Initial Compartment 1 pH Response to Grain Supplementation in Alpacas (Vicugna pacos) Fed Alfalfa and Grass Hay

The purpose of this study was to determine the diurnal pH variation of the first compartment stomach (C1) of alpacas (vicugna pacos) fed grass hay (GH) or alfalfa hay (AH) and initial addition of grain supplements; oats (O), corn (C) or corn/oats/barley (COB) and to determine the effects of initial inclusion of corn to GH at levels of 0, 35, 50 and 70% of dry matter intake on C1 pH. Two experiments were conducted with four male (+3 yrs, 65 kg BW) alpaca fitted with C1 fistula. Alpaca were housed in metabolism crates and fed ad libitum hay and water. Experiment 1 treatments (TRT) included supplementation of 454 g of oats (O), ground corn (C), corn/oats/barley/molasses (COB) to AH (AO, AC, ACOB) and GH (GO, GC, GCOB). Two alpacas were acclimated to AH and the other two to GH. Each grain TRT was randomly administered followed by a 30 d acclimation period to the other forage and random administration of each grain. A pH probe was fitted through the fistula and positioned at the anterior, ventral portion of C1. Treatment periods included d1 to d7 diurnal pH collection of AH or GH, d8-10, d15-17 and d22-24 for grain TRT. Dry matter intake (DMI) was 1415, 1146, 1142 and 1192g for AH, AC, AO and ACOB; and 1331, 1206, 1207, and 1260 for GH, GC, GO and GCOB. AH was different from AH+grain TRT (P < 0.05). Overall pH was 6.87, 6.78, 6.78 and 6.56 for AH, AC, AO and ACOB; and 6.95, 6.76, 6.89 and 6.83 for GH, GC, GO and GCOB (P < 0.05). TRT and Time were significant (P < 0.05). For EXP 2 GH was supplemented with 0 (G0C), 454g (G1C), 731g (G2C) and 908g (G3C) of corn. DMI was not affected. Overall pH decreased from 7.27 to 7.08 for G0C to G3C (P < 0.05). Diurnal pH was significant for TRT (P < 0.05), but not Time. Initial or abrupt feeding of grains to alpacas does elicit a pH response, but not to the extent of other true ruminants. This may be attributed to the buffering capacity of the C1, but further research is needed.