding targets (e.g. enhanced disease resistance and digestibility). Recently, demands for more sustainable production systems have required high yielding, high-quality forages that enable efficient animal production with minimal environmental impact. Achieving this involves considering the entire farm system and identifying opportunities for maximising nutrient use efficiency in both forage and animal components. Forage crops of the future must be able to utilise limited resources (water and nutrients) to maximise production on a limited land area and this may require us to consider alternative plant species to those currently in use. Furthermore, new breeding targets will be identified as the interactions between plants and the animals that consume them become better understood. This will ensure that available resources are targeted at delivering maximum benefits to the animal through enhanced transformation efficiency.

Traits such as disease resistance are costly to evaluate and slow to improve using current methods. Analysis of gene expression profiles (e.g. DNA microarrays) has potential for predicting such phenotypes and has been used in an analogous way to classify cancer types in human patients. However, doubts have been raised regarding the use of classification methods with microarray data for this purpose. Here we propose a method using random regression with cross validation, which accounts for the distribution of variation in the trait and utilises different subsets of patients or animals to perform a complete validation of predictive ability. Published breast tumour data were used to test the method. Despite the small dataset (n < 100), the new approach resulted in a moderate but significant correlation between the predicted and actual phenotypes (0.32). Binary classification of the predicted phenotypes yielded similar classification error rates to those found by other authors (35%). Unlike other methods, the new method gave a quantitative estimate of phenotype that could be used to rank animals and select those with extreme phenotypic performance. Use of the method in an optimal way using larger sample sizes, and combining DNA microarrays and other testing platforms, is recommended.

The common carp is one of the main aquaculture species in the world. Despite this, most of the production is carried out using unselected strains. Selective breeding for fast growth has not proven to be effective in this species, but other traits (disease resistance, shape) could be successfully selected for. Most heritability estimates in the literature are unreliable due to environmental biases, but complementary results from population genetics and comparison of strains seem to indicate that there should be a potential for selective breeding in this species, including selection for growth rate, provided the base populations are variable enough (e.g. synthetic strains). New techniques such as parentage assignment with microsatellites and use of doubled haploid progenies may help describe much more accurately, without environmental bias, the genetic determination of traits of interest in the carp. This could be a new opportunity to design efficient breeding programs in this important species.

The change in the proportional distribution of bone weight within the carcass skeleton from birth to maturity was examined in rams and ewes from flocks of Australian Merino sheep selected for high (weight plus) and low (weight minus) weaning weight and from a randomly selected control flock. Data from 140 animals (106 immature, 34 mature) were used. Shape parameters for the long bones of the limbs in the 34 mature animals were derived by determining the allometric relationship between bone length, diameter and individual bone weight.

Selection for increased and decreased weaning weight resulted in a concomitant increase and decrease in mature size and total bone weight. In the weight plus group, total bone as a proportion of body weight also increased but selection had little effect on the proportional distribution of bone weight within the skeleton at any stage of maturity. This was the product of similar growth patterns within the skeletal system aiming towards a similar mature distribution pattern for each strain.

Within the strains of different mature size there was a difference between mature rams and ewes in both total bone weight as a proportion of body weight and in the proportional distribution of this bone weight. This was associated with differences in the maturing patterns of the bones of the hindlimb and the pelvic girdle.

Neither selection nor sex affected the relationship between bone shape and bone weight, although the difference in bone weight between the strains and sexes at maturity meant that they also differed in bone shape at this point.