Effect of a pine enhanced biochar on growth performance, carcass quality, and feeding behavior of feedlot steers¹

Abstract

The objective of this study was to evaluate the effect of enhanced biochar (EB) on growth performance, carcass quality, and feeding behavior of feedlot steers fed high-forage and high-grain diets. A total of 160 crossbred steers (initial 286 ± 26 kg body weight [BW]) were blocked by BW and randomly assigned to 16 pens (10 steers per pen), 8 of which were equipped with the GrowSafe system for monitoring feeding behavior. Treatments were EB included in the diet at 0% (control), 0.5%, 1.0%, or 2.0% (dry matter [DM] basis) with four pens per treatment. The backgrounding phase (84 d) was divided into four 21-d periods, and the finishing phase (112 d) was divided into four 28-d periods, with a 28-d transition period for dietary adaptation. Pen was the experimental unit for all parameters except for feeding behavior, where steer was considered the experimental unit. Treatment was included as a fixed effect, and period was considered a repeated measure. Total weight gain and overall average daily gain (ADG) tended to decrease (P = 0.06) with 2.0% EB. There was no effect (P ≥ 0.13) of EB on dry matter intake (DMI), gain-to-feed ratio (G:F), net energy for gain, ADG, or final BW for the backgrounding or finishing phases. There was a treatment × period effect (P < 0.05) of EB on DMI, ADG, and G:F for both backgrounding and finishing phases. Hot carcass weight, dressing %, back fat, rib-eye area, and meat yield were not affected (P ≥ 0.26) by EB. Lean meat yield was increased (P = 0.03) by 2.0% EB compared to all other treatments. Compared to the control, 2.0% EB increased (P = 0.02) the number of carcasses that achieved Canada 1 grade. More (P = 0.05) carcasses from control steers were graded as Canada 3 as compared to those fed 0.5% or 2.0% EB. Quality grade and incidences of liver abscesses were not affected (P ≥ 0.44) by EB. Enhanced biochar had no effect (P ≥ 0.11) on feeding behavior during backgrounding or finishing phases. In conclusion, EB did not result in changes in growth rate, feed efficiency, or feeding behavior in feedlot cattle, but 2.0% EB increased lean carcass yield grade.

INTRODUCTION

Improving the efficiency by which cattle convert feed to meat protein can have both economic and environmental benefits. Dietary supplementation is a strategy that beef cattle producers often use to achieve increased meat yield or gain to feed ratio (G:F). Consumer reservations and recent restrictions on the use of antibiotics and hormones have required producers to reduce the use of these growth-enhancing technologies. As such, biochar may represent a “natural” additive with the potential to improve the feed efficiency of feedlot cattle (Leng, 2014). Enhanced biochar (EB) is a form of pyrolyzed organic matter heated (350–650 °C) under oxygen-limited conditions that has also undergone a postpyrolysis treatment. Inclusion of biochar in cattle diets has been suggested to decrease enteric methane (CH₄) emissions from ruminants (Leng et al., 2012; Saleem et al., 2018), with a metabolism study demonstrating that biochar increased ruminal fermentation and growth performance of beef cattle (Leng et al., 2012). The high surface area and porous structure of EB are postulated to promote the formation of biofilms (Leng, 2014), thereby increasing microbial growth efficiency (Leng et al., 2012). Alternatively, recent metabolism trials have found that rumen fermentation, CH₄ production, and microbial N flow were not altered by the inclusion of EB in the diets of beef heifers (Terry et al., 2019; Winders et al., 2019). Though several metabolism experiments have now been published (Leng et al., 2012; Terry et al., 2019; Winders et al., 2019), a comprehensive study examining the effect of EB on the growth performance of feedlot cattle throughout both backgrounding and finishing phases has not been reported. As such, the objective of this study was to examine the effect of EB on growth performance, carcass quality, and feeding behavior in feedlot steers fed high-forage and high-grain diets.

MATERIALS AND METHODS

This study was conducted at the Agriculture and Agri-Food Canada Research and Development Centre in Lethbridge, Alberta. Animals were cared for in accordance with the guidelines of the Canadian Council on Animal Care (2009), and the study was reviewed and approved by the institutional Animal Care Committee at the center (ACC1725).

