In Vitro Digestibility and Preference by Sheep for Silages Made from Whole-Plant Soybeans

Abstract

Maturity group IV (‘Stafford’) vs group V (‘Bay’) soybean forages were harvested and ensiled at either full bloom (R2), full pod (R4), or full seed (R6) growth stages, with or without a silage inoculant and offered to sheep in a consumption experiment having a balanced incomplete block design. Silage samples were collected at the time of feeding for in vitro total DM digestibility determination. Three sheep were adapted to ensiled R6 Bay silage, then individually offered a selection of four different silages (soybean silage combinations or com silage) daily for 13 d. Quantity of each silage was limited to 50% of the total daily silage consumption. In 1988, the indigestible fraction was higher and digestibility at 18, 24, and 72h was lower from R4 Stafford than from the other cultivar and growth stage combinations (P<.05). In 1989, the indigestible fraction was lower and digestibility higher at 24, 48, and 72h from R2 than R4 and R6 silages (P<.05). Com silage was preferred (P<.05) to any of the soybean silages. Consumption of R6 silage was greater (Ρ<·05) than that 0fR2 and R4 in 1988 and 0fR4 in 1989·Silage consumption was conelated positively (P<.05) with forage DM content; DM yield; molar percentage of isovaleric and valeric acids; and lactic acid, ethanol, and acid-detergent lignin contents and negatively with acetic, propionic, isobutyric, butyric, and total volatile fatty acid concentrations; molar percentage of propionic and isobutyric acids; pH; and N, Ca, and P contents. Delaying ensiling of whole-plant soybeans until the R6 growth stage some-what compromises digestibility of the forage but provides a silage of higher acceptance by sheep.