Effect of substitution of distillers grains and glycerin for steam–flaked corn in finishing cattle diets on growth performance and carcass characteristics

Abstract

An experiment was conducted to determine the effect of substituting modified corn distillers grains with solubles (DGS) or crude soy glycerin (CG) for steam–flaked corn (SFC) in finishing diets on growth performance and carcass characteristics. Treatments were arranged as a 2 × 2 factorial with DGS (0% or 40%) and CG (0% or 10%) replacing dietary SFC in a basal diet. Growth performance and carcass traits were measured on 48 individually fed crossbred yearling cattle (21 steers and 27 heifers; 380 ± 37 kg). Cattle were randomly allotted to 48 Calan gate bunks. After the first 28 days, nine animals were removed from the study for health reasons or observed confirmation of consumption of feed from unassigned Calan gate bunk (n = 39). After the feeding period, cattle were harvested in two groups on day-124 and day-173. No DGS × CG interactions were observed (P > 0.10) for any dependent growth performance or carcass characteristic variable tested. Cattle-fed DGS as 40% of diet dry matter (DM) had greater (P< 0.01) dry matter intake (DMI), while CG inclusion at 10% of diet DM did not affect DMI (P = 0.16). Carcass–adjusted average daily gain (ADG) was not affected by DGS (P = 0.73) or CG (P = 0.28). Decreased (P = 0.03) carcass–adjusted gain-to-feed (G:F) was observed as the main effect of DGS. Greater DMI resulting from feeding DGS as 40% of diet DM appears to have driven the tendency for reduced G:F. Hot carcass weight, longissimus muscle area, 12th rib fat depth, yield grade, and marbling score were not (P> 0.10) influenced by DGS or CG. However, kidney, pelvic, fat (KPH) was increased (P = 0.01) when cattle were fed DGS as 40% of diet DM. Based on the findings presented, it is concluded that CG can substitute up to 10% of SFC in the diet without negatively affecting cattle growth performance or carcass characteristics, regardless of DGS inclusion as 40% of the diet DM.

Glycerin can be substituted for 10% of the steam–flaked corn without influencing growth performance or carcass characteristics in finishing cattle diets containing 0% or 40% modified corn distillers grains with solubles.

Introduction

As the production of alternative energy sources increases, opportunities to feed co-products to cattle have increased as well. Feeding glycerin, a liquid co-product of the biodiesel industry, provides versatility while helping maintain diet integrity (Kholif, 2019). Parsons et al. (2009) observed a quadratic response in gain-to-feed (G:F) in finishing heifers fed crude glycerin (CG), with diminishing performance not observed until dietary inclusion of CG was greater than 4%. In a similar study, Van Cleef et al. (2019) reported no effect on average daily gain (ADG) when feeding CG included at 0, 7.5, or 15% of diet dry matter (DM),but a linear decrease in dry matter intake (DMI). This resulted in a concomitant improvement in G:F (Van Cleef et al., 2019). Results from a parallel in vitro experiment by Van Cleef et al. (2019) demonstrated a depression in DM disappearance when ruminal fluid had not been previously adapted to CG inclusion (15% of diet DM) and was then exposed to CG in vitro. This supported the findings of Kijora et al. (1998) that prior adaptation is needed to optimize CG utilization in the rumen. Beyond the effects of adaptation time, the influence of CG on DMI is not fully understood as suggested by the inconsistency in the literature (Parsons et al., 2009; Schneider et al., 2011; Hales et al., 2013a, 2013b; Weiss et al., 2017). It is the potential for improved growth performance efficiency when CG is included in the diet that has captured the interest of cattle nutritionists looking for versatility in feed ingredients. However, interactions with other ingredients (like those of fat and other co-products) should be considered when examining the influence of dietary inclusion of CG on cattle growth and carcass characteristics (Schneider et al., 2011; Buttrey et al., 2015; Weiss et al., 2017). Distillers grains research has been of interest due to the increased prevalence of the co-product in modern beef cattle diets. Previous experiments by Schneider et al. (2011) and Weiss et al. (2017) examined the interactive effects of low concentrations of CG and corn distillers grains with solubles (DGS). Neither determined the effects of CG on cattle growth or carcass characteristics. The current experiment expands on this research by examining higher dietary inclusions of both co-product ingredients. Our objective was to determine the effect of substituting modified DGS and CG for 40% or 10%, respectively, of steam–flaked corn (SFC) in finishing diets on growth performance and carcass characteristics.

