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The social environment and reproduction of the female pig
579 The stress-induced changes in the function of the endocrine system very often result in unsatisfactory reproductive performance. Preliminary results of dealing with previous reproductive disorders in intensive piggeries are reported.
PHYSIOLOGICAL AND BEHAVIOURAL STRESS AND WELFARE IN THE PIG
ASPECTS
OF ASSESSING
J.L. BARNETT Animal Research Institute,
Werribee, Vie., 3030
(Australia)
ABSTRACT Background information is given on adrenal function in pigs and the implications this has for the design of experiments to examine acute stressors and to obtain a representative measure of plasma corticosteroids. Two experiments using corticosteroids to measure stress responses in pigs are described. First, individual and group penning of pigs is compared. Moving pigs to a new environment results in an acute stress response which is more severe when social interactions are involved. The effects of the penning treatment resulted in a chronic stress response in individually penned (no visual or tactile contact) pigs; the a.m.-p.m. rhythm of corticosteroids was abolished, afternoon values were higher (P < O.Ol), and mean corticosteroid binding capacity was lower (P < O.Ol), with a consequent elevation (P < 0.05) of free (biologically active) corticosteroids. In the second experiment, the effects of man-animal interactions were examined in growing pigs. Two treatments were imposed from 8 to 24 weeks of age, which resulted in either an avoidance or approach behaviour by the pigs to humans. In the group that showed avoidance, a 2-min exposure to humans resulted in an acute stress response (P < 0.05) with a I-fold increase in hormone levels, that returned to pre-exposure levels within 30 min. In the absence of humans, this group also had elevated (P < 0.005) corticosteroid levels throughout the day. One consequence of this chronic stress response was a significant reduction in growth rate (P < 0.05) and a lower food conversion rate.
THE SOCIAL ENVIRONMENT FEMALE PIG
AND REPRODUCTION
OF THE
P.H. HEMSWORTH Animal Research Institute,
Werribee,
Vie., 3030 (Australia)
ABSTRACT The objective of this paper is to discuss briefly two recent studies that demonstrate the important role of the social environment on reproduction of the gilt and sow. The influence of the social environment during rearing was studied by rearing four
580 groups of ten gilts from an early age under four social conditions. Over all mating tests conducted at the spontaneous and subsequent hormone-induced oestruses, the mating rate (defined as the proportion of the number of successful copulations to the number of oestruses) of gilt reared near mature boars (Treatments 3 and 4) was significantly higher (P < 0.05) than that of gilts reared in isolation from boars (Treatments 1 and 2). For gilts reared near mature boars, those that received regular boar introduction during rearing (Treatment 4) had a significantly higher (P < 0.05) mating rate. Gilts isolated from boars during rearing (Treatments 1 and 2) also had a significantly longer (P < 0.05) interval from first mount by the boar until the display of the standing response, and a significantly higher (P < 0.01) proportion of these gilts terminated the copulation in comparison to those reared near mature boars. It is concluded that the social environment during rearing influences the oestrous behaviour of the gilt. The second study was conducted at commercial farms ona total of 590 sows to investigate the role of the social environment on anoestrus in the weaned sow. Group housing and intense boar stimulation, achieved by daily introduction to a boar, were associated with significant reductions (P < 0.05 and P < 0.01, respectively) in the weaning-to-mating interval: these two treatments together produced a 38% increase in the percentage of fit-litter sows mated within 10 days of weaning. Over all sows this increase was 18%. Thus, the social environment from weaning to mating exerts a significant influence on the onset of oestrus in the sow.
MATING BEHAVIOUR AND SEMEN CHARACTERISTICS BOARS USED AT DIFFERENT MATING LOADS
C.G. WINFIELD
OF YOUNG
and P.H. HEMSWORTH
Animal Research Institute,
Werribee, Vie., 3030
(Australia)
ABSTRACT To examine the effect of a high mating load in young breeding boars (5.5-10 months of age), one of three treatments was imposed on groups of 4 boars: Tl, six matings/week on 3 consecutive days; T2, no mating but housed near female pigs; T3, no mating, housed away from female pigs. During the treatment period, Tl boars maintained the desired mating frequency with no difficulties and sperm numbers were acceptable (about 0.5 x 10” sperm/ejaculate), but sperm motility was low. During the post-treatment period from 10 to 12.5 months of age, when all boars were mated twice per week, there were no significant differences between treatment groups in mating behaviour test scores or semen characteristics. In a further post-treatment evaluation period from 14.5 to 16 months of age, where a higher mating load was imposed, Tl boars achieved significantly more copulations per mating test than T2 or T3 boars (2.20, 1.86 and 1.04 copulations each/test, respectively, P < 0.05). There appears to be no subsequent detrimental effect of a high mating load on young boars, but semen quality under a high load is uncertain.
