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1.
Following weaning at 24 +/- 1 d of age, crossbred boars were subjected to removal of the cranial cervical ganglia (GX, n = 8) or sham surgery (SHAM, n = 8). At 213 +/- 1 d of age, a catheter was inserted into a jugular vein or vena cava, and all boars were housed in environmentally controlled rooms at 22 degrees C with an equatorial photoperiod. After 2 wk of exposure to this photic environment, samples of plasma and serum were collected at hourly intervals for 24 h. The plasma was assayed for adrenocorticotropic hormone (ACTH) and the serum was assayed for cortisol and melatonin by RIA. The time-trends for all three hormones were described by regression models, which were tested for heterogeneity of regression between SHAM and GX treatments. The circadian rhythm of cortisol in serum was similar for SHAM and GX treatments. The profiles of ACTH were also similar between the two treatments, but circadian changes in concentrations of ACTH paralleling those of cortisol were not evident in either treatment. Overall, concentrations of ACTH were reduced (P = .06) for GX boars compared to SHAM boars. The time-trends of melatonin in serum differed (P less than .001) for GX and SHAM treatments, with a nocturnal rise in melatonin evident in some SHAM boars but not in GX animals. Four SHAM boars had profiles of melatonin that obviously entrained to the light-dark cycle. None of the boars in GX treatment had elevated concentrations of melatonin in serum during the dark period, relative to concentrations during the light.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

2.
Four pubertal (25 wk) crossbred boars were used to evaluate the role of the photoperiod in the organization of secretion of cortisol and melatonin throughout a 24-hr period. Boars were exposed to a 16-hr photoperiod in an environmentally controlled room and temperature was kept constant at 22 C. For the first 15 d, the onset of the photophase (light phase) and scotophase (dark phase) was 0200 hr and 1800 hr, respectively (ON2). During the final 15 d, the onset of the photophase and scotophase was advanced by 6 hr (0800 hr and 2400 hr, respectively; ON8). Samples of serum were obtained from catheterized boars at hourly intervals for 24 hr between the 14th to 15th d in both ON2 and ON8 photoperiods. Samples of serum were frozen and later assayed for cortisol and melatonin. The data were normalized to the clock time of onset of the photophase, fit to polynomial equations, and the profiles of cortisol and melatonin in ON2 and ON8 were tested for heterogeneity of regression. A circadian rhythm of cortisol was observed in both ON2 and ON8 and the fitted profiles were parallel, suggesting that the rhythm had shifted with the 6-hr shift in lights-on, lights-off. Generally, higher concentrations were observed during the late subjective evening and scotophase, whereas lower concentrations occurred about 6 to 10 hr after onset of the photophase. Although the profiles of melatonin did not differ in ON2 and ON8, there was no evidence of a nocturnal rise in melatonin in either treatment. It is suggested that some characteristic of the photoperiod organizes the circadian rhythm of cortisol in boars, but melatonin is not secreted in a rhythmic fashion in long photoperiods.  相似文献   

3.
In the domestic pig, a circadian rhythm of plasma cortisol occurs, with greatest concentrations in the morning and lowest concentrations in the afternoon. However, photic entrainment of the rhythms of ACTH and melatonin in pigs have not been defined clearly. This experiment was designed to evaluate free-running rhythms of ACTH, cortisol and melatonin in pigs housed in constant light (LL) and constant darkness (DD). Twelve crossbred barrows, maintained under ambient photoperiod, were catheterized and tethered individually in two environmentally controlled rooms, one with LL and the other with DD. For animals in LL, fluorescent lights provided 202 +/- 15 (mean +/- standard deviation) lux of light at 65 cm above the floors. Incandescent nightlights equipped with 7 watt red bulbs provided 7 +/- 2 lux and were illuminated continuously in both rooms. Pigs were given at least 14 d exposure to LL and DD, then samples of plasma and serum were obtained at hourly intervals for 48 hr. Plasma was assayed for ACTH, and serum for cortisol and melatonin. Periodograms were constructed to analyze the data. For this type of analysis, a statistic, Qp, is calculated, and circadian periodicity is suggested if maximum Qp (Qp max) occurs at or near 24 hr. The period of the free-running rhythms (tau) at Qp max for ACTH, cortisol and melatonin for pigs in LL (23.80 +/- .01, 23.78 +/- .01, and 23.21 +/- .02 hr, respectively) did not differ significantly from those for pigs in DD (23.39 +/- .01, 23.20 +/- .01, and 22.55 +/- .02 hr, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

