From two weeks of age female broiler breeder chickens were fed either on a commercial daily ration (R), twice that amount (2R), or ad libitum (AL). Motivation to eat in R and 2R birds was compared every third week with that of AL birds subjected to 3-72h food deprivation. AL and 2R birds grew three and two times faster than R birds to 20 weeks, and AL birds ate two to four times as much per day as R birds, depending on age and on whether birds of the same age or weight were compared. When feeding motivation was measured in 16min tests with an operant procedure, numbers of responses by R and 2R birds were not related in a consistent way to the time since their daily meal ended Responses by AL birds were correlated consistently with the preceding period of food deprivation, but it was not possible to express hunger in R and 2R birds in terms of equivalent deprivation in AL birds, as intended, because feeding motivation in the two situations differed in magnitude. Instead, it was calculated that motivation to eat in R and 2R birds, from 8 to 20 weeks, was 3.6 and 1.9 times greater than that of maximally (72h) deprived AL birds. Another measure of feeding motivation with different birds, rate of eating in 10min tests, produced a similar index of hunger with 2R but not R birds. It is concluded that broiler breeders fed on the commercial ration eat only a quarter to a half as much as they would with free access to food, and that they are highly motivated to eat at all times. The modern broiler breeder industry is caught in a welfare dilemma, since on the one hand stock appear to be chronically hungry, while on the other hand less severe food restriction leads to reduced fertility and health problems.

Twelve Isa Brown hens (Gallus gallus domesticus) were trained to open a locked door for access to a pen containing an enclosed nest box (‘nest test’) and to return to a home pen containing food, water, litter and a perch (‘home test’). The door was connected to a computer-controlled load cell, which recorded work exerted on the door and unlocked the door when the hen had exceeded a predetermined workload. Following training, the workload was set at 10 Ns, and hens received one nest test per day at 80, 60, 40 or 20 min prior to oviposition, and then one home test per day after 1, 2, 3 or 4 h confinement in the nest pen. As oviposition approached, hens showed a higher work-rate for access to the nest pen, showed a shorter latency to use the nest box and spent a greater proportion of their visit time in the nest box. Hens also worked harder for the home pen, showed a lower latency to feed and spent more time feeding after their return as period of confinement increased. The hens’ work-rate for the nest pen at 40 min prior to oviposition was comparable with their work-rate for the home pen after 4 h confinement, while their work-rate was at its highest in nest tests at 20 min prior to oviposition. The technique appears to be a valid means of assessing the importance of environmental resources, the values of which vary with time. The results suggest that hens place a higher value on gaining access to a discrete nest-site prior to oviposition than they do on gaining access to food following 4 h food deprivation.

Pigs undergoing an alarming experience may produce olfactory stimuli (pheromones) in their urine, which may have consequences for the welfare of other pigs exposed to these stimuli. Twelve young adult female pigs (gilts) were restrained for 30min in feeding stalls (a potentially alarming experience) and any urine produced was collected. Six gilts had previously experienced the procedure (experienced gilts), and six gilts had not (inexperienced gilts). The gilts’ behaviour was recorded over the 30min period. The inexperienced gilts exhibited significantly more escape behaviour (P < 0.001) and less exploratory behaviour (p < 0.05) than those which had prior experience of restraint.

Twelve weaner pigs (30 days old) were subsequently individually exposed to the urine from inexperienced gilts, the urine from experienced gilts and a water control in an open field test. The ambulation score in the open field test was significantly higher (P < 0.01) when weaners were exposed to the urine from inexperienced gilts compared to the other two treatments. The weaners were then presented with a feeder containing feed sprayed with the treatment samples. The weaners took significantly longer to approach the feeder sprayed with the urine from the inexperienced gilts (P < 0.05) and performed significantly more eating bouts (P < 0.05) that were significantly shorter compared with the water control (P < 0.05). Total number of vocalizations (P < 0.01) and grunts (P < 0.05) were significantly greater in those pigs exposed to the inexperienced gilts’ urine. These results indicate that urinary alarm pheromones were produced by the inexperienced gilts during restraint in the feeding stall and that these pheromones significantly modified the behaviour of weaner pigs subsequently exposed to them. Exposure to such pheromones is likely to adversely affect the welfare of pigs.

It has been suggested that feeding motivation, and hence the incidence of certain abnormal behaviours, may be reduced by the gastro-intestinal distension which results from the ad libitum provision offoods with a high water-holding-capacity (WHO. Therefore, the aim of this experiment was to test the hypothesis that feeding motivation is inversely proportional to the WHC of meals which supply the same level of nutrients. Eight male pigs (initial body weight 54·0 (s.d. 5·76) kg) were offered a series of four foods which possessed increasing WHC due to a linearly increasing inclusion of dried citrus-pulp (2·18, 3·52, 5·60 and 6·92 g water per g dry food for LB, MLB, MHB and HB), but all with similar ratios of digestible energy (DE) to crude protein and minerals. The experimental treatments were allocated in two 4X4 Latin squares with blocks of 6 days separated by a 4-day change-over period. On each day the pigs were given food twice (09.00 h and 16.00 h) to provide the same level of scaled DE across the meals of each treatment. The resulting level offeeding motivation was measured in two successive tests at 30-min intervals before, and eight successive tests at 30-min intervals after, the ingestion of the first meal using a second-order operant conditioning schedule; a methodology which requires pigs to press a paddle to obtain a feeding-related stimuli (CS). It was found that the number ofCS earned pre-feeding was not affected by treatment (17·2, 17·2, 17·6 and 17·5 (s.e.d. 1·58) CS per test for LB, MLB, MHB and HB; P > 0·05), whereas, the number of CS earned post feeding was significantly affected by treatment (16·6, 15·5, 14·6 and 13·8 (s.e.d. 1·15) CS per test for LB, MLB, MHB and HB; P < 0·001). Within each treatment, the number ofCS earned did not alter significantly across any of the time-periods post feeding. As the number of CS earned has been shown to be a reliable indicator of feeding motivation, the results from this experiment support the hypothesis that feeding motivation is inversely proportional to the WHC of iso-energetic meals.