Effects of landscape structure on nest predation in roadsides of a midwestern agroecosystem: a multiscale analysis

Nest predation is an important cause of mortality for many bird species, especially in grassland ecosystems where generalist predators have responded positively to human disturbance and landscape fragmentation. Our study evaluated the influence of the composition and configuration of the surrounding landscape on nest predation. Transects consisting of 10 artificial ground nests each were set up in 136 roadsides in six watersheds in south-central Iowa. Nest predation on individual roadside transects ranged from 0 to 100% and averaged 23%. The relationship of landscape structure within spatially-nested landscapes surrounding each roadside transect (within 200, 400, 800, 1200, and 1600 m of the transect line) to nest predation was evaluated by using multiple regression and canonical correlation analyses. The results of this multiscale landscape analysis demonstrated that predation on ground nests was affected by the surrounding landscape mosaic and that nest predators with different-sized home ranges and habitat affinities responded to landscapes in different ways. In general, wooded habitats were associated with greater nest predation, whereas herbaceous habitats (except alfalfa/pasture) either were associated with less nest predation or were not important. Different landscape variables were important at different spatial scales. Whereas some block-cover habitats such as woodland were important at all scales, others such as rowcrops and alfalfa/pasture were important at large scales. Some strip-cover habitats such as gravel roads and paved roads were important at small scales, but others such as wooded roadsides were important at all all scales. Most landscape metrics (e.g., mean patch size and edge density) were important at large scales. Our study demonstrated that the relationships between landscape structure and predator assemblages are complex, thus making efforts to enhance avian productivity in agricultural landscapes a difficult management goal.     

欧盟对动物促生长剂的措施及其对畜牧业的影响

欧盟专员 Ｆｒａｎｚ Ｆｉｓｃｈｌｅｒ于 １９９５年 １１月 ２９～３０日和１２月１日在布鲁塞尔组织了关于肉类生产中使用生长促进剂的科学研讨会。此后有关抗生素作为饲料添加剂的一场新的争论又开始了。同时对同化激素和生长激素类促生长剂的应用前景也展开了争论。禁用生长激素的理由，是否有科学的依据？对于中国畜牧业会有什么潜在的影响？本文将就欧盟禁用动物促生长剂产品的科学依据以及对中国畜牧业有什么影响作一探讨。１同化激素和生长激素是否有应用前景 让我们首先回顾一下同化激素（促合成代谢剂ａｎａｂｏｌｉｃ ｏｇｅｎ…     

Quinolone resistance in Escherichia coli.

Escherichia coli is an important pathogen of animals and humans that causes great financial cost in food production by causing disease in food animals. The quinolones are a class of synthetic antimicrobial agents with excellent activity against Escherichia coli and other Gram-negative bacteria used in human and veterinary medicine. Different quinolones are used to treat various conditions in animals in different parts of the world. All members of this class of drug have the same mode of action: inhibition of topoisomerase enzymes, DNA Gyrase and Topoisomerase IV. Escherichia coli can become resistant to quinolones by altering the target enzymes, reducing permeability of the cell to inhibit their entry, or by actively pumping the drug out of the cell. All these resistance mechanisms can play a role in high-level fluoroquinolone resistance, however target site mutations appear to be most important. As all quinolones act in the same way resistance to one member of the class will also confer decreased susceptibility to all members of the family. Quinolone resistant Escherichia coli in animals have increased in numbers after quinolone introduction in a number of different case studies. The resistance mechanisms in these isolates are the same as those in resistant strains found in humans. Care needs to be taken to ensure that quinolones are used sparingly and appropriately as highly resistant strains of Escherichia coli can be selected and may pass into the food chain. As these drugs are of major therapeutic importance in human medicine, this is a public health concern. More information as to the numbers of quinolone resistant Escherichia coli and the relationship between resistance and quinolone use is needed to allow us to make better informed decisions about when and when not to use quinolones in the treatment of animals.     

