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1.
Two experiments were conducted to determine whether oral administration of melatonin alters the onset of puberty in gilts during naturally increasing or decreasing daylength. In Exp. 1, 20 crossbred prepubertal gilts weighing 77.5 +/- .5 kg at 171.8 +/- 1.0 d of age were assigned randomly to receive either a daily oral dose of 3 mg of melatonin (MEL) or ethanol vehicle (ETH) at 1530 from August 31 to December 1, 1987 (decreasing daylength). Gilts were exposed to mature boars for 20 min thrice weekly and blood samples were collected twice weekly. Serum concentrations of progesterone were used to establish age at puberty and length of estrous cycle. In Exp. 2, 20 crossbred prepubertal gilts weighing 67.7 +/- .7 kg at 143.8 +/- 1.1 d of age received either MEL or ETH treatment from February 1 to May 15, 1988 (increasing daylength). Age of puberty was less in gilts that received MEL than in gilts that received ETH in both Exp. 1 (198 +/- 3 vs 228 +/- 7 d; P less than .01) and Exp. 2 (183.8 +/- 2.7 d vs 194.3 +/- 3.3 d; P less than .05). Gilts that received MEL reached puberty at a lighter weight than gilts that received ETH in Exp. 1 (95.6 +/- 2.1 vs 112.4 +/- 3.9 kg; P less than .01) and Exp. 2 (88.1 +/- 1.5 vs 96.0 +/- 1.8 kg; P less than .01). Serum concentrations of LH and FSH, length of estrous cycles, and percentage of muscle of carcasses were similar between MEL and ETH gilts.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

2.
The effect of adrenal function and flumethasone (FM, a synthetic glucocorticoid) on induction of puberty in crossbred gilts raised in confinement was examined in two experiments. In Exp. 1, gilts were adrenalectomized (Adx) or subjected to sham adrenalectomy (Sham) between 140 and 160 d of age. Twenty days later indwelling jugular catheters were implanted in Adx, Sham and another group of intact gilts designated as Controls, and the gilts were moved from confinement to outdoor pens and checked daily for estrus with a mature boar. Fewer (P less than .05) Adx (1/11) than Sham (9/14) gilts showed estrus and ovulated by 205 d of age. Response of Control gilts (6/14) was not different from the other groups. Although Adx gilts received 40 mg cortisone acetate and 10 mg deoxycorticosterone acetate daily throughout the experiment, mean plasma glucocorticoids were lower (P less than .05) in Adx (24 +/- 4.7 ng/ml) than in either Sham (47 +/- 8.1 ng/ml) or Control (44 +/- 6.1 ng/ml) gilts. Experiment 2 was conducted to determine whether FM given to Adx gilts immediately after surgery could have inhibited estrus and ovulation. Intact gilts received a total of 27.5 (FM1) or 17.5 (FM2) mg FM over 4 d between 150 and 160 d of age before relocation and boar exposure 20 d later. Control gilts received no injections. Nine of 13 FM-treated but none of the Control gilts showed estrus. It is concluded from these results that the adrenal glands may facilitate the onset of puberty in gilts through increases in glucocorticoid production, but that this is not required for puberty to occur.  相似文献   

3.
Ewes selected for fertility in autumn lambing were used to evaluate correlated responses in nocturnal hormone levels. Four jugular blood samples were obtained during nighttime in August from each of 113 selected and 69 control ewes. Melatonin levels were lower for selected ewes (143 +/- 14 pg/mL) than for control ewes (184 +/- 13 pg/mL), and melatonin levels decreased with increases in estimated breeding values (EBV) for fertility (-2.23 +/- 0.79 pg mL(-1) x %(-1)). Prolactin levels were higher for selected ewes (90 +/- 7 ng/mL) than for control ewes (52 +/- 7 ng/mL), but significant line x ewe age interaction was also observed, with smaller differences in prolactin levels in 2-yr-old and older ewes (74 +/- 7 vs. 56 +/- 9 ng/mL for select and control ewes, respectively; P < 0.20 before and P = 0.05 after logarithmic transformation). Prolactin levels increased with both fertility EBV (1.23 +/- 0.53 ng mL(-1) x %(-1)) and maternal birth weight EBV (9.0 +/- 4.0 ng x ml(-1) kg(-1)). Heritability estimates were 0.43 (P < 0.02) for melatonin levels and 0.11 (P > 0.25) for prolactin levels. Thus, we conclude that selection for fertility in autumn lambing has affected patterns of melatonin and prolactin secretion during the dark phase.  相似文献   

