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ANIMAL NUTRITION |
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* Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-1600; and
and
ADM Corn Processing, Columbus, NE 68601
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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0.08) interactions were detected. Fat addition, regardless of source, decreased (P < 0.01) DMI, marbling score, and the number of carcasses grading USDA Choice. Among heifers fed finishing diets containing TALLOW or 10% GERM, supplemental fat source did not affect DMI (P = 0.76), ADG (P = 0.54), G:F (P = 0.62), or carcass characteristics (P 0.06). Increasing GERM decreased DMI (linear; P < 0.01) and ADG (quadratic; P < 0.02), with ADG by heifers fed 10% GERM slightly greater than those fed control but least for heifers fed 15% GERM. Increasing GERM improved (quadratic; P < 0.03) G:F of heifers, with heifers fed 10% GERM having the greatest G:F. Increasing GERM decreased HCW (linear; P < 0.02), marbling score (linear; P < 0.01), and the percentage of carcasses grading USDA Choice (linear; P < 0.01). The addition of vitamin E increased (P < 0.04) the percentage of carcasses grading USDA Select and decreased (P < 0.01) the percentage of carcasses grading USDA Standard. These data suggest that GERM can serve as a supplemental fat source in cattle finishing diets, and that the effect of vitamin E did not depend on source or concentration of supplemental fat.
Key Words: Cattle • Dried Full-Fat Corn Germ • Fat • Vitamin E
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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; Zinn and Shen, 1996; Ramirez and Zinn, 2000). Common fat sources fed to cattle are tallow, vegetable fat, or tallow and vegetable fat blends. Because supplemental fat is typically added to the diet as liquid, specialized equipment, such as storage tanks and pumps, is required, which can limit the use of supplemental fat in finishing cattle diets. Dried full-fat corn germ (GERM) is a byproduct of corn wet milling and traditionally has been used for corn oil production. Results in our laboratory indicate that GERM contains approximately 5% moisture and approximately 45% lipid and 12% CP on a DM basis, with a bulk density of 385 g/L and a mean particle size of 2,240 µm (our unpublished observations). Dried full-fat corn germ is free flowing, and it can be handled easily by conventional grain handling systems (our unpublished observations).
Increased intake of linoleic acid or PUFA has been shown to increase peroxidation of tissue lipids (Iritani et al., 1980; Valk and Hornstra, 2000). Vitamin E is a fat-soluble vitamin that serves as an antioxidant and decreases lipid peroxidation in cell membranes either by direct removal of free radicals (Halliwell, 1996) or by preventing the induction of peroxisomal ß-oxidation enzymes and the formation of excess hydrogen peroxide (Hennig et al., 1990). Because GERM contains a high proportion of linoleic acid, we hypothesized that adding vitamin E to finishing-cattle diets containing GERM might improve growth performance and carcass characteristics. Our objectives were to evaluate the effects of GERM as a supplemental fat source in finishing diets containing dry-rolled or steam-flaked corn on cattle growth performance and carcass characteristics and evaluate any interactions between source and concentration of supplemental fat and vitamin E.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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Experiment 1
Three hundred fifty-eight crossbred (British x Continental) beef steers with an initial BW of 319 ± 6 kg were used in a randomized complete block design to evaluate GERM as a supplemental fat source in finishing cattle diets containing dry-rolled corn and wet corn gluten feed. Steers were assigned to six blocks according to a previous dietary treatment regimen consisting of receiving diets containing supplemental tallow or varying concentrations of ground flaxseed. Steers were then assigned randomly within block to one of four treatments, for a total of six pens per treatment, with each pen containing 12 to 16 steers. Pens were soil surfaced, approximately 245 m2, and provided approximately 10 m of linear bunk space (84 to 63 cm of bunk space per steer). Treatments (Table 1) were diets formulated to contain dry-rolled corn, 35% wet corn gluten feed, and 0, 5, 10, or 15% GERM on a DM basis, where GERM replaced a portion of soybean meal and dry-rolled corn. Steers were adapted to the diet without GERM over a period of 18 d, at which time they were weighed, implanted with Synovex Plus (200 mg of trenbolone acetate and 28 mg of estradiol benzoate; Fort Dodge Animal Health, Overland Park, KS), and fed their dietary treatments. Diets were fed for 155 d and were offered once daily at 0900 to allow for ad libitum consumption. At the end of the 155-d finishing period, each pen of steers was weighed as a group before feeding and transported to a commercial abattoir where carcass data were collected. Hot carcass weights and liver scores were obtained at slaughter. Subcutaneous fat thickness over the 12th rib, KPH, marbling score, and USDA quality grades and yield grades were measured after a 24-h chill. Marbling score values were determined by a USDA grader and correspond to the following degrees of marbling and USDA quality grades: 100 to 199 = Devoid, Utility; 200 to 299 = Practically Devoid, Standard; 300 to 399 = Traces, Standard; 400 to 499 = Slight, Select; 500 to 599 = Small, Low Choice; 600 to 699 = Modest, Choice; 700 to 799 = Moderate, High Choice; 800 to 899 = Slightly Abundant, Low Prime; 900 to 999 = Moderately Abundant, Prime; 1,000 to 1,099 = Abundant, High Prime. Final BW was calculated by dividing HCW by a common dressing percent of 63.5%.
