Twenty-four-hour Profiles of Serum Prolactin and Luteinizing Hormone in Anoestrous Crossbred Bitches

The dynamics of prolactin (PRL) and luteinizing hormone (LH) secretion in the anoestrous bitch is poorly known. Therefore, the objective of this study was to characterize the 24 h profiles of serum PRL and LH in crossbred anoestrous bitches and to assess whether a relationship exists between the secretory patterns of these two hormones. Serum PRL and LH concentrations were measured in 10 healthy anoestrous crossbred bitches at 145 min intervals for 24 h. During the experiment the animals received continuous artificial illumination and remained undisturbed except at the time of blood sampling. Serum PRL was measured by a homologous enzyme‐linked immunosorbent assay, whereas LH and progesterone (P₄) were determined by radioimmunoassay. The anoestrous state of the bitches was assessed by vaginal cytology, vaginoscopy and physical examination. Two groups of animals were identified according to their PRL levels: a high PRL group (n=3, mean ± SEM 12.3 ± 2.7 ng/ml) and a low PRL group (n=7, mean ± SEM: 2.5 ± 0.9 ng/ml). In the low PRL group, the PRL profiles were flat and did not show any significant circadian pattern. Nevertheless, occasional single‐point peaks were detected in some of the bitches. In the high PRL group the individual PRL profiles were variable. To detect the presence of a circadian change of PRL concentrations, two different sets of time windows (TW) of sampling were studied. The first set was: day [TW1A, samples 1–5 (0900–1840 h)] and night [TW1B, samples 6–10 (2105–0645 h)]. The second set was chosen after visual inspection of the average PRL profiles for both (high and low) groups: [TW2A, samples 3–7 (1350–2330 h) and TW2B, samples 1–2 and 8–10 (0155–1125 h)]. PRL concentrations were not significantly different between day and night. In the high PRL group, but not in the low PRL group, average serum PRL was significantly (p < 0.01) higher in TW2A than TW2B. In both groups serum LH levels were more homogeneous than PRL levels. Neither TW showed circadian changes in LH patterns of secretion (TW1A versus TW1B, p < 0.69; TW2A versus TW2B, p < 0.88). On the other hand, bitches in the high PRL group showed significantly (p < 0.01) lower serum LH levels than those in the low PRL group of animals. Serum PRL concentrations presented a significant inverse correlation with LH concentrations (r=?0.21, p < 0.03) and a significant positive correlation with P₄ concentrations across the study (0.92, p < 0.01). It is concluded that in anoestrous crossbred bitches serum PRL is highly variable and inversely related to LH. No circadian rhythm of PRL secretion appears to exist in most anoestrous bitches.     

外源激素对间情期毕格犬发情及妊娠的影响

给６只间情期雌性毕格犬注射外源激素雌酮（Ｅ１）、孕马血清促性腺激素（ＰＭＳＧ）、人绒毛膜促性腺激素（ｈＣＧ）和雌二醇（Ｅ２），结果有５只犬发情，３只受孕，产仔１４只。发情前期、发情期与自然发情犬无明显差别。发情犬血浆ＬＨ高峰出现在阴门见有血样分泌物后（１１．６±１．６）ｄ；在ＬＨ高峰期血浆孕酮（Ｐ４）明显升高，其后１２ｄ，Ｐ４含量达峰值；８０％阴道上皮细胞角化后（６．４０±０．６８）ｄ出现ＬＨ峰     

Effect of Changes in Light on Hormonal Secretion and Milk Production of Dairy Cows in Early Lactation

Abstract

Two experiments were carried out to investigate the effect of a change in day length and light intensity on the concentration of prolactin in milk and plasma, on milk production during the first two months of lactation, and on the daily variation in plasma concentrations of prolactin, melatonin, growth hormone, Cortisol and insulin 24–48 h after calving. The light programmes used were 9.5 L:14.5 D and 17.5 L:6.5 D. During 4–8 weeks before calving one group was on the long day programme (LL group) and the other on the short day programme (DL group) in both experiments. After calving, both groups were on the long day programme. Indoor light intensity was 150 lux at the eye level of the cows in both experiments. Outdoor light intensity during the summer was also included in the calculationsln the second experiment.

