Reproductive seasonality in the mare: neuroendocrine basis and pharmacologic control

Reproductive seasonality in the mare is characterized by a marked decline in adenohypophyseal synthesis and secretion of LH beginning near the autumnal equinox. Thus, ovarian cycles have ceased in most mares by the time of the winter solstice. Endogenous reproductive rhythms in seasonal species are entrained or synchronized as a result of periodic environmental cues. In the horse, this cue is primarily day length. Hence, supplemental lighting schemes have been used managerially for decades to modify the annual timing of reproduction in the mare. Although a full characterization of the cellular and molecular bases of seasonal rhythms has not been realized in any species, many of their synaptic and humoral signaling pathways have been defined. In the mare, neuroendocrine-related studies have focused primarily on the roles of GnRH and interneuronal signaling pathways that subserve the GnRH system in the regulatory cascade. Recent studies have considered the role of a newly discovered neuropeptide, RF-related peptide 3 that could function to inhibit GnRH secretion or gonadotrope responsiveness. Although results that used native peptide sequences have been negative in the mare and mixed in all mammalian females, new studies that used an RFRP3 antagonist (RF9) in sheep are encouraging. Importantly, despite continuing deficits in some fundamental areas, the knowledge required to control seasonal anovulation pharmacologically has been available for >20 yr. Specifically, the continuous infusion of native GnRH is both reliable and efficient for accelerating reproductive transition and is uniquely applicable to the horse. However, its practical exploitation continues to await the development of a commercially acceptable delivery vehicle.     

Effect of several supplemental Chinese herbs additives on rumen fermentation, antioxidant function and nutrient digestibility in sheep

Two experiments were carried out in this study. Experiment 1 was conducted to examine the effects of several supplemental Chinese herbs on antioxidant function and slaughtered body weight in sheep. Results indicated that Fructus Ligustri Lucidi supplementation improved the blood antioxidant function [higher concentration of glutathione reductase (GR), superoxide dismutase and lower concentration of malondialdehyde] and slaughtered body weight in sheep (p < 0.05). Experiment 2 was conducted to investigate the effect of Fructus Ligustri Lucidi extract (FLLE) on rumen fermentation and nutrient digestibility in sheep. Four levels of FLLE treatments, i.e. 0, 100, 300 and 500 mg/kg dry matter (DM), were used in this part. Addition of FLLE at 300 or 500 mg/kg DM increased total volatile fatty acid (VFA) concentration and propionate proportion, decreased ammonia-N concentration in the ruminal fluid, reduced blood urea nitrogen concentration at 2, 4, 6 and 8 h after morning feeding (p < 0.05). Addition of FLLE at all dosages had no effect on ruminal pH value and acetate concentration at all sampling time points in sheep (p > 0.05). Dynamic degradation coefficient c of maize DM was significantly increased by supplementing FLLE at 300 or 500 mg/kg DM (p < 0.05). Fructus Ligustri Lucidi extract addition had no effect on degradation coefficients a, b, c of DM and nitrogen of soybean meal; a, b of maize DM; a, b, c of maize nitrogen; and a, b, c of neutral detergent fibre (NDF) and acid detergent fibre (ADF) of Chinese wildrye (p > 0.05). Addition of FLLE at 300 or 500 mg/kg DM increased DM and organic matter digestibility of diet (p < 0.05). Fructus Ligustri Lucidi extract addition had no effect on digestibility of diet's NDF, ADF and crude protein (p > 0.05). From the aforementioned results, it is indicated that FLLE improved antioxidant status and slaughtered body weight. Fructus Ligustri Lucidi extract addition has capability to modulate rumen fermentation, increase the maize degradation rate, total volatile fatty acid concentration and propionate proportion in sheep.     

陈玉米饲粮中添加茶多酚、维生素E和二丁基羟基甲苯对肉鸭生长性能和抗氧化功能的影响

本试验旨在研究陈玉米饲粮中添加茶多酚(TP)、维生素E和二丁基羟基甲苯(BHT)对肉鸭生长性能和抗氧化功能的影响。选取1日龄雄性北京鸭192只,随机分为4组,每组6个重复,每个重复8只。以储存3年玉米作为能量原料,Ⅰ组(对照组)饲喂基础饲粮(不添加饲料抗氧化剂),Ⅱ、Ⅲ、Ⅳ组分别饲喂在基础饲粮中添加120 mg/kg TP、维生素E和BHT的试验饲粮。试验期42 d。结果表明:1)与对照组相比,TP能显著提高22~42日龄肉鸭平均日增重(P0.05),维生素E能显著提高1~21日龄和22~42日龄肉鸭平均日增重(P0.05),BHT对肉鸭生长性能无显著影响(P0.05)。2)与对照组相比,TP能显著提高21和42日龄血清总抗氧化能力(T-AOC)以及42日龄血清过氧化氢酶(CAT)活性(P0.05),维生素E能显著提高42日龄血清CAT活性(P0.05);BHT能显著提高21日龄血清T-AOC以及21和42日龄血清CAT活性(P0.05)。由此可见,陈玉米饲粮中添加TP和维生素E对肉鸭生长性能以及抗氧化功能均有不同程度的改善,而BHT只改善了肉鸭的抗氧化功能。陈玉米饲粮中添加TP效果最好。     

