Effects of sorghum silage kernel processing on intake and apparent total tract digestibility of beef heifers

Author details:

1 University of Florida, North Florida Research and Education Center; 2 Universidad Nacional del Litoral, Santa Fe, Argentina; 3 El Encuentro Experimental Farm; 4 Universidad Nacional de La Plata; 5 Claas; 6 University of Florida.

This study evaluated the effect of different kernel processors in terms of nutrient digestibility of whole-plant sorghum silage. Grain sorghum (hybrid ADV1250IG, Advanta Seeds, Irving, TX) was harvested at the hard-dough stage with a Class Jaguar 960 and 930 harvesters, switching the kernel processor to generate the forage material for the three treatments: conventionally processed (CONV), unprocessed (UN), and shredlage processed (SHRED). The material was bagged in three 2.7 m bags and allowed to ferment for 1 mo. Twenty-four black Angus heifers (13 ± 1 mo, 267 ± 10.9 kg of BW) were randomly assigned to treatments (8 heifers/treatment) and allocated to individual pens (36 m²) with access to feed and water. Diets were ad libitum sorghum silage from each respective treatment, plus soybean meal top-dressed at 0.5% of BW. After a 15-d adaptation period, feed and feces were collected for 5 d. Feed was offered once daily, and orts were collected the following day. Fecal samples were collected twice daily and apparent total tract digestibility was determined using indigestible NDF as a marker. Data were analyzed as a completely randomized design using heifer as the experimental unit, and initial BW as a covariate. Dry matter (DM) intake as a percentage of BW (P = 0.09) and NDF digestibility (P = 0.06) tended to differ among treatments, where CONV tended to be lesser than UN (P = 0.08), whereas SHRED was intermediate. Digestibility of DM was affected by treatment (P = 0.05), where UN (71.3%) tended (P = 0.06) to be greater than CONV (67.9%), while SHRED (70.8%) did not differ from any of the treatments (P ≥ 0.12). In conclusion, kernel processing affects nutrient digestibility of sorghum silage. Differences in ruminal kinetics and fermentation parameters, resulting from contrasting particle sizes, grain processing and sorting, may help explain these findings.

Abstract published in Journal of Animal Science, Volume 98, Issue Supplement_4, November 2020, Pages 153–154, https://doi.org/10.1093/jas/skaa278.280.