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1.
The effects of acute nutritional change on endocrine and ovarian characteristics were studied in cyclic (intact; n = 20) and long-term ovariectomized (ovx; n = 18) heifers being fed 1.2 x maintenance (1.2M). On d 7 of an 8-d progesterone and estradiol treatment, intact and ovx heifers were randomly allocated to diets providing .4, 1.2, or 2.0M until emergence of the second follicular wave after ovulation in intact heifers. In intact heifers, two of eight fed .4M failed to ovulate. In the other six, growth rate and maximum diameter (1.1+/-.09 mm/d and 10.1+/-.7 mm, respectively) of the first dominant follicle (DF) postovulation were less (P<.05) than in heifers fed either 1.2 (1.6+/-.18 mm/d; 12.9+/-.44 mm) or 2.0M (1.6+/-.08 mm/d; 12.7+/-.7 mm). In intact heifers, LH pulse frequency and amplitude were not affected by diet (P>.10). In ovx heifers, the frequency of LH pulses was unaffected by diet (P>.10), but heifers fed .4M had a greater pulse amplitude (P<.05) and mean concentration of LH (P<.001) than those fed 1.2 or 2.0M. Plasma concentrations of FSH were greater (P<.05) in ovx heifers fed .4M than in those fed 1.2 or 2.0M and increased linearly with time (P<.01). The FSH concentrations in heifers fed 1.2 and 2.0M were similar (P>.10) and decreased linearly with time (P<.001). In intact heifers, concentrations of FSH preceding follicle wave emergence were greater in heifers fed .4M (P<.001), but basal concentrations were not affected (P>.10). Concentrations of progesterone and estradiol were unaffected by diet (P>.10). Significant diet x ovarian status interactions in plasma IGF-I concentrations existed. Plasma concentrations of insulin increased as the level of nutrition increased, whereas concentrations of NEFA decreased. In conclusion, growth rate and maximum diameter of the DF were decreased by acute nutritional restriction, without affecting the concentration of LH. The magnitude of the FSH increase preceding new follicle wave emergence increased following dietary restriction, but concentrations of FSH were unaffected during the other stages of DF growth. The results of this study may have important implications for the feeding strategies adapted for high-yielding dairy cows in the early postpartum period when feed intake is often physiologically restricted.  相似文献   

2.
This study was designed to test the effects of active immunization against estrogen and progesterone on patterns of luteinizing hormone (LH) and follicle stimulating hormone (FSH) secretion, ovarian characteristics and growth rate of heifers. Heifers were randomly assigned to four treatments: 1) control injection (n = 10); 2) ovariectomy (n = 9); 3) immunization against estrogen (anti-E, n = 10); and 4) immunization against estrogen and progesterone (anti-E+P4, n = 10). Three booster immunizations were administered at 1, 1.5 and 6 mo after primary immunization. Progesterone antibody binding was 40% (34 fmol at 1:600 final dilution) in the anti-E+P4 heifers, and estradiol-17 beta binding was 35% (30 fmol) and 60% (52 fmol at 1:100 final dilution) in the anti-E+P4 and anti-E heifers, respectively, after the final immunization. Anti-E+P4 heifers had more pulses of LH and higher basal concentrations of LH than anti-E or control heifers (P less than .05). Concentrations of LH in anti-E+P4 heifers did not increase to concentrations found in ovariectomized heifers (P less than .05). Immunization against steroids did not alter the secretion of FSH. The number of large follicles (greater than 15 mm diameter) in anti-E+P4 and anti-E heifers was greater than in control heifers (P less than .05). Ovarian weight was increased in anti-E+P4 heifers (P less than .05). Average daily gain was not different among groups (P greater than .05). It was concluded that active immunization against estrogen and progesterone in heifers increased LH secretion and stimulated ovarian function.  相似文献   

