Cupplant Silage as a Replacement for Corn Silage in Growing Beef Cattle Diets

Jeffrey W. Lehmkuhler and Marcelo H. Ramos, Department of Animal Sciences, and Kenneth A. Albrecht, Department of Agronomy, University of Wisconsin-Madison 53706

Abstract

Forage and grain crops utilized by the livestock industry are subject to failure under some environmental conditions. The objective of this trial was to investigate the potential for cupplant (Silphium perfoliatum L.) to fill gaps in livestock feed resource chains. Dietary treatments investigated were 0, 30, and 60% cupplant silage replacing corn (Zea mays L.) silage. Increasing the inclusion level of cupplant silage from 0 to 30% and 60% resulted in a decline in average daily gain (ADG) for weaned beef calves of 12 and 44%, respectively. However, with yearling beef cattle, no differences in ADG or gain efficiency were observed as cupplant silage level increased in diets. Diet dry matter (DM) and organic matter (OM) intakes and neutral detergent fiber (NDF) digestibilities were reduced with increasing levels of cupplant silage. Our results show that cupplant silage can be utilized as an alternative forage source to replace a portion of the corn silage in beef calf rations; however, it will reduce ADG.

Cupplant Silage Fills Ecological Niches

Livestock industries in the north-central USA depend on conserved forage for winter feeding, and alfalfa (Medicago sativa L.) and corn silage have proven to be the most productive and dependable sources. The danger of depending on a few plant species for winter feed is brought to the forefront by extensive alfalfa winter-kill events and other weather-induced crop failures. Identification of forage crops to fill ecological niches prone to crop failure would reduce risk faced by the livestock industry.

Cupplant is indigenous to mesic regions of the North American prairie (4) and tolerates short-term flooding. Forage dry matter yields range from four to six tons per acre from cupplant harvested one or two times per season (1) and winter damage has not been observed over a period of 15 years (K. A. Albrecht, unpublished observations). Standing cupplant contains greater than 80% water and wilting is required to obtain lactic acid fermentation end products in silage (6). Cupplant silage was found to have 29 to 38% NDF and in vitro DM digestibility ranging from 52 to 70% with digestibility characteristics similar to that of alfalfa silage (5,6). There are little animal performance data for cupplant forage; therefore, the objective of this research was to compare the feeding value of cupplant silage as a replacement for corn silage in growing beef cattle diets.

Production and Harvest of Cupplant Silage

Cupplant was grown from bulked seed after allowing crossing of a collection of 26 Wisconsin, Illinois, Minnesota, and Iowa ecotypes. Cupplant and corn fields near Arlington, WI (43°18’N, 89°21’W) were fertilized to maintain P and K levels in the optimum range for corn silage (7) and ammonium nitrate was applied to provide 150 lb N per acre each spring. Cupplant was harvested at the early flower stage in early July and field wilted to a target of 65% moisture before chopping and ensiling in a concrete stave silo. Corn for silage was harvested after the half kernel milk-line stage when whole plants were approximately 65% moisture.

Project Descriptions and Data Analysis

Feeding trial experiments were approved by the University of Wisconsin College of Agriculture and Life Sciences Animal Care and Use Committee. In Experiment 1, 36 weaned crossbred beef steer calves (538 lbs ± 34) were stratified by weight and assigned to one of nine pens allowing for similar weights among pens. Dietary treatments consisted of 100% corn silage (CS), 70% CS : 30% cupplant silage (LC), and 40% CS : 60% cupplant silage (HC) replicated three times in a completely randomized design. Steers were weighed on two consecutive days before feeding at the initiation and end of the trial to calculate ADG. Single day weights were recorded on days 34 and 67. Dietary treatments were offered for 100 days (4 December 2003 to 23 March 2004) once daily in the morning as a total mixed ration (Table 1). Bunks were initially managed following a slick bunk protocol. After it was noted that large pieces of cupplant stem were being left, the HC cattle were allowed approximately 8 lb of refusal daily. Feed refusals were weighed daily and subtracted from feed delivered to calculate DM intake.

Table 1. Dietary ingredient levels of total mixed rations fed to growing beef cattle in all three experiments.

