An experiment to measure the dose-response relationship of ovulation rate to FSH in cows selected with a history of twinning

Fifteen mature cows and 12 two-year-old heifers were superovulated with purified follicle stimulating hormone (FSH-P) to study the relationship between FSH-P dose level and response (measured as number of palpated corpora lutea (CL) and plasma progesterone concentration). The cattle came from a high prolificacy breeding herd for which cows were originally purchased after producing at least two sets of twins; the heifers were bred in the herd. At dose levels of 8, 16, 24 and 28 mg FSH-P in cows, averages respectively of 2.3, 3.5, 6.9 and 11.1 palpable CLs were found. There was an average difference in response of two CLs between heifers and cows (higher in heifers, though not significantly so). The relationship found between progesterone concentration and CL number could be a useful indicator of superovulation success in future experiments. The regression for cows was 1.25±0.11 ng/ml progesterone per unit increase in CL number, with a correlation of 0.92 between the two variables over the CL range 1 to 25. The corresponding value for heifers was 2.74±0.24 ng/ml per CL (correlation 0.94), or 2.50±0.40 ng/ml per CL (correlation 0.83) if one record (29 CL, 84 ng progesterone/ml) was excluded.     

Relationship between different concentrations of the plasma progesterone at the time of FSH-P treatment and the superovulatory response in Holstein dairy heifers

The aim of this study was to evaluate the influence of two different concentrations of plasma progesterone at the time of FSH-P treatment on the superovulatory response in dairy heifers. Sixteen reproductively sound Holstein heifers (13-15 months of age) were used in this study. Superovulatory treatment was commenced at mid-dioestrus (Day 10 ± 2 of the oestrous cycle) of the synchronized (using two injections of PGF2α, 11 days apart) oestrous cycles. Blood samples were collected on the day and the day after commencing FSH-P treatment and at oestrus for plasma progesterone determination. Heifers were grouped based on two levels of plasma progesterone; Group low progesterone (LP; ranging from 2 to 4.5 ng /ml; n = 7) and Group high progesterone (HP; ≥ 4.6 ng /ml; n = 8) at the beginning of FSH-P treatment (one heifer was excluded from the statistical analysis because of the abnormal progesterone level at oestrus). The superovulatory response in terms of mean numbers of palpable corpora lutea (ovulation rate) was significantly higher (p < 0.05) in group LP than group HP. Ovulation rate was negatively correlated (r = -0.51) with the progesterone concentration at the time of commencing FSH-P treatment (p < 0.05). Data suggest that varying concentrations of plasma progesterone at the time of FSH-P treatment may have a different effect on the outcome of superovulatory response in dairy heifers.     

Udder oedema associated with adrenocortical insufficiency in a herd of Holstein/Friesian cows

The possible involvement of the pituitary-adrenocortical axis with severe pre- and post partum udder oedema was studied in a herd of 60 Holstein/Friesian cows. The prevalence of udder oedema in this herd was about 75 per cent. The animals were fed a diet containing high levels of potassium (average daily potassium intake 410 g per cow). The concentrations of sodium, potassium, chloride and total protein in the plasma of the cows were within their normal ranges. In one animal a very low plasma cortisol concentration (2.30 ng/ml) was accompanied by normal plasma glucose and beta-hydroxybutyrate concentrations. The adrenal responsiveness of two heifers with severe udder oedema was impaired one month after parturition in comparison with 11 normal animals (increases from 3.27 to 38.8 and 23.2 to 37.8 ng cortisol/ml compared with 8.02 +/- 1.19 to 146 +/- 16.7 ng cortisol/ml but returned to normal spontaneously after 175 days. One cow was diagnosed as having primary adrenocortical insufficiency.     

