Behavior In Female Pigs Research Articles

Effects of Field Pea Diet and Immunocastration in Heavy Pigs on Fresh Pork and Dry-Cured Ham

Peas are an alternative to soybeans to supply protein in livestock feeds. Immunocastration avoids surgical castration of male pigs and increases fat deposition in female pigs. This work aimed to assess the effects of pea inclusion on the amount of fat and fatty acid profile of loins and on weight losses of dry-cured hams in different sexes of pigs; in addition, growth performance and feeding behavior in immunocastrated female pigs were evaluated. Two experiments were conducted with crossbred immunocastrated female (IF) and immunocastrated (IM) or surgically castrated (CM) male pigs from Duroc dams sired by Berkshire, which were assigned to one of two diets (soybean vs. pea-based). The effect of castration type on the afore-mentioned variables was evaluated in male pigs, and the growth performance, and feeding behavior in female pigs. The pea-based diet in IF had no effect on average daily gain nor on carcass traits; although, it increased feeding time (p < 0.001) and reduced n-3 polyunsaturated fatty acid (PUFA) content (p < 0.05). In male pigs, the pea-based diet did not change carcass fatness either but reduced the n-3 PUFA levels (p < 0.05). Likewise, IM had lower (p < 0.001) monounsaturated fatty acid (MUFA) and higher (p < 0.05) n-6 PUFA than CM. Diet did not affect dry-cured ham weight losses during the process, while IM showed greater (p < 0.001) losses than CM. Pigs fed a pea-based diet complied with the requirements of cured ham production, while immunocastration in male pigs increased weight losses, partly explained by lower fat content and higher fatty acid unsaturation.

Sexual behaviour in female pigs

This paper reviews the influence of social mechanisms on oestrus and sexual motivation in pigs. The social relations between the animals and the signals they send out can inhibit as well as encourage their social motivation. Social stimuli from both boars and other sows in oestrus tend to induce and synchronise oestrus and ovulation amongst sows. The courting behaviour of boars is also facilitated by social stimuli from other boars. However, when sows are kept under conditions where the social pressure is high, e.g. due to limited space and/or resources, the social stress experienced by particularly the subordinate individuals may inhibit sexual motivation during oestrus. To a large extent this effect seems to be mediated via specific fear reactions towards dominant individuals of sows that have lost many aggressive encounters. For example, fear reduces the sexual motivation during mating and during sexual interactions amongst sows within a group, and fear may thus inhibit their chances of reproductive success. Similarly, fear of humans caused by innate fearfulness or negative handling procedures reduces sexual motivation in the presence of the human handler even when sows are in standing oestrus.

The effect of small doses of naloxone on the initiation and duration of the first estrus after weaning in sows

The present research was conducted with the objective of studying the pharmacological effect of small doses of naloxone on the initiation and duration of the first estrus after weaning in the sow. For this purpose, 32 multiparous sows were used. Sows were divided at random into two groups. Group 1 ( n=16) was treated by i.m. injection with 2 mg naloxone at 12 h intervals from 3 days before until 3 days after weaning. Group 2 ( n=16) served as the control group and received saline solution at the same times as treatments for group 1. First estrus after weaning occurred at 85±5.2 and 108.3±5 h ( P<0.05) in naloxone- and saline-treated sows. Duration of estrus was 89.6±3.9 and 49.6±3.9 h ( P<0.05) in naloxone-treated and control animals, respectively. It was concluded that naloxone treatment advanced the time of appearance and duration of the first estrus after weaning in sows giving further support that endogenous opioids (EOP) are modulators of sexual behavior in female pigs.

C-fos mRNA expression associated with PGF 2α-induced nest-building behaviour in female pigs

Domestic pigs, Sus scrofa, build a maternal nest on the day before parturition. A model for nest building has been established in pigs, in which exogenously administered prostaglandin (PG) F 2α may be used to elicit nesting behaviour in cyclic, pseudopregnant and pregnant pigs. The central mechanisms mediating this response are unknown. The present study determined regional brain activity using semi-quantitative analysis of c-fos mRNA, after induction of nest-building behaviour by PGF 2α in Large White pseudopregnant pigs. Oestradiol valerate injections (5 mg/day) were given on days 11–15 of the oestrous cycle to induce pseudopregnancy. The pigs were housed individually in pens (2.8×1.7 m) containing straw. On the test day (day 46 or 47 of pseudopregnancy) animals were injected with 3 ml saline ( n=5) or 15 mg of PGF 2α (Lutalyse, Upjohn; n=6) intramuscularly. Pigs treated with PGF 2α, but not saline, displayed bouts of rooting, pawing and gathering straw, which we interpret as nest building behaviour. The pigs were killed 65 min after treatment, which was 30 min after peak nest building activity, and the brain, uterus and ovaries removed for processing using in situ hybridisation. Saline-treated pigs had elevated levels of c-fos mRNA, compared to background, in the pituitary, corpus luteum and uterus, and a lower, but elevated, level of expression in cerebellum, cortex, hippocampus and olfactory bulb. PGF 2α-treated pigs had significantly higher levels of c-fos mRNA expression than saline-treated pigs in the parvocellular and magnocellular regions of the hypothalamic paraventricular nucleus, the supraoptic nucleus (including the pars dorso-medialis), the neural lobe of the pituitary gland and the cerebellum. PGF 2α-treated pigs also had significantly higher c-fos induction in corpus luteum. These data show that the pattern of c-fos mRNA expression in specific brain areas is different between pigs that show PGF 2α-induced nest building and saline-injected controls.

