Differential effects of short photoperiod on 2-[125I]iodomelatonin binding in the testis and brain of quail

The affinities and densities of 2-[125I]iodomelatonin binding sites in the brains and gonads of male Japanese quail following short photoperiod treatment were studied. At 6 weeks old, control quail were placed under a 14 hour light/10 hour dark photo-stimulatory cycle and experimental quail were housed under a 7 hour light/17 hour dark photo-inhibitory lighting regime. Eighteen weeks after photic manipulation, the birds were killed at mid-light. The photo-inhibited quail had very small testes. Brains and testes of control and experimental quail were collected for receptor binding studies. The maximum number of binding sites (Bmax) of 2-[125I]iodomelatonin determined by saturation studies and the number of 2-[125I]iodomelatonin binding sites determined by a one-point binding assay in the testes of short-day quail were significantly lower (p < 0.05) than those of the testes in reproductively active birds kept under long photoperiod. There was no significant difference (p > 0.05) between the testicular Kd (equilibrium dissociation constant) values of these two groups. As for the Kd and Bmax of 2-[125I]iodomelatonin binding sites in the whole brain, there were no significant differences (p > 0.05) between the two groups. The higher level of testicular 2-[125I]iodomelatonin binding sites in photostimulated birds may be related to an up-regulation of melatonin receptors by the suppressed pineal melatonin secretion under long photoperiod. The lower testicular 2-[125I]iodomelatonin binding sites under short photoperiod may be the result of down-regulation of melatonin receptors by the stimulated melatonin pattern in the photo-inhibited birds.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of betaine on the growth performance of chicks inoculated with mixed cultures of avian Eimeria species and on invasion and development of Eimeria tenella and Eimeria acervulina in vitro and in vivo

At 7 d postinoculation (DPI) with a mixed culture of avian Eimeria species, 21-d-old chicks maintained in batteries and floor pens on a diet containing 0.15% (3 lb/ton) betaine plus 66 ppm (60 g/ton) salinomycin were significantly heavier and had significantly lower feed conversion ratios and mortality than chicks fed diets containing 0.15% betaine or 66 ppm salinomycin alone, or the control diet. At 31 DPI, when the chicks were 45 d old, the differences between the diet groups were not as great as at 7 DPI. In vitro, except at high concentrations, betaine was nontoxic to sporozoites of Eimeria tenella or Eimeria acervulina and had little effect on their invasion and development in cultured cells. In vivo, invasion by E. tenella and E. acervulina sporozoites was significantly reduced in all chicks fed diets containing betaine or salinomycin compared with that in control chicks. There was a significant interaction between betaine and salinomycin that impacted on invasion by both species. Overall development of E. tenella did not appear to be adversely affected by addition of betaine to diets containing salinomycin. Conversely, development of E. acervulina was reduced in chicks fed diets containing 0.075% (1.5 lb/ton) betaine plus 66 ppm salinomycin as compared with that in chicks fed salinomycin alone.     

Influence of mode and carbohydrate on the cytokine response to heavy exertion

1. This experiment was carried out to evaluate the productive and physiological consequences of a slight but long term food restriction of male broiler chickens from 2 commercial strains. 2. Cobb-500 and Ross chickens were submitted to a 20% food restriction from 8 to 21 d of age. Strain, food programme and their interactive effects were analysed in terms of consequences upon performance, mortality, incidence of sudden death syndrome (SDS) and ascites syndrome (AS), index of right cardiac hypertrophy and plasma concentrations of hormones related to metabolism and growth (T3, T4, T3:T4 ratio, IGF-I and GH). 3. Although some catch-up growth was observed by refeeding previously restricted birds after 22 d of rearing, food restriction decreased (P < or = 0.05) body weight at market age (42 d) irrespective of the strain, but improved (P < or = 0.05) food conversion. 4. The incidence of mortality was not high in non-restricted birds but SDS and AS caused more than 50% of deaths. Hypertrophic cardiac index was observed in chickens of both strains after 4 weeks of age and was higher in ad libitum fed birds. 5. During the period of food restriction, plasma T3 and IGF-I concentrations decreased whereas plasma T4 and GH concentrations increased compared to those of the age-matched ad libitum fed counterparts. During the subsequent ad libitum feeding period, few differences in circulating hormone concentrations were observed, except for the higher mean GH litres in previously food-restricted chickens at 35 d of age. 6. These results indicate that even a non-severe food restriction negatively affects body weight of 42-d-old male broilers but these are benefits with improved food efficiency and diminished mortality from metabolic disturbances. The hormone results suggest that the degree of food restriction applied was not severe because there was a very fast adaptive response with small and transient alterations in T3, T4 and GH plasma concentrations during the period of compensatory growth.     

