Bird reproduction

Chickens fed with penta- and hexaCNs at 100 mg kg 1 in the diet produced chick edema disease [44]. Penta- and hexaCNs fed to turkeys at 20 mg kg-1 in feed for 40 days resulted in 50% mortality. At a concentration of 5 mg kg 1 feed, PCNs caused 6.5% mortality and 33% reduction in body weight [44], Histological examination revealed liver damage in exposed birds. Reproductive problems were also observed in chickens fed with a Halowax 1014 mixture at doses greater than 100 mg kg-1 bw. 

Chlorfenapyr is used on cotton, vegetables, and ornamentals to control whiteflies, thrips, caterpillars, mites, leafminers, aphids, and Colorado potato beetles. It has an oral LD50 in rats of 441 mg/kg. This compound is not registered for cotton insect control in the United States because of potential hazards to bird reproduction. 

Not all accepted that bird reproduction toxicity was a serious problem and that DDT should be banned. In October 1971 Nature had a comment from the Nobel Peace Price winner Norman E. Borlaug that symbolized the green revolution. 

Oil spills are deadly dangerous for Arctic fauna. A lot of animals die in oil-traps (collection of oil in low-lying areas). Birds die in lakes and seas due to contamination of feathers and violation of air-exchange processes. As oil contamination of egg shell kills germinating birds, reproduction of birds in most of the oil-fields in the Arctic became impossible. Oil film on the sea surface is even more dangerous for biota than oil diluted in seawater. 

Interaction of vitamin D and its metaboUtes with sex hormones has been demonstrated, particularly ia birds ia which the egg-laying functions combine calcium needs and reproductive activity. The metaboUtes of vitamin D behave as hormones. As such, they play an active role ia the endocrine system, along with other hormones, to maintain the various body functions. Several biological influences of metaboUtes of vitamin D have been studied, including effects related to cancer (193—197), skin diseases (198—201), immunomodulatory effects (202,203), and Alzheimer s disease (204—206) (Fig. 9). 

The detrimental effect of organochlorine pesticides on reproductive success in birds of prey is well established following the crash of some populations during the 1950s and 1960s. Links have been established with the DDT metabolite, DDE, the cyclodiene pesticides and Although many raptor species... 

Animal nutritionists have developed formulas to guide them in recommending the amount of food to feed animals in captive situations such as in zoos. First, the number of calorics needed to maintain the animal while at rest is determined—this is called the basal metabolic rate (BMR). In general, a reptile s BMR is only 15 percent that of a placental mammal, while a bird s is quite a bit higher than both a reptile s and a mammal s. For all animals, the number of calories they should receive on a maintenance diet is twice that used at the basal metabolic rate. A growing animal should receive three times the number of calories at the BMR, while an animal in the reproductive phase should receive four to six times the BMR. 

Water birds have not been shown to be directly affected by acidification. However, the prey of waterbirds may be of concern as these lower food-chain organisms may have elevated levels of toxic metals related to acidification of their habitat. Moreover, most water birds rely on some component of the aquatic food-chain for their high protein diet. Invertebrates that normally supply caJcium to egg-laying birds or their growing chicks are among the first to disappear as lakes acidify. As these food sources are reduced or eliminated due to acidification, bird habitat is reduced and reproductive rate of the birds is affected. The Common Loon is able to raise fewer chicks, or none at all, on acidic lakes where fish populations are reduced 37 and 5S). However, in some isolated cases, food supplies can be increased when competitive species are eliminated (e.g.. Common Goldeneye ducks can better exploit insects as food when competition from fish is eliminated). The collective influences of acidification are difficult to quantify on a specific area basis but for species that rely on a healthy aquatic ecosystem to breed, acidification remains a continuing threat in thousands of lakes across eastern North America 14). 

Toxic equivalency factors (TEFs) are estimated relative to 2,3,7,8-TCDD, which is assigned a value of 1. They are measures of the toxicity of individual compounds relative to that of 2,3,7,8-TCDD. A variety of toxic indices, measured in vivo or in vitro, have been used to estimate TEFs, including reproductive effects (e.g., embryo toxicity in birds), immunotoxicity, and effects on organ weights. The degree of induction of P450 lAl is another measure from which estimations of TEF values have been made. The usual approach is to compare a dose-response curve for a test compound with that of the reference compound, 2,3,7,8-TCDD, and thereby establish the concentrations (or doses) that are required to elicit a standard response. The ratio of concentration of 2,3,7,8-TCDD to concentration of test chemical when both compounds produce the same degree of response is the TEF. Once determined, a TEF can be used to convert a concentration of a dioxin-like chemical found in an environmental sample to a toxic equivalent (TEQ). 

PCB fraction accounted for 75%+ of TEQ by either assay reduced productivity of birds in this area TEQs mainly due to PCBs, especially 3,3, 4,4 -TCB Reduced reproductive success, but less effect than expected from high TEQs PCDDs, PCDFs, and PCBs made variable, but on the whole similar contributions to TEQ values probably not high enough to adversely affect fish populations TCDD mainly 2,3,7,8-TCDD Reduced hatching... 

Eroschenko, V.P. (1981). Estrogenic activity of the insecticide chlordecone in the reproductive-tract of birds and mammals. Journal of Toxicology and Environmental Health 8, 731-742. 

Fry, D.M. (1995). Reproductive effects in birds exposed to pesticides and industrial-chemicals. Environmental Health Perspectives 103, 165-171. 

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