Animal Sciences Research and Reviews

Special Circular 156

Effects of Corn Processing and Dietary Fiber Source on Lamb Feedlot Performance and Tissue Accretion Rates

S. Hejazi and F.L. Fluharty
Department of Animal Sciences

Summary

High-concentrate diets containing whole corn can improve lamb performance and lean tissue accretion compared with diets containing primarily ground, pelleted corn. Additionally, both soybean hulls and peanut hulls (as supplemental fiber components) can improve dry matter intake (DMI) and average daily gain (ADG) compared with high-concentrate diets lacking supplemental fiber.

Introduction

Processing methods, such as grinding and pelleting, are used to increase the digestibility of corn vs feeding the grain whole (Nocek and Tamminga, 1991). However, when corn grain is processed, the ruminal pH is lower during the first 9 hours after feeding compared with whole corn (Murphy et al., 1994). If there are fluctuations in feed intake coupled with low ruminal pH, there is the possibility of acidosis and bloat. Therefore, feeding some dietary fiber with high-concentrate diets may be beneficial through increased saliva. This would occur because the buffering capacity of saliva maintains a stable ruminal pH. Furthermore, different sources of fiber may alter energy availability to the animal. The objectives of this experiment were to determine the effects of feeding high-concentrate diets containing either whole shelled corn (WSC) or ground corn, with either no dietary fiber, a highly digestible fiber (soybean hulls, SBH), or a relatively indigestible dietary fiber (peanut hulls, PH) on lamb performance, visceral organ weight, rate of visceral organ accretion, and carcass characteristics.

Experimental Procedures

One-hundred-twenty-six early weaned (average 50 days of age) Targhee and Polypay crossbred lambs (initial body weight = 53 pounds + 2 pounds) were used in a 2 x 3 factorial experiment to determine the effects of corn processing (whole vs ground and pelleted) and dietary fiber source (none [control], SBH, or PH) on animal performance, visceral organ mass and accretion, and carcass characteristics. Composition of the diets is shown in Tables 1 and 2. Diets were formulated to meet the dietary nutrient requirements during two different stages of the feeding period (NRC, 1985). Period 1 diets were fed until the lambs in a treatment group achieved an average weight of 79 pounds. Period 2 diets were fed starting when lambs reached 79 pounds and continued to be fed until lambs reached terminal weight (100 to 110 pounds for ewes and 105 to 115 pounds for rams). Diets were formulated to provide equal daily intakes of vitamins, minerals, urea, ammonium chloride, and lasalocid across treatments.

Table 1. Composition of diets fed to lambs weighing 53 to 79 pounds.
Item	Whole corn/ no fiber	Pelleted corn/ no fiber	Whole corn/ peanut hulls	Pelleted corn/ peanut hulls	Whole corn/ soybean hulls	Pelleted corn/ soybean hulls
	(%, Dry matter basis)
Whole corn	70.000	. . .	60.000	. . .	70.000	. . .
Ground corn	15.641	85.641	15.211	75.211	6.011	76.011
Peanut hulls	. . .	. . .	10.000	10.000	. . .	. . .
Soybean hulls	. . .	. . .	. . .	. . .	10.000	10.000
Soybean meal	5.700	5.700	5.840	5.840	5.440	5.440
Blood meal	2.850	2.850	2.920	2.920	2.720	2.720
Corn gluten meal	2.850	2.850	2.920	2.920	2.720	2.720
Urea	0.400	0.400	0.400	0.400	0.400	0.400
Limestone	1.300	1.300	1.300	1.300	1.300	1.300
Dicalcium phosphate	0.250	0.250	0.250	0.250	0.250	0.250
Monosodium phosphate	. . .	. . .	0.150	0.150	0.150	0.150
Trace mineral salt	0.450	0.450	0.450	0.450	0.450	0.450
Vitamin A, 30,000 IU/g	0.010	0.010	0.010	0.010	0.010	0.010
Vitamin D, 3,000 IU/g	0.010	0.010	0.010	0.010	0.010	0.010
Vitamin E, 44 IU/g	0.030	0.030	0.030	0.030	0.030	0.030
Selenium, 201 ppm	0.090	0.090	0.090	0.090	0.090	0.090
Ammonium chloride	0.400	0.400	0.400	0.400	0.400	0.400
Lasalocid, 67.5 g/pound	0.019	0.019	0.019	0.019	0.019	0.019
Calculated composition
Crude protein, %	17.025	17.025	17.020	17.020	17.010	17.010
Calcium, %	0.545	0.545	0.569	0.569	0.590	0.590
Phosphorus, %	0.411	0.411	0.416	0.416	0.429	0.429
NEm, Mcal/kg1	2.082	2.082	1.863	1.863	1.975	1.975
NEg, Mcal/kg2	1.432	1.432	1.281	1.281	1.337	1.337
1Net energy available for maintenance. 2Net energy available for gain.

