Endocrine and sperminogenic testicular function. 8. Relationships between testicular and plasma testosterone concentrations as well as between the number of Leydig cells in testicular tissue and their cell nucleus volume in boars of different ages]

Testicular tissue and blood samples (V. spermatica interna) were taken from 32 boars during castration. The animals were different age groups. Against this background, studies were conducted into the correlations between testicular and plasma testosterone, on the one hand, and the amount of interstitial cells of Leydig in testicular tissue as well as the latters' cell nuclei volumes, on the other. The results seemed to support the conclusion that any age-dependent increase of testicular and plasma testosterone concentrations was caused unambigously by an absolute increase in volume of androgenic testicular tissue, in concomitance with testicular growth, in other words, by rise in the total number of interstitial cells of Leydig.     

Excessive oral administration of iron to sheep. 1. Digestibility of rations, results of fattening and carcass yields]

4 digestibility trials (4 male sheep per group) and 2 growth trials were carried out with 24 (V 1) and 32 (V 2) fattening lambs to investigate the effect of abundant oral Fe doses on the digestibility of crude nutrients in a ration of barley + dried green feed and on the results of fattening and carcass yields. Fe supplementation (less than 1400 mg per sheep/day) did not significantly change the digestibility coefficients of crude nutrients. Increasing Fe levels in the concentrates decreased the rates of liveweight increase and food consumption in both growth trials. Well-established statistical evidence was provided for the decline in absolute carcass yields resulting from the lower weight of the lambs at the end of the fattening period after Fe supplementation.     

Hemagglutinating encephalomyelitis virus (HEV) infections in swine. Serologic indication for infectional occurrence in Denmark]

In 1956 a disease of nursing pigs previously unreported in Denmark, was observed in several swine herds. The disease syndrome appeared identical with that later described by Roe and Alexander in 1958 and by S. F. Cartwright and M. Lucas in 1968. Since 1956 there have been no reports of such outbreaks in Danish herds. To investigate whether the virus is still present, a survey was carried out to detect neutralizing antibodies in sera from a number of boars using a micro technique. In 144 sera from Jutland 12% had titers ranging from 10 to 32 ND-50, 22% from 32 to 90, 37% from 90 to 256, 14% from 256 to 724 and 3% above 724 ND-50 with a total of 86% positive. Of 174 sera from the rest of the country 16% had titers ranging from 10 to 32 ND-50, 18% from 32 to 90, 28% from 90 to 256, 13% from 256 to 724 and 3% exceeding 724 ND-50 with a total of 79% positive.     

Breeding objectives for beef cattle used in different production systems: 2. Model application to production systems with the Charolais breed

A general bio-economic model for beef cattle production was used to define breeding objectives for Charolais cattle to be utilized in a variety of linked production systems. Economic weights were calculated for 16 traits (some with both direct and maternal components) in three production systems (pure-breeding and terminal crossing with beef or dairy cows) and two marketing strategies (sale or fattening of weaned surplus calves). Economic weights for the total breeding objective were calculated as weighted averages, where weights were numbers of cows expected to be mated with Charolais bulls in each production system and marketing strategy. Results suggest that the direct component of calving performance and cow longevity were of primary economic importance in all systems. Conception rate of cows and weaning weight reached about 50% of the standardized economic weight of calving performance in purebred systems with sale of weaned calves, whereas in purebred systems with fattening the economic importance of the direct component of cow conception rate, losses at calving, mature weight of cows, weaning weight, and fattening traits were of equal importance (each approximately about 20% that of calving performance). In terminal crossing systems, weaning weight was important when calves were sold at weaning, and fattening traits were important for systems selling fattened animals. The bio-economic model performed well under the conditions of this demonstration and could easily be customized for other applications.     

Campylobacter spp., Salmonella spp., Verocytotoxic Escherichia coli,and Antibiotic Resistance in Indicator Organisms in Wild Cervids

Faecal samples were collected, as part of the National Health Surveillance Program for Cervids (HOP) in Norway, from wild red deer, roe deer, moose and reindeer during ordinary hunting seasons from 2001 to 2003. Samples from a total of 618 animals were examined for verocytotoxic E. coli (VTEC); 611 animals for Salmonella and 324 animals for Campylobacter. A total of 50 samples were cultivated from each cervid species in order to isolate the indicator bacterial species E. coli and Enterococcus faecalis/E. faecium for antibiotic resistance pattern studies. Salmonella and the potentially human pathogenic verocytotoxic E. coli were not isolated, while Campylobacter jejuni jejuni was found in one roe deer sample only. Antibiotic resistance was found in 13 (7.3%) of the 179 E. coli isolates tested, eight of these being resistant against one type of antibiotic only. The proportion of resistant E. coli isolates was higher in wild reindeer (24%) than in the other cervids (2.2%). E. faecalis or E. faecium were isolated from 19 of the samples, none of these being reindeer. All the strains isolated were resistant against one (84%) or more (16%) antibiotics. A total of 14 E. faecalis-strains were resistant to virginiamycin only. The results indicate that the cervid species studied do not constitute an important infectious reservoir for either the human pathogens or the antibiotic resistant microorganisms included in the study.     

