F. L. Fluharty1, G. D. Lowe, and D. D. Clevenger
The Ohio State University Department of Animal Sciences
Ninety-six (48 ewes and 48 rams) early weaned Targhee x Hampshire lambs (initial weight 58.6 ± 0.6 lb) were used in a 2 x 3 factorial experiment to determine the effects of corn processing (whole shelled corn [WSC] vs. ground and pelleted corn [GC]) and feed-delivery system (feed constantly available, daily adjustment in intake, or weekly adjustment in intake) on animal performance and carcass characteristics. Lambs fed whole corn had a greater average daily gain (ADG) (P < 0.001), feed efficiency (P < 0.05), and required fewer (P < 0.001) days on feed compared with lambs fed ground/pelleted corn. Because of differences in days on feed, there were no differences (P > 0.10) in total pounds of feed required to reach market weight between lambs fed ground/pelleted corn and those fed whole-shelled corn. There were no consistent benefits to adjusting feed daily vs. offering feed ad libitum. Lambs consumed between 3.2 to 4.2% of body weight during the experiments. Therefore, comparisons of results between these lamb studies and cattle studies where the animals consume 2.0 to 2.5% of their body weight on a daily basis may lead to erroneous conclusions. Feeding ground/pelleted corn diets to lambs limits feed intake and minimizes differences in intake due to bunk management compared with whole-shelled corn diets.
Historically, feedlot animals have been allowed continuous access to feed. Recently, however, feeding systems that limit the amount of feed offered have gained popularity. However, reducing intake or using programmed intake systems have had variable results in controlled studies. Galyean (1992) delivered feed to steers in either a constant or programmed (6 10% daily or weekly) amount. Varying the amount of feed resulted in reduced ADG and efficiency of gain compared with constant feed delivery. Alternatively, Delehant et al. (1993) fed yearling steers twice daily to achieve daily intakes of 100%, 95%, or 90% of ad libitum intake. Steers fed to achieve 95% or 90% of ad libitum intake had lower ADG but improved efficiency of gain compared with cattle fed to 100% of ad libitum. Feed-delivery systems that result in restricting the intake of cattle have been shown to alter eating behavior by increasing the percentage of cattle that come to the feed bunk when feed is delivered and reducing the number of daily meals consumed compared with having feed available to cattle at all times (Knutsen et al., 1995). Recently, Bierman and Pritchard (1997) reported that a clean bunk management system reduced DMI and increased gain/feed without reducing ADG. These results can be partially explained by those of Knoblich et al. (1997), who reported that reducing the total energy intake of cattle seemed to be a prerequisite to altering feed efficiency of steers in limit-feeding systems.
Restricting the intake of 100% concentrate diets has been found to decrease visceral organ mass in lambs compared with offering feed ad libitum (Fluharty and McClure, 1997). This reduction in visceral organ mass may account for some of the increased efficiency of gain compared with offering feed ad libitum. Additionally, corn processing can influence diet digestibility in high-concentrate diets fed to lambs. Hejazi and Fluharty (1997) reported that whole corn resulted in improved DM, NDF, and N digestibility compared with rolled corn in high-concentrate diets. Therefore, feed-delivery management systems may have different effects depending on the level of grain processing. The objectives of these experiments were to determine the effects of feed-delivery system and corn processing on lamb growth and carcass characteristics.
Experiment 1
Ninety-six (48 ewes and 48 rams) early-weaned Targhee x Hampshire lambs (initial weight 58.6 ± 0.6 lb) were used in a 2 x 3 factorial experiment to determine the effects of corn processing WSC vs. GC and feed-delivery system (feed constantly available, daily adjustment in intake, or weekly adjustment in intake) on animal performance and carcass characteristics. The experiment began in April of 1997 and ended in July of 1997. Composition of the diets is shown in Table 1. 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 80 lb. Period 2 diets were fed starting when lambs reached 80 lb and continued to be fed until lambs reached terminal weight (100 to 110 lb for ewes, and 105 to 115 lb for rams). Diets were formulated to provide equal daily intakes of vitamins, minerals, urea, ammonium chloride, and lasalocid across treatments. Feed samples were collected weekly and composited within each of the two periods. Feed samples were dried in a forced-air oven at 551ºC, ground to pass a 1-mm screen, and analyzed for DM (AOAC, 1984).
