Postnatal function of the somatotrophic axis in pigs born naturally or by Caesarian section

This study was designed to determine what effects the birth process would have on development of the somatotrophic axis in neonatal pigs. Eight crossbred sows were selected (n = 4 natural birth and n = 4 Caesarian section) for the present study. Blood and tissue samples from 38 pigs were collected at birth. Twenty pigs were maintained with natural birth sows until sacrificed for blood and tissue collection at 2 wk of age. Gestational age at birth did not differ (P > 0.16) between natural birth and C-section pigs. Average daily gain (ADG) from birth until 2 wk of age was reduced (P < 0.0001) by 39.3% in the C-section pigs as compared to the natural birth pigs. Serum growth hormone (GH) did not differ (P > 0.86) at birth, but was greater (P < 0.024) at 2 wk in C-section pigs. Serum insulin-like growth factor 1 (IGF-1) was greater at birth (P < 0. 0025) and at 2 wk of age (P < 0.035) in the natural birth pigs. Serum concentration of IGF-2 did not differ at birth (P > 0.8) but was greater (P < 0.043) in natural birth pigs at 2 wk of age. Pituitary content of GH mRNA and GH-releasing hormone receptor mRNA did not differ (P > 0.90) between groups regardless of age; however, expression of both mRNAs declined (P < 0.0003) from birth until 2 wk of age. There tended to be a birth type X age interaction (P < 0. 082) for liver IGF-1 mRNA such that C-section pigs had a greater expression at 2 wk of age. Liver IGF-1 mRNA expression increased (P < 0.0001) in both groups from birth to 2 wk of age. Liver expression of GH receptor mRNA was greater in C-section pigs at birth (P < 0. 04) and 2 wk of age (P < 0.03). These data provide evidence that the natural birth process affects postnatal development and/or function of the somatotrophic axis in the neonatal pig.     

In utero heat stress alters the postnatal innate immune response of pigs

The effects of in utero heat stress (IUHS) range from decreased growth performance to altered behavior, but the long-term impact of IUHS on postnatal innate immune function in pigs is unknown. Therefore, the study objective was to determine the effects of early gestation IUHS on the immune, metabolic, and stress response of pigs subjected to an 8 hr lipopolysaccharide (LPS) challenge during postnatal life. Twenty-four pregnant gilts were exposed to thermoneutral (TN; n = 12; 17.5 ± 2.1 °C) or heat stress (HS; n = 12; cyclic 26 to 36 °C) conditions from days 6 to 59 of gestation, and then TN conditions (20.9 ± 2.3 °C) from day 60 of gestation to farrowing. At 12 wk of age, 16 IUHS and 16 in utero thermoneutral (IUTN) pigs were selected, balanced by sex and given an intravenous injection of LPS (2 µg/kg BW mixed with sterile saline [SAL] and injected at 2 µL/kg BW) or SAL (2 µL/kg BW). Body temperature was monitored every 30 min, and blood was obtained at 0, 1, 2, 3, 4, 6, and 8 hr following the LPS challenge. Blood samples were analyzed for glucose, insulin, non-esterified fatty acids (NEFA), cortisol, and cytokine concentrations. In addition, white blood cell counts were determined at 0 and 4 hr. Hour 0 data were used as covariates. Body temperature was increased (P < 0.01) in LPS (40.88 ± 0.08 °C) vs. SAL (39.83 ± 0.08 °C) pigs. Eosinophils tended to be decreased overall (P = 0.09; 43.9%) in IUHS vs. IUTN pigs. Glucose concentrations were reduced overall (P = 0.05; 5.9%) in IUHS vs. IUTN pigs. The NEFA concentrations tended to be greater (P = 0.07; 143.4%) in IUHS-LPS pigs compared with all other treatments, and IUTN-LPS pigs tended to have greater (127.4%) circulating NEFA concentrations compared with IUTN-SAL and IUHS-SAL pigs. Cortisol was increased (P = 0.04) in IUHS-LPS compared with IUTN-LPS pigs at 3 hr (21.5%) and 4 hr (64.3%). At 1 hr, tumor necrosis factor α was increased (P = 0.01; 115.1%) in IUHS-LPS compared with IUTN-LPS pigs. Overall, interleukin-1β (IL-1β) and interleukin-6 (IL-6) were greater (P < 0.04; 281.3% and 297.8%, respectively) in IUHS-LPS pigs compared with all other treatments, and IUTN-LPS pigs had increased IL-1β and IL-6 concentrations compared with IUTN-SAL and IUHS-SAL pigs. In summary, IUHS altered the postnatal cytokine, metabolic, and physiological stress response of pigs during postnatal life, which may have negative implications toward the innate immune response of IUHS pigs to pathogens.     

