Caecal growth in the domestic fowl following surgical manipulation.

1. Some effects of removing increasing proportions of the left caecum on the remaining caecal tissue and on the right caecum were studied in young chicks during a period of 35 d. The chicks were 22 d old when the operations were carried out. 2. No differences were detected between the gains in weight of the control and experimental groups of birds. 3. A marked negative linear relationship was observed between the dry weight of the amount of caecal tissue removed when the birds were 22 d old and weight of the left caecum at the end of the experiment. 4. The average growth rate of the left caecum (g dry tissue/week) was found to be dependent on the estimated weight of caecal tissue remaining after surgery. 5. No evidence was obtained to indicate that the growth of the right caecum responded to the removal of the left caecal tissue. 6. The morphology and histology of the operated caeca were found to be similar to the equivalent regions of the unoperated caeca. Surgical interference was not followed by any major changes in mucosal architecture. 7. In birds which had experienced unilateral caecectomy, the discharge of caecal faeces usually stopped for about 2 d. When caecal defaecation was resumed, the pattern of defaecation appeared to be the same as that observed in sham-operated birds with both caeca intact.

Coccidial infection with Eimeria tenella and caecal defaecation in chicks.

1. The periodicity of caecal defaecation was investigated in chicks infected with Eimeria tenella. The birds were illuminated for 12 h/d (07.00-19.00) and faeces were collected at 3-h intervals for up to 21 d. 2. In uninfected birds caecal faeces were never collected during the dark period. During the periods 07.00-10.00 h, 10.00-13.00 h, 13.00-16.00 h and 16.00-19.00 h, caecal defaecation occurred on approximately 44, 19, 55 and 91% of the total number of days respectively. 3. In infected birds production of haemorrhagic caecal faeces began from between 90 and 156 h after infection and continued during both light and dark periods for between 12 and 48 h. After this period, no caecal faeces were observed for between 39 and 120 h. Normal caecal defaecation resumed from between 198 and 264 h.

Acute cold exposure and the metabolism of glucose and some of its precursors in the liver of the fed and fasted sheep.

Measurements of total body oxygen consumption, visceral and hepatic blood flow, oxygen consumption, exchanges of amino acids, lactate, pyruvate and glucose were made on sheep fed 3--6 h or 21 h before the experiment and exposed for 3 h to a neutral environment (15 degrees C) or a cold environment (0.5 to 4 degrees C with clipped coat and wind speed 2 m.s-1). Recent feeding significantly increasedd the total oxygen consumption and the oxygen consumption of the viscera and liver. No general release of amino acids from the viscera or uptake by the liver after feeding was detected although the arterial plasma concentration of essential amino acids did increase significantly after feeding. The plasma concentration of most non-essential amino acids also increased except that of glycine, which decreased significantly. Cold exposure increased the total oxygen consumption and reduced the respiratory quotient significantly. Release of amino acids from the viscera was stimulated by cold exposure. There was a variable increase in the hepatic uptake of lactate and alanine when the sheep were fasted and cold-exposed. The liver's glucose output doubled and the blood (arterial) glucose concentration significantly increased in the cold.

Changes in the metabolism of the shivering hind leg of the young ox during several days of continuous cold exposure.

The effect of 4 days of continuous exposure to a cold environment on blood flow in, and oxygen and energy substrate uptake by the shivering hind leg has been studied in young steers. The animals shivered throughout the period of cold exposure and total oxygen consumption (total VO2) remained 40-50% greater than VO2 during thermoneutrality. Leg blood flow (leg Q) and oxygen uptake (leg VO2) increased two- and four-fold respectively on the first day of cold. Both had declined significantly by the final day, leg Q to a level 37% greater than, and leg VO2 to about double, pre-cold levels. The change in the relationships of leg Q and leg VO2 to total VO2 was examined by linear regression analysis, which suggested that the changing contribution of leg VO2 to total VO2 was entirely due to changes in leg Q, rather than in the arteriovenous difference in blood oxyhaemoglobin saturation across the leg. The net uptakes by the leg of free fatty acids (FFA), acetate, glucose and lactate all increased on the first day of cold. Both glucose and acetate uptakes were greater on day 4 than on day 1 in the cold, in spite of the lower leg VO2, but net uptakes of FFA and lactate were considerably lower. The decrease in net uptake of FFA is attributed mainly to an increase in the rate of lipolysis and release of FFA from fat depots in the leg, because of the associated progressive increase in the release of glycerol and oleic acid from the leg. The molar ratios of net carbohydrate substrate, acetate and FFA uptakes to leg VO2 are compared. The results suggest that tissues other than the leg muscles become increasingly important as sites of heat production, and that there are changes in the utilization of glucose, acetate and FFA by shivering muscle, during prolonged cold exposure.