Feeding value and fermentation characteristics of ensiled sugar beet wet distillers for fattening Holstein steers

Abstract

Sugar beet wet distillers juice with solubles (SBWDJS) are disposed to aerobic spoilage when stored for a prolonged period. The objectives of the present study were to evaluate the fermentation characteristics of ensiled SBWDJS, as well as their feeding impact on the metabolic profiles and the growth performance in fattening Holstein steers. Ensiled blends containing SBWDJS were prepared either with Amylomyces rouxii inoculation (AS) or without (US). The silos were analysed on days 0, 7, 14, 28 and 42. As expected, silage lactic acid (LA) concentrations were elevated in the AS treatment compared with the US treatment. Daily gain and final bodyweight values were similar between treatments. Statistically, blood lactic acid concentrations were lowest from AS-based diet-fed steers and highest from control-fed steers. Collectively, SBWDJS can be effectively ensiled with or without A. rouxii and used as feedstuff for fattening Holstein steers.

Keywords:

• Amylomyces rouxii
• beef
• silage
• sugar beet
• wet distillers

Introduction

Recently, the increase in oil prices has sparked an interest in renewable energy alternatives, resulting in an increase in the production of bioethanol from various grain sources (Lodge et al. 1997). Highly productive crops, such as corn and other grains, are the major determinants of profitability in the livestock production industry (Lawrence et al. 2011); therefore, the search for new feeding sources has become critical for animal producers. Sugar beets are mainly used for sugar production, but are also used as a raw material for ethanol distillation. This distillation process results in the production of sugar beet wet distillers juice with solubles (SBWDJS). Wet distillers are considered to be valuable feedstuffs for raising ruminant animals and maintaining/improving their growth performance (Klopfenstein et al. 2008). However, the spoilage of wet distillers often occurs during storage. Thus, ensiling of this material was suggested by Abrams et al. (1983), who proposed that wet distillers could be ensiled and stored for long periods of time while still retaining the same efficacy for ruminant feeding purposes.

Inoculants are the most common biological additives used during the ensiling process, resulting in a rapid decrease in pH, higher lactate:acetate ratios and an improvement in dry matter (DM) recovery (Weinberg & Muck 1996). However, recent studies (Oda et al. 2002; Okine et al. 2007) have investigated the use of fungal or aerobic inoculants that target the first stages of the ensiling process. Amylomyces is a monotypic genus of fungus that contains only a single species, Amylomyces rouxii, which is identified by its formation of rhizoids, stolons and black-pigmented sporangia (Saito et al. 2004). This fungus contains pectinase and lactose dehydrogenase enzymes, which enable aerobic production of lactic acid (LA) from various types of complex structural carbohydrates (Okine et al. 2007). Therefore, the addition of A. rouxii may have a value in enhancing silage fermentation qualities.

To our knowledge, no data concerning ensiled SBWDJS have been published previously. Therefore, in the present study, we evaluated the fermentation characteristics of SBWDJS ensiled with wheat straw (WS) and wheat bran (WB) in the presence and absence of A. rouxii, as well as the impact of feeding the ensiled feedstuff on the growth performance and blood constituents of Holstein steers.

Materials and methods

Experimental protocols and animal care were conducted according to the Guide for the Care and Use of Experimental Animals at the Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan.

Ensiling experiment

Sugar beet wet distillers juice with solubles was delivered in the morning and ensiled with WS and WB on the same day. Two treatment blends were evaluated for ensilability characteristics. The first treatment blend consisted of 475 g/kg SBWDJS, 355 g/kg WS and 170 g/kg WB without inoculation (US), and the second treatment blend consisted of 475 g/kg SBWDJS, 355 g/kg WS and 150 g/kg WB and 20 g/kg A. rouxii (AS), both on a fresh matter basis. Amylomyces rouxii strain CBS 438.76^T (Accession no. AY238888) is a commercial product cultured on WB and was purchased from the Snow Brand Seed Co. (Sapporo, Japan). The inoculant was initially added to SBWDJS and then mixed for 3 min before ensiling. For each silo bag, a fixed amount of WS was mixed with WB and SBWDJS (with or without A. rouxii) for 5 min until the mixture was homogeneous and then placed in the silo bags. All silo bags were packed to a density of 473.8 kg/m³ on a fresh matter basis. Ensiled materials were kept in round silo bags, which were made up of two layers; the inside layer was plastic allowing anaerobic conditions to be maintained. The bags had a width × height of 110 × 110 cm as well as a safe working load of 500 kg and a capacity of 1040 L (FIBC, TEC, Japan). Twelve silo bags were made for each blend, and three silos were sampled on days 7, 14, 28 and 42. Samples from each blend were collected for analysis before ensiling to represent day 0. From each silo bag a total of 9 to 15 samples were taken 15–20 cm below the upper surface of the silage along a W-shaped sample pathway ensuring that each sample was taken from a different horizontal and vertical position. A 0.5 kg composite sample was made from each silo bag, stored at 4 °C and sent directly for analysis. Samples were analysed for changes in nutrient composition and fermentation characteristics.