Table 1. Diet Composition. |
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|---|---|---|---|---|
|
Item |
Whole Corn Period 1 |
Pelleted Corn Period 1 |
Whole Corn Period 2 |
Completely Pelleted Period 2 |
|
Whole corn |
70.00 | – | 70.00 | – |
|
Ground corn |
6.01 | 76.01 | 9.37 | 79.37 |
|
Soybean hulls |
10.00 | 10.00 | 10.00 | 10.00 |
|
Soybean meal |
5.44 | 5.44 | 3.76 | 3.76 |
|
Blood meal |
2.72 | 2.72 | 1.88 | 1.88 |
|
Corn gluten meal |
2.72 | 2.72 | 1.88 | 1.88 |
|
Urea |
0.40 | 0.40 | 0.40 | 0.40 |
|
Limestone |
1.30 | 1.30 | 1.30 | 1.30 |
|
Dicalcium phosphate |
0.25 | 0.25 | 0.25 | 0.25 |
|
Monosodium phosphate |
0.15 | 0.15 | 0.15 | 0.15 |
|
Trace mineral salta |
0.45 | 0.45 | 0.45 | 0.45 |
|
Vitamin A, 30,000 IU/g |
0.01 | 0.01 | 0.01 | 0.01 |
|
Vitamin D, 3,000 IU/g |
0.01 | 0.01 | 0.01 | 0.01 |
|
Vitamin E, 44 IU/g |
0.03 | 0.03 | 0.03 | 0.03 |
|
Selenium, 201 ppm |
0.09 | 0.09 | 0.09 | 0.09 |
|
Ammonium chloride |
0.40 | 0.40 | 0.40 | 0.40 |
|
Lasalocid, 150 g/kg |
0.019 | 0.019 | 0.019 | 0.019 |
|
Calculated composition: |
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|
Crude protein, % |
17.01 | 17.01 | 15.16 | 15.16 |
|
Calcium, % |
0.59 | 0.59 | 0.58 | 0.58 |
|
Phosphorus, % |
0.43 | 0.43 | 0.42 | 0.42 |
|
NEm, Mcal/kg |
1.98 | 1.98 | 1.98 | 1.98 |
|
NEg, Mcal/kg |
1.34 | 1.34 | 1.34 | 1.34 |
|
Analyzed composition: |
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|
Crude protein, % |
15.95 | 15.41 | ||
|
NDF, % |
24.14 | 21.04 | ||
|
Starch, % |
49.88 | 54.68 | ||
|
aContained > 93% NaCl, 0.35% Zn, 0.28% Mn, 0.175% Fe, 0.035% Cu, 0.007% I, and 0.007% Co. |
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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. 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 a pen basis, as each pen reached the predetermined terminal weight range (100 to 110 lb for ewes, and 105 to 115 lb for rams).
There were four lambs per replicate pen and four replicate pens per each of the six treatments. Therefore, each dietary and feed-delivery system combination had two pens of each sex. The pens (5 x 16 ft) were constructed using expanded metal floors, with metal gates on three sides and a wooden fence-line feed bunk (5-ft long) on the fourth side. Each pen had an automatic water cup so that water was available at all times.
Three feed-delivery systems were used in this experiment (feed constantly available, daily adjustment in intake, or weekly adjustment in intake). Feed offered and feed refused was weighed daily in each pen prior to refeeding at 0830 hours. For the ad libitum consumption pens, feed was offered so that it was constantly available. Because sorting was predicted, feed was not allowed to remain in the feed bunk for more than one day before it was discarded. This was done because nutrient content of the diet available to the lambs could differ substantially among the management groups if sorting occurred in the ad libitum group. The daily adjustment group never had their intake increased or decreased by more than 5% of the previous day’s intake. Additionally, lambs in the daily adjustment pens never had their feed offered increased two consecutive days. The management strategy for the daily adjustment group was intended to have a slicked bunk at least 50% of the time.
As each pen of lambs reached an average weight of 80 lb, that pen was switched to the Period 2 diet (Table 1). All 48 ram lambs were slaughtered at a commercial abattoir when their pen reached the predetermined terminal weight range to determine final carcass measurements. However, one lamb became lame during the trial, was not within the terminal weight range specified by the commercial abattoir, and was not available for carcass data. Chilled carcass weights were determined 48 hours after slaughter, and backfat, internal fat, and loin-eye area were measured.