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). Statistical Analyses
Growth performance data, HCW, dressing percent, fat thickness, KPH, and marbling score were analyzed as a randomized complete block design using the GLM procedure of SAS (SAS Inst., Inc., Cary, NC), with pen as the experimental unit and model effects including block and treatment. Residual error served as the error term. Yield grade and quality grade data, as well as the incidence of liver abscesses and dark cutting were analyzed as nonparametric data using the Genmod procedure of SAS, with model effects including block and treatment. Contrasts were used to test for linear, quadratic, and cubic effects of GERM, and an alpha level of 0.05 was used to decrease the probability of committing a Type I error.
Experiment 2
Eight hundred eighty-eight crossbred (British x Continental) beef heifers with an initial BW of 380 ± 10 kg were used in a randomized complete block design to compare the effects of adding GERM to cattle finishing diets with those of adding tallow or no added fat, as well as to evaluate any interactions between source and concentration of supplemental fat and vitamin E. Two hundred eighty-six heifers were purchased from a commercial sale barn in southern Oklahoma, and the remaining heifers were from two commercial feed yards in central Kansas. Heifers were transported to the Kansas State University Beef Cattle Research Center in Manhattan Kansas. Heifers were received and processed over a period of 8 d and processing included vaccination against bovine respiratory syncytial virus, bovine virus diarrhea, infectious bovine rhinotracheitis, and parainfluenza using modified live viruses (Bovishield 4, Pfizer Animal Health, Exton, PA), vaccination against common clostridial diseases using a clostridial bacterintoxoid (Fortress 7; Pfizer Animal Health), and implanting with Revalor H (140 mg of trenbolone acetate and 14 mg of estradiol benzoate; Intervet, Millsboro, DE). Immediately after processing, each heifer was assigned randomly to one of 48 pens so that each pen contained 14 to 23 heifers, depending on pen size. Pens were soil surfaced, and were either approximately 245 m2 or 460 m2, and provided approximately 10 m of linear bunk space (72 to 44 cm of bunk space per heifer). Pens were assigned to four blocks according to date of implanting, and treatments (Table 2) were arranged in a 4 x 2 factorial that consisted of cattle finishing diets formulated to provide no added fat (control), 4% tallow (TALLOW), or 10% or 15% GERM on a DM basis, with or without 224 IU/kg of diet DM of added vitamin E. A portion of soybean meal and steam-flaked corn was replaced by GERM. Treatments were assigned randomly within block and were replicated equally across pen size. Heifers were adapted to the control diet over a period of 17 d, at which time heifers were weighed and dietary treatments were initiated. Diets were fed for 105 d and were offered once daily at 0900 to allow for ad libitum consumption. At the end of the 105-d finishing period, each pen of heifers was weighed as a group before feeding and transported to a commercial abattoir, where carcass data were collected in the same manner as in Exp. 1, with the exception that LM area also was measured. Final BW was calculated by HCW by a common dressing percent of 63.5%. Dietary ingredients were sampled weekly throughout the experiment and analyzed in the same manner as in Exp. 1.
