Effects of supplemental vitamin E during the laying period on the reproductive performance of Taiwan native chickens

1. One-day-old Taiwan Native Breeder female chicks were fed on maize/soybean growing diets without supplemental vitamin E from hatch to 17 weeks of age. After 17 weeks the birds (n = 300) were randomly assigned to 5 dietary treatments and fed on maize/soybean laying diets supplemented with 0, 40, 80, 120 and 160 mg/kg of vitamin E (dl-alpha-tocopherol acetate), respectively, until 46 weeks of age. The variates measured included: age at first egg, feed consumption (FC), feed efficiency (FE), egg production (EP), egg weight (EW), egg specific gravity (ESG), eggshell strength (ESS), fertility and hatchability. 2. The addition of 120mg/kg of vitamin E lowered the first EW (P<0.05); however, there was no significant difference in the age or body weight (BW) of pullets at first egg or mortality rate to 46 weeks of age among the treatments. FE and egg mass were improved (P<0.05) in pullets fed 80 mg/kg of supplemental vitamin E. A significant increase in EP was observed after peak EP in pullets given 80 mg/kg of supplemental vitamin E. However, this favourable effect decreased as supplemental vitamin E exceeded 80 mg/kg. 3. From 17 to 46 weeks of age, egg quality (ESG and ESS) decreased with age. However, there was no correlation between age and fertility or hatchability during the experimental period, suggesting that egg quality is more age-sensitive than reproductive performance for breeder pullets. 4. Compared with the control, fertility and hatchability of all eggs set for the treatment with 80 mg/kg supplemental vitamin E increased by 7.7 and 13.4%, respectively. There was no difference in the hatchability of fertile eggs. 5. These results suggest that using supplemental vitamin E during the laying period can improve the reproductive performance of breeder pullets. The addition of 80 mg/kg of vitamin E obtained the best performance in EP, egg mass, FE (feed/egg), hatchability and fertility.     

饲粮代谢能水平对汶上芦花产蛋鸡生产性能、血清生化指标和蛋品质的影响

本试验旨在研究饲粮代谢能(ME)水平对产蛋期汶上芦花鸡生产性能、血清生化指标和蛋品质的影响,并建立代谢能需要量析因模型,确定产蛋期汶上芦花鸡的饲粮代谢能需要量。试验采用单因素完全随机设计,选取40周龄、体重相近的健康汶上芦花鸡360只,随机分为5个组,每组6个重复,每个重复12只鸡。各组分别饲喂代谢能水平为10.68、10.89、11.10、11.30和11.51MJ/kg的试验饲粮,其他主要营养水平保持一致。预试期7d,试验期35d。结果表明:1)饲粮代谢能水平对产蛋期汶上芦花鸡的平均日采食量(ADFI)、平均日代谢能摄入量(ADMEI)、平均体重、代谢体重(BW0.75)、产蛋数、产蛋率和平均日产蛋量(ADEM)均有显著影响(P0.05)。随饲粮代谢能水平的升高,ADFI、ADMEI、产蛋数、产蛋率和ADEM呈增加趋势,但当代谢能水平为11.51 MJ/kg时降低。随饲粮代谢能水平的升高,料蛋比呈降低趋势,但当代谢能水平为11.51 MJ/kg时增加。饲粮代谢能水平为11.51和11.30 MJ/kg时的平均体重和BW0.75显著高于代谢能水平为11.10 MJ/kg时(P0.05)。2)随饲粮代谢能水平的升高,产蛋期汶上芦花鸡的血清葡萄糖(GLU)、甘油三酯(TG)和总胆固醇(TCHO)含量均呈增加趋势。3)饲粮代谢能水平对产蛋期汶上芦花鸡的蛋白高度、蛋黄颜色、哈氏单位和蛋黄比率有显著影响(P0.05)。低能组(代谢能水平为10.68、10.89和11.10 MJ/kg)的蛋白高度和哈氏单位显著高于高能组(代谢能水平为11.30和11.51 MJ/kg)(P0.05)。随饲粮代谢能水平的升高,蛋黄颜色和蛋黄比率呈增加趋势,其中代谢能水平为11.51 MJ/kg时的蛋黄颜色和蛋黄比率显著高于其他各代谢能水平时(P0.05)。4)以ADMEI为因变量,以平均日增重(ADG)、ADEM和BW0.75为自变量,拟合41~45周龄汶上芦花鸡饲粮代谢能需要量的析因模型为:ADMEI=0.88 ADG+10.63 ADEM+476.40 BW0.75(R2=0.982 5,P0.05)。满足41~45周龄汶上芦花鸡最佳生产性能的适宜饲粮代谢能需要量为11.29 MJ/kg。     

