Creature Companion - Interzoo Special September 2019 | Page 42

Pet Nutrition Legislation European legislation designates guar, carob and cassia gums as technological additives in feedingstuff s, falling within the subclass of emulsifying and stabilizing agents, thickeners and gelling agents (6-8). Guar meal, carob and fenugreek seed are listed in the catalogue of feed materials (9). Galactomannans Seed galactomannans (GM) act as energy storage for germination in the endosperm. Th eir β-1,4-linked mannan backbones have single galactose units in α-1,6 linkages. Th e mannose:galactose ratio typifi es gums, but also varies within kinds. Th e ratio is roughly 1 to 5 for GM from fenugreek, guar, tara, carob and cassia seeds. Since galactose imparts hydrophilicity to GM, through inhibiting inter-chain association, water solubility is higher for lower mannose:galactose ratios. To obtain GM-rich gums from seeds, the isolated endosperm is dissolved in water, followed by addition of alcohol as precipitation step. Whole seeds of the fi ve gum sources contain 21-33% GM (10-13). GM contents are insignifi cant in cereal grains (14) and at most 1% for the endospermic legumes, chickpeas, lentils, green beans and soybeans (15, 16). Fermentation Pancreatic α-amylase cannot hydrolyse GM, implying indigestibility in dogs and cats. Ingested GM is broken down in the colon. Guar and carob gums are fermented by dog and cat fecal microfl ora, the rates diff ering considerably between preparations of the same gum type (17-19). In keeping with reduced ileal protein digestion, guar gum intake by dogs reduced postprandial concentrations of α-amino nitrogen and urea (22). Postprandial plasma glucose in dogs was lowered when guar gum was consumed with a single meal (25, 27), but not aft er daily feeding (22). Guar gum reduced blood cholesterol in dogs (22). Guar gum Guar gum intakes by dogs (20) and cats (21) at levels as high as 7.0 and 4.0% of dietary dry matter (ddm), reduced apparent protein digestibility by 5.3 and 8.1% units, increased feces production by 80 and 25% and water content by 11 and 1% units. Four diet comparisons in dogs (22, 23) indicate that guar gum at 3.1% ddm lowered total-tract digestibilities of dry matter and protein by 0.8 and 2.5% units. In cats fed guar gum at 2.3% ddm, feces production was increased by 9%, while organic matter and protein digestion were decreased by 0.3 and 3.4% units (24). Th us, adding 0.5% guar gum to wet food (2.5% ddm) clearly reduces apparent protein digestion. Feeding guar gum to dogs accelerated gastric emptying of larger food particles (25) and increased viscosity of ileal digesta (26). Th ose eff ects shorten the digestive action of gastric pepsin and impede that of pancreatic proteases. Guar gum likely stimulates fecal excretion of bacterial nitrogen, which by itself lowers apparent protein digestion. Fenugreek seed Defatted fenugreek seed at 12% ddm lowered plasma cholesterol in normal dogs and reduced cholesterol, blood and urinary glucose in alloxan-diabetic dogs. A gum- rich fraction from defatted seed had both hypocholesterolemic and hypoglycemic activity, whereas a saponin-rich fraction reduced only cholesterol (28-33). Safety of seed gums Guar gum at 0.5% in commercial wet foods depresses protein digestion without endangering protein supply as those foods provide ample protein. Th e guar gum and extra undigested protein entering the colon stimulate bacterial growth, leading to an increase in fecal nitrogen by about 20%. Th e increased bacterial activity, including enhanced protein fermentation, does not demonstrably impair gut health. Dog feeding trials, lasting 12-30 weeks, indicate that 0.5% seed gum in wet food is safe, when it comes to guar, carob, cassia and tara gum (34-38). * List of references is available on request from the author ([email protected])