Animals and Experimental Design

One hundred and sixty Bos taurus crossbred beef steers (286 ± 26 kg live BW) were used in a 235-d experiment. Steers were all sourced from a single farm, blocked by weight, and randomly assigned to 16 pens (10 steers per pen). Of the 16 pens, 8 were fitted with two feeding bins equipped with an electronic monitoring system (GrowSafe Systems, Airdrie, Alberta) as described by Moya et al. (2011). Of the eight GrowSafe pens, two pens were each assigned to one of four treatments: control (0), 0.5, 1.0, and 2.0 EB as a percentage of diet dry matter (DM). Eight additional pens with standard feeding bunks were allocated in a similar manner for a total of four pens per treatment; two with GrowSafe feeding bins and two without.

The EB was supplied by Cool Planet Energy Systems, Inc. (Greenwood Village, CO), which markets biochar products under the brand names of Cool Terra and Cool Fauna. The biomass used for the EB was from southern yellow pine (Pinus echinata) grown in the United States. The EB provided was produced using the company’s proprietary Engineered Biocarbon Technology, which includes front-end pyrolysis (below 650 °C for several minutes) and a patented postpyrolysis treatment step. The posttreated biochar was ground to consistent particle size so that >80% of particles were <5 mm (% DM). The final product underwent a comprehensive chemical analysis by Cool Planet Energy Systems, Inc. (Table 1) and had a dioxin content less than the European Union maximum limit (<0.75 ng/kg). The EB dosages were selected based on a previous metabolism study (Terry et al., 2019).

Table 1.

Chemical and physical characteristics of EB

Item	Composition
Carbon, % DM	75
pH	7–8
Bulk density, kg/m3	160–256
Surface area, m2/g	200–250
Porosity, vol%	60–70
Water holding capacity, wt%	150–250
Particle size distribution
<0.5 mm, % DM	80
0.5–2.0 mm, % DM	20

Steers were fed a backgrounding diet for the first 84 d, followed by a 28-d transitional diet with sequential increases in the proportion of barley grain in the total mixed ration (TMR). Steers were then fed a finishing diet for the last 112 d (finishing phase), after which they were marketed at a live weight between 650 and 750 kg. The backgrounding phase was divided into four 21-d periods, and the finishing phase was divided into four 28-d periods. Cattle were kept for an additional 11 d after the last finishing period until transport. The final two weigh days were scheduled 2 d before transport to the abattoir.

Animals were fed a typical Canadian feedlot diet during both backgrounding and finishing phases (Table 2). Diets were formulated to meet or exceed the nutrient requirements of backgrounding and finishing feedlot cattle (National Academies of Sciences, Engingeering and Medicine (NASEM), 2016). Animals were ear tagged and implanted with a growth promotor before the start of the backgrounding and finishing phases (Elanco Division of Eli Lilly Canada Inc., Ontario). Each implant contained: 120 mg trenbolone acetate, 24 mg estradiol, United States Pharmacopeia, and 29 mg tylosin tartrate. No ionophore or other antibiotics were included in the diet.

Table 2.

Ingredient and chemical composition of experimental diets fed during backgrounding and finishing phases to feedlot steers

	Treatment
Item	Control	0.5% EB	1.0% EB	2.0% EB
Backgroundinga
DM	47.5	48.2	48.0	49.0
OM	93.0	93.1	92.9	93.5
CP	12.3	12.2	12.1	12.1
NDF	35.5	33.6	34.5	31.9
ADF	19.1	18.5	19.5	19.0
NEmb	1.76	1.79	1.75	1.77
NEgc	1.17	1.19	1.16	1.18
Finishingd
DM	80.7	82.2	81.7	81.2
OM	96.4	96.2	95.7	96.1
CP	12.4	12.6	11.8	11.8
NDF	21.1	19.0	19.1	19.4
ADF	7.44	7.68	6.67	6.26
NEm	2.20	2.20	2.23	2.25
NEg	1.53	1.53	1.56	1.57

The pellet supplied per tonne of dietary DM: 531 kg barley chop, 90 kg canola meal, 250 kg calcium carbonate, 19.5 kg molasses, 28.5 kg salt, 9.9 kg feedlot premix, 19.8 kg urea, 0.66 kg vitamin E (50%), and 9.9 kg canola meal. The feedlot premix in the supplement contained per kilogram of dietary DM: 15 mg Cu, 65 mg Zn, 28 mg Mn, 0.7 mg I, 0.2 mg Co, 0.3 mg Se, 6000 IU vitamin A, 600 IU vitamin D, and 47 IU of vitamin E.