Effect of dose and frequency of administration of a potent analog of human growth hormone-releasing factor on hormone secretion and growth in pigs

Ninety-six pigs (49.5 +/- .5 kg BW) were allotted to six treatments and were injected once (SID) or three times daily (TID) s.c. with a [desamino-Tyr1, D-Ala2, Ala15] human growth hormone-releasing factor (1-29) NH2 analog (GRF-AN). Treatments were T1, noninjected control; T2, saline-injected control (TID); T3, GRF-AN (1.66 micrograms/kg BW, TID); T4, GRF-AN (3.33 micrograms/kg BW, TID); T5, GRF-AN (6.66 micrograms/kg BW, TID) and T6, GRF-AN (10 micrograms/kg BW, SID). Feed protein levels were 14% for T1 and 18.8% for T2 through T6. The GRF-AN increased serum growth hormone (GH) concentration for the entire growing period (about 56 d) in a dose-related manner and did not induce desensitization of the somatotroph cells; in fact, an increase (P less than .05) in the GH response to GRF-AN was observed in T4 and T5 after 1 mo of treatment. This GRF-AN produced (P less than .05) a dose-dependent effect on several variables in animals grown to 110 kg BW: in comparison to T2, T5 increased meat in carcass (6%), carcass length (3%), loin eye area (13%), liver weight (19%), kidney weight (30%), improved feed efficiency (20%) and decreased total feed intake by 50 kg (26%). Compared to T2, average daily gain was increased (P less than .05) by 13% by the 3.33 micrograms/kg TID dose. Blood parameters were measured on d 1, 29 and 57. Increased serum glucose and insulin levels were observed. Triiodothyronine and thyroxine concentrations were increased and decreased, respectively after 28 d of treatment but were unchanged on d 57. This potent GRF analog maintained high GH concentration for at least 56 d and affected several growth parameters and carcass characteristics in a dose-related manner similar in magnitude to that reported in studies using porcine GH.     

Relationships among LH, FSH and prolactin secretion, storage and response to secretagogue and hypothalamic GnRH content in ovariectomized pony mares administered testosterone, dihydrotestosterone, estradiol, progesterone, dexamethasone or follicular fluid

Thirty-five ovariectomized pony mares were used to study the relationships among luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL) concentrations in blood (secretion), in pituitary (storage) and in blood after secretagogue administration, as well as the content of gonadotropin releasing hormone (GnRH) in hypothalamic areas, under various conditions of steroidal and nonsteroidal treatment. Five mares each were treated daily for 21 d with vegetable shortening (controls), testosterone (T; 150 micrograms/kg of body weight, BW), dihydrotestosterone (DHT; 150 micrograms/kg BW), estradiol (E2; 35 micrograms/kg BW), progesterone (P4; 500 micrograms/kg BW), dexamethasone (DEX; 125 micrograms/kg BW) or charcoal-stripped equine follicular fluid (FF; 10 ml). Secretagogue injections (GnRH and thyrotropin releasing hormone, TRH, at 1 and 4 micrograms/kg of BW, respectively) were given one d prior to treatment and again after 15 d of treatment. Relative to controls, treatment with T, DHT and DEX reduced (P less than .05) LH secretion, storage and response to exogenous GnRH, whereas treatment with E2 increased (P less than .05) these same characteristics. Treatment with P4 reduced (P less than .05) only LH secretion. Treatment with T, DHT, E2 and DEX reduced (P less than .05) FSH secretion, whereas treatment with P4 increased (P less than .05) it and FF had no effect (P greater than .1). All treatments increased (P less than .05) FSH storage, whereas only treatment with T and DHT increased (P less than .05) the FSH response to exogenous GnRH. Other than a brief increase (P less than .05) in PRL secretion in mares treated with E2, secretion of PRL did not differ (P greater than .1) among groups. Only treatment with E2 increased (P less than .01) PRL storage, yet treatment with T or DHT (but not E2) increased (P less than .05) the PRL response to exogenous TRH. Content of GnRH in the body and pre-optic area of the hypothalamus was not affected (P greater than .1) by treatment, whereas treatment with T, E2 and DEX increased (P less than .1) GnRH content in the median eminence. For LH, secretion, storage and response to exogenous GnRH were all highly correlated (r greater than or equal to .77; P less than .01). For FSH, only storage and response to exogenous GnRH were related (r = .62; P less than .01). PRL characteristics were not significantly related to one another. Moreover, the amount of GnRH in the median eminence was not related (P greater than .1) to any LH or FSH characteristic.     