Experimental toxoplasmosis in broiler chicks

To evaluate chicken toxoplasmosis both as an economic and a public health subject, 84 broiler chicks of a commercial strain, 30 days old, were distributed into seven groups of 12 birds (three replications of four chicks) experimentally infected with three developing T. gondii stages of the P strain as follows: tachyzoites, intravenous (two groups: 5.0 x 10(5) and 5.0 x 10(6)), cysts, per os (two groups: 1.0 x 10(2) and 1.0 x 10(3)) and oocysts, per os (three groups: 5.0 x 10(2), 5.0 x 10(3) and 5.0 x 10(4)). Twelve chicks received only a placebo (control group). During the next 30 days the following parameters were estimated: productivity (weight gain and feed conversion), clinical signs, including rectal temperature and parasitemia (bioassay). No clinical signs suggesting toxoplasmosis were seen and no statistical differences on productivity standards were found in comparison between inoculated and control chicks. However, fowls inoculated with tachyzoites and oocysts occasionally showed hyperthermia. Some haematological changes were detected in fowls inoculated with T. gondii. Anatomo-histopathological changes were not observed. From 14 parasitemias detected, 35.7% appeared on the 5th day after inoculation and 57.1% of them resulted from oocysts inoculation. After 30-35 days all birds were slaughtered: fragments from 12 organs or tissues from each of them were subjected to artificial peptic digestion and after that injected into T. gondii antibody-free mice (IIFR). T. gondii was detected in brain (12), pancreas (five), spleen (five), retina (five), kidney (two), heart (four), proventriculus (three), liver (two), intestine (two), lung (one), and skeletal muscle (one). Similar to observations with parasitemia, from 42 T. gondii isolations, 59.5% came from chicks which had received oocysts. It can thus be inferred that the developing form, expelled by cats, is the most important for T. gondii chicken infection and that brain is the most infected organ in birds. Attention must be paid to the potential importance of chicken meat in public health, since T. gondii was isolated from skeletal and heart muscles.     

The use of intermittent lighting in broiler raising. 2. Effects on the somatotrophic and thyroid axes and on plasma testosterone levels

Male and female broiler chicks were raised separately in nearly continuous lighting [23 h light (L):1 h dark (D), CL] and consumed feed ad libitum. At 7 d of age, the intermittent lighting schedule (1L:3D, IL) was imposed on half of the chicks, whereas the other chicks remained under CL. In addition to performance characteristics, several parameters of the somatotrophic and thyrotrophic axes were studied together with plasma concentrations of testosterone. Males had a higher growth rate than females regardless of the imposed lighting schedule and this pronounced growth difference is reflected by higher plasma concentrations of growth hormone (GH), and a better GH receptor occupancy. Differences in growth rate between sexes could not be attributed to differences in circulating 3,3',5-triiodothyronine (T3) levels or to hepatic deiodination activities. However, from 3 wk of age onwards, males had significantly higher plasma testosterone levels than females. Plasma GH and T3 levels decreased whereas plasma insulin-like growth factor-I and thyroxine levels increased with age in all experimental groups. The age-related decline in plasma GH levels were less pronounced for males than for females. No major changes in other hormonal parameters or deiodination activities could be observed as a result of imposing IL, except for the higher plasma GH levels of IL chickens, and for plasma testosterone concentrations in IL males at Day 41, which were twice the levels found in their CL counterparts. These results therefore suggest that the somatotrophic axis as well as circulating testosterone levels mediate the sex-related differences in growth rate and the compensatory growth as present in males.     