4.
The objective of this study was to determine the effects of recombinant porcine somatotropin (rpST) treatment during the finishing phase on subsequent reproductive function in crossbred gilts. Forty gilts weighing 50 kg and housed in a swine finishing facility were randomly assigned to control or rpST treatment. Four control and four rpST-treated gilts were allotted per pen. Twenty rpST-treated gilts received 6 mg of rpST.gilt-1.d-1 in 1 ml of buffered carrier and 20 control gilts received 1 ml of buffered carrier.gilt-1.d-1. Injections were administered daily at 1400 in the extensor muscle of the neck. All gilts received an 18% CP diet containing 1.2% lysine. Treatment was terminated when the average weight in each pen reached 110 kg. Gilts treated with rpST gained more weight (P less than .05) than control gilts (59.8 +/- 1.0 vs 53.5 +/- 1.0 kg). Age at puberty was not different (rpST, 182.2 +/- 3.3; control 181.4 +/- 3.1 d). Prior treatment with rpST did not significantly affect length of estrus (rpST, 1.9 +/- .1; control, 1.8 +/- .1 d) or estrous cycle length (rpST, 20.6 +/- .4; control, 20.4 +/- .4 d). Ovulation rates at second estrus were similar for rpST gilts (15.1 +/- .5) and control gilts (14.4 +/- .5). More embryos (P = .10) were recovered on d 9 to 12 of gestation from rpST-treated gilts than from control gilts (13.1 +/- .9 vs 10.7 +/- .9).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5.
To test the hypothesis that the parathyroid hormone (PTH) response to hypercalcaemia is influenced by circadian rhythms, the Ca2+ -PTH curve was studied in six dogs after infusion of CaCl2 (0.66 mEq/kg/h) at daytime (09:00 h) and at night-time (21:00 h). Plasma Ca2+ and PTH values measured before or after CaCl2 infusion were not different at day and at night. However, in the recovery from hypercalcaemia, PTH concentrations were significantly lower (P < 0.05) at 21:00 h (23 +/- 7.5 pg/ml at Ca2+ = 1.30 mm) than at 09:00 h (38.8 +/- 6.9 pg/ml at Ca2+ = 1.30 mm). In addition, the Ca2+ -PTH curve showed hysteresis at daytime (for the same Ca2+ concentration, PTH values were higher during recovery than during induction of hypercalcaemia) but not at night-time (PTH values were lower during recovery than during induction of hypercalcaemia). In conclusion, a circadian variation in the PTH secretory pattern during recovery from hypercalcaemia has been identified in dogs.  相似文献   

6.
Two experiments were conducted to evaluate the effects of the immunization of gilts against ovarian steroids on ovulation rate and litter size. In Exp. 1, gilts (n = five gilts/treatment) at 165+/-1.6 d of age were immunized against either carrier (Control), androstenedione, or 17alpha-hydroxyprogesterone. Age at puberty and estrous cycle length averaged 208+/-5.5 (P = 0.67) and 20.3+/-2.8 d (P = 0.41), respectively, and were not affected by treatment. The androstenedione- and 17alpha-hydroxyprogesterone immunized gilts had higher (P < 0.02) ovulation rates than Controls (14.2, 14.2, and 11.4+/-0.8, respectively). Total pigs born (P = 0.66) and pigs born live (P = 0.65) for the androstenedione-treated group were not different from Controls. Gestation length was not different (P = 0.36) between any of the treatments and the Controls (115+/-0.9 d). Procedures used in Exp. 2 were similar to those in Exp. 1, except that only Control (n= 18) and 17alpha-hydroxyprogesterone (n = 16) treatments were included and only litter size at farrowing was measured. Total pigs and pigs born live were higher in the 17a-hydroxyprogesterone-treated gilts than in the Controls (12.6 vs 10.5+/-0.6, P < 0.02; and 11.4 vs 9.2+/-0.6; P < 0.01, respectively). Data from this study indicate that litter size in gilts can be increased by immunization against 17alpha-hydroxyprogesterone.  相似文献   

