G.M. Cronin

The effect of individual and group housing on behavioural and physiological responses related to the welfare of pregnant pigs

Abstract The effects of four housing treatments (neck-tethers, stalls, a group indoors and a group in a paddock), imposed at 3–5 weeks after mating, were determined on the behaviour and physiology of 24 pigs. Behaviour observations were made 2–3 days after the treatments began and 4 and 9 weeks later, and physiological measurements were made 18 and 46 days after the treatments began. Pigs in tethers spent less time in active behaviours than all other treatments, and the pigs housed in stalls showed increased amounts of oral—Nasal behaviours such as manipulation of drinkers and licking/biting pen components (7% of observations) compared to all other treatments (3.1–4.8% of observations). The pigs in tethers had highest free corticosteroid levels “at rest” (2.2 ng ml −1 compared to an average of 1.4 ng ml −1 for the other treatments), a disrupted rhythm of corticosteroid levels and, at the second sampling period (9–12 weeks of pregnancy), a lower response to transport; these responses in the tethered pigs were associated with an increase in plasma glucose and a decrease in plasma urea levels. These physiological data indicate a chronic stress response and a significant metabolic cost resulting from housing pigs in tethers. The implications of the results to the welfare of pregnant pigs are discussed.

The effects of individual and group penning of pigs on total and free plasma corticosteroids and the maximum corticosteroid binding capacity.

Abstract Total and free plasma corticosteroid concentrations and the maximum corticosteroid binding capacity (MCBC) were measured twice a day in pigs penned individually or in groups following a period of individual penning. Moving animals into groups after 5 weeks in individual pens resulted in a short-term stress response as evidenced by an increased corticosteroid concentration measured 5 1 2 hr later, but within 24 hr the hormonal pattern established was of higher levels in the morning than in the afternoon. In group-penned pigs the total corticosteroid concentration was generally well below that of the MCBC. In contrast, in individually penned pigs the MCBC was lower and the afternoon corticosteroid concentration was elevated to levels similar to the morning values. Both morning and after-noon mean corticosteroid values approached the mean MCBC. It was concluded that individual penning resulted in a chronic stress response.

The welfare of adult pigs: the effects of five housing treatments on behaviour, plasma corticosteroids and injuries

Abstract The effects of 5 housing treatments (tethers, pairs, or a group indoors, in a yard or in a paddock) on the behaviour, physiology (stress physiology and blood metabolites), health (injury status) and production (food eaten and oestrous expression) of 30 non-pregnant adult female pigs were determined at regular intervals over 12 months. Pigs housed in pairs exhibited a chronic stress response; they had the highest free corticosteroid levels “at rest”, a disrupted diurnal rhythm of plasma corticosteroids and a slower corticosteroid response to, and recovery from, transport. Behaviourally, these pigs spent more time lying alone than pigs in other treatments, and there was a significant regression between lying alone behaviour and free corticosteroid levels, suggesting this behaviour may be a useful indicator of welfare status. The group of 6 pigs housed indoors consistently showed the lowest total and free corticosteroid levels during the entire experiment, and also the least lying alone behaviour; however, these responses may have been influenced by their similar rearing and experimental environment. While the occurrence of inappropriate behaviours such as champing, biting and excessive drinking was generally low, it was higher in pigs housed indoors, particularly the tether and pair treatments, suggesting mild frustation in these latter 2 treatments. A comparison of the two most contrasting environments (tethers and paddock treatments) showed no clear welfare advantage in housing non-pregnant adult pigs in a more extensive environment.

The effect of piglet stimuli on the posture changing behaviour of recently farrowed sows

Abstract Twenty-four primiparous sows that had recently farrowed in commercial farrowing crates were tested in a 2 × 2 factorial experiment for their behavioural response to piglet stimuli during the process of changing from a standing to a lying posture. The piglet stimuli presented were those that a sow may perceive prior to an overlay situation, where the sow crushes a piglet beneath her body. The experimental treatments were (1) tactile stimulus (model piglet under the sows udder); (2) auditory stimulus (piglet distress vocalizations). The application of either stimulus produced significant ( P χ 2 2 = 12.25, P

The effect of mating on plasma corticosteroids in the female pig and the influence of individual and group penning on this response

Corticosteroid levels in the plasma of female pigs in behavioural oestrus were elevated within 5 min of the completion of mating in an unfamiliar pen. These levels were 25% higher than those produced by exposure to an unfamiliar pen alone (mean free corticosteroid levels were 7.5 and 5.6 ng ml−1, respectively). In two further experiments conducted in different seasons and times of day, there was a similar response to the boar, but it was greater in animals which had previously been kept in pens in groups compared to those kept in individual pens. It was concluded that stressors produced by the social environment may influence the postmating release of corticosteroids in female pigs.

The incidence of, and factors associated with, failure to mate by 245 days of age in the gilt

The incidence of, and factors associated with, gilts failing to mate between 29 and 35 weeks of age were studied over 12 months at a large intensive piggery in southern Australia. After excluding gilts culled as physically unsound, 10.5% of the remaining 2484 gilts failed to mate and were slaughtered. n nSeventy percent of unmated gilts had ovulated, and of these, 54% had shown negative or low responses to the back-pressure test (BPT) and 16% had shown moderate or high responses. Few prepubertal gilts (1%) had abnormal reproductive tracts. n nWhen group size was greater than 50 gilts (< 0.9 m2/gilt) immediately prior to mating (27–28 weeks of age), there was a higher incidence of unmated gilts and an increase in the proportion of unmated gilts which had shown negative or low BPT response than when groups were less than 50 gilts (12.9 vs. 8.6%, P < 0.001; and 8.0 vs. 3.6%, P < 0.001, respectively). n nThe incidence of prepubertal gilts at 35 weeks was lower during spring than other seasons (1.48 and 3.36%, P < 0.05) and higher during summer than other seasons (4.61 and 2.37%, P < 0.01). n nFewer Large White gilts remained unmated at 35 weeks of age than Landrace or Large White-Landrace synthetic breed gilts (7.7 and 14.1% of those selected, P < 0.001). More purebred gilts were prepubertal at 35 weeks of age than crossbred gilts (5.4 and 2.4%, P < 0.01).