4.
To study porcine melatonin secretion in a stable environment 3 daytime (10.00-15.00) and 3 nighttime (22.00-03.00) plasma samples were collected by jugular venipuncture from 15 gilts, 16 sows, 3 boars and 48 piglets (24 females and 24 males from 8 litters) and analysed for melatonin content. Nighttime melatonin concentrations were higher than daytime melatonin concentrations (p < 0.001), whereas no effect of sampling order could be discerned. The 3 adult Hampshire boars had higher melatonin concentrations during the day and the night, than the 31 adult Yorkshire females (p < 0.05). There was no clear difference between gilts and sows in plasma melatonin. The gilts from one of the litters had higher plasma melatonin concentrations than the gilts in 3 other litters (p < 0.05). Among the 48 piglets, the increase of nocturnal melatonin secretion differed between litters (p < 0.01), whereas the influence of father was not quite significant (p = 0.12). No difference in daytime melatonin concentrations between litters could be found, and there was no difference in melatonin levels between the male and female piglets. In conclusion, this study demonstrates that domestic pigs express a nocturnal increase of melatonin secretion in a standard stable environment. For some animals the amplitude of nighttime melatonin secretion was very low, although always higher than the daytime base levels. Furthermore, the levels of nighttime melatonin secretion differed between litters, which suggests a genetic background.  相似文献   

5.
The aims of this study were to examine whether mouflons exposed to constant long and short day photoperiods are able to exhibit an annual cycle of hair growth and moult, and prolactin (PRL) secretion. Mouflon ewes were assigned to three groups of treatment. Ewes were maintained, either under natural photoperiod (control, n=9), or received a series of subcutaneous melatonin implants from December to April (n=8), or were exposed to a constant long day photoperiod (16-h light:8-h dark; 16L:8D) during 18 months (n=7). Blood was collected weekly to determine PRL concentrations, and hair samples were clipped weekly from the base of the neck to measure the length of predominant hair. Under constant long days and with melatonin implants, mouflons expressed an annual rhythm of PRL secretion, even though these treatments modified the times of rise or falling of PRL concentrations throughout the year. Hair growth initiation was almost coincident with the summer solstice in both control and melatonin-implanted mouflons but occurred two months earlier in long day hold mouflons (P<0.001). Long day hold mouflons had a lower hair growth rate than control and melatonin-implanted mouflons (P<0.001), and at the end of the experiment, a shorter hair length (3.4±0.24 cm; P<0.01) than control (4.3±0.17 cm), and melatonin-implanted mouflons (4.2±0.12 cm). Our data support the conclusion that in mouflon, an endogenous circannual rhythm of PRL secretion exists, and that the seasonal cycle of hair growth and moult appears to depend, at least in part, on circulating levels of PRL.  相似文献   

