Salivary Cortisol in Guide Dogs.

Guide dogs work for extended periods and are exposed to multiple environmental stimuli that could lead to higher stress compared with companion dogs. Cortisol is the main hormone associated with stress in most mammals. This study included seven guide dogs and seven same-breed dogs that were trained as guide dogs but became companion dogs to compare their salivary cortisol levels before, during, and after a period of social isolation and exposure to a 110-decibel gunshot sound. Each dog was left alone in an empty room for 60 min. After 15 min, the dogs were exposed to the sound. We collected four saliva samples from each dog. The first one was taken 5 min before starting the social isolation period, and the following ones at 15, 30, and 45 min after the test started. A two-way ANOVA was used to compare the group effect and the time effect during isolation and noise exposure. The results showed higher levels of cortisol in the guide dogs compared with the companion dogs throughout the test. No differences were found in time or in the interaction between time and group. This suggests that being a guide dog increases levels of basal cortisol when compared with dogs that live as companion animals and family members.

Neurobiology of Maternal Behavior in Nonhuman Mammals: Acceptance, Recognition, Motivation, and Rejection.

Among the different species of mammals, the expression of maternal behavior varies considerably, although the end points of nurturance and protection are the same. Females may display passive or active responses of acceptance, recognition, rejection/fear, or motivation to care for the offspring. Each type of response may indicate different levels of neural activation. Different natural stimuli can trigger the expression of maternal and paternal behavior in both pregnant or virgin females and males, such as hormone priming during pregnancy, vagino-cervical stimulation during parturition, mating, exposure to pups, previous experience, or environmental enrichment. Herein, we discuss how the olfactory pathways and the interconnections of the medial preoptic area (mPOA) with structures such as nucleus accumbens, ventral tegmental area, amygdala, and bed nucleus of stria terminalis mediate maternal behavior. We also discuss how the triggering stimuli activate oxytocin, vasopressin, dopamine, galanin, and opioids in neurocircuitries that mediate acceptance, recognition, maternal motivation, and rejection/fear.

Clicker Training Accelerates Learning of Complex Behaviors but Reduces Discriminative Abilities of Yucatan Miniature Pigs.

Animal training is meant to teach specific behavioral responses to specific cues. Clicker training (CT) is a popular training method based on the use of a device that emits a sound of double-click to be associated as a first-order conditioned stimulus in contingency with positive reinforcements. After some repetitions, the clicker sound gains some incentive value and can be paired with the desired behavior. Animal trainers believed that CT can decrease training time compared to other types of training. Herein, we used two-month old miniature piglets to evaluate whether CT decreased the number of repetitions required to learn complex behaviors as compared with animals trained with voice instead of the clicker. In addition, we compared the number of correct choices of animals from both groups when exposed to object discriminative tests. Results indicated that CT decreased the number of repetitions required for pigs to learn to fetch an object but reduced the ability of animals to make correct choices during the discriminate trials. This suggests that CT is more efficient than voice to teach complex behaviors but reduces the ability of animals to use cognitive processes required to discriminate and select objects associated with reward.

Effect of stress during slaughter on carcass characteristics and meat quality in tropical beef cattle.

OBJECTIVE: This study aimed to determine the effects of stress during slaughter of beef cattle on physiological parameters, carcass, and meat quality at a Federal Inspection Type slaughterhouse located in the southeast of Mexico. METHODS: A total of 448 carcasses of male Zebu×European steers with an average age of 36 months were included. Carcass assessment of presence of bruises and bruise characteristics was carried out on each half-carcass. Blood variable indicators of stress (packed cell volume, neutrophil to lymphocyte ratio, glucose, cortisol concentration) and meat quality parameters (pH, color, shear force, drip loss) were evaluated. RESULTS: Of the 448 carcasses evaluated, 81% of the carcasses showed at least one bruise; one bruise was detected in 36.6% and two bruises in 27.0% of animals. Of the 775 bruises found, 69.2% of the bruises were grade 1 in region 3. Of the 448 carcasses studied, 69.6% showed hyperglycemia (6.91 mmol/L); 44.3% and 22.7% showed high (74.7 ng/mL) and extremely high (108.8 ng/mL) cortisol levels, respectively, indicative of inadequate handling of animals during preslaughter and slaughter. Of the carcasses evaluated, 90.4% had a pH ≥5.8 with an average of pH 6.3. In both pH groups, meat samples showed L* values >37.0 (81.6%) and a shear force >54.3 N; meat pH≥5.8 group showed a drip loss of 2.5%. These findings were indicative of dark, firm, and dry (DFD) meat. According to principal component analysis, grades 1 and 2 bruises in region 3 and grade 1 bruises in region 5 were highly associated with cortisol, drip loss, and color parameters b* and h* and were negatively associated with L*, a*, and C*. CONCLUSION: The bruises probably caused by stress-inducing situations triggered DFD meat. Appropriate changes in handling routines in operating conditions should be made to minimize stress to animals during the slaughter process to improve animal welfare and meat quality.

Heterosexual experience prevents the development of conditioned same-sex partner preference in male rats.