Effect of Energy and Protein on Performance,Egg Components,Egg Solids,Egg Quality,and Profits in Molted Hy-Line W-36 Hens

An experiment was conducted to determine the influence of dietary energy on performance, egg composition, egg solids, egg quality, and profits of Hy-Line W-36 hens fed different protein levels. The experiment was designed as a 4 × 3 factorial arrangement with 4 added dietary energy levels (0, 79, 158, and 238 kcal of ME/kg) and 3 protein levels (14.89, 16.06, and 17.38%). The basal diets of 17.38, 16.06, and 14.89% protein contained 2,751, 2,784, and 2,815 kcal of ME/kg, respectively. This study lasted 12 wk. Molted Hy-Line W-36 hens (n = 1,440) in phase 1 (70 wk of age) were randomly divided into 12 treatments (8 replicates of 15 hens per treatment). Protein had a significant effect on egg production, egg mass, feed intake, feed conversion, egg weight, percentage of egg shell components, yolk color, and yolk and albumen weight. As dietary energy increased from 0 to 238 kcal of ME/kg by addition of poultry oil, feed intake linearly decreased. Increasing dietary energy also significantly increased BW and egg yolk color. As dietary energy increased, percentage yolk solids increased at the 2 greater dietary protein levels, whereas egg-specific gravity linearly decreased at the 17.38% protein level. Increasing dietary energy and protein significantly improved feed conversion. Increasing protein intake significantly increased albumen and yolk weight but had no influence on yolk, albumen, or whole egg solids. Because feed ingredient and egg prices vary, there can be no fixed ideal dietary energy level for optimal profits during molt phase 1 (70 to 81 wk).     

饲粮添加维生素E和酵母硒对黄羽肉种鸡产蛋性能、孵化性能及蛋中维生素E和硒沉积量的影响

本试验旨在研究饲粮添加维生素E和酵母硒对黄羽肉种鸡产蛋性能、孵化性能及蛋中维生素E和硒(Se)沉积量的影响。试验采用3×3双因子设计,设3个维生素E添加水平(0、20、40 IU/kg)和3个Se添加水平(0、0.15、0.30 mg/kg)。选用32周龄快大型岭南黄羽肉鸡父母代种母鸡864只,根据产蛋率和体重一致性原则随机分成9个组,分别为VE_0Se_0组、VE_0Se_(0.15)组、VE_0Se_(0.30)组、VE_(20)Se_0组、VE_(20)Se_(0.15)组、VE_(20)Se_(0.30)组、VE_(40)Se_0组、VE_(40)Se_0.15组和VE_(40)Se_0.30组,每组6个重复,每个重复16只鸡。试验期8周。结果表明:1)饲粮中维生素E和Se添加水平对黄羽肉种鸡的体增重、平均日产蛋量、料蛋比、平均蛋重、产蛋率、破蛋率和不合格蛋率均无显著影响(P0.05)。2)饲粮中维生素E和Se添加水平对黄羽肉种鸡的蛋长径、蛋短径、蛋白高度、蛋黄颜色、哈氏单位、蛋黄重、蛋壳重和蛋壳厚度均无显著影响(P0.05)。3)饲粮中维生素E和Se添加水平对黄羽肉种鸡的健雏出壳重、孵化率、弱雏率和受精率均无显著影响(P0.05)。4)饲粮中维生素E添加水平对黄羽肉种鸡血浆MDA含量有显著影响(P0.05),随饲粮中维生素E添加水平的升高血浆MDA含量呈降低趋势,其中维生素E添加水平为40 IU/kg时血浆MDA含量显著低于0 IU/kg时(P0.05);饲粮中维生素E和Se添加水平对血浆MDA含量有显著交互作用(P0.05),其中VE_(40)Se_0组的血浆MDA含量显著低于VE_0Se_(0.15)和VE_0Se_(0.30)组(P0.05)。5)随饲粮中维生素E和Se添加水平的升高,黄羽肉种鸡蛋中维生素E和Se含量显著增加(P0.05);饲粮中维生素E和Se添加水平对蛋中维生素E和Se含量有显著交互作用(P0.05)。结果提示,维生素E可以提高黄羽肉种鸡的抗氧化水平,饲粮中维生素E和Se添加水平可以显著影响蛋中维生素E和Se的含量;建议在无任何应激因素刺激和不使用Se缺乏地区饲料原料的情况下,黄羽肉种鸡玉米-豆粕型饲粮可以不用额外添加维生素E和Se。     

