Some effects of including differently processed barley in the diet of the growing pig: 1. Growth rate, food conversion efficiency, digestibility and rate of passage through the gut

Propionic acid-treated barley in the diets of bacon pigs

Growth performance and carcass quality (linear measurements) were studied in pigs grown from 25 to 90 kg on barley stored and prepared in different ways. Half the barley was dried to about 14% moisture content for storage and half was not dried but treated with 0·8% propionic acid. Each was given after hammer-milling (3·2 mm screen) or rolling. A total of 144 pigs was used at four centres.

The performance and carcass quality of pigs given acid-treated barley were as good as those given dried barley. While feed utilization, expressed on the basis of air-dry feed, was poorer for pigs fed on acid-treated barley this difference disappeared when account was taken of the different moisture contents of the barley samples. Pigs fed on diets based on milled barley grew more quickly, had better feed utilization but greater fat measurements than pigs fed on rolled barley. There was a significant interaction between storage method and feed preparation (milling or rolling). Pigs given the acid-treated barley grew more quickly when it was in the milled form than when it was rolled, whereas for the dried barley there was a small, non-significant difference in favour of the rolled form.

Moist barley preserved with propionic acid in the diet of the growing pig

The feeding value of three forms of acid-treated moist barley, viz. 26 % moisture and either rolled or plate-milled, and 29 % moisture plate-milled, was compared with that of dried hammer-milled barley for growing pigs from 23 to 87 kg live weight. Two feeding experiments were undertaken, one in which individual pigs were given the same amount of dry matter from all the diets, while in the other, groups of pigs were fed ad libitum. Digestibility of the diet was determined in a third experiment.

In both feeding experiments differences between treatments in efficiency of utilization of dry matter in the feed were significant (P<0·05), that for the diet containing dried barley being approximately 5% better than the other three. There were no significant differences between treatments in intake of dry matter, rate of growth and carcass quality of the pigs. However, pigs fed on dried barley apparently grew more rapidly than those given any of the acid-treated moist barleys. Differences in digestibility of the diets were very small and not significant except for crude protein. Differences in digestibility of protein (P<0·05), however, were not consistent with differences in efficiency of conversion of dry matter in the feed.

Some effects of including differently processed barley in the diet of the growing pig: 2. In vivo gastric pH changes

1. In vivo gastric pH changes were studied, in 6 pigs fitted with permanent gastric cannulae, under ‘basal conditions’ (i.e. when no food was given) and when diets containing 85% of differently processed barley were given either twice daily or at frequent intervals of time in an attempt to simulate ad libitum feeding systems. Before inclusion in the diet the 85% of barley had either received no processing (i.e. was given as the whole grain) or had been processed in one of the five following ways: (a) ground through a (1·56 mm) screen (b) ground through a (4·68 mm) screen (c) ground through a (9·36 mm) screen (d) coarsely crimped (e) cold rolled.

2. Relative to the ‘basal’ determinations the systems of feeding which gave food at frequent intervals of time induced higher overall mean pH values than did those which gave food twice daily, while between the six differently processed diets those containing the smaller particles of barley tended to give higher overall mean pH values than did those containing the coarser particles.

3. The validity of the results is discussed in the context of the techniques used and some possible implications in terms of animal health are briefly discussed.

Nutritional evaluation of wheat. 5. Disappearance of components in digesta of pigs prepared with two re-entrant cannulae

1. Three pigs prepared with re-entrant cannulae in the proximal duodenum and terminal ileum were used to study flow rate of nitrogen, and digestion and absorption of dry matter, nitrogen, gross energy and starch. The pigs were given a semi-purified diet, a hard wheat diet and a soft wheat diet. These were approximately isonitrogenous.

2. Nitrogen content of insoluble dry matter of duodenal digesta was much higher on the semi-purified diet than on the wheat-based diets.

3. Apparent digestibilities of dry matter, energy and nitrogen in the small intestine were in the order semi-purified diet > hard wheat > soft wheat although differences were not statistically significant. Similar results were obtained for total digestibility of these components.

4. Absorption of most amino acids from the small intestine was higher for casein in the semi-purified diet than for wheat protein. Significantly more lysine, arginine, isoleucine and tyrosine were absorbed from hard than from soft wheat.