Behavioral Responses to Intramuscular Injections of Prostaglandin F 2α in Female Pigs

This study investigated the effect of different doses (0–1.25 mg/kg IM) of prostaglandin (PG) F 2α on the behavior of female pigs ( Sus scrofa). Six-month-old cyclic nulliparous sows (gilts) were housed and tested individually in strawed pens (2.8 × 1.7 m). All doses of PGF 2α induced rooting, pawing at the ground, and gathering straw. In the hour following treatment the frequency of pawing increased with increasing dose to reach a maximum level with the highest dose given. The frequency to gather straw was highest in pigs treated with the lowest dose (0.008 mg/kg). The frequency of oronasal contact with the floor and pen walls was unaffected by dose. Scratching, locomotion, and changes in body posture were highest following treatment with the three highest doses of PGF 2α. Many of the behaviors observed following PGF 2α treatment are characteristic of prepartum nesting behavior in pregnant sows. We conclude that two key components of maternal nest-building behavior, pawing, and gathering straw, are affected differentially by different doses of PGF 2α. The implications of these results on the mechanisms underlying maternal nest building in pigs are discussed.

Deprivation of straw bedding alters PGF 2α-induced nesting behaviour in female pigs

Sows are highly motivated to build a maternal nest on the day preceding parturition. A model for nest building has been established in pigs, in which exogenously administered prostaglandin F 2α (PGF 2α) may be used to elicit nesting behaviour in cyclic, pseudopregnant and pregnant pigs. The aim of this experiment was to examine the effects of deprivation of straw bedding on PGF 2α-induced nest building in pseudopregnant Large White gilts. Oestradiol valerate injections (5 mg/day) were given on days 11–15 of the oestrous cycle to induce pseudopregnancy. The pigs were housed individually in a pen (2.8×1.7 m) and provided with 2-kg fresh straw each day. On the test day, on day 46 or 47 of pseudopregnancy, half of the pigs were deprived of straw (substrate effect) and they were injected intramuscularly with saline or 15 mg of PGF 2α (Lutalyse, Upjohn) (treatment effect) allocated in a Latin-square design. Behaviour was recorded onto video tapes for 1 h either side of treatment for analysis using a computerised event recorder. PGF 2α-treated pigs housed in bare or strawed pens showed significantly higher frequencies of pawing and rooting, and stood for longer than saline-treated controls. This treatment effect has been previously shown to be comparable to pre-partum nest building. The removal of straw significantly reduced the frequency of pawing and the duration of rooting by PGF 2α-treated pigs. The results demonstrate that nesting behaviour can be initiated by exogenously administered PGF 2α and is further modified by the provision of straw. This suggests that PGF 2α-induced nesting behaviour is subject to environmental feedback.

Sensitivity and Behavioral Responses to the Pheromone Androstenone Are Not Mediated by the Vomeronasal Organ in Domestic Pigs

Based largely on results of studies of laboratory rodents, the vomeronasal or accessory olfactory system is believed to function mainly in social communication, mediating the effects of stimuli such as urine or glandular secretions on the behavior or endocrine response of conspecifics. In the domestic pig (Sus scrofa), the steroid androstenone has been identified as a pheromone that facilitates expression of both attraction to the male and a receptive mating stance in estrous females. Though the domestic pig is one of the few vertebrate species in which the identity of a compound that functions as a pheromone is known, the role of the vomeronasal system in domestic pigs has never been investigated. We have examined the role of the vomeronasal organ in mediating the pheromonal effects of androstenone in pigs. In addition, we have examined the structure of the vomeronasal organ at the gross and light-microscopic levels. The vomeronasal organ appears functional, with sensory epithelium lining the medial wall, and has access to stimuli from both the oral and nasal cavities. To determine whether the vomeronasal organ is necessary for androstenone detection or attraction or receptive behavior in female pigs, access to the vomeronasal organ was blocked with surgical cement, and androstenone detection threshold and sexual behavior were measured. Experimental animals did not differ significantly in androstenone sensitivity, measured behaviorally, from untreated controls. Vomeronasal organ-blocked animals also did not differ from untreated controls in either androstenone-mediated receptive standing behavior or attraction to the odor of androstenone. We conclude that in the domestic pig, the vomeronasal organ is not necessary for androstenone detection or androstenone-mediated sexual behavior in estrous females.