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Growth performance data, HCW, dressing percent, fat thickness, LM area, KPH, and marbling score were analyzed as a randomized complete block design using the GLM procedure of SAS, with pen as the experimental unit and model effects including block, fat treatment, vitamin E, and fat treatment x vitamin E. Residual error served as the error term. Yield grade and quality grade data, as well as the incidence of liver abscesses and dark cutting carcasses, were analyzed as non-parametric data using the Genmod procedure of SAS, with model effects including block, fat treatment, vitamin E, and fat treatment x vitamin E. Contrasts were used to compare the control diet with the mean of diets containing added fat, to compare the TALLOW diet with the diet containing 10% GERM, and to test for linear and quadratic effects of GERM by using the control diet and diets containing 10 and 15% GERM. Because only preplanned contrasts were used, they were not protected by an overall F-test. An alpha level of 0.05 was used to decrease the probability of committing a Type I error.
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Results and Discussion |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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Finishing performance and carcass characteristics of steers fed finishing diets containing different concentrations of GERM are shown in Table 3. Increasing GERM in the diet linearly deceased (P < 0.02) DMI. Decreased DMI in cattle fed finishing diets containing supplemental fat has previously been reported (Krehbiel et al., 1995; Zinn and Shen, 1996; Ramirez and Zinn, 2000). Whether this effect of fat supplementation on DMI was caused by a decrease in diet acceptability or was a result of a chemostatic response to increased energy density of diets is unknown. In contrast to reports of supplemental fat decreasing DMI in cattle, Zinn (1989) fed steers a steam-rolled barley-based finishing diet containing no added fat or 4 or 8% supplemental fat in the form of yellow grease, blended animal vegetable fat, or crude soybean lecithin and reported that supplemental fat, regardless of concentration or source, did not affect DMI. Brandt and Anderson (1990) fed steers steam-flaked sorghum-based diets containing no added fat or 3.5% supplemental fat as soybean oil, tallow, or yellow grease and reported no differences in DMI due to fat supplementation. Brandt et al. (1992) also fed steers diets based on steam-flaked corn or steam-flaked sorghum and containing no added fat or 4% yellow grease and reported no effects of supplemental fat on DMI.
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, 1989; Brandt and Anderson, 1990), not affected (Brandt et al., 1992; Zinn and Shen, 1996; Ramirez and Zinn, 2000), or decreased ADG (Hatch et al., 1972).
Increasing GERM in the diet improved G:F of steers quadratically (P < 0.05), and G:F followed the same trend as ADG, with steers fed the diet containing 10% GERM having the greatest G:F. Although improved G:F is commonly observed in cattle consuming finishing diets supplemented with fat (Brandt and Anderson; 1990; Brandt et al., 1992; Ramirez and Zinn, 2000), providing supplemental fat to finishing cattle has failed to improve G:F in some experiments. Hatch et al. (1972) fed steers diets based on dry-rolled corn and containing 0, 3, or 6% animal fat and reported no effect of supplemental fat on G:F. Buchanan-Smith et al. (1974) fed steers diets based on ground-shelled corn and containing 0 or 5% animal fat and reported that supplemental fat failed to affect G:F.
Hale (1986) noted that inconsistent results in growth performance of cattle fed supplemental fat might be attributable to the grain source used in the basal diet. Presumably, corn-based diets would contain more fat than wheat-, barley-, or sorghum-based diets, due to the higher fat content of corn (NRC, 1996). Nonetheless, subsequent experiments examining the effects of supplemental fat on cattle growth performance where corn-based diets were compared directly with sorghum- or wheat-based diets have failed to prove this hypothesis (Brandt et al., 1992; Zinn, 1992).
Increasing GERM in the diet increased fat thickness (linear; P < 0.05), KPH (linear; P < 0.05), and the percentage of USDA Yield Grade 4 carcasses (quadratic; P < 0.03), with steers fed the diet containing 15% GERM having the greatest percentage of USDA Yield Grade 4 carcasses. The effects of supplemental fat on carcass characteristics of cattle seem variable. Zinn (1989) fed steers 0, 4, or 8% supplemental fat for 125 d and reported a linear increase in HCW, KPH, marbling score, and retail yield. Brandt and Anderson (1990) fed steers diets containing no added fat or 3.5% supplemental fat as soybean oil, tallow, or yellow grease for an average of 122 d and reported increased HCW of steers supplemented with yellow grease and increased dressing percent due to supplemental fat, regardless of source. Zinn (1992) fed steers diets based on steam-flaked corn or steam-flaked wheat that contained no added fat or 6% supplemental fat as either yellow grease or cottonseed oil for 121 d and reported that supplemental fat increased HCW, dressing percent, LM area, KPH, and marbling score. In contrast to the above experiments, Brandt et al. (1992) fed steers diets containing no added fat or 4% yellow grease for 100 d and reported no effects of supplemental fat on carcass characteristics. Krehbiel et al. (1995) fed steers diets containing no added fat or 4% supplemental fat as tallow for 112 d and found no differences in carcass characteristics due to supplemental fat. Furthermore, Hatch et al. (1972) fed steers diets based on dry-rolled corn and containing 0, 3, or 6% animal fat and reported no effect of supplemental fat on carcass characteristics as well.
