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Summary The objective of this study was to examine the effect of different forage and supplement combination s on forage and supplement intake and ruminal parameters in steers. Six ruminally fistulated steers were assigned to 1 of 4 treatments during 4 different data collection periods. Treatments were 1) Hay +wet brewers grains (WBG); 2) Hay +dried distillers grains (DDG); 3) round bale silage (RBS) + WBG; and 4) RBS + DDGS. Forage was offered in 2 feedings per day at 110% of the forage intake. Supplements and a mineral premix were offered to steers once daily in the morning. Supplements were offered at 0.5% of body weight (BW) on a dry matter (DM) basis. Forage, supplement and total dry matter intake (DMI) and a pparent total tract digestibility were measured for each forage supplement combination. Ruminal pH and ammonia N concentration were measured for each forage supplement combination. Forage type (hay or RBS) did not affect forage DMI, but DDG tended to inc rease forage DMI compared to WBG. Supplement DMI tended to be greater for steers fed Hay compared to RBS. Supplement DMI was similar between supplements. Total DMI was similar between forage types, but total DMI was greater for steers when offered DDG c ompared to WBG. Total tract digestibility did not differ between forage types, but DDG supplementation had greater total tract digestibility than WBG. Daily mean ruminal pH was greater in RBS fed steers compared to Hay. In contrast, supplement type did not affect mean daily ruminal pH (mean = 6.32). Daily mean ruminal ammonia N concentration did not differ between forage types. Likewise, daily mean ruminal ammonia N concentr ation did not differ between supplement types. Ruminal pH and ammonia N concentration were maintained in ranges adequate to support normal ruminal metabolism and support adequate cattle performance. Introduction Meeting the nutrient demands of cattle t hrough supplementation is of critical importance for growing animals and the cow herd. However, utilizing cereal grains as supplements can decrease forage intake in cattle through depression of ruminal pH. Decreased ruminal pH alters ruminal bacteria populations which result in a decrease in fiber digestion and negatively affects intake of forage. Florida based research has demonstrated that corn based, starch containing supplements decreased forage intake and digestibility in bermudagrass f ed cattle. Therefore co product supplements that are characterized as low starch may optimize forage intake and utilization. However, there has been no extensive evaluation of dried distillers grains (DDG) or wet brewers grains (WBG) when coupled with su btropical forages. Evaluating the effectiveness of different forage supplement combinations on ruminal metabolism in beef cattle is important in Effect of Wet Brewers Grains or Dried Distillers Grains as Supplements to Round Bale Silage or Dry Hay on Intake and Digestibility in Steers Megan Thomas, Matt Hersom, Todd Thrift, Joel Yelich 1 Forage type had no effect on intake or digestibility, whereas dried distillers grains increased intake and digestibility compared to wet brewers grains. Round bale silage forage supported increased ruminal pH and ammonia N concentration compared to hay. 1 Department of Animal Scienc es, University of Florida, Gainesville, FL
understanding the associative effects of these feeds. The objective of this study was to evaluate the combi nation of Hay and RBS with DDG and WBG. Materials and Methods Six, 2 yr old ruminally cannulated Brangus steers (mean BW = 954 lb) were randomly assigned to 1 of 4 treatments in a 6x4 Latin square design with 4 periods. Treatments included: 1) Hay + WB G; 2) Hay+DDG; 3) RBS+WBG; 4) RBS+DDG. Hay and RBS were from similar cuttings of Tifton 85 bermudagrass. Forages were ground to a mean chop length of 4 in. Forage was offered in two feedings per day Suppleme nts and a mineral premix were offered to steers once daily in the morning. Supplements were offered at 0.5% of BW on a DM basis. Steer BW was collected at the start of every 23 d period. Steers were adapted to each forage supplement combination for 14 d Following adaptation to the diet steers were adapted to harnesses and bags for total fecal collection from d 10 to 14. On d 15 to 19 total fecal output and voluntary DMI were measured. On d 20 ruminal fluid was collected at hourly intervals starting 2 hr prior to the morning feeding to 12 hr after the morning feeding. Ruminal fluid pH was immediately measured and aliquots frozen for analysis of ruminal ammonia N concentration. Starting on d 21 a sequential introduction of duplicate nylon bags with a sample of 8 g DM of forage or 4 g DM of supplement were placed in each steer corresponding to the current treatment at 0, 6, 12, 24, 36, and 72 h for an in situ DM disappearance study. Dry matter pools were partitioned into three fractions as described by Coblentz et al. (1998). Those fractions are the A fraction