Studies on Bovine Leukosis

Summary

An enzyme linked immunosorbent assay (ELISA) and the agar gel immunodiffusion test with bovine leukosis virus glycoprotein as antigen (AGIDT‐BLV gp) were further used to test 633 bovine sera for antibodies to BL V. Both tests detected the same number of sera positive (149) or negative (464) for antibodies. Nine sera were negative in the ELISA but found to be weakly positive (2 sera) or bending the control line (7) in the AGIDT‐BLV gp. On the other hand 11 sera were scored negative in the AGIDT‐BLV gp but were weakly positive (9 sera), positive (1), and strongly positive (I) in the ELISA. Both tests are used routinely in this Institute as they complement each other, specially if sera with low antibody titers are under investigation. It is concluded that ELISA can fully replace radioimmunoassays in the serodiagnosis of enzootic bovine leukosis.     

The Potch System: An approach to the management of semi‐arid grasslands in southern Africa

A host of grassland management systems have been published and recommended. Whereas earlier approaches to grassland management emphasized the systematic resting aspect, the systems published since 1966 have tended to stress the degree of utilization of the grassland sward. In an attempt to accommodate the periodic dry periods that are so typical of the semi‐arid grasslands of western Transvaal, the Potch system of management was evolved. It aims at the development of a fodder reserve, firstly by delaying the commencement of summer grazing, and secondly, by allowing prolonged periods of absence in the grazing rotation. High utilization grazing within the concept of controlled selective grazing is prescribed. This approach was tested and demonstrated over a period of five years in an experiment comprising 240 beef breeding cows. It appeared that generally, summer grazing only commenced after the third week of November, and that the mean period of occupation amounted to 20 days, with a period of absence of 87 days. A conception rate of 85% of all the cows and heifers mated, was achieved. A stocking rate of 0.53 LSU ha^?1 could be maintained in an area where the general grazing capacity is 0.33 LSU ha^?1.     

Evaluation of the Cranial Cruciate Ligament Repair System? in Surgery for Laryngeal Hemiplegia in Heavy Draft Horses

The purpose of this study was to evaluate the effect of the canine cranial cruciate ligament repair system on laryngeal hemiplegia in heavy draft horses. Twenty-four heavy draft horses diagnosed with grade 4 laryngeal hemiplegia were allocated to either the prosthetic laryngoplasty (PL) group (n=14) or a canine cranial cruciate ligament repair system (CCCLRS) group (n=10). Right to left angle quotients (RLQs) of abductions of the arytenoid cartilages were endoscopically evaluated before and after surgery. Post-operative RLQs in the CCCLRS group were significantly lower than those of the PL group (P<0.01). The canine cranial cruciate ligament repair system was revealed to be a good surgical procedure for laryngeal hemiplegia in heavy draft horses.     

Genetic analyses of piglet survival and individual birth weight on first generation data of a selection experiment for piglet survival under outdoor conditions

Genetic parameters of piglet survival traits and birth weight were estimated on the first generation data of a selection experiment aimed at improving piglet survival using a multiple trait linear and threshold model. Data on 5293 piglets for survival at birth, at day one after birth and during the entire nursing period, as well as individual birth weight and litter size, were recorded in an outdoor production system. Genetic effects of piglet survival traits and birth weight were estimated based on threshold and Gaussian models, respectively, using a Bayesian approach. The statistical model included as fixed effects selection group, parity, gender, fostering, gestation length and month of farrowing and, alternatively, an adjustment for litter size. Direct genetic effects (i.e. the piglet's genetic potential) for piglet survival and birth weight were estimated separately, whereas maternal genetic and environmental effects could only be estimated for the given data structure in a combined litter effect. Posterior means of heritabilities for direct genetic effects of survival at birth, at first day after birth and the entire nursing period, as well as birth weight, were 0.08, 0.07, 0.08 and 0.20, respectively. Genetic correlations among survival traits were in the range of 0.29 to 0.40 and indicate that these traits were mainly attributable to different genetic effects. Genetic correlations between direct effects of survival traits and birth weight ranged between 0.18 and 0.23 and were reduced when weights of stillborn piglets were omitted in the analysis or the traits were adjusted for litter size. The magnitudes of direct genetic effects of survival traits are substantially higher than estimates in the literature, which may indicate that these traits have a higher genetic influence under outdoor conditions. The use of birth weight in the multiple trait estimation provided important information for the estimation of survival traits due to its favourable genetic correlations with survival, its high heritability and its high information content as a continuously measured trait.     

Evaluation of a new strategy to modulate skeletal development in Thoroughbred performance horses by imposing track-based exercise during growth

REASON FOR PERFORMING STUDY: No data exist on the intensity of exercise required or on possible harmful effects of increasing exercise in foals over the natural level when free at pasture. OBJECTIVES: To investigate whether an increase in workload over free pasture exercise in the period from directly after birth to the start of training is tolerated by Thoroughbred (TB) foals without increasing injury rate or producing other undesired side effects. METHODS: Thirty-three TB foals were allocated to one of 2 exercise groups directly after birth. One group (PASTEX) was raised on pasture and the other (CONDEX) kept under identical circumstances, but was additionally subjected to an exercise protocol of gradually increasing intensity. Foals were monitored periodically and scored for the presence of clinical signs related to the musculoskeletal system (joint effusion, pain at flexion, occurrence of physeal swelling), and radiographs taken at the end of the conditioning phase. Also, behavioural studies were performed to detect any changes in behaviour related to the exercise programme. Cortisol levels were measured in both groups, to assess the level of stress. RESULTS: Workload in the CONDEX group was significantly higher than in the PASTEX group (approximately 30%). Conditioning increased the likelihood for joint effusion in the antebrachiocarpal joint, but reduced tarsocrural effusion and physeal swelling at the lateral distal radius, the third metacarpal bone (medial aspect) and lateral and medial aspects of the third metatarsal bone. CONCLUSIONS: The 30% increase in workload did not affect the animals' welfare, effects of conditioning exercise on clinical musculoskeletal health were few and there were no adverse effects. POTENTIAL RELEVANCE: This study supports the feasibility of imposing early conditioning exercise in horses and is a benchmark for its effects on the development of equine musculoskeletal tissues.     

