EFFECT OF A SOYBEAN HULL, SOY LECITHIN, SOAPSTOCK MIXTURE ON RUMINAL DIGESTION AND PERFORMANCE OF GROWING BEEF-CALVES AND LACTATING DAIRY-CATTLE

Four experiments were conducted to evaluate the effect of a soybean hu ll, soy lecithin, and soapstock mixture on ruminal fiber and protein d igestion, growth efficiency of beef calves, and lactational performanc e of dairy cattle. An initial mixing experiment determined that a 4:1 ratio (DM basis) of soy lecithin:soapstock could be added to soybean h ulls at 15% (wt/wt, DM basis); this mixture had acceptable mixing and handling characteristics. Dietary addition of a mixture of 85% soybean hulls, 12% soy lecithin, and 3% soapstock (DM basis; SLS) to provide 0, 3, 5, or 7% supplemental fat resulted in a linear (P < .01) decreas e in in situ rate of ruminal NDF digestion with no effect on rate of C P digestion. Daily gain, DMI, and feed efficiency (kilograms of gain/k ilogram of DMI) of growing beef calves were not affected (P > .10) as graded levels of SLS replaced com grain. However, as graded levels of SLS replaced soybean hulls, daily gain and feed efficiency increased l inearly (P < .01). Based on the results of these trials, Holstein dair y cattle were fed four isonitrogenous and isoenergetic diets that cont ained either high levels of nonfiber carbohydrates (43%) and no added fat, 1% ruminally inert fat, a 6% level of SLS, or a 12% SLS level (al l on DM basis). Efficiency of 4% fat-corrected milk production (kilogr ams of milk/kilogram of DMI) was greatest for cows fed SLS at 6% of di etary DM. The SLS mixture was an excellent source of fiber and vegetab le fat, comparable in feeding value to com grain, for inclusion in the diets of beef calves and dairy cows.