PSXII-31 Severity of hay processing on dry matter intake, sorting behaviour, and apparent total tract digestibility in lambs

Abstract

Abstract The objective was to evaluate digestibility and sorting behaviour of grass hay processed to differing severities. Thirty-six wether lambs were used in a completely randomized design and fed diets consisting of grass hay (82.2 %), whole barley (15.7 %), and a mineral-vitamin supplement (2.1 %). Treatments included: unprocessed hay (CON); shredded hay (SHRED); chopped hay (CHOP); and ground hay (GRIND). Lambs were fed their respective diet for 20 d followed by 4 d for measurement of feed intake and fecal output. Lambs fed CON (1.23 kg and 3.24 %) had greater DMI (P = 0.04 and 0.05) compared to CHOP (1.04 kg and 2.71 % BW), with SHRED (1.17 kg and 3.11 % BW) and GRIND (1.13 kg and 2.97 % BW) being intermediate. Undigestible NDF intake tended to decrease as processing severity increased (P = 0.05). Dry matter digestibility (67.6, 66.2, 59.6, and 60.8 % for CON, SHRED, CHOP, and GRIND, respectively; P < 0.01) generally decreased as the severity of forage processing increased. Crude protein digestibility was greatest in CON (68.6 %) compared to SHRED (60.83 %), CHOP (58.7 %), and GRIND (58.5 %; P < 0.01). ADF and aNDFom digestibilities were greater for CON (57.4 and 67.2 %) and SHRED (60.0 and 67.9 %) compared to CHOP (44.8 and 54.6 %) and GRIND (48.3 and 58.5 %; P < 0.001). CON and SHRED lambs sorted for larger particle sizes (particles > 19 mm and 8 to 19 mm; P < 0.001 and 0.025, respectively) while CHOP and GRIND lambs sorted for smaller particles (particles 4 to 8 mm and particles < 4 mm; P < 0.001 and 0.003, respectively). These results indicate that processing of grass hay does not increase nutrient digestibility partly because of the sorting behaviour of lambs.