Digestion characteristics, feed intake and live weight gain by cattle consuming forage supplemented with defatted rice bran or other feedstuffs

ANIMAL FEED SCIENCE AND TECHNOLOGY

E LS EVI ER

Animal Feed Science and Technology 47 (1994) 259-275

Digestion characteristics, feed intake and live weight gain by cattle consuming forage supplemented with defatted rice bran or other feedstuffs L.A. Forster, Jr., A.L. Goetsch*, D.L. Galloway, Sr., W. Sun, A.R. Patil, Z.B. Johnson Department ofAnimal Sciences, University of Arkansas, Fayetteville, AR 72701. USA

(Received l0 June 1993; accepted 16 November 1993)

Abstract

Effects of supplementing cattle with defatted rice bran compared with full-fat rice bran, ground corn or wheat middlings on feed intake, digestibility and live weight gain (LWG) were determined. In Experiment 1, in situ (ruminal) dry matter disappearance in two steers consuming forage was 75, 45, 77 and 53% at 12 h (standard error (SE) 4.4), and 86, 95, 83 and 82% at 48 h (SE 0.6) for full-fat rice bran, corn, wheat middlings and defatted rice bran, respectively. In Experiment 2, six Holstein steer calves (193 _+1.3 kg average trial body weight (BW); 6 X 6 Latin square) consumed a 1 : 1 : 1 mixture of alfalfa, orchardgrass and bermudagrass hay ad libitum without supplementation (Control), or with 0.80% of BW of full-fat rice bran (FR), 0.62% of BW of corn (C), 0.81% of BW of wheat middlings (W), 0.80% of BW of defatted rice bran (L-DR) or 1.10% of BW of defatted rice bran (H-DR). Total organic matter intake was lower (P< 0.05 ) for FR than for C, W, L-DR and H-DR (5.65, 5.48, 5.96, 5.90, 6.03 and 5.86 kg per day; SE 0.127), digestibility of neutral detergent fiber was 53.3, 49.5, 53.7, 51.4, 50.9 and 49.8% (SE 1.13 ), and digestible organic matter intake was 2.96, 2.98, 3.35, 3.32, 3.17 and 3.11 kg per day (SE 0.088) for Control, FR, C, W, L-DR and H-DR, respectively (C and W greater than Control and FR; P < 0.05 ). In Experiment 3, six mature beef cows ( 564 + 37 kg BW) with cannulae in the rumen and duodenum (6 × 6 Latin square) were fed the same hays with similar dietary proportions of supplement. True ruminal nitrogen disappearance was greatest (P<0.05) for W (62.5, 60.2, 63.0, 79.6, 68.1 and 65.7% for Control, FR, C, W, L-DR and H-DR, respectively; SE 3.24), microbial efficiency was similar among treatments (P> 0.10), and acetate:propionate in ruminal fluid was decreased (P< 0.05 ) by FR, L-DR and H-DR relative to Control (4.06, 3.69, 4.00, 4.09, 3.89 and 3.80 for Control, FR, C, W, L-DR, and H-DR, respectively; SE 0.053). In Experiment 4, crossbred beef *Corresponding author. 0377-8401/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved SSD10377-8401 (93) 00584-I

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calves (48 steers and 48 heifers; 232 + 2.1 kg initial BW) grazed paddocks with fescue, clover and bermudagrass in the spring for 84 days and were supplemented as in Experiment 2. LWG was lower (P< 0.05 ) for W, L-DR and H-DR than for FR and C ( 1.06, 1.18, 1.14, 0.99, 1.04 and 0.98 kg per day for Control, FR, C, W, L-DR and H-DR, respectively; SE 0.027).

1. Introduction

Ruminants ingesting forage are frequently supplemented with higher-quality feedstuffs to achieve desired levels of performance. Because ruminal microbes degrade fiber and inexpensive agricultural byproducts are abundant, byproducts are common ingredients in ruminant diets. One such commodity available in some areas is rice bran, with estimated production in the USA of 0.54 billion t in 1990 (Young et al., 1991 ). Rice bran differs from other byproducts such as soybean hulls in having higher levels of ether extract (e.g. 17%; White and Hembry, 1985 ) and starch, and possibly limited potential degradability of fiber (Belyea et al., 1989 ). Effects of supplementation of forage with rice bran on digestion and fermentation characteristics have been variable (Cardenas Garcia et al., 1992, 1993). Currently, oil is extracted from some rice bran, although the effects of supplementation with defatted rice bran on feed intake, digestibility and performance by ruminants relative to full-fat rice bran and other feedstuffs have not been extensively investigated. Objectives of this study were to compare feed intake, digestion characteristics and live weight gain (LWG) by cattle consuming forage supplemented with different levels of defatted rice bran or with full-fat rice bran, corn or wheat middlings.

2. Materials and methods 2. I. Experiment 1

Two mature beef steers, with a cannula in the rumen, were fed a 1 : 1 : 1 mixture (hand-mixed) of alfalfa (Medicago sativa, 50-75% bloom), orchardgrass (Dactylis glomerata, early anthesis) and bermudagrass (Cynodon dactylon, early heading) hay (long-stemmed) at 1.6% of body weight (BW) (dry matter (DM) basis) for 14 days. Steers were housed indoors in 3.1 m × 4.3 m pens, with free access to water and trace mineral salt (92-97% NaCI, > 2% Fe, 3% Mn, 0.33% Cu, 0.007% I, 0.0025% Co). Full-fat rice bran, corn, wheat middlings or defatted rice bran (composites taken during Experiment 2; Table 1 ) were placed ( 1.5 g air-dry) in duplicate 8 c m × 12 cm Dacron bags (50-70 # pore size) attached at 1 cm intervals along a 60 cm long nylon cord weighted with a 30 g sinker. Bags were soaked in tap water for approximately 5 min before being suspended in the rumen for 0, 3, 6, 12, 18, 24, 48 or 72 h; all bags were removed at the same time.

