After intravenous injection of 50 g glucose the blood glucose concentration in sows declined very quickly from the high concentrations initially found. The blood glucose concentration always returned to the fasting concentration within the period 18-45 min after glucose injection. The rate at which the glucose was removed was a function of the total blood glucose concentration.After the blood glucose concentration returned to the fasting concentration, the concentration continued to fall, concentrations of 5-10 mg/100 ml. being achieved regularly with no overt signs of hypoglycaemia.The time required for the blood glucose concentration to return to the fasting glucose concentration was found to be the most repeatable quantitative assessment of the test in the pig.A systematic study of the tolerance of sows to intravenous injections of glucose has not been reported, although several workers have studied the intravenous glucose tolerance of immature pigs [Hanawalt, Link and Sampson, 1947; Link, 1953;Meyer, Briskey, Hoekstra and Bray, 1962;Curtis, Heidenreich and Folley, 1966]. In addition none of these workers made any attempt to assess the results of an intravenous glucose tolerance test (IVGTT) in a quantitative manner such as was described by Duncan [1956] in his work with man. The aim of the work reported in this paper was to develop a method of assessing quantitatively the results of an IVGTT in the sow, and to determine whether there was a sufficient range in the glucose tolerance between sows to merit studies now proceeding of any possible relation between the sow's glucose tolerance and the birth weight of her litters. A relation of this nature had already been demonstrated in the case of man where a state of diabetes or pre-diabetes results in heavier babies at birth [Kyle, 1963].
METHODSThe animals used were Large White sows drawn from the Rowett Research Institute pig herd. The tests were undertaken either when the animals were non-pregnant and had not been lactating for some weeks or in the first 14 days of pregnancy. Animals were given a uniform feed intake of 2-2 kg per day of a standard diet [Elsley, Anderson, McDonald, McPherson and Smart, 1966] and had been receiving this diet for at least three weeks prior to the test. On the day before the test, an indwelling catheter was placed in the jugular vein, and in some cases in the carotid artery, using a method described previously [Anderson and Elsley, 1969].On the morning of the test, three initial samples of blood were withdrawn from the animal by means of the catheter. A standard dose of 50 g of glucose in 50 per cent * Present address: Institute of Animal Physiology, Babraham, Cambridge. 104