Effects of replacing corn silage with alfalfa haylage in growing beef cattle diets on performance during the growing and finishing period

Abstract

Corn silage is the predominant mechanically harvested forage source for feedlot cattle production in the United States because of high yield. Alternatively, because of multiple cuttings per year and lower annual cost, the use of alfalfa or other forages, may increase opportunities for manure spreading, perennial soil cover, pollinator habitat, and greater carbon sequestration. The objective of this trial was to determine the feeding value of alfalfa haylage when replacing corn silage in growing cattle diets. One-hundred-sixty-five Angus crossbred steers [326 ± 51 kg of body weight (BW)] were blocked by initial BW and randomly assigned to one of 28 pens at the University of Minnesota feedlot. Pens were randomly assigned to dietary growing treatments. The control diet was comprised of (DM basis) 50% corn silage, 19.25% rolled corn grain, 19.25% high moisture corn, 7% dried distillers grains plus solubles, and 4.5% liquid supplement (corn silage control, CS Control). For alfalfa haylage (AH) diets, AH substituted corn silage at 33% (AH 33), 66% (AH 66), or 100% (AH 100). Growth performance measurements [dry matter intake (DMI), average daily gain (ADG) and gain to feed (G:F) ratio] were assessed for 42 to 70 d depending on BW block. Afterwards, steers were fed a common finishing diet until harvested. There was a linear increase in DMI (P < 0.01) with increasing AH inclusion. Replacing CS with AH linearly decreased (P ≤ 0.05) ADG and G:F. No differences (P ≥ 0.10) were observed in finishing performance or carcass traits. Results from this study demonstrated that greater substitution of corn silage with alfalfa haylage in growing diets resulted in greater intake but reduced rate of gain and gain:feed. Despite slower rate of gain, cattle fed alfalfa haylage at increasing proportions during the growing period were able to compensate in BW gains during the finishing period and reached harvest weight and backfat thickness at similar days on feed than those fed corn silage. Based on these results the energy value of corn silage and alfalfa haylage were 3.05 and 2.39 Mcal ME/kg of DM, respectively, when included at 50% of the diet DM.

There is an opportunity to increase alfalfa acreage to enhance beef systems through ecosystem services while increasing revenues per hectare through reduced crop costs and greater periods of time to spread manure from beef cattle operations.

Introduction

In growing diets, roughage inclusion levels are a function of target average daily gain (ADG) and are fed for a variety of reasons including to reduce fat deposition over this period, and to decrease the cost of gain (Fox and Tedeschi, 2002). Alfalfa hay and corn silage are two of the most common roughage sources used in growing and finishing cattle in the United States (Galyean and Gleghorn, 2001; Vasconcelos and Galyean, 2007; Samuelson et al., 2016). Nonetheless, corn silage has replaced alfalfa hay and haylage as the major forage fed to high-producing beef and dairy cattle (Erdman et al., 2011).

Growing cattle diets in the U.S. Midwest may range from 0% to 67% inclusion of silage (DM basis), averaging 22.2% (Asem-Hiablie et al., 2016), with corn silage being the primary silage source (Samuelson et al., 2016). Corn silage with 30% to 50% grain, typically provides additional starch to the diet (25% to 35% of the DM when harvested at 32% to 35% DM or even greater concentrations when harvested at greater maturity; Ferraretto et al., 2015), which requires consideration particularly in growing diets where there is a target ADG defined by economic and environmental conditions, and where fat deposition is not the main objective (Peel, 2003). Starch consumption, which is a fermentable energy source, can affect meal patterns and feed intake via the hepatic oxidation theory (Allen et al., 2009). As intake in beef cattle fed grain-based diets is typically controlled primarily by metabolic factors and not limited by bulk fill, small increases in the concentration of bulky roughage can increase dry matter intake (DMI) by finishing cattle (Galyean and Defoor, 2003). Thus, the percentage of neutral detergent fiber (NDF) supplied by roughage in growing and finishing diets accounts for most of the variation in DMI caused by roughage. Changes in NDF sources can affect the energy density of the diet, and therefore animal intake, as cattle consume dry matter to maintain a constant metabolizable energy (ME) intake (Krehbiel et al., 2006). The growing period permits using various forage sources and byproducts which can be cost effective, while contributing to adjusting rates of gain to reach market weights at optimum weight and degree of finish. This practice in turn helps adjust both the timing and volume of cattle harvest, in a complex market environment where flexibility in rates of gain is important. Thus, the decision on the inclusion of forage sources for growing diets needs to be considered in the context of a production system, where revenue per unit of land area, fertilization costs and manure value, soil cover, as well as animal performance and marketing opportunities are at play. Considering all this, alfalfa haylage could play a role in beef production systems due to its protein quality and its associated benefits in terms of ecosystem services (Fernandez et al., 2019).