The effects of vaccination of Merino ewes with an attenuated Australian bluetongue virus serotype 23 at different stages of gestation

SUMMARY A cell culture attenuated Australian bluetongue virus serotype 23 (BLU23) prototype vaccine was assessed for its effects on pregnant Merino sheep. Seventy-six ewes were vaccinated at 5 different stages of gestation, and the failure to lamb at term was as follows: 35 to 43 days of gestation, 20/36 (56%); 57 to 64 days of gestation, 3/10 (30%); 81 to 88 days of gestation, 3/10 (30%); 109 to 116 days of gestation, 0/10 (0%); 130 to 137 days of gestation, 0/10 (0%). Of 30 ewes vaccinated with a cell culture supernatant fluid control between 35 and 43 days of gestation, 6.7% (2/30) failed to lamb at term. Two ewes vaccinated with BLU23 vaccine between 35 and 43 days of gestation had lambs with hydranencephaly. All other lambs born were clinically normal. Three ewes vaccinated with BLU23 aborted. Two of these were vaccinated between 35 and 43 days of gestation, the 3rd between 81 and 88 days of gestation. Five lambs were born with BLU group antibody. Four of these were from ewes vaccinated between 35 and 43 days of gestation, and 2 of these had hydranencephaly. The fifth was from a ewe vaccinated between 57 and 64 days of gestation. The vaccine did not produce disease in adult sheep, but was a potent cause of early foetal death and to a much lesser extent foetal malformation.     

Effect of Breeding Activity on the Microflora of the External Genitalia and in the Semen of Stallions,and the Relationship Between Micro‐organisms on the Skin and on the External Genitalia

A possible role of breeding activities in the composition of the microbial population in stallions' external genitalia (EG) and the relationship between micro‐organisms colonizing the skin of the abdomen and the ones colonizing the EG have not been studied. In experiment 1, EG microbiological samples were collected from 41 stallions used for both natural cover and semen collection (BST) and from 18 non‐breeding stallions (NBST). A higher (p < 0.05) frequency of isolation of potentially pathogenic species was found for BST. Age did not influence number of micro‐organism species isolated both in BST and NBST. In experiment 2, the microbial content of the EG and semen was compared in 23 BST. Most micro‐organisms isolated from the EG were present in semen, albeit with a numerically lower prevalence. In 7 stallions, six microbial species isolated from semen were absent from the EG cultures, suggesting contamination by the operator. In experiment 3, a numerically higher number of micro‐organism species was isolated from the EG of 31 stallions, than from their skin of the ventral abdomen in contact with the penis or from the skin of the thorax. With the sole exception of Escherichia coli, potentially pathogenic bacteria were only isolated from the EG but not from the skin. Results suggest that breeding activity increased the number of species colonizing the EG; most species isolated from the EG were also found in semen even if with a lower frequency, and additional semen contamination seemed to occur during its manipulation. Many micro‐organism species of the skin were also isolated from the penis, but independently of being or not in contact with the penis, skin did not seem to provide an adequate environment for the growth of potentially pathogenic bacteria that were isolated from EG, with the sole exception for E. coli.     

Prevalence of Bovine Dermatophilosis in a Tropical Highland Region of Ethiopia

A study was made of bovine dermatophilosis on 540 animals at a high altitude (2400–2500 m above sea level) in Ethiopia. Eighty-two (15.4%) of the animals were affected by the disease which was more prevalent in local animals than was previously assumed. There was a significant (p<0.05) difference in the prevalence among different age groups. However, the difference in the prevalence of the disease between males and females was not significant (p>0.05). Associated risk factors included the relatively high average annual rainfall and humidity, tick infestation (76%) and management, related to the mixed crop-livestock production system. The possible impact of the disease on Ethiopian agriculture is indicated.     