Adrenal-gonad interactions in cattle. Corpus luteum function in intact and adrenalectomized heifers

To determine the effect of the hyperadrenal state on corpus luteum (CL) function, we treated intact and adrenalectomized (ADRX) heifers with adrenocorticotropin (ACTH) and hydrocortisone. ACTH treatment of intact heifers by infusion of 1 mg alpha 1-24 ACTH/24 hr from day 2 to 25 of an estrous cycle increased progesterone concentrations in plasma to 4 +/- .52 ng/ml plasma on days 3 to 4. Thereafter, progesterone concentrations declined, indicating severe suppression of CL function as compared to that of control heifers. Similar infusions of ACTH to ADRX heifers did not alter CL function as reflected by progesterone concentrations in jugular plasma. Infusion of ADRX animals with hydrocortisone succinate (100 mg/24 hr) decreased progesterone in plasma during the cycle, with maximum values averaging less than 4 ng/ml, compared to concentrations of 6 to 7 ng/ml in control ADRX heifers. Chronic administration of ACTH or hydrocortisone to heifers caused a decreased progesterone secretion during the luteal phase of the estrous cycle. On the basis of these results, we suggest that stress, as indicated by the hyperadrenal state, could inhibit progesterone secretion by the corpus luteum.     

Plasma cortisol and progesterone responses to low doses of adrenocorticotropic hormone in ovariectmized lactating cows

The objective of this study was to describe the responses of the plasma progesterone and cortisol concentrations in ovariectomized lactating cows to low doses of adrenocorticotropic hormone (ACTH). The estrous cycles in 3 lactating cows were synchronized, and the cows were ovariectomized in the luteal phase. ACTH challenge tests were conducted at doses of 3, 6, 12 and 25 IU. Blood samples were collected at 30 min intervals, and the plasma progesterone and cortisol concentrations were analyzed by EIA. A concomitant rise in plasma progesterone and plasma cortisol was observed in cows treated with 12 IU or higher doses of ACTH. Significant increments in the plasma cortisol concentrations were observed at all doses of ACTH. The means (+/- SE) of the peak plasma progesterone concentrations after the 3, 6, 12 and 25 IU ACTH challenge tests were 0.6 +/- 0.1, 1.3 +/- 0.4, 1.5 +/- 0.3 and 2.4 +/- 0.3 ng/ml, respectively. The means of the peak plasma cortisol concentrations in the 3 cows after the ACTH challenge were 14.0 +/- 1.5, 17.0 +/- 2.5, 23.3 +/- 3.0, and 33.3 +/- 7.0 ng/ml, respectively. The effects of the doses, time after treatment, and their interaction on the plasma progesterone concentrations after the ACTH challenge were significant (P<0.01). Likewise, the effects of the doses, time after treatment, and their interaction on the plasma cortisol concentrations after the ACTH challenge were significant (P<0.01). The mean AUC values for the plasma progesterone and cortisol concentrations after the ACTH treatments were also significantly affected by the dose of ACTH (P<0.01 and P<0.05, respectively). A significantly positive correlation was obtained between the peak plasma progesterone and cortisol concentrations after different doses of ACTH (r=0.7, P<0.05). The results suggest that lactating dairy cows are capable of secreting a significant amount of adrenal progesterone, reaching up to the minimal concentration necessary to cause suppression of estrus in response to 12 IU ACTH (P<0.01). The concomitant plasma cortisol concentration was 23.3 ng/ml.     

A routine 20-22 days post-service milk progesterone monitoring in dairy cows. Economic evaluation

Three hundred and sixty inseminated Holstein cows were monitored in a controlled trial for low milk progesterone concentration 21-23 days post-breeding. Information about low progesterone cows was given to herdsmen for the experimental group only. Of the cows in the experimental group with milk progesterone of less than or equal to 4.5 ng/ml, 56.0% were inseminated within 2 days of monitoring compared to 28.8% of the control animals. Of the cows reaching the 42-day rectal pregnancy diagnosis, 13.7% and 43.6% were negative for the experimental and the control groups respectively. Inter-service intervals were 34.5 +/- 14.5 days and 44.3 +/- 17.7 days for the experimental and control groups respectively. Pregnancy rates were the same for 264 cows served on routine progesterone monitoring and for 318 cows bred on behavioural oestrus when matched to farm and day of breeding. A gain of US $32.5 (an equivalent of 85 l milk) per lactation for a cow in the monitored herd was established using the data in a model of a 250-cow herd with a total pregnancy goal of 82.4%.     