6.
This study was performed to determine whether in dogs with pituitary-dependent hyperadrenocorticism (PDH) excessive release of adrenocorticotrophic hormone (ACTH) is accompanied by secretion of ACTH precursor molecules. In addition, we investigated whether the plasma ACTH precursor concentrations were correlated with the size of the pituitary gland and with the degree of resistance to negative glucocorticoid feedback. In 72 dogs with PDH, the plasma ACTH precursor concentration was determined by calculating the difference between the results of a radioimmunoassay (RIA) in which besides ACTH, ACTH precursors were also measured and a highly specific immunoradiometric assay (IRMA) using a polyclonal antibody against ACTH. The degree of resistance to glucocorticoid feedback was established by determining the effect of dexamethasone administration (0.1 mg/kg) on the urinary corticoid/creatinine ratio. The pituitary height/brain area (P/B) ratio, determined by computed tomography, was used as a measure for the size of the pituitary gland. The plasma ACTH precursors concentration ranged from 18 to 2233 ng/L (median 93 ng/L). In 38 dogs, the pituitary was enlarged and plasma ACTH precursors concentrations in these dogs (median 130 ng/L, range 24–2233 ng/L) were significantly (P<0.05) higher than those in the dogs without pituitary enlargement (median 72 ng/L, range 18–481 ng/L). In concordance, P/B ratios correlated significantly with plasma ACTH precursor concentrations (r=0.35, P<0.01). In addition, the P/B ratios were significantly correlated with the degree of dexamethasone resistance (r=0.42, P<0.001). Plasma ACTH precursor concentrations in the dexamethasone-resistant dogs (median 210 ng/L, range 24–628 ng/L) were significantly higher (P<0.01) than those in the dexamethasone-sensitive dogs (median 72 ng/L, range 18–2233 ng/L). Similarly, the degree of dexamethasone resistance was also significantly correlated with the plasma ACTH precursor concentrations (r=0.33, P<0.01). Dogs with an elevated plasma -MSH concentration (n=14) had significantly (P<0.001) higher plasma ACTH precursor concentrations (median 271 ng/L, range 86–2233 ng/L) than dogs with non-elevated -MSH (median 73 ng/L, range 18–481 ng/L). In addition, the plasma concentrations of -MSH correlated significantly with both plasma ACTH precursor concentrations (r=0.53, P<0.001) and P/B ratios (r=0.26, P<0.05). In conclusion, in all dogs with PDH the ACTH concentrations determined by the RIA were higher than the concentrations measured by IRMA indicating the presence of circulating ACTH precursors. High plasma ACTH precursor concentrations were especially found in dexamethasone-resistant dogs with large corticotroph adenomas, some of them probably of PI origin. In the association of large corticotroph adenoma, dexamethasone resistance and high plasma concentrations of ACTH precursors, the decreased sensitivity of the corticotroph cells to glucocorticoid feedback may play a pivotal role.  相似文献   

7.
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.  相似文献   

8.
The objective of this experiment was to develop a procedure for immunizing ewes against melatonin that would alter the effects of changing photoperiod on seasonal reproduction and prolactin secretion. Ewes were immunized against human serum albumin (HSA) as controls (n = 9) or a melatonin-human serum albumin conjugate (0.25 mg; n = 10) on December 14th (Day 0) and boosted 9 times. They were maintained on natural photoperiod and then transferred indoors and exposed to long days for 35 d, followed by short days for 146 d, long days for 93 d, and short days for a further 123 d. Antibody titers to melatonin (at a serum dilution of 1:1,250) were significantly higher in immunized ewes (27.3 ± 6.6%) than controls (0.7 ± 0.1%; P < 0.001). At the end of the experiment, antibody titers in immunized ewes (at dilution of 1:50) were higher in blood (43.7 ± 8.2%) than in cerebrospinal fluid (10.8 ± 3.9%; P < 0.05), and highly correlated (r2 = 0.746). Onset of the breeding season was advanced slightly after the second transfer from long to short days in immunized ewes (April 12 ± 3 d) compared with controls (April 25 ± 3 d; P < 0.05). Mean serum prolactin concentrations were lower (P < 0.05) in melatonin-immunized ewes compared with controls on natural photoperiod, after transfer from long to short days, during long days, and after the second transfer from long to short days. In conclusion, despite melatonin-immunization increasing antibody titers in blood and cerebrospinal fluid, and decreasing prolactin concentrations over much of the experiment, minimal effects on the timing of reproductive transitions in the ewes were evident. This discrepancy between the response of the prolactin and reproductive axes to melatonin immunization supports the hypothesis of a dual site of action of melatonin, with melatonin acting in the pituitary gland to mediate the effects of photoperiod on prolactin secretion and in the mediobasal hypothalamus to affect reproductive responses.  相似文献   

9.
This study compares morphological changes, performed with real-time transrectal ultrasonography, of testis and accessory glands and seasonal endocrine changes in a wild (Mouflon) and a domesticated (Spanish Merino) breed of sheep. In Mouflons, the maximum plasma testosterone concentrations, testicular diameter and vesicular gland size occurred synchronously during autumn (P < 0.001). In Merino rams the highest circulating levels of testosterone (P < 0.05) and maximum testicular diameter (P < 0.001) occurred during summer, with no seasonal variations in vesicular and bulbourethral glands. The seasonal changes in plasma concentrations of prolactin were not correlated with annual variations in testicular and glandular size in neither wild nor domestic species. No differences were observed between both species for the seasonal pattern of prolactin secretion and mean amplitude of melatonin. Wide differences in reproductive patterns between wild and domestic types of rams do not appear to be attributed to seasonal changes in prolactin and melatonin secretion.  相似文献   