Steer feeding experiment

Two batches of US and AS silage blends were ensiled for 42 days, and their effects as a feed source were then evaluated in fattening Holstein steers. Twenty-nine Holstein steers (averaging 622.7 ± 23.3 kg of bodyweight (BW) and approximately 16 ± 1 months old) were assigned to one of three treatment diets. The diets were control (total mixed ration [TMR], 11 steers), US silage blend + TMR (USTMR, nine steers) and AS silage blend + TMR (ASTMR, nine steers). The ingredient compositions of each diet are given in Table 1. The control diet comprised 16.6% timothy hay (Phleum pratense) and 83.4% concentrate mixture (DM basis) composed of rolled corn, WB, soybean meal, lucerne pellets, defatted rice bran, calcium carbonate and feed additives. The USTMR diet was composed of 7.7% timothy hay and 15.4% US silage blend with 76.9% concentrate mixture. The ASTMR diet was composed of 7.7% timothy hay, 15.4% AS silage blend and 76.9% concentrate mixture. All diets were designed to be isocaloric and isonitrogenous, according to the Japanese Feeding Standard for Beef Cattle (NARO 2008). Samples of timothy hay, concentrate mixture, US and AS silage blends were taken weekly and then composited for proximate analysis.

Table 1 Ingredient composition for the control, sugar beet wet distillers juice with solubles (SBWDJS) silage blend (USTMR), and SBWDJS inoculated with Amylomyces rouxii silage blend (ASTMR) treatment diets and the chemical composition of individual components, SBWDJS, wheat straw and wheat bran, used to make the silage blends.

	Diets
	Control	USTMR	ASTMR
Ingredients (% of DM)
Timothy hay	16.6	7.7	7.7
US silage	0	15.4	0
AS silage	0	0	15.4
Concentrate (% of concentrate pellet, DM base)	83.4	76.9	76.9
Corn, rolled	65	65	65
Wheat bran	18	18	18
Soybean meal, 48% CP	5	5	5
Lucerne Pellets	5	5	5
Defatted rice bran	5	5	5
Calcium carbonate	1.5	1.5	1.5
Feed additives^1	0.5	0.5	0.5
Chemical composition (g/kg DM, unless stated otherwise)
Items	SBWDJS	Wheat straw	Wheat bran
DM	15.0	884.0	889.0
CP	280.0	152.0	43.0
ADF	117.0	148.0	483.0
NDF	66.0	462.0	777.0
EE	140.0	53.0	19.0
Ash	186.0	59.0	116.0

SBWDJS, sugar beet wet distillers juice with solubles; ADF, acid detergent fibre; CP, crude protein; DM, dry matter; EE, ether extract; NDF, neutral detergent fibre. Control, TMR + timothy hay; USTMR, TMR + blend of 475 g/kg SBWDJS, 355 g/kg wheat straw and 170 g/kg wheat bran; and ASTMR, TMR + blend of 475 g/kg SBWDJS, 355 g/kg wheat straw, 150 g/kg wheat bran and 20 g/kg A. rouxii.

¹ Feed additives: each 1 g contains 1500 IU vitamin A, 150 IU vitamin D3, 2 mg vitamin E 50%, 300 µg of vitamin B1, 300 µg of vitamin B2, 300 µg of vitamin B6, 300 µg of vitamin K3 50%, 218 µg of manganese oxide, 435 µg of ferrous sulphate, 15.5 µg of copper oxide, 138.5 µg of zinc oxide, 2.2 µg of potassium iodide, 0.9 µg of sodium selenite.

