V a L U E of High Fiber Diets for G R a V I D Swine 1

An experiment was conducted to determine the effect of roughages on the utilization of dietary nitrogen, energy and fiber by gravid swine. Water consumption, backfat depletion, pregnancy weight gain, and reproductive performance were used as response criteria. Metabolism assays, employing 18 crossbred sows (second or third parity), were initiated at days 0 (prior to breeding), 30 and 80 postcoitum. The pelleted experimental diets consisted of a 97% sun-cured alfalfa (Alf), a 66% tall wheatgrass (WG), and a conventional corn-soybean meal diet (CS). The sows were weighed every 2 weeks and changes in backfat thickness were estimated from ultrasonic determinations. Water consumption was not affected by treatment. The average apparent water intake was 17.5 li ters/sow/day with an average spillage of 14.9 liters/day. The CS group gained more weight than those fed high fiber diets during gestation (P<.001), with a tendency for the sows in the CS group to have a greater amount of backfat than those fed the high fiber diets. Metabolizable energy (ME) values were 2,019, 1,874 and 3,733 kcal/kg for Alf, WG and CS diets, respectively. ME value of tall wheatgrass was 597 kcal/kg of dry matter. Sows in the CS group retained more nitrogen (g/day) than those in the Alf and WG groups (P<.001). A period • t reatment interaction (P<.05) was observed for dry matter (DM) digestibility. The sows on the Alf and WG diets showed decreased DM digestibility from day 0 to day 30 and then increased 3.0 and 2.8%, respectively, to day 80 of gestation. Conversely, the CS group showed an increase in DM digestibility slightly above the base at 30 days and then a decrease of 2.7%