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261

After removal, the bags were washed, dried at 100 °C for 24 h and weighed. DM disappearance was calculated and the concentration and rate of disappearance of insoluble but potentially digestible DM were determined using the formula p = a + b ( 1 --eCt), where p is percentage degradation at time t, a is soluble DM, b is insoluble but potentially degradable DM, c is rate of disappearance of b (Orskov and McDonald, 1979). Data were analyzed with substrate in the statistical model by the General Linear Models procedures of the Statistical Analysis Systems Institute Inc. (1985). Differences among substrates were determined by least significant difference procedures when the overall F-test was significant (e<0.10). 2.2. E x p e r i m e n t 2

Six Holstein steer calves ( 193 +_ 1.3 and 273 _+4.4 kg initial and final unshrunk BW, respectively) were used in a 6 × 6 Latin square with 14 day periods. Steers were placed in tie stalls (1.2 m × 2 . 4 m) in an enclosed barn with free access to water. Steers were weighed (unshrunk) at the beginning of the study and on Day 14 of each period at 13: 00 h. Steers were fed a 1 : 1 : 1 mixture of the same hays (long-stemmed) used in Experiment 1 at 105-110% of the consumption on the preceding few days. Steers were not supplemented (Control) or were offered (DM basis) 0.80% of BW of full-fat rice bran (FR treatment), 0.62% of BW of corn (C treatment), 0.81% of BW of wheat middlings (W treatment), 0.80% of BW of defatted rice bran (LDR treatment) or 1.10% of BW of defatted rice bran (H-DR treatment). The FR, C, W and H-DR supplements provided a similar quantity of digestible energy (National Research Council, 1984). Hay and supplements were fed at 08: 00 and 16:00 h in equal meals. Supplement was contained in buckets and given before hay was offered; hay was placed in feeders with buckets containing supplement. All steers were given 10 g (air-dry) of a 3:1 mixture of NaC1 and trace minerals (>12% Zn, 10% Mn, 5% K, 2.5% Mg, 1.5% Cu, 0.3% I, 0.1% Co, 0.02% Se). Steers received 8 g of dicalcium phosphate daily top-dressed on hay offered at 08:00 h. Hay refusals (bermudagrass) were collected and weighed immediately before the 08: 00 h meal. Fecal grab samples were taken on Days 11-14, at 12 h intervals advancing 3 h daily, and frozen. Individual samples were dried in a forced-air oven at 55 ° C and ground to pass a 2 m m screen. Hay and supplement composites were constructed from samples taken on Days 9-14 and ground to pass a 1 m m screen. Feed and fecal composites were analyzed for DM, ash, N (Association of Official Analytical Chemists (AOAC), 1984 ), neutral detergent fiber (NDF; Goering and Van Soest, 1970)and acid-insoluble (2 N HC1)ash (Van Keulen and Young, 1977 ). Amylase was used to determine NDF in supplements (Cherney et al., 1989), and supplements were analyzed for ether extract (AOAC, 1984). High levels of fat can inflate estimates of NDF concentration if separate water and lipid phases develop, resulting in a low concentration of detergent in the water phase (Robertson and Van Soest, 1977 ). However, separate phases were not observed, and

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NDF concentrations for full-fat rice bran were similar to those in previous reports (Belyea et al., 1989; Warren and Farrell, 1990). Digestibilities of organic matter (OM), NDF and N were determined with acid-insoluble ash as an interhal marker. Hay was analyzed for acid detergent fiber (ADF; containing insoluble ash) and lignin (Goering and Van Soest, 1970). Cellulose was determined as the loss in weight after treatment with H2SO4, and ADF was subtracted from NDF to yield an estimate of hemiceUulose. Silica can affect ADF concentration and that of hemiceUulose when calculated by the difference between levels of ADF fiber and NDF. Silica was not quantified in this study. However, low acid-insoluble ash concentrations in full-fat and defatted rice brans in Experiments 1 (0.32 and 0.51%) and 2 (0.45 and 0.63%) do not suggest high concentrations of silica or a large effect of silica on concentrations of fiber fractions. Voluntary hay intake on Days 10-14 was analyzed as a split-plot in time. Hay intake was not affected by day or the day×treatment interaction; hence, hay intake was averaged over days. Data were analyzed with steer, period and supplement treatment in the model. Differences among means were determined byleast significance difference procedures when the treatment F-test was significant (P<0.10).

