Fermentation in the small intestine contributes substantially to intestinal starch disappearance in calves.

BACKGROUND: The proportion of starch disappearing from the small intestinal lumen is generally lower in ruminants than in monogastric animals, and there are indications that the starch digestion capacity in ruminants is limited. OBJECTIVES: Milk-fed calves were used to study the rate-limiting enzyme in starch hydrolysis and to quantify starch fermentation in ruminants. METHODS: Forty male Holstein-Friesian calves were fed milk replacer containing either lactose (control) or 1 of 4 corn starch products. The following starch products differed in the enzyme ratios required for their complete hydrolysis to glucose: gelatinized starch [α-amylase and (iso)maltase], maltodextrin [(iso)maltase and α-amylase], maltodextrin with α-1,6-branching (isomaltase, maltase, and α-amylase), and maltose (maltase). In the adaptation period, calves were stepwise exposed to an increasing dose of the starch product for 14 wk to allow maximal adaptation of all enzyme systems involved. In the experimental period, apparent total tract and ileal starch product disappearance, total tract starch product fermentation, and α-amylase, maltase, and isomaltase activities were determined at 18% inclusion of the starch product. RESULTS: Maltase and isomaltase activities in the brush border did not increase for any of the starch product treatments. Luminal α-amylase activity was lower in the proximal (3.9 ± 3.2 and 2.7 ± 1.7 U/mg Co for control and starch product calves, respectively) but greater in the distal small intestine of starch-fed calves than in control calves (0.0 ± 0.0 and 6.4 ± 1.5 U/mg Co for control and starch product calves, respectively; means ± SEs for control and means ± pooled SEMs for starch product treatments). Apparent ileal (61.6% ± 6.3%) and total tract (99.1% ± 0.4%) starch product disappearance did not differ between starch product treatments, suggesting that maltase activity limits starch digestion in ruminants. Total tract starch product fermentation averaged 414 ± 43 g/d, corresponding to 89% of intake, of which half was fermented before the terminal ileum, regardless of starch product treatment. CONCLUSION: Fermentation, rather than enzymatic digestion, is the main reason for small intestinal starch disappearance in milk-fed calves.

Dietary pectin and mango pulp effects on small intestinal enzyme activity levels and macronutrient digestion in grower pigs.

The effects of refined pectin and mango pulp on macronutrient digestion and small intestinal enzyme activity were studied in grower pigs. Diets based on wheat starch with and without apple pectin or dried mango fruit pulp were fed to 30 grower pigs for 21 days. Pigs were euthanized two hours postprandially, and their gastrointestinal contents recovered. Starch and protein digestion as well as α-amylase activity were all increased in pigs fed pectin. In contrast, fat digestion, lipase and protease (trypsin) activities were all significantly reduced in these pigs. Pigs fed the mango fruit pulp diet had intermediate effects compared with pigs fed refined pectin and control diets. The data suggests that pectin has a significant effect on digestive enzyme activity and subsequent influence on macronutrient digestion. The fact that pectin caused either an increase (α-amylase) or decrease (lipase, protease) in enzyme activity in digesta, which either did (starch, lipid) or did not (protein) associate with residual nutrient differences illustrates the complexity of small intestinal responses to added fibre in diets.

Male grower pigs fed cereal soluble dietary fibres display biphasic glucose response and delayed glycaemic response after an oral glucose tolerance test.

Acute and sustained soluble dietary fibre (SDF) consumption are both associated with improved glucose tolerance in humans and animal models (e.g. porcine). However, the effects on glucose tolerance in grower pigs, adapted to diets with a combination of SDF have not been studied previously. In this experiment, cereal SDF wheat arabinoxylan (AX) and oat ß-glucan (BG) were fed individually and in combination to determine the effect on glucose tolerance in jugular vein catheterized grower pigs. Five groups of Large White male grower pigs were fed highly digestible diets containing either 10% AX, 10% BG, 5% AX with 5% BG, a model cereal whole wheat flour (WWF), or a control wheat starch diet (WS) with no SDF. Blood was collected via jugular vein catheters over 240 minutes following a feed challenge and an oral glucose tolerance test (OGTT) on two separate days. Postprandial blood samples were used to determine plasma glucose, insulin, non-esterified fatty acids (NEFA), glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), peptide tyrosine tyrosine (PYY), ghrelin, glucagon and cortisol concentrations. No dietary effects on glycaemic response were observed following the feed challenge or the OGTT as determined by the area under the curve (AUC). A biphasic glucose and insulin response was detected for all pigs following the OGTT. The current study showed male grower pigs have tight glycaemic control and glucose tolerance regardless of diet. In addition, pigs fed the combined SDF had a reduced GIP response and delayed insulin peak following the feed challenge. Incretin (GLP-1 and GIP) secretion appeared asynchronous reflecting their different enteroendocrine cell locations and response to nutrient absorption.

An updated method for the jugular catheterization of grower pigs for repeated blood sampling following an oral glucose tolerance test.

Jugular catheterization is a common procedure used under experimental conditions. However, there is considerable variation in the reported techniques, particularly for grower pigs (>40 kg and <60 kg) when larger volumes of blood per sample (>10 mL) are required. This paper provides a complete methodology including the use of current equipment and anaesthetic regimen for grower pigs. This surgical jugular catheterization method was carried out in 30 large white grower pigs. Firstly, the pigs were habituated to human handling for at least two weeks prior to surgery. Animals were sedated and anesthetized. Following intubation, an incision was made in the jugular fossa, and the jugular vein was located. A catheter was then inserted and fixated. The wound was stapled and the catheter line secured to the back of the neck. The pigs recovered fully from the surgery and the catheters remained patent for the duration of the blood sampling period (min 72 h). Twenty millilitres of blood were collected every 15 min, taking approximately 2 min per pig. No haemolysis was detected in any samples. Jugular catheterization of pigs using this procedure proved successful both in terms of animal recovery and quality of samples. Catheters remained patent and pigs remained calm during sampling.