Effects of plasma progesterone concentrations on LH release and ovulation in beef cattle given GnRH

The effects of plasma progesterone concentrations on LH release and ovulation in beef cattle given 100 microg of GnRH im were determined in three experiments. In Experiment 1, heifers were given GnRH 3, 6 or 9 days after ovulation; 8/9, 5/9 and 2/9 ovulated (P<0.02). Mean plasma concentrations of progesterone were lowest (P<0.01) and of LH were highest (P<0.03) in heifers treated 3 days after ovulation. In Experiment 2, heifers received no treatment (Control) or one or two previously used CIDR inserts (Low-P4 and High-P4 groups, respectively) on Day 4 (estrus=Day 0). On Day 5, the Low-P4 group received prostaglandin F(2alpha) (PGF) twice, 12 h apart and on Day 6, all heifers received GnRH. Compared to heifers in the Control and Low-P4 groups, heifers in the High-P4 group had higher (P<0.01) plasma progesterone concentrations on Day 6 (3.0+/-0.3, 3.0+/-0.3 and 5.7+/-0.4 ng/ml, respectively; mean+/-S.E.M.) and a lower (P<0.01) incidence of GnRH-induced ovulation (10/10, 9/10 and 3/10). In Experiment 3, 4-6 days after ovulation, 20 beef heifers and 20 suckled beef cows were given a once-used CIDR, the two largest follicles were ablated, and the cattle were allocated to receive either PGF (repeated 12h later) or no additional treatment (Low-P4 and High-P4, respectively). All cattle received GnRH 6-8 days after follicular ablation. There was no difference between heifers and cows for ovulatory response (77.7 and 78.9%, P<0.9) or the GnRH-induced LH surge (P<0.3). However, the Low-P4 group had a higher (P<0.01) ovulatory response (94.7% versus 61.1%) and a greater LH surge of longer duration (P<0.001). In conclusion, although high plasma progesterone concentrations reduced both GnRH-induced increases in plasma LH concentrations and ovulatory responses in beef cattle, the hypothesis that heifers were more sensitive than cows to the suppressive effects of progesterone was not supported.     

Phytoestrogens and their metabolites inhibit the sensitivity of the bovine corpus luteum to luteotropic factors

The aim of this study was to examine whether active metabolites of phytoestrogens (equol and para-ethyl-phenol) inhibit sensitivity of bovine corpus luteum (CL) to luteinizing hormone (LH) and to auto/paracrine luteotropic factors (prostaglandin E2-PGE2 and prostaglandin F(2alpha)-PGF(2alpha)), and whether they influence pulsatile progesterone (P4) secretion by the bovine CL. In in vivo experiments, high levels of equol and para-ethyl-phenol were found in plasma and in the CL tissue of heifers and cows fed a soy bean diet (2.5 kg/animal/day), along with lower concentrations of P4 (P < 0.05). Both Prostaglandins (PG) and LH strongly stimulated P4 secretion in cultured pieces of CL that were collected from cows fed a standard diet (P < 0.01). There was no effect of PGs and LH on P4 stimulation in CLs obtained from cows fed a diet rich in soy bean. Finally, we examined whether active metabolites of phytoestrogens participated in regulation of pulsatile P4 secretion and LH-stimulated P4 secretion in vitro using a microdialysis system. Equol and para-ethyl-phenol had no effect on basic and pulsatile P4 secretion in CLs during 240 min of perfusion when compared to the control (P < 0.05). However, they inhibited LH-stimulated P4 secretion (P < 0.05). Phytoestrogens and their metabolites may disrupt CL function by inhibiting PG- and LH-stimulated P4 secretion.     