7.
Hormones within the somatotropin cascade influence several physiological traits, including growth and reproduction. Active immunization against growth hormone-releasing factor (GRFi) initiated at 3 or 6 mo of age decreased weight gain, increased deposition of fat, and delayed puberty in heifers. Two experiments were conducted to investigate the effects of GRFi on puberty and subsequent ovulation rate in gilts. Crossbred gilts were actively immunized against GRF-(1-29)-(Gly)2-Cys-NH2 conjugated to human serum albumin (GRFi) or against human serum albumin alone (HSAi). In Exp. 1, gilts were immunized against GRF (n = 12) or HSA (n = 12) at 92 +/- 1 d of age. At 191 d of age, antibody titers against GRF were greater (P < .05) in GRFi (55.5 +/- 1.3%) than in HSAi (.4 +/- 2%) gilts. The GRFi decreased (P < .05) BW (86 +/- 3 vs 104 +/- 3 kg) by 181 d of age and increased (P < .05) backfat depth (15.7 +/- .4 vs 14.8 +/- .4 mm) by 130 d of age. At 181 d of age, GRFi reduced the frequency of ST release (1.0 +/- .5 vs 5.0 +/- .5, peaks/24 h; P < .0001) and decreased (P < .01) ST (1.1 +/- .06 vs 1.7 +/- .06 ng/mL), IGF-I (29 +/- 2 vs 107 +/- 2 ng/mL), and insulin concentrations (3.5 +/- .2 vs 6.3 +/- .2 ng/mL). The GRFi decreased (P < .05) feed conversion efficiency but did not alter age at puberty (GRFi = 199 +/- 5 d vs HSAi = 202 +/- 5 d) or ovulation rate after second estrus (GRFi = 10.7 +/- .4 vs HSAi = 11.8 +/- .5). In Exp. 2, gilts were immunized against GRF (n = 35) or HSA (n = 35) at 35 +/- 1 d of age. The GRFi at 35 d of age did not alter the number of surface follicles or uterine weight between 93 and 102 d of age, but GRFi decreased (P < .05) ovarian weight (.41 +/- .08 vs 1.58 +/- .4 g) and uterine length (17.2 +/- 1.1 vs 25.3 +/- 2.3 cm). Immunization against GRF reduced (P < .05) serum IGF-I (GRFi = 50 +/- 4 vs HSAi = 137 +/- 4 ng/mL) and BW (GRFi = 71 +/- 3 vs HSAi = 105 +/- 3 kg) and increased (P < .05) backfat depth (GRFi = .38 +/- .03 vs HSAi = .25 +/- .02 mm/kg). Age at puberty was similar in GRFi and HSAi gilts, but ovulation rate was lower (P < .05) after third estrus in GRFi (11.3 +/- .8) than in HSAi (13.8 +/- .8) gilts. Thus, GRFi at 92 or 35 d of age decreased serum ST, IGF-I, and BW in prepubertal gilts without altering age of puberty. However, GRFi at 35 d of age, but not 92 d of age, decreased ovulation rate. These results indicate that alterations in the somatotropic axis at 1 mo of age can influence reproductive development in pubertal gilts.  相似文献   

8.
Gilts bred at first (n = 18) and third (n = 18) estrus were assigned in replicates of equal numbers to be slaughtered on d 3, 15 and 30 post-mating to assess fertilization rate, embryonic losses and serum concentrations of estrogen (estradiol-17 beta + estrone) and progesterone. Mean number of ovulations was lower among gilts bred at first vs third estrus (12.2 vs 14.5; P less than .05), with no difference in fertilization rate (100 vs 98%). Embryonic survival was lower (P less than .05) among gilts bred at first vs third estrus on d 15 (78.1 vs 95.4%) and 30 (66.7 vs 89.4%) of gestation. Serum estrogen (pg/ml) and progesterone (ng/ml) levels, although lower in gilts bred at first vs third estrus, were not significantly different at the three stages of gestation studied. The ratio of progesterone to estrogen in gilts bred at first estrus was higher than in those bred at third estrus on d 15 (439 +/- 71 vs 210 +/- 17) and 30 (597 +/- 106 vs 179 +/- 50), but was lower on d 3 (187 +/- 37 vs 444 +/- 123; stage of gestation X estrous period interaction, P less than .05). These data suggest that changes in the ratio of systemic levels of estrogen and progesterone may be related to early embryonic mortality in gilts bred at pubertal estrus.  相似文献   

