Effect of inoculated or ammoniated high-moisture ear corn on finishing performance of steers

Animal Feed Science and Technology 182 (2013) 25–32

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Effect of inoculated or ammoniated high-moisture ear corn on finishing performance of steers E. Diaz a , D.R. Ouellet b,∗ , A. Amyot c , R. Berthiaume b , M.C. Thivierge a a b c

Département des sciences animales, Université Laval, Québec, QC, Canada Dairy and Swine R&D Centre, Agriculture and Agri-Food Canada, Sherbrooke, Québec, Canada Research and Development Institute for the Agri-Environment (IRDA), Deschambault, Québec, Canada

a r t i c l e

i n f o

Article history: Received 18 April 2012 Received in revised form 30 January 2013 Accepted 7 April 2013

Keywords: Silage additive Steers Finishing performance Digestibility

a b s t r a c t We investigated the effects of inoculated or ammoniated high-moisture ear corn (HMEC) on fermentation characteristics of silages, nutrient digestibility, nitrogen balance and finishing performance of steers. The HMEC was ensiled in both mini silos and press bags. The following treatments were compared: (1) Uninoculated HMEC (CO); (2) Homolactic bacterial inoculated HMEC (HOBI; Lactobacillus plantarum and Enterococcus faecium 0.91 × 105 cfu/g of fresh HMEC); (3) Heterolactic bacterial inoculated HMEC (HEBI; Lactobacillus buchneri 1.0 × 105 cfu/g of fresh HMEC); (4) Ammonia treated HMEC (AMMO; aqueous solution of NH4 OH, 295 g/kg NH3 , 0.90 kg/L was applied at 16 g/kg of fresh HMEC). For the finishing trial, 36 steers were fed HMEC-based diets over 142 days according to an incomplete block design. Four additional steers were used in a 4 × 4 Latin Square design to measure the nutrient digestibility and nitrogen balance of diets. The AMMO silage was highest in pH, ammonia, and soluble carbohydrates compared with CO, HOBI and HEBI silages. Digestibility of DM, OM, aNDF, ADF, and starch were not different (P>0.15) among treatments. Nitrogen retention was also not affected (P>0.20) by treatments. No impact (P>0.15) on body weight gain, gain to feed ratio, hot carcass weight, carcass yield and carcass grading of steers was observed during the finishing phase. In conclusion, inoculation of HMEC with homo- or hetero lactic bacteria or aqueous ammonia resulted in marginal changes in fermentation characteristics leading to similar diet digestibility and comparable performance during the finishing phase of steers. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.

1. Introduction Ensiling high-moisture ear corn (HMEC) reduces fuel and labour costs when compared with artificial drying of corn grain. In addition, one advantage of harvesting HMEC lies in the fact that it can be harvested earlier which reduces field losses and allows seeding of late-maturing hybrids. However, HMEC may be more subject to aerobic conditions which can lead to spoilage. Slow filling rates, low packing density at the moment of ensiling and bad management of the silo face

Abbreviations: ADF, acid detergent fibre expressed inclusive residual ash; ADG, average daily gain; ADIN, acid detergent insoluble nitrogen; AMMO, high-moisture ear corn sprayed with aqueous ammonia; aNDF, neutral detergent fibre expressed inclusive residual ash; BW, body weight; cfu, colony forming units; CO, control high-moisture ear corn; DMI, dry matter intake; HEBI, high-moisture ear corn treated with the heterolactic bacterial inoculant; HOBI, high-moisture ear corn treated with the homolactic bacterial inoculant; HMEC, high-moisture ear corn; Lignin (sa), determined by solubilisation of cellulose with sulphuric; NDIN, neutral detergent insoluble nitrogen; NH3 -N, ammonia nitrogen; OM, organic matter; SEM, standard error of the mean; TMR, total mixed ration. ∗ Corresponding author. Tel.: +1 819 7807209; fax: +1 819 5645507. E-mail address: [email protected] (D.R. Ouellet). 0377-8401/$ – see front matter. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.anifeedsci.2013.04.007