N-methyl-d,l-aspartate stimulates growth hormone and prolactin but inhibits luteinizing hormone secretion in the pig.

The effects of n-methyl-d,l-aspartate (NMA), a neuroexcitatory amino acid agonist, on luteinizing hormone (LH), prolactin (PRL) and growth hormone (GH) secretion in gilts treated with ovarian steroids was studied. Mature gilts which had displayed one or more estrous cycles of 18 to 22 d were ovariectomized and assigned to one of three treatments administered i.m.: corn oil vehicle (V; n = 6); 10 micrograms estradiol-17 b/kg BW given 33 hr before NMA (E; n = 6); .85 mg progesterone/kg BW given twice daily for 6 d prior to NMA (P4; n = 6). Blood was collected via jugular cannulae every 15 min for 6 hr. Pigs received 10 mg NMA/kg BW i.v. 2 hr after blood collection began and a combined synthetic [Ala15]-h GH releasing factor (1-29)-NH2 (GRF; 1 micrograms/kg BW) and gonadotropin releasing hormone (GnRH; .2 micrograms/kg BW) challenge given i.v. 3 hr after NMA. NMA did not alter LH secretion in E gilts. However, NMA decreased (P < .02) serum LH concentrations in V and P4 gilts. Serum LH concentrations increased (P < .01) after GnRH in all gilts. NMA did not alter PRL secretion in P4 pigs, but increased (P < .01) serum PRL concentrations in V and E animals. Treatment with NMA increased (P < .01) GH secretion in all animals while the GRF challenge increased (P < .01) serum GH concentrations in all animals except in V treated pigs. NMA increased (P < .05) cortisol secretion in all treatment groups. These results indicate that NMA inhibits LH secretion and is a secretagogue of PRL, GH and cortisol secretion with ovarian steroids modulating the LH and PRL response to NMA.     

绍兴鸭剩余采食量与部分生产性能及蛋品质的相关性分析

本实验旨在探讨绍兴鸭剩余采食量(RFI)与生产性能及蛋品质之间的关系。测定300只绍兴鸭410~470日龄的采食量、体重、平均蛋重、蛋品质,计算出剩余采食量与料蛋比,并分析剩余采食量与生产性能及蛋品质的相关性。结果显示:绍兴鸭平均采食量、平均蛋重、体重、体增重、料蛋比、剩余采食量分别为198.8 g/d、73.0 g、1500.9 g、2.5 g/d、2.7、3.5 g/d;低剩余采食量组的剩余采食量、采食量以及料蛋比极显著低于高剩余采食量组;相关性分析表明,剩余采食量与采食量和料蛋比呈极显著正相关(P<0.01);采食量与平均蛋重、体重呈极显著正相关(P<0.01),与料蛋比呈极显著负相关(P<0.01),与体增重呈显著正相关性(P<0.05);蛋品质分析结果表明,高剩余采食量组仅蛋黄色泽水平显著高于低剩余采食量组;相关性分析表明,剩余采食量与蛋品质各指标间均无显著相关性。本试验结果表明,以剩余采食量为蛋鸭选育指标是可行的,且选育低剩余采食量的鸭子能显著降低采食量,提高饲料效率,且不改变产蛋重及蛋品质。     

Exogenous human growth hormone-releasing factor and ovine somatotropin improve growth performance and composition of gain in lambs

