Jenny Yngvesson

Aggression between unacquainted pigs—sequential assessment and effects of familiarity and weight

Abstract Staged paired encounters between 74 pairs of 7–8 weeks old unacquainted piglets were studied. In 37 of the pairs, the pigs were pre-exposed to their opponents by keeping them for 24 h in small pens separated by wire net. The controls were kept in the same pen, separated by solid wooden walls. In 41 pairs, there was a median weight difference of 23%, and in 35 pairs the weight differed by less than 10%. The sequential assessment theory was applied to generate specific predictions about the effects of pre-exposure and of weight differences. The following results were in agreement with predictions from theory: contests were structured into a first nosing phase and a second biting phase. During the nosing phase, the rate of nose contacts was linearly dependent on the length of the phase, and during the biting phase, rate of biting was linearly dependent of length of phase. Prior to the point where one pig signalled that it gave up, there was no difference in emission rate of nosing or biting between the contestants, whereas the loser performed significantly less biting after giving up. The durations of the phases were independent of each other. The duration of the first phase was independent of weight asymmetry. Pre-exposed pairs had a reduced nosing phase, but not a reduced biting phase. However, not in agreement with predictions, weight asymmetry did not shorten contest length or biting phase and did not reduce the proportion of pairs escalating contests to overt fighting. It was also found that the variance of phase durations was smaller in pre-exposed pairs, indicating that the information obtained by the animals modified the sequence of the fights, which is not predicted by theory. In conclusion, the sequential assessment game provided explanations for a large part of the contest behaviour of pigs, but some findings were not in agreement with theory. Pre-exposure of unacquainted pigs may be a way for farmers to reduce the time of initial fighting between newly mixed pigs.

Rearing without early access to perches impairs the spatial skills of laying hens

The effect of rearing with and without perches on the spatial ability of domestic hens (Gallus gallus domesticus) was investigated. No access or late access to perches during rearing has been shown to increase the later prevalence of floor eggs and cloacal cannibalism in loose-housed laying hens. This may be explained by either the birds reared without perches have difficulty using perches due to low muscle strength, lack of motor skills, and inability to keep balance, or they have impaired spatial skills necessary for moving around in three-dimensional space. These alternative explanations are not mutually exclusive.Thirty, day-old chicks were randomly allocated into two equal groups and reared in litter pens, one with access to perches (P+) and one without (P-). At 8 weeks of age, all birds were given access to perches, and by 15 weeks, all birds were using perches for roosting at night. At 16 weeks, 10 birds from each group were tested in pens where food was presented on a wire mesh tier 40 cm above the ground (T40). Three consecutive tests, with increasing difficulty for the bird to reach the food, were then performed. Firstly, the food was presented at 80 cm above the ground but with the tier at 40 cm still present; secondly, food was presented on the tier at 80 cm; and then, finally, with the food on a 160 cm high tier with the tier at 80 cm still present. All birds were food deprived for 15 h before each test and the time from the bird entering the pen until reaching the food was recorded. There was no difference in the time to reach the food between P+ and P- birds in the T40 test. But as the difficulty of the task increased, the difference between the P+ and P- birds became significant, with the P- birds taking a longer time to reach the food or not reaching it at all. Since there was no difference between P+ and P- in the T40 test, it seems reasonable to suppose that the later differences did not depend on differences in physical ability. Therefore, the results may imply that rearing without early access to perches, in some ways, impairs the spatial cognitive skills of the domestic hen.

Body size and fluctuating asymmetry in relation to cannibalistic behaviour in laying hens

Abstract We studied cannibalism in laying hens, Gallus gallus domesticus . From farms experiencing high mortality caused by cannibalism, we collected cannibalistic birds, birds with injuries caused by pecking and control birds. All factors such as farm, bird hybrid and age were identical within a set of three birds, but differed between trios. Based on predictions from studies on wild animals, we hypothesized that cannibalistic laying hens would be larger and victims smaller than control birds, and that victims would in some way be less fit than control birds. In addition, since cannibalism in the wild is usually shown by individuals under adverse conditions, we hypothesized further that under commercial conditions cannibalistic individuals would be those that experience the environment as more stressful than others in the flock. Since fluctuating asymmetry is thought to be positively correlated with low stress-buffering capacity, we expected cannibals and victims to be more asymmetrical than other birds. As predicted, cannibals were heavier and taller than other birds and both victims and cannibals were more asymmetrical than control birds