Statistical analysis was performed using the GLM procedure of SAS (1988) for a 2 x 3 factorial experiment blocked by sex. Performance data within each period, and for the total trial, were analyzed using a model that included effects due to sex, corn processing, feed-delivery system, and the corn processing x feed-delivery system interaction. Pen was used as the experimental unit for lamb performance data. Treatment means were compared using the PDIFF statement of SAS (1988) when protected by a significant (P < 0.05) F-value.
Experiment 2
Ninety-two (36 ewes and 56 wethers) Targhee x Dorset lambs (initial weight 83 ± 1.0 lb) were used in a 2 x 2 factorial experiment to determine the effects of corn processing WSC vs. GC and feed-delivery system (feed constantly available vs. daily adjustment in intake) on animal performance and carcass characteristics. The experiment began on October 17, 1997, and ended in December of 1997. The diets used in this experiment were the same as in Experiment 1, Period 2 (Table 1). Diets were formulated to meet the dietary nutrient requirements (NRC, 1985). Diets were formulated to provide equal daily intakes of vitamins, minerals, urea, ammonium chloride, and lasalocid across treatments. Feed samples were collected weekly and composited within each of the two periods. Feed samples were dried in a forced-air oven at 551°C, ground to pass a 1-mm screen, and analyzed for DM (AOAC, 1984).
The lambs used in this experiment originated in Licking, Mo., and were transported a distance of 653 miles by truck to the Ohio Agricultural Research and Development Center’s sheep facility in Wooster, Ohio. Because of the distance traveled, a one-week receiving period was used to acclimate the lambs to the feedlot facility prior to initiation of the experiment. During this time, whole shelled corn, a pelleted protein/mineral supplement, and alfalfa haylage were used. Initial weights of lambs were determined the first two days that the lambs were in the feedlot. 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. 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 a pen basis, as each pen reached the predetermined terminal weight range (110 to 115 lb for ewes, and 115 to 120 lb for wethers).
There were four or five ewe lambs per replicate ewe pen and four or five wether lambs per replicate wether pen. There were five replicate pens per treatment (one ewe pen containing four lambs, one ewe pen containing five lambs, one wether pen containing four wethers, and two wether pens containing five lambs each). Two ewe lambs offered feed ad libitum were removed from the trial due to slow growth (less than 0.25 lb/day).
The pens (5 x 16 ft) were constructed using expanded metal floors, with metal gates on three sides and a wooden fence-line feed bunk (5-ft long) on the fourth side. Each pen had an automatic water cup so that water was available at all times.
Two feed-delivery systems were used in this experiment (feed constantly available vs daily adjustment in intake). Feed offered and feed refused was weighed daily in each pen prior to refeeding at 0830 hours. For the ad libitum consumption pens, feed was offered so that it was constantly available. Because sorting was predicted, feed was not allowed to remain in the feed bunk for more than one day before it was discarded. This was done because nutrient content of the diet available to the lambs could differ substantially among the management groups if sorting occurred in the ad libitum group. The daily adjustment group never had their intake increased or decreased by more than 5% of the previous day’s intake. Additionally, lambs in the daily adjustment pens never had their feed offered increased two consecutive days. The management strategy for the daily adjustment group was intended to have a slicked bunk at least 50% of the time.
All 56 wether lambs were slaughtered at a commercial abattoir when their pen reached the predetermined terminal weight range to determine final carcass measurements. However, four lambs fed whole corn, but on two different feed-delivery treatments, lost their identification tags in the cooler and were not used in the analysis for carcass characteristics. Chilled carcass weights were determined 48 hours after slaughter, and backfat, internal fat, and loin-eye area were measured.
Statistical analysis was performed using the GLM procedure of SAS (1988) for a 2 x 2 factorial experiment blocked by sex. Performance data for the total trial were analyzed using a model that included effects due to sex, corn processing, feed-delivery system, and the corn processing x feed-delivery system interaction. Pen was used as the experimental unit for lamb performance data. Treatment means were compared using the PDIFF statement of SAS (1988) when protected by a significant (P < 0.05) F-value.