3.
In vitro blastocyst production was determined for oocytes recovered postmortem from 48 beef x dairy heifers offered low (Low NH3) or high (High NH3) plasma ammonia-generating diets during the period of late antral follicle development. Following the establishment of a reference estrus (d 0), the experimental diets were offered for an 18-d period starting on d 3 and during which a second estrus was induced (d 16) 4 d before the animals were slaughtered. Blood samples collected at varying intervals were analyzed for ammonia, urea, progesterone, and LH. Ovarian folliculogenesis was monitored daily by transrectal ultrasonography. Ovaries were collected at slaughter and cumulus-oocyte complexes were aspirated from small (1 to 4 mm) and medium-sized (> 4 to 8 mm) sized follicles. In vitro-matured and -fertilized putative d-1 zygotes were cultured for a further 7 d in vitro and embryo development and metabolism were assessed. Relative to the low-NH3-generating diet, the high-NH3-generating diet increased peak postprandial levels of plasma ammonia (326.1 +/- 43.3 vs 52.1 +/- 7.4 micromol/L; P < .001), mean levels of plasma urea (7.0 vs 5.7 mmol/L; SED = .2; P < .001), peak levels of plasma progesterone prior to induced luteolysis (8.9 +/- .4 vs 6.8 +/- .3 microg/L; P < .001), and follicular fluid levels of ammonia (267 +/- 18 vs 205 +/- 20 nmol/mL; P < .05) and progesterone (351 +/- 69 vs 199 +/- 26 ng/mL; P < .05). The timing and level of the preovulatory LH surge was not affected by dietary treatment. Of oocytes cultured, cleavage (47.4 vs 62.4%; P = .02) and blastocyst production (10.9 vs 20.6%; P = .06) rates were reduced when the oocytes were derived from heifers offered the high- rather than the low-NH3-generating diets. There were interactions between dietary treatment and follicle size class, which indicated that fewer blastocysts were produced from cleaved oocytes derived from medium-sized follicles of heifers offered the high-NH3 treatment but that de novo protein synthesis was increased in such embryos. In conclusion, exposure to high levels of ammonia and(or) urea in vivo can significantly compromise the subsequent capacity of oocytes to develop to blastocysts in vitro, and oocytes recovered from medium-sized follicles are particularly sensitive to this effect.  相似文献   

4.
Experiments were performed to determine whether serum concentrations of total cholesterol (TC) undergo cyclic changes during the estrous cycle of dairy heifers and to assess the relationship between serum concentrations of TC and ovarian steroid hormones. The effects of a hypercholesterolemic diet upon luteal progesterone secretion also were determined. Experiment 1 involved five dairy heifers exhibiting normal estrous cycles. Serum concentrations of TC, progesterone, testosterone and estradiol-17 beta were determined in blood samples collected throughout a complete estrous cycle. A transient decline in TC was observed during the luteal phase of all heifers beginning on d 2 and reached a nadir 6 d after estrus. Highest mean concentrations of TC occurred between d -2 and +2 (96.3 +/- 8.2 mg/dl), which were markedly higher (P less than .05) than the lowest mean concentrations (76.3 +/- 10.3 mg/dl) observed on d 6. Concentrations of serum TC were negatively correlated (r = -.40; P less than .01) with progesterone between d 2 and 9. Serum TC was not correlated with testosterone or estradiol-17 beta. In Exp. 2, seven cycling Holstein heifers were fed a control diet for 70 d (Stage I), a diet containing 15% whole sunflower seed as a source of supplemental dietary lipid for 70 d (Stage II) and then the control diet for 70 d (Stage III). Diets were isocaloric and isonitrogenous. All heifers were synchronized with prostaglandin F2 alpha after wk 5 in each of the three feeding stages.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5.
To determine whether long-term administration of growth hormone (GH)-releasing factor (GRF) and(or) thyrotropin-releasing hormone (TRH) alters ovarian follicular fluid (FFL) concentrations of insulin-like growth factor-I (IGF-I), progesterone, and estradiol (E2), and follicular growth, Friesian x Hereford heifers (n = 47; 346 +/- 3 kg) were divided into the following four groups: control (vehicle; n = 11); 1 micrograms GRF (human [Des NH2 Tyr1, D-Ala2, Ala15] GRF [1-29]-NH2).kg-1 BW.d-1 (n = 12); 1 microgram TRH.kg-1 BW.d-1 (n = 12); or GRF + TRH (n = 12). Daily injections (s.c.) continued for 86 d. On d 89, heifers that had been synchronized were slaughtered and ovaries were removed. Follicles were grouped by magnitude of diameter into the three following sizes: 1 to 3.9 mm (small, n = 55), 4.0 to 7.9 mm (medium, n = 63), and greater than or equal to 8 mm (large, n = 71). Growth hormone-releasing factor and(or) TRH did not affect (P greater than .10) IGF-I concentrations in FFL of any follicle size group. Growth hormone-releasing factor increased (P less than .06) size (means +/- pooled SE) of large follicles (14.7 vs 13.0 +/- .6 mm). Growth hormone-releasing factor also increased (P less than .05) progesterone concentrations 4.4-fold above controls in FFL of medium-sized follicles but had no effect on progesterone in FFL of the small or large follicles. Thyrotropin-releasing hormone did not alter FFL progesterone or E2 concentrations in any follicle size group. We conclude that the GRF and(or) TRH treatments we employed did not affect intra-ovarian IGF-I concentrations, but GRF may alter steroidogenesis of medium-sized follicles and growth of large follicles.  相似文献   