The effects of mutated skeletal ryanodine receptors on hypothalamic-pituitary-adrenal axis function in boars

The objectives of the current experiment were to determine whether boars heterozygous for the mutation in skeletal ryanodine receptors (sRyR), known to cause porcine stress syndrome, differed from wild-type boars in hypothalamic-pituitary-adrenal axis (HPA) function. We have examined basal plasma ACTH, cortisol, and corticosteroid-binding globulin (CBG) concentrations; plasma ACTH and cortisol responses to a nose-snare stressor and at slaughter; dexamethasone suppression of plasma ACTH and cortisol concentrations; and glucocorticoid receptor (GR) density in the pituitary gland, hippocampus, hypothalamus, and frontal cortex. We have also examined carcass yields, composition, and meat quality to determine whether differences in HPA activity were accompanied by an increased incidence of meat quality characteristics associated with pale, soft, exudative (PSE) meat. Thirty boars either heterozygous or wild-type (n = 15 per genotype) for mutated sRyR were tested for HPA function at 7 mo of age. Heterozygous boars had lower basal plasma ACTH (P < .05) and cortisol (P < .04) concentrations. Integrated basal plasma ACTH and cortisol levels were also lower (P < .05 and P < .005, respectively). Genotype had no significant effect on basal CBG, stressor-induced (nose snare or slaughter) or dexamethasone suppression of plasma ACTH or cortisol concentrations. No differences in immunoreactive GR levels were found in the pituitary gland or any brain region examined. We did find a significant, negative correlation (r = -.62, P < .02) between peak (0800) basal plasma ACTH concentrations and hippocampal GR levels. The alterations in basal HPA function in heterozygous boars were accompanied by lighter body weights (P < .03), decreased carcass fat depth (P < .04), and increased carcass lean yields (P < .02). There was a higher incidence of meat quality characteristics associated with PSE meat in heterozygous boars indicated by higher carcass temperatures (P < .04) and meat brightness (P < .0001) with lower carcass pH at slaughter (P < .03) and after chilling (P < .003). In conclusion, we have found differences in basal and not stressor-induced HPA function between boars heterozygous and wild-type for mutated sRyR. This altered basal HPA activity was accompanied by an increased incidence of meat quality aspects associated with PSE meat in heterozygous boars.     

Effect of spray-dried plasma and lipopolysaccharide exposure on weaned pigs: II. Effects on the hypothalamic-pituitary-adrenal axis of weaned pigs

A study was conducted with 20 weaned barrows (14 d, 4.98 +/- 0.21 kg) to determine the effect of feeding spray-dried plasma (SDP) after weaning on the pig's stress response to a lipopolysaccharide (LPS) challenge. After weaning, pigs were fed a diet containing 0 or 7% SDP for 7 d. On d 6 after weaning, all pigs were nonsurgically fitted with a jugular catheter. On d 7 after weaning, the pigs were given i.p. injections of either saline or LPS (150 microg/kg BW) followed by serial blood collection every 15 min for a 3-h period. Following the 3-h blood collection, all pigs were killed and tissue was collected for mRNA analysis. Pig weight on d 7 after weaning was not affected by dietary treatment (P > 0.21). Pigs fed the diet with SDP had lower (P < 0.05) levels of hypothalamic corticotropin-releasing hormone (CRH) mRNA, pituitary gland CRH receptor mRNA, and adrenal gland adrenocorticotropin-releasing hormone (ACTH) receptor mRNA. Dietary treatment did not affect pituitary gland proopiomelanocortin (POMC) mRNA. No effect of LPS treatment was observed in any of the mRNA levels examined. For both serum ACTH and cortisol, there was a significant diet x LPS treatment interaction (P < 0.01) such that both the ACTH and cortisol responses to the LPS challenge were greater in the pigs fed the diet with SDP than in the pigs fed the diet without SDP. For pigs given the saline injection, diet did not affect basal serum cortisol concentration; however, basal serum ACTH concentration was lower in those pigs fed the diet with SDP (P < 0.0001). A diet x LPS treatment interaction (P < 0.024) was observed for adrenal gland mRNA expression for steroidogenic acute regulatory (StAR) protein such that the LPS-induced increase in StAR mRNA was greater in the pigs fed SDP than in pigs fed the diet without SDP. These results demonstrate that pigs fed a diet with SDP have an increased activation of the pituitary-adrenal axis following an LPS challenge compared to pigs fed a diet without SDP.     