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may accentuate establishment of aerobic conditions in the silo. Consequently, yeasts may grow and metabolize lactic acid leading to an increase in silage pH to a point that opportunistic bacteria and moulds grow (McDonald et al., 1991). Such a phenomenon results in losses of dry matter (DM) and nutritive value which in turn might reduce animal performance (Whitlock et al., 2000). To facilitate fermentation and reduce aerobic spoilage or both, a variety of additives are available. The efficiency of propionic acid (Sebastian et al., 1996) and buffered propionic acid-based additives (Ranjit and Kung, 2000; Kleinschmit et al., 2005) to inhibit growth of moulds and yeasts in corn silage and high moisture corn is largely documented. Ammonia applied to HMEC (Alli et al., 1983) reduced initial population of yeasts and moulds but prevented also the initial increase of populations of lactic acid bacteria. Elevated costs combined with recommended high application rates (3–6 g/kg of wet forage weight) and safety issues have limited the use of chemical additives on HMEC. Homolactic bacterial inoculants containing Lactobacillus plantarum have been used to promote efficient fermentation of high-moisture corn. For L. plantarum, improved aerobic stability has been reported in corn silage diets (Wohlt, 1989). However, it seems that forage sources exert a strong influence on efficacy of inoculants. A review of the literature indicates that homofermentative inoculants were effective approximately 60% of the time with beneficial response often observed in grass and alfalfa silages while less than 50% in corn silage and 33% in whole-crop small grain silages (Much, 2010). Recently, the use of a heterolactic bacteria (Lactobacillus buchneri) has been shown to inhibit yeasts (Kleinschmit et al., 2005) and improve the aerobic stability of whole plant corn silage (Taylor and Kung, 2002). However, few studies have investigated the effect of heterolactic bacteria on the performance of finishing steers fed treated HMEC. For example, the effects of high concentrations of acetic acid in silages treated with L. buchneri, which may depress intake, could not be evaluated by a meta-analysis approach due to the very low number of publications on the subject and, therefore, still remains a subject of debate (Kleinschmit and Kung, 2006). Still today, only 50% of the studies using inoculants gave a positive animal response (Muck, 2010) and the reasons for that remain unclear. To our knowledge, there are no reports evaluating in a single experiment, homolactic vs. heterolactic bacteria or aqueous ammonia applied specifically to HMEC on feedlot performance. Therefore, the current study was designed to compare the effect of homolactic vs. heterolactic bacteria or aqueous ammonia applied to HMEC on digestibility, N usage and performance of finishing steers. 2. Materials and methods 2.1. Harvest and treatment of HMEC High-moisture ear corn (Hybrid DKC27-12, 2250 corn heat units, 670 g/kg DM ± 17) was harvested over four consecutive days using a New Holland 790 forage harvester equipped with 1 row corn head (New Holland). The knives were adjusted to obtain a majority of particles shorter than 7.5 mm. The forage was transported from the field to the storage area in selfunloading wagons (Dion HD185). Forage was placed on a conveyor belt where application of treatment was performed just prior to ensiling. The four large scale silos consisted of HMEC either (1) uninoculated (CO); (2) inoculated with a mixture of homolactic bacteria (HOBI, L. plantarum and Enterococcus faecium, Biomax Chr. Hansen A/S, Horsholm, Denmark); (3) or with a heterolactic bacterium (HEBI, L. buchneri, Pioneer 11A44, Pioneer Hi-Bred Ltd., Chatham, ON, Canada); or (4) treated with an aqueous solution of ammonia (AMMO). At the time of silo filling, loads of HMEC were either untreated or treated with the preparations according to manufacturer’s recommendations. Microbial inoculants were applied at the rate of 1 g/ton of fresh HMEC, preparing 25 g of inoculant in 50 L of water and applying the solution at the rate of 2 L/ton of fresh HMEC. This provided 0.91 × 105 colony-forming-units per gram (cfu/g) of fresh HMEC with HOBI and 1.0 × 105 cfu/g of fresh HMEC with HEBI. Commercial ammonia (NH4 OH, 295 g/kg NH3 , 0.90 kg/L) was applied at a rate of 16 kg/ton of fresh material. Five repetitions of each treatment were also stored in mini silo (27.5 cm, diameter × 44 cm, height, 26 L capacity) to study HMEC fermentation. Each silo was filled with 16.2 kg of forage that was packed with a hydraulic press to a density of ∼420 kg DM/m3 and weighed prior to being filled and immediately after sealing the lid with thermoplastic (Mulco Inc. Montreal, Canada). Mini silos were stored in a temperature controlled room to mimic the external temperature where the large scale silos were stored. Temperature in the room was gradually decreased from +12 ◦ C to 0 ◦ C from October to December, kept between 0 ◦ C and −5 ◦ C from December to April and then increased gradually from 0 ◦ C in April to 18 ◦ C in June. For the large scale HMEC, four different pressed bag silos (Bag All, Klerk’s Plastic Products Manufacturing Inc. Richburg, SC) were prepared using a silage compactor (Roto Press, Sioux Automation, Sioux City, IA), one allocated to each treatment. One day was required to complete each silo (15 tons DM ± 0.5 ton; 27 m length ± 1 m; 1.35 m diameter). The plastic pressed bags were placed on a concrete surface. All HMEC in mini silos were ensiled for 225 days while pressed bag silos were ensiled for 180 days prior to feed out in early May. 2.2. Finishing performance and digestion experiment Experiments outlined below were approved by the local Animal Care and Use Committee of the “Centre de recherche en sciences animales de Deschambault” and animals were treated according to the Canadian Council on Animal Care (1993) guidelines.