The impact of domestic violence on women''s mental health

Broiler chicks were spray treated on the day of hatch with titrated dosages (10(6), 10(7), or 10(8) anaerobic CFU) of a characterized competitive exclusion culture (CF3) and challenged orally on day 3 with 10(4) CFU of Salmonella typhimurium. On day 10, cecal contents from control and CF3-treated chicks were cultured for S. typhimurium to determine the minimal efficacious dosage of the CF3 culture. The experiment was repeated in three replicated trials. Resistance to Salmonella cecal colonization was dosage related and progressively enhanced at the 10(7)- and 10(8)-CFU dosages compared with the 10(6)-CFU dosage. The 10(7)-CFU dosage was selected as the minimal effective dosage and evaluated for efficacy during a 43-day broiler growout study. Six hundred broilers were spray treated on the day of hatch and compared with 600 controls. One-half of the control and CF3-treated birds were challenged orally on day 3 with 10(4) CFU of S. typhimurium and designated "seeders." The remaining unchallenged birds were designated "contacts." Compared with the controls, the recovery of Salmonella cells from the ceca of the CF3-treated broilers was significantly decreased (P < 0.01) in the challenged seeders on days 21 and 43 of growout. Salmonella contamination of floor pen litter was significantly reduced (P < 0.05) in pens of CF3-treated birds compared with controls. The transmission of Salmonella cells from seeder to contact birds in the same pens was decreased significantly (P < 0.01). The results indicated that treatment of broiler chicks on the day of hatch with the 10(7)-CFU dosage of CF3 culture effectively increased resistance to S. typhimurium challenge during growout to market age.     

The utilization of sodium in sodium zeolite A by broilers

Two identical experiments were conducted with 1-d-old broiler chicks to determine whether the Na in sodium zeolite A (SZA) was utilizable. Three male and three female chicks were randomly assigned to each of eight replicate pens per treatment. A corn-soybean meal basal diet was formulated to contain supplemental levels of 0, .02, .04, .06, .08, and .16% Na from either SZA or NaCl. The diets were isocaloric and isonitrogenous. The Cl level within each dietary Na level was kept constant. Feed and deionized water were offered for ad libitum consumption throughout each 21-d experiments. In both experiments, broiler body weight was increased with each addition of Na from either NaCl or SZA. In Experiment 1, the addition of Na, whether from NaCl or SZA, resulted in an improvement in feed consumption and feed conversion compared with birds fed the control diet. In Experiment 2, body weights of birds fed .04 to .08% Na from SZA were heavier than those fed the same levels from NaCl. Overall the addition of Na from SZA or NaCl resulted in an improvement in body weight, increased feed consumption, and improved feed conversion. Data from these experiments indicated that the Na in SZA was able to be utilized by broilers as efficiently as the Na from NaCl.     

Radiative heat loss in gentoo penguin (Pygoscelis papua) adults and chicks and the importance of warm feet

Adult penguins and their chicks differ considerably in their apparent body insulation. The chicks are covered in down, whereas the adults have the short, hard body feathers characteristic of the family, so mechanisms of heat loss may vary considerably between the two groups. We examined radiative heat loss by measuring body surface temperatures of gentoo penguins (Pygoscelis papua) in Antarctica. At the time the birds were considered to be in their thermoneutral zone, and there was little or no wind. Measurements of infrared emission were made on breeding adults and in large downy, and thermally independent, chicks in relation to environmental temperature. All 28 external body surface sites measured were positively correlated with ambient temperature, although there was considerable intersite variability in the relationship between site temperature and ambient temperature. Foot temperature increased most rapidly per degree ambient temperature increase, followed by the flippers, followed by the trunk. This pattern was particularly pronounced in the chicks, indicating that the exceptional heat-loss capacities of the feet may counteract for the reduced capacity of the flippers. Net heat transfer by radiation was examined using Stefan-Boltzmann's law and preliminary data on the surface area of a gentoo penguin body. This showed that between ground temperatures of 5 degrees and 15 degrees C overall heat transfer remains essentially constant, although radiative heat loss from the trunk decreases, this being counteracted by increasing heat transfer from the flippers and feet. Over the same temperature range the specific radiation heat transfer of the feet increased approximately 100 times faster per degree ambient temperature increase than did that of the flippers. This and the bimodality in foot temperature found in the study birds even under constant ambient temperatures indicate that within the thermoneutral zone heat loss by radiation in gentoo penguins is primarily executed using the feet, through which the blood circulates in pulses.     