CP, crude protein.

^aBackgrounding diet consisted of 60% barley silage, 35% barley grain, and 5% supplement (DM basis)

^b,cNet energy for maintenance and gain, respectively, is calculated by summative energy equation (NASEM, 2016).

^dFinishing diet consisted of 10% barley silage, 85% barley grain, and 5% supplement (DM basis)

Feed Sampling

Feed was delivered as a TMR daily at 0900 h. Steers were fed to appetite using a slick bunk practice to target <5% orts. Feed offered was recorded daily, with feed refusals weighed and sampled weekly. Ingredient DM was determined weekly and the TMR was adjusted if silage DM deviated more than 3 units from the average. Samples for chemical analysis were composited by period and immediately dried at 55 °C for 3 d for DM determination. Dry matter intake (DMI) was calculated as the difference between feed offered and weekly refusals, corrected for DM content.

Live BW

Steers were weighed before feeding on two consecutive days at the beginning and end of each phase (backgrounding, transitioning, and finishing). Steers were also weighed (1 d) at the end of each period (21 d for background and 28 d for finishing). Body weights were reported as shrunk BW by multiplying BW with 0.96 to account for gut fill (Ribeiro et al., 2016). Average daily gain (ADG) was calculated as the difference between mean initial and mean final shrunk BW divided by the total days on feed. The G:F was calculated by dividing ADG by DMI. Net energy for maintenance (NE_m; Mcal/kg DMI) was calculated based on animal weights, DMI, and ADG as described by Zinn and Shen (1998) using the retained energy formula for medium frame steers (RE = [0.0493 × BW^0.75] × ADG^1.097; National Research Council (1996)). Dietary net energy for gain (NE_g) content was calculated from NE_m assuming NE_g = NE_m × 0.877 – 0.41 (Zinn and Shen, 1998).

Carcass Characteristics

At the end of the 235-d feeding period, steers were slaughtered at a commercial processer (Cargill Foods, High River, Alberta). Hot carcass weight (HCW; kidneys removed), dressing percentage, backfat thickness, rib-eye area (REA), saleable meat yield, and quality grade were determined by qualified graders. Dressing percentage was calculated as HCW divided by final BW × 100%. Saleable meat yield (%) was estimated using the length, width, and fat cover of the rib-eye muscle between the 11th and 12th rib as described by Yang et al. (2012). Carcasses were graded for yield grade using the Computer Vision Grading System (VBG 2000 e + v Technology GmbH, Oranienburg, Germany) according to Canadian Beef Grading Agency (CBGA) regulations (CBGA, 2020). Lean yield (YG; %) was determined from the measurement of the length and width of the longissimus dorsi muscle (REA) between the 12th and 13th rib and fat depth according to CBGA (2020). Based on the YG, carcasses were graded as: Canada 1 = ≥52.4%; Canada 2 = 50.2%–52.2%; Canada 3 = 47.7%–50.1%; Canada 4 = 45.2%–47.5%; Canada 5 = ≤45.0%. Livers were scored for abscesses using the Elanco system as described by Ribeiro et al. (2016) and graded as 0, A−, A, or A+. Those livers classified as A+ (1 or more large active abscesses greater than 2.5 cm diameter with inflammation of surrounding tissue) were considered severely abscessed.

Feeding Behavior

Feeding behavior of all steers contained within the GrowSafe pens was recorded throughout the study. Frequency of daily visits, daily duration of total bunk attendance, individual animal feed consumption, eating rate (grams of feed per minute), and average duration of each visit were recorded. Individual DMI and day-to-day variation of DMI (SD of DMI) were reported. The distinct feeding events were pooled into meals using a meal criterion of 300 s as described by Schwartzkopf-Genswein et al. (2002). The amount of feed consumed during a visit was used to calculate meal size (kilograms of DM per meal). GrowSafe data were summarized to report meal frequency (meals per day), the duration of each meal (minutes per meal), and the interval between meals (minutes per day). Feeding time was calculated as the sum of the length of all meals within a day (minutes per day). Feeding rate was determined as the sum of the mass of all meals within a day divided by daily feeding time (grams of DM per minute).