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2.2.1. Finishing performance Thirty-six crossbred Charolais steers (427 ± 27 kg initial BW) were grouped on the basis of their initial weight and allocated according to a randomized incomplete block design to study the effects of treated HMEC on finishing performance. The four HMEC silages outlined previously were evaluated during a period of 142 days. Steers were housed indoors in groups of three in 12 concrete pens (4.6 × 4 m). Steers had access to a continuous supply of water and were individually fed their respective diets using electronic gates (American Calan, Northwood, NH). During a 30-days pre-experimental period, steers were adapted to their environment and to electronic gates. During the week prior to the onset of the experiment, steers were vaccinated for bovine rhinotracheitis, parainfluenza-3, Haemophilus somnus, bovine virus diarrhoea and bovine respiratory syncytial virus (Triangle 4 + HS, Fort Dodge Animal Health, IA). Simultaneously, they were administered 22.5 mg of Se and 225 mg of vitamin E (Mu-SE Intervet Schering-Plough Animal Health). Steers were implanted once with Revalor S® (120 mg of trenbolone acetate and 24 mg of estradiol; Intervet Lane Millsboro, DE). The experimental diets (g/kg DM basis) consisted of 607 HMEC, 101 corn silage, 192 dry cracked corn, 71 soybean meal and 29 vitamin-mineral mixture including monensin to offer 33 mg per kg of DM. Silages were removed at the rate of 12.5 to 17.5 cm/d from each silo. Dietary ingredients were mixed mechanically for 5 min and offered ad libitum once daily at 12:30 h as a total mixed ration (TMR). Diets offered were adjusted weekly for DM content of HMEC and corn silage in order to provide fixed ratios of ingredients on a dry matter basis. Given that ammonia was used as an additive to HMEC, urea (15 g of N/d) was incorporated into the mineral mixture of CO, HOBI and HEBI treatments to make diets isonitrogenous, and to keep degradable protein intake constant. Dietary treatments were formulated to meet requirements of finishing cattle gaining 1.5 kg/d (National Research Council, 1996). Steers were weighed without shrink on three consecutive days at the beginning and end of the experiment. They were further weighed every 21 days at 08:00 h during the experiment. Feed intake and refusals were recorded daily throughout the study. Samples of each ingredient, TMR and feed refusals were taken weekly, mixed to obtain composite samples representing a 21 days period, and stored at −20 ◦ C for subsequent chemical analyses. On day 142 of the experiment, steers were transported to a commercial slaughterhouse. At slaughter, hot carcass weight was recorded and carcasses were graded using official grading criteria (Agriculture Canada, 1992; B1 = devoid of marbling or less than 4 mm grade fat, A = trace of marbling, AA = slight marbling, AAA = small marbling with youthful, bright, red-firm meat and white-amber-firm fat). 