Changes in the activity of the sympathetic nervous system or in the hypothalamo-pituitary-adrenal axis have been extensively used to evaluate pain induced by castration or tail docking in numerous species. Such data are missing in pigs. Therefore, three experiments were conducted to determine the effects of castration, tail docking, or tooth resection on stress hormones. Glucose and lactate also were measured because catecholamines stimulate mobilization of glycogen, which results in glucose and lactate release. In Exp.1, 18 male pigs from seven litters (two or three pigs per litter) were catheterized surgically into one jugular vein, under general anesthesia, at 5 or 6 d of age. Two days later, they were submitted either to bilateral castration, control handling, or no handling (n = 6 per group). Blood samples were collected before (- 15 and -2 min) and after (5, 15, 30, 60, 90, 180 min) the experimental treatment. In Exp. 2, 27 female pigs from 12 litters (one to four pigs per litter) were submitted either to tooth clipping with pliers, tooth resection with a grinder apparatus, control handling, or no handling (n = 6 or 7 per group) at 1 d of age. In Exp. 3, 17 female pigs from nine litters (one to three pigs per litter) were submitted to one of the following treatments: 1) tail docking with an electric-heated scissor docking iron, 2) control handling, and 3) no handling (n = 5 or 6 per group) at 1 d of age. Castration induced significant (P < 0.05) increases in adrenocorticotropin hormone (ACTH; from 5 to 60 min), cortisol (from 15 to 90 min), and lactate (from 5 to 30 min). These variations are indicative of stress and tissue damage following castration. In contrast, neither tail docking nor tooth resection had marked effects on plasma cortisol, ACTH, glucose, and lactate. Measurements of plasma cortisol, lactate, and ACTH could be useful for validating treatments designed to relieve the distress reaction induced by castration in pigs.

No abstract

Effects of nutritional deficit during lactation on secretion of gonadotropic hormones and ovarian follicular populations around weaning were investigated in 24 primiparous crossbred sows. Sows were allocated to receive close to ad libitum intakes (H) or approximately 50% of this amount (L) during a 28-d lactation. Serial blood samples were collected 1 d before weaning (W-1), in the hours following weaning (W), and 1 d after (W+1). Their ovaries were removed on the day of weaning or 2 d later (W+2) and subjected to macroscopic and histological observations. Mean and basal LH concentrations were not influenced by the level of feeding. Frequency of LH pulses was reduced in L sows (.17, .5, and .5 vs 1.50, 1.17, and .83 pulses/6 h at d W-1, W, and W+1 respectively; P < .05). Mean and basal concentrations of LH were influenced by the day of sampling, being significantly increased within hours following weaning. Mean FSH concentrations were influenced neither by the level of feeding nor by the day of sampling. At weaning, the ovaries from L sows were lighter and had smaller follicles and fewer follicles > or = 4 mm (P < .05). Values of these macroscopic characteristics increased after weaning ( P < .05). At weaning, the percentage of healthy follicles was higher in the first class (< 1 mm) and lower in the second class (1 to 2.99 mm) in L compared to H sows (P < .05). Whatever the day of sampling, IGF-I concentrations in follicular fluid tended to be lower in L than in H sows. These results indicate that feed restriction during lactation inhibits LH pulsatility and ovarian activity.

No abstract

The effects of dietary levels of tryptophan (TRP) and protein on voluntary feed intake, growth performance, muscle pH, and brain indoleamine and catecholamine concentrations were studied in an experiment involving 48 crossbred Piétrain x Large White pigs (38 kg initial weight). Equal numbers of females, intact males, and barrows were used and they were given ad libitum access to feed during the 28-d experiment. Four dietary treatments were compared in a 2 x 2 factorial arrangement, with the following levels of analyzed TRP and CP: 1) .12 and .16% TRP, suboptimum and optimum for growth, respectively, 2) 12.7% CP of a diet based on corn-soybean meal and adequately balanced for limiting essential amino acids other than TRP; and 16.7% CP diet with additional protein from corn gluten meal. Dietary CP interacted with TRP on feed intake and growth, with a greater depressive effect at .12% TRP than at .16% TRP in the three genders. Norepinephrine concentration, which was the highest in the preoptic area, was higher in females than in intact or castrated males. Serotonin concentration was increased by TRP supplementation in the different brain regions. Additional CP depressed serotonin concentration more at .12% TRP than at .16% TRP. The greater sensitivity of feed intake and growth of pigs, especially females, to TRP deficiency in the presence of additional CP may have been related to a more critical serotonergic activity, when hypothalamic serotonin concentration fell below a threshold level. Supplemental TRP increased muscle pH, both at 45 min and 24 h after death, in ham (adductor femoris and semimembranosus) and loin (longissimus), suggesting a sedative effect of TRP for reducing stress response.