Investigating the heat tolerance and production performance in local chicken breed having normal and dwarf size

Heat stress significantly impairs the growth performance of broilers, which causes serious losses to the poultry industry every year. Thus, understanding the performance of indigenous chicken breeds under such environment is crucial to address heat stress problem. The purpose of this study was to investigate the effects of heat stress (HS) on production performance, tissue histology, heat shock response (HSP70, HSP90), and muscle growth-related genes (GHR, IGF-1, and IGF-1R) of Normal yellow chicken (NYC) and Dwarf yellow chicken (DYC). Seventy-two female birds from each strain were raised under normal environmental conditions up to 84 days, with birds from each strain being divided into two groups (HS and control). In the HS group, birds were subjected to high temperature at 35 ± 1 °C for 8 h daily and lasted for a week, while in the control group, birds were raised at 28 ± 1 °C. At 91 days old, bird's liver, hypothalamus, and breast muscle tissues were collected to evaluate the gene expression, histological changes, and the production performance. The Feed intake, weight gain ratio, total protein intake and protein efficiency ratio showed a significant reduction in the treatments (P < 0.01) and treatment × strain interaction (P < 0.05) with breast muscle rate significantly reducing among the treatments (P < 0.01) after 7 days of HS. Correspondingly, total abdominal fat showed significant change among treatment and strain (P < 0.01, P < 0.05), respectively. Besides, HS markedly upregulated the mRNA expression of HSP70 and HSP90 in the pectoralis major of both chicken strains, but no significant increase (P < 0.05) was found in mRNA expression of HSP90 in liver and hypothalamus tissues of both chicken strains. Moreover, HS significantly upregulated (P < 0.05) the expression of lipogenic genes (FASN, ACC) in liver tissues of NYC, while mRNA expression of these genes showed no variation in DYC. Similarly, HS downregulated the mRNA expression of muscle growth-related genes (GHR, IGF-1, and IGF-1R). Consequently, the histopathological analysis showed that histological changes were accompanied by inflammatory cell infiltration in liver tissues of both chicken strains; however, histopathological changes were more severe in NYC than dwarf chicken strain. Conclusively, this study depicted that the production performance and growth rate varied significantly between treatment and control group of NYC. However, heat treatment in DYC has not shown significant damaging consequences as compared to the control group that signifies the vital role of the dwarf trait in thermal tolerance.     

Histopathology findings in common marmosets (<Emphasis Type="Italic">Callithrix jacchus</Emphasis> Linnaeus, 1758) with chronic weight loss associated with bile tract obstruction by infestation with <Emphasis Type="Italic">Platynosomum</Emphasis> (Loos, 1907)

Chronic weight loss in marmosets is often associated with wasting marmoset syndrome (WMS), an important disease that occurs in callitrichid colonies around the world. Even though its etiology is very difficult to determine, particular variables, such as weight loss, diarrhea and alopecia, associated or not with infestation in the pancreatic ducts with Trichospirura leptossoma (Nematoda: Thelazioidea), seem to be linked with the syndrome. This study investigated the histopathology of the lungs, duodenum, liver, gallbladder, extrahepatic bile ducts and pancreatic ducts of six common marmosets (Callithrix jacchus) suffering from severe non-diarrheic weight loss. Three individuals died naturally and the other three were euthanized. Microscopic findings showed the presence of adult flukes (Platynosomum) in the liver. These flukes, which provoke common infection in cats, were also observed inside the gallbladder as well as in the intra and extrahepatic bile ducts in common marmosets. Portal fibrosis was observed in two animals, which developed chronic fibrosing hepatopathy (biliary pattern, grade 3). The disease progresses without diarrhea and without pancreatic lesions or infestation. With the progression, the animals presented with ascending cholangitis, cholestasis and portal fibrosis, sometimes culminating in secondary biliary cirrhosis. Therefore, this infirmity, associated with chronic weight loss in common marmosets, could be another etiological factor linked with WMS.     