2.3. Experiment 3 Six mature beef cows (Angus, Hereford, or Hereford×Angus; 564+ 37.1 kg average trial unshrunk BW), with cannulae in the rumen and duodenum (T-type), were used in a 6 × 6 Latin square with 14 day periods. Cows were housed indoors in 3.1 m×4.3 m pens, with free access to water and trace mineral salt (as in Experiment 1 ). Cows were fed the same sources of hay (long-stemmed) as in Experiment 2 in a 1 : 1 : 1 ratio in equal meals at 07:00 and 19:00 h. Total DM intake was set at approximately 85-90% of ad libitum consumption of unsupplemented hay determined in a 14 day period before the experiment. Controls (no supplement) received (DM basis) 1.5% of initial BW of hay, while hay intake for supplement treatments (FR, C, W, L-DR and H-DR) was 1.1% of BW. Supplement amounts relative to initial BW were 50% of those in Experiment 2 for similar dietary proportions of supplements between experiments. Feedstuffs were offered and sampled as in Experiment 1. Duodenal (275 ml) and fecal digesta were sampled at 07: 00 and 19: 00 h on Day 11, at 08:30 and 14:30 h on Day 12, at 10:00 and 16:00 h on Day 13 and at 11 : 30 and 17: 30 h on Day 14. Duodenal samples, composited on a wet basis, were thoroughly mixed and divided, with one fraction being lyophilized and the other frozen. Fecal samples were subsampled on a wet basis and the composite was lyophilized. Dried composites of duodenal and fecal digesta were ground to pass a 1 mm screen. Ruminal fluid (400 ml) was sampled on Day 11 at 09: 00, 11 : 00, 13: 00, 16: 00, 19:00 and 23:00 h, on Day 12 at 08:30, 14:30 and 21:00 h and on Day 13 at 10:00 h. The pH was measured immediately and samples were strained through eight layers of cheesecloth. Aliquots (200 ml) were composited within cow and

L.A. Forster, Jr. et al. / Animal Feed Science and Technology 47 (1994) 259-275

263

period in a saline (0.9%, w / v ) solution and refrigerated, while another 200 ml aliquot was frozen after adding 7.2 N H2504 (2 ml). Bacterial cells were isolated from the saline solution by differential centrifugation (Merchen and Satter, 1983 ) within 24 h of the last sampling. Isolates were frozen, lyophilized, ground with a mortar and pestle and analyzed for DM, ash, N and nucleic acids (Zinn and Owens, 1986). Ruminal fluid samples were thawed at room temperature and centrifuged at 10 000 X g. Supernatant was analyzed for ammonia N (samples at 07:00, 09:00, 11:00, 13:00 and 16:00 h) by a phenolhypochlorite procedure (Broderick and Kang, 1980) and for volatile fatty acids (VFA; Goetsch and Galyean, 1983) at 11:00 and 19:00 h. Frozen duodenal digesta was thawed and analyzed for DM (55°C, forced-air oven) and ammonia N. Feed and dried digesta composites were analyzed for DM, ash, N and NDF. Hay, full-fat rice bran, wheat middlings and defatted rice bran were analyzed for ADF and lignin; concentrations of ether extract and starch (Streeter et al., 1989 ) were determined for supplements. Duodenal composites were analyzed for nucleic acids. The percentage of microbial N in duodenal digesta was obtained by dividing duodenal digesta nucleic acid concentration by nucleic acids: total N in bacterial cells; microbial OM was derived from bacterial cell N and OM concentrations. Subtracting microbial and ammonia N from total N at the duodenum yielded apparent feed N (non-ammonia, non-microbial). Data were analyzed as described for Experiment 2. Repeated measures were analyzed as a split-plot in time; mean values were analyzed in a reduced model when the treatment × time interaction was not significant (P> 0.10). 2.4. E x p e r i m e n t 4

Ninety-six crossbred (Simmental-sired) beef cattle (approximately 13 months of age), 48 steers and 48 heifers (232 _+2.5 and 232 _+3.3 kg shrunk BW, respectively), were used in an 84 day experiment in the spring at the Beef Substation of the University of Arkansas near Newport. Animals were weighed, dewormed and implanted with 36 nag of zeranol after an overnight period without feed or water. Cattle were allotted to 12 groups by BW (four steers and four heifers per group) to achieve similar mean BW and variation in BW within group. Two groups of cattle (eight per group ) were assigned randomly to each of six supplement treatments. Supplement treatments were as described for Experiment 2 (Control, FR, C, W, L-DR and H-DR), with group-feeding between 09:00 and 10:00 h. Supplement amounts were adjusted every 21 days after weighing and averaged within treatment. A 3: 1 mix of NaC1 and trace minerals (same as in Experiment 2 ) was given daily at 15.7 g per animal daily. Cattle grazed 12 paddocks ( 1.7 ha, silt loam soil) of Kentucky tall fescue (Festuca arundinacea), red and white clover (Trifolium pratense and Trifolium repens, respectively) and bermudagrass. The 12 paddocks were split into two subgroups; each hosted one group of cattle from a treatment. Cattle groups were

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rotated to different paddocks weekly so that every group grazed one of the six paddocks in a subgroup for 7 days during the first 42 days of the study. Cattle groups grazed the other paddocks on Days 43-84. Cattle were weighed (shrunk) on Days 21, 42, 63 and 84. However, on Day 65 one group of steers was killed by lightning. Hence, LWG was analyzed on Days 0-42, 42-84, 0-63 and 0-84. Clipped forage samples (simulated grazed) were obtained from each paddock on Days 0, 21, 42, 63 and 84, dried at 55 °C in a forced-air oven and composited within paddock subgroup. Forage allowance was estimated on Days 0, 21, 42, 63 and 84 with a disc meter (Bransby et al., 1977); 30 readings were taken in each paddock. Calibration (establishment of relation between disc height and forage allowance) was conducted on each day with nine points and clipping of forage at approximately 2.54 cm. Supplement was sampled daily, and composites were formed within 21 day periods. Forage and supplement samples were analyzed for DM, ash, N and NDF. Forage, full-fat rice bran, wheat middlings and defatted rice bran were analyzed for ADF and lignin, and ether extract concentration in supplements was determined. Data were analyzed as a split-plot design; supplement treatment was the main plot and gender the subplot. Group within treatment was used to test for effects of supplement treatment. Differences among treatments were determined by least significance differences procedures when the treatment F-test was significant ( P < 0.08 ).

