PSI-4 - Effects of Sorghum Inclusion in Lamb Diets on Apparent Total Tract Digestibility

Abstract: The objective of this experiment was to evaluate the effect of grain sorghum inclusion on the apparent total tract digestibility of lamb diets. This experiment utilized 24 Rambouillet lambs (46.1 ± 3.90 kg) that were previously used in a growth experiment. Animals were housed in one of 24 pens with 1 lamb per pen and 6 pens per treatment. Lambs were randomly assigned one of the 4 treatment diets prior to the growth experiment and remained on the same treatment for over the 10-d experimental period. Treatments included 1) Control (0% sorghum inclusion); 2) Sorg10 (10% corn substituted for sorghum); 3) Sorg20 (20% corn substituted for sorghum); and 4) Sorg30 (30% corn substituted for corn). Diets were ground using hammermill and titanium dioxide was added to the ground diet at 0.4% as an indigestible marker. Lambs were fed these diets for 7-d prior to fecal sample collection to allow for steady-state marker concentrations. Fecal grab samples were collected every 6 hours over the final 3 days and were composited by animal to represent each 2-hour period of a 24-hour cycle. Feed and composited fecal samples were analyzed for crude fat, crude protein, ADF, NDF, and ash. Data were analyzed using the LM function in R with a fixed effect of treatment. Significance was defined at P £ 0.05 and means were separated using Tukey’s HSD where appropriate. Sorghum inclusion did not affect (P ³ 0.16) crude protein, crude fat, or acid detergent fiber digestibility. Neutral detergent fiber digestibility was reduced (P = 0.02) for animals consuming Sorg20 and Sorg30 compared to the control, and Sorg10 was intermediate. Organic matter digestibility tended to decrease (P = 0.08) with increasing sorghum inclusion. In conclusion, replacing corn with sorghum at levels up to 30% had minimal impact on nutrient digestibility in growing lambs.