which is considered to be immediately soluble; the B fraction which is starch or nitrogen degraded at a measurable rate; and the C fraction which is considered undegradable in the rumen. Determ ination of these fractions was performed using PROC NLIN of SAS (SAS Inst. Inc., Cary, NC). Data were fit to the model described by Coblentz et al. (1998). The model calculates fractions B and C, lag time, and degradation rate constant (K d ). Fraction A was calculated by difference [total N or starch (B+C)], and maximum theoretical extent of degradation by difference [total N or starch C) (Coblentz et al., 1998). Dry matter intake, fecal output, and apparent digestibility data were analyzed using th e MIXED procedure of SAS (SAS Inst., Inc., Cary, NC). The model contained the effects of forage, supplement, period, and the interactions. Period was considered the random effect. Data collected for rumen pH and ammonia N concentrations were analyzed us ing the MIXED procedure of SAS. Effects of forage, supplement, hour, and the interactions were included in the model. Data was analyzed using a repeated measures procedure. Means were separated using the P diff option when protected by a significant F v alue ( P < 0.05). For both models the interaction of forage, supplement, and period or hour were not significant ( P > 0.05), thus these means are presented separately. Kinetic data were analyzed using the GLM procedure of SAS with least squares means calc ulated. Source of variation included in the model was feedstuff. We considered steer the experimental unit for this analysis. Results Forage type (hay or RBS) did not affect forage DMI (mean = 15.65 lb), but DDG tended ( P = 0.10) to increase forage DMI compared to WBG (Table 2). Supplement DMI tended ( P = 0.08) to be 0.30 lb greater for Hay compared to RBS. Supplement DMI was similar ( P = 0.11) between DDG and WBG. Total DMI was similar ( P = 0.76) between forage types. However as a result of the small differences in hay and supplement DMI, total DMI was greater ( P = 0.05) for steers when offered DDG compared to WBG. Fecal output was similar between forage and supplement types. Total tract digestibility did not differ ( P = 0.30) between forage types (mean = 56.7%). In contrast, DDG supplementation resulted in 3.2 percentage unit greater ( P = 0.007) total tract digestibility than WBG. In situ digestion kinetics for forages and supplements are presented in Table 1. The proportion of rapidly degradable (Fraction A)
DM was 54% greater ( P < 0.001) and extent of degradation was 26% greater ( P = 0.004) for RBS compared to HAY. In contrast, the undgradable proportion (Fraction C) of DM was 43% less ( P = 0.004) in RBS than HAY. The slowly degradable proportion (Fraction B) of DM did not differ ( P = 0.43, mean = 47.2%), nor did l ag time ( P = 0.13, mean = 4.86 h) or rate of degradation ( P = 0.2 2, mean = 0.053) between forage sources. Similar trends were observed between supplement sources. The proportion of rapidly degradable DM was 40% greater ( P < 0.001) and extent of degradation was 10% greater ( P = 0.03) for DDG compared to WBG. The undeg radable portion of WBG was 60% greater ( P = 0.03) than DDG. Fraction B, l ag time, and r ate of degradation were similar ( P 0.02) between DDG and WBG supplements. Daily mean ruminal pH (Table 3) was greater ( P = 0.05) in RBS fed steers compared to Hay. Additionally, a forage x hour interaction was evident for ruminal pH. Steers offered RBS had greater ( P < 0.05) ruminal pH from 2 h prior to feeding to 2 h post feeding compared to Hay fed steers, thereafter ruminal pH were similar. In contrast, supple ment type did not affect mean daily ruminal pH (mean = 6.32). However, a supplement x hour interaction was also evident for ruminal pH. Steers offered WBG had greater ( P < 0.05) ruminal pH from 1 h after feeding to 4 h after feeding compared to DDG, ther eafter ruminal pH were similar. There was a forage x supplement interaction ( P < 0.001) for ruminal ammonia N. Ruminal ammonia N was greater ( P < 0.05) for H ay WBG than RBS WBG, which was greater ( P < 0.05) than H ay DDG which was greater ( P < 0.05) than RBS DDG. There was a forage x hour interaction ( P < 0.001) for ruminal ammonia N concentration. Steers offered Hay had greater ( P < 0.05) ruminal ammonia N concentration compared to RBS every hour except for 1 h post feeding to 4 h post feeding. There was also a supplement x hour interaction ( P < 0.001) for ruminal ammonia N concentration. Steers offered WBG had greater ( P < 0.05) ruminal ammonia N concentration compare d to DDG every hour except for 1 h post feeding. Marginal differences in forage and supplement DMI resulted in increased total DMI for DDG compared to WBG supplement treatments. Ruminal pH values remained above critical pH values indicative of comprised ruminal function. Ruminal ammonia N concentrations were generally greater for Hay than RBS and WBG compared to DDG. Literature Cited Coblentz, W.K. et al. 1998.J. Dairy Sci. 81:150.
