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Biomedical subjects

A H Sykes

Publications and source records attributed to A H Sykes.

At least 19 recordsLinked to original sources
PubMed1987

Detoxication of cyanide in the chicken by conversion to thiocyanate, as influenced by the availability of transferable sulphur.

The urinary excretion of thiocyanate by hens after dosage with cyanide (30 mumol) has been studied in a series of acute experiments involving 6 hr urine collection periods. More than half of the dose could be recovered as thiocyanate when cyanide was given by intravenous infusion and the rate of excretion closely paralleled plasma thiocyanate concentration. Little cyanide was excreted directly. The excretion of thiosulphate fell by an amount that suggested that availability of sulphane sulphur might limit the extent of conversion. However, neither thiosulphate nor sulphur amino acids enhanced thiocyanate excretion when they were infused together with cyanide; indeed, thiocyanate excretion decreased as the level of sulphur compound given was increased. Both nitrite and sulphite depressed thiocyanate excretion also but they differed in their effects on plasma thiocyanate levels and the pattern of urinary excretion. Comparison of excretion from both sides of the kidneys separately emphasised the importance of the first pass of cyanide in its conversion to thiocyanate. The results suggest that although sulphur availability may be limited the in vivo production of sulphite also restricts cyanide detoxication.

Animals↗
PubMed1986

Acclimatization of the fowl to intermittent acute heat stress.

The acclimatization of poultry to a hot, dry climate was assessed by studying changes in rectal temperature (Tr) during regular daily exposure to an ambient temperature of 38 degrees C and 26% RH. Laying hens of two strains, young chicks, growing broilers and broiler breeders were able to acclimatise, in varying degrees, to these conditions. Acclimatization was characterised by a progressive reduction in the rate of increase in Tr over the period of exposure and the ability to survive conditions that initially would have been fatal. Laying hens could acclimatise if prevented from displaying their normal postural responses to heat stress. Acclimatization was accompanied by a decrease in oxygen consumption when measured at either the acclimatization temperature or at a thermoneutral temperature.

Acclimatization↗
PubMed1986

Effect of a change in environmental temperature on heat tolerance in laying fowl.

Laying hens when transferred from accommodation at an ambient temperature (Ta) of 30 degrees C to one of 20 degrees C failed to acclimatise to intermittent heat stress (Ta 38 degrees C) commencing one day after the transfer. After 21 d of intermittent exposure to 38 degrees C these hens showed little or no increase in heat tolerance, whereas hens living constantly at either Ta 20 degrees C or 30 degrees C acclimatised normally. The failure to acclimatise was also observed when hens were transferred from Ta 30 degrees C to 5 degrees C but not when transferred from Ta 5 degrees C to 30 degrees C. The failure to acclimatise following transfer from a warm to a cool environment was accompanied by an increase in food intake; if food intake was not allowed to increase the hens acclimatised normally to heat stress.

Acclimatization↗
PubMed1986

Effect of changes in dietary energy intake and environmental temperature on heat tolerance in the fowl.

The improvement in heat tolerance acquired during the acclimatization of laying hens to intermittent heat stress was lost or considerably reduced when energy intake increased following the addition of maize oil to the diet. The oxygen consumption (VO2) of acclimatised hens increased after the addition of maize oil to the diet. Reducing the environmental temperature (Ta) from 30 degrees to 10 degrees C prevented the development of acclimatization if the heat stress commenced soon after the change of Ta; if the heat stress commenced 5 weeks after the change of Ta acclimatization took place normally. Reducing the Ta from 30 degrees to 10 degrees C resulted in an increased VO2 and food intake. The administration of triiodothyronine increased VO2 and reduced the heat tolerance of acclimatised hens. It is concluded that heat tolerance, despite being reinforced by regular exposure to heat stress, remains susceptible to changes in energy metabolism brought about by dietary or environmental means.

Acclimatization↗
PubMed1986

Transfer of thiocyanate into chicken eggs.

Laying hens were fed thiocyanate (SCN) as a solution of potassium thiocyanate (KSCN) in their drinking water to determine whether dietary SCN was transferred into eggs. The thiocyanate content of their eggs was measured before and during thiocyanate administration. Egg thiocyanate content increased from 6 micrograms SCN/g albumen to 31 micrograms SCN/g (a 400% increase) in the period immediately following thiocyanate administration and then fell progressively, seeming to stabilize much closer to but still well above control levels.

Administration, Oral↗
PubMed1985

Food intake of the laying hen following crop loads of maize oil and other nutrients.

The metabolisable energy (ME) of the diet of laying hens at an ambient temperature (Ta) of 20 degrees C was abruptly changed from 10.9 MJ/kg to 12.9 MJ/kg, or vice versa. Food intake during the next 14 d was significantly reduced by the low ME diet and was increased by the high ME diet, that is, the expected compensatory changes in food intake did not occur. Laying hens given the same change of diet as above but kept at 32 degrees C did not show any change in food intake within 14 d. Thus ME intake increased with the high ME diet and decreased with the low ME diet. Daily doses of 10 ml maize oil/kg body weight given directly into the crop of laying hens at a Ta of 20 degrees C, resulted in an immediate, significant, reduction of food intake such that total ME intake remained the same as with normal feeding. Daily doses of 3 ml maize oil/kg, given as before, resulted in an immediate, significant, reduction in food intake at a Ta of 20 degrees C but at a Ta of 32 degrees C food intake remained unchanged; consequently daily ME intake increased. Loading the crop with glucose or sucrose, at Ta 20 degrees C, in quantities which provided a similar ME as 3 ml maize oil/kg, reduced food intake but the adjustment was less precise and daily ME intake increased. Loading with glycerol or protein hydrolysate decreased both food and ME intake. Crop loads of starch were as effective as maize oil in bringing about a significant and compensatory reduction of food intake. Similar volumes of water or liquid paraffin placed in the crop did not affect food or ME intake. A similar weight or cellulose placed in the crop reduced food and ME intake.

Animals↗
PubMed1982

Thermal panting and respiratory alkalosis in the laying hen.

1. Changes in respiratory rate (f), rectal temperature (Tr) and blood acid-base values were measured in laying hens exposed to ambient temperatures (Ta) of 32, 35, 38 or 41 degrees C. 2. At Ta 32 degrees C there was no panting. At Ta 35 degrees C panting occurred without any increase in Tr but there was a slight alkalosis (pH 7.55). 3. At Ta 38 degrees C Tr increased and panting was accompanied by moderate alkalosis (pH 7.58). 4. At Ta 41 degrees C Tr increased considerably and severe alkalosis developed (pH 7.65). 5. From the relation between Tr, f and pH it is concluded that some degree of alkalosis is a normal response to panting in the laying hen.

Alkalosis, Respiratory↗
PubMed1982

The respiratory responses of the fowl to hot climates.

Respiratory rate (f) and tidal volume (VT) have been measured at normal and at warm ambient temperatures (Ta) in adult domestic fowl by means of a whole body plethysmograph. Resting values of f = 23 +/- 9 min-1 and of VT = 25.6 +/- 0.9 ml min-1 were found. At Ta 30, 35 or 40 degrees C f increased in direct relation to the severity of the heat stress reaching a maximum values of 273 +/- 12 min-1; VT fell uniformly in all three climates to a minimum of 9.0 +/- 0.5 ml. Total ventilation (V) showed a linear relation with f during first-phase panting. Second-phase panting occurred only at Ta 40 degrees C; V increased at first but subsequently fell as the decline in f became more pronounced.

Acclimatization↗