10.
Seasonal serum concentrations of melatonin in cycling and noncycling mares   总被引：1，自引：0，他引：1  
To determine whether secretory patterns of melatonin change throughout the seasons in mares, blood samples were drawn byvenipuncture from nine mares at noon and midnight for five successive days at monthly intervals from August through July at the University of Missouri in Columbia, MO. In addition, during September, December, March, and June, blood samples were drawn from indwelling catheters at 2-h intervals for 48 or 72 h. Mares were predominantly Quarter Horses weighing approximately 450 kg and ranged from 3 to 12 yr of age. Mares were housed in outdoor paddocks with three-sided run-in sheds for shelter. During the noon and midnight bleeding period, mares were placed in a larger open-sided barn with outside runs. Mares remained outdoors with the barn being used as a shelter in the event of inclement weather. All lights in the shed were converted to red light. Often, moonlight provided enough illumination to collect blood samples. Mares were returned to their normal paddock after each sampling period. For analysis of data, a mare was considered to be cycling if serum concentrations of progesterone were greater than 1 ng/ mL. For a mare to be classified as exhibiting a nocturnal rise of melatonin, serum concentrations of melatonin had to be at least two times greater at midnight than at noon. By month, a relationship did not exist (chi2; P > 0.05) among mares that were exhibiting estrous cycles and exhibiting nocturnal rises of melatonin. Likewise, examination of serum profiles of melatonin taken at 2-h intervals for 48 h revealed considerable variation among mares throughout the seasons. A nocturnal rise in serum melatonin was observed only in June (P < 0.02). In March and December, serum melatonin was greater in cycling mares than noncycling mares, but the elevation was not associated with light-dark periods (P < 0.01). Two of the mares exhibited estrous cycles throughout the seasons but melatonin secretion in these two mares were similar to that observed in the seven mares that demonstrated seasonal anestrous. From these results, it does not appear that changes in serum concentrations of melatonin are used as a cue to regulate cyclic activity in the mare throughout the seasons.  相似文献   

11.
Two experiments were conducted to determine if feeding melatonin alters plasma concentrations of melatonin, growth and carcass composition of postpubertal beef heifers exposed to 16 h light (L):8 h dark (D). In Exp. 1, 16 heifers were blocked by initial body weight (318 +/- 5.6 kg). Four heifers were killed before starting the melatonin treatment to obtain initial carcass composition. Six heifers received vehicle (95% ethanol) and six were fed melatonin (4 mg/100 kg body weight) daily for 58 d at 1330 to coincide with the middle of the 16-h light period. On d 59 heifers were slaughtered. Melatonin feeding increased the percentage of fat in rib (P less than .05) and longissimus muscle (LD; P less than .10) and carcass fat accretion 28% (P less than .09) but reduced the percentage of protein 8% in rib (P less than .05) and carcass protein accretion 30% (P less than .09). Other measures in the carcass and body weight gain were not affected (P greater than .10) by feeding melatonin. Plasma concentrations of melatonin increased (P less than .01) from 10 to 140 pg/ml within 30 min of feeding melatonin. In Exp. 2, 24 heifers were blocked by initial body weight (348 +/- 13.7 kg). Eight heifers were killed initially, eight received vehicle and eight were fed melatonin for 63 d as described in Exp. 1. Melatonin did not influence (P greater than .10) body weight gain or any measure in the carcass; however, these heifers were fatter (40.1%) than those in Exp. 1 (30.9%) at the beginning of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

12.
A direct radioimmunoassay procedure for the determination of melatonin in the blood of blue fox has been validated and applied.The assay required 50 μl of sample and standard, 100 ul of antiserum and 100 μl of (3H)melatonin. After overnight incubation at 4°C the antibody bound melatonin was separated from the free hormone with dextran-coated charcoal. Following centrifugation the antibody bound (3H)melatonin was determined in a beta scintillation counter.The antiserum bound 30–35 % of the (3H)melatonin at a final dilution of 1:36000. The non specific binding represented less than 5% of the total radioactivity in all assays. The lowest detectable amount of melatonin was 2.6 fmol/tube, corresponding to 52.5 pmol/1. The inter-assay coefficient of variation at 178 and 510 pmol/1 was 15.6 and 8.8%, respectively. The precision profile, calculated from a 10-replicate standard curve, showed that the coefficient of variation decreased from 43% at 84 pmol/1 to 15% at 336 pmol/1, and remainded at or below 10% for concentrations exceeding 670 pmol/1.Plasma was collected from 2 male blue foxes at about hourly intervals during a 24 h period in September and assayed for melatonin. Maximum (421 pmol/1) and minimum (97 pmol/1) concentrations of the hormone were inversely related to light intensity.  相似文献   

