Story in Brief

Seventy-five feedlot cattle in 15 pens were fed high concentrate diets supplemented with either 0 or 136 ppm Agrado (30 and 45 cattle, respectively) for 28 d prior to harvest. Added Agrado had little impact on gain, feed intake, or feed efficiency although rate and efficiency of gain tended to be improved slightly by supplemental Agrado. Lean maturity, an indicator of darkness of ribeye color, was reduced while USDA yield grade was increased slightly by feeding Agrado. Improvements in feed efficiency, reduced carcass maturity and liver abscess incidence should make Agrado useful as an additive for feedlot cattle.

(Key Words: Cattle, Performance, Agrado™, Gain Efficiency, Feedlot.)

Introduction

Feeding vitamin E, an antioxidant, at concentrations 10 to 100 times the amount required has improved feedlot performance slightly and has improved health of shipping-stressed cattle (Secrist et al., 1997). Unfortunately, vitamin E is rather costly; cost for supplementation is between $3 to $4 per animal. Whether other more economical antioxidants would improve cattle performance has received limited attention. In one study, lambs were fed diets containing 0, .01 and .1% ethoxyquin (DeMille et al., 1972); tissue concentrations of a compound presumed to be ethoxyquin reflected the amounts being fed. When ethoxyquin was fed to lactating dairy cows, milk contained elevated concentrations of a compound not separable from vitamin E. So whether Agrado fed to animals acts directly as an antioxidant or enhances absorption, activity, or stability of other antioxidants is not certain. Ethoxyquin is used commonly as an antioxidant additive for certain feed ingredients including fish meal, fat, and alfalfa meal; maximum concentration in feeds permitted by the FDA is 150 ppm (except for dog food where the maximum suggested concentration is 75 ppm). The objective of this study was to determine the impact of feeding Agrado at approximately 150 ppm on performance and carcass characteristics of feedlot cattle.

Materials and Methods

Treatments. A 121-d feeding study was conducted at the Progeny Test Barn at Oklahoma State University located near Stillwater, OK; Agrado treatments were imposed only during the final 28 d of this trial. Cattle that had been fed a high concentrate diet for 92 d previously and having an average full weight of 506 kg were divided into two groups. Each pen in one of these groups (5 cattle per pen) received no supplemental Agrado whereas the other group received 13 g top-dressed on their daily diet once daily. Preweighed plastic bags containing Agrado premix were poured onto and mixed with the fresh feed in the feed bunks once each day. On chemical analysis by Covance Laboratories, Madison, WI, the dry Agrado premix purchased from Nutra Blend Corp., Neosho, MO contained 52.8% ethoxyquin. This means that Agrado intake averaged 1.37 g daily per animal. Because feed intake for the final 35 d of the trial averaged 22.3 lb (10.1 kg) daily for cattle receiving Agrado, Agrado concentration, expressed as parts per million of diet dry matter, was 136 ppm for cattle receiving the Agrado supplement. Other diet ingredients included 82% rolled corn grain, 10% alfalfa meal pellets, and 7.8% of a protein-mineral-vitamin supplement that provided .5% dietary urea. No tylosin or Monensin™ was fed. Cattle received fresh feed once each day at 0830. For compiling the corn grain, alfalfa meal pellets and the pellet supplement, a Data Ranger™ feed delivery system was used. Based on the amount of feed remaining in the bunk from the previous day, the amount of fresh feed to add was adjusted each day to keep feed excess below 5% but avoid bunks being empty. Feed weights were recorded daily and summarized across each weighing period.

Cattle Management and Weighing. In this study, 75 cattle, predominately of British breeding from the Oklahoma State University cattle herd, were used; 45 cattle (9 pens with 5 animals in each pen) received the Agrado supplement while 30 cattle (6 pens with 5 animals in each pen) received no Agrado. Cattle were housed in partially covered pens (3.8 m by 16 m) equipped with automatic waterers and fence-line cement feed bunks with 76 cm (38 in) of linear bunk space per animal. Cattle were weighed individually at approximately 28 d intervals and again 2 d prior to harvest. For calculation purposes, final body weight was calculated as hot carcass weight assuming that dressing percentage was 62%. This calculation helps adjust for individual differences in gut fill and water intake and more precisely estimates sellable product.

Carcass Measurements and Sampling. On June 17, 1997, all cattle were loaded onto two semitrailer trucks and transported to Excel Inc., Dodge City, KS and harvested. Following exsanguination and hide removal, the animal identification tag was transferred from the ear to the carcass to maintain identity of each carcass in the meat cooler. Each liver was examined for presence and severity of abscesses. After carcasses were held at 4°C for 36 h, each carcass was ribbed (sliced at the 12th rib); quality grade, yield grade, ribeye area, marbling score, skeletal maturity, kidney-heart-pelvic fat percentage, and maturity of lean and bone were determined by University personnel for each carcass.

Statistical Analysis. Data were analyzed as a completely randomized design with two treatments; pen means were used for analysis of performance data.