The objectives of this study were 1) to compare intermittent subcutaneous administration of human growth hormone-releasing factor (hGRF) at two doses with a similar regimen of ovine somatotropin (oST) for effects on growth and composition of gain in growing lambs and 2) to determine whether increasing the dietary amino acid availability enhances response to oST or hGRF. Eighty crossbred ewe and wether lambs (25.5 kg live weight) were assigned randomly in pairs to receive four daily injections of excipient, 40 micrograms oST/kg BW, 5 micrograms hGRF/kg BW or 10 micrograms hGRF/kg BW for 42 (n = 80) or 56 (n = 40) d. Doses were adjusted weekly for BW. Mean plasma oST concentrations increased from 2.03 ng/ml prior to treatment to 20.64, 4.80 and 5.45 ng/ml with oST, 5 and 10 micrograms/kg hGRF doses, respectively. Lambs did not become refractory to hGRF. Cumulative gain increased approximately 18% with 7 wk of treatment with oST and the low dose of hGRF (both P less than .01), and feed efficiency improved 21% with oST and 18% with both doses of hGRF (both P less than .05). Carcass lipid accretion rate decreased 22% to 30% (P less than .001), and carcass protein accretion rate increased 30% to 36% (P less than .001) with hGRF and oST treatment, respectively. Addition of fishmeal to the diet at 4% to replace an equal amount of soy protein improved gain 8.5%; it improved efficiency 14.2% (P less than .05) across all treatments, and it significantly enhanced the effects of oST on feed efficiency (interaction P less than .12) and hind leg muscle weights.     

The effects of different iodide availabilities on thyroid function during development in Japanese quail

Japanese quail (Coturnix japonica) were used to study the effects of different egg iodide (I) availabilities on thyroid function during development. Low (less than 50 micrograms 1/kg feed in the maternal diet) and high (1200 micrograms 1/kg feed) I availability were compared to control levels (800 micrograms 1/kg feed), a standard supplementation for game bird feed. We measured thyroid gland content of I, triiodothyronine (T3) and thyroxine (T4), plasma concentrations of T3 and T4, hepatic 5' monodeiodinase (5'-D) activity, and the response of the thyroid gland to thyrotrophin (TSH) stimulation. Embryos, on day 14 of the 16.5-17 day incubation period, and 1-day chicks were used for most studies but thyroid gland hormone content and plasma hormone concentrations were determined for more stages. With high I, thyroidal I content was elevated but thyroidal T4 and T3 were not different from controls. Plasma T3 and T4, the thyroid gland response to TSH stimulation, and hepatic 5'-D activity did not differ between control and high I. Reduced body weight occurred with high I. In general, thyroid gland weight was not altered, but some high I birds exhibited thyroid hypertrophy and altered thyroid gland function. With low I availability, thyroid gland contents of I and T4 were reduced but thyroidal T3 content was maintained. The thyroid gland response to TSH stimulation, plasma thyroid hormone concentrations, and the developmental patterns of plasma thyroid hormones, hepatic 5'-D activity, body weight and thyroid weight were not different between control and low I groups. Developing Japanese quail exhibit excellent ability to adjust thyroid function over a wide range of I availabilities. Regulation appears to occur at the level of thyroid hormone synthesis in the thyroid gland, which allows most aspects of thyroid dynamics to remain unchanged in the maintenance of circulating thyroid hormone concentrations.     

Stimulation of pig growth performance by porcine growth hormone: determination of the dose-response relationship

The present study was undertaken to determine the relationship between dose of porcine growth hormone (pGH) and growth performance of pigs. Porcine GH was administered daily for 35 d [buffer-injected control = (C); 10 micrograms/kg body weight (BW) = (L); 30 micrograms/kg BW = (M); 70 micrograms/kg BW = (H)] to barrows (initial wt = 50 kg). Growth rate was significantly increased by pGH (14% for H dose vs C). Feed efficiency was increased in a dose-related manner (L = 7%, M = 10%, H = 17%) by pGH. There was a concurrent change in carcass composition of pGH-treated pigs. The H dose of pGH decreased the percentage of carcass lipid by 25% (P less than .05). Muscle mass was significantly increased in H vs C pigs (31 vs 26 kg). Serum insulin-like growth factor 1 (IGF-1) concentration increased in a manner that was linearly related to the pGH dose (r = .87). No antibodies to pGH were detected in any of the pigs. In summary, these results extend our earlier findings that pGH increases growth performance markedly. Based on the present findings it appears that the maximally effective dose of pGH is greater than 70 micrograms.kg BW-1.d-1 since several indices of the growth-promoting and metabolic effects of pGH (% carcass protein, % carcass lipid and feed efficiency) had not plateaued.     

