Some specific welfare issues
Most animals, other than primates, do not behave maternally towards their offspring except when they have just given birth. But although the behaviour is short lived for the mothers, its impact on the offspring may be lifelong.
Scientists are trying to understand more about maternal behaviour by identifying the mother's requirements for stress-free birth, and the impact of maternal behaviour on offsprings' ability to cope with their environment. Results could contribute to optimising the quantity and quality of
maternal care received by livestock and laboratory animals. In semi-natural environments, domestic pigs isolate themselves from the herd one to two days before giving birth. They build a nest in
which to rear the piglets. Collaborative research between scientists at the Universities of Bristol and Oxford on a commercial outdoor pig farm sourced by Cambac JMA Research is investigating how individual sows naturally vary in their maternal skills. A total of around fifty sows is being studied and the aim is to identify the key factors of maternal behaviour that benefit the piglets, for example in terms of their growth, health and subsequent tolerance of handling by humans.
There are sound practical reasons for wanting to understand more about the way mother animals recognise and bond to their offspring. Such understanding could help to improve the adoption of orphaned offspring by foster mothers and suggest ways of overcoming the reluctance of mothers to look after their offspring in captivity - a problem that often occurs in attempts to breed endangered species. Practical protocols for fostering orphan lambs are described on page 47.
Research at Babraham Institute and the University of Cambridge over the past decade showed that maternal bonding between a ewe and her lamb is induced and stimulated by two principal factors: hormonal changes of pregnancy and the stimulation and dilation of the cervix and vagina during birth. The latter operates at least in part by inducing release of the hormone oxytocin in the brain, and into the bloodstream from whence it stimulates contraction of the uterus.
Smell is the principal way a ewe recognises and bonds with her lambs following birth and many cells in parts of the brain that process smell become tuned to respond to the specific odour cues from their wool. This process is triggered by feedback signals from the cervix and uterus promoting the release of oxytocin and noradrenaline in the brain. This increases the activity of the cells responding to the lambs odour and they release more of the transmitter glutamate. This acts via the nitric oxide signalling pathway to further promote its own release and cause permanent changes to
the synapses to make them more responsive to the lamb's odours whenever they are encountered in the future. In this way, the chemical signals in the ewe's brain help her to remember the smell of her lamb she has bonded with and to reject the attentions of all other lambs.
All of these processes, pregnancy, natural birth and smell are necessary to establish maternal
bonding between ewes and their offspring. Maternal behaviour and bonding does not occur, for example, with lambs delivered by caesarean section. However, as described on page 47, ewes can be persuaded to foster lambs that are not their own.
Importance of maternal care
Scientists at the Babraham Institute have shown that both lambs and goat kids learn their preference for which species to socialise and mate with from their mothers. Thus, lambs raised by goats grow up preferring to socialise and mate with goats rather than sheep even if they are raised together with a lamb brother or sister and with other sheep in the flock. The same happens with goat kids raised by sheep, and in both cases the effects of maternal social education are much stronger in males
than females. Indeed, the males continue to prefer their adoptive mother's species even after 5 years of living only with their own species. The physical basis for this species preference has been shown to be visual cues from the mother's face. This shows how important the maternal offspring bond is for determining the social likes and dislikes of the offspring in these two species and
complements other work showing that strong and enduring dietary preferences are also learned from mothers. It also underlines, from a welfare point of view, how important it is for offspring to receive appropriate maternal care and delivers a note of caution to captive breeding programmes aiming to raise offspring from endangered species using foster mothers from other more common closely related ones. Animals produced this way may not grow up to be strongly attracted to their own species.
Scientists at the University of Oxford are investigating the effects of maternal grooming in rodents. There is evidence that maternal grooming of new-born rats lowers the
sensitivity of the hormone system that is activated during stress. This effect lasts as the rats grow and develop; indeed, it lasts into old age. It is unclear, whether rats that receive maternal grooming find situations less stressful than those that have been deprived of maternal grooming, or whether they just react less. If the former applies, then ensuring high quality maternal grooming could be one way of enhancing the welfare of captive rodents, including laboratory mice and rats.
Scientists at the University of Oxford are looking at the effects on juveniles of the early loss of their mothers. In many laboratory and agricultural situations, young animals are removed from their mothers earlier than would occur in the wild or in more naturalistic situations. In primates - including ourselves - the early loss of the mother can make individuals more vulnerable to stress.
Researchers are therefore seeing if this is also true for other types of mammal. If it is, leaving young animals longer with their mothers could be an effective way of making them better able to cope with stress.
Broodiness is a hen's natural tendency to cease laying and incubate a batch of eggs. It can cause regression of the ovary and poor egg production in broilers, turkeys and waterfowl. Broodiness is likely to become more of a problem as egg producers increasingly switch to more extensive systems in which birds can express natural nesting behaviour.