Sexual partner preferences can be strengthened, weakened or even drastically modified via Pavlovian conditioning. For example, conditioned same-sex partner preference develops in sexually-naïve male rats that undergo same-sex cohabitation under the effects of quinpirole (QNP, D2 agonist). Here, we assessed the effect of prior heterosexual experience on the probability to develop a conditioned same-sex preference. Naïve or Sexually-experienced males received either Saline or QNP and cohabited during 24h with a male partner that bore almond scent on the back as conditioned stimulus. This was repeated every 4days for a total of three trials and resulted in four groups (Saline-naïve, Saline-experienced, QNP-naïve, QNP-experienced). Social and sexual preference were assessed four days after the last conditioning trial in a drug-free test in which experimental males chose between the scented familiar male and a novel sexually receptive female. Results showed that Saline-naïve, Saline-experienced and QNP-experienced displayed a clear preference for the female (opposite-sex). By contrast, only QNP-naïve males displayed a same-sex preference. Accordingly, QNP-experienced males were not affected by the conditioning process and continued to prefer females. We discuss the effects of copulation and D2 agonists on the facilitation and/or disruption of conditioned partner preferences.

Status epilepticus during early development disrupts sexual behavior in adult female rats: recovery with sexual experience.

Female sexual behavior is sensitive to stress and diseases. Some studies have shown that status epilepticus (SE) can affect sexual proceptivity and receptivity in female rats and also increases reject responses towards males. However, epidemiologic studies indicate that SE is more frequent in young individuals. Herein, we assessed the effects of SE in infant females on their sexual behavior during adulthood. Thirteen-day-old (P13) rat pups received intraperitoneal injections of lithium chloride (3 mEq/kg). Twenty hours later, at P14, SE was induced by subcutaneous injection of pilocarpine hydrochloride (100 mg/kg s.c.). Control animals were given an equal volume of saline subcutaneously. The animals were weaned at P21 and, later in adulthood, were ovariectomized and hormone-primed with estradiol+progesterone, and their sexual behavior assessed during 4 separate trials of 30 min each with a stud male. Our results indicate that proceptive behaviors (solicitations and hops and darts) were impaired during the first trial, but no alterations were observed for receptivity and attractivity. By trial 3, all SE females displayed normal proceptivity. These results indicate that SE in infancy readily affects proceptivity in a reversible manner. We discuss the role of sexual experience in recovery.

Tickling in juvenile but not adult female rats conditions sexual partner preference.

Female rats display a conditioned partner preference for males that bear odors paired with different types of rewarding unconditioned stimuli (UCS). Here we examined whether tickling constitutes a rewarding UCS that supports the development of partner preferences. In Experiment 1, we tested the possibility that odors associated with a tickling UCS in prepubescent rats would induce a conditioned partner preference in adulthood. Two groups were formed with 31-day-old, single-housed females, tickled for 6 min daily for 10 days, by a hand that wore a scented glove (almond or lemon). At 47 days of age, females were ovariectomized (OVX), hormone-primed (EB+P), and tested for sexual partner preference with two scented stud males (one almond and one lemon). In each group, females displayed a sexual preference toward males bearing the odor paired with tickling, as observed with longer visits, more solicitations, hops & darts, and receiving more intromissions and ejaculations from the preferred male. In Experiment 2, we used 3-month old, OVX, hormone-primed rats conditioned every 4 days for 10 trials. In contrast to juvenile females, adult females failed to prefer males that bore the odor paired with tickling but instead preferred the novel male. These results suggest that tickling has opposite age-dependent effects in the conditioning of partner preference. Tickling in juvenile females appears to act as a rewarding UCS, whereas in adult females it may act as an aversive UCS. Further research is needed to understand brain mechanisms that might account for such differences.

Juvenile play conditions sexual partner preference in adult female rats.

Rats can display a conditioned partner preference for individuals that bear an odor previously associated with sexual reward. Herein we tested the possibility that odors associated with the reward induced by social play in prepubescent rats would induce a conditioned partner preference in adulthood. Two groups of 31-day-old, single-housed female rats were formed, and were given daily 30-min periods of social play with scented females. In one group, almond scent was paired with juvenile play during conditioning trials, whereas lemon scent functioned as a novel odor in the final test. The counterbalanced group received the opposite association. At age 42, females were tested for play partner preference with two males, one almond-scented and one lemon-scented. In both groups females displayed a play partner preference only for males scented with the paired odor. They were ovariectomized, hormone-primed, and at age 55 were tested for sexual partner preference with two scented stud males. Females displayed a sexual preference towards males scented with the paired odor as observed with more visits, solicitations, hops and darts, intromissions and ejaculations. These results indicate that olfactory stimuli paired with juvenile play affects later partner choice for play as well as for sex in female rats.

Sexual reward induces Fos in the cerebellum of female rats.

The cerebellum is generally considered a neural structure specialized in motor control and recent imaging data suggest its role in sexual behavior. Herein, we analyzed the pattern of Fos immunoreactivity (Fos-IR) in the cerebellum of female rats allowed to pace copulation as a model of sexual reward in rodents. Ovariectomized, hormone-primed, sexually naïve females formed three groups: Pacing, Nonpacing and Control. Pacing occurred in arenas bisected by a middle divider that allowed only females to control sexual interaction with stud males. For nonpaced copulation the divider was removed, and control females were allowed to pace in chambers without a male. Fos-IR was analyzed in granule and Purkinje layers of the 10 cerebellar lobules, and in the fastigial deep nucleus (FDN). Results indicated that Pacing females expressed more Fos-IR in the granule layer compared to Nonpacing and Controls, and more Fos-IR in Purkinje compared to Nonpacing. No differences were observed in FDN. Such response cannot be explained with motor activity because Pacing females moved less in general. We discuss the role of the cerebellum and its connections in the sexual reward induced by pacing.