COMPARATIVE DIGESTIVE UTILIZATION OF UHT GOATS AND COWS MILKS - NUTRITIONAL EFFECTS OF GELATION - USE OF A SWINE MODEL

The digestive utilization of the nutrients from goat's and cow's milk was studied using the growing pig as a model. The digestibility of the main nutrients (energy, crude protein, alimentary fibre) was measured at the fecal level, and that of the amino acids and fatty acids, was determined at the ileal level, using an equal supply of crude protein and crude fat with both milks. In addition, the nutritional impact of goat's milk gelation was studied in ileal digestibility. In both exper iments, the animals were fed fortified barley with goat's or cow's mil k (25% of total dry matter in the diet). Total digestibility was measu red over a 10-d period in 2 groups of 5 barrows (35 kg liveweight) fed the 2 diets. In another group of 6 pigs, a surgically-modified ileo-r ectal anastomosis allowed measurement of ileal digestibility over at l east 5 or 7-d periods per treatment With the animals used for the tota l digestibility, both the milks led to the same performance. These res ults are consistent with the fact that the total digestive utilization of the main nutrients was not significantly different between the mil ks. Only the minerals tended to be better absorbed from the goat's mil k than from the cow's milk. This was also the case for ileal digestibi lity. At this level, the differences were significant: the true (conve ntional) digestibility of cystine (-16.7 points), methionine (-6.1 poi nts) and isoleucine (-6.3 points) was lower in goat's milk; but that o f lysine did not differ between the 2 milks, ie 93.2 and 94.6% for the goat's and cow's milks respectively. The middle-chain fatty acids wer e completely digested in the small intestine. Although the differences between the 2 milks were not significant, the goat's milk fatty acids tended, on average, to be slightly better absorbed than the cow's mil k fatty acids, especially as regards C14:0 and C18:2. The main consequ ence of gelation was an inhibition of the absorption of lactose and mi nerals and a reduction in alimentary fibre degradation, leading to a d ecrease in milk and diet energy content. Gelation led to an additional decrease in cystine and arginine digestibility. Finally, gelation had little effect on fats, with the exception of linoleic acid whose dige stibility was reduced. In conclusion it can be inferred from this swin e model that the gross nutritive value of UHT liquid goat's milk is no t significantly different from that of UHT cow's milk for growth after weaning.