Several experiments conducted in dairy cows demonstrated that corn silage, alfalfa haylage/silage, or mixtures of these two roughage sources can provide adequate nutrition to support production (Thomas et al., 1970; Belyea et al., 1975; Grieve et al., 1980; Sauer et al., 1980; Erdman et al., 2011). However, scarce information exists comparing the replacement of corn silage with alfalfa haylage on nutrient digestibility and performance of growing beef cattle, as most experiments were conducted decades ago and in dairy cattle, with forage varieties that do not represent the potential of the current production systems.

The main objective of this study was to compare the feeding value of alfalfa harvested as haylage vs. corn silage when fed at the same dietary concentration, by assessing nutrient digestibility and growth performance of beef cattle. A secondary objective was to determine if the increased replacement levels of corn silage by alfalfa haylage during the growing period have an impact on finishing performance and carcass characteristics of Angus crossbred steers, as roughage source can affect DMI and NE_g intake, ultimately affecting finishing performance and carcass characteristics (Defoor et al., 2002). We hypothesized that a greater substitution of alfalfa haylage for corn silage would sustain similar animal performance and carcass traits due to its effect on DMI. Should alfalfa haylage be deemed a suitable partial or full replacement for corn silage in growing cattle diets, this could potentially lead to an increase in the planted area for alfalfa. As a perennial forage, alfalfa can sequester large quantities of carbon and provide winter soil cover (Autret et al., 2016), enhancing whole-farm nutrient cycling ­(Martin et al., 2017). A potential increase in alfalfa land area in beef systems could allow feedlots greater flexibility in field manure spreading throughout the growing season, improving nutrient management in beef cattle operations (Yost et al., 2014).

Materials and Methods

This experiment was conducted at the feedlot of the Beef Research and Education Complex at the Rosemount Research and Outreach Center, University of Minnesota, Rosemount, MN. All research procedures were reviewed and approved by the University of Minnesota, Institutional Animal Care and Use Committee (Protocol number 1805-35897A).

Animals, treatments, and diets

One-hundred-sixty-five Angus crossbred steers [12 ± 2 months of age, 326 ± 51 kg of body weight (BW)] were used in a randomized complete block design. Ninety-six steers (group 1) arrived at the feedlot in mid-April 2021, while seventy steers (group 2) arrived in mid-May 2021. Steers were blocked (4 blocks for group 1: light, medium-light, medium-heavy, and heavy; 3 blocks for group 2: light, medium, and heavy) by initial BW and assigned randomly to one of 28 pens (24 m²/pen) in a deep-bedded confinement barn (5 to 6 steers/pen, minimum of 50 cm/steer of linear bunk space). Pens were randomly assigned to one of four dietary treatments (7 pens/treatment), which consisted of growing diets in which alfalfa haylage replaced corn silage as the roughage ingredient. The corn silage control diet (CS Control) consisted of (DM basis) 50% corn silage, 19.25% rolled corn grain, 19.25% high moisture corn, 7% dried distillers grains plus solubles, and 4.5% of a supplement to meet protein, vitamin and mineral requirements of growing steers. Alfalfa haylage (AH) diets were formulated to substitute corn silage at 33% (AH33), 66% (AH66), or 100% (AH100).

The experimental (growing) period consisted of a 14-d adaptation to facilities and pens, followed by a 42- to 70-d growing period, depending on initial block or group. Cattle were procured from two sources (Group 1 and Group 2). Lot size (95 steers) and weight variation were greater for cattle derived from Group 1; therefore, four initial blocks were generated. Cattle from Group 2 (70 steers) were divided into three initial blocks. Cattle from Group 2 and heavy and medium-heavy cattle from Group 1 were grown for 42 d. Medium-light and light cattle from Group 1 were grown for 56 and 70 d, respectively. Growing periods were intended to reduce weight differences observed at initial body weight, a common practice in cattle feedlots. Afterwards, animals were adapted to high concentrate diets over 14 d by increasing inclusion of corn grain and decreasing forage inclusion. Then, cattle were fed a common finishing diet for 141 d to 171 d depending on group arrival and block allocation until slaughter. Cattle were evaluated by visual appraisal to determine harvest dates. Estimation of fat cover at 1.25 cm or greater over the loin for 50% or more cattle per pen was considered reflective of harvest readiness. Cattle were scheduled for harvest at two dates only two days apart. This resulted in cattle from Group 2 being finished for 141 d and heavy cattle from Group 1 being finished for 169 d. Light, medium-light, and medium-heavy cattle from Group 1 were finished for 143 d, 157 d, or 171 d, respectively. Steers were harvested at a ­commercial abattoir where hot carcass weight (HCW), longissimus muscle area (LMA), backfat (BF), marbling score (MB), and USDA quality and yield grade were obtained by instrument grading.