In the first study, with 6 cows and 6 first calvers, the plasma concentration of prolactin increased significantly in the LL group but not in the DL group during 30-3 days before calving (b = 1.88±0.70 μg/l/d, p<0.01). During weeks 1–8 after calving there was a similar increase in the DL group (b _plasma = 12.03 μg/l/w, p < 0.001 and b _milk = 0.88±0.37 μg/l/w, p <0.05), but no significant change in the LL group. The first calvers of the LL group produced 10–12% more energy-corrected milk (3.14 MJ/kg) and kg milk fat than those of the DL group (p<0.05). No production traits of the cows were influenced by the light programmes (p>0.40), but both groups of cows were severely affected by illness after calving. Melatonin, growth hormone and Cortisol concentrations in plasma showed no significant daily variation and no effect of light programmes (p>0.45). There was no significant difference in the insulin concentration between groups (p = 0.28), although the group on long days had lower concentrations at all hours. The concentration of plasma prolactin was lower during the dark hours than during the light hours (p<0.05). In the second experiment, 36 first calvers were stalled 6–8 weeks before expected calving following a period of grazing. The stalling involved a substantial decrease in daily maximum light intensity for the cows. From the first day in experiment to 10 days before expected calving, the plasma prolactin concentration decreased from 41.5 ± 3.7 to 29.0 ± 3.3 μg/l, p<0.05, equally in both groups. After calving, the plasma prolactin concentration increased in the DL group (b=4.20 ± 1.93 μg/l/w, p<0.05) to a higher level than at the start of the experiment. There was no difference in milk production (p>0.50).

The results indicate that a continuously increasing secretion of prolactin in the last month of gestation may promote milk production in early lactation.     

Effect of Repeated Cabergoline Treatment on the Vernal Transition and Hair Shedding of Mares (Year 1) and a Subsequent Comparison of the Effect of Starting Date on Prolactin Suppression (Year 2)

Two studies were conducted to determine efficacy of cabergoline for suppressing prolactin (PRL) and the possible effects on vernal transition in mares. In experiment 1, six mares each received either vehicle or cabergoline (5 mg, intramuscularly) every 10 days for 12 treatments beginning February 4, 2013. Blood samples were drawn regularly, and mares were challenged with sulpiride periodically to assess PRL suppression. Weekly hair samples were obtained to determine shedding. Prolactin was suppressed (P < .05) by cabergoline, but suppression waned in spring. There was no effect (P > .05) of treatment on day of first ovulation, luteinizing hormone, or follicle stimulating hormone. Hair shedding was generally suppressed (P = .05). In 2014 (experiment 2), eight of the same 12 mares were used in a similar experiment to determine if the rise in PRL observed in experiment 1 was due to refractoriness to cabergoline or perhaps another factor. Treatment began on April 6, 2014, corresponding to the increase in PRL in treated mares in experiment 1. Mares were treated with cabergoline or vehicle until June 5. Prolactin was suppressed (P < .05) by cabergoline, and the pattern of apparent escape from suppression was similar to year 1. We conclude that (1) cabergoline at this dose alters hair shedding but does not alter the time of first ovulation in mares and (2) relative to our previous reports of cabergoline treatment in the fall, there is a seasonal effect on the ability of this dose of cabergoline to suppress unstimulated PRL secretion.     

大豆黄酮对奶牛免疫功能和血清及乳中几种激素水平的影响

研究口服大豆黄酮对奶牛免疫功能和血清及乳中生长激素(GH)、催乳素(PRL)、生长抑素(SS)水平的影响。结果表明：1)大豆黄酮能明显提高血清及乳中特异性抗体水平,表明奶牛整体和乳腺器官的体液免疫功能明显增强。2)奶牛血清及乳中GH、PRL含量明显高于对照组,而血清SS含量显著低于对照组。本实验结果提示垂体GH、PRL和体内SS可能参与了大豆黄酮对奶牛免疫功能的调节过程。     