Patterns, trends, and toxicological significance of chlorinated hydrocarbon and mercury contaminants in bald eagle eggs from the Pacific coast of Canada, 1990-1994

Bald eagle (Haliaeetus leucocephalus) eggs were collected during incubation, 1990-1992, from 16 nests near three bleached-kraft pulp mills, from six nests in the Fraser River estuary and from seven nests at a reference site on the Pacific coast of Canada. Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were present in all eggs in a qualitatively similar pattern among sites. Mean concentrations of 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) were significantly higher in eggs collected from near three kraft pulp mill sites in the Strait of Georgia (44, 45, 84 ng/kg) than from the reference area in Johnstone Strait (15 ng/kg). There were few differences among sites in mean organochlorine pesticide levels, indicating the diffuse distribution of those chemicals and the domination of atmospheric inputs. Mean concentrations of total polychlorinated biphenyls (PCBs) were highest in eggs from the Strait of Georgia (4.86 mg/kg) and the PCB congener pattern was significantly different between that area and both the lower Fraser valley and Johnstone Strait. Mean mercury concentrations, which were mainly methyl-mercury, were significantly higher in eggs collected from the lower Fraser Valley (0.258 mg/kg) and Johnstone Strait (0.294 mg/kg) compared to the Strait of Georgia (0.188 mg/kg). Individual and regional variation in concentrations of organochlorine pesticides, PCBs and mercury in eagle eggs were thought to be influenced mainly by dietary differences. Toxicologically, in 1990, mean TCDD-toxic equivalents (TEQs) in bald eagle eggs were about two-fold greater than a lowest-observed-effect level, suggested elsewhere for this species, of 210 ng/kg TEQs. In the Strait of Georgia, PCCDs and PCDFs made a greater contribution to TEQs than non-ortho and mono-ortho PCBs, whereas the reverse was true for eggs outside the strait. Mean eggshell thickness was less than the pre-1947 value at all sites, although there was no significant relationship between eggshell thickness and DDE concentrations. Levels of other organochlorine pesticides and mercury were below those considered to be toxic.     

Lead levels in exposed herring gulls: differences in the field and laboratory

We compared blood lead levels for herring gull (Larus argentatus) chicks exposed at two days of age in the field and the laboratory. One randomly selected chick in each family of three was injected with lead, the second with a sterile saline solution, and the third was not injected. Field birds were then completely free-living, and were entirely cared for by their parents. Blood was drawn at 35 or 45 days of age for comparison with laboratory-reared chicks. In both the laboratory and the field, blood lead levels were positively related to dose, and concentrations were lower at 45 than at 35 days of age. However, at each dose, the field birds had lower levels than did the laboratory birds. We postulate that this relates to higher overall activity and accelerated bone development in the field, and perhaps to a move varied diet. Wild young gulls were mobile and practiced flight more often than did laboratory-reared gulls. Growth metabolic, and behavioral factors may enhance deposition of lead in the bone, reducing blood lead. Thus, both in ecological risk assessments and in using birds as bioindicators, caution is required in extrapolating from laboratory studies in field conditions.     

Impairment of growth and immune function of avocet chicks from sites with elevated selenium, arsenic, and boron

Avocets (Recurvirostra americana) hatched from eggs collected from the south Central Valley of California (USA) were studied to determine the impact of elevated concentrations of selenium, arsenic, and boron on the immune system and growth to maturity. Corcoran ponds were the reference site with low selenium (1.2 ppb) and arsenic (29 ppb) (boron not measured). Westfarmers Pond had elevated concentrations of selenium (319 ppb), arsenic (127 ppb), and boron (109 ppm). Pryse ponds also had elevated selenium, arsenic, and boron concentrations (13.9 ppb, 1,100 ppb, and 29.4 ppm, respectively). Size at hatch was significantly reduced (P < or = 0.05) in birds from Westfarmers and Pryse ponds. The growth rate was faster, but mean adult size was reduced in birds from Pryse ponds. Avocet chicks from Pryse and Westfarmers ponds exposed solely through in ovo transfer of these elements had significantly increased heterophil:lymphocyte ratios. The phagocytic activity of macrophages also was significantly reduced in these birds, and Pryse Pond birds had an increased proliferative ability of lymphocytes in the presence of concanavalin A, a T-cell mitogen. Avocet chicks (< or = 5 wk old) were captured from the various ponds and the same morphometric and immune function measurements made. The birds that were most severely impacted by exposure to these compounds were those that were collected from Pryse ponds.     

Effects of light hatching on synapse number and size in the intermediate and medial part of the hyperstriatum ventrale of the domestic chick

The effects of pre-hatch light exposure on synaptic development in the intermediate and medial part of the hyperstriatum ventrale (IMHV) of the chick brain were investigated. Quantitative electron microscopical techniques were used to determine the size and numerical density of synapses and it was seen that in light hatched chicks there was a significant increase in the density of synapses in the left IMHV but that the size of synapses in these birds was decreased. These results provide a link between synaptic development and plasticity.     