Ingredient and chemical composition of the diets are shown in Tables 1 and 2. Ingredients were sampled weekly to correct for DM differences and adjusted accordingly. Diet samples were collected from the bunks every 7 d, dried at 55 °C, ground to pass a 2-mm screen, and composited by pen. Diet samples and ingredients were analyzed for nutritional composition by a commercial laboratory (Dairy One Forage Laboratory, Ithaca, NY) through wet chemistry procedures for concentrations of crude protein (CP), NDF, acid detergent fiber (ADF), starch, and total digestible nutrients (TDN) using the procedures described in their July 2022 update (https://dairyone.com/download/forage-forage-lab-analytical-procedures). The Penn State Particle Separator with sieves of 19.0, 8.0, 1.8 mm, and a pan was used (Kononoff et al., 2003; Heinrichs, 2013) to characterize particle size distribution of the diets (Table 2) weekly during the growing period starting on week 2.

Table 1.

Analyzed¹ chemical composition of the ingredients (DM basis) of diets fed to Angus crossbred steers

Item3	Ingredient2
	CS	AH	HMC	DRC	DDGS
DM, %	34.93	58.91	63.25	88.66	90.12
CP, %	8.70	19.60	7.50	8.00	32.00
EE, %	3.82	2.60	4.44	3.98	10.11
Ash, %	4.65	13.81	1.47	1.39	5.38
Soluble CP, % CP	45.00	52.00	55.00	15.00	16.00
ADF, %	24.50	38.30	2.10	3.50	17.00
aNDF, %	35.80	45.00	6.70	8.20	34.80
Lignin, %	3.00	8.00	0.30	0.90	4.20
NFC, %	47.00	19.00	80.00	79.10	17.70
Starch, %	32.00	2.70	75.10	69.10	4.00
TDN, %	73.00	54.00	91.00	88.00	81.00
NEm, Mcal/kg	0.79	0.48	1.04	1.00	0.94
NEg, Mcal/kg	0.50	0.23	0.72	0.69	0.64

¹Dairy One Forage Testing Laboratory, Ithaca, NY.

²CS, corn silage; AH, alfalfa haylage; HMC, high moisture corn; DRC, dry rolled corn; DDGS, dry distillers grain plus solubles. Ingredient samples were collected every week and composited for the entire trial.

³DM, dry matter; CP, crude protein; EE, ether extract; Sol. CP, soluble crude protein; ADF, acid detergent fiber; aNDF, neutral detergent fiber corrected with alpha-amylase; NFC, non-fibrous carbohydrates; TDN, total digestible nutrients calculated as: (CP digestibility × CP) + (FA × 2.25) + 0.98 × (100—CP—Ash—EE) – 7; NE_m, net energy of maintenance; NE_g, net energy of gain.

Table 2.

Ingredient and nutrient composition¹ on a DM basis of dietary treatments fed to Angus crossbred steers

Item	Treatment2				Finishing
	CS Control	AH33	AH66	AH100
Ingredients3
Corn silage	50.00	33.35	16.65	–	12.3
Alfalfa haylage	–	16.65	33.35	50.00	–
HMC	19.25	19.25	19.25	19.25	46.3
DRC	19.25	19.25	19.25	19.25	30.8
DDGS	7.00	7.00	7.00	7.00	8.1
Liquid supplement	4.50	4.50	4.50	4.50	2.4
Nutrient composition4
DM, %	47.7	52.6	58.6	66.1	64.4
CP, %DM	12.50	14.90	15.90	17.50	12.2
RDP, %CP	61.4	61.1	60.7	60.4	56.7
EE, %DM	3.98	4.01	3.70	3.52	3.8
NDF, %DM	23.2	24.7	26.3	27.8	12.6
ADF, %DM	14.5	16.8	19.1	21.4	6.3
Lignin, %DM	2.0	2.9	3.7	4.5	1.1
Ash, %DM	3.3	4.8	6.3	7.8	2.1
Starch, %DM	44.0	39.2	34.3	29.4	58.8
TDN, %	78.3	75.2	72.0	68.8	84.6
NEm, Mcal/kg	1.92	1.81	1.69	1.58	2.12
NEg, Mcal/kg	1.25	1.15	1.05	0.95	1.44
Particle size, mm
>19.0	35.1	27.8	24.1	19.2	–
19.0–8.0	28.9	30.2	30.4	29.9	–
8.0–1.8	32.1	34.2	34.8	38.7	–
<1.8	4.0	7.8	10.7	12.2	–

¹Dairy One Forage Testing Laboratory, Ithaca, NY.