6.
Primiparous sows (n = 36) were used to evaluate the effects of dietary lysine intake in lactation on follicular development and oocyte maturation after weaning. Sows were assigned randomly to one of three diets containing .4% (low lysine, LL), 1.0% (medium lysine, ML), or 1.6% (high lysine, HL) total lysine. All diets contained 2.1 Mcal NE/kg and exceeded NRC (1988) requirements for all other nutrients. Actual lysine intakes over an 18-d lactation were 16, 36, and 56 g/d for sows consuming LL, ML, and HL, respectively. Ovarian data were analyzed for sows determined to have been slaughtered during the first proestrus period after weaning, using previously established criteria. Compared with sows fed ML and HL, sows fed LL tended to have lower uterine weight, follicular fluid volume, and follicular fluid (FF) estradiol (E2) content (P < .15), but similar ovarian weight and follicular fluid IGF-I concentration. Within the largest 15 preovulatory follicles, sows fed LL had a lower percentage of large (> or = 7.0 mm) follicles (33 vs 50 and 58%; P < .01) and a higher percentage of medium (5.5 to 7.0 mm) follicles (62 vs 44 and 39%; P < .01) but a similar percentage of small (< or = 5.5 mm) follicles (4.4 vs 5.9 and 3.7%; P > .15), respectively, compared with sows fed ML or HL. Standardized pools of oocytes aspirated from follicles of prepubertal gilts were incubated for 44 h with pooled FF recovered from the largest 15 follicles of each experimental sow. Fewer oocyte nuclei matured to metaphase II of meiosis when cultured with FF recovered from sows fed LL, than from sows fed ML or HL (47.1 vs 59.8 and 63.8%, respectively; P < .01). Our results suggest that low lysine (protein) intake in primiparous lactating sows impaired follicular development and reduced the ability of follicles to support oocyte maturation. However, high compared with medium lysine (protein) intake had no further positive effects on ovarian function.  相似文献   

7.
A study was conducted to determine the effect of charcoal-extracted, bovine follicular fluid (CFF) on plasma follicle stimulating hormone (FSH) and luteinizing hormone (LH) concentrations, the interval from luteolysis to estrus, and subsequent luteal function in heifers. Fifteen Angus, Simmental and Hereford heifers were allotted by age, weight and breed to a control (C, n = 8) or a CFF (n = 7) group. Heifers received injections of saline or CFF (iv, 8 ml/injection) every 12 h from d 1 (d 0 estrus) through d 5 of the estrous cycle. On d 6, each heifer was injected (im) with 25 mg of prostaglandin F2 alpha (PGF2 alpha). Blood samples were collected every 12 h by venipuncture starting just before the first saline or CFF injection and continuing until estrus. Thereafter, blood samples were collected every other day during the subsequent estrous cycle and assayed for FSH, LH, estradiol-17 beta and progesterone by radioimmunoassay. Injections of CFF had no effect (P greater than .05) on circulating FSH or LH concentrations from d 1 to 5 relative to the C group; however, there was a transient rise (P less than .05) in FSH concentrations 24 h following cessation of CFF injections. This transient rise in FSH was not immediately followed by an increase in plasma estradiol-17 beta concentrations. Although CFF injections did not interfere with PGF2 alpha-induced luteolysis, the interval from PGF2 alpha injection to estrus was delayed (P less than .05) by 5 d in the CFF group compared with the C group.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