9.
Five adult pasture-bred French Friesian cows were used to qualify the circadian profile and characterized pulsatility of plasma melatonin, and to estimate melatonin secretion rate, around the summer solstice. Plasma concentrations of melatonin were low (5 pg/ml) during the photophase, began to rise at sunset (light intensity less than 20 lx) and reached a maximum (about 90 pg/ml) in the middle of the scotophase. The mean amplitude of peaks was 48.67 +/- 23.01 pg/ml, their mean duration was 32.30 +/- 21.50 min and the frequency was 1.5 +/- 0.3 peak/hr during the secretory period (537 +/- 42.3 min). The plasma clearance (ClB) was 0.0247 +/- 0.0013 1/kg per min, the steady state volume of distribution (Vss) was 1.404 +/- 0.225 1/kg, the elimination half life (t1/2 beta) was 66.66 +/- 11.30 min, the mean residence time was 51.37 +/- 9.92 min and the mean production rate was 399.9 +/- 57.37 ng/kg per 24 hr. These results support the concept of linearity for melatonin kinetics in cattle and the plasma clearance value suggest a first-pass hepatic effect.  相似文献   

10.
To determine whether pituitary concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH) or hypothalamic content of gonadotropin releasing hormone (GnRH) change before puberty, 40 prepubertal gilts averaging 7 mo of age were slaughtered before or on the second, third or fourth day after relocation and boar exposure. Some gilts responded to relocation and boar exposure as indicated by swollen vulvae, turgid uteri and enlarged ovarian follicles at the time of slaughter. Pituitary concentrations of LH and FSH and hypothalamic content of GnRH were similar between gilts that responded to relocation and boar exposure and gilts that did not respond. In addition, boar exposure and relocation had no effect on pituitary concentrations of LH and FSH or on hypothalamic content of GnRH. To determine whether pituitary responsiveness to GnRH changes before puberty, a third experiment was conducted in which 72 gilts were injected with 400 micrograms of GnRH either before or on the second, third or fourth day after relocation and boar exposure. In gilts that subsequently responded (i.e., ovulated) as a result of relocation and boar exposure, pituitary responsiveness to GnRH was reduced as compared with gilts that failed to ovulate after relocation and boar exposure. Peak concentrations of serum LH after GnRH injection were 4.6 +/- 1.3 vs 9.8 +/- .8 ng/ml for responders vs nonresponders. Peak serum FSH after GnRH injection was also lower for responders than for nonresponders (29.5 +/- 4.2 vs 41.2 +/- 2.4 ng/ml). When compared with controls, relocation and boar exposure did not significantly affect GnRH-induced release of LH and FSH.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

11.
Two experiments (EXP) were conducted to determine the roles of age, weight and estradiol (E) treatment on serum leptin concentrations and leptin gene expression. In EXP I, jugular blood samples were collected from gilts at 42 to 49 (n = 8), 105 to 112 (n = 8) and 140 to 154 (n = 8) d of age. Serum leptin concentrations increased (P < 0.05) with age and averaged 0.66, 2.7, and 3.0 ng/ml (pooled SE 0.21) for the 42- to 49-, 105- to 112-, and 140- to 154-d-old gilts, respectively. In EXP II, RNase protection assays were used to assess leptin mRNA in adipose tissue of ovariectomized gilts at 90 (n = 12), 150 (n = 11) or 210 (n = 12) d of age. Six pigs from each age group received estradiol (E) osmotic pump implants and the remaining animals received vehicle control implants (C; Day 0). On Day 7, back fat and blood samples were collected. Estradiol treatment resulted in greater (P < 0.05) serum E levels in E (9 +/- 1 pg/ml) than C (3 +/- 1 pg/ml) pigs. Serum leptin concentrations were not affected by age, nor E treatment. Leptin mRNA expression was not increased by age in C pigs nor by F in 90- and 150-d-old pigs. However, by 210 d of age, leptin mRNA expression was 2.5-fold greater (P < 0.01) in E-treated pigs compared to C animals. Serum insulin concentrations were similar between treatments for 210-d-old pigs. However, insulin concentrations were greater (P < 0.05) in E than C pigs at 90 d and greater in C than E animals at 150 d. Plasma glucose and serum insulin-like growth factor-I concentrations were not influenced by treatment. These results demonstrate that serum leptin concentrations increased with age and E-induced leptin mRNA expression is age- and weight-dependent.  相似文献   

