Story in Brief. Introduction. Experimental Procedures

Transcription

1 Chemical, Fatty Acid, and Tenderness Characteristics of Beef from Three Biological Types of Cattle Grazing Cool-Season Forages Supplemented with Soyhulls R.T. Baulits 1, A.H. Brown, Jr. 1, F.W. Pohlman 1, Z.B. Johnson 1, D.O. Onks 2, and B.A. Sandelin 1 Story in Brief Over two consecutive years, the effects of allocating large-, medium-, or small-framed cattle, all of intermediate rate of maturing (n = 107), to fescue without supplementation (Control), or fescue or orchardgrass pasture with soyhull supplementation on shear, chemical, and fatty acid characteristics were investigated. There were no differences (P > 0.05) in shear force etween dietary treatments. Cattle from the two supplemented treatments produced eef that had increased (P < 0.05) percentage lipid and decreased (P < 0.05) proportions of polyunsaturated (PUFA) and n-3 fatty acids (those fatty acids with the first doule ond at the third caron from the caronyl end of the fatty acid) compared to the Control. However, supplementation did not decrease proportions of conjugated linoleic acid (CLA) present in the longissimus, which can commonly occur when forage-fed cattle are supplemented concentrates. Additionally, even though the proportion of n-3 fatty acids was reduced with supplementation, the n-6/n-3 ratio (n-6 fatty acids are those unsaturated fatty acids with the first doule ond at the sixth caron from the caronyl end of the fatty acid molecule) was elow five in all three treatments, which could potentially aid in reduced atherosclerosis and inflammation. Biological type did not appear to e a significant source of variation for most traits analyzed in this study. These results suggest that supplementation of soyhulls to cattle grazing forage may not decrease CLA proportions, and although it might elicit a reduction in proportions of PUFA and n-3 fatty acids present in the longissimus, the n-6/n-3 ratio still may e maintained elow the recommended ratio of four to five. Introduction Experimental Procedures A forage-ased feeding regimen offers an alternative marketing approach for producers. Furthermore, forage-ased eef often exhiits fatty acid profiles that offer positive health characteristics; thus, providing a healthier eef product to consumers. Typically, forage-fed eef contains higher proportions of conjugated linoleic acid (CLA), which exhiits anticarcinogenic properties, and can reduce ody fat. Furthermore, forage-fed eef can exhiit a reduced n-6 /n- 3 fatty acid ratio (n-6 fatty acids are those unsaturated fatty acids with the first doule ond at the sixth caron from the caronyl end of the fatty acid molecule; n-3 fatty acids are those fatty acids with the first doule ond at the third caron from the caronyl end of the fatty acid), which has een shown to exhiit positive health effects. These positive health effects, related to anti-atherogenicity and antiinflammatory processes, have een associated with an n-6/n-3 ratio of five or less (Innis, 1996; Lee et al., 1989). However, forage-fed eef can experience decreased flavor acceptance due to volatiles from fat oxidation and from chlorophyll derivatives (Grieenow et al., 1997). Additionally, forage-fed cattle often are inferior to grainfed cattle, in terms of carcass merit. Supplementation to cattle on forage-ased rations can improve flavor acceptance and carcass merit; however, inclusion of grain in the diet can negatively impact the fatty acid profile of forage-fed eef. Furthermore, the rate of growth exhiited y cattle has een stated to influence tenderness (Aerle et al., 1981) and allotting appropriate types of cattle to a forage-ased system could impact the palataility of the eef. Therefore, the ojective of this study was to oserve the effects of supplementing soyhulls, a highly digestile fier source, to divergent iological types of forage-fed cattle on shear, chemical and fatty acid characteristics. Animals. British, and British x Continental fall- and winter-orn eef steers and heifers from two consecutive years (n = 108) of small (n = 35; SI), medium (n = 36; MI), or large (n = 36; LI) frame size and intermediate maturing rate were selected from a commercial cow herd at the University of Tennessee Experiment Station, Springhill, Tennessee to e utilized in this study. Biological types were estimated using the equation set forth y McCurley et al. (1980). This study was replicated over two