13.
Experiments were conducted to determine if a nocturnal rise in serum melatonin occurs in prepubertal gilts and whether acute exposure of gilts to light during the dark period abruptly reduces serum concentrations of melatonin. In experiment 1, 12 prepubertal crossbred gilts (Duroc x Hampshire x Chester White x Yorkshire) weighing 96.4 + 1.3 kg at 5.1 + .1 mo of age were housed in an LD cycle of 10:14. Following a 3-wk acclimation period, blood samples were drawn at 1-hr intervals from indwelling jugular catheters. Serum concentrations of melatonin were similar (P greater than .05) among blood samples collected during light and dark periods. In experiment 2, serum concentrations of melatonin did not change (P greater than .05) when gilts were abruptly exposed to light during the normal dark period. In experiment 3, serum concentrations of melatonin were similar (P greater than .05) in blood samples collected at 2-hr intervals under 700 lux of light or in total darkness from gilts maintained in either LD 9:15 or LD 24:0. Data from experiment 4 demonstrated that serum melatonin could be detected in nighttime samples if exogenous melatonin was ingested by gilts at night. Together, these experiments clearly indicate that prepubertal gilts do not exhibit a nocturnal rise in serum melatonin when maintained under short daylengths (10L:14D or 9L:15D), and serum melatonin concentrations are unaffected by abrupt changes in light/dark conditions.  相似文献   

14.
The effects of weaning age, type of creep diet and the classification of piglets as ‘eaters’ or ‘non eaters’ of creep feed on weight gain to weaning were examined. Four antimicrobial-free diets were offered from day 14 of lactation: (i) wheat-soy based diet with animal and vegetable (‘mixed’) protein sources (COMM), (ii) heat-processed rice (HPR) with barley hulls and potato starch and mixed protein sources (RBPS), (iii) HPR with sugar-beet pulp and mixed protein sources (RSBP), and (iv) HPR with mixed protein sources (R). Pigs were weaned at an average of either 27 (early) or 33 (late) days of age. A dye (indigo carmine) was added to each diet at day 24 of lactation in both groups to classify piglets as ‘eaters’ or ‘non eaters’ of creep feed, based on appearance or non-appearance, respectively, of dye in faeces. Pigs weaned late weighed 1.4 kg more (P < 0.001). Weaning age interacted with diet type and eating classification for weaning weight (P < 0.001). Of the 1067 piglets where classification of the faecal dye was possible, 829 (77.7%) were ‘eaters’ and 238 (22.3%) were ‘non eaters’. This qualitative estimate of creep feed consumption did not influence weight gain to weaning (P > 0.05).  相似文献   

15.
Prolactin (PRL) was found to have a stimulatory effect on adrenal steroidogenesis in vivo and in vitro in several species including pigs. PRL signal transduction pathways, however, in adrenocortical cells are poorly recognized. Therefore, the goal of this paper is to ascertain the involvement of protein kinase C (PKC) and tyrosine kinases in PRL signaling in porcine adrenal cortex. Adrenals were harvested from locally slaughtered mature gilts. Cortical cells were dispersed by sequential treatment with collagenase. The cells were seeded into 24-well culture plates at a density of 3×105/mL. Cells were incubated with or without PRL (500 ng/mL), ACTH (5 nM—a positive control), tyrosine kinase inhibitor—genistein (1; 2.5 or 5 μM), PKC inhibitor—sphingosine (20–1000 nM) and PKC activators—diacylglycerol (DiC8; 10–100 μM) and phorbol ester (PMA; 1–1000 nM). All incubations were performed for 8 h (95% air and 5% CO2, 37°C). PRL and ACTH (P<0.05) increased cortisol and androstenedione (A4) secretion. DiC8 and PMA mimicked the stimulatory effect of PRL. Sphingosine (P<0.05) suppressed basal and PRL-stimulated steroid secretion. Genistein inhibited (P<0.05) PRL-stimulated cortisol secretion and enhanced (P<0.05) basal and PRL-stimulated A4 secretion. Moreover, PKC activation was assessed by measuring the specific association of [3H]phorbol dibutyrate ([3H]PDBu) with adrenocortical cells after treatment with PRL or ionomycin (a positive control). PRL (within 2–3 min) and ionomycin (within 2–5 min) increased (P<0.05) specific binding of [3H]PDBu to the porcine adrenocortical cells. In addition, PRL did not augment the cortisol and A4 secretion by PKC-deficient adrenocortical cells. In conclusion, presented results support the hypothesis that PKC and tyrosine kinases are involved in PRL signaling in adrenocortical cells in pigs. Moreover, activation of PKC is associated with the increased secretion of cortisol and A4.  相似文献   

