Dietary lupins (Lupinus angustifolius and Lupinus albus) can increase digesta retention in the gastrointestinal tract of pigs

Lupins are high in crude protein, cell wall materials, and gross energy but uncertainty about the bioavailability of nutrients and adverse effects on feed intake limit their use in the pig industry. Three experiments were conducted to determine the effect of lupins on retention time in the digestive tract by determining the average time it took for ingested polyethylene beads to pass through the digestive tract of pigs fed wheat-based diets containing various lupin species and fractions. In Expt 1, pigs were restrictively fed (1.8 kg/day) diets containing either predominantly wheat or predominantly wheat plus 400 g/kg peas or L. angustifolius seeds or kernels. The retention times of diets containing 400 g/kg of L. angustifolius seeds or kernels were significantly greater than those containing wheat alone (66.4 and 64.3 v. 48.8 h, P > 0.05, s.e.d. = 7.7 h), while that for the diet containing 400 g/ kg peas was intermediate (55.8 h). In Expt 2 and 3, pigs were fed 1 of 6 wheat-based diets balanced for digestible energy (DE) and amino acid composition and containing either animal protein or 350 g/kg of peas, and L. angustifolius seeds or kernels, or L. albus seeds and kernels. Pigs were restrictively fed (1.5 kg/day) for Expt 2 or fed ad libitum for Expt 3. The mean retention time of the L. albus diets was greater than the other diets in both experiments. Feed intake and daily gain were reduced in pigs fed diets containing L. albus. Despite having lower feed intakes, pigs fed diets containing L. albus had more digesta in the stomach and small intestine at slaughter than the pigs consuming the diets not containing lupins. Appropriate physical treatment or enzymatic supplementation of L. albus diets may alleviate some of the feed intake problems