consecutive years with 54 animals utilized each year. One small-framed intermediate maturing heifer was removed from the first year s study due to chronic illness. The randomly chosen calves were stratified across either orchardgrass (Dactylis glomerata) predominated pasture supplemented with pelleted soyhulls (Orchard), tall fescue (Festuca arundinacea Schre.) pasture with soyhull supplementation (Fescue), or fescue pasture with no supplementation, for the control (Control). A commercial salt and mineral mix was availale to all animals throughout the study. Six animals (two from each iological type) were allocated to a paddock, replicated three times within each treatment, each year (n = 36 per treatment). There were equal numers of steers and heifers represented within each iological type, within each treatment. Utilizing a rotational system, each paddock allowed for 0.5 acre/calf in the fall and spring, and 1.0 acre/calf in the winter. Pelleted soyhulls were fed to the supplemented treatments and were allocated at 1% BW/calf/day. Adjustments to supplementation were performed every 28 d when the cattle were reweighed. Grazing continued into the summer months (mean days-of-age = 555), until forage availaility started to diminish, whereupon all cattle, within a year, were sent to a commercial slaughtering facility (carcass results reported in Baulits et al., 2003). After carcasses chilled for 48 h, a 1 Department of Animal Science, Fayetteville 2 University of Tennessee Experiment Station, Springhill 139

2 AAES Research Series 522 three-ri section (10 th 12 th ris) of the wholesale ri from the right side of each carcass was removed, vacuum-sealed, transported ack to the University of Arkansas and aged for an additional 5 d efore susequent analyses. Warner-Bratzler shear force. For Warner-Bratzler shear force (WBS) analysis, longissimus steaks (1 in thick) were cooked in a convection oven until the internal temperature of each steak was 158 F. After cooking, steaks were allowed to cool to room temperature for approximately 2 h. Upon cooling, five 0.5 in-diameter cores were removed from each steak for WBS. Each core was sheared with a Warner-Bratzler attachment using an Instron (Canton, Mass.) Universal Testing Machine. Cooking loss. Cooking loss of the steaks was determined during the cooking process for WBS. After steaks were removed from the vacuum-sealed pouches, each steak was weighed on a alance prior to cooking. Upon completion of cooking, a final weight was otained for cooking loss calculations. Moisture percentage. Percent moisture was otained y dicing the longissimus muscle of a steak and utilizing approximately a 50 g sample to represent a homogenous portion. Samples were freezedried for approximately 96 h. After drying moisture percentage was calculated and samples were placed in a commercial lender, ground and stored in a freezer at - 10 F for later determination of total lipids and fatty acid profiles. Total lipids. Total lipids were otained using the method as descried y Rule (1997). Tissue samples weighing 200 mg were utilized and lipid extraction was performed with chloroformmethanol, followed y chloroform removal and evaporation to yield the lipid fraction. Fatty acid profiles. For fatty acid analysis, total lipids were extracted y the same method previously descried. Fatty acid methyl esters (FAME) were prepared y transmethylation utilizing methanol and HCl as descried y Murrieta et al. (2003). Tridecanoic acid (13:0; 1 mg) was used as the internal standard for all samples. Fatty acid methyl esters were analyzed using a Hewlett- Packard 5890 gas chromatograph (Hewlett-Packard, Avondale, Pa.) equipped with a flame ionization detector and a 60 -m x mm fused silica capillary column (SP-2380; Supelco, Bellefonte, PA). Statistical analysis. The experiment was set up as a split-plot design with random effects of year and replicate within year, and fixed effects of treatment and iological type. The whole plot consisted of forage treatment and the su-plot consisted of iological type. The three-way interaction of year x replicate x treatment was the error term for the whole plot, and the four-way interaction year x replicate x treatment x iological type was the error term for the su-plot and for the interaction of treatment x iological type. Although year is generally considered to have a significant effect on performance, it is likely due to temporary environmental effects