12.
Seasonally anestrous Suffolk ewes (n = 28) were randomly divided into 5 groups and treated with varying doses of melatonin as follows; Groups C (n = 4), M1 (n = 6), M2 (n = 6), M3 (n = 6), M4 (n = 6) of ewes were fed pellets containing 0, 1, 2, 3 and 4 mg melatonin, respectively, daily for 60 days from May 17 (Day 0). Following feeding of the pellets at 13.00 hr plasma levels of melatonin rapidly increased reaching the peak values within 30 min, which ranged from 92.0 to 292.7 pg/ml and were highly correlated with the dose of melatonin administered (r = 0.986, P less than 0.01). Maximum dose of melatonin (4 mg) produced an increase of plasma melatonin similar in magnitude to nocturnal peaks of endogenous secretion. The onset of ovulatory cyclicity, assessed from plasma progesterone profiles, was advanced by melatonin administration. The mean +/- SEM intervals from the commencement of melatonin treatment until the onset of ovulatory cyclicity were 53.0 +/- 5.8, 53.6 +/- 2.5, 42.0 +/- 5.6 and 44.3 +/- 4.3 days for the Groups M1, M2, M3 and M4, respectively, which were shorter (M1, P less than 0.05; M2, M3 & M4, P less than 0.01) than that for the Group C (72.5 +/- 1.4 days). The melatonin treatment also suppressed, in a dose related manner, the rise in plasma prolactin under the lengthening photoperiod. We conclude that the dose-related efficacy of melatonin could be ascribed to the difference in the diurnal profiles of circulating melatonin.  相似文献   

13.
One-hundred-twenty crossbred gilts from two experiments were assigned randomly to a 2 X 5 factorial experiment. Gilts were reared in two environments (confinement or outside) and assigned to be slaughtered at 4, 5, 6, 7 or 8 mo of age. Beginning at 6 mo of age, blood samples were taken at weekly intervals from each gilt via venipuncture. Serum concentrations of progesterone were analyzed to determine when gilts attained puberty. On the day prior to slaughter, six pigs within a treatment group were cannulated and blood samples were taken at 20-min intervals for 4 h. At slaughter, follicular fluid (FF) was aspirated and the volume determined from those follicles having a diameter of at least 4 mm. No effect of environment was found on the proportion of gilts that attained puberty by 8 mo of age. For the 12 gilts that reached puberty during the study, the age at puberty for gilts reared in outdoor lots (202 +/- 5 d) was less (P less than .05) than those reared in confinement (224 +/- 8 d). Mean concentrations of serum luteinizing hormone (LH; P = 98) and number of secretory spikes of LH (P = .76) were similar between gilts reared in confinement and those reared in outdoor lots. No differences in average serum concentrations of follicle stimulating hormone (FSH) or number of secretory spikes of FSH were found between gilts subjected to these environments (P = .95). Concentrations of estradiol-17 beta in FF were not affected by environment or age (P greater than .25).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