Experiment 1
There was a corn processing x feed-delivery system interaction for dry-matter intake (DMI) (Table 2). Regardless of corn-processing method, lambs that had their feed intake adjusted weekly consumed less feed (P < 0.001) compared with lambs that had their feed intake adjusted daily or lambs offered feed ad libitum. However, when ground/pelleted corn was fed, there was no difference (P > 0.60) in DMI between daily adjusted (2.69 lb/day) and ad libitum fed (2.72 lb/day) lambs. When whole corn was fed, DMI was less (P < 0.05) with daily adjusted (3.12 lb/day) vs. ad libitum fed (3.33 lb/day) lambs. This interaction occurred partly because lambs fed ground/pelleted corn consumed less (P < 0.001) than lambs fed whole corn (2.58 vs 2.95 lb/day, respectively). Lambs fed ground/pelleted corn consumed less feed as a percent of body weight than lambs fed whole shelled corn throughout the trial (Figure 1). Therefore, when ground/pelleted corn was fed, low feed intake limited any further effect that feed-delivery system may have had on feed intake. Lambs fed whole corn had a greater ADG (P < 0.001), feed efficiency (P < 0.05), and required fewer (P < 0.001) days on feed compared with lambs fed ground/pelleted corn (Table 2).
Table 2. Effects of Corn Processing and Feed-Delivery System on Lamb Performance. |
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|---|---|---|---|---|---|---|---|
| Corn Processing | Feed-Delivery System | ||||||
| Item1 | Ground | Whole | SEM1 | Weekly | Daily | Ad Libitum | SEM1 |
|
No. of lambs |
48 | 48 | 32 | 32 | 32 | ||
|
Initial wt, lb |
58.7 | 58.7 | 0.09 | 58.4 | 58.7 | 58.4 | 0.11 |
|
Final wt, lb |
107.8 | 107.6 | 0.7 | 106.9 | 107.2 | 108.9 | 0.9 |
|
DMI, lba |
2.58b | 2.95c | 0.02 | 2.40 | 2.91 | 3.02 | 0.04 |
|
Days on test |
71.5b | 59.8c | 1.6 | 76.7b | 60.1c | 60.1c | 2.0 |
|
ADG, lb |
0.68b | 0.86c | 0.02 | 0.64b | 0.84c | 0.86c | 0.02 |
|
G/F, lb/lb |
0.267d | 0.285e | 0.005 | 0.265 | 0.284 | 0.280 | 0.006 |
|
Total DMI, lb |
183.7 | 172.4 | 4.0 | 183.0 | 172.0 | 179.0 | 4.9 |
| 1 DMI = Dry-matter intake, ADG =
average daily gain, G/F = gain/feed, and SEM = standard error of mean. a Corn processing x feed-delivery system interaction (P < 0.001). b,c Means within a row with different superscripts differ (P < 0.001). d,e,f Means within a row with different superscripts differ (P < 0.05). |
|||||||
|
| Figure 1. Effects of corn processing on dry-matter intake (DMI) as a percentage of body weight (BW). |
Lambs that had intake adjusted daily and lambs offered feed ad libitum had greater (P < 0.001) ADG and required fewer (P < 0.001) days on feed compared to lambs that had their feed intake adjusted weekly (Table 2). When intake was expressed as a percent of body weight to compare daily adjusted vs. ad libitum fed lambs, the only difference in intake occurred during the first 14 days (P < 0.05) (Figure 2). However, there were no differences (P > 0.10) in feed efficiency due to feed-delivery system. Likewise, there was no difference (P > 0.10) in total DMI due to either corn processing or feed-delivery system. Additionally, lambs that consumed less per day required more days on feed to reach their terminal weight, so total feed intake was not different (P > 0.10) (Table 2).
 |
| Figure 2. Effects of feed-delivery system on dry-matter intake (DMI) as a percentage of body weight (BW). |
Effects of corn processing and feed-delivery system on wether lamb performance and carcass characteristics are shown in Table 3. There were only slight differences in carcass composition due to corn processing or feed-delivery system. Quality grade was greater (P < 0.05) with lambs adjusted in feed intake weekly compared with those adjusted daily. Additionally, percent kidney, pelvic, and heart fat was greater (P < 0.05) in lambs fed ground/pelleted corn compared to whole-shelled corn. However, there were no differences (P > 0.10) in hot carcass weight, backfat depth, leg conformation score, L. dorsi area, or yield grade due to corn processing or feed-delivery system.