2.2.2. Digestion experiment Four additional crossbred Charolais steers (423 ± 9 kg initial BW) were used in a concurrent 4 × 4 Latin Square design to measure the nutrient digestibility and nitrogen balance of the four experimental diets. Steers in the digestion trial were at a similar physiological state to those on the finishing experiment. Each experimental period of the digestion trial lasted 21 days. Steers were weighed without shrink at the beginning and end of each experimental period. Days 1–7 were allocated for ad libitum consumption measurement (average observed = 7.6 kg/d). Days 8–14 were allocated to restrict feeding to represent 0.90 of ad libitum intake. Steers were confined to metabolic crates with free access to water from day 13 to 21 of each experimental period to conduct digestibility and N balance measurements from day 15 to 21. During the digestibility and N balance experiment, total urine excreted was collected, weighed, and sampled daily. Concentrated H2 SO4 (50 mL) was added to each container to prevent ammonia loss (Chen et al., 1990); the final urinary pH was between 2 and 3. Daily samples were taken representing 0.01 total urinary excretion, frozen at −20 ◦ C, and pooled at the end of each experimental period to obtain one composite sample per animal per period. Total faeces were collected, weighed daily and thoroughly mixed. A sample representing 0.02 of total daily excretion was frozen at −20 ◦ C, pooled, and thoroughly mixed to obtain one composite sample per animal per period. Diets and individual ingredients were sampled on a daily basis during this experiment. When applicable, feed refusals were also recorded and sampled for further analyses to calculate DM and nutrient intake. 2.3. Analytical methods The HMEC stored in mini silos for 225 days were analyzed for DM (10 g of wet silage at 100 ◦ C to a constant weight). For the pH measurement, 10–15 g of silage were mixed in 20–30 mL of distilled water for 20 min and an electrode was inserted in the liquid mixture (Accumet 925, Fisher Scientific, Nepean, ON, Canada). Soluble carbohydrates and organic acids were determined as described previously (Denoncourt et al., 2006). After 225 of fermentation, yeasts and molds counts in HMEC were performed (Douey and Wilson, 2004). The HMEC obtained from the mini silos were also evaluated for their aerobic stability (Ruppel et al., 1995). Samples of HMEC from pressed bags, total mixed diets, individual ingredients and refusals were freeze-dried and dry matter was recorded. Samples were further ground through a 1 mm screen using a Wiley mill (Brabender® GmbH & Co. KG, Duisburg, Germany). Total mixed diets, individual ingredients and refusals were analyzed for ash according to AOAC procedure (AOAC 942.04; AOAC, 1990). The acid detergent fibre expressed inclusive residual ash (ADF) and neutral detergent fibre expressed inclusive residual ash (aNDF) analyses were conducted according to Van Soest et al. (1991) using sodium sulfite and heat-stable ␣-amylase. Lignin was further assessed by the sulphuric acid method (Lignin (sa), (AOAC 973.18; AOAC, 1990) after a sequential neutral-acid detergent extraction. Total N was determined by the Kjeltec System II (Tecator, Herndon, VA), as well as neutral and acid detergent insoluble nitrogen (NDIN and ADIN, respectively; fibre residue digested with H2 SO4 /peroxide at 420 ◦ C for 80 min, with the residue analyzed for N as described earlier). Starch content of HMEC, faeces and diets was measured according to an enzymatic method (McCleary et al., 1997;