Chemical Analysis

Before analysis, feed samples were oven dried at 55 °C for 72 h. Dried feed was ground in a Wiley mill through a 1-mm screen (Standard model 4 Wiley mill; Arthur H. Thomas, Philadelphia, PA). Samples were analyzed for analytical DM (Association of Official Analytical Chemists (AOAC), 2005; method 930.15), organic matter (OM) (method 942.05), ash (method 942.05), neutral detergent fiber (NDF), and acid detergent fiber (ADF). Samples were analyzed sequentially for NDF (Mertens, 2002) and ADF (AOAC, 2005; method 973.18) with appropriate modifications for a fiber analyzer (F57 Fiber Filter Bags, 200 Fiber Analyzer, ANKOM Technology; Vogel et al. 1999) and with heat-stable α amylase (Termamyl 120, Sigma-Aldrich, St. Louis, MO) and sodium sulfite included. The NDF was expressed exclusive of residual ash. Subsamples (5 g) were further ground with a ball grinder (Retsch MM 400; Retsch Inc., Newtown, PA) and analyzed for N using flash combustion (method 990.03; Carlo Erba Instruments, Milan, Italy). Crude protein was calculated as N × 6.25. Starch concentration was determined as described by Herrera-Saldana et al. (1990), and absorbance was read on a Thermo Scientific Appliskan 1.437 (SkanIt Software 2.3 RE) microplate reader at a wavelength of 490 nm. Net energy for maintenance and gain was calculated by the summative energy equation (NASEM, 2016).

Statistical Analysis

Data were analyzed using the MIXED model procedure of SAS (SAS Institute Inc., Cary, NC). The univariate procedure in SAS was used to test for normal distribution and homogeneity of variance. Pen was the experimental unit for DMI, ADG, G:F, and carcass characteristics, while steer was the experimental unit for feeding-behavior parameters. Treatment was included as a fixed effect and period was treated as a repeated measure. Data for background and finishing were analyzed separately except for total weight gain and total ADG to examine whether dietary composition altered the effect of EB. Initial BW was used as a covariate. The minimum value of Akaike’s information criterion was used to select the most suitable covariance structure. Contrast statements for unequally spaced treatments were used to test for control versus EB treatment effects. The GLIMMIX procedure (SAS Institute Inc.) was used to analyze data for carcass characteristics and liver abscesses using binomial distribution. False discovery rate (FDR) corrected P values were calculated using Tukey’s test. Differences between means were declared significant at P < 0.05.

RESULTS

Total weight gain and overall ADG tended to decrease (P ≥ 0.06) with 2.0% EB (Table 3). There was no effect (P ≥ 0.13) of EB on shrunk and final BW, DMI, G:F ratio, ADG, NE_m, or NE_g over either the backgrounding or finishing phases. There was a treatment × period interaction (P < 0.05) of EB on DMI, ADG, and G:F during both backgrounding and finishing phases, although this difference was not considered biologically relevant. Hot carcass weight, dressing percentage, back fat, REA, and meat yield were not affected (P ≥ 0.26) by EB (Table 4). Lean meat yield was increased (P = 0.03) by 2.0% EB compared to all other treatments. Compared to the control, more (P = 0.02) carcasses from steers fed 2.0% EB were graded Canada 1, whereas more (P = 0.05) control carcasses were graded as Canada 3. All carcasses achieved AAA or AA grade, though grading and incidence of liver abscesses were not affected (P ≥ 0.44) by EB. Enhanced biochar had no effect (P ≥ 0.11) on individual animal DMI, meal frequency, eating duration, intermeal interval, meal size, or eating rate during either backgrounding or finishing phases. There was a control versus EB effect on the SD of DMI during the backgrounding phase, where EB increased the day-to-day variation in intake (Table 5).

Table 3.