Steers were housed in a barn with a metal roof with natural daylight during the experimental period of 43 days preceded by a 7-day adaptation period. Daily intake from each diet was fixed at 10 kg/head day⁻¹ (DM basis). Bodyweight records and blood sampling were taken individually at the beginning of the experiment and then every 2 weeks at 1000 h under the same housing conditions. Two trials of weight measuring were performed for adaptation purposes prior to the experiment. For determination of the metabolic profile, blood samples were collected from the jugular vein in three different tubes. Blood test tubes specified for glucose detection were used (Vacuette, Glucose PO/NaF 4 mL tubes, Venoject®, Terumo, Tokyo, Japan). Air-vacuumed tubes without anticoagulant (Venoject®) were used for serum separation to be assayed for aspartate transaminase (AST), alanine transaminase (ALT), triglycerides cholesterol (T-cho), triglycerides, albumin and urea nitrogen detection. Specified tubes containing 4 mL of 1 N perchloric acid (Venoject®) were used for the detection of LA concentrations. All samples were immediately placed on ice and transferred to the Kishimoto Clinical Laboratory (Obihiro, Hokkaido, Japan) for analysis.

Chemical analysis

Feed chemical composition and fermentation characteristics of silage samples including DM, ash, neutral detergent fibre (NDF), acid detergent fibre (ADF), crude protein (CP), pH, volatile fatty acids (VFA), LA and ammonia were assessed by the Tokachi Nokyoren Research Centre (Obihiro, Hokkaido, Japan) directly after each sampling time. Eighty grams of each silage sample was weighed and placed into a 500 mL sealable container to which was added 320 mL of distilled water. The container was closed and shaken for 6 h at 180 rpm using a horizontal shaker (Moyo 2010). The extracted silage was then filtered through four layers of cheesecloth. Directly after sample preparation, the pH was measured using an electrode pH meter, after it had been calibrated by means of pH 4 and pH 7 buffer solutions. Lactic acid was determined by the colorimetric method of Pryce (1969). Ammonia nitrogen was analysed according to AOAC (2002) using method number 920.03, whereas the VFA analysis was conducted with high-performance liquid chromatography (Siegfried et al. 1984). For proximate analysis, samples were dried for 48 h at 55 °C in a dispatch oven (style V-23, Dispatch Oven Co, Minneapolis, MN, USA) before milling to a particle size of 1 mm (Wiley mill, model 3, Arthur H. Thomas Co, Philadelphia, PA, USA). Dry matter was measured by drying 1 g of the ground sample at 105 °C for 24 h (Undersander et al. 1993). Crude protein was determined with the Kjeldahl method number 954.01 (AOAC 2002). The preparation of the ether extract (EE) was performed with the Soxhlet method to measure total fat content based on AOAC procedure number 920.39 (AOAC 2002). NDF (Van Soest et al. 1991), without the use of α-amylase and not corrected for ash, and ADF (Robertson & Van Soest 1981), without correction for ash, were determined in sequence with the Ankom fibre analysis system (Ankom Technology Corp, Fairport, NY, USA). Ash content was determined with a muffle furnace at 450 °C for 8 h (Undersander et al. 1993).

Metabolic profile test

Biochemical analysis of blood samples were performed by a clinical chemistry automated analyser (Toshiba Medical Systems Co, Tochigi, Japan) to measure the concentrations of glucose, AST, ALT, T-cho, LA, triglycerides, albumin and blood urea nitrogen with specific detection regents (Denka Seiken, Tokyo, Japan).

Statistical analysis

All data were analysed using a mixed model with repeated measures (Mixed procedures, SAS Inst. Inc, Cary, NC) (SAS 2010). This model included treatment, week and treatment × week interaction with week as the repeated term and treatment as the subject. Average daily gain (ADG) was determined by calculating the differences between initial and final time points before dividing by the number of days in the study. Initial and final bodyweight data were analysed using the general linear model procedure in a complete randomised design with treatment as the main effect. Least square means were computed for all targets and were adjusted with Tukey's test for significance. Treatment means were considered statistically different at P < 0.05.