Effect of Naloxone on Serum Luteinizing Hormone Concentration in Anovulatory Holstein Cows During the Early Postpartum Period

This experiment was conducted to investigate the effect of naloxone (NAL), an opioid receptor antagonist, on pituitary LH secretion in anovulatory Holstein cows during the early postpartum period when cows were expected to be in negative net energy balance. Twenty-three cows (11 primiparous) received either saline (n = 12) or 1 mg/kg BW NAL i.v. (n = 11) on Day 14 or 15 postpartum. Jugular blood samples were collected at 15-min intervals for 2 hr before and 2.5 hr after NAL or saline. All cows received 3 ug gonadotropin releasing hormone (GnRH) at 2.5 hr post-NAL or -saline and blood collection was continued for 1 hr. Mean serum progesterone concentration was 0.33 ± 0.2 ng/ml. Mean net energy balance for all cows was -5.5 ± 0.6 Mcal/day. Naloxone caused a transient increase (P < 0.05) in serum LH concentrations in both primi- and multiparous cows within 45 min after administration. In contrast, serum LH concentrations remained unchanged in saline-treated cows. GnRH increased (P < 0.05) LH and there was no effect of treatment. These results suggest that modulation of LH secretion, at least in part, may be mediated via endogenous opioids in dairy cows before first postpartum ovulation.     

Effect of Early Postpartum Ovulation on Fertility in Dairy Cows

Our objectives were to determine the effects of early ovulation on fertility and uterine health of dairy cows. Four hundred and forty‐five Holstein cows (185 primiparous and 260 multiparous) from five herds were used. Blood samples were collected at 21, 35 and 49 days in milk (DIM) and cows were considered to be cyclic at 21 DIM (Cyc21) if serum progesterone (P4) concentration was above 1 ng/ml, cyclic by 49 DIM (Cyc49) if P4 concentration was above 1 ng/ml at 35 or 49 DIM, or not cyclic (NotCyc) if P4 concentration was below 1 ng/ml at all sample times. Endometrial cytology for diagnosis of subclinical endometritis was examined at 49 DIM in a subset of 414 cows. Cows in the group Cyc21 had increased hazard of insemination, for the first service, compared with cows in Cyc49 [hazard ratio (HR) = 1.40; 95% CI = 1.10–1.79; p = 0.006] and NotCyc (HR = 2.07; 95% CI = 1.52–2.82; p < 0.001). Cows in the Cyc49 group also had increased hazard of insemination compared with cows in the NotCyc group (HR = 1.47; 95% CI = 1.13–1.93; p = 0.005). Median days to insemination were, respectively, 71, 76 and 96 for cows in Cyc21, Cyc49 and NotCyc groups. Cows in Cyc21 had greater first service pregnancy per AI than Cyc49 [38.6 vs 28.1%; adjusted odds ratio (AOR) = 1.67; 95% CI = 1.01–2.75; p = 0.04] and NotCyc (38.6 vs 23.6%; AOR = 2.08; 95% CI = 1.08–4.00; p = 0.03). Pregnancy per AI was similar in Cyc49 and NotCyc cows (28.1 vs 23.6%; AOR = 1.25; 95% CI = 0.70–2.24; p = 0.45). Cows in Cyc21 had increased hazard of pregnancy up to 300 DIM compared with Cyc49 (HR = 1.52; 95% CI = 1.17–1.96; p = 0.002) and NotCyc (HR = 1.98; 95% CI = 1.41–2.78; p < 0.001). Cows in Cyc49 tended to have increased hazard of pregnancy compared with NotCyc (HR = 1.31; 95% CI = 0.96–1.77; p = 0.09). Median days to pregnancy were, respectively, 103, 147 and 173 for cows in Cyc21, Cyc49 and NotCyc groups. Cows in the Cyc21 group had decreased prevalence of subclinical endometritis compared with cows in the NotCyc group (29.9 vs 43.7%; AOR = 0.53; 95% CI = 0.29–0.97; p = 0.04); however, the prevalence did not differ from the Cyc49 group (29.9 vs 39.1%; AOR = 0.68; 95% CI = 0.41–1.14; p = 0.15). Cyc49 cows had similar prevalence of subclinical endometritis compared with NotCyc cows (AOR = 0.77; 95% CI = 0.46–1.29; p = 0.32). Early postpartum ovulation was associated with improved uterine health and fertility.     

