F. L. Fluharty1, G. D. Lowe, and D. D. Clevenger
The Ohio State University Department of Animal Sciences
Eighty Columbia x Suffolk ewe lambs (initial body weight [BW] 114.5 6 0.8 lb) were used in a randomized complete block experiment to determine the effects of alfalfa haylage vs. corn silage on animal performance and carcass characteristics. Lambs offered alfalfa haylage consumed 23.5% more (P < 0.01) feed on a daily basis than lambs offered corn silage (4.09 vs. 3.31 lb/day, respectively). However, lambs fed corn silage gained 21.3% faster (P < 0.01) than lambs fed alfalfa haylage (0.57 vs. 0.47 lb/day, respectively). Additionally, lambs fed corn silage were 50.4% more efficient in converting feed to gain compared with lambs offered alfalfa haylage (0.173 vs. 0.115 lb gain/lb feed, respectively). Lambs fed corn silage had a heavier (P < 0.01) hot carcass weight and a greater (P < 0.01) dressing percentage compared with lambs offered alfalfa haylage (74.8 lb and 52% vs. 71.5 lb and 49.7%, respectively). Properly managed, alfalfa haylage and corn silage allowed ewe lambs to grow slowly and yield large carcasses with 0.22 to 0.26 inches of backfat.
Lamb feedlot diets are usually offered ad libitum. In the Midwest, corn is the least expensive energy source, and animals offered a high-concentrate diet ad libitum generally have a greater average daily gain (ADG) than animals grazed on legumes (Bidner et al., 1981; Tatum et al., 1988; McClure et al., 1994; Murphy et al., 1994). However, lambs that graze alfalfa accumulate less fat on a daily basis than lambs that are fed corn-based diets (Murphy et al., 1994; McClure et al., 1995; Fluharty et al., 1999). In many beef feedlots, ensiled feeds are used in place of grazing to allow for a growing phase prior to placing cattle on high-concentrate finishing diets. The use of ensiled feeds is not as common in lamb feeding operations as in beef feedlots, because of the required ensilage handling equipment, as well as the susceptibility of lambs to listeriosis with improperly made or managed silage. However, ensiled feeds may allow for growth of feedlot lambs without the management concerns of high-concentrate diets. The objectives of this experiment were to compare alfalfa haylage to corn silage in lamb feedlot diets on lamb growth and carcass characteristics.
Eighty Columbia x Suffolk ewe lambs (initial BW 114.5 6 0.8 lb) were used in a randomized complete block experiment to determine the effects of alfalfa haylage vs. corn silage on animal performance and carcass characteristics. The experiment began in November of 1998 and ended in February of 1999. The lambs originated from a ranch in Montrose, Colorado, and were transported by truck approximately 1,582 miles to the Ohio Agricultural Research and Development Center (OARDC) sheep feedlot in Wooster, Ohio. Diets were formulated to meet the dietary nutrient requirements of lambs (NRC, 1985) and to provide equal concentrations of crude protein (CP), vitamins, ammonium chloride, and lasalocid across treatments (Table 1). The concentration of phosphorus (P) was held constant at 0.4% across diets. However, because of the high concentration of calcium (Ca) in alfalfa (1.52% on a DM basis) and the potential negative impact on diet palatability of increasing the level of supplemental Ca in diets containing corn silage, the concentration of Ca differed between diets. Feed samples (100 g) were collected every 14 days throughout the experiment, dried in a forced-air oven at 551°C, ground to pass a 1-mm screen, and analyzed for dry matter (DM) (AOAC, 1984).