Increasing GERM in the diet decreased the incidence of liver abscesses (quadratic; P < 0.02), which was greater for steers fed the diet containing no GERM and less for steers fed diets containing GERM. Liver abscesses are believed to result primarily from acidosis-induced rumenitis, which allows Fusobacterium necrophorum, the ruminal bacteria identified to be the primary etiological agent of liver abscesses, to enter the portal circulation and colonize in the liver (Nagaraja and Chengappa, 1998). Because GERM replaced dry-rolled corn in our diets and decreased DMI, a decrease in liver abscesses as a result of adding GERM to diets might be the result of decreased starch or altered feed intake patterns, which might have decreased the incidence of acidosis and subsequent rumenitis. Another possible explanation for the decrease in the incidence of liver abscesses in steers fed diets containing GERM is that GERM diets may have somehow suppressed the growth of Fusobacterium necrophorum.
Increasing GERM in the diet decreased (P < 0.04) the percentage of dark-cutting carcasses in a cubic fashion, with the percentage of dark-cutting carcasses being greater with the diet containing 5% GERM, and least for the diets containing no GERM or 10 and 15% GERM. This effect of GERM on the percentage of dark-cutting carcasses is difficult to explain and, based on the limited number of dark-cutting carcasses, might be spurious.
Experiment 2
No fat treatment x vitamin E interactions (P 0.08) were detected; therefore, only main effects of fat treatment and vitamin E are presented. The lack of a fat treatment x vitamin E interaction suggests that any effects on growth performance or carcass characteristics due to vitamin E supplementation did not depend on the source or level of supplemental fat fed. The effects of supplemental TALLOW and GERM on growth performance and carcass characteristics of finishing heifers are shown in Table 4. Supplemental fat decreased DMI (P < 0.01), marbling score (P < 0.01), the percentage of carcasses grading USDA Choice (P < 0.01), and increased (P < 0.01) the percentage of carcasses grading USDA Standard. The decrease in marbling score observed in Exp. 2 contrasts with the results of Exp. 1, in which marbling score was not affected by supplemental fat. The reasons for the conflicting results for marbling score between Exp. 1 and Exp. 2 are not clear, but might be related to corn processing method (dry-rolled vs. steam-flaked), type of cattle used (steers vs. heifers), or length of finishing period (155 vs. 105 d). The effect of supplemental fat on marbling score has been variable, with supplemental fat reported to increase (Zinn, 1989), have no effect (Zinn, 1988, 1992; Brandt et al., 1992), or decrease marbling score (Clary et al., 1993). Owens and Gardner (2000) reviewed 21 experiments consisting of a total of 2,016 cattle provided supplemental fat. Owens and Gardner (2000) reported that when carcass traits were adjusted to a standard carcass weight, providing up to 2% supplemental fat increased dressing percent, LM area, and quality grade, whereas higher amounts of supplemental fat reversed these effects.
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, are not readily explained, but might be related to decreased starch intake as a result of decreases in DMI or the replacement of starch with supplemental fat in the diet. Smith and Crouse (1984) reported that acetate provides 70 to 80% of the acetyl units for in vitro lipogenesis in s.c. adipose tissue of steers, but only 10 to 25% of the acetyl units for i.m. adipose tissue, whereas glucose provides only 1 to 10% of the acetyl units for s.c. adipose tissue but 50 to 75% of the acetyl units for i.m. adipose tissue. Because i.m. adipose tissue prefers glucose as a precursor for de novo lipid synthesis, any decrease in starch intake might explain in part the decreased quality grades in cattle fed increasing dietary fat.