Effect of EB on DMI and growth performance of backgrounding and finishing feedlot steers

	Treatment					P valuea
Item	Control	0.5% EB	1.0% EB	2.0% EB	SEMb	Treat	Control vs. EB
Total weight gain, kg	397.5	393.4	393.7	378.6	5.44	0.06	0.15
Overall ADG, kg/d	1.71	1.69	1.69	1.62	0.025	0.08	0.17
NEm, Mcal/kg DMc	1.98	1.96	1.99	1.96	0.026	0.76	0.68
NEg, Mcal/kg DMc	1.35	1.33	1.36	1.33	0.023	0.76	0.68
Backgrounding
Shrunk initial BW, kg	276.3	273.3	274.4	274.8	3.92	0.96	0.65
Shrunk final BW, kg	388.0	382.5	384.6	380.2	5.05	0.73	0.34
DMI, kg/d	8.26	8.28	8.02	8.01	0.127	0.32*	0.32
ADG, kg/d	1.36	1.39	1.34	1.31	0.029	0.29*	0.46
G:F	0.17	0.17	0.18	0.17	0.004	0.67*	0.99
NEm, Mcal/kg DMc	1.55	1.55	1.57	1.53	0.021	0.65	0.88
NEg, Mcal/kg DMc	0.97	0.96	0.98	0.95	0.018	0.65	0.88
Finishing
Shrunk initial BW, kg	439.6	432.2	436.3	429.4	5.47	0.56	0.27
Shrunk final BW, kg	670.3	664.1	665.7	661.0	4.31	0.47	0.24
DMI, kg/d	10.4	10.6	10.4	10.1	0.19	0.40*	0.85
ADG, kg/d	1.91	1.95	2.00	1.91	0.036	0.28*	0.65
G:F	0.18	0.18	0.19	0.19	0.004	0.82*	0.68
NEm, Mcal/kg DMc	2.14	2.09	2.13	2.11	0.035	0.81	0.52
NEg, Mcal/kg DMc	1.49	1.44	1.48	1.46	0.031	0.81	0.52

^aControl vs. EB = control vs. all EB treatments.

^bn = 4 per treatment.

^cCalculated based on performance (Zinn and Shen, 1998)

*Indicate significantly different treatment × period means (P < 0.05).

Table 4.

Effect of EB on carcass characteristics and liver abscess incidence of finishing feedlot steers

	Treatment					P value
Item	Control	EB 0.5%	EB 1.0%	EB 2.0%	SEMa	Treat	Control vs. EBb
HCW, kg	406.1	404.1	402.3	395.7	4.76	0.44	0.33
Dressing %	60.7	60.6	60.5	60.9	0.22	0.51	0.81
Back fat, mm	33.8	33.3	32.3	32.1	3.36	0.26	0.24
REA, cm2	95.6	94.8	95.2	95.1	1.65	0.99	0.76
Meat yield, %	54.2	53.9	54.8	55.1	0.74	0.65	0.62
Lean yield, %c	51.3b	52.1b	52.0b	54.5a	0.77	0.03	0.10
Canada 1d	40.5b	52.5ab	52.5ab	73.7a	0.01	0.02	0.08
Canada 2	21.6	12.5	15.0	13.2	0.48	0.68	0.23
Canada 3	27.0a	7.5b	20.0ab	7.9b	0.18	0.05	0.02
Canada 4	2.7	15.0	7.5	2.6	0.70	0.18	0.40
Canada 5	8.1	12.5	5.0	2.6	0.23	0.42	0.58
AAA, %e	83.8	77.5	82.5	89.5	0.28	0.53	0.91
AA, %f	16.2	22.5	17.5	10.5	0.35	0.35	0.98
Abscessed livers, %	62.2	65.0	50.0	57.9	0.53	0.59	0.59
Severely abscessed, %g	21.6	32.5	30.0	39.5	0.13	0.44	0.19

^an = 4 per treatment.

^bControl versus EB = control versus all EB treatments.

^cLean yield = 57.34 + (0.212 × REA [cm²]) – (0.81 × grade fat [mm]) – (0.032 × HCW [kg]).