Results

Ensiling experiment

Chemical analysis of silage components revealed that the concentration of DM in SBWDJS was 15 g/kg, and on a DM basis, SBWDJS contained 66 g/kg NDF, 117 g/kg ADF, 280 g/kg CP and 186 g/kg ash (Table 1). Thereafter, the nutrient composition of the prepared silages was examined over the period of the ensiling process (Table 2). The changes in DM content were not significantly different between treatments over the ensiling period. However, CP concentration decreased for both treatments (P = 0.02) with prolonged ensiling period, with no significant effect observed between treatments. No effect of treatment was noticed for EE, ADF and NDF concentrations; however, there was a tendency for ADF and NDF to increase (P = 0.06 and 0.09, respectively) over time for both treatments. No effect of treatment was found for ash content; however, concentrations over the ensiling period tended (P = 0.06) to elevate. As shown in Table 3, the average pH values in the US and AS treatments were recorded over the ensiling period to be 4.5 for both treatments, with no significant effect between the two treatments. The concentrations of ammonia nitrogen (AN) tended to increase with time (P = 0.08) for both blends, with no significant effect between treatment. Lactic acid concentrations were higher in the AS treatment than the US treatment (P = 0.03). Acetic acid (AA) and propionic acid (PA) concentrations were not influenced by treatment or ensiling period.

Table 2 Nutrient chemical composition over time of two ensiled blends, a sugar beet wet distillers juice with solubles (SBWDJS) silage blend without inoculation (US) and with Amylomyces rouxii inoculation (AS) on a dry matter basis.

		Treatment				P value
Items (g/kg)	D of ensiling	US	AS	D mean	SEM	T	D	T × D
DM	0	365.0	382.5	373.8	15.7	0.17	0.12	0.14
	7	342.0	348.8	345.4	15.7
	14	360.5	327.5	344.0	15.7
	28	421.0	350.5	385.8	15.7
	42	401.0	352.5	376.8	15.7
	T mean	352.4	377.9		12.9
CP	0	103.8	112.0	107.9^xy	7.0	0.58	0.04	0.94
	7	111.3	118.5	114.9^xy	7.0
	14	115.5	123.5	119.5^x	7.0
	28	117.5	113.5	115.5^xy	7.0
	42	91.5	98.0	94.8^y	7.0
	T mean	113.1	107.9		6.7
EE	0	33.5	31.3	32.4	3.1	0.92	0.58	0.74
	7	34.5	32.0	33.3	3.1
	14	39.0	31.5	35.3	3.1
	28	33.5	35.5	34.5	3.1
	42	24.8	33.3	29.0	3.1
	T mean	32.7	33.1		2.5
ADF	0	361.8	347.5	354.6	16.1	0.54	0.06	0.37
	7	371.5	332.8	352.1	16.1
	14	361.0	337.3	349.1	16.1
	28	347.5	358.8	353.1	16.1
	42	403.5	399.8	401.6	16.1
	T mean	355.2	369.1		15.5
NDF	0	656.0	639.3	647.6	14.6	0.48	0.09	0.84
	7	646.0	625.0	635.5	14.6
	14	641.3	613.5	627.4	14.6
	28	633.8	644.8	639.3	14.6
	42	684.3	668.3	676.3	14.6
	T mean	638.2	652.3		13.9
Ash	0	90.8	96.0	93.4	4.6	0.32	0.06	0.99
	7	90.3	98.5	94.4	4.6
	14	95.0	102.5	98.8	4.6
	28	94.5	101.2	97.9	4.6
	42	105.8	112.0	108.9	4.6
	T mean	102.1	95.3		4.7

ADF, acid detergent fibre; CP, crude protein; D, day; DM, dry matter; EE, ether extract; NDF, neutral detergent fibre; T, treatment. AS, blend of 475 g/kg SBWDJS, 355 g/kg wheat straw, 150 g/kg wheat bran and 20 g/kg A. rouxii (on an as-fed basis); US, blend of 475 g/kg SBWDJS, 355 g/kg wheat straw and 170 g/kg wheat bran.

^a,b Means in the same row (T mean) with different letters are significantly different (P < 0.05).

^x,y,z Means in the same column (d mean) with different letters are significantly different (P < 0.05).

Table 3 Fermentation characteristics over days of two ensiling blends of for sugar beet wet distillers juice with solubles (SBWDJS) silage blend (US) and SBWDJS inoculated with Amylomyces rouxii silage blend (AS) on a dry matter basis.