Pulmonary arteriole hypertrophy in broilers with pulmonary hypertension syndrome (ascites)

Two experiments were conducted to determine the effect of low ventilation or cool temperature environments on pulmonary arteriole hypertrophy. Male broilers were maintained under control or low ventilation conditions in Experiment 1, whereas male broiler breeder by-product chicks were exposed to cool temperature conditions in Experiment 2. Birds were randomly selected for histological evaluation of lung tissue in both experiments. In Experiment 1, birds that had pulmonary hypertension syndrome (PHS+) exhibited a greater degree of inflammation of lung tissue at 5 and 7 wk of age than controls or birds that did not have PHS (PHS-). These PHS+ birds also had higher numbers of cartilaginous osseous nodules at 3 and 7 wk of age than controls. Morphometric analyses revealed that PHS+ birds in Experiment 1 had a thicker medial layer associated with 100 to 200 microns diameter pulmonary arterioles at 7 wk of age, and 50 to 100 microns arterioles at 3 and 7 wk of age than PHS- or control birds. In Experiment 2, PHS+ birds exhibited a thicker medial layer in pulmonary arterioles at 7 wk of age than did PHS- birds, but there were no differences in medial layer thickness at 5 wk of age nor were there differences in the degree of inflammation or amount of osseous nodule formation between PHS+ and PHS- birds at 5 and 7 wk of age. Thus, pulmonary arteriole hypertrophy was observed in birds having PHS in response to both low ventilation and cool temperature environments and this hypertrophy occurred with or without a coincident inflammatory response in lung tissue.     

Comparative High-Temperature Corrosion Behavior of Ni-20Cr Coatings on T22 Boiler Steel Produced by HVOF, D-Gun, and Cold Spraying

To protect materials from surface degradations such as wear, corrosion, and thermal flux, a wide variety of materials can be deposited on the materials by several spraying processes. This paper examines and compares the microstructure and high-temperature corrosion of Ni-20Cr coatings deposited on T22 boiler steel by high velocity oxy-fuel (HVOF), detonation gun spray, and cold spraying techniques. The coatings’ microstructural features were characterized by means of XRD and FE-SEM/EDS analyses. Based upon the results of mass gain, XRD, and FE-SEM/EDS analyses it may be concluded that the Ni-20Cr coating sprayed by all the three techniques was effective in reducing the corrosion rate of the steel. Among the three coatings, D-gun spray coating proved to be better than HVOF-spray and cold-spray coatings.     

Resistance against Salmonella enteritidis cecal colonization in Leghorn chicks by vent lip application of cecal bacteria culture

Leghorn chicks were treated with cultures of cecal bacteria from adult chickens by crop gavage, upper body spray, or vent lip application on the day of hatch. The chicks were challenged orally with 10(4) Salmonella enteritidis (SE) at 3 d of age and evaluated for SE cecal colonization at 10 d of age. The concentration of volatile fatty acids (VFA) in the cecal contents was determined on the day after culture treatment and at 10 d of age. Compared with controls, SE colonization was significantly decreased in each of the treatment groups. Vent lip application of a single .05-mL drop of cecal bacteria culture resulted in resistance against SE challenge comparable to crop gavage or spray treatment with .5 mL of culture. Resistance to SE challenge was directly associated with the concentrations of total VFA and propionic acid in the cecal contents of the treated chicks on the day after culture treatment. The results indicated that cecal bacteria from adult chickens that increase SE colonization resistance may rapidly become established in the ceca of newly hatched chicks following contact with the vent lips.     

Doxorubicin hydrochloride, cyclophosphamide, and 5-fluorouracil combination in advanced prostate and transitional cell carcinoma

Hubbard cockerels, 1 day of age (n = 91), were divided into 3 handling groups: (1) chicks from the 5-Day group were removed from the brooder and isolated at 22 degrees C for 3 min on each of the first 5 days; (2) chicks from the 15-Day group received this treatment for 15 days; and (3) Control chicks were not handled. Within each group half were fed broiler starter for 5 weeks, and half were fed layer starter which produces slower growth. On Days 28, 35, 42, and 49 the average weight of 5-Day birds was significantly higher than that of Controls; 15-Day birds weighed slightly less than birds in the 5-Day group. The weight advantage of the 5-Day birds occurred with both starter rations, at all weighing periods, and did not appear to reflect increased food consumption. Similarities between these findings and results obtained with rodents were noted.     