Results and Discussion

Cattle Performance. Performance measurements were taken on days that did not correspond precisely with the 28 d period when Agrado was fed. The weigh day nearest to the day that Agrado was first fed (d 92) was d 84. Since Agrado was fed for 28 of the 37 d of this final period, responses during this period might be attributed to added Agrado. Live and carcass weights were not altered by Agrado supplementation although daily gain tended to be slightly greater (about 5%) for cattle fed Agrado during this final 37 d period (Table 1). No sorting or rejection of the small particles carrying Agrado was detected. Dry matter intakes were not different; consequently, the amount of feed required per unit of gain either on a live basis (119 d values) or a carcass adjusted basis (121 d values) slightly favored (7 to 10%) cattle receiving Agrado during this final period. Feed energy value, calculated from gain, mean weight, and feed intake, again tended to favor cattle fed Agrado when they were receiving this supplement. However, none of these performance differences were significant statistically due to the small number of pens of cattle in this experiment.

Carcass Differences. Only two carcass differences proved to be significant statistically (Table 2). First, maturity as judged by lean color was lower (lean color was brighter red) for cattle fed Agrado; skeletal maturity, an index of calcification of spinus processes, was not altered by Agrado feeding. Brighter lean color 48 h after harvest probably reflects an alteration in oxygen uptake or oxygen holding capacity by ribeye muscle tissue.

USDA Yield Grade, an index of carcass fatness that is dependent largely on fat thickness over the ribeye muscle, was slightly greater for cattle fed Agrado. This means that the cattle fed Agrado were slightly fatter than control cattle were. Likewise, a lower percentage of cattle fed Agrado fell in the leanest yield grade (1) while several more cattle fell in the less desirable and discounted yield grades (4 and 5). No explanation for this difference is apparent. Marbling scores also tended to be greater for cattle fed Agrado. The incidence of liver abscesses was very low for all cattle but tended to be slightly lower for cattle receiving Agrado. The USDA grader that examined each liver for presence of abscesses and flukes indicated that healthfulness of all the cattle was excellent with no apparent discoloration or defects. Studies with rats previously had indicated that rate of liver regeneration was greater for rats fed Agrado. Certain dog owners have alleged that ethoxyquin is responsible for liver malfunction in certain breeds of dogs. However, dogs would consume much more antioxidant than cattle because dogs have much higher feed intakes (4 vs 2% of body weight intake per d) and would consume such feeds for a much longer time period (lifetime vs 28 d) than the cattle used in this experiment.

Implications

Including Agrado at 138 ppm of the diet for 28 d prior to harvesting, feedlot cattle increased rate and efficiency of gain slightly and reduced lean maturity (ribeye color was brighter). Agrado also tended to increase carcass fatness and marbling scores.

Literature Cited

DeMille, F. et al. 1972. Can. J. Anim. Sci. 52:351.

Secrist, D.S. et al. 1977. Professional Anim. Sci. 13:47.

 

Table 1.  Effects of adding 150 ppm Agrado™ for the final 28 d on performance of finising beef cattle. (Agrado™ was fed only from 5/20 to 6/17/97).
Agrado™ added, ppm	0	150	% Change	Prob; P<
Cattle, number	30	45
Weights, lb
Live, d 0 (2/17/97)	729	716	-1.8	.27
Live, d 84 (5/12/97)	1125	1109	-1.4	.50
Live, d 119 (6/16/97)	1238	1229	-.7	.80
Carcass, d 121 (6/18/97)	760	756	-.5	.84
Daily gain, lb/d
0-119 d (live wt; 5% shrink)	3.76	3.79	.8	.87
0-121 d (carcass wt/dress %)	4.19	4.24	1.2	.75
84-119 d (Agrado™ began d 92)	3.09	3.26	5.2	.64
84-121 d (Agrado™ began d 92)	4.51	4.75	5.1	.45
Dry matter intake, lb/d
0-120 d	21.41	21.23	-.8	.80
84-120 d	22.72	22.26	-2.1	.67
Feed/gain
0-119 d	5.72	5.62	-1.8	.61
0-121 d	5.12	5.02	-2.0	.42
84-119 d	7.65	6.92	-10.5	.19
84-121 d	5.06	4.72	-7.2	.17
Diet metabolizable energy, Mcal/kg
0-121 d	2.92	2.94	.7	.71
84-121 d	2.76	2.87	3.8	.22

 

Table 2.  Effects of adding 150 ppm Agrado™ for final 28 d on carcass characteristics  of finishing beef cattle. (Agrado was fed only from 5/20 to 6/17/97).
Agrado added, ppm	0	150	Effect, %	Prob. P<
Dressing % (carcass wt/live wt*100)	61.4	61.5	0.2	.82
Skeletal maturity	153	153	0.0	.96
Lean maturity	153	142	-7.7	.02
Overall maturity	153	148	-3.4	.24
Marbling (400 = choice)	285	341	16.4	.40
Quality score	1.33	1.47	9.5	.46
Prime, %	0	6.7		.16
High choice, %	6.7	4.4		.75
Choice, %	13.3	4.4		.12
Select, %	73.3	71.1		.88
Percent above choice	26.7	28.9		.88
Rib eye area, sq in	13.9	13.6	-2.2	.34
Fat thickness, in	0.43	0.5	14.0	.16
Adjusted fat thick, in	0.51	0.57	10.5	.26
Kidney, heart, pelvic fat, %	2.17	2.26	4.0	.36
USDA Yield grade	2.27	2.67	15.0	.04
Final yield grade	2.64	2.88	8.3	.17
Yield grade 1, %	16.7	6.7		.13
Yield grade 2, %	53.3	48.9		.74
Yield grade 3, %	30	40		.49
Yield grade 4, %	0	4.4		.27
Liver abscesses, %	6.7	4.4	-52.3	.79