16.
The objective of this study was to examine the effects of somatotropin (ST) on porcine reproductive and metabolic statuses during early pregnancy. Four pregnant crossbred gilts received 6 mg of recombinant porcine somatotropin (rpST) daily from days 10 to 27 after artificial insemination while six pregnant gilts served as controls. Blood samples were taken on days 8, 10, 12, 14, 18, 22, and 27 prior to rpST injections (8:00 h) and subsequently at 9:00, 10:00, 12:00, 14:00, 16:00, 18:00, and 20:00 h. On all remaining days of treatment, samples were taken once daily before injections (8:00 h). The samples were assayed for the metabolic hormones: ST, insulin-like growth factor I (IGF-I), insulin, thyroxine (T4), triiodothyronine (T3), and cortisol; for metabolites: free fatty acids (FFA) and glucose; and for the reproductive hormones: luteinizing hormone (LH), progesterone, estradiol-17β, estrone sulfate, and prostaglandin F2. Delivery of rpST daily induced a 20- to 40-fold increase in plasma ST concentrations. Moreover, repeated administration of rpST resulted in a continuous increase in plasma IGF-I concentration (P<0.001), from 191.0±22.3–340.0±15.3 ng/mL 24 h after initial injection to 591.3±46.8 ng/mL after final injections. Mean serum insulin tended to be greater in rpST-treated gilts. Blood concentrations of T4 were reduced (P<0.05) from day 14 of gestation in treated gilts while T3 concentrations remained unchanged. Concentrations of both glucose and FFA were greater (P<0.01) and cortisol concentrations were unchanged in treated gilts. Changes in reproductive steroid hormones were minimally affected. Circulating progesterone (P=0.078), and estradiol-17β (P=0.087) concentrations tended to be lower in treated animals. These data show that treatment of pregnant gilts with rpST during early gestation mainly impacts metabolic rather than reproductive status.  相似文献   

17.
The epidemiologies of the most common diseases diagnosed in pigs at the Danish pig-breeding test stations were studied with special reference to possible genetic predisposition. The population under study comprised 9084 test pigs (corresponding to 3028 test groups) housed at nine test stations from September 1983 to September 1984. There were substantial differences between the four breeds in the study (Landrace, Yorkshire, Duroc and Hampshire) with the white breeds having higher clinical incidences of respiratory diseases and culling rates than the coloured ones. In only one of nine analyses was a significant sire effect found. However, significant differences were found between breeding centres of origin. There was a negative influence of clinical diseases on daily gain and feed conversion. Classifying respiratory disease in an ‘early’ form (at least one pig in the group was treated during the first 45 days of the test period) and a ‘late’ form (treatments were given after this period) showed that late infections resulted in a higher reduction of performance than early infections did. There were no associations between pathological findings at slaughter and growth rate.  相似文献   

18.
We developed three different knowledge-dissemination methods for educating Tanzanian smallholder farmers about mastitis in their dairy cattle. The effectiveness of these methods (and their combinations) was evaluated and quantified using a randomised controlled trial and multilevel statistical modelling. To our knowledge, this is the first study that has used such techniques to evaluate the effectiveness of different knowledge-dissemination interventions for adult learning in developing countries.

Five different combinations of knowledge-dissemination method were compared: ‘diagrammatic handout’ (‘HO’), ‘village meeting’ (‘VM’), ‘village meeting and video’ (‘VM + V’), ‘village meeting and diagrammatic handout’ (‘VM + HO’) and ‘village meeting, video and diagrammatic handout’ (‘VM + V + HO’). Smallholder dairy farmers were exposed to only one of these interventions, and the effectiveness of each was compared to a control (‘C’) group, who received no intervention. The mastitis knowledge of each farmer (n = 256) was evaluated by questionnaire both pre- and post-dissemination.