THE EFFECTS OF TWO OESTRUS DETECTION PROCEDURES AND INTENSE BOAR STIMULATION NEAR THE TIME OF OESTRUS ON MATING EFFICIENCY OF THE FEMALE PIG

Abstract In the first experiment, a higher oestrus detection rate (percentage of cycling gilts that were detected in oestrus) and a higher mating rate (percentage of cycling gilts that were mated) were achieved when cycling gilts were checked for oestrus in the corridor adjacent to the boar pens than when they were checked in their own pens, which were separated from the boar pens by a 1.0 m-wide corridor (90 v. 52% and 87 v. 52%, respectively). In the second experiment, several housing treatments were imposed over a 21-day period. A lower proportion of gilts were detected in the I stage of oestrus (positive response to the back-pressure test both in the presence and absence of a boar) and a lower mating rate was achieved when cycling gilts were separated from the boar by a wire-mesh pen division than when separated by a 1.0 m corridor (48 v. 81% and 47 v. 81%, respectively). It was concluded that cycling females should be housed near, but not adjacent to, boars and that at the time of oestrus detection using the back-pressure test, females should be very close to boars.

The Effects of Genotype on Physiological and Behavioural Responses Related to the Welfare of Pregnant Pigs

Abstract Plasma free-corticosteroid concentrations, aggressive behaviour and levels of motivation to socially interact and explore a novel arena were observed in an experiment to examine whether differences previously observed between pigs in neck-tethers and groups are shown by pigs of different genotypes. Thirty-two pregnant gilts of 2 genotypes were housed in either tether stalls or groups. The 2 genotypes were mainly Large White×Landrace stock, but one had been intensively selected on the basis of growth performance. Genotypic differences had previously been observed in protein and energy metabolism, and the present experiment also showed differences in their behaviour (increased activity and a decreased motivation to socially interact in the intensively selected genotype) and free-corticosteroid concentrations (40% lower in the intensively selected genotype). In spite of these differences, the behavioural and physiological responses to housing treatments were similar. In tether stalls, pigs of both genotypes had a higher frequency of retaliation and a lower frequency of withdrawal in response to aggressive interactions than group-housed pigs. There were 50 and 56% increases in free-corticosteroid concentrations in response to tether housing in the 2 genotypes, providing evidence of a chronic stress response of a magnitude sufficient to suggest a risk to welfare in the design of tether stall used in this experiment.

The effect of early contact with mature boars on reproductive efficiency in the gilt

The effect of first contact of gilts with a mature boar at 23 or 28 weeks of age on their subsequent reproductive efficiency was studied over a 12-month period at a large intensive piggery in southern Australia. Following this contact, the gilts entered the mating shed at 29 weeks of age and were checked daily for oestrus, as assessed by the back-pressure test in the presence of the boar. Gilts that showed moderate or high responses were taken to a boar for mating. Sexual receptivity was then assessed by the time taken to “stand” after the first mount by the boar. Gilts that remained unmated at 35 weeks of age were culled, and their ovaries were examined. n nOf the 2660 gilts in the study, 2349 were mated and they had a farrowing rate of 88.2% with a mean litter size of 9.5 piglets, of which 0.7 piglets (7.4%) were born dead. The reproductive efficiency of the gilts following earlier contact with the boar was consistently higher than that of gilts exposed later. The mating rate of the week 23 gilts was greater than that of the week 28 gilts (70.1 vs 66.0%, P < 0.01), more appeared to show a high level of sexual receptivity (97.0 and 94.6%, N.S.) and fewer failed to mate when put to a boar (6.1 vs 9.5%, P < 0.01). The percentage of prepubertal gilts at 35 weeks of age was also lower (1.46 vs 3.03%, P < 0.01). The improved reproductive performance was estimated to be equivalent to 0.24 extra piglets born per gilt.

Oestrous behaviour in relation to fertility and fecundity of gilts

The reproductive performance of 2484 gilts was recorded over a 12-month period at a large intensive piggery in southern Australia. Between 29 and 35 weeks of age, gilts were examined daily for response to the back-pressure test (BPT). Those subjectively assessed as showing a moderate or high response were taken to a boar for mating. Gilts that had showed a moderate response to the BPT on their first day of mating had lower average litter size than gilts showing a high BPT response (9.05 and 9.35 piglets, respectively; P < 0.05). A quantitative assessment of sexual receptivity was made while the gilt was with the boar. Gilts that were mated while showing low sexual receptivity on the first day of mating had poorer farrowing rate (78.1 vs. 83.1%, respectively; P < 0.05), as well as lower litter size (9.03 vs. 9.35 piglets, respectively; P < 0.05) than gilts that were mated when showing high sexual receptivity. A moderate BPT response was followed by either low sexual receptivity or failure to mate on 81.4% of occasions, compared with 12.8% for a high BPT response. Since 75% of gilts that showed a moderate BPT response on the first day of mating showed a high response on the following day, it was concluded that mating should only be attempted when gilts exhibit a high response to the BPT. The mean farrowing rate and litter size for gilts at their first farrowing was 82.4% and 9.31 piglets (8.62 alive and 0.69 dead), respectively.