3. Results and discussion

3. I. Experiment 1 Much of the difference between full-fat and defatted rice bran in DM disappearance during incubations of less than 24 h appeared attributable to 0 h loss (Fig. l ). Although particle size of supplements was not measured, full-fat rice bran particles appeared much smaller than those of defatted rice bran, which may have resulted in greater 0 h disappearance. Rathee and Lohan (1988) also observed greater in situ DM disappearance of full-fat than defatted rice bran in short (e.g. 2 and 4 h) rather than in long incubations (e.g. 24 and 48 h). Predicted potential DM disappearance was 88, 100, 83 and 85% (standard error (SE) 0.7) and rate of disappearance of insoluble but potentially digestible DM was 9.0, 4.9, 16.0 and 7.1% (SE 0.68) for full-fat rice bran, corn, wheat middlings and defatted rice bran, respectively. Small differences between full-fat and defatted rice bran in DM disappearance at 48 and 72 h, relative to the large difference in NDF concentration (Table 1 ), suggests that NDF digestibility was lower for full-fat rice bran. Disappearance at 0 h and rate of disappearance were lowest (P<0.05) for corn, though disappearance at 48 and 72 h was higher ( P < 0.05 ) for corn than for the byproducts. Lower 0 h disappearance and rate of disappearance for corn than for the byproducts imply that factors affecting digesta residence time would have greater impact on extent of digestion of corn.

L.A. Forster, Jr. et al. / Animal Feed Science and Technology 47 (1994) 259-275

265

100~ A

8O 0 t"

I i

6oi Q.

.~_

-'- Corn

o:y

- - Wheat

middlings

- ~ F u l l - f a t RB m Defatted RB

E

i i

0i 0

10

20

30

40

50

60

70

80

Time (h) Fig. 1. In situ (ruminal) dry matter disappearance of corn, wheat middlings, full-fat rice bran (RB) or defatted RB. Pooled SE were 2.72, 1.53, 2.48, 4.43, 1.67, 2.64, 0.58 and 0.68% for 0, 3, 6, 12, 18, 24, 48 and 72 h of incubation, respectively (Experiment 1 ).

3.2. Experiment 2 Lower concentrations of ash, crude protein and NDF in full-fat rice bran than in defatted rice bran correspond to the higher level of ether extract in full-fat rice bran (Table 1 ). Starch was not quantified in Experiment 2; however, levels in Experiment 3 were 28, 71, 35 and 25% for full-fat rice bran, corn, wheat middlings and defatted rice bran, respectively. Conversely, Cardenas Garcia et al. (1992) noted a higher starch concentration in defatted than in full-fat rice polishings (32.5 vs. 25.8%). Supplement OM comprised 24, 19, 25, 21 and 30% of OM intake for FR, C, W, L-DR and H-DR, respectively (Table 2). Depressions in hay OM intake with supplementation were 112, 73, 83, 69 and 87% of supplement OM intake for FR, C, W, L-DR and H-DR, respectively. Similarly, total intake of a grass hay-based diet by adult sheep was not markedly affected by supplementation with 68, 137 or 203 g of rice polishings (Cardenas Garcia et al., 1993). In our experiment, hay OM intake ranked (P<0.05): Control>C and L-DR>FR, W and H-DR. Organic matter digestibility was increased (P< 0.05 ), relative to Control, only by C and W. NDF digestibility was depressed (P< 0.05 ) by FR and H-DR but was not altered (P>0.10) by other supplement treatments. Digestible OM intake was increased by C (P< 0.05) and W (P< 0.05 ).

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Table 1 Feed composition (Experiments 2 and 3) Constituent (% of dry matter) a Feedstuff Experiment 2 Alfalfa Orchardgrass Bermudagrass Hay average b Full-fat ricebran Corn

Wheat middlings Defatted rice bran Experiment 3 Alfalfa Orchardgrass Bermudagrass Hay average b FuU-fat rice bran Corn

Wheat middlings Defatted rice bran

Ash

CP

NDF

ADF

ADL

11.3 9.3 7.0 9.3 12.8 2.9 6.1 17.7

19.0 16.4 11.5 15.9 15.6 9.8 16.1 20.2

46.9 62.6 77.6 61.2 23.6 16.5 38.1 37.9

32.7 33.4 33.1 . 7.7 . 9.6 11.0

7.5 4.9 5.6

10.7 12.0 10.7 11.2 13.2 3.2 7.7 17.7

18.5 16.5 12.0 15.6 15.3 9.5 17.0 20.4

44.8 59.4 75.4 60.3 16.2 9.7 32.8 30.2

32.0 31.8 32.4 . 7.0 . 10.2 11.7

25.3 27.8 28.1

. .

Cellulose Hemicellulose Ether extract

.

.

3.4 . 3.6 5.0

5.0 . 7.0 6.9

7.4 4.7 5.3

24.1 26.5 26.3

.

. 3.1

.