Management of dairy heifers and its relationships with the incidence of clinical mastitis

AIM: To describe aspects of management of dairy heifers before calving and determine risk factors for clinical mastitis postpartum in heifers, at the herd level, under pasture-based management systems in the Waikato and Taranaki regions of New Zealand. METHODS: Dairy herdowners (n=578) provided information via a prospective survey about their practices for rearing heifers and management of mastitis. A proportion of herdowners (n=250) subsequently provided data on the cases of clinical mastitis in their herds, including the date, cow identification, age and quarter affected from cases occurring in the 4 months after the planned start of calving (PSC) in the subsequent lactation. The relationship between management factors and the proportion of heifers diagnosed with clinical mastitis within a herd was examined using bivariate and multivariate analyses. RESULTS: The herd average percentage of heifers with clinical mastitis was 13.6 (95% confidence interval (CI)=12.3-14.9)%, and multiparous cows with clinical mastitis was 9.0 (95% CI=8.2-9.8)% in the first 4 months of lactation. There were positive relationships between the proportion of heifers with clinical mastitis and average milk production per cow (kg milksolids/ lactation; p<0.001), number of cows milked per labour unit (p=0.003), stocking rate (<> 3.30 cows/ha; p=0.002), and incidence of clinical mastitis in multiparous cows (%/120 days; p<0.04), in the final multivariate model. The proportion of heifers with clinical mastitis per herd was lower in herds that milked their lactating cows in multiple groups (p=0.02). CONCLUSIONS: The risk of clinical mastitis in heifers was significantly associated with management practices. It may be possible to reduce the incidence of clinical mastitis in heifers by modification of management practices at the herd level, and further studies are required to investigate this.     

Relationship of ovarian contents to plasma progesterone concentration in the swamp buffalo (Bubalus bubalis)

Using rectal palpation and laparoscopy, the relationship of ovarian contents to plasma progesterone concentration during the oestrous cycle, early pregnancy and post partum periods in the swamp buffalo (Bubalus bubalis) was studied. During the oestrous cycle, four stages in the lifespan of the corpus luteum were seen laparoscopically. The mean (+/- sd) concentrations of progesterone in plasma in cows with and without a corpus luteum on their ovaries were 1.49 +/- 0.78 ng/ml (n = 31) and 0.14 +/- 0.09 ng/ml (n = 14), respectively. Plasma progesterone levels reflected age-dependent changes occurring in the cyclic corpus luteum. The accuracy of diagnosing ovarian contents was 82 and 91 per cent for rectal palpation and plasma progesterone levels respectively. Approximately 29 per cent follicles (larger than 10 mm) were incorrectly diagnosed as corpora lutea by rectal palpation.     

奶牛发情期的奶孕酮分析

<正> 影响奶牛人工授精成功率的主要原因是对发情期能否正确判断,适时输精。据1981年联邦德国Bavarian动物健康服务机构的报告,输精时间不正确,是影响奶牛繁殖率的重要因素。由于孕酮含量在发情周期中呈规律性变化,在发情期显著下降,因此可     

Use of milk progesterone enzyme immunoassay for differential diagnosis of follicular cyst, luteal cyst, and cystic corpus luteum in cows

In 160 cows with ovarian cysts as determined by rectal palpation, differentiation was made of follicular cyst, luteal cyst, and cystic corpus luteum on the basis of milk progesterone concentrations estimated by an enzyme immunoassay before and at 10 days after cows were treated with gonadotropin-releasing hormone. Cows having a progesterone concentration in skim milk less than 1.0 ng/ml were considered to have follicular cysts and those with concentrations of 1.0 ng/ml or higher were regarded as the cases of luteal cyst or cystic corpus luteum. Luteal cyst was characterized by progesterone values remaining high in the cows for 10 days after treatment, and cystic corpus luteum was characterized by a decrease in progesterone concentration after cows were treated. By the rectal palpation procedure it was impossible to differentiate luteal cyst and cystic corpus luteum from follicular cyst. The frequencies of follicular cyst, luteal cyst, and cystic corpus luteum were 65%, 19%, and 16%, respectively. Of 104 cows with follicular cysts as defined by milk progesterone assay result, 73 (70%) responded to the treatment with gonadotropin-releasing hormone, the milk progesterone concentration increasing from 0.7 +/- 0.2 ng/ml (mean +/- SD) to 1.8 +/- 1.1 ng/ml. The accuracy of rectal palpation 10 days after treatment for judgment of luteinization of follicular cyst confirmed by milk progesterone analysis was only 30% (48 cows of 160).     