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Table 1 Dry matter content at ensiling, fermentation-end products and microbiological analyses of high-moisture ear corn treated with different additives preserved in mini silos during 225 days. Item

DM (g/kg fresh at ensiling time) pH NH3 -N (g/kg DM) Lactic acid (g/kg DM) Acetic acid (g/kg DM) Lactic:acetic acid ratio Soluble carbohydrates (g/kg DM) DM recovery (g/kg DM ensiled) Aerobic instability (◦ C/day) Yeasts (log 10 cfu/g) Moulds (log 10 cfu/g)

HMEC (n = 5)

SEM

CO

HOBI

HEBI

AMMO

674 4.06a 0.52a 13.7a 4.1ab 3.35b 26.6ab 988 5.0ab 4.7 1.3

675 4.03a 0.46a 14.3a 3.6a 4.03c 21.6a 982 6.8b 5.8 1.5

674 3.99a 0.60a 14.8a 5.1b 2.92b 21.4a 981 3.6a 1.9 1.7

674 7.56b 2.88b 3.4b 6.7c 0.54a 40.7c 988 5.2ab 2.8 2.3

4.2 0.10 0.33 1.1 0.3 0.15 1.62 29 0.7 1.2 0.4

Means within a row with different letters (a, b, c) differ (P<0.05). Yeast tended to be higher (P<0.14) for HOBI vs. HEBI.

Megazyme Int., Bray, Ireland). Ether extract content was determined according to AOAC method no. 954.02 (AOAC, 1990) and gross energy determined with an adiabatic bomb calorimeter (model 141, Parr Instruments Co., Moline, IL). Samples of HMEC taken during the finishing experiment were further analyzed for ammonia nitrogen (NH3 -N; steam distillation with MgO addition, according to Stevenson, 1982) from an aliquot (adding 100 ml of deionised water to 25 g of wet sample and allowing the sample to balance for 2 h at room temperature). Faecal samples were analyzed for total N, ash, gross energy, aNDF, ADF and freeze-dried urine samples for total N and gross energy using methods outlined previously in this section. Digestibility of DM, OM, N, aNDF, ADF and starch were calculated according to differences between intake and excretion. Digestible energy was calculated as the difference between the gross energy values of the ration ingested and the gross energy value of the collected faeces. Nitrogen retention was defined as N intake minus the sum of N outputs in faeces and urine.

2.4. Statistical analyses Data of the finishing experiment were statistically analyzed using the MIXED procedure of SAS (9.1) according to an incomplete block design using individual animal as the experimental unit and where treatments were considered as fixed effects and weight block as random effects. Carcass grading is presented as percentage of animals per grade (AAA or AA), the Cochran-Mantel-Haenszel test (Landis et al., 1978) in the FREQ procedure of SAS (9.1) was used to compare these results. Data from the digestibility experiment were statistically analysed using the MIXED procedure of SAS (9.1) according to a 4 × 4 Latin Square design with animal as random and period and treatment as fixed effects. Probability values were corrected for multiple comparisons using the Tukey–Kramer adjustment (Hayter, 1984). Treatment effects were declared significant at P<0.05. Data of one steer fed ammoniated HMEC was removed because of unrealistic N retention (N retained > 110 g/d).

3. Results 3.1. High-moisture ear corn composition The DM contents of HMEC were similar at ensiling time (Table 1). After 225 days of conservation, pH of AMMO was 7.56 compared with an average of 4.03 for the other 3 treatments. Similarly, the concentrations of NH3 -N and acetic acid were higher in AMMO compared with CO, HOBI and HEBI. Conversely, concentration of lactic acid was lower in AMMO compared with the other treatments. The lactic:acetic acid ratio was higher in HOBI, intermediate in CO and HEBI and lower in AMMO. Soluble carbohydrates content were highest in AMMO, intermediate in CO and lowest and similar between inoculated silages. The aerobic instability was higher (P<0.01) for the HOBI (6.8 ◦ C/day) than for the HEBI treatment (3.6 ◦ C/day). Addition of homofermentors to HMEC tended to increase (P<0.12) yeasts counts when compared with heterofermenters (6.8 and 3.6 log 10 cfu/g, for HOBI and HEBI, respectively) Treatments of HMEC had no effects on dry matter recovery (98.5% DM ensiled) and mold counts (1.7 log 10 cfu/g). The chemical composition of the pressed bags compared well with the mini silos. Dry matter was 21 g less per kg while pH and lactic acid were similar. Acetic acid was different for HEBI (17.0 vs. 5.1 for pressed bag and mini silos, respectively). As a result of ammonia addition, the CP content of HMEC was greater than 130 g/kg DM in AMMMO (Table 2). The mean ADIN concentration was also higher in AMMO. Treatments had no effect on NH3 -N. Starch concentration was numerically lower in HOBI and HEBI compared with the untreated HMEC.