14.
This study was designed to examine the effects of two seasons and stage of gestation on luteinizing hormone (LH) release in the gilt. Eleven Yorkshire-Landrace crossbred gilts were each fitted with an indwelling vena caval cannula. Blood samples were collected at 6 h intervals for six days during early (day 39 to 44) or mid-gestation (day 69 to 74). Serum progesterone, estradiol-17 beta and LH concentrations were determined in samples collected at 6 h intervals. Early and mid-gestation occurred during August and September in group 1 (n = 6) and during January and February in group 2 gilts (n = 5). To characterize pulsatile LH release, samples were collected at 15 min intervals for 8 h on day 40, 43, 70 and 73 of gestation. Following each 8 h sampling period, gilts were treated intravenously with 0.5 micrograms gonadotropin-releasing hormone (GnRH)/kg body weight and blood collected at 10 min intervals for 3 h. Progesterone concentrations decreased (p less than 0.01) from 22.1 +/- 0.4 ng/mL during early gestation to 18.2 +/- 0.4 ng/mL during mid-gestation. Estradiol-17 beta concentrations increased (p less than 0.01) from early to mid-gestation (13.5 +/- 0.8 versus 28.4 +/- 0.7 pg/mL). Frequency of LH pulses and LH pulse amplitude were higher (p less than 0.05) in pregnant gilts during January and February compared to August and September.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

15.
Forty-eight prepubertal gilts (178.7 +/- 4.1 d; 94.2 +/- 4.1 kg), 16 in each of three trials, were assigned randomly to receive 0 (C) or 10 ppm zearalenone (Z) daily in 2.5 kg of a 14% protein finishing ration for 2 wk. Blood samples were collected at 20-min intervals for 4 h 1 wk after the start of the experiment and 1 wk after Z was withdrawn. Two weeks after Z was withdrawn, gilts were exposed to mature boars 15 min per day for 3 wk. Gilts in estrus were mated to two different boars 12 h apart. Twice each week, blood was sampled and analyzed for progesterone to establish age of puberty. Age at puberty differed (P = .008) among replicates but was similar (P = .13) between Z and C gilts within each replicate. Mean serum concentrations of LH were suppressed (P = .025) during consumption of Z (.25 vs .42 ng/ml) but were similar (P = .16) to concentrations in C gilts 1 wk after Z was withdrawn (.35 vs .45 ng/ml). Frequency and amplitude of LH secretory spikes did not differ (P greater than .50) between Z and C gilts during either sampling period. Mean serum concentrations of FSH were similar (P = .25) between Z and C gilts. Number of corpora lutea and live fetuses were similar (P = .29 and P = .94, respectively) between Z and C gilts. Fetal weights were greater (P = .025) and crown to rump length tended to be greater (P = .10) in fetuses from Z gilts.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

16.
This experiment determined the effect of treatment of 3- to 4-mo-old heifer calves with exogenous melatonin, in early summer, on the attainment of puberty the following spring. Hereford heifers, born between February 22, and March 16, were paired by age and BW and assigned at random within pair to receive an ear implant of melatonin (MEL, n = 12) or to serve as controls (C, n = 12). The implant period was 5 wk, starting June 10 at a mean age of 105 +/- 5 d and 134.4 +/- 3.5 kg BW. Puberty was evaluated the following year on four occasions: January 26, March 19, May 2, and June 1. One each date, rectal palpation of the ovaries was performed, blood samples were taken to assess concentrations of progesterone (P4), and BW was determined. Puberty was considered to have occurred when concentrations of P4 were greater than or equal to .5 ng/mL concomitant with a palpable corpus luteum (CL), or when concentrations of P4 were greater than or equal to 1 ng/mL and a CL was present on the next date. At implant removal, concentrations of melatonin in plasma collected at 1000 to 1400 were 69.5 +/- 6.3 and 16.7 +/- 2.4 pg/mL for MEL and C heifers, respectively. On that and subsequent occasions, neither BW nor ADG differed between MEL and C heifers. Treatment with melatonin increased the incidence of heifers pubertal by the second observation date (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

17.
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   

18.
In an attempt to improve the reproductive performance of gilts mated at puberty, 70 Yorkshire x Landrace gilts were allocated at 120 d of age and 60 kg body weight to one of two treatments. Restricted gilts were fed 2.0 kg d-1 of a diet formulated to provide 18% crude protein and 14.5 MJ DE kg-1 from selection until mated at their first estrus (n = 35). Flushed gilts were fed 2.0 kg d-1 of the same diet from 120 to 150 d of age, but then had their feed intake increased to 3.5 kg d-1 until mated at their first estrus (n = 35). An additional group of gilts (control fed; n = 33) were fed 3.0 kg d-1 from selection until they were bred at their third estrus in order to investigate the influence of feed restriction on the onset of puberty. During gestation all gilts were fed 1.8 to 2.2 kg d-1 of a 16.8% crude protein diet having 13.7 MJ DE kg-1. Control fed gilts were younger (p less than 0.05) at puberty (150 d) than restricted (165 d) or flushed gilts (165 d). There was no difference in subsequent litter size between the restricted and flushed gilts (7.7 and 8.0, respectively). It is concluded that the institution of a flushing nutritional regime in the prepubertal period will not enhance piglet production from gilts mated at puberty.  相似文献   