5. With all diets there was almost complete digestion of starch in the small intestine.

6. There was little digestion of nutrients in the large intestine, and thus digestibilities calculated from faecal analyses showed similar trends to those calculated from analyses of digesta from the terminal ileum. Most values compared favourably with those reported elsewhere for digestibilities of amino acids in wheat.

7. It was concluded that casein was superior to the wheat proteins but that protein of hard wheat was of better quality than that of soft wheat when evaluated by ileal recovery of animo acids, due largely to a greater absorption of lysine.

Nutritional evaluation of wheat 1. Effects of preparation on digestibility of dry matter, energy and nitrogen in pigs

1. A split-plot design was used to study apparent digestibility of dry matter, gross energy and nitrogen of a whole grain wheat diet and processed (hammermilled, rolled or hammermilled and then steam-pelleted) wheat diets by eight small (33·9 ± 0·1 kg) and eight large (70±1·7 kg) pigs. Metabolizable energy and nitrogen retention were also studied with the small pigs.

2. The processed wheat diets were superior to the whole grain wheat diet in all the parameters measured.

3. There were no significant differences between the performance of pigs given the differently processed wheat diets.

4. Apparent digestibility of dietary components particularly in the whole wheat diet was significantly higher when diets were given to small pigs than when given to large pigs.

Growth and gastric abnormalities in the growing pig resulting from diets based on barley in differing physical forms

Seventy-two Large White × (Large White × Landrace) weaner pigs in each of three experiments were scale-fed diets containing 850 g barley per kg which had been processed by either cold rolling (R) or grinding through 1-56 mm (O) or 468 mm (T) screens. In experiments 1 and 2 barley (0-868 dry matter) was used and group feeding was practised for 55 and 100 days respectively. In experiment 3 barley (0-838 dry matter) was used and individual feeding was practised for 107 days. In experiment 1 gastric pH was recorded at slaughter. In all experiments the stomachs of all pigs were examined for gross and histological abnormalities.

In experiments 1 and 2 growth rates and efficiencies of feed conversion were not significantly different for pigs fed the R-, O- and T-based diets. In experiment 1 the pH in the pylorus, but not in the fundus, was significantly higher in pigs fed the O-diet compared with the T-diet, and on the T-diet compared with the R-diet. Growth rates and efficiencies of feed conversion in experiment 3 were significantly poorer in pigs fed the R-diet compared with the T-diet, and on the T-diet compared with the O-diet. In experiment 1 one pig from each of the three diets showed hyperplastic changes in the pars oesophagea of the stomach. In experiment 2 no gastric abnormalities were found, but bile staining was present in the pyloric zone of one pig fed each of the three diets. In experiment 3 hyperplastic lesions of the pars oesophagea (and bile staining) were present in 19 (14), 10 (7) and 4 (1) pigs fed diets O, T and R respectively.

Effects of structural and non-structural polysaccharides in the diet of the growing pig on gastric emptying rate and rate of passage of digesta to the terminal ileum and through the total gastrointestinal tract

Six experiments were made in growing pigs to investigate the effects of substituting bran, oatmeal byproduct, pectin and guar gum for barley on gastric emptying rate, pH and dry matter of digesta and on the dry matter content and rate of passage of digesta to the terminal ileum and overall. Twelve pigs with cannulas sited at the pyloric/fundic junction of the stomach were used to measure gastric emptying. Seventy-two pigs were kept in metabolism cages for the total collection of faeces and nine pigs were fitted with simple cannulas 150 mm cranial to the ileo-caecal junction. For the overall transit measurements the barley was ground through a 4.68 mm screen (C) and for the other studies either through this screen or a 1.56 mm screen (F). Gastric emptying rates were significantly faster for F diets than for C diets, but bran and oatmeal by-product substitutions were without significant effect on this variable or on rate of passage to the terminal ileum. Guar gum and pectin significantly speeded up gastric emptying and transit to the terminal ileum in C diets. Guar gum and pectin did not significantly affect overall transit time, but bran accelerated it. The results are discussed in relation to the depressive effects on nutrient utilization which have been recorded for the four polysaccharides: it is postulated that gastric emptying rate and transit time to the terminal ileum are likely to have a minimal effect on overall transit time.