Individual production differences do not explain cannibalistic behaviour in laying hens

1. Sixty-three laying hens were collected from 5 commercial farms experiencing outbreaks of cannibalism. It is known that cannibalistic behaviour varies strongly between hybrids and between individuals of the same hybrid. The aim of this study was to test specific hypotheses about the causation of cannibalism by comparing matched individuals varying in their cannibalistic behaviour. 2. To investigate feed efficiency, egg production and feed consumption, data were collected over 30 d. Nutrient deficiencies have been associated with outbreaks of cannibalism and we hypothesised that cannibals are more feed efficient than their flock mates and, therefore, more susceptible to transient nutrient deficiencies or imbalances that trigger cannibalistic behaviour. 3. Video recordings were made of victims of cloacal cannibalism and their matched controls during oviposition. Victims were expected to have longer oviposition durations and a higher incidence of short-term cloacal prolapses than controls, because the starting point for cannibalism is often suggested to be pecking at the red mucosa of the victim during, or just after, oviposition. 4. Oviduct swab samples were taken from surviving victims of cloacal cannibalism and their matched controls 4 weeks after the cannibalistic attack. If peck wounds provide a route for subsequent bacterial invasion of the reproductive tract, victims would be expected to have greater bacterial colonisation of the oviduct. 5. Mortality within each matched trio was recorded over a 23-month period after the cannibalistic attack. Victims that survived a cannibalistic attack were expected to have reduced longevity compared to controls and cannibals. This could occur if they developed secondary infections as a result of the cannibalistic attack, or if they had poorer health even before the attack. 6. No significant differences were found between cannibals, victims and controls in feed efficiency or any of the production variables measured. Victims of cloacal cannibalism did not expose their cloacal mucosa more, or for longer, than matched control hens during oviposition, and had no more bacteria in their oviduct. Victims tended to die sooner than their matched cannibals or cannibals during a 23-month period after a cannibalistic attack.

Behaviour in one fast-growing and one slower-growing broiler (Gallus gallus domesticus) hybrid fed a high- or low-protein diet during a 10-week rearing period

ABSTRACT This study compared behavioural time budgets, presence of comfort behaviours and social behaviours in two different broiler genotypes (the fast-growing Ross 308 (R) and the slower-growing Rowan Ranger (RR)) fed organic diets with high (17.0% crude protein (CP)) or low (14.5% CP) protein content during a 10-week rearing period. 429-day-old chicks (218 R and 211 RR, respectively) were included in the study and behaviour was recorded at 2, 6 and 9 weeks of age. The results showed no effect of diet treatments but that R broilers were less active and sat, ate and drank more frequently than RR broilers, which stood and perched more frequently. However, both hybrids showed decreasing activity and foraging behaviour with increasing age, while time spent eating and sleeping was approximately similar over the entire rearing period.

Let me sleep! Welfare of broilers (Gallus gallus domesticus) with disrupted resting behaviour

ABSTRACT Perching is important for broiler welfare, however, hampered by body weight. In a mixed flock, resting behaviour and location were compared between three broiler hybrids (Rowan Ranger, Hubbard CYJA57 & Ross 308; n = 100/hybrid), differing in growth. Rearing was in a large littered pen (1.84 birds/m2), with perches. Behaviour and position was observed in focal birds on daytime and as group scans on daytime (days 11, 45, 61 and 80) and night-time (days 63, 70 and 77). Birds were slaughtered at 84 days and accumulated mortality in fast-growing birds was 20% and 2% in slow-growing. Resting frequency did not differ though fast-growing broilers perched less and lower, at night (P < .01) and day (P < .01). On daytime, males disturbed birds resting on the floor more than females did (P < .05). Disrupted rest is a potential welfare issue in broilers, hence perches or other elevated structures would improve welfare.