Pregnancy Rates in Repeat-breeder Heifers Following Multiple Artificial Inseminations during Spontaneous Oestrus

Hormonal asynchronies during oestrus, related to the presence of suprabasal plasma-progesterone (P4) concentrations and a delayed ovulation, interfere with the fertility of repeat-breeder heifers (RBH). Since tubal dysfunction can occur in connection with hormonal asynchronies and constrained availability of fertile spermatozoa at the time of ovulation, the present study tested the hypothesis that frequent sperm deposition from onset of oestrus to ovulation may improve pregnancy rates in RBH. Five RBH and five virgin heifers (VH; controls) were repeatedly artificially inseminated (AI) at 6 h intervals from onset of oestrus to spontaneous ovulation. Hormone analyses revealed suprabasal P₄ concentrations and a delay in the occurrence of the luteinising hormone (LH) surge, but a normal cortisol profile in RBH. Compared with controls, RBH presented longer interval from onset of oestrus to ovulation, and therefore, received more AIs. Pregnancy rates in RBH reached control levels (60%; NS), indicating that the hypothesis might be correct. Pregnancy rates in VH were below the expected range, presumably attributed to a deleterious influence of the frequent handling. The study suggests that pregnancy rates can be improved in RBH by frequent AI in relation to spontaneous ovulation. However, this practice of repeated manipulations, while seeming not to show adverse effects, lacks practicality for routine use.     

黄瓜低温弱光耐受性机理及其应用研究的主要进展

选择低温弱光抗性水平不同的欧洲温室型、欧亚杂交型、华北温室型、华北露地型黄瓜(Cucumis sati- vus L.)的16个品种为试验材料,以光合代谢为切入点,开展苗期光合速率、光补偿点、1,5-二磷酸核酮糖羧化酶 (rubisco)活性和叶绿素a荧光动力学曲线的系统研究,结果表明:单一偏低温和偏低温弱光协效应未明显伤害光合系统,而临界低温可能伤及PSⅡ;偏低温和弱光组合时,弱光对黄瓜幼苗的影响起主导作用,弱光与临界低温组合时,临界低温起主导作用;偏低温弱光(单一弱光)下的叶面积增长量和临界低温下的冷害指数可分别作为评价黄瓜对偏低温弱光(单一弱光)耐受性和临界低温耐受性的比较稳定可靠的指标,据此设计了相关的评价指标体系。用117个重组自交系为材料,以弱光下叶面积增长量为指标进行弱光耐受性评价并以RAPD、AFLP、SSR分子图谱为基础,通过区间作图,检测到5个与黄瓜弱光耐受性有关的QTLs。采用mRNA差异显示银染技术克隆得到黄瓜冷敏型品种津研4号低温锻炼中特异表达基因的cDNA克隆(ccr18),其大小为639 bp。在基因组中以单拷贝或低拷贝形式存在。序列同源性比较表明它与拟南芥[Arabidopsis thaliana(L．)Heynh．]染色体ⅣBAC库中的 F14P3基因组序列具有88％的同源性。     

用外翻肠囊法研究高钙条件下有机锰在肉仔鸡小肠中的吸收特点

本试验用外翻肠囊法研究高钙对肉仔鸡不同肠段(十二指肠、空肠和回肠)吸收不同形态锰的影响,以比较有机锰和无机锰在高钙条件下吸收特点的差异。采用单因子完全随机设计,培养液中添加的4种锰源分别为:硫酸锰、弱络合强度的蛋氨酸锰(Mn-MetE)、中等络合强度的氨基酸锰(Mn-AAA)和强络合强度的氨基酸锰(Mn-AAB)。为了扣除内源的影响,设置1个零添加锰水平处理。将40只31日龄AA肉公鸡随机分到以上5个组,每组8个重复,每个重复1只鸡,每只鸡的十二指肠、空肠和回肠分别作为相应肠段外翻肠囊的一个重复。结果表明:1)体外培养回肠肠囊对锰的吸收率显著高于十二指肠(P<0.01);2)回肠肠囊对强络合强度的Mn-AAB中锰的吸收率显著高于硫酸锰或中等络合强度的Mn-AAA(P<0.05)。本试验结果表明:在高钙条件下,络合形态的有机锰在体外培养的肉仔鸡肠囊中的吸收率显著高于无机形态的锰;强络合强度有机锰源中的锰能更强地抵抗小肠内的解离,比弱或中等络合强度的有机锰源更有利于锰的吸收。