Materials and Methods

All animals were cared for according to the guidelines of the University of Minnesota, Institutional Animal Care, and Use Committee (Minneapolis, MN), and all experimental procedures were reviewed and approved by Institutional Animal Care and Use Committee. The experiment was conducted at the University of Minnesota Beef Research Facility (Rosemount, MN).

Cattle, experimental design, and dietary treatments

Forty-eight Charolais–cross yearlings (21 steers and 27 heifers; initial body weight (BW) 380 ± 37 kg) were randomly assigned to bunks in a Calan gate individual feeding system. The Calan gate system consisted of 48 bunks (56 cm bunk space per animal) in four pens (12 Calan gates/pen). Dietary treatments were assigned randomly to Calan gate bunk within a pen with an intended total of 12 replicates per treatment (actual animals per treatment are presented in Table 1). Nine animals were removed from the study; one for health reasons and the others were confirmed outliers by observation of feed routinely being consumed from unassigned Calan gates. Observations were made and outliers were removed from the study within the first 28 days of the study. Dietary treatments were arranged as a 2 × 2 factorial with modified corn DGS and CG replacing 40% or 10%, respectively, of the SFC in the basal diet (Table 1). Steam–flaked corn (0.47 kg/L) was manufactured and delivered once to the research facility. Cattle were fed for ad libitum intake once daily at 0800 hours and orts were collected and sampled daily before feeding. A bunk score of 0 (scale: 0, empty to 4, full) for two consecutive days elicited a 0.23kg–DM increase in the amount of feed offered. Daily DMI was corrected using measured orts. Cattle were implanted on d 56 with 200 mg of trenbolone acetate and 20 mg of estradiol (Revalor 200 implant; Merck Animal Health, Madison, NJ).

Table 1.

Ingredient composition and nutrient analysis (% DM basis) of finishing diets

Item	Treatment diet1
	DGS-N CG-N	DGS-Y CG-N	DGS-N CG-Y	DGS-Y CG-Y
No. of animals	10	8	11	10
Ingredient(%)
Grass hay	11.7	10.6	11.6	10.3
Steam–flaked corn2	78.8	44.5	67.1	35.3
Modified DGS3	0.0	41.0	0.0	40.7
Soy glycerine	0.0	0.0	11.0	9.9
Liquid mineral supplement 4	4.0	3.6	3.9	3.6
Liquid protein supplement 5	5.3	0.0	6.1	0.0
Myco CURB 6	0.2	0.3	0.3	0.2
Calculated composition(%)
DM	80.7	69.8	78.1	71.4
CP	13.8	17.6	13.7	16.4
RDP	10.8	8.5	7.7	8.8
ADF	9.4	15.2	11.7	11.8
Ca	0.77	0.74	0.82	0.89
P	0.35	0.47	0.39	0.48
S	0.13	0.25	0.17	0.22
NEm, mcal/kg	2.05	2.23	2.03	2.22
NEg, mcal/kg	1.37	1.41	1.36	1.42

¹Treatment diets included: DGS-Y CG-N, containing 40% distillers grains and 0% soy glycerin; DGS-N CG-N, containing 0% distillers grains and 0% soy glycerin; DGS-Y CG-Y, containing 40% distillers grains and 10% soy glycerin; DGS-N CG-Y, containing 0% distillers grains and 10% soy glycerin.

²Flake density = 0.47 kg/L.

³Modified distillers grains with solubles (48% DM; Western Wisconsin Energy, Boyceville, WI).