Initial and final weights were determined using the average of weights taken on two consecutive days, and 14-day intermediate weights were taken prior to feeding at 0800 hours. Average daily gain, DMI, feed efficiency (gain/feed), and days required to reach slaughter weight were determined for all lambs. Lambs were removed from the trial on an individual basis as they reached the predetermined terminal weight range.

Three Polypay and three Targhee ram lambs were slaughtered at the initiation of the trial to estimate initial visceral organ weight. The remaining 120 lambs were allotted randomly by weight (within sex and breed) to the six treatments. There were five lambs per replicate and four replicate pens per treatment. As each pen

of lambs reached an average weight of 79 pounds, that pen was switched to the Period 2 diet (Table 2). All of the ram lambs were slaughtered when they reached the predetermined terminal weight range to determine final visceral organ weight, accretion rates, and final carcass measurements. Lambs were selected for slaughter in such a manner as to achieve equal carcass weights across treatments. Lambs were slaughtered at the local commercial abattoir, Tucker Packing Company, Orrville, OH. The visceral organs were removed from each lamb, flushed with water, allowed to drip dry, and weighed. Organs weighed were the heart, kidney, liver, rumen-reticulum, omasum, abomasum, small intestine, cecum, and colon. Chilled carcass weights were determined 48 hours after slaughter, and backfat, internal fat, and loin eye area were measured.

Table 2. Composition of diets fed to lambs weighing 79 to 115 pounds.
Item	Whole corn/ no fiber	Pelleted corn/ no fiber	Whole corn/ peanut hulls	Pelleted corn/ peanut hulls	Whole corn/ soybean hulls	Pelleted corn/ soybean hulls
	(%, Dry matter basis)
Whole corn	70.000	. . .	60.000	. . .	70.000	. . .
Ground corn	19.041	89.041	18.611	78.611	9.371	79.371
Peanut hulls	. . .	. . .	10.000	10.000	. . .	. . .
Soybean hulls	. . .	. . .	. . .	. . .	10.000	10.000
Soybean meal	4.000	4.000	4.140	4.140	3.760	3.760
Blood meal	2.000	2.000	2.070	2.070	1.880	1.880
Corn gluten meal	2.000	2.000	2.070	2.070	1.880	1.880
Urea	0.400	0.400	0.400	0.400	0.400	0.400
Limestone	1.300	1.300	1.300	1.300	1.300	1.300
Dicalcium phosphate	0.250	0.250	0.250	0.250	0.250	0.250
Monosodium phosphate	. . .	. . .	0.150	0.150	0.150	0.150
Trace mineral salt	0.450	0.450	0.450	0.450	0.450	0.450
Vitamin A, 30,000 IU/g	0.010	0.010	0.010	0.010	0.010	0.010
Vitamin D, 3,000 IU/g	0.010	0.010	0.010	0.010	0.010	0.010
Vitamin E, 44 IU/g	0.030	0.030	0.030	0.030	0.030	0.030
Selenium, 201 ppm	0.090	0.090	0.090	0.090	0.090	0.090
Ammonium chloride	0.400	0.400	0.400	0.400	0.400	0.400
Lasalocid, 67.5 g/pound	0.019	0.019	0.019	0.019	0.019	0.019
Calculated composition
Crude protein, %	15.155	15.155	15.150	15.150	15.162	15.162
Calcium, %	0.536	0.536	0.561	0.561	0.582	0.582
Phosphorus, %	0.404	0.404	0.410	0.410	0.422	0.422
NEm, Mcal/kg1	2.083	2.083	1.865	1.865	1.976	1.976
NEg, Mcal/kg2	1.433	1.433	1.283	1.283	1.338	1.338
1Net energy available for maintenance. 2Net energy available for gain.