^dLean yield grade: Canada 1 = ≥52.4; Canada 2 = 50.2–52.2; Canada 3 = 47.7–50.1; Canada 4 = 45.2–47.5; Canada 5 = ≤45.0.

^eCanada grade AAA (approximately equivalent to United States Department of Agriculture choice); marbling score 500.

^fCanada grade AA; marbling score 400.

^gPercentage of livers classified as A+ (1 or more large active abscesses greater than 2.5 cm diameter with inflammation of surrounding tissue) were considered severely abscessed.

^a,bMeans with different letters in the same row differ (P < 0.05).

Table 5.

Effect of EB on eating behavior of backgrounding and finishing steers

	Treatment					P value
Item	Control	0.5% EB	1.0% EB	2.0% EB	SEMa	Treat	Control vs. EBb
Backgrounding
DMI, kg/d	8.08	8.17	8.05	8.24	0.225	0.93	0.77
SD of DMI, kg/dc	0.92	1.00	0.96	1.01	0.029	0.11	0.07
Meal frequency, meals/d	11.4	12.1	12.0	11.1	0.43	0.32	0.41
Duration, min/meal	13.7	14.2	13.4	15.0	0.61	0.28	0.52
Intermeal interval, min	124.2	115.6	116.3	125.0	4.55	0.32	0.32
Meal size, kg/meal	0.77	0.73	0.72	0.79	0.036	0.46	0.60
Eating rate, g/min	56.8	51.9	55.1	53.7	1.86	0.31	0.14
Finishing
DMI, kg/d	10.6	11.0	10.6	10.5	0.23	0.34	0.64
SD of DMI, kg/dc	1.50	1.60	1.57	1.52	0.055	0.49	0.33
Meal frequency, meals/d	8.3	8.6	8.1	8.0	0.32	0.52	0.84
Duration, min/meal	9.5	10.2	10.4	10.6	0.52	0.51	0.31
Intermeal interval, min	180.2	172.0	182.5	186.8	7.77	0.53	0.97
Meal size, kg/meal	1.37	1.34	1.38	1.40	0.058	0.91	0.99
Eating rate, g/min	139.2	136.2	133.5	132.1	5.64	0.81	0.41

^an = 20 steers per treatment; individual steer was the experiment unit.

^bControl vs. EB = control vs. all EB treatments.

^cDay-to-day variation of DMI.

DISCUSSION

Similar DMI between treatments is consistent with previous studies (Tobioka and Garillo, 1994; Terry et al., 2019; Winders et al., 2019) that reported that EB did not affect intake in beef cattle fed high-forage or high-concentrate diets. Leng et al. (2012) found that there was a tendency of Bos indicus (Laos “yellow”) cattle fed biochar to have improved live weight gain (grams per day). The relatively small (80–100 kg) calves used different diet composition (cassava root chips and cassava foliage), as well as the low ADG (13 kg over 98 d) obtained by Leng et al. (2012) may account for the differences in response to biochar observed in our study. Similarly, Japanese brown cattle had increased growth rate when fed a high-concentrate diet supplemented with activated carbon. However, this response was not consistent across three experiments conducted by this group (Tobioka and Garillo, 1995).

The variability in animal response between studies may arise, in part, due to differences in biochar composition. Although varying biochar biomass, pyrolysis temperatures, doses, and posttreatments did not result in changes to in vitro rumen fermentation of hay or silage, differences in gas and volatile fatty acid (VFA) production among different types of biochar has been observed (Calvelo Pereira et al., 2014). Similarly, a fine particle size biochar was found to increase in vitro DM digestibility of orchard grass compared to coarse biochar, though not compared to the control (McFarlane et al., 2017). Differences in original biomass, pyrolysis temperature, and pretreatment and posttreatment can alter the chemical composition, surface area, pH, and porosity of EB. It is these factors that have been hypothesized to alter the rumen microbial environment, prompting caution in extrapolating observations across biochar products.