Ingredient	Percent of DM
	Corn silage	30% cupplant	60% cupplant
Corn silage	89	59	30
Cupplant silage	—	30	59
Supplement	11	11	11
	Supplement composition
Soybean meal	86.2
Calcium carbonate	4.30
Choice grease	2.20
Salt	1.72
Urea	1.72
Vitamin ADE premix	1.72
Rumensin 6.5% premix	1.72
Trace mineral premix	0.42

Feed samples were dried in a forced air oven at 130°F, ground, and stored for subsequent analysis. Dry matter concentration was determined by drying samples in a 212°F oven for 24 h. Ash concentration was determined following incineration at 932°F for 24 h in a muffle furnace. Neutral detergent fiber was determined with the inclusion of α-amylase and Na₂SO₃ and acid detergent fiber (ADF) was determined sequentially on diet samples (ANKOM²⁰⁰ Fiber Analyzer, ANKOM Technology Corp., Fairport, NY). Nitrogen concentration of diets was determined by thermoconductivity (LECO FP 528 Nitrogen Analyzer, Leco Instruments Inc., St. Joseph, MI) with crude protein (CP) estimated by multiplying nitrogen percentage by 6.25. Diet energy concentrations were estimated using beginning and end weights along with observed DM intake values (9).

The same dietary treatments were offered to 24 yearling steers and 12 yearling heifers (787 lbs ± 43) in Experiment 2 in the same facilities used for Experiment 1. Cattle had been previously grazing a cool-season perennial grass and clover pasture. Cattle were blocked by sex, stratified by weight, and assigned to one of nine pens that allowed for the initial average pen weight to be similar within blocks. This resulted in one pen of heifers and two pens of steers per dietary treatment. Due to limited cupplant silage availability, treatment diets were offered for 60 days (25 August 2005 to 27 October 2005). Animals were managed and data collected similarly to Experiment 1 with a single day weight taken on day 33.

Experiment 3 utilized four crossbred steer calves (mean BW 584 lb) in a 3 × 3 Latin square with an extra observation to study the digestibility of cupplant silage. Steers were housed in individual pens in a temperature-controlled facility (76°F) with 12 h of light and 12 h of darkness. The trial consisted of three 8-day periods with 5 days for diet adaptation and 3 days of sample collection. Diets offered utilized the same feedstuffs as in Experiment 2 as Experiments 2 and 3 occurred simultaneously. Feed was delivered twice daily at 0800 and 1400 and offered ad libitum. Feed refusals were weighed and a sub-sample was dried to correct for DM intake and analyzed for NDF to determine daily NDF intake. Gelatin capsules containing 0.18 oz of TiO₂ were administered at 0800 and 2000 daily. During the 3-day collection period, fecal samples were collected every 6 h with collection times advanced 2 h on subsequent days. This resulted in samples representing 2-h intervals in a 24-h clock to account for diurnal variations in passage rates. Fecal samples were immediately frozen for storage and later thawed and dried for 48 h at 130°F. Daily feed and fecal samples were composited by treatment within each period. Fecal Ti concentration was measured colormetrically (8) and fecal samples were analyzed for DM and NDF as described above. During the 3-day collection period approximately 0.1 lb of feed and refusals were collected, stored frozen and later composited by period, dried for 48 h at 130°F and analyzed as described above.

Data from Experiment 1 were analyzed as a completely randomized design. The MIXED procedure of SAS (SAS Institute Inc., Cary, NC) was used with treatment included as a fixed effect and pen as a random variable in the model. The LSMEANS statement was utilized to generate means and standard errors for mean comparisons. Variables in Experiment 2 were analyzed as a randomized block design with sex and treatment included as fixed effects while pen (treatment × sex) was included as a random effect. Because sex and the interaction of treatment by sex were not significant, only the main effects of treatment are reported for Experiment 2. Data from Experiment 3 were analyzed as a Latin square design. The model included treatment as a fixed effect and period and steer as random effects. Linear and quadratic orthogonal contrasts were utilized for mean comparisons in all experiments. Differences were considered significant at P < 0.05. Quadratic contrasts were not significant in Experiments 2 or 3 and only linear contrasts are reported.