Table 1. Diet Composition. |
||
|---|---|---|
| Corn Silage | Alfalfa Haylage | |
| %, Dry Matter Basis | ||
|
Corn silage |
70.00 | – |
|
Alfalfa haylage |
– | 70.00 |
|
Ground corn |
11.47 | 20.27 |
|
Soybean meal |
16.80 | 7.60 |
|
Urea |
0.30 | 0.30 |
|
Dicalcium phosphate |
0.20 | – |
|
Monosodium phosphate |
– | 0.60 |
|
Trace mineral salta |
0.45 | 0.45 |
|
Vitamin A, 30,000 IU/g |
0.01 | 0.01 |
|
Vitamin D, 3,000 IU/g |
0.01 | 0.01 |
|
Vitamin E, 44 IU/g |
0.05 | 0.05 |
|
Selenium, 201 ppm |
0.09 | 0.09 |
|
Dynamateb |
0.20 | 0.20 |
|
Ammonium chloride |
0.40 | 0.40 |
|
Lasalocid, 150 g/kg |
0.022 | 0.022 |
|
Calculated composition: |
||
|
Crude protein, % |
18.01 | 18.01 |
|
Calcium, % |
0.67 | 1.09 |
|
Phosphorus, % |
0.44 | 0.43 |
|
NEm, Mcal/kg |
1.75 | 1.47 |
|
NEg, Mcal/kg |
1.14 | 0.89 |
| aContained
> 93% NaCl, 0.35% Zn, 0.28% Mn, 0.175% Fe, 0.035% Cu, 0.007% I, and 0.007%
Co. bMagnesium sulfate and potassium sulfate contained 22% S, 18% K, and 11% Mg (International Minerals and Chemical Co., Terre Haute, Ind.). |
||
Upon arrival at the feedlot, the lambs were provided long-stem alfalfa hay and had access to water troughs containing an electrolyte solution. Following an 18-hour rest period, the lambs were individually weighed, ear tagged, and vaccinated against Clostridium perfringens Types C and D, and Tetanus, with a second vaccine against Clostridium perfringens Types C and D and Tetanus given 14 days later. On 11—3—98, the 80 ewe lambs were weighed and allotted to two groups of 40 lambs, and fed either the corn-silage or alfalfa-haylage-based diet. During this pre-treatment period, the lambs fed alfalfa haylage gained 0.036 lb/hd/day, and the corn silage fed lambs gained 0.31 lb/hd/day. On 12—15—98 the lambs were weighed and allotted to eight pens of 10 lambs per pen. This weight on 12—15—98 was used as day one of the experiment. Initial and final weights of the lambs 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. The ADG, dry-matter intake (DMI), feed efficiency (gain/feed), and days required to reach slaughter weight were determined for all lambs. Lambs were removed from the trial, on a pen basis, as each pen reached the predetermined terminal weight range of 140 to 145 lb.
There were two blocks of lambs, based on body weight. There were 10 lambs per replicate pen and four replicate pens per each of the two treatments. Therefore, there were two light-weight and two heavy-weight pens per dietary treatment. The pens were 9.8 x 16.0 ft, with 9.8 ft of bunk space or 11.7 inches per lamb. All pens were constructed using expanded metal floors, with metal gates on three sides and a wooden fence-line feed bunk on the fourth side. Each pen had an automatic water cup so that water was available at all times.
Feed offered and feed refused were weighed daily in each pen prior to feeding at 0830 hours. Because sorting was predicted and to prevent feed spoilage, feed refusals were not allowed to remain in the feed bunk for more than one day before they were discarded. This was done because nutrient content of the diet available to the lambs could differ substantially among the diet groups if sorting occurred. Pens of lambs never had their intake increased or decreased by more than 10% of the previous day’s intake.
Lambs were slaughtered when their pen reached the predetermined terminal weight range. Lambs were slaughtered at a commercial abattoir. Two pens of lambs (20 lambs) per treatment were slaughtered for carcass data. Chilled carcass weights were determined 48 hours after slaughter, backfat and loin-eye area were measured, and internal fat was estimated.
Statistical analysis was performed using the GLM procedure of SAS (1988) for a randomized complete block experiment that was blocked by animal weight. Pen was used as the experimental unit for lamb performance data. Individual lambs served as the experimental unit for carcass data. Data were analyzed using a model that included effects due to diet, block, and the diet x block interaction. Treatment means were compared with Fisher’s LSD using the PDIFF statement of SAS (1988) when protected by a significant (P < 0.05) F-value. The residual mean square was used as the error term.
The effects of alfalfa haylage vs. corn silage on lamb performance are shown in Table 2. Lambs offered alfalfa haylage consumed 23.5% more (P < 0.01) feed on a daily basis than lambs offered corn silage (4.09 vs. 3.31 lb/day, respectively). However, lambs fed corn silage gained 21.3% faster (P < 0.01) than lambs fed alfalfa haylage (0.57 vs. 0.47 lb/day, respectively). Additionally, lambs fed corn silage were 50.4% more efficient in converting feed to gain compared with lambs offered alfalfa haylage (0.173 vs. 0.115 lb gain/lb feed, respectively). This percentage difference in efficiency of gain with corn silage vs. alfalfa haylage is very close to the 51.5% difference in net energy available for gain (NEg concentrations) reported for well-eared corn silage (1.03 Mcal/kg) and alfalfa silage between 30 to 50% dry matter (0.68 Mcal/kg) (NRC, 1985). As a result of the difference in efficiency of gain, lambs fed corn silage required 171 lb of feed to reach their market weight vs. 226 lb of feed for the lambs fed alfalfa haylage (P < 0.01).