Administration of ACTH to restrained, pregnant sows alters their pigs' hypothalamic-pituitary-adrenal (HPA) axis

This study was designed to examine the physiology and behavior of pigs whose dams were snared and then injected with ACTH during gestation. Administration of ACTH to dams during pregnancy has been shown to replicate the effects of prenatal stress in other species. Control sows (n = 8) were given no treatment, whereas the treatment sows (ACTH, n = 8) were immobilized by snaring the snout and then administered an i.v. injection of ACTH (1 IU/kg BW) weekly from 6 to 12 wk of gestation. A pig was killed from each sow at 1, 30, and 60 d of age. The hypothalamus, pituitary gland, adrenal glands, and liver were immediately obtained to determine the amounts of corticotropin-releasing hormone (CRH), beta-endorphin, and mRNA for pro-opiomelanocorticotropin (POMC), the ACTH receptor (ACTH-R), and insulin-like growth factor I (IGF-I). Pituitary corticotrope and somatotrope cell numbers and adrenal cortex-to-medulla area ratios (CORT:MED) were also determined. Pigs' behaviors were recorded at 6 and 8 wk of age. At 75 d of age, a blood sample was taken and a biopsy puncture was created on one pig from each litter, then pigs were stressed by mixing. Blood was sampled every other day for 10 d to determine plasma cortisol concentrations and differential leukocyte counts. Biopsy damage was evaluated for healing. At 1 d of age, control pigs tended to weigh more (P = .09), have a lower expression of ACTH-R mRNA (P = .01) and IGF-I mRNA (P = .01), and a lower CORT:MED (P = .04) than ACTH pigs. At 30 d of age, control pigs had a greater concentration of beta-endorphin (P = .01) and tended to have a lower concentration of CRH (P = .09) and IGF-I mRNA (P = .10) than ACTH pigs. At 60 d of age, control pigs tended to have lighter pituitary glands (P = .08), a lower expression of POMC mRNA (P = .02), and a CORT:MED (P = .003) than ACTH pigs. At 8 wk of age, control pigs performed a higher frequency of belly nosing (P = .07) and oral vice behaviors (P = .01) than ACTH pigs. In response to mixing stress, control pigs had lesser concentrations of plasma cortisol (P = .03) and healed faster (P = .006) than ACTH pigs. Thus, exogenous ACTH and restraint during gestation alters the HPA axis of the sow's offspring, and during stressful situations later in life health, and therefore welfare, may be compromised.     

Maternal treatment with somatotropin alters embryonic development and early postnatal growth of pigs

A possible management strategy to alter fetal development and enhance sow productivity and progeny performance was examined by maternal administration of porcine somatotropin during early gestation. Eighteen crossbred gilts were bred naturally to boars of similar genetics, and pregnancy was confirmed between Days 21 and 24 of gestation by ultrasound. All animals were allowed ad libitum consumption of a 16% CP gestation diet through Day 21 of gestation and 3.0 kg/d for the remainder of gestation. Gilts were injected twice daily with 0 (n = 10) or 15 μg/kg body weight (BW) (n = 10; total, 30 μg/kg BW per d) pituitary-derived porcine somatotropin (pST) during Days 28 to 40 of gestation. Data were collected postmortem during embryonic, neonatal, and market-weight phases. At 41 d of gestation, pST treatment increased embryonic survival (87.9 versus 77.0%; P < 0.05) and embryo crown rump lengths (77.96 versus 65.14 mm; P < 0.01), but embryo weight was not altered (10.15 and 9.03 g; P > 0.10). Pigs from pST-treated gilts had increased (P < 0.01) crown rump lengths at birth (31.5 versus 30.4 cm) and 21 d (50.9 versus 48.4 cm). However, no differences were observed in birth or 21-d weights as a result of pST treatment (P > 0.10). Neonatal carcasses of progeny (20 kg BW) from the pST-treated gilts had heavier semitendinosus muscles (76.1 versus 66.0 g; P < 0.10), larger longissimus muscle cross-sectional area (10.1 versus 8.2 cm²; P < 0.05), longer sides (51.2 versus 47.9 cm; P < 0.001), and decreased 10th rib backfat (6.67 versus 8.64 mm; P < 0.001) compared with those of controls. Carcasses of market-weight progeny (100 kg BW) from pST-treated gilts had larger longissimus muscle cross-sectional area (P < 0.10), heavier trimmed loins (P < 0.10), and longer carcass sides (P < 0.05). Data are supportive of a hypothesis that mechanisms during early embryonic development are sensitive to manipulation through selected management strategies of the sow and that modifications of this strategy may serve as a model for the examination of molecular and cellular events controlling early embryonic growth.     

