Defaunated sheep offered lucerne hay or dried red clover were used to study digestion in the stomach of dietary organic matter, plant cell wall constituents, and plant cell contents. Digestion in that section of the tract was, for dietary organic matter, 50 % with lucerne and 60% with red clover, for plant cell contents 65–70% with both diets, and for plant cell wall constituents 30% with lucerne and 60 % with red clover. Estimates of growth of rumen bacteria in these sheep indicated that about 32 g of bacterial organic matter and 23 g of bacterial crude protein were synthesized in the rumen for each 100 g of plant organic matter digested. Comparisons of apparent digestion in the stomach and intestines were made between the defaunated sheep and the same sheep carrying a normal population of rumen microorganisms. Levels of rumen ammonia were lower in the absence of protozoa. However, only small differences were observed in the flow of digesta along the tract and in the apparent digestion of organic matter and nitrogen in both the stomach and intestines as a result of defamation. Hence it is suggested that data on the digestion of forages obtained with defaunated sheep can be applied to sheep with rumen protozoa.

A study was made of the composition, intake, and digestion of dried Phalaris tuberosa forage that had been harvested at three stages of maturity. Advancing maturity was associated with: (i) decreased food intake; (ii) increased expenditure of time and energy in chewing activities; (iii) decline in the rate of flow of digesta from the abomasum though not from the rumen; (iv) decline in digestibility in the whole tract of organic matter, nitrogen, and the structural carbohydrates; (v) decline in the digestion of fibre in the rumen relative to that occurring in the whole tract; (vi) decline in the quantities of volatile fatty acids and amino acids made available to the animal. By contrast only small differences attributable to maturity were observed in: (i) the distribution of digestion of organic matter between stomach and intestines; (ii) the digestibility of nitrogen other than ammonia in the intestines; (iii) the proportions of digestible organic matter derived from volatile fatty acids and amino acids; (iv) the proportions of individual amino acids in the digesta passing to the intestine. It was calculated that microbial piotcin contributed 33, 38, and 47% of the protein passing from the stomach to the intestincs with the diets of advancing maturity. Most of the remaining protein was presumably of dietary origin. About 80% of the crude protein in the digesta was present in the form of amino acids, and the quantities of amino acids released in the intestines were calculated to be equivalent to 64–66 g/100 g crude protein intake. With advancing maturity of the diets the plasma levels of the essential ammo acids except lysine, histidine, and arginine declined; there was little effect of diet on the plasma levels 01 non-essential amino acids. However, relative to total essential amino acids, the ratios of valine and leucine decreased with advancing maturity of the diet while those of lysine, histidine, glutamate, glycine, alanine, and serine increased. * Part 111, Aust. J. Agric. Res., 1969, 20, 347.

Aims/hypothesis. Glycation of insulin, resulting in impaired bioactivity, has been shown within pancreatic beta cells. We have used a novel and specific radioimmunoassay to detect glycated insulin in plasma of Type 2 diabetic subjects. Methods. Blood samples were collected from 102 Type 2 diabetic patients in three main categories: those with good glycaemic control with a HbA 1c less than 7%, moderate glycaemic control (HbA 1c 7-9%) and poor glycaemic control (HBA 1c greater than 9%). We used 75 age-and sex-matched non-diabetic subjects as controls. Samples were analysed for HbA 1c , glucose and plasma concentrations of glycated insulin and insulin.Results. Glycated insulin was readily detected in control and Type 2 diabetic subjects. The mean circulating concentration of glycated insulin in control subjects was 12.6±0.9 pmol/l (n=75). Glycated insulin in the good, moderate and poorly controlled diabetic groups was increased 2.4-fold (p<0.001, n=44), 2.2-fold (p<0.001, n=41) and 1.1-fold (n=17) corresponding to 29.8±5.4, 27.3±5.7 and 13.5±2.9 pmol/l, respectively. Conclusion/interpretation. Glycated insulin circulates at noticeably increased concentrations in Type 2 diabetic subjects. [Diabetologia (2003) [1]; the process of glycation in the beta cell is rapid and occurs in a time-and concentration-dependent manner [2]. Previous studies have shown that glycated insulin has a reduced ability to regulate plasma glucose homeostasis in vivo and to stimulate adipose tissue lipogenesis or glucose uptake and oxidation by isolated diaphragm and abdominal muscle in vitro [3,4,5]. Studies in healthy human volunteers using the hyperinsulinaemic-euglycaemic glucose clamp technique suggest that glycated insulin could contribute to insulin resistance in Type 2 diabetes mellitus [6].The site of glycation of human insulin has now been identified by electrospray tandem mass spectrometry as the N-terminal Phe 1 of the B-chain [7], enabling the development of a sensitive and specific radioimmunoassay to measure concentrations of glycated insulin and to identify glycated insulin in pancreatic islets using immunohistochemistry [8]. High performance liquid chromatography techniques used previously were neither sensitive nor reliable Formation of advanced glycation-end products (AGEs) plays an important role in long-term metabolic consequences of diabetes including ophthalmic, renal and atherosclerotic vascular complications. Glycation has been shown also to interfere with normal cellular functions including the activities of various enzymes such as Cu-Zn superoxide dismutase and several other peptide hormones. A growing body of evidence now exists to support the hypothesis that glycation of insulin in pancreatic beta cells occurs under conditions of hyperglycaemia. Glycated insulin has been identified in the pancreas of normal and diabetic animal models