Distribution of the neurokinin-1 receptor in equine intestinal smooth muscle

REASON FOR PERFORMING STUDY: Tachykinins have profound effects on equine intestinal motility, but the distribution of the neurokinin receptors (NKRs) through which they act is unknown. This study reports the distribution of one of these receptors, the neurokinin-1 receptor (NK1R), in smooth muscle throughout the equine intestinal tract. OBJECTIVES: To quantify the distribution of the NK1R, based upon mRNA expression, in smooth muscle of different regions of the equine intestinal tract. METHODS: Nine regions of the intestinal tract were sampled in 5 mature horses. Total RNA was isolated from smooth muscle and reverse transcribed; NK1R mRNA was then quantified using real-time PCR. RESULTS: NK1R mRNA was found at all levels of the sampled intestinal tract. The smooth muscle of the proximal small intestine and the ventral colon exhibited the highest level of NK1R mRNA expression in the equine intestinal tract. CONCLUSIONS: Tachykinins probably affect intestinal contractility and propulsion in the proximal small intestine and in the ventral colon.     

mRNA差异显示技术及其在动物遗传育种中的应用

ｍＲＮＡ差异显示技术是近年来国外发展起来的攻克隆新基因的一种新方法,同时已广泛用于人类基因调控和克隆研究。本文论述了这一新技术的原理、发展现状和在动物遗传育种中的应用领域。     

开食时间对雏鸡早期生长和内脏器官发育的影响

本试验旨在研究不同开食时间对雏鸡早期的生长性能及内脏器官发育的影响.试验选取1080只0日龄、体重相近的新扬州鸡雏鸡,根据开食时间不同,随机分成6个组,每个组3个重复,每个重复60只(30只公鸡,30只母鸡).出壳后一周内,每天从每个重复中随机挑选8只雏鸡(4公4母),分别称其活重后致死,取卵黄囊、肝脏、心脏、胰腺、法氏囊和小肠分别称重,测量小肠长度.结果表明,出壳后禁食36h对7日龄鸡体重没有显著负面影响,出壳后最长禁食时间不应超过60h.     

2018年全球口蹄疫流行状况分析

据世界动物卫生组织(OIE)和世界口蹄疫参考实验室(WRLFMD)样品检测报告,2018年全球共有50多个国家或地区报告发生口蹄疫疫情或检测到口蹄疫病毒。在亚洲、非洲,口蹄疫继续呈地方性或暴发流行,在欧洲(如俄罗斯和土耳其)及南美洲(哥伦比亚)的部分国家呈散发性流行。本文介绍了2018年全球口蹄疫发生情况,分析总结了全球口蹄疫流行特点,简述了全球防控进展,同时结合我国口蹄疫流行情况,对我国口蹄疫防控提出了相关建议。     

microRNA-124-3p调控H1N1亚型猪流感病毒致小鼠肺损伤的研究

为研究microRNA-124-3p（miR-124-3p）对H1N1亚型猪流感病毒（swine influenza virus,SIV）感染小鼠所致肺损伤的调控作用,本试验构建miR-124-3p腺病毒表达载体,通过小鼠尾部静脉注射法构建miR-124-3p差异表达小鼠模型,试验分3组：过表达组、抑制组和对照组。48 h后,各组小鼠鼻腔接种H1N1亚型SIV,每只10⁵ EID₅₀（50 μL）。连续观察14 d,计算小鼠平均体重变化率、观察病理切片并测定相关炎症因子IL-1β、TNF-α和IL-6 mRNA相对表达量。结果显示,已成功将pre-miR序列及其sponge序列插入腺病毒的穿梭质粒,并将其共转染293A细胞。实时荧光定量PCR检测证实,与对照组相比,过表达组和抑制组小鼠黑色素瘤细胞miR-124-3p表达水平分别极显著升高（P<0.01）和显著降低（P<0.05）,表明成功构建腺病毒表达载体。过表达组、抑制组和对照组小鼠体重变化率分别为－5.5%、－12.4%和－8.6%。抑制组和对照组均可见肺泡壁增厚,其间有多量淋巴细胞浸润,部分肺泡内出现纤维蛋白渗出,且抑制组病理变化更为严重,肺泡中还有大量的红细胞浸润;而过表达组仅有少量的淋巴细胞浸润,肺脏组织较正常。与对照组相比,过表达组检测的炎症因子IL-1β、TNF-α和IL-6 mRNA表达水平均显著降低（P<0.05）;抑制组炎症相关炎症因子mRNA表达水平均显著升高（P<0.05）。本试验结果表明,miR-124-3p对H1N1亚型SIV感染小鼠所致的肺脏炎症因子的表达具有抑制作用,同时能减轻肺脏病理损伤。