Effect of dietary energy,protein, and a versatile enzyme on hen performance,egg solids,egg composition,and egg quality of Hy-Line W-36 hens during second cycle,phase two

This study was conducted to evaluate the effect of Rovabio, dietary energy, and protein on performance, egg composition, egg solids, and egg quality of commercial Leghorns in phase 2, second cycle. A 4 × 2 × 2 factorial arrangement of treatments comprising 4 dietary energy levels (2,791, 2,857, 2,923, and 2,989 kcal of ME/kg) and 2 protein levels (15.5 and 16.1%) with and without Rovabio was used. Hy-Line W-36 hens (n = 1,920, 87 wk old) were randomly divided into 16 dietary treatments (8 replicates of 15 hens per treatment). The trial lasted 12 wk. Dietary protein significantly increased feed consumption but decreased yolk color. As dietary energy increased from 2,791 to 2,989 kcal of ME/kg, feed consumption decreased from 98.0 to 94.9 g per hen daily, and yolk color increased from 5.27 to 5.56. There was a significant interaction among dietary protein, energy, and Rovabio on egg production, BW, egg mass, feed conversion, and yolk solids. Egg weight of hens fed the diets supplemented with Rovabio was significantly greater than that of hens fed the diets without Rovabio during wk 3 and 4. However, Rovabio did not significantly influence average egg weight (87 to 98 wk of age). Rovabio supplementation significantly increased BW of hens. These results suggest Rovabio had a small but significant influence on nutrient utilization of commercial Leghorns during phase 2 of the second cycle.     

大豆黄酮对产蛋初期期和后期绍兴鸭产蛋性能及血清激素水平的影响

日粮中添加3mg/kg大豆黄酮分别饲喂产蛋初期和产蛋后期绍兴鸭,观察其对产蛋性能、血清GH、IGP-1和E2水平的影响.结果表明,产蛋初期添加大豆黄酮显著降低绍兴鸭产蛋率和平均蛋重,饲料转化率下降,并伴随有血清GH水平显著降低.相反,产蛋后期添加大豆黄酮,绍兴鸭产蛋率和平均蛋重均显著增加,血清GH水平也明显提高.无论在产蛋初期还是后期添加大豆黄酮对血清IGF-1和E2水平均无显著影响.结果表明,产蛋初期添加大豆黄酮对绍兴鸭的产蛋性能具有抑制作用,而产蛋后期添加大豆黄酮可以促进绍兴鸭的产蛋性能,血清生长激素水平的相应变化提示GH可能是大豆黄酮作用途径的一个环节.     

大豆黄酮对产蛋初期和后期绍兴鸭产蛋性能及血清激素水平的影响

日粮中添加3mg/kg 大豆黄酮分别饲喂产蛋初期和产蛋后期绍兴鸭 ,观察其对产蛋性能、血清GH、IGP -1和E2 水平的影响。结果表明 ,产蛋初期添加大豆黄酮显著降低绍兴鸭产蛋率和平均蛋重 ,饲料转化率下降 ,并伴随有血清GH水平显著降低。相反 ,产蛋后期添加大豆黄酮 ,绍兴鸭产蛋率和平均蛋重均显著增加 ,血清GH水平也明显提高。无论在产蛋初期还是后期添加大豆黄酮对血清IGF -1和E2水平均无显著影响。结果表明 ,产蛋初期添加大豆黄酮对绍兴鸭的产蛋性能具有抑制作用 ,而产蛋后期添加大豆黄酮可以促进绍兴鸭的产蛋性能 ,血清生长激素水平的相应变化提示GH可能是大豆黄酮作用途径的一个环节。     

Use of growth hormone response to growth hormone-releasing hormone to determine growth potential in beef heifers.

