Substitution of a Protected Tallow Product for Grain Sorghum in the Diet of Fattening Steers Fed for 89 or 118 Days2

A field trial was conducted with 200 steers of mixed breeding with a mean initial weight of 351 kilograms. The steers were randomly allotted within three breed type groups into control (C) or protected tallow (PT) treatments. The C steers were offered a diet containing 85% concentrates and 15% corn silage on a dry matter basis. The PT steers received the same diet except a formaldehyde-treated protein protected tallow product (containing 40% tallow) was substituted for grain sorghum at 19% of the total dry matter of the diet. At that level, the PT provided 7.65% added tallow to the diet. Within the C group, 20 steers were fed for 89 days and 78 were fed for 118 days. In the PT group, 76 were fed for 89 days and 20 were fed for 118 days. Feeding the PT product increased (P<.08) average daily gain (ADG), however, increasing the time on feed from 89 to 118 days reduced (P<.002) ADG. The feed required per unit of gain was reduced by PT feeding and was increased by extending the length of time on feed.Adjusted subcutaneous fat thickness, percentage of kidney, pelvic and heart fat and USDA yield grade were increased (P<.01) by either feeding the C group 118 days or by including the PT product in the diet for 89 days. Fat content of the longissimusmuscle was increased (P<.04) by inclusion of the PT product in the diet and was also increased (P<.08) by increasing the time on feed. Feeding the PT product for 89 days produced steers with carcass characteristics quite similar to steers fed the control diet for 118 days.Sensory characteristics of cooked longissimussteaks were unaffected (P<.05) by either time on feed or by the PT product. Increasing the time on feed from 89 to 118 days increased shrinkage (P<.07) and cooking time (P<.02), but had no significant effect on the appearance of doneness.