Statistical analysis was performed using the GLM procedure of SAS (1988) for a 2 x 3 factorial experiment blocked by breed and sex. Performance data within each period and for the total trial were analyzed using a model that included effects due to breed, sex, corn processing, dietary fiber source, and the corn processing x dietary fiber source interaction. Twenty-four pens were used as the experimental units to house and feed the lambs. For visceral organ and carcass data, the model contained effects due to breed, corn processing, dietary fiber source, and the corn processing x dietary fiber source interaction. Individual lambs served as the experimental units. Treatment means were compared using the PDIFF statement of SAS (1988) when protected by a significant (P < 0.07) F-value.

Research protocols concerning animal care followed guidelines recommended in the Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching (Consortium, 1988).

Results and Discussion

Dry matter intake was greater for diets containing supplemental fiber (SBH or PH) compared with no supplemental fiber during both Period 1 (P < 0.01) and Period 2 (P < 0.001) (Table 3). Overall, DMI was greater (P < 0.05) for fiber supplemented diets compared with no fiber (Table 3). There was a greater ADG during both Periods 1 and 2 (P < 0.05) when peanut hulls were fed compared with no supplemental fiber (Table 3). Overall, both SBH and PH resulted in a greater (P < 0.05) ADG compared with diets containing no supplemental fiber. Lambs fed the control diet also required more days on feed (P < 0.05) to reach their terminal weight compared with lambs fed the SBH and PH diets (Table 3). Additionally, WSC resulted in a greater (P < 0.05) ADG compared with ground corn (Table 3).

Ground corn resulted in a greater (P < 0.05) fat depth compared with WSC (Table 4). Quality grade; leg conformation; percent kidney, pelvic, and heart fat (KPH); and dressing percentage were not different (P > 0.10) due to diet. Whole corn diets had a lower (P < 0.05) yield grade compared with ground corn diets.

The rumen-reticulum was heavier (P < 0.01) for lambs fed the ground corn diets compared with WSC diets (Table 5). Likewise, the daily accretion rate of the rumen-reticulum was greater (P < 0.05) with ground corn compared with whole corn (data not shown). Fiber source did not have an effect (P > 0.10) on viscera weights or daily accretion rates.

Whole shelled corn has an economic advantage over ground corn, because it does not have to undergo any mechanical breakdown, which would add cost to the diet. In the present study, ground corn resulted in a greater fat depth and higher yield grade than WSC. Therefore, if the objective of feeding high concentrate diets is to allow for rapid lean tissue gain, the cost and management required to process corn are not justified if the only outcome is a carcass containing a greater proportion of fat. The lower yield grade with whole corn is a direct measurement of increased overall carcass leanness compared with lambs fed ground corn.

Table 3. Main effects of corn type and fiber source on lamb performance.
	Corn type				Fiber type
Item	Ground	Whole	SEM	Control	SBH1	PH2	SEM3
	(Period 1)
DMI4, pound/day	2.13	2.15	6	2.08a	2.16b	2.17b	8
ADG5, pound/day	0.65	0.66	6	0.63c	0.65cd	0.68d	7
Gain/feed6, pound/pound	0.31	0.31	0.01	0.30	0.30	0.31	0.01
Days on feed	42.6	40.8	1.1	43.7	42.0	39.4	1.4
	(Period 2)
DMI, pounds/day	2.94	3.00	17	2.78e	3.08f	3.06f	20
ADG, pound/day	0.74	0.79	8	0.72c	0.78cd	0.79d	9
Gain/feed, pound/pound	0.25	0.25	0.01	0.25	0.25	0.26	0.01
Days on feed	34.8	34.2	1.5	35.3	33.8	34.4	1.9
	(Overall)
Initial weight, pounds	53.4	53.4	0.1	53.1	53.6	53.4	0.1
DMI, pounds/day	2.50	2.54	7	2.40c	2.58d	2.59d	9
ADG, pounds/day	0.69c	0.72d	4	0.67c	0.71d	0.73d	5
Gain/Feed, pound/pound	0.27	0.28	0.004	0.27	0.27	0.28	0.005
Days on feed	77.4	75.1	1.2	79.0c	75.8d	73.8d	1.4
Final weight, pounds	104.4	107.6	0.1	106.9	107.6	107.8	0.2
1 SBH = Soybean hulls. 2 PH = Peanut hulls. 3 SEM = Standard error of mean. 4 DMI = Dry matter intake. 5 ADG = Average daily gain. 6 Gain/feed = Feed efficiency a,b Means within a row with different superscripts differ (P < 0.01). c,d Means within a row with different superscripts differ (P < 0.05). e,f Means within a row with different superscripts differ (P < 0.001).