Fine structure of the canal neuromasts of the lateral line system in the adult zebrafish

The mechanosensory lateral line system of fish is responsible for several functions such as balance, hearing, and orientation in water flow and is formed by neuromast receptor organs distributed on head, trunk and tail. Superficial and canal neuromasts can be distinguished for localization and morphological differences. Several information is present regarding the superficial neuromasts of zebrafish and other teleosts especially during larval and juvenile stages, while not as numerous data are so far available about the ultrastructural characteristics of the canal neuromasts in adult zebrafish. Therefore, the aim of this study was to investigate by transmission electron microscopy the ultrastructural aspects of cells present in the canal neuromasts. Besides the typical cellular aspects of the neuromast, different cellular types of hair cells were observed that could be identified as developing hair cells during the physiological turnover. The knowledge of the observed cellular types of the canal neuromasts and their origin could give a contribution to studies carried out on adult zebrafish used as model in neurological and non‐neurological damages, such as deafness and vestibular disorders.     

Nature of early reproductive failure caused by bovine viral diarrhea virus

A 2-part study was undertaken to determine the effect of bovine viral diarrhea (BVD) virus on fertilization and early development of embryos. In experiment 1, 10 seronegative cows were superovulated and artificially inseminated twice during estrus. After the second insemination, 5 of the cows received intrauterine infusion of BVD virus suspension. The other 5 cows received suspending medium only and served as controls. All 10 cows were slaughtered on day 3, and ova and embryos were collected for morphologic evaluation. A total of 49 and 52 ova and embryos were collected from the control and virus-treated cows, respectively. Among the ova and embryos collected from control cows, 81.6% were fertilized, whereas only 52% were fertilized in the virus-treated group. The statistically significant difference (P less than 0.01) indicated that the virus interferes with fertilization. In experiment 2, the protocol was identical except for slaughter on day 13. Seventy-nine ova and embryos were collected from the 6 control cows, and the 6 virus-treated cows yielded 59 ova and embryos. Of the total ova and embryos recovered on day 13, 88.6% and 50.8% were hatched and developing normally in the control and virus-treated groups, respectively. The difference was highly significant (P less than 0.001). Unfertilized ova and degenerating embryos could not be differentiated on the basis of morphologic appearance. The nearly identical percentages of unfertilized ova in experiment 1 and unhatched ova and embryos in experiment 2 strongly suggested that fertilization failure is the principal manifestation of the observed adverse effect of BVD virus infection.     

Coxiella burnetii: Serological reactions and bacterial shedding in primiparous dairy cows in an endemically infected herd—impact on milk yield and fertility

Coxiella burnetii (C. burnetii) is the causative agent of Q fever both in humans and animals. The objectives of this study were to investigate seropositivity and bacterial shedding in heifers and primiparous cows in an endemically infected herd and to assess the effects on post‐partum diseases, fertility and milk production. At the age of 9 months, 96 Holstein heifers were included. Sampling was performed reproduction‐orientated: at the beginning of the study, at detection of first pregnancy, 3 weeks before expected calving date (blood serum), at parturition and after 21, 42, 100 and 150 days in milk (DIM) (blood serum, vaginal swabs and milk). Serum samples were investigated by a commercial ELISA for the presence of specific antibodies and vaginal swabs and milk samples by PCR to detect C. burnetii DNA. Individual animal data (calving ease, stillbirth, retained foetal membranes, puerperal metritis, endometritis after 42 DIM, presence of corpus luteum after 42 DIM, interval calving‐first service, interval calving‐conception, number of inseminations until 150 DIM, proportion of pregnant cows until 100 and 150 DIM, proportion of pregnant cows after first service and data of the dairy herd improvement test) were documented. All heifers were seronegative at the age of 9 months and 3 weeks before the expected calving date. Subsequently, the proportion of seropositive animals and the antibody score increased significantly towards 42 and 100 DIM, respectively. Vaginal C. burnetii shedding was highest at parturition (30.9%), while the most positive milk samples were detected after 100 DIM (15.3%). Coxiella burnetii seropositivity and shedding had no impact on parameters of reproduction. However, milk fat yield was declined in puerperal vaginal shedders and cows which seroconverted during their first 42 DIM, respectively.