. 3.8 4.5

28.4 26.9

. 4.3 . 6.8 7.1

14.3 29.4 43.2 . 15.9

12.8 27.6 43.0 . 16.6 27.8 26.2

20.6 2.7 3.0 2.7

-

19.3 2.7 3.1 3.0

~CP, crude protein; NDF, neutral detergent fiber; ADF, acid detergent fiber; ADL, acid detergent

lignin. bBased on actual intakes of alfalfa, orchardgrass and bermudagrass hay mixture.

Assuming that supplement treatments did not affect hay NDF digestibility, supplement NDF digestibility was 23, 67, 43, 41 and 39% for FR, C, W, L-DR and H-DR, respectively. Thus, in accordance with results of Experiment 1, digestibility of NDF in full-fat dee bran may have been lower than for defatted dee bran. Conversely, oil in full-fat dee bran (5% of total DM intake with FR) may have impaired forage NDF digestibility. Similarly, Moran ( 1983 ) markedly depressed crude fiber digestibility in 2-3-year-old cattle by supplementing elephant grass with 1.2-4.8 kg office bran. Fatty acids in rice oil are composed of approximately 16% palmitic, 42% oleic and 39% linoleic acids (Warren and Farrell, 1990), and unsaturated fatty acids depress ruminal fiber digestibility more than saturated fatty acids (Harfoot et al., 1974; Jenkins and Palmquist, 1982; Chalupa et al., 1986). Triglycerides in unstabilized full-fat rice bran are hydrolyzed during storage (Juliano, 1985 ), and rice brans were obtained at one time a few weeks before trial initiation. Therefore, most fatty acids probably were unesterified. Free fatty acids have greater effects on ruminal microbial activity than triglycerides (Palmquist and Jenkins, 1980; Jenkins and Palmquist, 1982 ). N digestibility was depressed (P<0.05) by C and increased (P<0.05) by W, whereas measures for FR, L-DR and H-DR were similar (P>0.10) to Control (Table 2 ). In part, the depression in N digestibility with C could have related to incomplete ruminal fermentation of corn OM which elevated hindgut fermenta-

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267

Table 2 Intake and digestion in Holstein steer calves consuming hay and different supplements (Experiment 2)

Treatmenta Item

Control

Organic matter Intake ( k g p e r d a y ) Hay Supplement Total Digestion % kg

per day

Neutral detergent fiber Intake ( k g p e r d a y ) Digestion % kg

per day

Nitrogen Intake (g per day) Digestion %

C

W

L-DR

H-DR

SE

5.65 d

4.14 b

4.80 ¢

4.41 b

4.77 c

4.13 b

0.111

5.65 ~

1.34 5.48 b

1.15 5.96 ~

1.49 5.90 ~

1.26 6.03 d

1.73 5 . 8 6 Cd

0.127

52.0 b 2.96 b

53.9 ~ 2.98 b

55.7 c 3.35 ~

56.1 c 3.32 c

51.9 b 3.17 ~

3.83 e

3.16 b

3.43 c

53.3 ~ 2.05 a

49.5 b 1.47 b

53.7 c 1.86 c

158 b

g per day

FR

58.2 ~ 92 m

aFR, full-fat rice bran; C, corn; W, ted r i c e b r a n .

155 b 56.8 ~ 8 9 ~¢

154 b 52.7 b 83 b

3.59 ~" 51.4 ~ 1.85 ~

165 b 59.8 d 9 9 a~

3.81 d~ 50.9 ~ 1.96 ~d

3.11 b~

0.82 0.088

3 . 5 7 cd

0.086

52.5 b

49.8 b 1.79 ~

1.13 0.062

184 c

185 c

3.6

55.9 ¢ 104 ~

55.5 ~ 104 e

1.05 2.8

wheat middlings; L-DR, low-defatted rice bran; H-DR, high-defat-

bx'nXMeans in a row without a common superscript differ ( P < 0 . 0 5 ).

tion and fecal excretion of microbial N. Higher N digestibility for W than for Control probably reflects rapid and extensive ruminal digestibility of protein and non-protein OM in wheat middlings (Galloway et al., 1991 ). Total tract availability of N in full-fat and defatted rice bran appeared similar, and digestibility of N in defatted rice bran was not altered by level of supplementation. 3.3. Experiment 3 The NDF concentration in supplemental feedstuffs was slightly lower than in Experiment 2 (Table 1 ). Reasons for these differences are not apparent because feedstuffs were obtained at the same time and from the same sources. Lower ( P < 0.05 ) ruminal pH for FR than for Control cannot be explained by VFA concentrations (Table 3), although the difference in pH was probably less than necessary to markedly alter ruminal microbial degradation or growth. Ruminal ammonia N concentration was affected by a time × treatment interaction ( P < 0.08; Fig. 2). Factors responsible for the interaction include a lower

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Table 3

Ruminal digesta characteristics in beef cows consuming hay and differing supplements ( E x p e r i m e n t

3) TreatmenP Item pH

Volatilefatty acids Total ( m M ) Isobutyrate (mol per 100 m o l ) Butyrate (mol per 100 m o l ) Acetate: propionate Acetate (mol per 100 mol) ll:00h