Young sheep were used in feed intake and digestion studies with a wheaten straw diet of low sulfur (S) content (0.71 g S kg-1 organic matter) fed without additional S (low S diet) or containing sodium sulfate (high S diet). With the high S diet, relative to the low S diet, (i) the levels of sulfide in rumen liquor were elevated, (ii) less time was spent in ruminating activities, (iii) rumen liquor volume tended to be lower (-l0%), (iv) indigestible markers were cleared more rapidly from the rumen (approx. +16%), (v) more organic matter (OM) and acid detergent fibre were digested in the stomach and in the alimentary tract as a whole (+8-16%), (vi) more non-ammonia nitrogen (NAN) flowed into the intestines (+13%) and this NAN had a higher content of sulfur amino acids (+ 17%), (vii) a greater quantity of NAN was digested in the intestines per unit of digestible OM intake (+ 12%), (viii) the concentrations of various amino acids in venous blood were substantially lower, and (ix) fungal activity in the rumen was higher. The number of bites performed on each rumination bolus was inversely related to fungal activity in the rumen, but the latter was not related to OM digestibility or to the sulfur amino acid content of the NAN flowing into the intestines. The OM digestibility was inversely related to the rate of clearance of markers from the rumen with the low S diet but not the high S diet. Voluntary feed consumption was similar with both diets, and in the low S diet it was inversely related to OM digestibility and positively related to marker clearance rate from the rumen. Digestible OM intake under conditions of ad libitum feeding was higher with the high S diet (+11%) and positively related to fungal activity in the rumen and to the sulfur amino acid content of the NAN flowing into the intestines. The data indicate that an inadequate amount of S in the low S diet impaired the metabolism of the rumen microbiota which in turn affected variables relating to digestion and metabolism. A quantitatively significant role for the anaerobic fungi in the structural degradation of fibre is suggested and attention is drawn to the need for studies on both feed consumption regulation with low S diets and the relation between herbage S status and the sulfur amino acid content of the rumen microbiota.

The digestion of nitrogen other than ammonia (NAN) in the small intestine of sheep fed on forage diets has been estimated by developing a structural relationship y = a+bx, where y = NAN (g/d) leaving the ilium and x = NAN leaving the abomasum. In this relationship the intercept a represents endogenous NAN passing from the ileum and the slope b the indigestibility of abomasal NAN; hence ( 1-b ) gives true digestibility. The values obtained (mean &SE) were: a = 1.04�0.32 and b = 0.34 � 0.02 , which indicated that the true digestibility of NAN leaving the abomasum was 66%. The amino acid composition of endogenous NAN leaving the ileum was estimated in ileal fluid collected from sheep whose rumens had been emptied and which were maintained by infusion of volatile fatty acids, minerals, vitamins and small amounts of amino acids into the stomach. The values obtained did not differ substantially from mean values obtained for abomasal and ileal digesta from sheep fed on four forage diets. Total amino acids (g/16 g NAN) in abomasal and ileal digesta and endogenous ileal fluid were 74.4, 62.9 and 82.5 respectively. From information on the true digestibility of abomasal NAN and the amino acid composition of digesta, estimates were made of the true absorption coefficients of individual amino acids from the small intestine. Values were mostly greater than 70% of the amount leaving the abomasum but for cystine the value was only 52%.