Insulin-like growth factor-I concentration in Holstein female cattle: variations with age, stage of lactation and growth hormone-releasing factor administration

Plasma insulin-like growth factor-I (IGF-I) concentrations were monitored in Holstein females through different periods of their growth, lactation and after acute or chronic growth hormone-releasing factor (GRF) administration. Plasma samples were radioimmunoassayed using a human IGF-I antibody after a 24 hr incubation in a HCl(.1N)-glycine(.2M) buffer (pH 2). In a first study, IGF-I concentrations were measured in Holstein females of different ages and(or) stages of lactation (n = 6 per group). The IGF-I concentrations in newborn calves (102.0 +/- 11.3 ng/ml) markedly decreased (P less than .01) in 1 mo old animals (50.2 +/- 7.1 ng/ml), then increased (P less than .01) to 137.0 +/- 5.1 and 137.4 +/- 11.0 ng/ml in 6 and 10 mo old heifers, respectively. In dairy cows, IGF-I concentrations were low 24 hr post-partum (44.7 +/- 7.6 ng/ml) and then increased (P less than .05) to remain stable throughout lactation (91.3 +/- 4.9, 92.8 +/- 12.9, 96.1 +/- 7.6, 90.7 +/- 8.8 ng/ml at 2, 3, 6 and 9 mo of lactation, respectively). There was a further increase (P less than .05) to 113.7 +/- 3.1 ng/ml during the dry period. In a second trial, blood samples were collected from lactating dairy cows every 2 hr for 24 hr following a sc injection of saline (n = 4) or human (h) GRF (1-29)NH2 (10 micrograms/kg BW, n = 4). The IGF-I peak concentration was reached on average 10 hr after the GRF injection and was higher (P less than .01) in treated cows than in control cows (135.4 vs 86.9 +/- 16.2 ng/ml). In the last trial, daily sc injections of 10 micrograms of hGRF(1-29)NH2 per kg BW to dairy cows (252 days of lactation) for 57 days, which increased milk production by 14% (2 kg/day), also increased (P less than .01) IGF-I concentration: 127.1 +/- 5.3 and 118.0 +/- 1.6 vs 90.7 +/- 4.7 and 96.0 +/- 5.0 ng/ml on days 29 and 57 of treatment for treated (n = 9) and control (n = 8) cows, respectively. Thus, the IGF-I concentration in dairy cattle varies with age and stage of lactation, and is increased by GRF administration in lactating dairy cows.     

Behaviour of cows in cubicles and its possible relationship with laminitis in replacement dairy heifers

The behaviour of cows in cubicles was studied in two dairy herds which were under the same ownership and had similar buildings and management systems. One of the herds had an annual problem of lameness due to laminitis leading to solar ulceration in the replacement first lactation heifers. There were considerable behavioural differences between the cows in the two herds. In the problem herd the heifers and cows stood for significantly longer, more heifers were seen not to use the cubicles, and there were more examples of aberrant behaviour than in the other herd. Less straw was used for cubicle bedding in the problem herd and when the amount used was increased to one bale per 10 cows per day no new cases of laminitis and solar ulceration occurred in the heifers.     

Cortisol and luteinizing hormone after adrenocorticotropic hormone administration to postpartum beef cows