Responses for Weaned Beef Steers in Experiment 1

Chemical composition differed among dietary treatments (Table 2). Neutral detergent fiber and ADF were unusually low in the corn silage and addition of cupplant increased these constituents in the diet. Crude protein concentrations, however, were similar across diets. As cupplant silage level increased, NDF and ADF concentrations were greater, reflecting lowered non-structural carbohydrate concentrations as corn silage was replaced. Average daily gains for diets containing cupplant silage decreased linearly for all periods (Table 3). A quadratic response in ADG was observed for the entire feeding period with gains being reduced dramatically for the high inclusion level of cupplant silage. Dry matter intake declined linearly as the level of cupplant silage increased. Dry matter intake expressed as a unit of body weight again responded quadratically for cupplant diets with DM intake of HC being 8 to 9% lower than CS and LC. Gain efficiency also decreased linearly as cupplant inclusion increased.

Table 2. Nutrient composition (%) of diets fed to growing beef calves and yearling cattle during Experiments 1, 2, and 3.

Experiment	Diet constituent*	CS	STDEV	LC	STDEV	HC	STDEV
1	DM	46	2.4	49	1.8	50	1.2
	CP	10.5	0.89	10.0	0.91	10.5	1.0
	NDF	28.9	3.63	36.8	3.6	43.0	2.5
	ADF	18.8	7.6	22.8	3.5	25.0	3.3
2 and 3	DM	51	1.52	42	1.21	39	2.00
	CP	9.9	0.78	11.4	1.12	13.0	0.98
	NDF	39.3	2.00	38.3	1.44	42.5	2.6
	ADF	21.0	1.00	22.6	1.30	26.4	2.12

* DM = dry matter, CP = crude protein, NDF = neutral detergent fiber, ADF = acid detergent fiber, CS = corn silage, LC = 30% cupplant silage, HC = 60% cupplant silage, STDEV = standard deviation.

Table 3. Performance of growing beef calves fed diets containing varying levels of cupplant silage in Experiment 1.

Average daily gain (lb)	Treatment^x			SEM^y	Linear^y	Quadratic^y
Average daily gain (lb)	CS	LC	HC	SEM^y	Linear^y	Quadratic^y
Period 1	3.04	2.65	1.74	0.09	<0.001	0.06
Period 2	2.71	2.23	1.26	0.15	<0.001	0.25
Period 3	3.51	3.28	2.27	0.18	0.003	0.13
Overall	3.06	2.69	1.72	0.09	<0.001	0.05
DM intake (lb/day)	14.2	14.0	11.8	0.4	0.008	0.09
DM intake (% body weight)	2.00	2.04	1.85	0.02	0.004	0.007
Gain efficiency (lb/lb)	0.22	0.19	0.15	0.005	<0.001	0.22

^x CS = Corn silage, LC = 30% cupplant silage, and HC = 60% cupplant silage treatments.

^y SEM = standard error of the mean, Linear = P value for linear contrast, Quadratic = P value for quadratic contrast.

Yearling Beef Cattle Responses to Cupplant Silage in Experiment 2

The cupplant silage utilized for Experiments 2 and 3 had a higher CP concentration than corn silage as indicated by the increasing dietary protein with increased cupplant inclusion level (Table 1). Neutral detergent fiber concentration of CS was also greater in these trials and closer to expected values for corn silage-based diets. Neutral detergent fiber and ADF concentrations were greater in the diet containing 60% cupplant silage than in the other two diets, but addition of cupplant had much less effect on these constituents than in Experiment 1. This is because fiber concentrations in the corn silage were only slightly lower than that in cupplant in this experiment (data not shown).

Increased proportions of cupplant silage did not affect ADG, DM intake or gain efficiency of yearling cattle (Table 4), although a trend for lower ADG (P = 0.14) and gain efficiency (P = 0.10) were observed. When expressed as a percentage of body weight, DM intake tended (P = 0.07) to increase linearly as cupplant silage increased. This higher DM intake would partially offset the lower energy density of HC. The lack of differences in ADG and gain efficiency among diets could be a result of the relatively short feeding period (60 vs 100 days) combined with compensatory growth of yearling animals. Additionally, the higher NDF level in the corn silage-based diets in this experiment may also partially explain the lack of differences.

Table 4. Performance of yearling beef cattle in Experiment 2 consuming
diets containing varying levels of cupplant silage.