The response of GH to GHRH at weaning is known to predict postweaning growth and body composition in beef bulls. The objective of this study was to determine whether GH response to a challenge of GHRH and plasma IGF-I can predict growth rate and body composition in the beef heifer. Growth hormone response to a challenge with two doses of GHRH was measured in 67 Angus heifers averaging 225 d of age (SD = 21) and 217 kg BW (SD = 32). Blood samples were collected at 0 and 10 min relative to an initial "clearance dose" (4.5 micrograms GHRH/100 kg BW) and again, 3 h later, relative to a challenge dose (1.5 or 4.5 micrograms GHRH/100 kg BW). Each animal received each of the two challenge doses, which were randomly assigned across 2 d of blood collection. Serum GH concentration was measured by RIA. Plasma was collected every 28 d during a 140-d growth test and assayed for IGF-I by RIA. Body weight was measured every 28 d and hip height was measured at weaning and at the end of a 140-d growth test. Average daily gain was calculated on d 140 of the growth test and body composition measurements were estimated by ultrasound 2 wk after completion of the growth test. Responses to the two GHRH challenges were dose-dependent (P < 0.05). Average daily gain tended to be related to GH response to the 1.5 micrograms GHRH/100 kg BW dose (R2 = 0.05; P = 0.06), but no relationship was observed at the 4.5 micrograms GHRH/100 kg BW dose (R2 = 0.00; P = 0.93). An inverse relationship (R2 = 0.06; P = 0.02) was observed between response to the 1.5 micrograms GHRH/100 kg BW dose and intramuscular fat percentage. Mean plasma IGF-I concentration was positively associated with ADG (R2 = 0.06; P < 0.01). Growth hormone response to GHRH is modestly related to body composition but not to ADG in weanling beef heifers and likely has limited use in evaluation of growth performance in replacement beef heifers.     

维生素A、维生素C和维生素E混合物对浙东白鹅繁殖机能的影响

研究了添加VA、VC和VE混合物(1.5 kg/t饲料)对浙东白鹅繁殖性能、血浆激素浓度和下丘脑-垂体-性腺轴基因mRNA水平的影响。结果显示:饲喂维生素混合物可显著提高浙东白鹅第1产蛋周期蛋重和受精率(P<0.05),但对第2产蛋周期产蛋量、蛋重、受精率和孵化率影响有限;饲喂维生素混合物可提高浙东白鹅第2产蛋周期内血浆FSH、P4、HCG和赖抱期、恢复期E2的浓度,降低LH浓度,改变浙东白鹅产蛋周期内FSH波动规律(P<0.05),降低下丘脑内PRLR、垂体内PRL和卵巢内PRLR基因的mRNA水平(P<0.05),提高卵巢内ESR2基因的mRNA水平(P<0.05),对下丘脑内GnRH、垂体内PRL和FSHβ、卵巢内PRL、ESR1和FSHR基因的mRNA水平影响不显著。因此,VA、VC和VE混合物可以通过影响繁殖期内部分血浆激素浓度变化,下调生殖轴PRLR mRNA水平以减弱PRL信号,从而改善浙东白鹅的繁殖性能。     

Effect of long-term administration of human growth hormone-releasing factor and (or) thyrotropin-releasing factor on hormone concentrations in lactating dairy cows

Fifteen cows (87 +/- 8 d in lactation; 641 +/- 33 kg BW) were randomly assigned to treatment and then subjected for 182 d to daily sc injection (1000 hr), in the cervical area, of saline (control), thyrotropin-releasing factor (TRF: 1 micrograms/kg BW), growth hormone-releasing factor (1-29)NH2 (GRF; 10 micrograms/kg BW) or GRF plus TRF (10 and 1 micrograms/kg BW, respectively) according to a 2 x 2 factorial design. On days 1, 31, 88 and 179, jugular blood samples were collected from 2 hr before to 6 hr after injection. Samples were also collected for 5 consecutive days after cessation of treatment. GRF always induced growth hormone (GH) release (600 vs 7925 ng.min/ml) with augmentation of response with time (interaction GRF * day; P less than .001). TRF did not affect (P greater than .25) GH release; there was no interaction (P greater than .25) with time. There was no significant interaction (P greater than .25) between GRF and TRF on GH release. However, the amount of GH release with GRF plus TRF was always greater than with GRF alone (9419 vs 6431 ng.min/ml). TRF induced a significant release of prolactin (23769 vs 42175 ng.min/ml) but GRF reduced the amount of prolactin release on the last day of sampling. TRF induced thyroid stimulating hormone (TSH) release only on the first day of injection while triiodothyronine (T3) and thyroxine (T4) continued to respond to TRF throughout the treatment period. Concentrations of T3 and T4 fell below control levels after cessation of TRF injection. In conclusion, GRF-induced GH release and TRF-induced Prl and thyroid hormone release were maintained over a 6-mo treatment period. TRF induced TSH release only on the first day of injection. Overall, these results raised the possibility of a direct effect of TRF on the thyroid gland.     