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Table 2 Mean chemical composition of treated and untreated high-moisture ear corn used during the performance experiment. Nutrient

HMEC (n = 6)

DM (g/kg fresh) pH Lactic acid (g/kg DM) Acetic acid (g/kg DM) Lactic:acetic acid ratio CP (g/kg DM) NH3 -N (g/kg DM) NDIN (g/kg of total N) ADIN (g/kg of total N) aNDF (g/kg DM) ADF (g/kg DM) Lignin (sa) (g/kg DM) Ether extract (g/kg DM) Starch (g/kg DM) Ash (g/kg dry matter) Gross energy (MJ/kg DM)

CO

HOBI

HEBI

AMMO

636 4.2 9.5 3.1 2.91 108 0.62 105 47 202 94 20 43 502 24 18.6

655 4.4 8.9 2.3 4.44 105 0.57 92 41 188 91 13 45 423 21 19.0

634 4.3 8.8 17.0 0.51 109 0.80 97 43 188 93 17 45 455 21 18.7

646 6.9 4.0 7.2 0.47 132 3.77 110 70 188 97 19 41 496 26 18.5

Table 3 Digestibility of nutrients in four steers fed a TMR containing high-moisture ear corn treated with different additives. Item

DM OM aNDF ADF Starch Ether extract Gross energy

TMR CO

HOBI

HEBI

AMMO

0.764 0.789 0.371 0.329 0.871 0.846 0.731

0.795 0.824 0.464 0.450 0.906 0.869 0.781

0.785 0.807 0.443 0.524 0.883 0.779 0.761

0.791 0.813 0.535 0.521 0.886 0.815 0.756

SEM

P

0.017 0.016 0.058 0.063 0.015 0.031 0.025

0.56 0.51 0.27 0.15 0.37 0.24 0.57

3.2. Digestion trial The digestibility coefficients of DM, OM, aNDF, ADF and energy although numerically higher for treated HMEC as compared with CO, were not altered by treatments (Table 3). Digestibility coefficient of starch was also similar among treatments. Nitrogen balance was also unaltered by the different treatments of HMEC, despite the numerical reduction in the amount and proportion of fecal N excretion observed for HOBI, HEBI and AMMO (Table 4) which resulted in 20 to 40 g/kg higher apparently digested N compared to CO. 3.3. Finishing trial Chemical composition of the TMR fed during the finishing experiment was similar between treatments (Table 5). The numerical changes in HMEC composition produced by additives had no effect on finishing performance of steers (Table 6). Mean DM intake, average daily gain (ADG) and Gain:Feed ratio averaged 9.96 kg/d, 1.43 kg/d, and 0.15 kg:kg, respectively. Table 4 Nitrogen balance measured in four steers fed a TMR containing high-moisture ear corn treated with different additives. Item

N intake (g/d) Fecal N (g/d) Fecal N (g/kg of N intake) Urinary N (g/d) Urinary N (g/kg of N intake) Total N excreted (g/d) Apparently digested N (g/d) Apparently digested N (g/kg of N intake) Retained N (g/d) Retained N (g/kg of N intake) Retained N (g/kg of N absorbed)

TMR CO

HOBI

HEBI

AMMO

156 48 282 56 363 104 123 718 52 328 413

149 39 240 53 362 92 125 760 57 374 444

158 45 259 64 402 109 129 741 50 313 383

146 42 264 52 352 94 118 736 50 351 432

SEM

P

15.0 4.5 28 6.3 44 7.3 13.8 28 12.4 55 62

0.87 0.34 0.61 0.33 0.80 0.14 0.93 0.61 0.97 0.75 0.86

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Table 5 Chemical composition of TMR containing high-moisture ear corn treated with different additives fed to steers during a finishing trial. Item