causing pasture conditions to vary etween years (Vallentine, 1990). Due to this, and that year was considered a random effect, no interactions pertaining to year were included in the final model. Days-ofage of individual animals was included in the final model as a covariate for all variales analyzed. The treatment x iological type interaction was not significant for any traits in this study; therefore, the interaction was pooled into the error term and susequent main effect means are reported. Data were analyzed using the MIXED procedure of SAS (SAS Inst., Inc., Cary, N.C.). Means were generated using LSMEANS and separation was performed using the PDIFF option. Results and Discussion There were no differences (P > 0.05) among treatments for longissimus cooking loss or WBS (Tale 1). Longissimus percentage lipid was greater (P < 0.05) for the supplemented treatments than the Control, and the Control had greater (P < 0.05) percentage moisture than oth supplemented groups (Tale 1). Biological type effects revealed no differences (P > 0.05) in tenderness, or percentage lipid or moisture (Tale 1), indicating that under these dietary conditions, iological type had little influence on the aforementioned traits. Fatty acid profiles of longissimus tissue, y iological type and treatment, are presented in Tale 2 and Tale 3, respectively. Other than the SI cattle having lower (P < 0.05) proportions of 16:1cis-9 and 18:2cis-9, trans-11 (conjugated linoleic acid; CLA), there were no differences among iological types for fatty acid profiles. Longissimus muscle samples from the Control had lower (P < 0.05) proportions of 16:0 and 18:1cis-9, and higher (P < 0.05) proportions of 18:3cis-9,12,15, 20:4cis- 5,8,11,14, 20:5cis-5,8,11,14,17, 22:5cis-7,10,13,16,19 and 22:6cis-4,7,10,13,16,19 than those from Fescue or Orchard (Tale 3). There were no differences etween dietary treatments for CLA (18:2cis-9, trans-11), indicating that soyhull supplementation did not decrease CLA, which commonly occurs with concentrate supplementation to forage-fed cattle. Although there were no differences (P > 0.05) among treatments for saturated fatty acids (SFA), the Control had greater (P < 0.05) proportions of polyunsaturated fatty acids (PUFA) and a greater (P < 0.05) PUFA / SFA ratio than Fescue and Orchard, with Fescue having lower (P < 0.05) proportions of PUFA and a lesser (P < 0.05) PUFA / SFA than Orchard. The Control samples exhiited an improved n-6/n-3 fatty acid ratio, which was less (P < 0.05) than Fescue or Orchard. The increased proportions of PUFA and improved n-6/n-3 ratio exhiited y the Control samples could have een largely due to increased forage ingestion. Forages typically have large amounts of 18:2cis-9,12 and 18:3cis-9,12,15 present in the form of glycolipids. Additionally, these two fatty acids serve as precursors for the endogenous synthesis of many of the 20- and 22- caron polyunsaturates (Innis, 1996). Thus, the Control could have otained higher proportions of longissimus 18:2cis-9,12 and 18:3cis-9,12,15 through increased forage digestion with the exclusion of soyhull supplementation that the Fescue and Orchard treatments received. This could have potentially allowed for direct increased PUFA asorption and increased sustrate for synthesis of the 20- and 22-caron polyunsaturates as well. Although longissimus samples from the control cattle had greater proportions of PUFA and an improved n-6/n-3 fatty acid ratio, the ratios for steaks from the supplemented treatments were elow the recommended ratio five, and there were no differences (P > 0.05) etween treatments for CLA. Implications Supplementing forage-fed cattle soyhulls does not seem to influence shear force. Biological type does not seem to have a large influence on shear force, or composition or fatty acid characteristics under these dietary regimens as well. Decreased longissimus polyunsaturated and n-3 fatty acids occurred as a result of supplementing soyhulls. However, the n-6/n-3 ratio was acceptale and the CLA proportions were not decreased, which can typically result from supplementing concentrates to forage-fed cattle; thus indicating soyhull 140