Inhibitory Effects of Pergolide and Cabergoline Formulations on Daily Plasma Prolactin Concentrations in Geldings and on the Daily Prolactin Responses to a Small Dose of Sulpiride in Mares

Two experiments were conducted to assess the efficacy and duration of action of two dopaminergic compounds, pergolide and cabergoline, on daily prolactin secretion in geldings and on prolactin responses to a small dose of sulpiride over 10 days. In the first experiment, oral administration of 2 mg of pergolide was compared to a single injection of 2 mg of pergolide in a slow-release vehicle and a single injection of 5 mg of cabergoline in slow-release vehicle. Controls received vehicle only. All drug treatments reduced (P < .05) prolactin concentrations relative to that in controls but differed substantially in duration of action (oral pergolide approximately 6 hours or less, injected pergolide 6 to 24 hours, and injected cabergoline at least 6 days). In the second experiment, repeated small doses of sulpiride (2 μg/kg of body weight intravenously) were used to stimulate prolactin release in mares, and the ability of seven daily injections of pergolide (2 mg each) and a single injection of cabergoline (5 mg) in slow-release vehicle to suppress this release were compared. Control mares receiving vehicle injections had robust prolactin responses to the sulpiride injections on all days of injection (days 1, 0, 1, 2, 3, 4, 6, 8, and 10 relative to treatment). Prolactin responses were muted (P < .05) by pergolide and cabergoline treatments on the first day of injection (day 0, 30 min after treatment) and were basically absent on days 1 to 8. The single injection of cabergoline continued to be suppressive through day 10, whereas mares previously treated with pergolide (through day 6) had begun to recover a prolactin response by day 10. We conclude that either daily 2-mg pergolide injections in slow-release vehicle or a single injection of 5 mg of cabergoline in slow-release vehicle is an effective way to apply dopaminergic activity to horses for approximately 7 to 10 days and may have application in the treatment of pituitary pars intermedia dysfunction in affected horses.     

过瘤胃葡萄糖对泌乳早期奶牛产奶量和乳汁成分的影响

选取产后10～15d,年龄、胎次、产奶量相近,年产奶量大于6t的荷斯坦奶牛24头,随机分为4组,每组各6头.Ⅰ、Ⅱ、Ⅲ组分别在基础日粮中每头每天添加200,300和400g过瘤胃葡萄糖,Ⅳ组为对照组,饲喂基础日粮.过瘤胃葡萄糖分早、晚2次混于精料中,任其自由采食,饲喂期20d.通过对试验奶牛在饲喂前、饲喂后10d和20d的产奶量、乳汁成分的分析.结果显示,与对照组比较,Ⅰ组产奶量极显著升高(P<0.01);乳脂肪、乳蛋白、乳糖水平均不显著(P>0.05).表明过瘤胃葡萄糖能提高奶牛泌乳性能.     

Effect of Estradiol and Progesterone on Metabolic Biomarkers in Healthy Bitches

The aim of this study was to evaluate the possible association between hormonal changes that occur during oestrus and biomarkers related with glucose metabolism (glucose and insulin), lipid metabolism (lipidic profile and BChE) and adipokines (adiponectin and ghrelin) in healthy bitches. For this purpose, we measured these analytes in serum of bitches, at two times: before (T1) and after (T2) the LH peak that were established according to progesterone concentrations. Increased levels of total cholesterol (p < 0.01), high density lipoprotein cholesterol (HDL‐C) (p < 0.01), low density lipoprotein cholesterol (LDL‐C) (p < 0.01), adiponectin (p < 0.01) and ghrelin (p < 0.05) were observed at T2 in comparison with T1. No statistically significant changes were observed in serum glucose, insulin, homoeostasis model assessment for insulin sensitivity (HOMA), triglycerides and BChE. When all data of T1 and T2 were pooled, serum adiponectin showed positive correlation with progesterone (r = 0.353; p = 0.022) and HDL‐C (r = 0.307; p = 0.048), and negative with insulin (r = ?0.429; p = 0.005), HOMA (r = ?0.446; p = 0.003) and BChE (r = ?0.522; p < 0.001). Ghrelin showed negative correlation with estradiol (r = ?0.701; p = 0.004). BChE was negatively correlated with estradiol (r = ?0.441; p = 0.018) and glucose (r = ?0.343; p = 0.028), and positively with insulin (r = 0.460; p = 0.003) and HOMA (r = 0.505; p < 0.001). In conclusion, changes in metabolic biomarkers occur in bitches after LH peak, characterized by increased lipids (total cholesterol, HDL cholesterol and LDL cholesterol) without changes in BChE activity, and increased adiponectin and ghrelin concentrations, without significant changes in glucose and insulin.     