Gonadotropin secretion in ovariectomized pony mares treated with dexamethasone or progesterone and subsequently with dihydrotestosterone

Twelve long-term ovariectomized (OVX) pony mares were used to determine the effects of dexamethasone (DEX) or progesterone (PR) on concentrations of follicle stimulating hormone (FSH) and luteinizing hormone (LH) in daily blood samples and after administration of gonadotropin releasing hormone (GnRH). All mares were subsequently administered dihydrotestosterone (DHT) to determine if DEX or PR treatment altered the FSH or LH response to this androgen. Daily blood sampling was started on day 1. After a pretreatment injection of GnRH on day 5, four mares were administered DEX at 125 micrograms/kg of body weight (BW), four mares were administered PR at 500 micrograms/kg of BW and four mares were administered vehicle. Injections were given subcutaneously in vegetable shortening daily through day 14. After a second injection of GnRH on day 15, all mares were administered DHT in shortening at 150 micrograms/kg of BW. Injections of DHT were given daily through day 24. A final injection of GnRH was given on day 25. Treatment of mares with DEX 1) reduced (P less than .01) daily LH secretion and briefly increased (P less than .05) daily FSH secretion and 2) increased (P less than .01) the FSH response to exogenous GnRH. Treatment of mares with PR had no effect on daily LH secretion but increased (P less than .05) daily FSH secretion and increased (P less than .01) the FSH response to exogenous GnRH.(ABSTRACT TRUNCATED AT 250 WORDS)     

大豆黄酮对肉种鸡产蛋和繁殖性能的影响

本试验旨在探索添加大豆黄酮后对肉种鸡产蛋和繁殖性能的影响。选取43周龄体况接近一致(体重、产蛋率)的肉种鸡S2系母鸡240只,随机分成4组,每组6个重复,每个重复10只:选取1组作为对照组,饲喂无大豆黄酮的基础饲粮,其余3组分别在基础饲粮基础上添加5、10、20 mg/kg大豆黄酮。再挑选20只强健的S2系公鸡采集精液,混精对试验鸡进行人工授精,试验期为15周。结果表明:与对照组相比,1)添加大豆黄酮对S2系母鸡体增重、采食量及死亡率无显著影响(P0.05)。2)添加大豆黄酮后能显著提高产蛋率(P0.05),其中10 mg/kg组产蛋率提高了4.1%(P0.05),日产蛋量提高了3.5%(P0.05),为3组最佳。5、10 mg/kg组料蛋比分别降低了8.0%和11.2%(P0.05)。3)10 mg/kg组受精率、孵化率和健雏率分别提高了13.1%、20.5%和5.8%(P0.05)。由此可见,饲粮中添加大豆黄酮能显著影响肉种鸡产蛋和繁殖性能,其中10 mg/kg组综合效果最佳。     

Effects of immunizing gilts against zearalenone on height of vaginal epithelium and urinary excretion of zearalenone

Two experiments were conducted to develop a vaginal epithelium bioassay for zearalenone (Z) and to determine whether immunization against Z would prevent Z mycotoxicosis. Eleven gilts were ovariectomized and allotted by weight to dietary doses of 50, 150 or 350 micrograms Z/kg BW daily for 3 d. All doses of Z increased height of the vaginal epithelium. Height of the vaginal epithelium in gilts fed 150 or 350 micrograms Z/kg BW increased more than that in gilts fed 50 micrograms Z/kg BW. Twenty-four gilts then were ovariectomized and allotted to be immunized or not immunized. A Z-bovine serum albumin conjugate was injected into gilts to achieve immunization. Ten weeks after initial immunization, antibodies to Z were detected after a 1:10(7) dilution at greater than .1 absorbance units using an enzyme-linked immunosorbent assay, and gilts were allotted by weight to diets with no Z or 150 micrograms Z/kg BW daily for 3 d. Immunization alone had no effect on height of vaginal epithelium, but after 3 and 10 d, immunized gilts fed Z had higher vaginal epithelium than did nonimmunized gilts fed Z. Immunized gilts excreted a larger percentage of ingested Z than nonimmunized gilts did. Therefore, immunizing gilts against Z potentiated both the estrogenic effects of Z and urinary excretion of Z equivalents.