The minimal changes in the performance of cattle fed EB is supported by Terry et al. (2019) who demonstrated that ruminal metabolism, including total VFA production, microbial protein synthesis, and N retention, was not altered by EB. Similarly, biochar did not cause changes in nutrient digestibility of DM, ADF, or NDF in beef steers fed high-forage or high-grain diets (Winders et al., 2019). The use of the rumen simulation technique found that total VFA production was linearly increased with increasing inclusion of EB in a barley silage-based diet similar to the backgrounding diet used in the present study (Saleem et al., 2018). In contrast, using the same technique, Teoh et al. (2019) did not find any effect of a high dose of hardwood biochar on fermentation characteristics. Similar inconsistencies between in vitro and in vivo research were previously reported for other feed additives like humic substances (Terry et al., 2018a,, 2018b) and were attributed to differences in microbial populations, length of experimental adaptation period, and sampling environment (Terry et al., 2018a).

Although there was a significant treatment by period interaction observed for DMI, ADG, and G:F in backgrounding and finishing phases, these differences likely arose due to variation in gut fill with time of weighing during the day and, as such, are unlikely to be biologically significant. However, Tobioka and Garillo (1994) did observe an increase in daily gain of beef cattle supplemented with activated carbon within the first month of the experiment, but this effect did not persist to the end of the study.

The observed decrease in total weight gain and overall ADG by 2.0% EB can, in part, be attributed to the replacement of 2.0% of the TMR with EB, which appears to be largely indigestible within the rumen (Terry et al., 2019). Though there were no differences observed in NE_m or NE_g in the diets, the colonization and utilization of EB as an energy source is limited (Terry et al., 2020). Interestingly, the lean yield was increased by 2.0% EB compared to all other treatments. Similarly, 73.7% of carcasses were graded as Canada 1 for 2.0% EB compared to 40.5% for the control. This may be due to the numerically lighter HCW of EB 2.0% cattle, which also had reduced back fat. Additionally, 2.0% EB steers were numerically lighter at finishing (661 vs. 670 kg), likely reflecting a reduction in fat deposition.

The percentage of incidence of liver abscesses was numerically lowered by 1.0% and 2.0% EB, though the percentage of livers with severe abscess was higher in these groups. The percentage of abscessed livers in the present study are less than those previously reported in feedlot steers fed a barley-based finishing diet (Moya et al., 2011), although the severity of the abscesses is higher than previously reported. Alternatively, Ribeiro et al. (2016) reported that liver abscess incidence was, on average, 20% lower than in our study. These differences between studies may be attributed to the inclusion of monensin, an antibiotic that has been suggested to decrease the incidence of liver abscesses (Meyer et al., 2013). Unlike Ribeiro et al. (2016) and Moya et al. (2011), the present study did not include monensin in the diet, suggesting that EB cannot substitute for antibiotics as a means of liver abscess control.

Consistent with the present study, other studies have found that EB did not alter feed intake when supplemented into either forage- or grain-based diets. Although there was a tendency for a control versus EB effect on the SD of DMI, all eating behavior parameters were typical for cattle fed high-forage and high-concentrate diets (Moya et al., 2011; Ribeiro et al., 2016). Similarly, the tendency for steers fed 0.5% and 1.0% to have more meals per day with decreased intermeal interval did not seem to alter any other measured performance parameters.

In conclusion, EB did not result in changes in growth rate, feed efficiency, feeding behavior, or carcass quality in feedlot cattle, but 2.0% EB did increase lean carcass yield grade. Though EB was unsuccessful in promoting growth, there were no negative consequences of including EB in the diet below 1% DM.

ACKNOWLEDGMENTS

The authors wish to acknowledge the funding or in-kind support from the Agriculture Greenhouse Gases Program of Agriculture and Agri-Food Canada, Alberta Agriculture and Forestry-Project #2017R036R, Cool Planet, and Blue Rock Animal Nutrition. Cool Planet provided recommendations for product dosage and reviewed the final manuscript. The assistance of technical staff in analytical analyses and the barn staff in the care of the cattle at the Lethbridge Research and Development Centre is also gratefully appreciated.

Footnotes

1

This project was funded by Agriculture Greenhouse Gases Program of Agriculture and Agri-Food Canada, Alberta Agriculture and Forestry, Cool Planet, and Blue Rock Animal Nutrition. S.A.T. acknowledges Meat and Livestock Australia for their financial support during her PhD candidacy. The authors wish to thank Cool Planet and Lethbridge Research and Development Centre for technical support and animal care assistance, respectively.