²CS Control, corn silage was 50% DM of diet; AH33, alfalfa haylage replacing 33% of the corn silage; AH66, alfalfa haylage replacing 66% of the corn silage; AH100, alfalfa haylage replacing 100% of the corn silage, representing 50% DM of the diet.

³HMC, high-moisture corn; DRC, dry-rolled corn; DDGS, dry distillers grain plus solubles; Liquid supplement, QLF core max 50 (Quality Liquid Feed, WI), main ingredient cane molasses.

⁴DM, dry matter; CP, crude protein; RDP, rumen degradable protein (using Streptomyces griseus (SGP) enzymatic digestion shown in Dairy One analytical procedures June 2022); EE, ether extract; NDF, neutral detergent fiber; ADF, acid detergent fiber; TDN, total digestible nutrients calculated as: (CP digestibility × CP) + (FA × 2.25) + 0.98 × (100 − CP − Ash − EE) − 7; NE_m = net energy of maintenance; NE_g, net energy of gain.

Performance

Throughout the trial, to adjust feed delivery, bunk scores were assessed every morning at 0800 h for each pen based on visual appraisal using the following scoring system: 0 = empty bunk; 0.1 = 1 to 5% of feed delivered remaining in bunk; 0.5 = 5% to 10% feed remaining; 1 = 10% to 20% of feed delivered; 2 = 20% to 30% of feed remaining; and 3 = >30% of feed remaining. Feed deliveries were reduced by estimates of feed remaining in the bunk when bunk scores were 1.0 or greater. Feed deliveries were increased by 0.22 kg DM/head upon two consecutive daily bunk readings of 0 score. If present, orts were taken each morning before feeding, weighed, and subsampled for DM determination. Steers were fed once daily with a vertical mixing wagon (800 Series 270, Patz, Pound, WI). Feed offered was weighed daily and recorded using a data recording software (Performance Livestock Analytics, Ames, Iowa) connected to the feeding wagon.

Steers were implanted with 24 mg of estradiol, 140 mg of trenbolone acetate, and 29 mg tylosin tartrate (Component TE-S with Tylan, Elanco Animal Health, Greenfield, IN) on d 1 of the growing period. All steers received a slow-release delivery implant containing 200 mg of trenbolone acetate and 40 mg estradiol at the end of the growing period.

At each respective start or end weight date, cattle were weighed after withdrawing feed and water for 16 h to determine BW to minimize effects of gut fill. Interim unshrunk BW were taken every 14 d at 0700 h. Dry matter intake, average daily gain (ADG), and gain to feed (G:F) ratio were assessed as measurements of animal performance. Changes in BW were calculated by subtracting the initial BW measurement from the final BW. Pen intake was calculated daily by subtracting orts from feed delivered. Feed delivery and refusals were corrected to a DM basis. The number of animals housed per pen was multiplied by number of days in the period to determine animal days, which were divided into the corrected total DM delivered to the pen to obtain average DMI per steer. One steer was removed from the growing period, and four others were removed during the finishing period due to sickness. Their intakes were back calculated considering their last BW measurement, and the amounts were removed from the pen intake for the time the steer was in the pen.

The net energy (NE) for each diet was calculated from performance data using the equation proposed by Zinn and Shen (1998) based on pen intake and ADG. Energy gain (EG) was calculated as EG = (0.0635 × EBW^0.75) × EBG^1.097, where EG is daily energy deposited (Mcal/d), EBW is empty body weight, calculated as shrunk body weight × 0.891, and EBG is empty average daily gain calculated as shrunk ADG × 0.956 (NASEM, 2016). The ­equation used to ­calculate maintenance energy expended (EM; Mcal/d) was EM = 0.077 × BW^0.75 (Lofgreen, 1968). From the calculated amounts of energy required for maintenance and gain, Net Energy of maintenance (NE_m) of each diet was obtained by the quadratic equation NE_m = [–b ± (b² − 4ac)^1/2]/2a, where a = –0.41 × EM, b = 0.877 × EM + 0.41 × DMI + EG, and c = –0.877 × DMI (Zinn and Shen, 1998). Net Energy of gain (NE_g) of each diet was obtained by the equation NE_g = 0.877 × NE_m—0.41 (Zinn and Shen, 1998). Energy values for corn silage and alfalfa haylage were determined using an iterative process as suggested by Owens et al. (1984) where the iterated ME concentrations were similar to ME concentrations calculated from diet composition. Relationships between ME, NE_m, and NE_g concentrations adopted by NASEM (2016) were utilized in these calculations.