8.
To determine influences of insulin and body condition on follicular growth, prepuberal gilts (n = 16) treated with pregnant mare's serum gonadotropin (PMSG) were used in a 2 X 2 factorial experiment with main effects of insulin (0 or .4 IU/kg every 12 h beginning at 1800 on the day before PMSG) and backfat depth (moderate, 25 +/- .8; high, 32 +/- .7 mm; P less than .0001). Body weights were similar. Blood sampling was at 6-h intervals for analyses of LH, FSH, growth hormone (GH), glucagon, cortisol, insulin, insulin-like growth factor-I (IGF-I), plasma urea nitrogen (PUN), nonesterified fatty acids (NEFA), testosterone, estradiol-17 beta, and progesterone. Ovaries were removed 75 h after PMSG treatment, and visible small (less than or equal to 3 mm), medium (4 to 6 mm), large (greater than or equal to 7 mm), and macroscopically atretic follicles were counted. Administration of insulin increased IGF-I in fluid of medium follicles (108.8 vs 60.7 ng/ml; SEM = 13.3; P less than .05). Neither insulin nor fatness affected hCG binding by granulosa cells (12.5 +/- 1.6 ng/10(6) cells) or numbers of large (16.7 +/- 2.6) and medium (10.4 +/- 2.3) follicles. However, insulin increased the number of small follicles (58.9 vs 29.9; SEM = 9.7; P less than .05) and reduced the number of atretic follicles (3.8 vs 11.3; SEM = 1.1; P less than .05). The predominant effect of insulin on reducing number of atretic follicles was in the small size class (.6 vs 6.9; SEM = .6, P less than .01). Follicular fluid estradiol and progesterone were not affected by treatments; however, testosterone concentrations in large follicles were lower in gilts with higher backfat (32.5 vs 59.9 ng/ml; SEM = 4.0; P less than .05). Systemic LH, FSH, glucagon, cortisol, PUN, NEFA, estradiol, and testosterone were not affected by insulin or level of feeding. However, GH was lower in gilts that had higher backfat (overall average of 3.2 vs 2.8 ng/ml; SEM = .1; P less than .05). Insulin reduced atresia and altered intrafollicular IGF-I independently of body condition and without sustained effects on other hormones.  相似文献   

9.
Our objectives were to determine whether or not ovarian follicles contribute to spontaneous luteal regression in heifers and, if so, when during diestrus do follicles exert their effect. Thirty-one Holstein heifers having displayed at least one estrous cycle (19 to 21 d) were assigned, as available, to randomized blocks for a factorial experiment. Reproductive organs were exposed through a midventral incision on d 9, 12 or 15 postestrus (estrus = d 0). Visible follicles were electrocauterized and both ovaries were x-irradiated (1,500 rads) in treated heifers, whereas ovaries of controls were exteriorized but follicles were not destroyed and ovaries were not x-irradiated. In two additional heifers, the ovary containing the corpus luteum was exteriorized and x-irradiated on d 15 postestrus, but follicles were not electrocauterized. Jugular blood was collected before and every 8 h after surgery until d 24 postestrus. All heifers were ovariectomized on d 24 postestrus to inventory follicles and to weigh corpora lutea. No follicles (greater than or equal to 1 mm diameter) were observed in ovaries from treated animals and concentrations of estradiol-17 beta did not change over time, whereas different numbers of follicles were observed in ovaries from controls and concentrations of estradiol-17 beta increased (P less than .05) during proestrus. Hence, treatment destroyed follicles and prevented follicular development. On d 24 postestrus, corpora lutea from treated heifers (5.5 +/- .5 g) were heavier (P less than .001) than corpora lutea from controls (1.1 +/- .1 g), independent of day when follicles were destroyed.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

10.
To elucidate the effects of ultrasound-guided transvaginal follicular aspiration, plasma concentrations of FSH, LH, inhibin, estradiol-17beta and progesterone, and folliculogenesis were examined in Holstein cows. Four clinically healthy cows with regular estrous cycles were scanned by ultrasound per rectum once a week for 9 weeks before the commencement of follicular aspiration. All visible follicles were divided into 3 categories based on their sizes (2 < or = small < 5 mm; 5 < or = medium < 10 mm, large > or = 10 mm). The follicular aspiration was started at random during the estrous cycle and conducted under epidural anesthesia induced with 5 ml of 2% lidocaine once a week for 6 weeks. The average number of total visible follicles > or = 2 mm in diameter at 7 days after aspiration (21.7 +/- 7.4, n = 24) was similar to that before starting aspiration (26.7 +/- 10.5, n = 36). Plasma inhibin and estradiol-17beta declined and fell to a trough on 1.5 days and returned to pre-aspiration values by 5 days after aspiration. Plasma concentrations of FSH increased and reached peak levels between 1 and 1.5 days after aspirations. Plasma concentrations of LH also increased and reached peak levels between 0.5 and 1.5 days after aspirations. Both plasma FSH and LH had returned to pre-aspiration levels by 5 days after aspirations. Plasma concentrations of progesterone did not change with the follicular aspiration. These results demonstrate that follicular aspiration decreases plasma concentrations of inhibin and estradiol-17beta, which in turn leads to a rise in plasma concentrations of FSH and LH. It is suggested that marked increases in plasma concentrations of FSH and LH after the aspiration stimulate the development and maturation of a new cohort of follicles within one week in cows.  相似文献   