Evaluation of immune system function in neonatal pigs born vaginally or by Cesarean section

Full term crossbred sows were selected to study the interaction of the immune system, hypothalamus-pituitary-adrenal axis, and growth in pigs born by Cesarean section (c-section; n=4 sows) or vaginal birth (n=4 sows). Gestation length and birth weight did not differ between vaginal birth and c-section pigs (P=0.34 and 0.62, respectively). Blood and tissue samples were collected from 44 pigs at birth. Forty-five pigs were weaned at 13 d. On d 14, pigs received an i.p. injection of lipopolysaccaride (LPS; 150 microg/kg) or saline at min 0, and blood samples were collected at -20, -10, 0, 5, 10, 20, 40, 60, 90, and 120 min. Vaginal birth pigs had 21% greater average daily gain than c-section pigs on d 14 (P<0.01). Basal serum concentrations of adrenocorticotrophin (ACTH) and cortisol were greater in c-section than vaginal birth pigs at birth (P<0.01) but were not different at 14 d (P=0.99 and 0.80, respectively). LPS increased serum concentrations of ACTH, cortisol, interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha; P<0.01) but the response was not different between c-section and vaginal birth (P>0.22). Basal serum concentrations of TNF-alpha tended to be greater in c-section vs vaginal birth pigs at 14 d (P=0.0967); however, basal serum concentrations of IFN-gamma tended to be lower in c-section pigs vs vaginal birth pigs at 14 d (P=0.0787). Expression of interleukin (IL)-6, IL-6 receptor, IL-1beta, and TNF-alpha mRNA did not differ between vaginal birth and c-section pigs but changed in an age and tissue dependent manner. Thus, reduced growth rate of c-section pigs is associated with altered immune system function.     

Effect of injected and dietary iron in young pigs on blood hematology and postnatal pig growth performance

The relationship of injected Fe doses on blood hematology and pig growth performance during both preweaning and postweaning periods was studied. In Exp. 1, the effect of BW of 347 pigs injected with 200 mg of Fe (dextran) intramuscularly (i.m.) at birth on hemoglobin (Hb) and percent hematocrit (Hct) at weaning was assessed. As BW increased there was a decline (P < 0.01) in Hb and Hct. In Exp. 2, Fe injection doses and timing of injected Fe on blood hematology and pig growth were evaluated. Injections were as follows: 1) 200 mg of Fe at birth; 2) 300 mg of Fe at birth; or 3) 200 mg of Fe at birth + 100 mg of Fe at d 10. A total of 269 pigs were allotted within litter to 3 treatments. The 2 greater quantities of injected Fe (i.e., 300 or 200 + 100 mg of Fe) had similar but greater (P < 0.05) Hb and Hct values than pigs receiving 200 mg of Fe, but growth rates were similar at weaning. The effects of injecting 200 mg of Fe at birth and either saline or 100 mg of Fe at 10 d of age were investigated in Exp. 3. Weaned pigs of each group were fed diets with 0, 80, or 160 mg/kg of added Fe for 35 d as a 2 × 3 factorial arrangement with 12 replicates (n = 360 pigs) in a randomized complete block design (RCB). The innate Fe contents of diets averaged 200 mg/kg. The greater Fe injection group (200 + 100 mg) had greater (P < 0.01) Hb and Hct values through 14 d postweaning (P < 0.05) and greater (P < 0.01) Hct values through 21 d postweaning. As dietary Fe increased, Hb was greater only at d 14 (P < 0.05 4), whereas Hct increased linearly to d 35 (P < 0.01) postweaning. Dietary Fe resulted in linear increases (P < 0.01) in ADG from d 21 to 35 and d 0 to 35. In Exp. 4, 3 dietary Fe (80, 160, and 240 mg/kg of diet), 2 injected Fe treatments (200 or 300 mg of Fe) at birth, and birth BW (<1.5 or ≥1.5 kg) were evaluated as a 2 × 2 × 3 factorial arrangement of treatments in a RCB design with 6 replicates (n = 280 pigs). The 300 mg of Fe injection group had lighter BW in both birth BW groups, with a birth BW × injected Fe interaction (P < 0.01). This resulted in the lighter birth BW pigs receiving 200 mg of Fe having greater BW gains to 240 mg/kg of dietary Fe, whereas light birth BW pigs injected with 300 mg of Fe plateaued at 160 mg/kg of Fe. Pigs in the heavy birth BW group injected with 200 or 300 mg of Fe at birth responded similarly to dietary Fe postweaning. These results indicate that blood Hb and Hct were affected by pig BW at weaning, but the additional 100 mg of Fe i.m. at 10 d of age increased blood hematology and that Fe injected preweaning affected initial postweaning performance.     