		Treatment				P value
Items	D of ensiling	US	AS	D mean	SEM	T	D	T × D
pH	0	4.5	4.5	4.5	0.04	1.00	0.45	0.70
	7	4.5	4.4	4.4	0.04
	14	4.5	4.5	4.5	0.04
	28	4.4	4.5	4.4	0.04
	42	4.5	4.5	4.5	0.04
	T mean	4.5	4.5		0.03
AN (g/kg DM)	0	0.9	1.0	0.9	0.1	0.35	0.08	0.80
	7	1.5	1.3	1.3	0.1
	14	1.5	1.2	1.4	0.1
	28	1.4	1.2	1.3	0.1
	42	1.1	0.9	1.0	0.1
	T mean	1.1	1.3		0.1
LA (g/kg DM)	0	9.7	10.5	10.1	2.8	0.03	0.25	0.29
	7	11.9	15.9	13.9	2.8
	14	8.9	16.1	12.5	2.8
	28	14.4	15.0	14.7	2.8
	42	7.1	7.4	7.3	2.8
	T mean	10.4^b	13.0^a		1.8
AA (g/kg DM)	0	30.6	34.5	32.7	3.4	0.49	0.38	0.44
	7	35.3	36.5	35.9	3.4
	14	34.9	33.7	34.4	3.4
	28	33.9	32.7	33.3	3.4
	42	37.5	35.4	36.5	3.4
	T mean	34.4	34.6		2.2
PA (g/kg DM)	0	4.6	7.2	5.9	1.4	0.33	0.24	0.18
	7	4.5	7.3	5.9	1.4
	14	5.3	5.7	5.5	1.4
	28	5.3	6.1	5.7	1.4
	42	8.5	6.8	8.6	1.4
	T mean	5.6	6.6		0.9

AA, acetic acid; AN, ammonia nitrogen; D, day; LA, lactic acid; PA, propionic acid; T, treatment. AS, blend of 475 g/kg SBWDJS, 355 g/kg wheat straw, 150 g/kg wheat bran and 20 g/kg Amylomyces rouxii (on an as-fed basis); US, blend of 475 g/kg SBWDJS, 355 g/kg wheat straw and 170 g/kg wheat bran.

^a,b Means in the same row (T mean) with different letters are significantly different (P < 0.05).

^x,y,z Means in the same column (day mean) with different letters are significantly different (P < 0.05).

Steer feeding experiment

The analysis of individual ingredients is presented in Table 4, and the TMR chemical analyses of the control, USTMR and ASTMR diets are illustrated in Table 5. The control diet had slightly lower ADF (121 g/kg) concentrations than USTMR (138 g/kg DM) and ASTMR (135 g/kg DM) treatments. The calcium (Ca), phosphorus (P), magnesium (Mg) and potassium (K) mineral concentrations did not vary between the diets. The metabolic profile of the steers is presented in Table 6. The LA concentrations from ASTMR fed steers were significantly lower (P = 0.01) than those from steers fed the control diet. However, ALT concentrations were significantly (P = 0.02) lower in USTMR than those from steers fed the control diets. Triglycerides cholesterol blood concentrations were lowest in steers fed the USTMR diet and highest in steers fed the ASTMR diet (P = 0.02). However, blood albumin concentrations were higher (P < 0.01) in control and ASTMR diets than in steers fed the USTMR. Blood urea nitrogen concentrations were found to be higher (P < 0.01) in the ASTMR fed steers than the control and USTMR, which might imply higher ruminal nitrogen to energy levels. However, blood glucose, AST and triglycerides concentrations were not influenced by the treatments over the period of the study. Consistently, the ADG values were comparable among treatments throughout the period of the experiment (Table 7). No treatments effect was found for total average daily gain (TADG) values; however, a tendency (P = 0.09) for the USTMR diet to have higher TADG values than the control and ASTMR treatment diets was noticed.

Table 4 Chemical composition of individual components of the concentrate, timothy hay, US silage blend and AS silage blend used to make the total mixed rations for each treatment.

Items (g/kg DM, unless stated otherwise)	Concentrate	Timothy hay	US	AS
DM	860.0	843.0	426.0	430.0
CP	148.0	69.0	103.0	101.0
ADF	66.0	353.0	402.0	396.0
NDF	191.0	408.0	655.0	654.0
NFC^1	606.0	110.0	126.0	125.0
EE	25.0	35.0	25.1	34.0
Ash	49.0	132.0	116.0	106.0
Ca	9.0	4.6	3.4	3.9
P	5.4	1.7	4.9	4.9
Mg	2.6	1.7	2.5	2.5
K	7.7	13.6	11.3	12.4
NEm (MJ/kg)^1	8.2	2.5	3.9	4.3
NEg (MJ/kg)^1	5.5	0.3	1.6	1.9

ADF, acid detergent fibre; Ca, calcium; CP, crude protein; DM, dry matter; EE, ether extract; K, potassium; NDF, neutral detergent fibre; NFC, non-fibre carbohydrate; Mg, magnesium; NE_m, net energy for maintenance; NE_g, net energy for growth P, phosphorus. AS, blend of 475 g/kg SBWDJS, 355 g/kg wheat straw, 150 g/kg wheat bran and 20 g/kg A. rouxii; US, blend of 475 g/kg sugar beet wet distillers juice with solubles (SBWDJS), 355 g/kg wheat straw and 170 g/kg wheat bran.