TMR CO

DM (g/kg fresh) 627 Composition of dry matter (g/kg DM unless otherwise stated) 142 CP 201 aNDF 97 ADF 29 Lignin (sa) Ether extract 32 Starch 477 43 Ash 18.8 Gross energy (MJ/kg DM)

HOBI

HEBI

AMMO

637

619

631

146 221 106 21 40 446 37 18.5

141 212 99 20 38 494 42 17.2

139 202 107 24 39 494 39 18.1

Hot carcass weight (351.7 ± 7.7 kg; mean ± SEM), carcass yield (56.0 ± 0.7%; mean ± SEM) and quality grade were not affected by treatments (P>0.10; Table 6). 4. Discussion 4.1. High-moisture ear corn composition Ammoniation lead to a different fermentation profile as compared with the other treatments. The pH of CO, HOBI and HEBI were close to 4.0, an adequate pH to reduce heating and spoilage, whereas AMMO had a pH greater than 7.0 reflecting the inhibitory effect of ammonia on lactic acid bacteria (Woolford, 1984). As expected, HOBI resulted in a greater Lactic:acetic acid ratio than CON, HEBI and AMMO. The very marginal difference in the fermentation products of HMEC caused by microbial inoculation (HOBI and HEBI) corroborates the findings of Wardynski et al. (1993) which indicated that the high dry matter content of HMEC limits fermentation. Acetic acid concentrations was lowest for HOBI while yeasts counts tended to be higher for HOBI vs. HEBI suggesting that heterolactic bacteria had a small effect on yeast growth. In addition, the improvement in aerobic stability seems to corroborate this positive effect of HEBI over HOBI on reducing the population of aerobic organisms. It was postulated that yeasts can produce ethanol which in turn will reduce DM recovery (Woolford, 1984). In the present experiment, although ethanol was not measured, its production may have been similar among treatments given the high and similar DM recovery (985 g/kg) among treatments. The higher crude protein content of AMMO was caused by the addition of aqueous ammonium at ensiling. Based on the application rate (16 g/kg wet weight), 0.40 of the added N was recovered in the mini silos whereas 0.66 of the added N was recovered in the large-scale silo. Similar N recovery (0.67) was observed in large-scale silos of whole plant corn silage (Huber and Santana, 1972). Alli et al. (1983) reported a 0.23 recovery, however, they dosed HMEC with a 10 g/kg (fresh weight) ammonia which increased N content by 43%. Higher fiber bound N in AMMO was also reported for ammonia-treated hay (Benahmed and Dulphy, 1986) and could be linked to the exothermic reaction following the application of ammonia. In terms of soluble carbohydrates, CO, HOBI and HEBI utilized the carbohydrates present at ensiling (27.5 g/kg of DM; data not presented) while AMMO accumulated soluble carbohydrates which agrees with the previously reported partial dissolution of hemicellulose following ammoniation (Harbers et al., 1982). Lowest starch concentrations in HOBI and HEBI reveal the action of both bacterial sources to utilize starch during fermentation. Although this was only observed in pressed bags, the high acetic acid content in HEBI is typical of this source of bacteria (Woolford, 1984; Kleinschmit et al., 2005).

Table 6 Finishing performances measured in steers fed TMR containing high-moisture ear corn treated with different additives during 142 days. Item

Initial weight (kg) Final weight (kg) Total gain (kg) DMI (kg/d) DMI/BW (kg/kg) ADG (kg/d) Gain:feed (kg/kg) Hot carcass weight (kg) Dressing (kg carcass/100 of BW) Grade (%)a AAA/AA a

TMR CO

HOBI

HEBI

AMMO

418.3 619.0 201.0 10.27 0.0198 1.44 0.14 349.0 56.49 55.5/44.4

436.3 637.3 200.6 9.94 0.0185 1.43 0.15 354.4 55.66 33.3/66.7

433.0 619.5 188.7 9.63 0.0182 1.35 0.14 348.2 56.24 50.0/50.0

437.3 647.5 208.9 10.00 0.0184 1.49 0.15 357.7 55.09 37.5/62.5

Grade: Carcass grading based on Canadian Beef Grading Agency Standard (Agriculture Canada, 1992).