仔猪的饲养需求

<正>断奶后的日粮种类和饲养管理措施为仔猪终生生长性能奠定基础。每当改进后的遗传学被用来提高猪的生产效率和生产瘦肉率更高的猪时,养猪场所采用的营养方案就需要重新探讨,以确保能够取得最大的生产效益,并满足为达到目标胴体所需的营养需求。     

Clinical effects of short-term oral budesonide on the hypothalamic-pituitary-adrenal axis in dogs with inflammatory bowel disease

Six dogs were entered into a 30-day, prospective, nonrandomized, uncontrolled clinical trial evaluating the effects of an oral preparation of budesonide on the hypothalamic-pituitary-adrenal (HPA) axis during therapeutic management of active inflammatory bowel disease. Oral budesonide, at a dose of 3 mg/m(2), was administered once daily. Upon entry and completion of the trial, serum basal cortisol, adrenocorticotropic (ACTH)-stimulated cortisol, endogenous ACTH concentration, serum alkaline phosphatase (SAP) activity, and urine specific gravity were evaluated, as well as owner assessment of glucocorticoid-associated side effects. Significant suppression of the HPA axis occurred. No significant differences in SAP activity, urine specific gravity, or owner-subjective assessments were detected.     

Activation of the ovine hypothalamic-pituitary-adrenal axis and febrile response by interleukin-6: A comparative study with bacterial lipopolysaccharide endotoxin

Sheep were subjected to immune challenge with either recombinant human interleukin-6 (rhIL-6; 2.0 μg/kg; n = 5), Escherichia coli lipopolysaccharide (LPS) endotoxin (400 ng/kg; n = 7), or saline (n = 6) to determine if IL-6 activates the febrile and hypothalamic-pituitary-adrenal axis (HPAA) responses in sheep, and to compare these responses with those associated with endotoxemia. Blood was collected over time to measure plasma adrenocorticotropic hormone (ACTH) and serum cortisol concentrations as indicators of HPAA activity. Unlike LPS, rhIL-6 was not pyrogenic in sheep at this challenge dose. In contrast, rhIL-6 elicited ACTH and cortisol responses that peaked earlier than those induced by LPS. These results suggest that this dose of IL-6, alone, is not sufficient to elicit the febrile response in sheep, however, it is a potent activator of the ovine HPAA response.     

Temperament and hypothalamic-pituitary-adrenal axis function are related and combine to affect growth, efficiency, carcass, and meat quality traits in Brahman steers

Associations between temperament, stress physiology, and productivity were studied in yearling Brahman steers (n = 81). Steers differed in calpain system gene marker status; 41 were implanted with a hormonal growth promotant at feedlot entry. Temperament was assessed with repeated measurements of flight speed (FS) and crush score (CS) during 6 mo of backgrounding at pasture and 117 d of grain finishing. Adrenal responsiveness was assessed with ACTH challenge, with plasma samples collected immediately before and 60 min after challenge. Steers with higher FS and CS had higher prechallenge plasma cortisol, glucose, lactate, and nonesterified fatty acid concentrations. The ACTH-induced cortisol response was unrelated to FS or CS, but glucose remained higher after challenge in flightier steers. The hormonal growth promotant reduced adrenal responsiveness; tenderness genotype had no effect. When temperament assessments and cortisol concentrations before and after challenge were combined in a principal components analysis, four vectors accounting for 38%, 25%, 18%, and 9% of the variation were identified. The first vector had significant loadings on temperament and prechallenge cortisol; increasing scores were associated with increased plasma glucose, lactate, and nonesterified fatty acid and with reductions in BW and feedlot growth rates, carcass fatness, and muscle pH. The second vector loaded only on ACTH-induced cortisol response; increased scores related to increased residual feed intake, number of daily feed sessions, and meat marbling score. The third and fourth vectors had different loadings on FS and CS and appeared to identify different aspects of temperament measured by FS or CS. Fewer associations were found between the third or fourth vectors and productivity traits, possibly because of lower variance accounted for by these vectors. In conclusion, temperament was related to prechallenge cortisol but not to ACTH-induced cortisol response. Principal components analysis separated these traits into separate components, which in turn had different relations with productivity traits. The largest component of temperament was described similarly by FS and CS, but there were smaller components that these described differently. There were some temperament-related differences in the metabolic status of the steers which were not related to the variation in cortisol, suggesting involvement of the sympatho-adrenal-medullary axis in these temperament-related effects.