19.
The aim of the study was to assess the effect of subacute treatment with a low dose of atrazine (1,3,5-triazine-2,4-diamine, 6-chloro-N-ethyl-N'-(1-methyl-ethyl), an s-triazine herbicide, on endocrine oestrus regulation in gilts. A group of nine gilts (F1 generation of Swedish Landrace x Large Yorkshire) were treated with 1 mg atrazine/kg body mass daily, mixed to the feed for 19 days before the onset of expected oestrus. Blood samples were obtained by cranial vena cava puncture three times daily at 3-h intervals on five post-treatment days, i.e. before and during oestrus. The serum concentration of oestradiol-17 beta (E2) was determined by the fluoroimmunochemical method. On Day -2 before the onset of expected oestrus, a significantly lower (P < 0.001) E2 concentration was measured in the serum of treated gilts (31.25 +/- 1.95 and 39.32 +/- 1.38 pg/mL) than in the control pigs (51.43 +/- 1.29 and 68.59 +/- 2.99 pg/mL). In contrast, the E2 concentration measured in the serum of treated animals was significantly higher (P < 0.001) on the day of the expected onset of oestrus and on the subsequent two days (35.43 +/- 1.85, 53.92 +/- 1.98 and 60.32 +/- 2.35 pg/mL, respectively) than in the control animals (13.52 +/- 1.79, 21.53 +/- 1.35 and 20.05 +/- 1.46 pg/mL, respectively). Insufficient serum E2 concentration of the treated gilts resulted in a failure of expected oestrus, as indicated also by the state of dioestrus demonstrated by histopathological examination of the uterus.  相似文献   

20.
The objective of this study was to determine plasma concentrations of luteinizing hormone (LH), progesterone (P4) and estradiol-17beta (E2) in Mangalica gilts (M), a Hungarian native breed, and compare them with Landrace gilts (L) during the peri- and post-ovulatory periods. The estrous cycle of gilts was synchronised by Regumate feeding, and ovulation was induced with a gonadotropin-releasing hormone (GnRH) agonist. Blood sampling was carried out via indwelling jugular catheters three times a day and in 2-h intervals during a 16-h period after the GnRH application. The concentrations of LH, E2 and P4 were determined by immunoassays. Gilts of both breeds showed a typical gonadotropin and gonadal hormone secretion pattern. Preovulatory E2 peaks were observed on day 2 (M) and day 4 (L) after the last Regumate feeding. Highest E2 concentration was different between M and L breeds (46.5 +/- 5.7 vs. 26.0 +/- 6.8 pg/ml, P < 0.05). Maximum LH levels measured up to 6 h after GnRH were not different between M and L breeds (11.5 +/- 4.1 vs. 6.6 +/- 2.3 ng/ml). Both LH amounts during surge (41.1 +/- 15.9 vs. 27.5 +/- 6.1 ng/ml) and total over LH release (73.4 +/- 22.2 vs. 50.0 +/- 8.7 ng/ml) did not differ significantly between M and L breeds. P4 concentrations started to rise on day 6 after Regumate feeding and increased significantly from 0.6 +/- 0.3 and 0.7 +/- 0.4 ng/ml to maximal 14.0 +/- 2.4 and 11.3 +/- 2.1 ng/ml in M and L breeds, respectively. Mean P4 secretion was higher in M on days 10-15 (12.9 +/- 2.6 vs. 9.3 +/- 2.2 ng/ml; P<0.05). At the same time the number of corpora lutea was lower in M compared to L (10.3 +/-1.5 vs. 17.8 +/- 5.0, P<0.05). In our experiment, there was no evidence that differences in the secretion of analysed hormones during the peri- and post-ovulatory periods are a possible cause of usually lower fecundity in Mangalica gilts.  相似文献   

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