Table 1. Composition of forages and supplements offered to steers Hay Round bale silage Wet Brewers Grains Dried Distillers Grains Dry matter, % 92.4 50.7 20.2 87.7 % of dry matter Organic matter 94.2 91.2 97.9 95.1 Crude protein 8.2 8.9 33.7 31.6 Neutral detergent fiber 74.6 72.8 43.7 37.1 Acid detergent fiber 37.0 42.7 24.5 17.4 Total digestible nutrients 46.0 57.3 75.0 81.7 Table 2. Effect of forage and supplement type on intake, digestibility, and in situ digestion kinetics Forage type Supplement type Hay RBS 1 SEM 2 P value DDG 3 WBG 4 SEM P value Forage DMI 5 lb 15.36 15.93 0.67 0.54 16.40 14.90 0.65 0.10 Supplement DMI, l b 4.95 4.64 0.12 0.08 4.93 4.66 0.12 0.11 Total DMI, lb 20.31 20.57 0.61 0.76 21.33 19.56 0.61 0.05 Fecal output, lb 8.65 9.02 0.31 0.41 8.90 8.77 0.31 0.75 Total Tract Apparent Digestibility, % 57.3 56.1 0.75 0.30 58.3 55.1 0.75 0.007 In situ dry matter digestion kinetics Fraction A, % 8.73 18.89 1.00 <0.001 42.78 30.48 1.29 <0.001 Fraction B, % 45.29 49.05 3.21 0.43 46.04 48.86 2.16 0.38 Fraction C, % 45.98 32.06 2.61 0.004 12.90 20.66 2.20 0.03 Lag time, h 3.14 6.58 1.50 0.13 1.26 2.06 0.53 0.29 Rate (k d ), h 0.024 0.082 0.031 0.22 0.041 0.051 0.006 0.20 Extent, % 54.02 67.94 2.61 0.004 87.10 79.34 2.20 0.03 1 Round bale silage 2 Standard error of mean 3 Dried distillers grains 4 Wet brewers grains 5 D ry matter intake
Table 3. Effect of forage and supplement types on hourly ruminal pH in steers. Forage Supplement Hour H ay RBS 1 DDG 2 WBG 3 2 6.29 a 6.57 b 6.44 6.42 1 6.39 a 6.67 b 6.53 6.52 0 6.51 a 6.73 b 6.63 6.61 1 6.22 a 6.46 b 6.26 a 6.42 b 2 6.17 a 6.34 b 6.14 a 6.37 b 3 6.11 6.24 6.08 a 6.27 b 4 6.10 6.21 6.08 a 6.23 b 5 6.10 6.19 6.08 6.20 6 6.16 6.23 6.16 6.23 7 6.25 6.30 6.27 6.29 8 6.28 6.35 6.36 6.28 9 6.30 6.40 6.39 6.30 10 6.39 6.40 6.44 6.34 11 6.36 6.33 6.36 6.32 12 6.33 6.25 6.28 6.30 SEM 0.06 0.06 P value 0.004 0.004 Mean 6.25 a 6.39 b 6.30 6.34 SEM 0.05 0.04 P value 0.05 0.51 1 Round bale silage 2 Dried distillers grains 3 Wet brewers grains 4 Standard error of mean a, b Means with different superscripts differ (P<0.05)
Table 4. Effect of forage and supplement types on daily mean and hourly ruminal ammonia N (mg/dL) in steers. Treatment H ay DDG H ay WBG RBS 1 DDG 2 RBS WBG 3 SEM 4 P value Mean ammonia N 7.83 a 12.58 b 6.84 c 9.20 d 0.21 <0.001 Forage Supplement Hour H ay RBS DDG WBG 2 8.43 a 6.32 b 6.09 a 8.66 b 1 8.34 a 6.43 b 6.27 a 8.51 b 0 8.71 a 6.68 b 6.71 a 8.68 b 1 12.08 11.31 11.07 12.32 2 13.47 13.72 11.83 a 15.37 b 3 12.81 13.35 10.51 a 15.65 b 4 10.88 10.09 7.54 a 13.43 b 5 9.79 a 7.50 b 6.01 a 11.28 b 6 9.29 a 5.93 b 5.23 a 9.98 b 7 9.12 a 5.50 b 5.15 a 9.47 b 8 9.23 a 5.18 b 5.44 a 8.97 b 9 9.77 a 5.26 b 5.81 a 9.22 b 10 10.63 a 7.48 b 7.62 a 10.49 b 11 10.35 a 8.19 b 7.71 a 10.83 b 12 10.22 a 7.40 b 7.07 a 10.54 b SEM 2.52 2.52 P value <0.001 <0.001 1 Round bale silage 2 Dried distillers grains 3 Wet brewers grains 4 Standard error of mean a, b c, d Means with different superscripts differ (P<0.05)