PHYSIOLOGICAL AND BEHAVIOURAL STRESS AND WELFARE IN THE PIG
ASPECTS
OF ASSESSING
J.L. BARNETT Animal Research Institute,
Werribee, Vie., 3030
(Australia)
ABSTRACT Background information is given on adrenal function in pigs and the implications this has for the design of experiments to examine acute stressors and to obtain a representative measure of plasma corticosteroids. Two experiments using corticosteroids to measure stress responses in pigs are described. First, individual and group penning of pigs is compared. Moving pigs to a new environment results in an acute stress response which is more severe when social interactions are involved. The effects of the penning treatment resulted in a chronic stress response in individually penned (no visual or tactile contact) pigs; the a.m.-p.m. rhythm of corticosteroids was abolished, afternoon values were higher (P < O.Ol), and mean corticosteroid binding capacity was lower (P < O.Ol), with a consequent elevation (P < 0.05) of free (biologically active) corticosteroids. In the second experiment, the effects of man-animal interactions were examined in growing pigs. Two treatments were imposed from 8 to 24 weeks of age, which resulted in either an avoidance or approach behaviour by the pigs to humans. In the group that showed avoidance, a 2-min exposure to humans resulted in an acute stress response (P < 0.05) with a I-fold increase in hormone levels, that returned to pre-exposure levels within 30 min. In the absence of humans, this group also had elevated (P < 0.005) corticosteroid levels throughout the day. One consequence of this chronic stress response was a significant reduction in growth rate (P < 0.05) and a lower food conversion rate.
THE SOCIAL ENVIRONMENT FEMALE PIG
AND REPRODUCTION
OF THE
P.H. HEMSWORTH Animal Research Institute,
Werribee,
Vie., 3030 (Australia)
ABSTRACT The objective of this paper is to discuss briefly two recent studies that demonstrate the important role of the social environment on reproduction of the gilt and sow. The influence of the social environment during rearing was studied by rearing four
580 groups of ten gilts from an early age under four social conditions. Over all mating tests conducted at the spontaneous and subsequent hormone-induced oestruses, the mating rate (defined as the proportion of the number of successful copulations to the number of oestruses) of gilt reared near mature boars (Treatments 3 and 4) was significantly higher (P < 0.05) than that of gilts reared in isolation from boars (Treatments 1 and 2). For gilts reared near mature boars, those that received regular boar introduction during rearing (Treatment 4) had a significantly higher (P < 0.05) mating rate. Gilts isolated from boars during rearing (Treatments 1 and 2) also had a significantly longer (P < 0.05) interval from first mount by the boar until the display of the standing response, and a significantly higher (P < 0.01) proportion of these gilts terminated the copulation in comparison to those reared near mature boars. It is concluded that the social environment during rearing influences the oestrous behaviour of the gilt. The second study was conducted at commercial farms ona total of 590 sows to investigate the role of the social environment on anoestrus in the weaned sow. Group housing and intense boar stimulation, achieved by daily introduction to a boar, were associated with significant reductions (P < 0.05 and P < 0.01, respectively) in the weaning-to-mating interval: these two treatments together produced a 38% increase in the percentage of fit-litter sows mated within 10 days of weaning. Over all sows this increase was 18%. Thus, the social environment from weaning to mating exerts a significant influence on the onset of oestrus in the sow.
MATING BEHAVIOUR AND SEMEN CHARACTERISTICS BOARS USED AT DIFFERENT MATING LOADS
C.G. WINFIELD
OF YOUNG
and P.H. HEMSWORTH
Animal Research Institute,
Werribee, Vie., 3030
(Australia)
ABSTRACT To examine the effect of a high mating load in young breeding boars (5.5-10 months of age), one of three treatments was imposed on groups of 4 boars: Tl, six matings/week on 3 consecutive days; T2, no mating but housed near female pigs; T3, no mating, housed away from female pigs. During the treatment period, Tl boars maintained the desired mating frequency with no difficulties and sperm numbers were acceptable (about 0.5 x 10” sperm/ejaculate), but sperm motility was low. During the post-treatment period from 10 to 12.5 months of age, when all boars were mated twice per week, there were no significant differences between treatment groups in mating behaviour test scores or semen characteristics. In a further post-treatment evaluation period from 14.5 to 16 months of age, where a higher mating load was imposed, Tl boars achieved significantly more copulations per mating test than T2 or T3 boars (2.20, 1.86 and 1.04 copulations each/test, respectively, P < 0.05). There appears to be no subsequent detrimental effect of a high mating load on young boars, but semen quality under a high load is uncertain.