Apparent total tract digestibility of nutrients

Apparent total tract digestibility of dry matter (DM), organic matter (OM), CP, starch, NDF, and ADF was measured in each pen using indigestible NDF (iNDF) as a marker. Feed and fecal samples were collected three times per day during a 4-d period, staggering collections by 2 h each day to cover an 8-h period of collection each day. For group 1, feed and fecal samples were collected from d 37 to d 42 on feed and for group 2, samples were collected on d 14 to 19. Feed samples were collected from bunks and fecal samples were collected directly from steers by rectal grab or from the pen floor when animals defecated avoiding contamination. Every morning before sampling, pens were scraped to facilitate the sampling and avoid fecal contamination. At every sampling point, fresh fecal samples from three to five animals per pen were collected and stored in a bag of their respective pen. After collection, feed and fecal samples were immediately placed on ice until transport to the laboratory. Feed and fecal samples were then frozen at −20 °C until further analysis. At the end of the experiment, feed and fecal samples were thawed and dried at 55 °C for 72 h in a forced-air oven and then ground in a Willey mill (Arthur H. Thomas Co., Philadelphia, PA) to pass a 2-mm screen. Feed and fecal samples were composited on an equal weight basis, per pen, for determination of nutrient and internal marker concentration.

For feed and fecal DM and OM determination, 0.5 g of each sample were weighed in duplicate, dried in a forced-air oven at 100 °C for 24 h, and ashed at 550 °C for 6 h. For determination of the fibrous component, samples were weighed in duplicate into F57 bags (Ankom Technology Corp., Macedon, NY) and analyzed for NDF, using heat-stable α-amylase and sodium sulfite, and subsequently for ADF in an Ankom 200 Fiber Analyzer (Ankom Technology Corp) as described by Van Soest et al. (1991). Nitrogen concentration in samples was analyzed through the Dumas dry-combustion method using a Vario Micro Cube (Elementar, Manchester, UK), after samples were ball-milled using a Mixer Mill MM400 (Retsch, Haan, Germany) at 25 Hz for 9 min.

For iNDF determination, 0.5 g of sample were weighed in duplicate into F57 bags (Ankom Technology Corp), incubated in the rumen of a cannulated steer consuming a 50:50 forage to concentrate diet for 288 h, rinsed with tap water until runoff was clear, dried at 60 °C overnight, and incubated in an Ankom 200 Fiber Analyzer (Ankom Technology Corp) as described by Cole et al. (2011) with the modifications proposed by Krizsan and Huhtanen (2013). Apparent total tract digestibility of DM, OM, NDF, ADF, starch and CP were calculated using the following formul:

$${\displaystyle \begin{array}{l}{\displaystyle 100-(100\times \frac{iNDFconcentrationinfeed}{iNDFconcentrationinfeces}\times \frac{nutrientconcentrationinfeces}{nutrientconcentrationinfeed})}\end{array}}$$

Statistical analyses

Data were analyzed as a randomized block design using the MIXED Procedure of SAS (SAS Institute Inc., Cary, NC). Pen was considered the experimental unit (n = 7 per treatment) and the model included the fixed effects of alfalfa haylage inclusion. Group and block nested within group were considered random effect. The proportions of cattle in each USDA quality grade were analyzed with the GLIMMIX procedure of SAS (binomial proportion), with the ILINK option used to calculate the treatment proportions and SEM. Orthogonal polynomial contrasts, adjusted for unequal spacing of treatments using the IML procedure of SAS, were included to compare the linear and quadratic effects of haylage inclusion on digestibility of nutrients, performance, and carcass traits of steers. Results were considered significant when P ≤ 0.05 and trends were considered when 0.05 < P < 0.10.

Results

During the apparent total tract digestibility measurements, there was a linear increase in DMI (P = 0.01), OM intake (P = 0.01), NDF intake (P = 0.04), and ADF intake (P < 0.01) with increasing AH inclusion, while CP intake increased quadratically (P = 0.03) with increasing AH inclusion (Table 3). There was a linear decrease in DM and OM digestibility with increasing alfalfa haylage inclusions (P < 0.01), where DM digestibility and OM digestibility decreased 19% and 16%, respectively, from Control CS to AH100. There was a quadratic decrease in CP digestibility (P = 0.02) as AH inclusion increased, decreasing from 71.4% in CS Control to 61.19% and 61.44% in AH66 and AH100, respectively. There was a linear decrease in NDF digestibility (P = 0.03) with increasing AH inclusion, but no effect on ADF digestibility (P ≥ 0.10).

Table 3.