19:00 h Propionate (tool per 100 m o l ) ll:00h 19:00h

Isovalerate (tool per 100 m o l ) 11:00 h 19:00h

Valerate (mol per 100 m o l ) 11:00 h 19:00 h

Control

FR

C

W

6.69 ¢

6.54 b

6.66 ~

6.63 ~

82.8 1.46 7.8 b 4.06 *

80.4 1.36 9.8 a 3.69 b

84.0 1.43 10.6 e 4.00 ac

85.7 1.51 10.9 e 4.09 ~

71.7 * 70.60

68.0 b 68.7 ~

69.3 ~ 68.1 b

17.4 b 17.7 ¢

18.80 18.3 ~

17.1 b 17.3 c

L-DR 6.67 c

H-DR

SE

6.62 ~

0.032

79.5 1.55 8.8 ¢ 3.89 *°

82.1 1.65 9.5 °~ 3.80 ~

2.59 0.084 0.27 0.053

68.1 b 68.8 ~

69.80 69.5 °a

68.6 ~ 68.3 ~

0.33 0.40

17.3 b 16.3 b

18.1 c 17.7 c

18.2 c 17.8 ¢

0.17 0.26

0.84 b¢ 1.46

0.85 ~ 1.43

1.00 de 1.50

1.10 * 1.56

0.78 b 1.59

0.94 °a 1.72

0.045 0.088

0.99 ~ 0.85 ~

0.98 b 0.65 b

0.92 b 0.71 b

1.29 d 0.80 b

0.94 b 0.80 b

1.07 c 1.03 c

0.028 0.078

aiR, full-fat rice bran ; C, corn; W, wheat middlings; L-DR, low-defatted rice bran; H-DR, high-defatted rice bran. b,*.°,eMeans in a row without a common superscript differ ( P < 0.05).

difference between C and other treatments at 09: 00 h than at other times, a decrease from 13:00 to 16:00 h for FR compared with increases for other treatments, and less of a decline from 09: 00 to 11 :00 h for FR than for other treatments. Generally, the pattern of change in ruminal ammonia N concentration with time after feeding was similar among treatments. Ammonia N concentration corresponded to differences among treatments in N intake in most cases, although the peak level for W was similar to that for H-DR despite N intake being considerably greater for H-DR. The concentration of total VFA and molar proportion of isobutyrate in ruminal fluid were similar (P> 0.10) among treatments (Table 3 ). All supplement treatments increased ( P < 0.05 ) the molar proportion ofbutyrate relative to Control, and greatest (P<0.05) changes were with C and W. Limited supplementation with corn has increased the molar proportion of butyrate in other instances as well (Grigsby et al., 1993). Acetate:propionate was decreased (P< 0.05 ) relative to Control by FR and defatted rice bran treatments, and the change was greater ( P < 0.05) for FR than for L-DR. Molar proportions of acetate, propionate, isovalerate and valerate were affected by treatment × sampling time interactions (P< 0.10). The effect of FR on the molar proportion of acetate was relatively greater at 11 :00 h than at 19: 00 h.

L.A. Forster, Jr. et al. / Animal Feed Science and Technology 47 (1994) 259-275

25

Corn

~- Wheat

-x- F u l l - f a t R B

269

middlings

~

Low-defatted RB

-~

Control

A

.J

~- High-defatted

E 20

RB

o o 03

E c o~

2

*'-10 c cO

E E

5

07.00

09.00

11.00

13.00

16.00

Time (h) Fig. 2. Ruminal ammonia nitrogen concentration in cows supplemented with corn, wheat middlings, full-fat rice bran (RB), low-defatted RB or high-defatted RB. Pooled SE were 0.79, 1.49, 0.86, 0.59 and 1.11 mg per 100 ml at 07: 00, 09: 00, 11 : 00, 13: 00 and 16: 00 h, respectively (Experiment 3 ).

The molar proportion of propionate was increased by FR and defatted rice bran treatments at 11 : 00 h but not at 19: 00 h. Effects of supplement treatments on both acetate and propionate molar proportions contributed to effects of FR and DR on acetate: propionate. Factors responsible for effects of FR and defatted rice bran treatments on acetate: propionate compared with the absence of change with C and W are unclear. However, low-level supplementation with corn did not alter acetate: propionate in ruminal fluid when butyrate was elevated (Grigsby et al., 1993 ). For FR, added oil might have depressed the number of protozoa in the rumen which decreased acetate: propionate (Jouany et al., 1988). Perhaps differences between wheat middlings and defatted rice bran in rate of ruminal starch degradation affected microbial VFA production. Supplement OM comprised 28, 23, 30, 28 and 35% of total OM intake for FR, C, W, L-DR and H-DR, respectively. Duodenal microbial OM flow was increased (P<0.05) by FR and W and greater (P<0.05) for W than for FR; however, microbial efficiency was similar ( P > 0.10) among treatments (Table 4). Duodenal feed OM flow was lower ( P < 0.05 ) and true ruminal OM digestibility was higher ( P < 0.05 ) for W than for Control. Postruminal OM digestibility was similar (P>0.10) among treatments; total tract OM digestibility was higher ( P < 0.05 ) with than without supplements and similar (P> 0.10) among supple-

270

L.A. Forster, Jr. et aL / Animal Feed Science and Technology 47 (1994) 259-275

Table 4 Organic matter and neutral detergent fiber digestibilities by beef cows consuming hay and different supplements (Experiment 3) Treatment" Item

Organic matter Intake (kg per day) Duodenal (kg per d a y ) Total Microbial

Feed Fecal (kg per day) Digestibility ( % ) Apparent ruminal True rnminal

Postrnminal Total tract Neutral detergent fiber I n t a k e ( kg per day) Duodenal (kg per day) Fecal ( kg per day) Digestibility (%) Ruminal Postrnminal Total tract

