Effects of feed physical form and buffering solutes on water disappearanceand proximal stomach pH in swine

The effects of the physical form of feed on water disappearance and the eff ects of buffered water on proximal stomach pH in swine were determined in t wo experiments. In Exp. 1, 32 barrows were used to evaluate the water disap pearance in pigs fed a finely ground and pelleted diet vs those fed a coars ely ground and mashed diet for ad libitum consumption over a 2-wk interval. There were four replicates with eight pigs per replicate. Average daily wa ter and feed disappearance did not differ (P = 0.06 and P = 0.10, respectiv ely). However, average daily water to feed ratio was higher for pigs on the pelleted diet (4.21 +/- 0,31 L/kg vs 3.04 +/- 0.33 L/kg; P = 0.02). The hi gher ratio for the pelleted diet indicated that this may be the cause of a more fluid digesta allowing reflux of irritants from the distal stomach to damage the pars esophageal region of the proximal stomach. In Exp. 2, four barrows (25 +/- 2 kg) had gastric cannulas surgically implanted into the pr oximal region of the stomach. Pigs were given ad libitum access to a finely ground and pelleted diet. The experimental design was a Latin square. Wate r treatments included water (control), 200 mOsm NaHCO3, 250 mOsm NaHCO3, an d 250 mOsm mono-dibasic sodium phosphate. Pigs were given a 4-d adjustment period, and pH measurements began on the morning of the 5th d and continued for 24 h under normal feeding conditions. Feed was removed and measurement s were continued for 16 h. Buffered water raised the pH of the proximal reg ion of the stomach compared to the control (P < 0.001). Average pR while co nsuming the water treatments was 3.65 +/- 0.11 (n = 4) for water control, 4 .86 +/- 0.11 (n = 4) for the 200 mOsm NaHCO3, 4.63 +/- 0.11 (n = 4) for the 250 mOsm NaHCO3, and 4.59 +/- 0.14 (n = 3) for the 250 mOsm mono-dibasic s odium phosphate. Buffers also raised the pH of the proximal region of the s tomach for the fed (P < 0.001) and the feed restriction (P < 0.01) phases o f the trial. Water disappearance rates in pigs given NaHCO3 were higher tha n in the control (P < 0.01). Average daily water disappearance for the trea tments was 9.13 +/- 0.74 L for the control, 13.56 +/- 0.74 L for 200 mOsm N aHCO3, 13.77 +/- 0.74 L for the 250 mOsm NaHCO3, and 10.33 +/- 0.95 L for t he phosphate buffer. The proximal pH of the stomach was increased by adding buffers to the water supply. Addition of NaHCO3 buffers also caused increa sed water disappearance.