⁴Liquid supplement containing 30% crude protein (100% from urea); 16% Ca, 0.1% P, 0.56% Mg, 2.05% K, and 0.49% S and Rumensin (959 g/Ton).

⁵Liquid supplement containing 52% crude protein (100% from urea).

⁶Mold inhibitor (Kemin Industries, Inc., Des Moines, IA).

Data collection and sample processing

Cattle were weighed every 28 days and initial BW was taken after a 1600-hour period without access to feed and water. Cattle were harvested in two groups on day-124 and day-173 when visual appraisal indicated approximately 1.3 cm of backfat at the 12th rib. All cattle were harvested at PM Beef (Windom, MN) and carcass data were collected by University and USDA personnel. Carcass data collection included hot carcass weight (HCW), marbling score, 12th–rib fat thickness, longissimus muscle area, kidney, pelvic, fat (KPH), USDA yield grade, and USDA quality grade.

Sample analysis

Feed and ort samples were dried overnight (or until dry) in a conventional drying oven at 55 ºC. Dry samples were ground through a 2-mm screen using a Thomas Model 4 Wiley Mill (Thomas Scientific, Swedesboro, NJ). Feed ingredients were analyzed individually for DM, organic matter (OM), crude protein (CP), and acid detergent fiber (ADF). Diet composition was calculated based on individual ingredient analyses (Table 1). Residual DM was measured at 105 ºC according to AOAC International (2005). Crude protein (CP) was determined via the Kjeldahl method in a 2300 Kjeltec analyzer unit (Foss Tecator AB, Höganäs, Sweden) (AOAC, 1990). An ANKOM 200 Fiber Analyzer (Ankom Corp., Fairport, NY) was used to determine ADF concentration according to the procedures of Van Soest et al. (1991). Minerals (Ca, P, and S) were analyzed via atomic absorption spectroscopy at Dairyland Laboratories, Arcadia, WI.

Based on visual behavior observation after the feed was delivered, the presence of outlier DMI data generated by cattle that consumed feed from an incorrect bunk or had feed consumed from their bunk by another animal was tested using the Regression procedure of SAS 9.4 (SAS Institute Inc., Cary, NC). The regression procedure led to the discovery of eight outliers, which were removed from the study. Data were then analyzed using a Mixed procedure of SAS with the animal being experimental unit. The effects of sex were permitted to be evaluated by the random effect of animals in the model. The statistical model was as follows:

$${\displaystyle \begin{array}{l}{\displaystyle {\mathrm{Y}}_{\mathrm{i}\mathrm{j}\mathrm{k}}=\mu +{\alpha }_{\mathrm{i}}+{\beta }_{\mathrm{j}}+\alpha \ast {\beta }_{\mathrm{i}(\mathrm{j})}+{\mathrm{A}}_{\mathrm{k}}+{\epsilon }_{\mathrm{i}\mathrm{j}\mathrm{k}}}\end{array}}$$

where Y_ijk = dependent variable, μ = population mean, α_i = ith effect of dietary distillers grains inclusion, β_j = jth effect of dietary glycerin inclusion, α*β_i(j) = interaction between ith effect of distillers grains and jth effect of glycerin, A_k = random kth effect of animal, and ε_ijk = residual error. Effects were considered significant when P values were less than or equal to 0.05 and were considered trends when P values were between 0.05 and 0.10.