11.
To investigate some biochemical changes during bovine follicle development, ovaries were obtained from cyclic heifers (7 to 11 heifers/d on each day of the 21-d estrous cycle; N = 152). Follicular fluid from the two largest follicles from both ovaries and a pool from small follicles (N = 30/cow) were collected from each animal and analyzed for ionic, enzymatic and endocrine changes in relation to day of the estrous cycle, follicle size, rank and atretic or growing status. Follicular fluid alkaline phosphatase activity and ascorbate concentrations were highest in all follicular sizes during the earlier portion of the estrous cycle (d 1 to 12; P less than .05), then decreased to the lowest levels (d 13 to 21). As follicular size (diameter) increased lactate dehydrogenase (LDH), acid and alkaline phosphatase activity was reduced in follicular fluid (P less than .05). Alkaline phosphatase and LDH activity tended to be increased in atretic follicles (P less than .10), and was correlated with increased progesterone and androgen concentrations of follicular fluid (r = .4, P less than .05). Both albumin and total protein concentrations decreased as follicular diameter increased (P less than .05). Sodium concentrations in follicular fluid were greater in growing-antral than atretic follicles, and increased with follicular enlargement (P less than .05). Follicular potassium concentrations increased as the estrous cycle progressed (P less than .05), and tended to be elevated in atretic follicles (nonsignificant). Both Ca and Mg concentrations increased with follicular enlargement (P less than .05). Dehydroepiandrosterone and testosterone were the predominant androgens in follicular fluid (androstenedione, the lowest concentration); their concentration decreased with follicle development (P less than .05), but were quite variable. Estradiol was increased in growing follicles (P less than .01). Estrone and estradiol concentrations increased as ovulation approached, particularly in small follicles (less than or equal to 4 mm diameter). Changes of biochemical components found in follicular fluid that relate to the growth and atresia process may provide a more sensitive and accurate method to classify follicle status, and thus aid in understanding the complexity of events associated with maturation of the bovine follicle and oocyte.  相似文献   

12.
This study was undertaken to determine changes in follicular populations on ovaries of dairy cows during three stages of the estrous cycle and their steroidogenic capacity in vitro. Numbers of small (2.0 to 5.0 mm), intermediate (5.1 to 10 mm) and large (greater than 10 mm) antral follicles on ovaries of multiparous cows and heifers (n = 31) in the early luteal (d 4), mid-luteal (d 12) and follicular phase (d 19) of the estrous cycle were determined (d 0 = estrus), and steroidogenic capacity of intermediate and large follicles was measured in vitro. Total number of follicles and number of small follicles were greatest (P less than .05) on d 19 compared with d 12, with numbers on d 4 not different from either d 12 or 19. Intermediate follicles were fewer (P less than .05) on d 19 compared with d 4 or 12. Numbers of large follicles did not change. The proportion of estrogen active (EA) follicles was greater (P less than .05) on d 19 compared with d 4 or 12. Accumulation of estradiol-17 beta (E) into culture medium by intermediate follicles decreased (P less than .05) with increasing days of the estrous cycle, while accumulation of progesterone (P) was greater on d 19. In large follicles, accumulation of E into culture medium was greatest (P less than .05) on d 19 and the lowest on d 12 (P less than .05). In summary, the proportion of EA follicles increases during the preovulatory period, and E production increases in large EA follicles.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