Effects of dietary boron supplementation on broilers

Two experiments were conducted with a total of 432 broiler chicks to investigate the influence of supplementing different amounts of boron to practical corn-soybean meal diets. The birds were housed in batteries and had free access to feed and water. In Experiment 1, 144 1-day-old broiler chicks were fed a basal diet supplemented with 0, 5, 40, 80, or 120 ppm boron for 21 days. Female body weight was not influenced by the dietary treatments. However, males supplemented with 5 ppm boron were heavier and their tibias resisted more load than the control birds. Overall feed conversion was not influenced by boron. In Experiment 2, 288 1-day-old broiler chicks were fed a basal diet supplemented with 0, 60, 120, 240, or 300 ppm boron for 22 days. Male and female body weights of the 300-ppm group were lower than those of the control birds. Percentage tibia ash was highest with 300 ppm boron. No significant differences were found in intestinal tract weight (grams of intestine per 100 g body weight) among treatments. Boron concentration in the breast muscle and liver increased as dietary concentration of boron increased. Data collected in these two experiments indicated that consumption of diets containing up to 240 ppm boron from hatch to 21 days of age was not detrimental to broiler performance. Data were not conclusive on the need for supplemental boron in broiler diets based on corn and soybean meal.     

Effects of social isolation and social separation in domestic chicks.

Conducted 2 experiments with 60 white Leghorn chicks, with subsamples of 24 and 36 animals tested in 2 independent replications, to assess the impact of early social isolation and social separation on the behavior of domestic chicks. In Exp I, a 3-wk longitudinal study, the day-to-day behavior of isolated chicks was compared to the behavior of birds housed in pairs. Ss in a 3rd group were reared in pairs for 2 wks, and then were permanently separated. The daily observations of all Ss recorded disturbance reactions, exploratory activities, consummatory behavior, grooming, and inactivity. In Exp II, 36 Ss from the 3 experimental conditions were tested in the 4th posthatch week for general social responsiveness in the presence of unfamiliar conspecifics. Results show that (a) both isolation and separation produced behavioral anomalies; (b) separated Ss' reactions indicated patterns analogous to post-separation patterns seen in other species; and (c) the effects of isolation and separation were not qualitatively equivalent--exposure to conspecifics revealed antisocial behavior in the isolates, relative to the responses of their socially reared and separated counterparts. Results are discussed in terms of a model for differences in the essence and consequences of early social isolation and social separation. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thyroid hormones and thyrotropin in liver and kidney insufficiency

In 22 patients with hepatic or renal insufficiency the serum concentrations of trijodothyronin, thyroxine and thyrotropin and also the T4-binding capacity of TBG were determined. The mean serum T3 concentration was found to be significantly lower in patients with hepatic coma when compared with euthyroid subjects. In the cases of renal insufficiency the serum T3 concentrations were in the normal range. Due to hormone loss through dialysis however, the mean value of the T3 concentrations was slightly lower than the average concentration of normal subjects. The obtained results agree with those of our earlier studies which showed that there are significant differences between liver artery and vein T3 concentrations in serum, whereas no such differences could be ascertained between serum concentrations in renal artery and vein. On the basis of these findings it is assumed that conversion of T4 into T3 occurs predominantly in the liver.     

Effect of vasoactive drugs on muscle fibre types and capillaries

Photosensitive great tits (Parus major) and willow tits (P. montanus) were exposed to long days (20L:4D) under three different temperature conditions (4+, +10, and +20 degrees C) in early winter. The two species showed significant differences in their LH and testicular reaction patterns to low temperatures. Testes showed pronounced growth cycles under all temperature regimes. For the willow tit, testes in birds kept at +20 degrees C reached maximum size about 2 weeks earlier than testes in birds living under the two lower temperature regimes, whereas in the great tit testes reached maximum size at about the same time in all three groups. Low temperatures delayed the onset of testicular regression in both species. Plasma levels of LH did change with time in both species. However, the patterns of the induced LH-cycles in the three great tit groups differed significantly from each other, whereas this was not the case for the willow tits. The LH cycle was especially pronounced in great tits kept at +20 degrees C. The initial LH peak in great tits kept at +4 and +10 degrees C was about 50% lower than in great tits kept at +20 degrees C. These results are discussed in relation to species differences in winter ecology and establishment of breeding territories.