Path-finding in real and simulated rats: assessing the influence of path characteristics on navigation learning

A large body of experimental evidence suggests that the hippocampal place field system is involved in reward based navigation learning in rodents. Reinforcement learning (RL) mechanisms have been used to model this, associating the state space in an RL-algorithm to the place-field map in a rat. The convergence properties of RL-algorithms are affected by the exploration patterns of the learner. Therefore, we first analyzed the path characteristics of freely exploring rats in a test arena. We found that straight path segments with mean length 23 cm up to a maximal length of 80 cm take up a significant proportion of the total paths. Thus, rat paths are biased as compared to random exploration. Next we designed a RL system that reproduces these specific path characteristics. Our model arena is covered by overlapping, probabilistically firing place fields (PF) of realistic size and coverage. Because convergence of RL-algorithms is also influenced by the state space characteristics, different PF-sizes and densities, leading to a different degree of overlap, were also investigated. The model rat learns finding a reward opposite to its starting point. We observed that the combination of biased straight exploration, overlapping coverage and probabilistic firing will strongly impair the convergence of learning. When the degree of randomness in the exploration is increased, convergence improves, but the distribution of straight path segments becomes unrealistic and paths become 'wiggly'. To mend this situation without affecting the path characteristic two additional mechanisms are implemented: a gradual drop of the learned weights (weight decay) and path length limitation, which prevents learning if the reward is not found after some expected time. Both mechanisms limit the memory of the system and thereby counteract effects of getting trapped on a wrong path. When using these strategies individually divergent cases get substantially reduced and for some parameter settings no divergence was found anymore at all. Using weight decay and path length limitation at the same time, convergence is not much improved but instead time to convergence increases as the memory limiting effect is getting too strong. The degree of improvement relies also on the size and degree of overlap (coverage density) in the place field system. The used combination of these two parameters leads to a trade-off between convergence and speed to convergence. Thus, this study suggests that the role of the PF-system in navigation learning cannot be considered independently from the animals' exploration pattern.     

冬小麦根系各种参数垂直分布实验研究

本文根据田间实测资料研究了冬小麦根系各种参数(长度、重量、活性表面和根径)的垂直分布。结果表明,在所观测地区的土壤条件下,冬小麦根系的长度、重量、表面积和体积随深度呈指数分布,而累积根系的长度、重量和表面积随深度呈双曲线型分布。根据作者的观测资料和国内外其它观测资料分析研究表明,对于不同土壤,根区各层土壤中累计根重及根长的百分比随相对深度的变化都符合下列双曲线函数形式:这一研究结果可为根系生态研究和作物对水分吸收的模拟工作提供参考。     

The effects of short-term acute cadmium exposure on blue tilapia,Oreochromis aureus

Synopsis Disease-free blue tilapia,Oreochromis aureus, exposed to cadmium (0.5 ppm and 10 ppm) showed very significant and dramatic decrease in food consumptions. Food consumptions returned to near normal 21 days after fish were returned to cadmium-free water. Along with anorexia there were decreases in body weights during the period when fish were exposed to cadmium. Fish in cadmium-free water that were pair-fed to cadmium-exposed fish (0.5 ppm) did not gain weight but there were no decreases in body weights. Cadmium was still in tissues 34 days after the fish were placed in cadmium-free water and the accumulation was highest in the kidney; this was followed by liver, brain, gill filaments and muscles. The accumulations of the heavy metal (in kidneys and gills) were significantly higher in fish exposed to high than low cadmium levels. There were no differences in complement levels (haemolytic acitivity) in cadmium-exposed and cadmium-free fish. However, cadmium-exposed fish did not produce detectable haemagglutinating antibodies against sheep red blood cells while cadmium-free fish responded well to the antigen. The anorexia in cadmium-exposed fish contributed to the depression in antibody production.     

Cost of reproduction: parental survival and production of recruits in the Willow Tit Parus montanus