Control

FR

C

W

L-DR

H-DR

7.30

7.10

6.82

7.42

7.02

7.72

3.97 0.73 ~ 3.24 c 3.19 e

4.23 0.91 d 3.32 ¢ 2.86 ca

3.79 0.81 ~ 2.99 ~ 2.61 b

3.82 1.05 c 2.77 b 2.84 ca

3.43 0.65 b 2.78 ~ 2.71 t~

4.04 0.77 ~ 3.27 ~ 2.90 d

45.0 55.1 b 11.2 56.2 b

4.95 g 2.00 d 2.13 ~ 59.4 - 2.4 57.0

41.4 53.9 b 18.8 60.2 c

3.85 c 1.81 ~ 1.82 c 53.5 - 0.1 53.4

44.0 56.0 b 17.5 61.6 ~

3.64 b 1.56 b 1.66 b 57.1 - 2.9 54.2

48.3 62.4 ¢ 13.7 62.0 c

4.30 e 1.94 d 1.97 d 55.0 - 0.5 54.6

50.8 60.1 ~ 10.8 61.6 ¢

4.18 d 1.67 ~ 1.76 ~ 59.7 - 1.1 58.0

47.4 57.4 ~ 14.8 62.3 ~

4.43 f 1.91 d 1.88 ~ 56.8 0.4 57.1

SE

0.192 0.049 0.158 0.076 2.47 2.11 2.30 1.02

0.043 0.098 0.055 2.10 2.22 1.31

"FR, full-fat rice bran; C, corn; W, wheat middlings; L-DR, low-defatted rice bran; H-DR, high-defatted rice bran. b,c,d,e,f~Means in a row without a common superscript differ ( P < 0.05 ).

ment treatments. Digestibilities of NDF were similar (P>0.10) among treatments. Restricted feed intake probably allowed more thorough digestibility of supplement and forage and minimized adverse effects of supplements on forage digestibility compared with ad libitum intake in Experiment 2. Duodenal flow of microbial N and true ruminal N digestibility were increased (P< 0.05 ) by W but were not affected (P> 0.10) by other supplement treatments (Table 5 ). Cardenas Garcia et al. ( 1993 ) depressed microbial protein supply in adult sheep by supplementing a grass hay-based diet with 68, 137 or 203 g office polishings. Assuming that supplement treatments in our experiment did not alter ruminal digestibility of forage N, ruminal disappearance of supplement N was 57, 68, 119, 80 and 71% for FR, C, W, L-DR and H-DR, respectively. The estimate for W indicates thorough ruminal digestibility of protein in wheat middlings and that forage protein degradation may have been higher for W than for Control. Overall, ruminal degradation of protein in defatted rice bran appeared higher than for full-fat rice bran. In contrast, Rathee and Lohan ( 1988 ) observed similar in situ N disappearance at 12, 24 and 48 h of ruminal incubation for rice

L.A. Forster, Jr. et aL /Animal Feed Science and Technology 4 7 (1994) 259-2 75

271

Table 5 Nitrogen intake and disappearance and microbial efficiency in beef cows consuming hay and different supplements (Experiment 3 ) TreatmenP Item

Control

FR

C

W

L-DR

H-DR

SE

199.3

170.1

211.9

218.7

246.4

2.58

75.5 de 10.90 66.8 d~

178.2 e 89.0 ¢d 77.7 de 11.6 d 66.5 de

146.6 cd 77.3 c 62.4 d 7.0 ~ 63.0 d

155.6 cdc 104.0 d 41.3 ~ 10.3 d 64.6 de

143.6 c 65.0 c 68.9 dc 9.7 cd 70.6 e

172.9 de 78.4 c 83.7 ¢ 10.8 d 77.2 f

8.98 8.18 6.77 0.97 2.09

20.6 cd 62.5 c 46.2 "f 66.8 ¢ 19.7

10.9 ~ 60.2 ¢ 55.5 f 66.4" 23.4

13.2 c 63.0 c 48.7 ef 61.9 f 20.7

25.8 de 79.6 d 43.2 °~ 69.0 e 22.6

33.7 e 68.1 ¢ 33.6 d 67.2 e 16.6

29.3 d~ 65.7 ~ 38.7 de 68.0 ~ 18.2

3.81 3.24 3.81 0.96 2.13

Nitrogen intake (g per day) 204.8 Duodenal nitrogen (g per d a y ) Total 160.7 ode Microbial 74.3 c Feed

Ammonia Fecal nitrogen (g per d a y ) Nitrogen disappearance ( % ) Apparent ruminal True ruminal

Postruminal Total tract Microbial efficiencyb

"FR, full-fat rice b r a n ; C, c o r n ; W, wheat middlings; L-DR, low-defatted rice bran; H - D R , h i g h - d e f a t t e d rice bran. bGrams of microbial nitrogen per k g o f organic matter truly fermented. c.d'e.fMeans i n a row without a common superscipt d i f f e r ( P < 0.05 ).

polishings and rice bran deoiled by a continuous process. Rice bran deoiled by a batch-type method was lower than that for full-fat rice polishings at all incubations. In our experiment, only postruminal N digestibility for L-DR differed ( P < 0.05 ) from Control. Total tract N digestibility was lower ( P < 0.05) for C than for other treatments, similar to results in Experiment 2.

