SummaryA microbial cell product was compared with fish meal at three levels of dietary inclusion, using barley as the basal diet. Digestibility coefficients for flash-dried microbial cells (DMC) were calculated to be 0·85 for gross energy and 0·91 for N. Digestible energy (DE) values were 18·8 MJ DE/kg D.M. for DMC and 16·5 MJ DE/kg D.M. for the fish meal. Digestible nitrogen (DN) values were 119 g DN/kg D.M. for the DMC protein and 108 g DN/kg D.M. for the fish meal. The metabolizable energy (ME) values for diets containing DMC were similar to those for diets containing fish meal; ME/DE for diets containing about 16·5% crude protein was 0·96. Microbial N was less efficiently utilized than fish meal N; this was largely attributed to the different contents of nucleic acid N.

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Digestibility trials were undertaken with pigs weighing 45 kg to compare the nutritive value of dried cooked potato with raw ware potato, potato of high and medium glycoalkaloid content, sprouted and greened potato, and macerated potato centrifuged (dewatered) to remove 84% of the water. There was no effect attributable specifically to either glycoalkaloid, sprouting or greening. In relation to values obtained for cooked potato, raw potato treatments had lower apparent digestibility coefficients for nitrogen and a lower efficiency for nitrogen retention. When potato was dewatered, 84% of the nitrogen, but none of the starch, was lost in the effluent. Chymotrypsin inhibitor activity was high in all the raw potato stocks, but absent in cooked potato. It is suggested that the presence of a chyrnotrypsin inhibitor contributed to the deleterious effects on nitrogen utilisation which resulted from the inclusion of raw potato into diets.

The digestibility of nutrients in milk replacers were determined with Ayrshire bull calves from 7 to 28 days of age. The mean apparent digestibilities of dry matter (DM), gross energy (g.e.) and nitrogen declined from 0.84 to 0.79; 0.85 to 0.78 and 0.79 to 0.76 when cooked potato flour replaced an equivalent weight of spray-dried whey in liquid diets. Potato starch has a mean apparent digestibility of 0.65. Nitrogen retention was unaffected by diet, but the potato diet had a lower metabolisable energy value than the control diet (15.6 and 17.5 MJ per kg DM respectively). Glucose levels in the jugular blood were lower for calves fed the potato based milk replacer. The apparent digestibilities of dry matter, gross energy and nitrogen showed marked improvements with age, particularly on the potato based diet, with starch digestibility improving from 0.50 to 0.74 between 10 and 24 days. While blood glucose concentration increases with age, the relative differences between treatments remained.

1. Broiler chicks, reared on litter, were given diets containing either 40% maize, 40% cooked potato flake, or 20% of each, in crumb form ad libitum from 1 to 21 d and 21 to 63 d in five dietary treatments.2. Birds receiving the diet with 40% cooked potato flake grew more slowly than birds receiving the other diets during both periods but their food consumption was the same.3. Including cooked potato flake in diets decreased the dry matter of the litter: with 40% in the diet the litter dry matter was decreased to 26% in 49 d at a stocking rate of 11 birds/m 2 .4. If the litter was kept dry, 20% of cooked potato flake was found to be an acceptable inclusion rate for broiler diets.