Apparent total tract digestibility of growing diets with increasing levels of alfalfa haylage replacing corn silage when fed to Angus crossbred steers

	Treatment1					P—value2
Item3	CS Control	AH33	AH66	AH100	SEM4	Linear	Quad
Intake, kg/d
DM	8.7	8.5	9.1	9.2	0.41	<0.01	0.09
OM	8.2	7.9	8.4	8.4	0.42	0.05	0.18
CP	1.1	1.2	1.5	1.7	0.03	<0.01	0.03
NDF	2.3	2.4	2.6	2.7	0.10	<0.01	0.79
ADF	1.2	1.3	1.7	1.9	0.05	<0.01	0.69
Digestibility, %
DM	74.4	68.9	62.9	60.2	1.69	<0.01	0.32
OM	76.0	71.0	65.4	64.0	1.69	<0.01	0.21
CP	71.4	64.2	61.2	61.5	1.84	<0.01	0.02
NDF	54.0	51.1	46.0	47.2	2.93	0.03	0.39
ADF	49.6	51.3	49.6	52.5	2.50	0.54	0.81

¹ CS Control, corn silage was 50% DM of diet; AH33, alfalfa haylage replacing 33% of the corn silage; AH66, alfalfa haylage replacing 66% of the corn silage; AH100, alfalfa haylage replacing 100% of the corn silage, representing 50% DM of the diet.

²Observed significance levels for main effects of treatment (replacement) and orthogonal contrasts.

³DM, dry matter; OM, organic matter; CP, crude protein; NDF, neutral detergent fiber; ADF, acid detergent fiber.

⁴Pooled standard error of treatment, n = 7 pens/treatment.

Regarding animal performance during the growing period, a linear effect for lower final BW (P < 0.01) was observed as AH inclusion increased (Table 4). There was a linear increase in DMI (P < 0.01) as AH inclusion increased. Conversely, there was a linear decrease in ADG (P < 0.01) and G:F (P < 0.01) with increasing AH inclusion in accordance to the linear decrease in dietary NE_m and NE_g with greater AH inclusions.

Table 4.

Effect of replacing corn silage with increasing levels of alfalfa haylage during the growing period on the growth performance of Angus crossbred steers during the growing and finishing periods

	Treatment1					P—value2
Item3	CS Control	AH33	AH66	AH100	SEM4	Linear	Quad
Growing
Initial BW, kg	346	344	341	344	25.1	0.57	0.38
Final BW, kg	435	431	424	418	18.6	≤0.01	0.88
DMI, kg/d	7.9	8.0	8.1	8.3	0.32	≤0.01	0.90
ADG, kg	1.92	1.81	1.75	1.54	0.073	≤0.01	0.40
G:F, kg/kg	0.242	0.226	0.216	0.187	0.0081	≤0.01	0.34
Diet NEm5, Mcal/kg	2.16	2.07	1.99	1.90	0.035	≤0.01	0.84
Diet NEg5, Mcal/kg	1.48	1.41	1.33	1.26	0.030	≤0.01	0.86
CS6 ME, Mcal/kg	3.05	–	–	–	–	–	–
AH6 ME, Mcal/kg	–	2.70	2.51	2.39	0.608	–	–
Finishing
Interim7 BW, kg	435	431	424	418	10.6	≤0.01	0.88
Final BW, kg	655	654	646	655	22.6	0.79	0.50
DMI, kg/d	9.7	9.8	9.8	10.2	0.60	0.12	0.46
ADG, kg	1.47	1.48	1.48	1.55	0.121	0.17	0.48
G:F, kg/kg	0.152	0.151	0.152	0.152	0.0055	0.96	0.88
Overall
DMI, kg/d	9.04	9.41	9.38	9.84	0.423	0.01	0.83
ADG, kg	1.58	1.57	1.55	1.57	0.105	0.73	0.72
G:F, kg/kg	0.174	0.167	0.164	0.159	0.0050	0.01	0.75

¹CS Control, corn silage was 50% DM of diet; AH33, alfalfa haylage replacing 33% of the corn silage; AH66, alfalfa haylage replacing 66% of the corn silage; AH100, alfalfa haylage replacing 100% of the corn silage, representing 50% DM of the diet.

²Observed significance levels for main effects of treatment and orthogonal contrasts.

³BW, body weight; DMI, dry matter intake; NDF, neutral detergent fiber; ADF, acid detergent fiber; NE_m, net energy of maintenance; NE_g, net energy of gain; DOF, days on feed.

⁴Pooled standard error of treatment, n = 7 pens/treatment.

⁵Calculated net energy of maintenance and net energy of gain based on performance.

⁶Metabolizable energy of corn silage (CS) and alfalfa haylage (AH) was calculated from performance using the iterative procedure suggested by Owens et al. (1984). The ME of AH (test ingredient) was calculated using the ME of corn silage (3.05 Mcal/kg of DM) which was calculated from control pens only (no AH fed).