3.4. Experiment 4 The concentration of NDF in clipped forage samples on Days 42, 63 and 84 (Table 6 ) resembled forage consumed in Experiments 2 and 3. Supplement composition was similar to other experiments as well. Forage allowance was high throughout the experiment, increasing from Day 0 to Day 63 and declining slightly thereafter. Interactions between gender and supplement treatment were non-significant ( P > 0.10)(Table 7 ). LWG was high because of high forage quality and allowance, and potential to increase performance by supplementation appeared limited. LWG on Days 0-42, 43-84 and 0-63 was similar ( P > 0 . 1 0 ) among treatments. However, LWG on Days 0-84 was increased by FR ( P < 0 . 0 5 ) and C

(P<0.09). The increase in LWG on Days 0-84 with FR was not in accordance with no change in digestible OM intake in Experiment 2. Greatest increases in digestible

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272

Table 6 Forage and hay composition and forage allowance (Experiment 4 ) Constituent (% of dry matter) a Item

Ash

CP

NDF ADF ADL Cellulose HemiEther cellulose extract

31.3 23.1 17.5 15.1 14.5

48.2 47.3 59.0 59.6 60.2

Forage allowance (kg DM per animal)

Clipped forage samples Day0 Day21 Day42 Day63 Day84

11.5 9.7 8.2 9.6 9.1

Full-fat rice bran Corn Wheatmiddlings Defatted rice bran

12.1 15.9 19.0 1.5 9.5 10.6 5.4 17.7 35.3 16.7 20.5 32.6

22.6 25.8 34.6 36.5 35.9

2.4 2.5 3.9 4.5 4.8

19.2 22.3 29.5 29.8 28.7

25.7 21.5 24.4 23.1 24.3

-

7.7 2.5 . . . 11.0 3.5 11.6 4.1

5.0 . 7.8 7.5

11.3

18.6 1.6 1.8 1.9

24.3 21.0

174 219 276 390 318

aCP, crude protein; NDF, neutral detergent fiber; ADF, acid detergent fiber; ADL, acid detergent lignin; DM, dry matter. Table 7 Live weight and live weight gain of grazing beef steers and heifers receiving different supplements (Experiment 4) Treatmenta

Item

Control

FR

C

W

L-DR

H-DR

SE

Initialliveweight (kg)

232.3

232.7

232.7

231.7

231.5

231.2

0.55

Live weight gain (kg per day) Days Days Days Days

0-42 43-84 0-63 0-84

1.00 1.11 1.01 1.06 ~

1.13 1.30 1.20 1.18 d

1.05 1.21 I. 16 1.14 ~

0.91 1.05 0.96 0.99 b

1.01 1.04 1.06 1.04 b

0.98 0.95 0.96 0.98 b

0.077 0.063 0.065 0.027

aFR, full-fat rice bran; C, corn; W, wheat middlings; L-DR, low-defatted rice bran; H-DR, high-defatted rice bran. b'c'dMeans in a row without a common superscript differ ( P < 0.05).

OM intake in Experiment 2 were with C and W, yet in Experiment 4 W did not improve LWG. Likewise, supplemental wheat increased digestible OM intake by steers fed bermudagrass hay but did not alter LWG by steers grazing bermudagrass, although increases in both digestible OM intake with hay and LWG during grazing were observed with supplemental corn (Galloway et al., 1993). It was postulated that wheat supplementation of grazing steers altered ruminal conditions such as pH more than in steers consuming dry hay because of differing alterations of saliva flow relative to OM being fermented. For FR, results in Experiment 3 suggest that acetate:propionate might have been decreased. Such a change could have contributed to increased LWG with

L.A. Forster, Jr. et al. / Animal Feed Science and Technology 47 (1994) 259-275

273

FR. However, LWG was not affected by L-DR despite decreased acetate:propionate in Experiment 3.

4. Summary Supplementing growing steers consuming moderate- to high-quality forage with 0.8% of BW of full-fat rice bran did not increase digestible OM intake, whereas supplementing with a comparable amount of digestible energy from corn or wheat middlings did. Defatted rice bran, added to provide amounts of DM or digestible energy similar to FR, did not significantly increase digestible OM intake. Full-fat rice bran depressed forage intake per unit of supplement intake more than defatted rice bran supplements. Digestibility of NDF of full-fat rice bran may have been lower than for defatted rice bran, and/or oil in full-fat rice bran depressed forage NDF digestibility. Full-fat and defatted rice bran treatments, particularly the former, decreased acetate:propionate, whereas C and W did not. Ruminal digestibility of protein in defatted rice bran appeared high relative to that of protein in full-fat rice bran and corn, and microbial efficiency did not differ among treatments. With moderate= to high=quality forage grazed by growing beef steers and heifers, supplementation with 0.80% of BW of full-fat rice bran or 0.62% of BW of corn increased LWG slightly. Conversely, supplementation with defatted rice bran at 0.80 or 1.10% of BW or with 0.81% of BW of wheat middlings did not affect LWG. These results indicate that in some situations intake and digestive conditions for cattle supplemented with defatted rice bran may be similar to, or more favorable than, those with full-fat rice bran, suggesting higher performance for defatted rice bran. Conversely, in other instances performance may be greater for full-fat rice bran. Furthermore, differences between rice brans and other supplements such as corn and wheat middlings may vary with experimental conditions such as forage characteristics as well.

5. Acknowledgements Appreciation is expressed to Riceland Foods and Arkansas Science and Technology Authority for partial financial support.

6. References Association of Official Analytical Chemists, 1984. Official Methods of Analysis, 14th edn. Association of Official Analytical Chemists, Washington, DC, pp. 152-157. Belyea, R.L, Steevens, B.J., Restrepo, R.J. and Clubb, A.P., 1989. Variation in composition of byproduct feeds. J. Dairy Sci., 72: 2339~2345.

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