¹ Calculated using the NRC (2001) computer model.

Table 5 Nutrient composition of control, USTMR, TMR + sugar beet wet distillers juice with solubles (SBWDJS) silage blend, and ASTMR, TMR + SBWDJS inoculated with Amylomyces rouxii silage blend treatment diets based on analysis of components

	Treatment diets
Items (g/kg DM, unless stated otherwise)	Control	USTMR	ASTMR
DM	863.0	862.0	863.0
CP	131.0	128.0	130.0
ADF	121.0	138.0	135.0
NDF	409.0	401.0	428.0
NFC^1	410.0	421.0	394.0
EE	33.0	31.0	32.0
Ash	51.0	51.0	50.0
Ca	7.3	6.3	6.9
P	4.7	4.3	4.7
Mg	2.0	1.9	2.1
K	8.9	8.7	9.0
NEm (MJ/kg)^1	7.1	6.8	6.9
NEg (MJ/kg)^1	4.6	4.3	4.4

ADF, acid detergent fibre; Ca, calcium; CP, crude protein; DM, dry matter; EE, ether extract; K, potassium; Mg, magnesium; NE_m, net energy for maintenance; NE_g, net energy for growth; NDF, neutral detergent fibre; NFC, non-fibre carbohydrate; P, phosphorus. ASTMR, TMR + blend of 475 g/kg SBWDJS, 355 g/kg wheat straw, 150 g/kg wheat bran and 20 g/kg Amylomyces rouxii; Control, TMR + timothy hay; USTMR, TMR + blend of 475 g/kg SBWDJS, 355 g/kg wheat straw and 170 g/kg wheat bran.

¹ Calculated using the NRC (2001) computer model.

Table 6 Blood composition of Holstein steers steers fed TMR with timothy hay (control), TMR with sugar beet wet distillers juice with solubles (SBWDJS) silage blend (USTMR), and TMR with SBWDJS inoculated with Amylomyces rouxii silage blend (ASTMR) treatment diets.

		Treatment					P value
Items	Day of experiment	Control	USTMR	ASTMR	D mean	SEM	T	D	T × D
Lactic acid (mg/dL)	0	24.6	25.9	16.2	22.2	2.5	0.01	0.57	0.77
	14	23.8	21.5	16.8	20.7	2.5
	28	19.7	17.4	17.2	18.0	2.5
	43	27.8	20.5	14.8	21.1	2.5
	T mean	24.0^a	21.3^ab	16.2^b		2.1
Glucose (mg/dL)	0	74.6	76.9	76.2	75.9^y	1.4	0.49	0.02	0.15
	14	74.5	78.6	85.4	79.4^xy	1.4
	28	76.6	78.7	76.1	77.2^xy	1.4
	43	84.5	81.1	81.3	82.4^x	1.4
	T mean	77.7	78.8	79.8		1.3
AST (IU/L)	0	59.3	58.3	56.4	58.1^xy	2.2	0.08	<0.01	0.32
	14	50.1	54.1	51.9	52.1^z	2.2
	28	51.2	60.3	59.2	56.8^yz	2.2
	43	60.2	63.5	65.7	63.1^x	2.2
	T mean	55.2	59.0	58.3		2.1
ALT (IU/L)	0	26.5	23.5	23.0	24.4^x	1.4	0.02	<0.01	0.67
	14	21.5	21.3	20.8	21.2^xy	1.4
	28	22.2	18.1	19.1	19.8^y	1.4
	43	22.8	20.4	22.3	21.8^xy	1.4
	T mean	23.3^a	20.8^b	21.3^ab		1.3
T-cho (mg/dL)	0	117.1	113.4	127.2	119.3^y	4.5	0.02	0.02	0.99
	14	121.8	119.4	135.8	125.7^xy	4.5
	28	115.6	113.9	133.6	121.0^y	4.5
	43	136.3	133.6	151.3	140.4^x	4.5
	T mean	122.7^ab	120.1^b	137.0^a		4.3
Triglycerides (mg/dL)	0	15.8	15.7	13.4	14.9^x	0.8	0.09	<0.01	0.51
	14	14.2	13.2	12.7	13.4^x	0.8
	28	15.1	11.3	11.5	12.7^x	0.8
	43	7.1	6.7	7.4	7.1^y	0.8
	T mean	13.0	11.7	11.3		0.6
Albumin (g/dL)	0	3.6	3.6	3.6	3.5^x	0.1	<0.01	<0.01	0.09
	14	4.0	3.9	4.0	4.0^x	0.1
	28	3.9	3.9	4.0	3.9^x	0.1
	43	3.7	3.5	3.8	3.6^y	0.1
	T mean	3.8^a	3.7^b	3.9^a		0.1
UN (mg/dL)	0	12.1	11.1	13.6	12.3^y	0.4	<0.01	<0.01	0.25
	14	12.2	12.5	13.6	12.8^y	0.4
	28	11.0	12.4	14.1	12.5^y	0.4
	43	15.1	13.9	15.9	14.9^x	0.4
	T mean	12.6^b	12.5^b	14.3^a		0.3