3 Arkansas Animal Science Department Report 2004 supplementation might e an effective approach to maintain some of the positive fatty acid characteristics associated with forage-fed cattle. Literature Cited Aerle, E. D., et al J. Anim. Sci. 52:757. Baulits, R. T., et al Ark. Anim. Sci. 509:9. Grieenow, R. L., et al J. Prod. Agric. 10:84. Innis, S. M Inter. Life Sci. Inst. Press, Washington, DC. Lee, J. H., et al J. Nutr. 119:1893. McCurley, J. R., et al J. Anim. Sci. 51(Suppl. 1):30. Murrieta, C. M., et al Meat Sci. 65:523. Rule, D. C Meat Sci. 46:23. Vallentine, J. F Grazing Management. Academic Press, Inc. New York. Tale 1. Least squares means for longissimus cooking loss, lipid percentage, moisture percentage and Warner-Bratzler shear force y treatment and iological type (n = 107). Treatment a Biological type Item Control Fescue Orchard LI MI SI Cooking loss c ± ± ± ± ± ± 0.90 Lipid % d 2.55 ± 0.28 x 4.72 ± 0.28 w 5.02 ± 0.28 w 4.04 ± ± ± 0.29 Moisture % e ± 0.27 w ± 0.26 x ± 0.27 x ± ± ± 0.28 Shear, l ± ± ± ± ± ± 0.23 a Control = fescue pasture with no supplementation; Fescue = fescue pasture with 1 % BW soyhull supplementation; Orchard = orchardgrass pasture with 1 % BW soyhull supplementation. d e wx LI = large-framed, intermediate-maturing; MI = medium-framed, intermediate-maturing; SI = small-framed, intermediate-maturing. c Cooking loss expressed as percent; calculated as: (Fresh weight Cooked weight) / Fresh weight x 100. Lipid percentage calculated as: Lipid weight / Tissue weight x (100 percent moisture). Moisture percentage calculated as: (Wet weight Dry weight) / Wet weight x 100. Within treatment or iological type, within a row, means without a common superscript letter differ (P < 0.05). 141

4 AAES Research Series 522 Tale 2. Least squares means for individual fatty acids of longissimus muscle y iological type (n = 107). Biological type a Fatty acid LI MI SI 12: ± ± ± : ± ± ± :1cis ± ± ± : ± ± ± :1cis ± ± ± : ± ± ± :1cis ± 0.09 w 3.03 ± 0.09 w 2.76 ± 0.09 x 16:1trans ± ± ± : ± ± ± :1cis ± ± ± : ± ± ± :1 c ± ± ± :2cis-9, ± ± ± :2cis-9, trans-11 (CLA) 0.70 ± 0.02 w 0.70 ± 0.02 w 0.62 ± 0.02 x 18:3cis-6,9, ± ± ± :3cis-9,12, ± ± ± :4cis-5,8,11, ± ± ± :5cis-5,8,11,14, ± ± ± : ± ± ± :5cis-7,10,13,16, ± ± ± :6cis-4,7,10,13,16, ± ± ± 0.01 PUFA ± ± ± 0.49 SFA ± ± ± 0.36 PUFA /SFA 0.29 ± ± ± 0.01 n ± ± ± 0.15 n ± ± ± 0.41 n-6 / n ± ± ± 0.13 a LI = large framed, intermediate maturing; MI = medium framed, medium intermediate; SI = small framed, intermediate maturing. Fatty acid percents expressed as proportion of all peaks oserved y GLC PUFA = Fatty acids with 2 or more doule onds; SFA = Fatty acids with no doule onds; n-3 = 18:3cis- 9,12,15; 20:5cis-5,8,11,14,17; 22:5cis-7,10,13,16,19; 22:6cis-4,7,10,13,16,19; n-6 = 18:2cis-9,12, 18:3cis-6,9,12, 20:4cis-5,8,11,14. c Includes all cis- and trans- isomers. wx Within treatment or iological type, within a row, means without a common superscript letter differ (P < 0.05). 142

5 Arkansas Animal Science Department Report 2004 Tale 3. Least squares means for individual fatty acids of longissimus muscle y treatment (n = 107). Treatment a Fatty acid Control Fescue Orchard 12: ± ± ± : ± ± ± :1cis ± ± ± : ± 0.24 w 1.44 ± 0.24 x 1.84 ± 0.24 x 15:1cis ± 0.02 w 0.18 ± 0.02 x 0.28 ± 0.02 w 16: ± 0.38 x ± 0.38 w ± 0.38 w 16:1cis ± 0.09 x 3.13 ± 0.09 w 2.96 ± 0.09 wx 16:1trans ± 0.05 w 0.68 ± 0.04 x 0.71 ± 0.05 x 17: ± 0.16 wx 1.52 ± 0.15 x 2.11 ± 0.16 w 17:1cis ± 0.03 w 0.92 ± 0.03 wx 0.84 ± 0.03 x 18: ± ± ± :1 c ± 0.56 x ± 0.56 w ± 0.57 w 18:2cis-9, ± ± ± :2cis-9, trans-11 (CLA) 0.69 ± ± ± :3cis-6,9, ± ± ± :3cis-9,12, ± 0.09 w 1.28 ± 0.09 x 1.18 ± 0.09 x 20:4cis-5,8,11, ± 0.15 w 2.54 ± 0.15 x 2.61 ± 0.15 x 20:5cis-5,8,11,14, ± 0.04 w 0.38 ± 0.04 x 0.51 ± 0.04 x 22: ± ± ± :5cis-7,10,13,16, ± 0.06 w 0.80 ± 0.06 x 1.02 ± 0.06 y 22:6cis-4,7,10,13,16, ± 0.01 w 0.08 ± 0.01 x 0.09 ± 0.01 x PUFA ± 0.48 w ± 0.48 x ± 0.48 y SFA ± ± ± 0.36 PUFA /SFA 0.35 ± 0.01 w 0.23 ± 0.01 x 0.30 ± 0.01 y n ± 0.14 w 2.21 ± 0.14 x 2.84 ± 0.14 y n ± 0.40 w 7.03 ± 0.40 x 9.43 ± 0.41 w n-6 / n ± 0.13 x 3.19 ± 0.13 w 3.36 ± 0.13 w a Control = fescue pasture with no supplementation; Fescue = fescue pasture with 1 % BW soyhull supplementation; Orchard = orchardgrass pasture with 1 % BW soyhull supplementation. Fatty acid percents expressed as proportion of all peaks oserved y GLC PUFA = Fatty acids with 2 or more doule onds; SFA = Fatty acids with no doule onds; n-3 = 18:3cis- 9,12,15; 20:5cis-5,8,11,14,17; 22:5cis-7,10,13,16,19; 22:6cis-4,7,10,13,16,19 n-6 = 18:2cis-9,12, 18:3cis-6,9,12, 20:4cis-5,8,11,14. c Includes all cis- and trans- isomers. wxy Within treatment or iological type, within a row, means without a common superscript letter differ (P < 0.05). 143