J. Anim Sci., doi: 10.2527/jas.2007-0491
©Copyright, 2007, The American Society of Animal Science
Influence of dry rolling and tempering agent addition during the steam-flaking of sorghum grain on the feeding value for feedlot cattle
R. A. Zinn 1*,
E. G. Alverez 1,
M. Montano 1,
J. Salinas-Chavira 1
1 Department of Animal Science, University of California, Davis 95616
* To whom correspondence should be addressed. E-mail: razinn{at}ucdavis.edu.
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Abstract |
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Two experiments were conducted to evaluate the influence of dry rolling (DRS) and tempering agent (TA) addition during the steam-flaking of grain sorghum (SFS) for feedlot cattle. Five dietary treatments were compared: 1) DRS; 2) SFS, no TA; 3) SFS, 0.275 mg/kg TA (SarTemp; SarTec, Anoka, MN); 4) SFS, 1.375 mg/kg TA; and 5) SFS, 2.750 mg/kg TA. Bulk densities of DRS and SFS were 0.48 and 0.36 kg/L, respectively. Diets contained 70.6% grain sorghum (DM basis). One hundred fifty crossbred steers (336 kg) were used in a 115-d finishing experiment to evaluate treatment effects on feedlot performance. Weight gain averaged 1.49 kg/d, and was not affected (P = 0.47) by treatments. The SFS reduced (P < 0.01) DMI (9%) and enhanced (P < 0.01) G:F (13%) and the NEm and NEg value of the diet (9 and 11%, respectively). Use of a tempering agent prior to flaking sorghum did not influence (P > 0.20) cattle growth performance or NEm and NEg value of the diet. Given that the NEm and NEg values of DRS are 2.00 and 1.35 Mcal/kg, respectively (NRC, 1996), the corresponding values for SFS were 2.28 and 1.59 Mcal/kg. Five steers (397 kg) with ruminal and duodenal cannulas were used in a 5 x 5 Latin square design to evaluate treatment effects on digestive function. Ruminal digestion of OM and starch were greater (14 and 16%, respectively; P < 0.01) for SFS versus DRS. Steam flaking sorghum increased (P < 0.01) post-ruminal digestion of OM (11%), N (10%), and starch (25%), and total tract digestion (P < 0.01) of OM (8.3%), N (8.2%), and starch (8.9%). Grain processing did not affect (P > 0.20) ruminal pH or VFA molar proportions. There was a cubic component (P < 0.10) to level of tempering agent on ruminal pH, and VFA molar proportions, with values being optimal at 1.375 mg/kg tempering agent. It is concluded that steam flaking grain sorghum will increase its NE value for maintenance and gain (14 and 18%, respectively) and enhance the MP value of the diet due to greater intestinal N digestion. The use of a tempering agent to enhance the mechanical efficiency of the flaking process may not otherwise benefit the feeding value of sorghum.
Key Words:
sorghum, tempering, steam flake, performance, digestion
