奶牛生殖激素的分析 Ⅵ.发情周期和怀孕期间奶桶混合乳17β-雌二醇的变化

采用放射免疫分析法测定了21头黑白花奶牛在发情周期和怀孕期间奶桶混合乳17β-雌二醇的变化。测定结果表明,发情周期和怀孕期奶桶混合乳17β-雌二醇的变化趋势与外周血浆基本一致。在发情当天17β-雌二醇出现一次分泌高峰(P<0.01),以后无论在发情周期或是在怀孕期间17β-雌二醇的变化只能说是呈现一种脉冲式的变化(P>0.05),无所谓第二次或第三次高峰。奶桶混合乳17β-雌二醇的含量为外周血浆的6倍。     

奶牛胎衣不下与乳中孕酮、雌二醇含量的关系

用放射免疫法测定了50头中国荷斯坦牛分娩当天及第2 d乳中的孕酮(P)和雌二醇(E2)的含量。结果表明:胎衣不下牛产后的孕酮含量与正常牛无显著差异;而雌二醇则比正常牛低,在分娩当天低将近1/3。但t检验的结果差异均未达显著。     

Pregnancy rates during experimentation in dairy cows

This study investigated pregnancy rates on day 16 in dairy cows following artificial insemination and blood sampling to monitor hormonal status. Collection of blood samples by jugular venepuncture coupled with single fixed time insemination resulted in a poor pregnancy rate (27.8%). Modification of the protocol to include double insemination and collection of blood samples from jugular cannulae inserted four days prior to insemination did not improve pregnancy rate (27.3%). Acclimatization of cows to the experimental facility, however, resulted in a dramatic increase in pregnancy rate (85.7%;P < 0.005). This improvement was not associated with any difference in plasma progesterone but was associated with a marked advancement in the decline in oestradiol at the end of the follicular phase, indicative of earlier ovulation. Non-pregnancy was associated with a delayed fall in oestradiol and reduced plasma concentrations of progesterone. The results support a role for inadequate progesterone in early embryo mortality but suggest that impaired ovulation is a more important problem in cows under the 'stress' of experimentation.     

Some Arthropods Affecting Man and Livestock in New Zealand

Extract

At present, the standard tuberculin test used in New Zealand is the subcaudal intradermal test using 0·1 ml Commonwealth Serum Laboratories Synthetic Medium tuberculin, animals being classified as positive or negative to the test on the presence or absence of any swelling either visible or palpable at the site of the injection at the 96th hour.     

The reproductive performance of anoestrous dairy cows following treatment with progesterone and oestradiol prior to the start of mating

Aims: To determine the reproductive performance of cows diagnosed as anoestrus prior to the planned start of mating (PSM) when they were either treated when first diagnosed, or left untreated until 16 days after the PSM.

Methods: A clinical trial was conducted during the 1996/97 and 1997/98 breeding seasons involving 823 anoestrous dairy cows in 14 herds. On Day-8 (PSM = Day 0), cows in one group (Treated) were each treated with an intravaginal device containing 1.9 g of progesterone (CIDR).The CIDR device was removed on Day-2, and on Day-1 each cow was injected intramuscularly with 1 mg oestradiol benzoate. Cows in the second group (Control) remained untreated at the time of first examination. All cows detected in oestrus after the PSM were mated by artificial insemination (AI) or a bull. Sixteen days after the PSM, all cows that had not been mated were presented for veterinary examination, and those which were still classified as anoestrus were treated with the previously described CIDR regimen. Pregnancy status and approximate date of conception were determined by palpation per rectum 10-13 weeks after the PSM or 6 weeks after the end of the mating period.

Results: Treatment of anoestrous cows 8 days before the PSM significantly increased the number of cows detected in oestrus (95.0% vs 63.1%;p < 0.001) and conceiving (59.5% vs 38.8%;p < 0.001) during the first 21 days of mating, and reduced the interval from PSM to conception by 7.5 days (p < 0.001). There was no significant difference between the conception rate of cows mated following the CIDR treatment regimen compared to cows mated at their first spontaneous oestrus after calving (52.4% vs 58.3%; p = 0.143).

Conclusion: Diagnosis and treatment of anoestrous dairy cows prior to the start of mating significantly improves their reproductive performance under the seasonal mating conditions typical of spring-calving New Zealand dairy herds.     

The long‐term effect of α‐ketoglutarate,given early in postnatal life,on both growth and various bone parameters in pigs

The long‐term effect of α‐ketoglutarate (AKG) given for 21–24 days post‐partum, on the skeleton of commercial pigs, was investigated. In experiment A, 12 pigs were given AKG [0.1 g/kg of body weight (b.w.) per day per os], while 12 controls were administered vehicle. At day 169, the left and right femur, humerus and sixth ribs were analysed for mechanical and geometrical properties and quantitative computed tomography. In experiment B, 32 piglets were divided equally into an AKG group (0.3 g/kg of b.w. per day) or a control group. Blood, taken at days 24 and 53 was analysed for plasma 17 β‐oestradiol. The main bone effect of AKG was to increase bone length in the sixth rib (7.3%, p < 0.01), ultimate strength (23%, p < 0.05), Young´s modulus (52%, p < 0.001) and maximum elastic strength (31%, p = 0.056) compared with controls. In both experiments, AKG preferentially increased the growth of female piglets, whilst for male piglets AKG had the opposite effect. In addition, AKG elevated plasma 17 β‐oestradiol levels compared to those of controls at the end of the period of treatment (20%, p = 0.002). It is concluded that AKG has long‐term effects on rib properties when given early in postnatal life whilst it elevates plasma 17 β‐oestradiol levels only so long as it is being administered.     