SEM

P

8.13 12.15 9.46 0.45 0.0007 0.07 0.006 7.7 0.65

0.16 0.21 0.52 0.76 0.31 0.52 0.40 0.74 0.43 0.78

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4.2. Digestion trial We merely observed a numerically higher digestibility of aNDF and ADF for AMMO, HOBI, and HEBI, compared with CO. Schaefer et al. (1989) also reported no effect of inoculation of HMEC on NDF digestibility when evaluated in growing steers diets. However, Phillip and Fellner (1992) reported an unexpected decrease in digestion of OM and ADF in steers fed inoculated HMEC which remains unexplained. The latter authors suggested that response may be partly linked to species and strain of bacteria used and to the crop specificity of the inoculant or both. Digestibility of starch was similar among treatments, corroborating the major impact of ensiling process on carbohydrates availability (Owens and Soderlund, 2007). Recent studies conducted by Hoffman et al. (2011) indicated that the starch–protein matrix, composed mainly of hydrophobic zein proteins in corn, are extensively degraded during the fermentation process of high-moisture corn and that inoculants had no additional effect on hydrophobic zein subunits despite an increase in production of acids during the fermentation. In growing heifers fed ammoniated alfalfa and ingesting more N than heifers on the control diet, Glenn (1990) reported an increase in digested N with a concomitant increase in urinary excretion. Glenn (1990) also indicated that when positive responses to ammoniation are observed in the literature, it seems related to an improvement in the efficiency of microbial protein synthesis. The lack of response observed in the present study on N metabolism could be partly explained by the control that we applied on N intake (0.90 of ad libitum). The incorporation of HMEC in a total mixed ration could also have contributed to dilute the effect of the different treatments on rumen fermentation. 4.3. Finishing trial The effects of inoculants on animal performance have been highly variable and often not significant (Kung and Muck, 1997). Part of the variation observed is related to the material ensiled. Focusing on the results of research conducted with high-moisture corn, we can report that with growing steers, inoculating high-moisture corn with homolactic or heterolactic bacteria had no effect on animal performance (Schaefer et al., 1989; Phillip and Fellner, 1992; Wardynski et al., 1993). Similarly, Phillip et al. (1985) reported no effect on growing performance of steers when ammoniated HMEC was compared with untreated HMEC to which urea was added to make diets isonitrogenous. The inability of inoculants and ammonia to improve high-moisture corn utilization by beef cattle could be linked to the limited fermentation usually observed in this feedstuff as compared to forages (e.g.: whole plant corn silage). The differences in composition between our treatments were likely too small to affect the metabolism of finishing steers which resulted in similar carcass characteristics agreeing with results reported by Schaefer et al. (1989). The current results in the finishing phase corroborate the similarity observed in digestion parameters. 5. Conclusion The results obtained in this experiment indicated that the addition of inoculants to high-moisture ear corn resulted in a product similar to the control. Adding ammonium altered pH, ammonia content, major volatile fatty acids and soluble carbohydrates. However, feeding ammoniated or inoculated HMEC to finishing steers had no effect on diet digestibility and N balance. When the different HMEC sources were fed ad libitum to finishing steers, the comparable characteristics of the diet digestibility did translate into similar growth performance and carcass quality. Acknowledgements The authors would like to thank the management and staff of the “Centre de Recherche en Sciences Animales de Deschambault” for their participation in this project. The authors also gratefully acknowledge S. Giguère and D. Bournival for their technical support and S. Méthot for statistical assistance. This study was funded by “La Fédération des Producteurs de bovins du Québec”, “Coop Fédérée du Québec”, Pioneer Hi-Breed Ltd., Laval University, and AAFC. References Agriculture Canada, 1992. Canada Agriculture Products Act. Livestock Carcass Grading Regulations. Pages 3821-3853 in Canada Gazette Part II. 126. Alli, I., Fairbairn, R., Baker, B.E., Phillip, L.E., Garino, H., 1983. Effects of anhydrous ammonia on fermentation of chopped, high-moisture ear corn. J. 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