Among heifers fed finishing diets containing TALLOW or 10% GERM, supplemental fat source did not affect DMI (P = 0.76), ADG (P = 0.54), or G:F (P = 0.62). There was a tendency (P < 0.06), however, for heifers fed diets containing 10% GERM to have increased KPH compared with heifers fed finishing diets containing TALLOW. These data suggest that including GERM at 10% of cattle finishing diets can effectively replace approximately 4% TALLOW as a source of supplemental fat. Increasing GERM decreased final BW (quadratic; P < 0.04), with heifers fed the control diet or diets containing 10% GERM having similar final BW and heifers fed the diet containing 15% GERM having the lowest final BW. Increasing GERM decreased DMI (linear; P < 0.01), which agrees with the results of Exp. 1. Increasing GERM decreased ADG in a quadratic (P < 0.02) fashion, with ADG by heifers fed the diet containing 10% GERM slightly greater than by those fed the control diet, but least by heifers fed the diet containing 15% GERM. Zinn (1994) reported that optimal growth performance response in finishing cattle to supplemental fat is obtained when total fat intake is less than 1.6 g/kg of BW. In our experiment, total fat intake was approximately 0.6, 1.4, and 1.7 g/kg of BW for heifers fed the control diet or diets containing 10 or 15% GERM, respectively. Changing the diet from control to 10% GERM improved ADG of heifers by approximately 0.8%; however, changing from 10% GERM to 15% GERM decreased ADG by 7.4%. According to Zinn (1994), decreased growth performance of finishing cattle fed excessive amounts of supplemental fat is caused primarily by decreased intestinal digestibility of fat. Increasing GERM improved (quadratic; P < 0.03) G:F of heifers, with heifers fed the diet containing 10% GERM having the greatest G:F
Increasing GERM decreased HCW quadratically (P < 0.04), with heifers fed the control diet or the diet containing 10% GERM having similar HCW, and heifers fed the diet containing 15% GERM having the lightest HCW. Increasing GERM decreased (quadratic; P < 0.01) the percentage of USDA Yield Grade 2 carcasses, with heifers fed the diet containing 10% GERM having the least percentage of USDA Yield Grade 2 carcasses and heifers fed the diet containing 15% GERM having the greatest. Increasing GERM increased (quadratic; P < 0.01) the percentage of USDA Yield Grade 4 carcasses, with heifers fed the diet containing 10% GERM having the greatest percentage of USDA Yield Grade 4 carcasses and heifers fed the diet containing 15% GERM having the least. Increasing GERM decreased marbling score (linear; P < 0.01), the percentage of carcasses grading USDA Choice (linear; P < 0.01), and linearly increased the percentage of carcasses grading USDA Standard (P < 0.01). Increasing GERM linearly decreased (P < 0.02) the incidence of liver abscesses, which agrees with the results of Exp. 1.
The addition of vitamin E did not affect DMI (P = 0.42), ADG (P = 0.11), or G:F (P = 0.18) of heifers, but it marginally increased (P < 0.04) the percentage of carcasses grading USDA Select and decreased (P < 0.01) the percentage of carcasses grading USDA Standard (Table 5). Results of supplementing vitamin E to finishing cattle are mixed. Arnold et al. (1992) reported that supplementing 300 to 2,000 IU of vitamin E per animal daily did not affect growth performance or carcass characteristics of finishing cattle. In contrast, Secrist et al. (1997) reviewed 21 experiments consisting of feedlot cattle fed supplemental vitamin E at 20 to 2,000 IU per animal daily and reported that vitamin E increased ADG by 2.9% and tended to improve G:F by 1.8%, but did not affect carcass characteristics. According to Secrist et al. (1997), the variability of results regarding vitamin E supplementation among feedlot cattle might depend on previous nutritional history and vitamin E status, stress level, and vitamin E concentration of the basal diet. We targeted an intake of approximately 2,000 IU of vitamin E/heifer daily. Although not significant, supplemental vitamin E improved ADG by 2.3% and G:F by 2.6% in our experiment, which agrees with the findings of Secrist et al. (1997).
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Implications |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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Footnotes |
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3 Current address: McElhaney Cattle Co., Wellton, AZ 85356.
4 Current address: Golden Belt Feeders, Kinsley, KS 67547.
5 Current address: Kansas Feeds, Dodge City, KS 67801.
2 Correspondence: Call Hall, Room 133 (phone: 785-532-1204; fax: 785-532-5681; e-mail: jdrouill{at}oznet.ksu.edu).
Received for publication October 4, 2004. Accepted for publication June 20, 2005.
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Literature Cited |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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