The effects of phospholipase C on oestradiol and progesterone secretion in porcine granulosa cells cultured in vitro

Granulosa cells play important roles in the regulation of ovarian functions. Phospholipase C is crucial in several signalling pathways and could participate in the molecular mechanisms of cell proliferation, differentiation and ageing. The objective of this study was to identify the effects of phospholipase C on the steroidogenesis of oestradiol and progesterone in porcine granulosa cells cultured in vitro. Inhibitor U73122 or activator m‐3M3FBS of phospholipase C was added to the in vitro medium of porcine granulosa cells, respectively. The secretion of oestradiol decreased after 2 hr, 8 hr, 12 hr, 24 hr and 48 hr of treatment with 500 nM U73122 (p < .05) and decreased after 2 hr of treatment in the 500 nM m‐3M3FBS addition group (p < .05). The secretion of progesterone increased after 4 hr of treatment with 500 nM U73122 (p < .05) and increased after 2 hr and 8 hr of treatment in the 500 nM m‐3M3FBS addition group (p < .05). The ratio of oestradiol to progesterone decreased at each time point, except 8 hr after the addition of 500 nM U73122 (p < .05). The ratio of oestradiol to progesterone decreased after 2 hr (p < .05) of treatment with 500 nM m‐3M3FBS. In genes that regulate the synthesis of oestradiol or progesterone, the mRNA expression of CYP11A1 was markedly increased (p < .05), and the mRNA expression of other genes did not change significantly in the U73122 treatment group, while the addition of m‐3M3FBS did not change those genes significantly despite the contrary trend. Our results demonstrated that phospholipase C can be a potential target to stimulate the secretion of oestradiol and suppress progesterone secretion in porcine granulosa cells cultured in vitro, which shed light on a novel biological function of phospholipase C in porcine granulosa cells.     

Endocrinological characterization of an ovarian sex cord–stromal tumor with a Sertoli cell pattern in a Japanese Black cow

A Japanese Black cow was evaluated for prolonged post‐partum anestrus and enlargement of the right ovary. Transrectal ultrasonography revealed that the right ovary was markedly enlarged and had a solid appearance, while the left ovary was small and inactive. The presumptive diagnosis was directed towards granulosa‐theca cell tumour (GTCT) which was supported by markedly elevated plasma anti‐Müllerian hormone (AMH; 332.0 ng/ml), oestradiol (E₂; 103.3 pg/ml) and immunoreactive inhibin (ir‐INH; 2.1 ng/ml) in comparison with the diagnostic cut‐off points for bovine GTCTs. Since the cow had been infertile and had swelling of the udder, slaughter was chosen. Histopathological examination revealed that the tumour was an ovarian sex cord–stromal tumour (SCST) with a Sertoli cell pattern. These findings suggest that plasma AMH, ir‐INH and E₂ could be possible biomarkers for bovine ovarian SCST with a Sertoli cell pattern, whereas this case could not be distinguished from GTCTs based on endocrinological profile.     

Acute stimulation of a smooth muscle constrictor by oestradiol‐17β via GPER1 in bovine oviducts

Oviducts play roles in reproductive processes, including gametes transport, fertilization and early embryo development. Oviductal transport is controlled by various factors such as endothelins (EDNs) and nitric oxide (NO), smooth muscle contracting and relaxing factor, respectively. EDNs and NO production depend on an ovarian steroid hormone, oestradiol‐17β (E2) and E2 quickly exerts their biological functions through G protein‐coupled oestrogen receptor 1 (GPER1), which mediates rapid intracellular signalling. Because follicular fluid which contains a high concentration of E2 enters the oviduct, we hypothesized that E2 in the follicular fluid participates via GPER1 in producing EDNs and NO. To test this hypothesis, we investigated 1) the expression and localization of GPER1 in bovine oviductal tissues and 2) rapid effects of E2 via GPER1 on EDN1, EDN2 and inducible NO synthase (iNOS) expression in cultured bovine oviductal isthmic epithelial cells. GPER1 was observed in the oviductal epithelium, stroma and smooth muscle, and its expression was highest in the isthmus. Short‐term treatments (≤1 hr) of E2 increased EDN2 mRNA expression in the isthmic epithelial cells, although E2 did not affect EDN1 and iNOS mRNA expressions. Results of GPER1‐selective agonist G‐1 and GPER1‐selective antagonist G‐15 treatments revealed acute stimulation by E2, which is mediated via GPER1. The overall findings suggested that E2 in follicular fluid rapidly stimulates EDN2 expression via GPER1 in the isthmic epithelial cells. Follicular fluid may play a role in retention of the ovulated oocyte in the end of ampulla by contracting the isthmus for successful fertilization.