铬的生物学作用及其在畜禽生产中的应用

本文叙述了铬的研究历史,铬的分类、不同类型的铬在动物及人体内的吸收情况,铬的代谢分布情况;重点阐述了铬的生物学作用、铬对畜禽生产性能的影响及铬对动物免疫、应激功能的影响,最后对铬的未来研究作了展望。     

玉簪抗旱性隶属函数及主成分分析

为利用我国丰富的玉簪属(Hosta)种质资源,给园林绿化提供优良抗旱的玉簪属植物品种,应用隶属函数及主成分分析法对5个优良玉簪品种的抗旱性进行了评价.结果表明:7个存在一定相关关系的抗旱指标通过隶属函数结合主成分分析归纳成伤害程度因子、抗旱能力因子、水分状况因子3个主成分;5个玉簪属植物种质资源的抗旱性顺序由强到弱依次为:金冠玉簪>白花玉簪>花叶玉簪>紫萼玉簪>绿叶玉簪;综合聚类分析,金冠玉簪、白花玉簪抗旱性较强,可供将来在缺水地区生产实践中参考使用,以解决园林建设和水资源有限两者之间的矛盾.     

共轭亚油酸及其生物学功能研究进展

共轭亚油酸（CLA）是含有共轭双键的亚油酸家族的总称,在这个家族中至少有28个同分异构体,它们主要存在于反刍动物的脂肪中.其中含量最多,生物学功能最为广泛的c9t11 CLA,占整个CLA总量的80％～90％.其生物学功能包括抗肿瘤细胞生长、改善心血管系统功能、增强机体免疫力以及预防糖尿病等.其次为t1oc12 CLA,占CLA总量的3％～5％,其主要生物学功能为降低脂肪酸的合成,抑制脂肪细胞的分化与生长等.给反刍动物饲喂具有不同脂肪酸含量特征的油菜籽、长链不饱和脂肪酸等,或对体内硬酯酰辅酶A去饱和酶的活性进行调节,均可提高反刍动物组织中的CLA含量,从而生产出具有促进人体健康的功能性畜产品.未来的研究应该阐明共轭亚油酸中的共轭结构是如何发挥其生物学功能的,在其他营养物质中是否也存在具有生物学功能的结构形式.     

20个高羊茅品种镉耐性评价及富集特征

采用水培试验,用10μM Cd~(2+)对20个高羊茅(Festuca arundinacea)品种进行处理,采用隶属函数值法和聚类分析法对其镉耐性和富集特征进行综合评价。结果表明,与对照相比,Cd~(2+)处理下所有参试高羊茅品种在株高、根长、生物量和光合色素含量等指标上均显著降低(P0.05),品种间变化值的差异也达到了显著水平(P0.05)。20份材料的平均隶属函数值变幅在为0.185~0.758,其中‘Commander’的镉耐性最强。20个品种间Cd~(2+)吸收和累积量也有很大差异,地上部Cd~(2+)浓度范围为106.66~150.97mg·kg~(-1),Cd~(2+)累积量最高值为6.87μg·株-1,最低值仅2.75μg·株-1,其中品种‘Commander’和‘Red Start’在Cd~(2+)吸收和累积上表现较好。通过综合评价最终将20个高羊茅品种分为4类,分别是高耐高吸收型:‘Arid 3’,‘Extreme’,‘Commander’,‘Escalade’,‘Ecological King’,‘Ky-32’,‘Red Start’,‘Green Label’;高耐低吸收型:‘Gold Crown’,‘Justice’,‘Honky Tonk’,‘Aries’;低耐高吸收型:‘RubyⅡ’,‘Coronado TDH’;低耐低吸收型:‘K31’,‘Crossfire Ⅲ’,‘Essential’,‘Super Watchdog’,‘Gram villa’,‘Dynamic Ⅱ’。     

DNA疫苗的作用机制及新型免疫策略的研究进展

疫苗是预防和控制严重传染病的重要手段，将基因工程用于疫苗生产已经成为生物技术的热点内容之一。治疗性基因工程疫苗是近些年研究的重点，并迅速从治疗传染性疾病的研究扩展到非传染性疾病的研究，如治疗性乙肝疫苗、治疗性肿瘤疫苗等。本文针对这一热点阐述基因工程DNA疫苗的作用机制及新型免疫策略研究的进展。