⁷Interim weight was the shrunk BW at the end of the backgrounded period and the beginning of the finishing period.

There was no effect of growing dietary treatment on DMI (P ≥ 0.10), ADG (P ≥ 0.10), final BW, or G:F (P ≥ 0.10) during the finishing period (Table 4). When evaluating the overall performance of the steers (considering the growing and the finishing period), there was a linear increase in DMI (P < 0.01) with increasing AH inclusion. Overall ADG of the steers was not different between treatments (P ≥ 0.10), but overall G:F decreased linearly (P < 0.01) as AH inclusion during the growing period increased (Table 4).

Decision to harvest cattle was based on predicting that 50% or more of the cattle in each pen had reached 1.25 cm of fat depth over the loin as appraised visually. Light cattle from Group 1 averaged 1.22 cm of fat while cattle from all other blocks, regardless of Group, averaged 1.48 cm or greater fat cover (data not tabulated). Also, proportion of carcasses grading Choice or better was 87% or greater for each treatment.

Hot carcass weight was not affected by treatment (P ≥ 0.10; Table 5). However, there was a quadratic effect (P = 0.03) in yield grade. There were no linear or quadratic effects (P ≥ 0.10) observed in backfat, longissimus muscle area, or marbling (P ≥ 0.10) among treatments (Table 5). No differences were observed for USDA quality grade distributions between treatments (P ≥ 0.10; Table 5).

Table 5.

Effect of replacing corn silage with increasing levels of alfalfa haylage during the growing period on carcass characteristics of Angus crossbred steers

	Treatment1					P-value2
Item3	CS Control	AH33	AH66	AH100	SEM4	Linear	Quad
HCW, kg	415	415	410	416	14.1	0.92	0.57
YG	2.88	3.23	2.95	2.90	0.109	0.55	0.03
LMA, cm2	97.2	98.9	95.8	98.1	2.65	0.95	0.85
BF, cm	1.47	1.66	1.43	1.46	0.081	0.41	0.22
MB5	495	523	504	507	46.9	0.75	0.32
USDA quality grade
Select, %	12.4	6.4	7.1	8.6	5.41	0.60	0.41
Low Choice, %	57.6	42.9	57.1	53.8	13.86	0.97	0.56
Upper 2/3 Choice, %	24.8	44.8	31.0	28.8	16.54	0.91	0.19
Prime, %	5.2	5.9	4.8	8.8	5.24	0.63	0.73

¹ CS Control, corn silage was 50% DM of diet; AH33, alfalfa haylage replacing 33% of the corn silage; AH66, alfalfa haylage replacing 66% of the corn silage; AH100, alfalfa haylage replacing 100% of the corn silage, representing 50% DM of the diet.

²Observed significance levels for main effects of treatment and orthogonal contrasts.

³HCW, hot carcass weight; YG, yield grade; LMA, longissimus muscle area; BF, back fat; MB, marbling score.

⁴Pooled standard error of treatment, n = 7 pens/treatment.

⁵MB, Marbling score: Slight⁰⁰ = 300; Small⁰⁰ = 400; Modest⁰⁰ = 500; Moderate⁰⁰ = 600; Slightly abundant⁰⁰ = 700.

Discussion

Corn silage is the predominant forage source for intensive beef and dairy cattle production in the United States (Johnson et al., 1999; Samuelson et al., 2016; Ferraretto et al., 2018). However, dependence on a single roughage source can lead to additional risk for cattle operations, which results from greater production costs and lower availability when there are weather events, or increases in input (fuel, seed, fertilizer) prices.

Alfalfa hay or haylage and corn silage are considered complementary forages, as they fit well in a crop rotation for managing nitrogen, pests, nutrient cycling, and soil health (Dhiman and Satter, 1997). From a cattle-feeding standpoint, the use of these two forages in a diet can lead to a more complete intake of nutrients, as alfalfa haylage is high in both CP and rumen degradable protein, while corn silage is a source of fermentable carbohydrates but is low in CP (Brito et al., 2006). Therefore, greater microbial protein synthesis could be expected by feeding optimal proportions of these sources, as proposed by Brito et al. (2006), which could lead to greater performance and lower costs by decreasing protein supplementation in beef cattle operations. Therefore, replacing corn silage with alfalfa as haylage for growing beef cattle diets contributes to managing risk and costs (Borton et al., 1997), while increasing dietary protein concentration (Dhiman and Satter, 1997).