White Leghorn hens, unlike most other breeds of poultry, generally lack broody behaviour. This is of practical significance to poultry breeders as it offers them the opportunity to incorporate White Leghorn genes into their stocks to suppress broodiness. However this option is not open to breeders of other types of poultry. Attempts to eliminate broodiness by conventional selection have had limited success. Researchers at the Roslin Institute have identified the genes causing the broody
trait and are now looking at the possibility of eliminating it by marker-assisted selection.
For some people, eliminating an innate behaviour in this way may be regarded as unethical, but it may reduce stress in layer hens that are unable to perform the behaviour in farmed conditions.
Animals in captivity commonly perform meaningless "rituals" or stereotypic behaviour. These may be new behaviours or a re-directed natural behaviour such as nibbling. Scientists are investigating the external environmental factors that might be involved in triggering stereotypic behaviour, and the genetic and physiological characteristics of individual animals that may make them more susceptible.
Whilst the overall aim is to aid the design of husbandry systems which enable animals to perform their normal behaviours, it is important to try to understand what causes stereotypic behaviours, and whether they can be transmitted from one animal to another through social interactions.
Horses, particularly those that are intensively managed, can show a variety of stereotypic behaviours including biting on part of the stable, or "weaving" (swaying from side to side). Up to around one in twenty horses may behave in such ways.
Many owners believe that horses copy these behaviours from each other, but this was not found to be the case in experiments at the University of Bristol. There, horses accommodated next door to one that was "weaving" showed very little if any likelihood to copy the behaviour.
There is evidence, however, that stable-biting is associated with dietary factors. It seems that stereotypic behaviours typically start in response to a welfare problem, such as an animal being thwarted from performing a particular behaviour, and that they later become habitual and continue even after the problem has passed. In other words, stereotypic behaviours may be "scars" from
previous poor welfare rather than indicators of current welfare problems.
Stereotypic behaviour may not be directly harmful to an animal, although there may be secondary effects. For example, horses that "weave" and stable-bite can damage their leg and neck muscles respectively. There is however, a major welfare issue, and productivity problem, associated with feather pecking in poultry.
Feather pecking, in which a bird pecks at the plumage of another, seems to be a re-directed foraging or exploratory pecking behaviour. It is not caused by aggression, although it causes severe pain and can be associated with increased cannibalism in flocks.
There is some evidence that once a bird's plumage has been pecked at and ruffled it becomes more attractive to other feather peckers. However, research at the University of Bristol, that allowed chicks to grow up watching commercial hens that feather pecked to a mild degree only, indicated that birds do not learn feather pecking from each other. Similarly, Roslin scientists found that feather
pecking was not increased in chickens from an experimental line showing low feather pecking when they were reared with birds from a high pecking line.
Stereotypies are also common in laboratory animals. For example, in many strains of mice, some individuals perform stereotypies when kept in traditional laboratory cages, repetitively jumping up and down or repeatedly mouthing the bars of their cage.
Research at the University of Liverpool has shown that these movements derive from attempts to escape. For example, if there is a lid on the cage-top that is regularly opened, that is the place where mice direct most of their bar-mouthing, particularly if they have been handled or have escaped via that route. Mice confined in traditional cages make more escape attempts, with the potential for developing stereotypies, than those housed in larger, open-topped enclosures. In rats, aggression between cagemates may increase their attempts to escape: those in groups where there are high levels of fighting spend more time trying to escape and show greater physiological signs of stress. Although evident in mice and rats of both sexes, the studies so far suggest that females often try harder to escape and may be more susceptible to developing stereotypies than males.
Research at Oxford, again on laboratory-housed rodents, has also shown why it is these behaviours can be so strange-looking and so incredibly persistent. They investigated these behaviours using techniques from experimental psychology. Humans with autism or schizophrenia, and animals treated with stimulant drugs, show stereotypies that resemble those of caged animals, but in these subjects, the behaviours are known to arise from changes in parts of the brain responsible for organising and sequencing behaviour properly. These brain regions, known as the basal ganglia, can make individuals hyperactive, prone to rapidlyshifting between different activities, and yet also abnormally persistent, prone to getting stuck in pointless behavioural ruts.
Could the same thing be going on in captive animals? The Oxford researchers showed that in caged voles (a mouse-like rodent), high levels of barmouthing stereotypy were similarly part of a
whole suite of behavioural symptoms, including increased activity, increased rates of switching between different types of behaviour, and also abnormal persistence: the most stereotypic voles had no trouble learning to run a maze to reach a sugar reward, but when the sugar was removed, they took far longer than other animals to unlearn the task and give up trying. This work suggests that
captivity can have profound effects on the how the brain functions.
Source: The Biotechnology and Biological Sciences Research Council - Summer 2002