13.
The objective of this study was to determine if alterations in dietary intake of heifers can influence IGF-I concentrations in plasma and(or) follicular fluid (FFL), size of follicles, and steroid concentrations in FFL (as an indicator of steroidogenic capacity). Cyclic heifers [n = 23; mean +/- SE body weight (BW) = 373 +/- 7 kg] were individually fed for 10 weeks either: a) 1.8% of BW in dry matter (DM) per d (GAIN; n = 7), b) 1.1% of BW in DM per d (MAINT; n = 8) or c) 0.7% of BW in DM per d (LOSE; n = 8). After 10 wk of treatment, heifers were ovariectomized 36-40 hr after the second injection of prostaglandin F2 alpha analog (2 injections 11 d apart), and plasma and ovaries were collected. Heifers weighed 444 +/- 13,387 +/- 8 and 349 +/- 9 kg in the GAIN, MAINT and LOSE groups, respectively, at time of ovariectomy. Mean diameter of follicles greater than or equal to 10 mm was greater (P less than .05) for GAIN (15.6 mm) than for MAINT (11.0 mm) or LOSE (12.5 mm) heifers. Numbers of follicles and concentrations of IGF-I in plasma and FFL did not differ (P greater than .20) between LOSE, MAINT and GAIN heifers. Progesterone concentrations were greater (P less than .05) in small and medium follicles of GAIN than MAINT or LOSE heifers, but were unaffected by diet in large follicles. Estradiol concentrations in FFL in small, medium and large follicles were unaffected (P greater than .20) by dietary treatment.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

14.
The aim of this study was to evaluate the effect of a dopamine antagonist, domperidone, in nonpregnant, reproductively cycling heifers consuming endophyte-infected (EI) fescue diets. Thirty crossbred heifers (Angus x Holstein or Hereford x Holstein) were assigned to one of three treatment groups (n = 10); endophyte-free (EF) fescue diet, EI fescue diet, or endophyte-infected diet and treated with domperidone (EID). Heifers fed EI diets had decreased weight gains compared with heifers fed EF or EID (P < 0.05) during a 21-d treatment period. Ovarian structures were monitored via transrectal ultrasound to determine follicle size and day of ovulation. Blood plasma samples were collected daily and analyzed for progesterone concentration to determine luteal function. Heifers ingesting EI diets had estrous cycles of shorter duration and lower mid-cycle progesterone concentrations than heifers in the EF or EID treatments (P < 0.05). Ovaries from a subset of heifers in each group (n = 3 per group) were harvested and in vitro secretion of progesterone from luteal tissue extracts was determined. No differences in progesterone concentrations were detected among luteal tissue incubates (P > 0.05). These results suggest that domperidone supplementation of heifers consuming EI fescue may ameliorate certain symptoms of fescue toxicosis.  相似文献   

15.
Precocious puberty can be induced in a majority of heifers weaned early and fed a high-concentrate diet. The objective of this experiment was to determine whether induction of precocious puberty is associated with an acceleration of ovarian maturation in heifers. Crossbred Angus and Simmental heifer calves were weaned at 104 +/- 2 (n = 18; early weaned) or 208 +/- 3 (n = 10; normal-weaned, NW) d of age. The early weaned heifers were fed a high-concentrate (60% corn; EWH, n = 9) or control diet (30% corn; EWC, n = 9). The NW heifers were also fed the control diet after weaning. Daily transrectal ultrasonography was performed to characterize a complete follicular wave beginning at a mean age of 126, 161, 196, 224, and 252 (EWH and EWC), or 224 and 252 (NW) d. Blood samples were collected daily during periods of ultrasonography to determine estradiol concentrations and weekly beginning at mean ages of 153 (EWH and EWC) or 216 (NW) d to be analyzed for progesterone concentrations. Heifers in the EWH treatment were heavier (P < 0.01) than EWC heifers from a mean age of 175 d through the end of the study (treatment x age; P < 0.05). Body weights did not differ between EWC and NW. At mean ages of 196 and 224 d, the maximum diameter of the dominant follicle (MaxDF) was greater (P < 0.05) in EWH than EWC heifers. At a mean age of 224 d, MaxDF was greater (P < 0.05) in EWC than NW heifers but was not different by a mean age of 252 d. All EWH, 5 of 9 EWC, and 5 of 10 NW heifers attained puberty at less than 300 d of age (precocious puberty). Age at puberty was less (P < 0.05) in EWH (252 +/- 9 d) than in EWC and NW (308 +/- 26 and 330 +/- 25 d, respectively) treatments. Across all heifers, MaxDF and duration of follicular waves increased with age (P < 0.05), mean number of follicles during follicular waves decreased with age (P < 0.05), and peak concentrations of estradiol during follicular waves increased until a mean age of 224 d. To further characterize aspects of precocious puberty, heifers were compared across treatments between those that experienced precocious puberty and those that did not. In heifers that experienced precocious puberty, BW at puberty was less (P < 0.01) and MaxDF, follicular wave duration, and peak estradiol concentrations were greater (P < 0.05) compared with heifers that did not experience precocious puberty. Ovarian maturation was accelerated in heifers that were weaned early and fed a high-concentrate diet and was associated with precocious onset of puberty.  相似文献   