Table 2. Effects of Alfalfa Haylage vs. Corn Silage on Lamb Performance. |
|||
|---|---|---|---|
|
Item |
Alfalfa Haylage | Corn Silage | SEM |
|
No. of lambs |
40 | 40 | |
|
Initial wt, lb |
115.5 | 113.5 | 0.9 |
|
Final wt, lb |
141.5 | 143.1 | 0.7 |
|
DMI, lba |
4.09 | 3.31 | 0.02 |
|
Days on test |
55.5 | 52.0 | 1.4 |
|
ADG, lba |
0.47 | 0.57 | 0.01 |
|
G/F, lb/lba |
0.115 | 0.173 | 0.004 |
|
Total DMI, lba |
226.0 | 171.0 | 3.2 |
| 1DMI = Dry-matter intake, ADG =
average daily gain, G/F = gain/feed, and SEM = standard error of mean. aDiet effect (P < 0.01). |
|||
The effects of diet on carcass characteristics are shown in Table 3. Lambs fed corn silage had a heavier (P < 0.01) hot carcass weight and a greater (P < 0.01) dressing percent compared with lambs offered alfalfa haylage (74.8 lb and 52% vs. 71.5 lb and 49.7%, respectively). Fluharty and McClure (1997) reported that lambs fed high-concentrate diets at restricted intakes had less visceral organ mass than lambs fed the same high-concentrate diets offered ad libitum, but that dressing percentage was not different due to increased visceral fat in the lambs offered feed ad libitum. In the present study, lambs fed corn silage had a greater (P < 0.05) backfat and higher (P < 0.05) yield grade compared with lambs fed alfalfa haylage (0.26 in and 3.7 vs. 0.22 in and 3.4, respectively) even though the lambs offered alfalfa haylage consumed 23.6% more feed on a daily basis. However, based on the efficiency of gain in the present study, the alfalfa haylage was probably not as digestible as the corn silage. This difference in digestibility, coupled with the greater energy density of corn silage compared with alfalfa haylage, resulted in more total energy available for gain with the lambs fed corn silage.
Table 3. Effects of Alfalfa Haylage vs. Corn Silage on Lamb Carcass Characteristics. |
|||
|---|---|---|---|
|
Item |
Alfalfa Haylage | Corn Silage | SEM |
|
No. of lambs |
20 | 20 | |
|
Final wt, lb |
143.9 | 143.8 | 1.0 |
|
Hot carcass wt, lba |
71.5 | 74.8 | 0.7 |
|
Dressing, %a |
49.7 | 52.0 | 0.5 |
|
Fat depth, inb |
0.22 | 0.26 | 0.01 |
|
Leg conformationc |
10.8 | 11.1 | 0.2 |
|
Quality gradec |
11.2 | 11.1 | 0.1 |
|
KPH fat, % |
3.3 | 3.5 | 0.1 |
|
Yield gradeb,d |
3.4 | 3.7 | 0.1 |
|
LEA, in2 |
2.79 | 2.79 | 0.09 |
| aDiet effect (P < 0.01)). bDiet effect (P < 0.05). c10 = Choice-, 11 = Choiceº, and 12 = Choice+. d1.66 - (0.05 x leg conformation score) + (0.25 x % KPH) + (6.66 x adjustment fat depth, inches). |
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Implications
Corn silage and alfalfa haylage resulted in growth rates between 0.45 and 0.60 lb/day. However, even at relatively slow growth rates with forage-based diets, differences in dietary energy density and digestibility (as measured by efficiency of gain) resulted in differences in carcass fat with no change in measured carcass lean. Properly managed, alfalfa haylage and corn silage allowed ewe lambs to grow slowly and yield large carcasses with 0.22 to 0.26 inches of backfat.
AOAC. 1984. Official Methods of Analysis. 14th Ed. Association of Official Analytical Chemists, Washington, D.C.
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Fluharty, F. L. and McClure, K. E. 1997. Effects of dietary energy intake and protein concentration on performance and visceral organ mass in lambs. J. Anim. Sci. 75:604—610.
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SAS/STAT. 1988. SAS/STAT User’s Guide: Statistics. SAS Institute, Inc., Cary, N.C.
Tatum, J. D., Klein, B. J., Williams Jr., F. L., and Bowling, R. A. 1988. Influence of diet on growth rate and carcass composition of steers differing in frame size and muscle thickness. J. Anim. Sci. 66:1942—1954.