Results and Discussion

Cattle performance

No DGS × CG interactions (P > 0.10) were observed for any dependent growth performance variable which was tested (Table 2). Final BW (P = 0.42) and carcass–adjusted ADG (P = 0.73) were not affected by 40% dietary inclusion of DGS. A decreased (P = 0.03) carcass–adjusted G:F is suggested to be influenced by the observed increase (P < 0.01) in DMI for treatment diets that included DGS compared to diets without DGS (Table 2). Nuttelman et al. (2011) report differences in feed intake with the inclusion of different types of DGS and report that cattle fed dried or modified corn DGS, at the same dietary concentration, had greater intake compared to those fed wet DGS. Dietary inclusion rates of wet DGS at 20%, 30%, and 40% of diet DM resulted in increased intake compared with negative control (Nuttelman et al., 2011). However, Veracini et al. (2013) observed a quadratic decrease in DMI over a 244-d feeding period when modified corn DGS were fed at 0%, 25%, 40%, and 70% dietary inclusion. Not all literature reports a consistent DMI increase to DGS inclusion in the diet (Ham et al., 1994; Lodge et al., 1997; Buckner et al., 2008; Depenbusch et al., 2009). These differences may stem from co-product manufacturing differences, inaccuracies when reporting the nutrient composition of the co-product utilized, as well as differences in the ingredients being replaced by DGS in the diet.

Table 2.

Main effects of DGS or CG on carcass adjusted finishing performance

Item	DGS1		CG2		SEM3	P-value
	No	Yes	No	Yes		DGS	CG	DGS ×CG
Initial BW(kg)	386	370	377	380	8	0.21	0.77	0.97
Final BW(kg)	586	575	583	578	10	0.42	0.74	0.96
DMI(kg/d)	8.43	9.97	9.53	8.89	0.32	<0.01	0.16	0.24
ADG(kg)	1.42	1.39	1.45	1.37	0.05	0.73	0.28	0.49
G:F 4(kg/kg)	0.16	0.14	0.15	0.15	0.008	0.03	0.57	0.11

¹DGS treatment diets included: No, containing 0% distillers grains; Yes, containing 40% wet distillers grains.

²CG treatment diets included: No, containing 0% soy glycerin; and Yes, containing 10% soy glycerin.

³SEM = Standard error of the mean.

⁴G:F = weight gain per feed consumed.

Previous research on the effects of dietary inclusion of CG has presented variable responses in DMI (Parsons et al., 2009; Schneider et al., 2011; Hales et al., 2013a, 2013b; Weiss et al., 2017). In the present experiment, no effect (P = 0.16) of CG for DMI was observed (Table 2). Hales et al. (2013a, 2013b) published a series of experiments with CG in receiving and finishing cattle, where both neutral and negative intake responses were reported. Parsons et al. (2009) observed a quadratic effect for DMI when heifers were fed 0%, 2%, 4%, 8%, 12%, and 16% CG. While Schneider et al. (2011) and Weiss et al. (2017) observed no DMI response in diets with varying inclusion of glycerin and corn co-products. Final BW (P = 0.74) and carcass–adjusted ADG (P = 0.28) were not affected in the current study by the main effect of CG (Table 2). Hales et al. (2013a) fed crude CG (0%, 2.5%, 5%, 7.5%, and 10% of diet DM) in SFC diets and observed a quadratic response in final BW (P = 0.09) and ADG (P = 0.04). The quadratic response showed that BW and ADG peaked when CG inclusion was 7.5% of diet DM (Hales et al., 2013a). Hales et al. (2013a) also discussed differences in dietary energetic value when CG replaced various ingredients in the diet, demonstrating that both diet composition and ingredient concentration in the diet can impact CG effects on growth performance. In the current experiment, carcass–adjusted G:F was not affected (P = 0.57) by 10% dietary inclusion of CG. These results are expected given the observed responses for DMI, ADG, and final BW already discussed. Parsons et al. (2009) reported that G:F decreased when dietary CG inclusion was at 4% inclusion or above, yet other literature (Schneider et al., 2011; Hales et al., 2013b; Buttrey et al., 2015; Weiss et al., 2017) reported no effects on G:F. Variation in DMI for CG in the literature may be attributed to the source of CG, methanol concentration of CG, and dietary energy differences. Further research is needed to better understand which dietary interactions are driving observations (or lack thereof) in the literature.