16.
Our objective in this study was to determine endocrine responses and changes in ovarian structures after a single injection of a GnRH agonist in Holstein dairy heifers (n = 38). Heifers were inseminated and received (i.m.) either saline or 200 micrograms of fertirelin acetate once on d 11, 12, or 13 after estrus (d 0). Blood was collected at 15- to 30-min intervals for 6 h after the injection to determine concentrations of LH, FSH, estradiol (E), and progesterone (P) in serum and once daily for 8 to 12 d after the injection to determine concentrations of E and P. Pregnancy rates were 58% (11 of 19) in both treatment groups. Diameter of the corpus luteum and numbers and appearance of ovarian follicles were determined by real-time ultrasonography on d-1 through 5 after injection. No treatment-induced ovulations or changes in the number of ovarian follicles were observed after the injection of the GnRH agonist. More (P less than .05) of the largest follicles within heifers receiving fertirelin acetate showed changes in their appearance on at least the 1st d after injection (6 of 10 vs 1 of 9 control heifers). Fertirelin acetate induced release of LH and FSH from the pituitary within 15 min of injection; both hormones reached peak concentrations at 120 min and then returned to pretreatment concentrations by 300 to 360 min after injection.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

17.
Twenty-five Brangus (BR) and 15 Angus (AN) heifers were used to study the effects of breed and wintering diet on average daily gain (ADG), onset of puberty and plasma concentrations of growth hormone (GH) and insulin-like growth factor 1 (IGF-1). Wintering diets (fed for 107 days beginning November 15) consisted of the following: 1) native grass hay (NGH), 2) ammoniated NGH, 3) NGH plus cottonseed meal, 4) Diet 3 plus corn and 5) Diet 4 plus monensin. After wintering, heifers were transferred to ryegrass pasture for 70 days. Mean ADG during the wintering phase were -.20, -.10, .17, .29 and .39 kg for heifers fed Diets 1 through 5, respectively (P less than .01). ADG was greater (P less than .05) for BR than for AN heifers. Plasma concentrations of GH were higher (P less than .05) in heifers fed Diets 1 and 2 than in heifers fed Diets 3, 4 or 5. Plasma concentrations of IGF-1 were lowest in heifers fed Diet 1 and highest in heifers fed Diets 4 and 5. During ryegrass grazing, GH concentrations were similar for all groups. However, concentrations of IGF-1 were higher (P less than .05) in heifers fed Diets 3, 4 and 5 than in heifers fed Diets 1 and 2. Age at puberty (onset of cyclic progesterone concentrations) was greatest in heifers fed Diet 1 and lowest in heifers fed Diet 5. Weight at puberty was not affected (P greater than .10) by wintering diet but was greater (P less than .01) in BR than in AN heifers. Therefore, negative ADG appears to be associated with elevated plasma GH concentrations in heifers, and plasma IGF-1 concentration appears to be a more accurate indication of nutritional status than plasma concentrations of GH.  相似文献   

18.
Angus x Hereford heifers were used to determine endocrine and ovarian function preceding nutritionally induced anovulation. Six heifers were fed to maintain body condition score (M), and 12 heifers were fed a restricted diet (R) until they became anovulatory. Starting on d 13 of an estrous cycle, heifers were given PGF2alpha every 16 d thereafter to synchronize and maintain 16 d estrous cycles. Ovarian structures of M and R heifers were monitored by ultrasonography daily from d 8 to ovulation (d 1 of the subsequent cycle) until R heifers became anovulatory. Concentrations of LH and FSH were quantified in serum samples collected every 10 min for 8 h on d 2 and 15 (48 h after PGF2alpha), and estradiol and IGF-I were quantified in daily plasma samples from d 8 to 16 during the last ovulatory cycle (Cycle -2) and the subsequent anovulatory cycle (Cycle -1). During the last two cycles before anovulation, M heifers had 50% larger (P < .0001) ovulatory follicles than R heifers and 61% greater (P < .0001) growth rate of the ovulatory follicles. There was a treatment x cycle x day effect (P < .001) for concentrations of estradiol. The preovulatory increase in estradiol occurred in the R and M heifers during Cycle -2 but only in M heifers during Cycle -1. A treatment x cycle x day effect (P < .05) influenced LH concentrations. During Cycle -2, LH concentrations were similar for M and R heifers, but during Cycle -1, M heifers had greater LH concentrations than did R heifers. Concentrations of FSH were greater (P < .05) in R than M heifers after induced luteolysis when R heifers failed to ovulate. There was a treatment x cycle interaction (P < .05) for IGF-I concentrations, and M heifers had 4.7- and 8.6-fold greater IGF-I concentrations than did R heifers during Cycle -2 and -1, respectively. We conclude that growth rate and diameter of the ovulatory follicle, and concentrations of LH, estradiol, and IGF-I are reduced before the onset of nutritionally induced anovulation in beef heifers.  相似文献   

