Effect of Dietary Sulfur on in Vitro True Digestibility of Various Feedstuffs

The effect of dietary sulfur on digestibility of feedstuffs is not well defined. The primary objective of this study was to evaluate the effect of dietary sulfur on in vitro true digestibility (IVTD) of various feedstuffs. A secondary objective was to determine the effect of sulfur treated rumen fluid on IVTD of various feedstuffs. Treatments consisted of 0 (CON) or 0.3 (SUL) % sulfur mixed into the ration of eight dorper wethers (29.87 ± 0.52 kg BW) consuming a commercial growing ration (Purina® Honor Show Chow Show lamb Grower 15% DX Medicated feed) with chopped coastal hay mixed at 90%:10%. Wethers were individually housed for the duration of the 56 d trial. Feedstuffs were selected to represent a variety in nutrient quality and included four roughages (wheat straw, blustem hay, coastal hay, alfalfa hay) and three commercial feedlot rations (starter, intermediate, and finisher diets). Ground feedstuff samples containing CON or SUL treatments were weighed into F57 nylon filter bags in quadruplicate. Sheep were slaughtered 56 d after commencing sulfur inclusion. Gastrointestinal tracts were collected during slaughter to allow for rumen fluid collection. Rumen fluid was processed and IVTD protocol performed in accordance with ANKOM (2005) utilizing an ANKOM Daisy^II Incubator. Data were analyzed using the MIXED procedure of SAS 9.3 (SAS Inst. Inc., Cary, NC). An interaction between treatment and feedstuff was not observed (P ≥ 0.64). A main effect of treatment was not observed (P ≥ 0.22). A main effect of feedstuff was observed (P < 0.01) with starter feedlot ration having the greatest IVTD and wheat straw having the lowest. Results suggest that dietary sulfur does not impact IVTD of feedstuffs, but great diversity exists amongst different types of diets.