Influence of forage inclusion in the diet on ileal and total tract digestibility

The present investigation aimed to study the ileal and total tract digestibility of 3 forages (clover-grass, clover-grass silage, and field pea (Pisum sativum)-barley (Hordeum vulgare) silage) supplemented to a basal diet. A total of 24 pigs, adapted to eating forages by supplementing a basal feed with clover-grass silage from weaning, were fitted with a T-cannula at the terminal ileum at approximate 30 kg BW. For each of the 3 types of forage, 2 balance trials with a 4 wk interval were carried out. Two pigs in each test were fed the basal diet and 6 others were fed the basal diet plus forage throughout the whole experiment. The intake of forages was low and quite variable and on average accounted for only 10 to 12% of the DMI. Ileal digestibility of protein estimated by collection from the T-cannula was higher (P = 0.031) than the digestibility estimated by the slaughter technique indicating some separation of the digesta collected from the T-cannula. The forages had, as expected, a lower total tract DM and energy digestibility than the basal diet (P < 0.05). The fresh clover-grass had a higher energy digestibility than the 2 silages (60 vs. 48%; P < 0.05). Inclusion of 10% of GE in the diet as forage reduced (P < 0.05) the energy digestibility of the ration by 2.2% for clover-grass, 3.4% for clover-grass silage, and 5.0% for pea-barley silage. In organic slaughter pig production, the overall energy supply from these forages is limited, but they may play an important role in satiety and rooting behavior.