The present study gives an overview on the whole mechanism of phytate degradation in the gut and the enzymes involved. Based on the similarity of the human and pigs gut, the study was carried out in pigs as model for humans. To differentiate between intrinsic feed phytases and endogenous phytases hydrolysing phytate in the gut, two diets, one high (control diet) and the other one very low in intrinsic feed phytases (phytase inactivated diet) were applied. In the chyme of stomach, small intestine and colon inositol phosphate isomers and activities of phytases and alkaline phosphatases were determined. In parallel total tract phytate degradation and apparent phosphorus digestibility were assessed. In the stomach chyme of pigs fed the control diet, comparable high phytase activity and strong phytate degradation were observed. The predominant phytate hydrolysis products were inositol phosphates, typically formed by plant phytases. For the phytase inactivated diet, comparable very low phytase activity and almost no phytate degradation in the stomach were determined. In the small intestine and colon, high activity of alkaline phosphatases and low activity of phytases were observed, irrespective of the diet fed. In the colon, stronger phytate degradation for the phytase inactivated diet than for the control diet was detected. Phytate degradation throughout the whole gut was nearly complete and very similar for both diets while the apparent availability of total phosphorus was significantly higher for the pigs fed the control diet than the phytase inactivated diet. The pathway of inositol phosphate hydrolysis in the gut has been elucidated.
The apparent digestibility of nitrogen and amino acids was measured by the ileal and faecal methods in pigs fed nine barleys differing in nitrogen content (from 1.73 to 2.16 per cent/DM). A positive (r = 0.87) and significant relationship was found between the apparent nitrogen digestibility at the end of the ileum and the crude protein content of barley. Generally, the higher the protein of the grain, the higher the ileal digestibilities of the amino acids. For most amino acids the faecal values were greater than the ileal ones. This being specially so for threonine, tryptophan, histidine and cystine belonging to the nutritionally important amino acid group. When the relationship between the amino acid and nitrogen digestibilities at the level of ileum is considered, the values were found to be similar to that of nitrogen in the case of tryptophan, higher for isoleucine, valine (both 2-3 units), cystine, histidine, leucine, methionine (all 5-6 units) and phenylalanine (10 units) and lower only for lysine and threonine (7-8 dig. units).
The aim of the feeding trial was to compare the effects of four different dietary fat supplementations (2.5% of tallow, olive oil, soyabean oil or linseed oil), three sire breeds and both sexes upon pig growth and usual carcass traits, but especially upon several meat and fat quality traits. Ninety-six weaners from different German and foreign sire breeds were tested for their ability to improve the quality of market products. The experiment was carried out with 48 barrows and 48 female growing/fattening pigs. They were progeny of German hybrid sows mated to Duroc, Hampshire × Duroc crosses or Pietrain × Hampshire crosses. The animals were individually kept from 30 to 120 kg liveweight.Growth and slaughter performances of pigs were not signifi cantly infl uenced by the supplemented fat source. The overall mean of intramuscular fat of loin reached only 1.3%, varying between the sire breeds. The fatty-acid composition of backfat and intramuscular fat showed much smaller differences between sire breeds and sexes than between fat supplements to the diets. There were strong correlations between intake (x) and concentration of polyunsaturated fatty acids in backfat (y = 3.73 x -0.91; r 2 = 0.85). Similar correlations were calculated for oleic acid. The results demonstrate that the fatty-acid profi le in backfat and muscle can be substantially infl uenced by fat sources in the diet.
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