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In Vitro and In Vivo Evaluation of Temperature and Pressure-Treated Tallow-Protein Mixtures¹

Oklahoma Agricultural Experiment Station, Stillwater 74078

Abstract

Effects of tallow additions to cottonseed meal and soybean meal (SBM) via heat, pressure and(or) vacuum on ruminal ammonia N (NH₃-N), digestibility and N balance were evaluated. Tallow-protein mixtures were treated in an experimental mixer equipped with a water jacket and steam and vacuum inlets allowing for temperature control. In vitro trials showed that pressure and heat (with live steam) reduced NH₃-N accumulation. Vacuum with dry heat did not affect NH₃-H accumulation. In a metabolism trial, 15 lambs were fed winter-harvested range grass and .07 kg/day of: (1) SBM + 15% tallow (SBM-T); (2) SBM + 15% tallow heated to 121 C, 1.36 atmospheres, for 5 min (HSBM-T), and (3) HSBM-T plus 1% urea (HSBM-T+U). Dry matter digestibility and N retained tended to be reduced with HSBM-T and HSBM-T+U. Ruminal NH₃-N did not differ (P>.05) between treatments. Ruminal NH₃-N was determined in 16 lambs fed a 33% corn, 50% alfalfa diet plus (1) SBM, (2) SBM heated for 5 min at 121 C under 1.36 atmospheres of pressure (HSBM), (3) SBM + 15% tallow (SBM-T) or (4) SBM-T heated in a manner similar to HSBM (HSBM-T). Heating of SBM reduced (P<.05) ruminal NH₃-N at 1, 4 and 8 hr postfeeding when concentrate diets were fed but not when roughage diets were offered. The addition of tallow to SBM reduced (P<.05) ruminal NH₃-N at 8 hr postfeeding when the SBM was fed with a concentrate diet. When 16 lambs were fed SBM, HSBM, SBM-T and HSBM-T with low quality hay, ruminal NH₃-N at 8 hr postfeeding was not reduced (P>.05) as a result of heating and(or) the addition of tallow to SBM, but heating tended to lower ruminal NH₃-N at 4 hr postfeeding. When SBM, HSBM, SBM-T and HSBM-T were incubated in vitro with rumen fluid from fistulated steers fed a roughage or a 40% concentrate diet, heating reduced (P<.05) NH₃-N in both types of inocula. The addition of 15% tallow to SBM appears to reduce ruminal NH₃-N accumulation when the mixture is fed with a concentrate diet but not when it is fed with a roughage diet. Heat treatment of the protein-tallow mixtures tended to reduce ruminal NH₃-N concentration.

¹ Journal Article 3788 of the Agr. Exp. Sta., Oklahoma State Univ., Stillwater 74078.

² Colorado State Univ., Fort Collins 80523.

³ Anim. Sci. Dept.

⁴ Dept. of Agr. Eng.