19.
The effects of graded differences in body condition score (BCS) on ovarian follicular development, granulosa cell steroidogenic potential, and growth hormone (GH)-insulin-like growth factor-I (IGF-I) relationships were examined during the puerperium in beef cows fed high fat diets. Cows (n = 36) were allocated randomly about 90 d before expected calving to dietary treatments that resulted in BCS of 3 (very thin), 4 (thin), 6 (optimal) and 8 (obese) at parturition. Body weight and BCS were maintained after parturition by adjusting individual intakes of forage throughout the 17-d experiment, and all cows were fed a high lipid supplement (soybean oil; 0.44 kg/500 kg body weight) during this period. Follicular development in BCS 3 and 4 lagged behind that of BCS 6 and 8 throughout most of the study; however, cows in BCS 4 developed numbers of medium and large follicles by day 15 postpartum that were comparable to those of cows in greater BCS. Mean concentrations of total cholesterol (TCH) and total triglycerides (TG) in serum were greater (P < .05) for cows in BCS 8 vs. 3, 4 and 6 through days 12 (TCH) and 16 (TG) postcalving, respectively. High-density lipoprotein cholesterol (HDL-CH), progesterone and estradiol-17β concentrations in follicular fluid were not affected by BCS at ovariectomy (day 17 postpartum). Addition of insulin and low-density lipoprotein (LDL) to culture media maximized (P < .05) production of progesterone by granulosa cells, but in vivo BCS treatments had no effect. Serum GH concentrations were elevated (P < .05) in cows in BCS 3 and 4 compared to those in BCS 6 and 8 throughout the puerperium. Serum IGF-I tended (P < .10) to increase during the first few days after parturition, and both serum and follicular fluid IGF-I increased (P < .02 and P < .001, respectively) with increasing BCS. Data indicate that cows calving in BCS < 4, and fed such that weight and BCS do not increase, are unlikely to respond to short-term dietary fat supplementation.  相似文献   

20.
To examine ovarian follicular response to low-dose injections of luteinizing hormone-releasing hormone (LHRH), 32 anovulatory, suckled beef cows were allotted to one of four treatment groups and injected with either saline or 500 ng LHRH every 2 h for 48 or 96 h, starting 21.4 +/- .4 d after parturition. Two hours after the last injection of LHRH, cows were ovariectomized and 10 to 15 ovarian follicles per pair of ovaries were removed and categorized by diameter as small (1.0 to 3.9 mm), medium (4.0 to 7.9 mm) or large (greater than or equal to 8.0 mm). Injections of LHRH did not affect (P greater than .10) steroid levels in small follicles or numbers of gonadotropin receptors in small and medium follicles. Concentrations of progesterone in fluid of medium follicles increased 1.5-fold (P less than .05) after 96 h of LHRH, whereas concentrations of estradiol and androstenedione were unchanged. In fluid of large follicles, concentrations of progesterone were fourfold greater (P less than .05) in LHRH-treated than in control cows at 48 h, but by 96 h progesterone was twofold greater (P less than .05) in control than LHRH-treated cows. In large follicles, concentrations of estradiol were unchanged (P greater than .10) after 48 h of LHRH injections but after 96 h estradiol was twofold greater (P less than .05) in LHRH-treated than control cows. Increased concentrations of estradiol in large follicles coincided with increased numbers of binding sites for human chorionic gonadotropin (hCG) but not follicle stimulating hormone (FSH) in granulosa and theca.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

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