Establishment of an ELISA for Measuring Bovine Pregnancy-Associated Glycoprotein in Serum or Milk and Its Application for Early Pregnancy Detection

It has been shown in several mammalian species that during pregnancy, trophoblast cells express a range of pregnancy-associated glycoproteins (PAG). The presence of PAG in the maternal serum of cows may serve as an indicator of pregnancy from day 28 after AI onward. The present study addresses (1) conversion of an existing PAG-RIA to a competitive double antibody ELISA using a polyclonal anti-bPAG-IgG and an anti-rabbit-IgG raised in sheep for coating and (2) application of newly established ELISA to test its suitability for pregnancy detection by measuring PAG in serum or milk. The intraassay coefficients of variation (CV) for the PAG-ELISA were 2–14% for serum and 10–12% for milk; the corresponding interassay CVs were 8–22% and 12–22%, respectively. Pregnancy-associated glycoprotein profiles established in milk and serum of 12 pregnant cows showed a characteristic pattern with measurable amounts from approximately day 20 onwards in serum and from day 60 onwards in milk. In a field trial, serum PAG was determined in 397 cows sampled between 20 and 50 days after insemination. The outcome was that, pregnancy could reliably be diagnosed from day 28 onwards in serum and from day 150 onwards in milk. In conclusion, it may be stated that the established ELISA provides an efficient and reliable means of pregnancy diagnosis that will, in our judgement, gain in popularity with cattle breeding. The ELISA proved to be an adequate and efficient way of measuring PAG in maternal serum or milk and will be a useful means of pregnancy detection in cows.     

催乳素对奶牛乳腺上皮细胞乳脂和乳蛋白合成相关基因表达的影响

本试验旨在探讨催乳素对奶牛乳腺上皮细胞(BMECs)乳脂和乳蛋白合成相关基因表达的影响。选取中国荷斯坦奶牛BMECs为试验材料,经纯化培养后,培养基中添加不同浓度催乳素[0(对照)、100、300、500和1 000 ng/m L],继续培养24 h。通过四甲基偶氮唑盐(MTT)比色法检测细胞活力;利用试剂盒检测胞内甘油三酯的含量;采用实时定量PCR法检测乳脂和乳蛋白合成相关基因的表达。结果表明:1)催乳素浓度为100、300 ng/m L时,BMECs相对增殖率显著高于对照组与其他试验组(P0.05)。2)与对照组相比,300 ng/m L催乳素能够显著提高BM ECs乙酰辅酶A羧化酶(ACC)、二酰甘油酰基转移酶(DG AT)、脂肪酸结合蛋白3(FABP3)基因表达量及甘油三酯的含量(P0.05),硬脂酰辅酶A去饱和酶(SCD)、过氧化物酶体增殖物激活受体γ(PPARγ)基因表达量有增加的趋势。3)与对照组相比,100、300 ng/m L催乳素能够显著提高哺乳动物雷帕霉素靶蛋白(m TOR)、催乳素受体(PRLR)基因表达量(P0.05);300 ng/m L催乳素能显著提高αS1酪蛋白(CSN1 S1)基因表达量(P0.05)。综上所述,100~300 ng/m L的催乳素对BM ECs乳脂和乳蛋白合成有较好的促进效果。     