ALT, alanine transaminase; AST, aspartate transaminase; D, day; T, treatment; T-cho, triglycerides cholesterol; UN, urea nitrogen.

ASTMR, TMR + blend of 475 g/kg SBWDJS, 355 g/kg wheat straw, 150 g/kg wheat bran and 20 g/kg Amylomyces rouxii; Control, TMR + timothy hay; USTMR, TMR + blend of 475 g/kg sugar beet wet distillers juice with solubles (SBWDJS), 355 g/kg wheat straw and 170 g/kg wheat bran.

^a,b Means in the same row (T mean) with different letters are significantly different (P < 0.05).

^x,y Means in the same column (day mean) with different letters are significantly different (P < 0.05).

Table 7 Growth measurements of Holstein steers fed TMR with timothy hay (control), TMR with sugar beet wet distillers juice with solubles (SBWDJS) silage blend (USTMR), and TMR with SBWDJS inoculated with Amylomyces rouxii silage blend (ASTMR) treatment diets.

		Treatment				P value
Items	D of experiment	Control	USTMR	ASTMR	SEM	T	D
No. of steers		11	9	9
FI (kg/d head^−1)		12	13	13
BW
Initial (kg)		646	613	609.1	–	0.55	–
Final^1 (kg)		682.3	650.2	657.3	13.1	0.24	–
ADG^2 (kg/d)	14	0.8	1.2	0.9	0.1	–	0.21
	28	1.2	1.1	1.1	0.1	–	0.95
	43	0.6	1.1	0.7	0.1	–	0.06
TADG		0.9	1.1	0.9	0.1	0.09	–

ADG, average daily gain; BW, bodyweight; D, day; FI, feed intake (as feed base); T, treatment; TADG, total average daily gain. ASTMR, TMR + blend of 475 g/kg SBWDJS, 355 g/kg wheat straw, 150 g/kg wheat bran and 20 g/kg Amylomyces rouxii; Control, TMR + timothy hay; USTMR, TMR + blend of 475 g/kg SBWDJS, 355 g/kg wheat straw and 170 g/kg wheat bran.

¹ Final bodyweight was taken at the end of the experimental period, which lasted for 43 days.

² Analysed with day as the repeated measure. No significant effect (P > 0.05) for day and treatment. Determined by calculating the differences between initial and final time points before dividing by the number of days in the study.

TADG was taken for 43 days (experimental period).

Discussion

Wet distiller grains have been documented to be a good source of protein and energy for cattle feeding (Klopfenstein et al. 2008); however, research on the ensiling and feeding impact of SBWDJS has not been conducted. Therefore, in the current study, we measured the fermentation characteristics of ensiled WDSBJS and the feeding impact on steer growth. Ensiled blends revealed a decrease in CP concentration in both AS and US treatments with a tendency to increased ammonia nitrogen concentrations in both treatments. These results can be explained based on the fact that protein degradation occurs extensively in wet distillers via plant degradation enzymes and/or microbial activity (Mjoun et al. 2011). Moreover, Mjoun et al. (2011) found that ammonia nitrogen concentrations were elevated when corn wet distillers grains with solubles were ensiled in combination with whole corn plants. With time, a tendency towards an increase in ADF and NDF concentrations was observed. Generally, the differences over time for ADF, NDF and VFA (organic acids) concentrations within the ensiling process are correlated to the changes in carbohydrate components during the fermentation process (Anderson et al. 2009). The process of converting the carbohydrates to VFA results in a loss of organic matter, whereas quantitative components such as ADF and NDF remain unchanged, which explains why the NDF and ADF concentrations of DM appeared to increase over time during the fermentation process. Despite some numerical differences regarding overall concentrations, these results agree with previous ensiling experiments that used wet brewers grains and wet distillers grains mixed with soybean hulls (Nishino et al. 2003; Wang & Nishino 2008; Anderson et al. 2009).