Cortisol and luteinizing hormone (LH) were measured in serum after the administration of adrenocorticotropic hormone (ACTH) to suckled (S) and nonsuckled (NS) beef cows. Blood was sampled on 2 consecutive days every 2 weeks for four bleeding periods starting 14 days after calving. Cows were injected with 200 IU ACTH or saline in a 2-day switchback design. Serum was collected before ACTH or saline injection and at 30-min intervals thereafter for 8 hours. Average cortisol concentrations in serum were similar in S and NS cows (6.4 +/- .6 and 6.1 +/- .8 ng/ml, respectively) after saline. Average cortisol concentrations in serum collected during an 8-hr period after ACTH on days 14, 28, 42 and 56 postpartum were 24.7 +/- 2.4, 31.8 +/- 3.5, 36.4 +/- 4.2 and 40.7 +/- .5 ng/ml, respectively, for S cows, and 31.1 +/- 2.9, 44.7 +/- 5.2, 45.0 +/- 5.7 and 46.0 +/- 5.4 ng/ml, respectively, for NS cows. Cortisol response to ACTH, measured as area under the response curve, was greater (P less than .05) in NS than in S cows. Amount of cortisol released by 200 IU ACTH was maximal by days 28 to 29 postpartum in NS cows, but the response increased gradually between days 14 to 15 and days 56 to 57 in S cows. overall, LH in serum averaged .55 +/- .08 ng/ml for S cows and .92 +/- .06 ng/ml for NS cows after saline, and .49 +/- .07 ng/ml for S cows and .94 +/- .06 ng/ml for NS cows after ACth. Although mean and peak serum LH concentrations did not differ between cows given ACTH and those given saline, the number of LH peaks and the number of cows having LH after saline. Mean serum LH concentrations were lower (P less than. 05) in S than in NS cows at 28 days postpartum. The number of LH peaks was lower (P less than .05) and the magnitude of the largest LH peak tended to be lower (P less than .06) in S cows at all sampling periods.     

A possible influence of the bull on the incidence of embryonic mortality in cattle

Milk progesterone profiles were used to study the high incidence of embryonic mortality between 30 to 80 days after insemination in 91 cows in a single herd. The progesterone levels dropped to basal values at 46.7 +/- 1.37 days after service in 22 per cent of apparently pregnant cows. Embryo loss occurred significantly more frequently following services by one bull (Z). The mortality rates were 14/32 (44 per cent) in cows conceiving to Z compared with 8/73 (11 per cent) in cows conceiving to other bulls. There was no significant effect of the age of the cow or yield on the incidence of embryonic mortality.     

Influence of experimental intrauterine infusion of Arcanobacterium pyogenes solution on ovarian activity in cycling cows

To examine the ovarian response to Arcanobacterium pyogenes (A. pyogenes) in uterus, bacterial solution was infused into the uteri of cows, and the follicle and corpus luteum (CL) development were monitored with a real-time ultrasound instrument. In addition, the plasma concentrations of progesterone (P(4)) and 13, 14-dihydro-15-keto-PGF(2alpha) (PGFM) were determined. A 10 ml bacterial solution that contained A. pyogenes (8 to 15 x 10(8) CFU/ml) was infused into the uterus of eight cows transcervically three days after natural ovulation. As a control, sterile physiological saline was infused into 4 other cows. The dominant follicle developed normally in 8 cows after bacteria inoculation. In 4 of these 8 cows, the developing CL regressed, and the first wave dominant follicles, which normally become atretic, ovulated after the inoculation. In the remaining 4 cows, the CL did not regress. The PGFM concentration increased transiently in all 8 cows after the infusion. The mean PGFM concentration of the cows with a regressed CL was significantly lower (P<0.01) than that of the cows whose CLs did not regress. In the control cows, there was no regression of developing CLs, no ovulation of first wave dominant follicles and no transient increase in PGFM after the infusion of sterile physiological saline. These results show that infusion of A. pyogenes into the uterus did not affect folliculogenesis and might have induced PGF(2alpha) production from the uterus.     

Insulin-like growth factor (IGF)-I and IGF binding proteins-2, -3, -4, -5 in porcine corpora lutea during the estrous cycle; evidence for inhibitory actions of IGFBP-3