Generalised linear mixed models were used to evaluate the effectiveness of the different interventions. The outcome variable considered was the probability of volunteering correct responses to mastitis questions post-dissemination, with ‘village’ and ‘farmer’ considered as random effects in the model. Results showed that all five interventions, ‘HO’ (odds ratio (OR) = 3.50, 95% confidence intervals (CI) = 3.10, 3.96), ‘VM + V + HO’ (OR = 3.34, 95% CI = 2.94, 3.78), ‘VM + HO’ (OR = 3.28, 95% CI = 2.90, 3.71), ‘VM + V’ (OR = 3.22, 95% CI = 2.84, 3.64) and ‘VM’ (OR = 2.61, 95% CI = 2.31, 2.95), were significantly (p < 0.0001) more effective at disseminating mastitis knowledge than no intervention.

In addition, the ‘VM’ method was less effective at disseminating mastitis knowledge than other interventions. Combinations of methods showed no advantage over the diagrammatic handout alone. Other explanatory variables with significant positive associations on mastitis knowledge included education to secondary school level or higher, and having previously learned about mastitis by reading pamphlets or attendance at an animal-health course.  相似文献   


19.
Thyroid status is compromised in a variety of acute and chronic infections. Conversion of thyroxine (T4) into the metabolically active hormone, triiodothyronine (T3), is catalyzed by 5′-deiodinase (5′D) mainly in extrathyroidal tissues. The objective of this study was to examine the effect of protozoan parasitic infection (Sarcocystis cruzi) on hepatic 5′D (type I) activity and plasma concentrations of T3 and T4 in placebo- or bovine GH (bGH)-injected calves. Holstein bull calves (127.5±2.0 kg BW) were assigned to control (C, ad libitum fed), infected (I, 250,000 S. cruzi sporocysts per os, ad libitum fed), and pair-fed (PF, non-infected, fed to intake of I treatment) groups placebo-injected, and three similar groups injected daily with pituitary-derived bGH (USDA-B-1, 0.1 mg/kg, i.m.) designated as CGH, IGH and PFGH. GH injections were initiated on day 20 post-infection (PI), 3–4 days prior to the onset of clinical signs of the acute phase response (APR), and were continued to day 56 PI at which time calves were euthanized for liver collection. Blood samples were collected on day 0, 28, and 55 PI. Alterations in nutritional intake did not affect type I 5′D in liver. Treatment with bGH increased (P<0.05) 5′D activity in C (24.6%) and PF (25.5%) but not in I calves. Compared to PF calves, infection with S. cruzi reduced 5′D activity 25% (P<0.05) and 47.8% (P<0.01) in placebo- and bGH-injected calves, respectively. Neither nutrition nor bGH treatment significantly affected plasma concentrations of T4 and T3 on day 28 and 55 PI. However, plasma thyroid hormones were reduced by infection. On day 28 PI, the average plasma concentrations of T3 and T4 were reduced in infected calves (I and IGH) 36.4% (P<0.01) and 29.4% (P<0.05), respectively, compared to pair-fed calves (PF and PFGH). On day 55 PI, plasma T3 still remained lower (23.7%, P<0.01 versus PF) in infected calves while plasma T4 returned to control values. The data suggest that parasitic infection in growing calves inhibits both thyroidal secretion and extrathyroidal T4 to T3 conversion during the APR. After recovery from the APR, thyroidal secretion returns to normal but basal and bGH-stimulated generation of T3 in liver remains impaired.  相似文献   

20.
Large variations in the level of 5α-androstenone in fat from different boars have been found. No significant difference in the level of 5α-androstenone was detected in fat from boars selected for high rate of gain and low back fat (HP-line), low rate of gain and high degree of fatness (LP-line) and a control group maintained without deliberate selection (GL-line). In boars used in artificial insemination service relatively high levels of 5α-androstenone in fat were observed, and in these animals a significant (P < 0.05) positive regression of 5α-androstenone level on age was found. Positive but non-significant regression coefficients were found between number of services which the boars had performed and level of 5α-androstenone in fat from the same animals.  相似文献   

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