盐藻粉对奶牛产奶性能与血清免疫球蛋白的影响

为了探讨盐藻粉对奶牛产奶性能免疫机能的影响,试验选择处于泌乳中期的健康荷斯坦奶牛18头分为对照组、1.5倍VA(165IU/kg)组和盐藻粉组进行饲喂试验。结果表明,日粮中添加盐藻粉或1.5倍VA对奶牛的产奶性能有一定促进效果,盐藻粉组优于1.5倍VA组;添加盐藻粉可显著降低乳中体细胞数,血清IgG抗体和IgM抗体浓度也有明显增加的趋势;添加1.5倍VA也可显著降低乳中体细胞数,血清IgG抗体浓度有明显升高的趋势。     

盐藻粉对奶牛产奶性能与血清免疫球蛋白的影响

为了探讨盐藻粉对奶牛产奶性能免疫机能的影响,试验选择处于泌乳中期的健康荷斯坦奶牛18头分为对照组、1.5倍VA( 165 IU/kg)组和盐藻粉组进行饲喂试验.结果表明,日粮中添加盐藻粉或1.5倍VA对奶牛的产奶性能有一定促进效果,盐藻粉组优于1.5倍VA组;添加盐藻粉可显著降低乳中体细胞数,血清IgG抗体和IgM抗体浓度也有明显增加的趋势;添加1.5倍VA也可显著降低乳中体细胞数,血清IgG抗体浓度有明显升高的趋势.     

盐藻粉对奶牛产奶性能与血清免疫球蛋白的影响

为了探讨盐藻粉对奶牛产奶性能免疫机能的影响,试验选择处于泌乳中期的健康荷斯坦奶牛18头分为对照组、1.5倍VA（165IU/kg）组和盐藻粉组进行饲喂试验。结果表明,日粮中添加盐藻粉或1.5倍VA对奶牛的产奶性能有一定促进效果,盐藻粉组优于1.5倍VA组;添加盐藻粉可显著降低乳中体细胞数,血清IgG抗体和IgM抗体浓度也有明显增加的趋势;添加1.5倍VA也可显著降低乳中体细胞数,血清IgG抗体浓度有明显升高的趋势。     

A Field Study of Serum,Colostrum, Milk Iodine,and Thyroid Hormone Concentrations in Postpartum Draft Mares and Foals

Iodine, thyroxine (T4) and triiodothyronine (T3) are required for normal fetal growth, maturation, and neonatal survival. There is a lack of robust information on iodine levels found in colostrum, milk, and serum of mares and foals after a healthy pregnancy. Our objective was to characterize colostrum, milk, and serum iodine levels in healthy postpartum mares and foals (n = 10) and explore relationships with thyroid hormone concentrations. Colostrum, milk, and jugular blood samples from draft breed mares and foals with an estimated average iodine daily intake of 39 mg per mare during pregnancy were obtained at Day 0 (foaling date) and/or 10 days later. Parameters studied were (1) mare basal concentrations of serum: TT3, TT4, and iodine; (2) iodine in colostrum at Day 0 and milk iodine (Day 10); and (3) foal basal: TT3, TT4, and serum iodine (Days 0 and 10). Median ± median error colostrum iodine levels (165 ± 15.1 μg/L) were higher than milk (48 ± 5.6 μg/L; P = .007) levels. Median ± median error foal serum iodine (268.5 ± 7.6 μg/L), TT4 (1,225 ± 47.8 nmol/L), and TT3 (14.2 ± 1.1 nmol/L) at foaling date were higher than at 10 days (serum iodine: 70 ± 3.6 μg/L; TT4: 69.6. ± 20.4 nmol/L; and TT3: 5.4 ± 0.3 nmol/L). In conclusion, equine mammary tissue concentrates iodine beyond plasma levels, making colostrum and milk a significant source of iodine. Foal serum iodine levels are high in the neonatal period and are positively correlated with TT4, which is important for neonatal adaptation.     