In this study we measured protein concentrations of insulin-like growth factor (IGF)-I and IGF binding proteins (IGFBPs) 2-5 in porcine corpora lutea (CLs) throughout the estrous cycle (Experiment 1), and examined the effects of IGFBP-3 and IGFBP-3 antibody (AB) on luteal progesterone (P4) secretion in vitro (Experiment 2). For Experiment 1, (CLs) and serum were collected on days (D) 4, 7, 10, 13, 15 and 16 of the estrous cycle (n = 5 animals per day). IGF-I was extracted from CLs and sera, and measured by radioimmunoassay (RIA). IGFBPs were measured in CLs by ligand blots. For Experiment 2, CLs (from Experiment 1) were enzyme dissociated and luteal cells cultured (24 h) in Medium 199 (M199) containing (0-500 ng/ml) IGFBP-3 (+/-IGF-I; 100 ng/ml), or (0-10 microg/ml) IGFBP-3 AB. P4 in media was measured by RIA. In Experiment 1, luteal IGF-I concentrations (ng/g tissue) were maximal on day 4 and gradually decreased thereafter. Serum IGF-I concentrations (ng/ml) were highest on days 4 and 7, compared with days 10-15. Peak levels of luteal IGFBP-3 were also seen on days 4 and 7 of the cycle. Luteal IGFBP-2 concentrations showed a tendency to increase on day 16 (P < 0.05 versus day 10), but no significant changes in IGFBP-4 or -5 were seen. In Experiment 2, IGFBP-3 (w IGF) inhibited the steroidogenic actions of IGF-I, but had no significant actions alone (IGFBP-3 w/o IGF). Finally, IGFBP-3 AB stimulated P4 secretion on days 4 and 7, but not on days 10-16. We conclude that IGFBP-3 inhibits IGF-I actions in the porcine CL.     

Ovarian morphological conditions and the effect of injection of human chorionic gonadotropin on ovulation rates in prepuberal gilts with two morphologically different ovarian types

The purpose of this experiment was to determine the ovulation rate after treatment with human chorionic gonadotropin (hCG) in two groups of gilts characterized by different ovarian morphology: grape-type (GT; n = 11) and honeycomb-type (HT; n = 7). At 170 d of age (d 0), gilts were examined by laparoscopy and ovarian type was determined by the distribution of macroscopic follicles present on the ovarian surface. Five to ten minutes after surgery, each gilt received a single injection (i.m.) of 750 IU of hCG. At d 0, GT ovaries had a greater number of large follicles (greater than or equal to 6 mm) than HT ovaries (10.0 +/- .5 vs 2.6 +/- .3; P less than .05), whereas HT ovaries had more small follicles (1 to 3 mm; HT: 42.3 +/- .8 vs GT: 26.7 +/- .9; P less than .05) and total follicles (HT: 59.4 +/- 2.3 vs GT: 52.2 +/- 1.5; P less than .05), although numbers of medium follicles (4 to 5 mm) were similar (GT: 15.6 +/- .8 vs HT: 14.6 +/- 1.7; P greater than .10). Number of induced corpora lutea (CL) per ovary was greater (P less than .05) in gilts with GT ovaries (10.59 +/- 2.9 CL) than in gilts with HT ovaries (5.21 +/- .66 CL). Total weight of luteal tissue (LT) per ovary and serum progesterone concentrations 8 d after induction of ovulation were greater in GT gilts than in HT gilts (GT: 6.37 +/- 1.09 g vs HT: 3.31 +/- .49 g for LT, P less than .05; GT: 21.08 +/- 4.76 ng/ml vs HT: 13.40 +/- 2.05 ng/ml for progesterone, P less than .07).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of trenbolone acetate on ovarian function in culled dairy cows

The ovarian cycles of 48 culled dairy cows were monitored by assaying plasma progesterone concentrations. Twenty-four cows received a subcutaneous implant of 300 mg trenbolone acetate (Finaplix; Hoechst) at the beginning of the study. Of the implanted cows, two were pregnant, six continued to cycle although their peak progesterone concentrations were significantly lower than in control cows (5.65 +/- 0.71 compared with 8.19 +/- 0.47 ng/ml; P less than 0.01). Prolonged periods (13 to 92 days) of low progesterone concentrations (less than 1 ng/ml) occurred in 12 of the implanted cows. In six of seven cows in which normal cycles had not resumed by the time of slaughter two to five ovarian follicles of diameter greater than or equal to 10 mm were found post mortem. Persistent luteal function (greater than 35 days) occurred in the absence of pregnancy or gross uterine pathology in five of the implanted cows, two of which had recovered spontaneously by the time they were slaughtered. There was no difference in plasma luteinising hormone concentrations between the implanted and control cows. It is concluded that trenbolone acetate affected the ovarian cycle of the cows in several ways through changes other than the modification of tonic luteinising hormone secretion.