Average daily gain (lb)	Treatment^x			SEM^y	Linear^y
Average daily gain (lb)	CS	LC	HC	SEM^y	Linear^y
Period 1	3.15	2.29	2.25	0.40	NS
Period 2	2.82	2.69	2.01	0.33	NS
Overall	3.00	2.49	2.14	0.31	NS
DM intake (lb/day)^z	18.0	17.8	18.6	0.3	NS
DM intake (% body weight)	2.04	2.04	2.16	0.03	0.07
Gain efficiency (lb/lb)	0.17	0.14	0.11	0.02	0.10

^x CS = Corn silage, LC = 30% cupplant silage, and HC = 60% cupplant
silage treatments.

^y SEM = standard error of mean, Linear contrast P value where
NS = not significant.

^z DM = dry matter.

As the proportion of cupplant silage in the diets increased, DM intake and diet energy concentrations were reduced, leading to lower gains for steer calves but not yearlings. Reductions in calculated energy densities of the diets were similar for Experiments 1 and 2, with net energy for gain (NEg) values for LC being 89% and HC 77% that of CS (data not shown). Upon regressing the calculated NEg for the diets, it was estimated that cupplant silage had NEg values of 41 and 32 Mcal/cwt for calves and yearlings, respectively. The thick, coarse stem of cupplant resulted in large particle size and refusals with the 60% cupplant silage diets. Others have reported interactions between particle length and DM intake in beef cattle and dairy cows (2,3) which may partially explain the observed lower intakes by calves. This depression in dry matter intake was not observed for the yearling cattle. Dry matter intake has been shown to increase with steer age at entry into feedlots along with a reduction in gain efficiency (10) agreeing with trends observed in these reported experiments.

Digestibility of Diets Containing Cupplant Silage in
Experiment 3

The intakes of DM and OM were greater when calves consumed the CS diet compared to diets containing cupplant silage (Table 5). Intakes followed the same pattern as in Experiment 1, which also used calves as test animals. Dry matter intake for calves was approximately 20% greater for CS than HC. A linear increase in NDF intake was observed as a result of increased NDF concentration in diets containing cupplant silage. Diet DM, OM and NDF digestibility decreased linearly as the proportion of cupplant silage increased in the diets. Organic matter digestibility averaged 18% lower for diets containing cupplant silage than CS while NDF digestibility averaged 36% lower for diets containing cupplant silage. The combined factors of reduced DM intake and digestibility resulted in a non-linear reduction in performance which limits the dietary inclusion level of cupplant silage if high rates of gain are desired in growing cattle.

Table 5. Digestibility and intake by growing beef calves of diets fed in Experiment 3 with varying levels of cupplant silage.

Diet^z	Treatment^x			SEM^y	Linear^y
Diet^z	CS	LC	HC	SEM^y	Linear^y
OM (%)	89.3	86.4	83.7	0.60	0.003
DM intake (lb/d)	13.0	11.7	10.9	0.9	0.003
OM intake (lb/d)	11.6	10.1	9.2	0.8	0.004
NDF intake (lb/d)	7.2	6.7	6.5	0.6	0.008
DM digestibility (%)	70.0	57.1	53.5	3.7	0.03
OM digestibility (%)	71.2	59.9	57.2	3.5	0.05
NDF digestibility (%)	58.5	38.5	35.5	5.8	0.05

^x CS = Corn silage, LC = 30% cupplant silage, and HC = 60% cupplant silage treatments.

^y SEM = standard error of the mean where number of observations equals four. Linear = P value for linear contrast.

^z DM = dry matter, OM = organic matter, NDF corrected = neutral detergent fiber of feed consumed adjusted for NDF content in refusals.

Summary

Although utilization of cupplant as a forage crop offers an opportunity to reestablish native vegetation on agricultural landscapes, its value as a livestock feed is less than that of corn silage. Cupplant silage can be utilized as an alternative forage in beef cattle diets, but the diets will be lower in digestibility and reduce animal performance compared to corn silage. Therefore, inclusion levels of cupplant silage will be dependent upon targeted body weight gains. Use of cupplant silage may be ideally suited for cattle in which dietary energy needs to be limited such as replacement dairy heifers and backgrounding of beef cattle.

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