米非司酮对早孕猕猴孕酮和雌二醇分泌的研究

为开展生殖生物学研究工作提供理想的动物模型。进行了本项试验,分析了米非司酮(ＲＵ４８６)对猕猴妊娠早期血清中孕酮(Ｐ)和雌二醇(Ｅ２)的影响。结果表明,注射ＲＵ４８６－段时间内孕酮和雌二醇基本不交,但Ｅ２/Ｐ比值有所增加,说明米非司酮干扰内分泌激素之间的平衡,随着出血的发生,孕酮、雌二醇均显著下降。这种降低与出血的发生有着明确的先后关系,从而证实了激素的变化源于蜕膜受损。     

轻音乐对奶牛产奶量及血液激素水平的影响

本试验旨在探讨轻音乐对奶牛产奶量及血液激素水平的影响。选取产奶量、年龄、胎次、泌乳期相近的荷斯坦泌乳牛32头,随机分成2组,每组16头。试验组于早、中、晚3次给料时间各播放轻音乐2 h,轻音乐选用理查德·克莱德曼的经典钢琴曲20首,对照组常规饲喂。预试期7 d,正试期60 d。正试期当天起(0 d),每隔10 d测定单产1次并采集血样1次。结果表明,试验组产奶量在第10、40天时显著高于对照组(P<0.05);试验组产奶量在第20、30、50、60天时高于对照组,差异均不显著(P>0.05);整个试验期,试验组平均产奶量较对照组高1.72 kg,差异极显著(P<0.01)。整个试验期,轻音乐能提高奶牛血液中γ-氨基丁酸(GABA)、生长激素(GH)含量,降低血液中皮质醇(COR)、五羟色胺(5-HT)含量,差异均不显著(P>0.05)。综上所述,轻音乐可通过提高奶牛血液中γ-氨基丁酸含量,促进生长激素的分泌,降低皮质醇、五羟色胺的含量,稳定奶牛情绪,从而降低奶牛应激反应,提高产奶量。     

温湿指数(THI)对荷斯坦牛产奶量影响的研究

本试验主要研究了温湿指数(THI)对奶牛产奶量的影响,同时分析了温湿指数对奶牛的受胎率和健康(子宫炎、乳房炎发病率)方面的影响。试验表明:产奶量随温湿指数的增大而下降;平均温湿指数与平均产奶量为负相关,相关系数r=0.8478;随着温湿指数的不断上升,奶牛的受胎率明显下降,乳房炎、子宫炎等疾病的发病率有上升趋势。     

Effect of dose and route of administration of thyroid releasing hormone (TRH) on the concentration of prolactin (PRL) and thyroxine (T4) in cyclic gilts

Our objective was to examine the ability of thyroid releasing hormone (TRH) to stimulate not only the release of the thyroid hormones, but also prolactin (PRL) in the female pig. An experiment was conducted to determine the effect of dose and route of administration of TRH on the concentration of PRL and thyroxine (T4) in cyclic gilts. Six gilts were injected with 0, 5, 25, 125, and 625 micrograms TRH and fed 0, 5, 2.5, 12.5 and 62.5 mg TRH. Gilts received TRH once daily. During the 10-day treatment period, route of TRH administration alternated between i.v. injection and feeding. The dose of TRH progressed from the lowest to the highest. Blood samples were taken prior to TRH injection and thereafter at 15-min intervals for 3 hr. Sampling continued for an additional 3 hr at 30-min intervals when TRH was fed. Concentrations of PRL and T4 were determined by radioimmunoassay. Intravenous injection of gilts with 125 and 625 micrograms TRH resulted in an increase in PRL from 0 to 15 min (P less than .05). All doses of TRH given i.v. elevated T4 over a 2-hr period (P less than .01). TRH failed to increase PRL when TRH was fed (P greater than .5). The feeding of 62.5 mg TRH elevated T4 from 0 to 6 hr (P less than .01). Thus, TRH injection increased PRL rapidly and T4 gradually. When TRH was fed, only a gradual elevation in T4 was observed. We conclude that TRH can elicit the release of both PRL and T4 in the cyclic gilt, but magnitude and duration of the PRL and T4 response depends on the dose and route of TRH administration.