The results observed on intake in this experiment are consistent with published literature exchanging corn silage with alfalfa hay or haylage in the diets of dairy cows; however, little information existed on the feeding value of alfalfa as haylage in growing beef cattle diets. Grieve et al. (1980) observed greater feed intake of dairy cows when alfalfa hay replaced corn silage in agreement with other authors (Waugh et al., 1955; Rumsey et al., 1963; Brown et al., 1965; Lessard and Fisher, 1980), and with the findings in this experiment. The linear increase in feed intake in this experiment, as alfalfa haylage inclusion increased, is in agreement with the observations by Galyean and Defoor (2003) and Krehbiel et al. (2006), where decreased dietary energy concentration in grain-based diets lead to increased intake. This is because intake in high-grain diets is typically controlled by metabolic factors rather than by bulk fill (Galyean and Defoor, 2003). This increase in intake observed when corn silage is replaced with alfalfa haylage is consistent with the decrease in the dietary energy density explained by Krehbiel et al. (2006), where increasing the concentrate to roughage ratio decreased DMI, so that ME intake remains constant.

As intake increased and ADG decreased, G:F also linearly decreased with greater alfalfa haylage inclusions. It is noteworthy that the alfalfa haylage used in this experiment had greater DM concentration (58.9%) than most direct-cut and wilted alfalfa haylage. Despite poorer performance by steers fed AH100, when calculated from performance, the ME concentration of alfalfa haylage in this treatment was 2.39 Mcal/kg of DM, which is 12% greater than ME concentration reported in the most recent NASEM (2016) publication for this forage source.

Apparent total tract digestibility of nutrients in this experiment demonstrated that greater inclusions of AH in replacement of corn silage linearly decreased the digestibility of DM, OM, and NDF by 19%, 16%, and 15%, respectively, from CS control to AH100. This linear decrease in nutrient digestibility with greater replacement levels of CS with AH may be related to the effect on DM intake. Greater intake would reduce ruminal retention time, and therefore reduce digestibility, particularly for the fiber components. This is particularly evidenced by the linear decrease in NDF digestibility as AH replacement for corn silage increased. The lack of differences in total tract digestibility of ADF, while intriguing, may be related to intrinsic differences in the composition of the ADF fraction in alfalfa haylage relative to that of corn silage.

The dietary treatments in the growing period did not affect the finishing performance and carcass traits of steers. Despite poorer performance by steers fed increasing inclusions of AH during the growing period, this was not reflected on carcass weight or traits. Cattle in all weight blocks finished at the same physiological end point, likely because days on feed in the growing period were adjusted based on initial BW. Across treatments the USDA Quality grade was 87% Choice or better.

Borton et al. (1997) performed economic and systemic analyses to compare the merits of corn silage and alfalfa in terms of net return above feed and manure costs. They recommended the utilization of at least one-third of each forage to provide the best results in terms of reducing the risk of crop loss, spread labor requirements more uniformly, and make a better use of on-farm nutrients.

There is opportunity to potentiate beef production systems through the utilization of alfalfa to sustain animal performance during the growing period without altering carcass characteristics during the finishing period. These possibilities could increase the acreage of alfalfa in beef systems, enhancing ecosystem services that this perennial crop provides, such as covering the soil for longer periods, providing pollinator habitat, increasing carbon fixation, and offering a greater number of opportunities to spread manure during the crop growing season (Gregorich et al., 2001; Autret et al., 2016; Martin et al., 2017; Fernandez et al., 2019). All these associated benefits should begin to be considered when comparing corn and alfalfa as possible roughage feedstuffs for beef cattle operations and when calculating the productivity of these systems per unit of land area.

Conclusions

Results from the current study demonstrated that greater substitution of corn silage with alfalfa haylage resulted in greater intake but reduced rate of gain during the growing period. Despite slower rate of gain, cattle fed alfalfa haylage at increasing proportions during the growing period were able to achieve adequate BW gains during the finishing period and reached harvest weight and endpoint at similar days on feed than those fed corn silage. Based on these results the energy value of corn silage and alfalfa haylage were 3.05 and 2.39 Mcal ME/kg of DM, respectively, when included at 50% of the diet DM. These energy values are greater than those recorded in previous publications (NASEM, 2016).

Glossary

Abbreviations

ADF

acid detergent fiber

ADG

average daily gain

BW

body weight

CP

crude protein

DDGS

dried distillers’ grains plus solubles

DM

dry matter

DMI

dry matter intake

DRC

dry rolled corn

EBG

empty average daily gain

EBW

empty body weight

EG

energy gain

FBW

final body weight

G:F

gain to feed

HMC

high moisture corn

iNDF

indigestible neutral detergent fiber

NDF

neutral detergent fiber

NE

net energy

NE_g

net energy of gain

NE_m

net energy of maintenance

OM

organic matter

SEM

standard error of the treatment mean

Conflict of Interest Statement

The authors declare no real or perceived conflicts of interest.