Table 4. Main effects of corn type and fiber source on slaughter lamb performance and carcass data.
	Corn type				Fiber type
Item	Ground	Whole	SEM	Control	SBH1	PH2	SEM3
Initial weight, pounds	54.27	54.50	0.13	54.87	53.85	54.44	1.6
Intermediate weight, pounds	82.01	81.80	1.8	83.78	80.65	81.28	2.2
End weight, pounds	113.74	114.50	0.60	113.38	114.28	114.03	0.75
Period 1, days	38.33	38.36	0.55	39.98	38.50	36.56	0.69
Period 2, days	38.91	37.26	2.30	37.49	39.65	37.11	2.88
On test, days	77.24	75.62	2.22	77.47	78.15	73.67	2.78
Period 1 ADG4, pounds/day	0.72	0.71	0.02	0.73	0.69	0.73	0.03
Period 2 ADG, pound/day	0.84	0.89	0.02	0.81	0.88	0.90	0.03
Overall ADG, pound/day	0.78	0.80	0.02	0.77	0.78	0.82	0.02
Hot carcass weight, pounds	57.25	57.98	0.60	57.71	57.90	57.22	0.76
Chilled carcass weight, pounds	55.61	56.18	0.53	56.14	56.19	55.36	0.31
Fat depth5, inch	0.28	0.23	0.02	0.25	0.28	0.24	0.03
%KPH6	3.76	3.60	0.08	3.63	3.78	3.64	0.10
Leg conformation7	11.26	10.84	0.22	10.89	11.10	11.17	0.27
Quality grade8	11.04	11.30	0.17	11.01	11.45	11.00	0.21
Dressing %	50.90	50.28	0.43	50.93	50.63	50.22	0.54
Yield grade5,8	3.93	3.52	0.14	3.65	3.89	3.62	0.18
REA9, inch2	2.20	2.36	0.06	2.25	2.27	2.32	0.08
1 SBH = Soybean hulls. 2 PH = Peanut hulls. 3 SEM = Standard error of mean. 4 ADG = Average daily gain. 5 Corn type effect (P < 0.05). 6 Kidney, pelvic, and heart fat. 7 9 = Good+, 10 = Choice-, 11= Choice, 12 = Choice+ 8 YG = 1.66 - (0.05 leg conformation grade code) + (0.25 percent kidney and pelvic fat) + (6.66 adjusted fat thickness, inches). 9 Ribeye area.

Table 5. Main effects of corn type and fiber source on organ and viscera weights.
	Corn type				Fiber type
Item	Ground	Whole	SEM	Control	SBH1	PH2	SEM3
Heart, g	197.19	207.03	4.75	200.86	203.76	201.71	5.95
Liver, g	1096.26	1143.33	20.71	1085.65	1141.12	1132.61	25.96
Kidney, g	145.03	146.09	3.27	139.11	149.38	148.19	4.10
Rumen-reticulum4, g	1312.52	1201.91	27.70	1259.00	1242.27	1270.37	34.73
Omasum, g	96.62	96.08	2.98	98.54	97.31	93.19	3.73
Abomasum, g	194.18	214.00	7.88	203.50	206.80	201.97	9.88
Small intestine, g	928.25	924.30	20.78	889.42	955.98	933.42	25.39
Cecum, g	66.48	63.25	2.09	62.51	65.53	66.57	2.62
Large intestine, g	472.04	443.47	14.94	445.41	464.94	462.93	18.73
Visceral fat, g	1407.99	1444.88	54.43	1454.27	1433.79	1391.23	68.24
1 SBH = Soybean hulls. 2 PH = Peanut hulls. 3 SEM = Standard error of mean. 4 Corn type effect (P < 0.01).

References

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Murphy, T.A., F.L. Fluharty, and S.C. Loerch. 1994. The influence of intake level and corn processing on digestibility and ruminal metabolism in steers fed all-concentrate diets. J. Anim. Sci. 72:1608.

Nocek, J.E., and S. Tamminga. 1991. Site of digestion of starch in the gastrointestinal tract of dairy cows and its effect on milk yield and composition. J. Dairy Sci. 74:3598.

NRC. 1985. Nutrient Requirements of Sheep (6th Ed.). National Academy Press, Washington, DC.

SAS. 1988. SAS/STAT User's Guide (Release 6.03). SAS Inst. Inc., Cary, NC.