Summary Brood sizes of the Willow Tit were altered experimentally by subtracting or adding two nestlings in 1986 and 1987 in the vicinity of Oulu, northern Finland. The manipulated broods were within the normal range observed in natural conditions. Unaltered broods were used as controls. Data from natural broods from 1978–1985 were available for comparison. When the nestlings were 13 days old they were ringed and weighed and their tarsus, wing, and tail lengths were measured. On the same day the parents were caught, weighed, and measured. In 1986 there were no differences in nestling mortality between the reduced, control, or enlarged broods; i.e. parents were able to fledge the two extra young. In 1987 starvation was most pronounced in the enlarged broods. This resulted in the number of fledglings being practically the same in each manipulation category. Especially the body weight, but also the other indices of body size, decreased as a function of the brood size category, suggesting that there may be quality differences between the young reared in different experimental groups. In 1986 there was a non-significant trend towards lower body weight of the parents attending reduced, control, or enlarged broods, in that order. In 1987 the differences were much smaller. These results were not due to size differences between the groups, so possibly the increased reproductive effort of raising extra young was responsible for the trend observed in 1986. There were no significant differences in parental survival associated with the manipulation category, although the trend in the females was consistent with the hypothesis of reproductive cost. It is possible that environmental conditions in 1986 were so favourable that the tits were not unduly stressed even when attending two extra young. Correlative data from 1978–1985 did not support the cost hypothesis either. A non-significant trend towards reduced post-fledging survival and recruitment of the young was observed with increased brood size. The average fitness value of parents, incorporating parental survival and number of recruits, showed that the success of the adults raising enlarged broods may be lower than that of others. It seems that the reproductive cost, if it exists, decreases individual fitness value by reducing the chances of recruiting descendants into the next generation. The reproductive stress may be insufficient to reduce the subsequent survival of parents. More data are however needed to confirm these results.     

The population dynamics of the large pine aphid,Cinara pinea (Mordv.)

The large pine aphid, Cinara pinea lives exclusively on Pinus species, where it feeds on the foliated shoots of the current and previous year. The paper describes the development of a computer model designed to simulate the aphid's population dynamics on saplings in the controlled environment of the laboratory, i.e. in the absence of natural enemies. The model was able to account for about 80% of the variation in aphid numbers within and between trees over a three month period. Sensitivity analysis revealed that the number of pine aphids is limited primarily by nymphal emigration, the operation of which is sensitive both to density and to plant quality as reflected in aphid growth rates. Of secondary importance are changes in reproduction acting through increased reproductive delay, again a result of altered growth rates and adult size. Development, too, has an important secondary influence. Contrary to expectation and conventional belief, however, alate production proved to be of negligible importance, either in limiting or regulating population numbers. Alatae are produced in too few numbers and for too short a period to significantly alter the pattern of population change.     

Serum and urinary markers of skeletal muscle tissue damage after weight lifting exercise

The purpose of this study was to determine whether high intensity weight lifting exercise produces elevations of urinary 3-methylhistidine (3-MH), serum creatine kinase activity (CK), and serum myoglobin concentration (MY), and whether trained weight lifters differed in such responses when compared to a group of untrained subjects. Ten experienced male weight lifters (EWL) and seven untrained male subjects (IWL) performed three sets of six weight lifting exercises at 70%-80% of 1 RM. All subjects consumed a meat-free diet. The 3-MH:creatinine (3-MH:CR) values decreased 24 h and 48 h following exercise (P less than 0.05). The 12-h and 24-h postexercise CK response and the 12-h postexercise MY response increased for both EWL and IWL (P less than 0.05). However, EWL had a lower 24-h postexercise CK response and lower 12-h and 24-h postexercise MY responses compared to IWL (P less than 0.05). Within 48 h following weight lifting exercise, skeletal muscle protein degradation (as assessed by 3-MH:CR values) decreased regardless of prior training experience whereas skeletal muscle tissue damage (as assessed by CK and MY responses) increased. However, prior weight lifting training appeared to diminish the extent of muscle tissue damage.     

A meta-analysis of the effects of exercise and/or dietary restriction on resting metabolic rate

A meta-analysis was used to examine the independent and interactive effects of dietary restriction, endurance exercise training and gender on resting metabolic rate (RMR). Sixty different group means (covering 650 subjects) were identified from the scientific literature and subjected to meta-analysis techniques. Collectively (i.e., all groups combined), body weight loss was greater (P < 0.05) for men ( 18 kg) than for women ( 12 kg). There were no statistically significant exercise training or gender effects on RMR during weight loss. Collectively (i.e., all groups combined), dietary restriction resulted in a – 0.59 kJ min^–1 ( – 12%) decrease in RMR (P < 0.05). When normalized to body weight, RMR was reduced by less than 2% (P < 0.05). These data suggest that exercise training does not differentially affect RMR during diet-induced weight loss. In addition, decreases in resting metabolism appear to be proportional to the loss of the metabolically active tissue.