Carcass characteristics

No interactions (P> 0.10) between DGS and CG were observed for any dependent carcass characteristic variables tested. The main effect of dietary DGS inclusion did not affect hot carcass weight (P = 0.43), longissimus muscle area (P = 0.62), 12th rib fat depth (P = 0.63), yield grade (P = 0.22), or marbling score (P = 0.63; Table 3). Larson et al. (1993) and Lodge et al. (1997) both observed no change in carcass characteristics when DGS replaced cereal grains in the diet. Depenbusch et al. (2009) observed that HCW responded quadratically when cattle were fed diets with an increasing concentration of DGS (0%, 15%, 30%, 45%, 60%, and 75%, DM basis), while no other carcass characteristics (dress yield, LM area, 12th–rib fat, USDA yield grade, marbling score, or USDA quality grade) were affected. Greater (P < 0.01) KPH for cattle-fed DGS in the current experiment agrees with the linear increase in KPH when DGS inclusion increased as reported by Depenbusch et al. (2009).

Table 3.

Main effects of feeding DGS or CG on carcass traits

Item	DGS1		CG2		SEM3	P-value
	No	Yes	No	Yes		DGS	CG	DGS× CG
HCW(kg)	373	366	371	368	6	0.43	0.74	0.93
12th–rib back fat(cm)	0.21	0.22	0.22	0.22	0.01	0.63	0.87	0.34
Longismuss muscle area(cm2)	83.2	82.1	82.3	83.0	1.5	0.62	0.75	0.13
KPH	2.4	3.0	2.5	2.6	0.1	0.01	0.42	0.91
USDA yield grade	2.6	2.8	2.7	2.6	0.1	0.22	0.57	0.29
Marbling4	424	434	435	424	17	0.63	0.62	0.30

¹DGS treatment diets included: No, containing 0% distillers grains;and Yes, containing 40% wet distillers grains.

²CG treatment diets included: No, containing 0% soy glycerin; and Yes, containing 10% soy glycerin.

³SEM = Standard error of the mean.

⁴where 400 = small⁰⁰, 500 = modest⁰⁰.

Hot carcass weight, longissimus muscle area, 12th–rib fat depth, yield grade, and marbling score were not (P> 0.10) affected by dietary inclusion of CG. Long et al. (2015) observed no differences in 12th–rib fat depth, KPH, yield grade(YG), or longissimus muscle area, but did see differences in marbling when CG was included (10% and 20% of diet DM) in growing cattle diets. Parsons et al. (2009) reported linear decreases for longissimus muscle area, 12th rib fat, and marbling with increased dietary CG inclusion (0%, 2%, 4%, 8%, 12%, and 16 % of diet DM) in finishing cattle diets. Results from Parsons et al. (2009) suggest that optimal dietary inclusion of CG is 8% or below in finishing diets, and above a concentration of 8% of diet DM, effects on growth and carcass performance were deleterious. However, like the present study, Buttrey et al. (2015) and Weiss et al. (2017) found no effect of feeding glycerin on growth performance or carcass characteristics when CG was included in SFC diets above the 8% threshold suggested by Parsons et al. (2009). This may suggest that other unconsidered factors may influence cattle response to CG inclusion in the diet.

In the present study, growth performance and carcass characteristics were not influenced by an interaction of DGS and CG at the ingredient concentrations fed. Based on these results it is concluded that at 10% and 40% of the diet DM respectfully, CG and DGS could be effective substitutions in SFC finishing diets when market price permits. An increase in DMI when DGS is included at 40% of diet DM appears to drive the differences seen in growth performance. Further research is needed to better understand any potential interactive effects of different inclusion rates of CG with other dietary ingredients on cattle growth performance as well as better understand any changes occurring in ruminal fermentation.

Glossary

Abbreviations

ADF

acid detergent fiber

ADG

average daily gain

BW

body weight

CG

crude soy glycerin

CP

crude protein

DGS

corn distillers grains with solubles

DM

dry matter

DMI

dry matter intake

G:F

gain-to-feed

HCW

hot carcass weight

KPH

kidney, pelvic, fat

OM

organic matter

SFC

steam–flaked corn

YG

yield grade

Conflict of Interest Statement

The authors declare no real or perceived conflicts of interest.