For ensiled wet distillers grains (WDG), pH values near to 4 are common (Mjoun et al. 2011) and these pH values are probably a result of the initial WDG acidity, which is caused by the addition of sulphuric acid to halt the fermentation process during ethanol production. Previous ensiling trials using corn wet distillers grains or wet brewers grains have reported a pH range of 3.7–4.8 (Abrams et al. 1983; Anderson et al. 2009; Mjoun et al. 2011). In agreement with those previous reports, the pH values of the AS and US silage blends fell within this range. In both treatments, LA concentrations increased over time due to the growth of LA bacteria (fermentative bacteria), that naturally produce LA from the conversion of complex hetero-carbohydrates to simpler water-soluble carbohydrates (Oda et al. 2002). However, the AS silage blend had higher LA concentrations than the US silage blend. Our hypothesis examined the addition of an aerobic fermentation agent that produces LA to the ensiling process to increase initial LA production in order to better preserve feed quality. In the current study, the addition of A. rouxii to SBWDJS silage might have caused the increase in LA concentration over the US treatment. However, with prolonged ensiling, LA concentrations decreased. Consistently, Wang & Nishino (2008) suggested that a reduction in LA concentrations was most probably due to the activation of Lactobacillus plantarum and L. buchneri, which are known to produce AA from LA under anaerobic conditions. Taken together, these results suggested that SBWDJS may be a nutritive component that can be stored by ensiling for a prolonged period without spoilage.

The impact of feeding the two ensiled blends (AS and US) was evaluated on fattening Holstein steers' blood metabolites and growth performance. Plasma metabolites are useful as biochemical indicators for the energy metabolism and nutritional status of beef cows (Lawrence et al. 2011). To our knowledge, no published data regarding the relationship between SBWDJS silage blends and blood metabolites exist. Analyses of blood biochemical indicators revealed that incorporating AS and US silages in the steer diets resulted in normal blood values for most of the studied indicators when compared with the control diets (Duncan & Prasse 2003). However, concerning the increase in blood urea nitrogen concentrations in the ASTMR fed steers, it is well known that in ruminants, blood urea nitrogen can be influenced by dietary nitrogen-to-energy ratio, level of forage intake, protein degradability in the rumen, and dietary carbohydrate amount (Polat et al. 2009). In the current experiment, both US and AS silage blends contained soluble protein; however, the addition of A. rouxii in the AS silage blend might have caused an increase in the ruminal ammonia concentrations in ASTMR fed steers, leading to higher blood urea nitrogen concentrations. Moreover, the recorded ADG values for USTMR and ASTMR diets were comparable to those values of the control diet. Similarly, Anderson et al. (2009) found that the initial and final bodyweights did not differ among treatments when Holstein heifers were fed ensiled wet distillers grains mixed with soybean hulls. At the feeding levels tested in the current study, our results suggested that diets containing silage based on wet distillers derived from sugar beet ethanol production will support growth at a level equal to other standard diets.

In conclusion, sugar beet wet distillers juice with solubles was successfully ensiled with or without A. rouxii inoculation. Both ensiled blends maintained growth performance in steers when they were fed with a traditional TMR ration containing soybean meal and corn. Ensiling SBWDJS is a good method for utilising ethanol industry by-products and provides a promising feedstuff. Further experiments incorporating different levels of WDSBJS silage with longer feeding periods in steers are still required.

Acknowledgements

The authors would like to thank Hokkaido Bioethanol Co. for providing sugar beet wet distillers for the ensiling process. We also would like to extend our gratitude to Professor Suzuki Mitsuyoshi (Obihiro University of Agriculture and Veterinary Medicine, Department of Life Science and Agriculture) for his guidance in the statistical analysis and Dr Adam Cronin (The United Graduate school of Agricultural Science, Iwate University) for his content revision and guidance.