Table 3. Effects of Corn Processing and Feed-Delivery System on Wether Lamb Performance and Carcass Characteristics. |
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|---|---|---|---|---|---|
| Corn Processing | Feed-Delivery System | ||||
|
Item1 |
Ground | Whole | Weekly | Daily | Ad Libitum |
|
No. of lambs |
23 | 24 | 16 | 16 | 15 |
|
Initial wt, lb |
61.5 ± 0.7 | 61.1 ± 0.7 | 61.1 ± 0.7 | 61.3 ± 0.9 | 61.5 ± 0.9 |
|
Final wt, lb |
113.8 ± 1.5 | 112.7 ± 1.5 | 112.7 ± 1.8 | 113.6 ± 1.8 | 113.3 ± 1.8 |
|
Days on testa |
72.5 ± 1.2 | 57.5 ± 0.7 | 76.7 ± 1.4 | 61.0 ± 1.4 | 57.3 ± 1.4 |
|
ADG, lb |
0.75 ± 0.02b | 0.93 ± 0.02c | 0.66 ± 0.02b | 0.90 ± 0.02c | 0.93 ± 0.02c |
|
Hot carcass wt, lb |
59.8 ± 0.9 | 59.3 ± 0.9 | 59.8 ± 1.1 | 59.5 ± 1.1 | 59.3 ± 1.1 |
|
Chilled carcass wt, lb |
58.4 ± 0.9 | 57.8 ± 0.9 | 58.7 ± 1.1 | 57.6 ± 1.1 | 58.0 ± 1.1 |
|
Dressing, % |
52.6 ± 0.3 | 52.6 ± 0.3 | 53.0 ± 0.4 | 52.5 ± 0.4 | 52.3 ± 0.4 |
|
Backfat depth, in |
0.28 ± 0.02 | 0.27 ± 0.02 | 0.28 ± 0.02 | 0.24 ± 0.02 | 0.30 ± 0.02 |
|
Leg conformationd |
11.0 ± 0.2 | 10.8 ± 0.2 | 11.3 ± 0.2 | 10.7 ± 0.2 | 10.7 ± 0.3 |
|
Quality graded |
11.3 ± 0.2 | 11.0 ± 0.2 | 11.6 ± 0.2e | 10.8 ± 0.2f | 11.1 ± 0.2ef |
|
KPH fat, % |
3.8 ± 0.1e | 3.5 ± 0.1f | 3.7 ± 0.1 | 3.6 ± 0.1 | 3.6 ± 0.1 |
|
L. dorsi area, in2 |
2.36 ± 0.06 | 2.46 ± 0.06 | 2.53 ± 0.08 | 2.36 ± 0.5 | 2.37 ± 0.08 |
|
Yield gradeg |
3.9 ± 0.1 | 3.8 ± 0.1 | 3.9 ± 0.1 | 3.6 ± 0.1 | 4.0 ± 0.1 |
| 1 ADG = Average daily gain and KPH
fat = Kidney, pelvic, and heart fat. a Corn processing x feed-delivery system interaction (P < 0.05). b,c Means within a row with different superscripts differ (P < 0.001). d 10 = choice-, 11 = choiceº, 12 = choice+. e,f Means within a row with different superscripts differ (P < 0.05). g Yield grade = 1.66 - (0.05 x leg conformation code) + (0.25 x % KPH fat) + (6.66 x adjusted for fatthickness, inches). |
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Experiment 2
As in Experiment 1, there was a corn processing x feed-delivery system interaction on dry-matter intake (Table 4). When ground/pelleted corn was fed, there was no difference (P > 0.80) in DMI between daily adjusted (2.85 lb/day) and ad libitum fed (2.87 lb/day) lambs. When whole corn was fed, DMI was less (P < 0.05) with daily adjusted (3.07 lb/day) vs. ad libitum fed (3.40 lb/day) lambs. This interaction occurred partly because lambs fed ground/pelleted corn consumed less than lambs fed whole corn (2.87 vs. 3.24 lb/day, respectively), and is nearly identical to the results of Experiment 1.
Table 4. Effects of Corn Processing and Feed-Delivery System on Lamb Performance. |
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|---|---|---|---|---|---|
| Corn Processing | Feed-Delivery System | ||||
|
Item1 |
Ground | Whole | Daily | Ad Libitum | SEM1 |
|
No. of lambs |
45 | 45 | 46 | 44 | |
|
Initial wt, lb |
85.3 | 85.3 | 85.3 | 85.3 | 0.4 |
|
Final wt, lb |
122.8 | 124.6 | 123.5 | 123.9 | 1.3 |
|
DMI, lba |
2.87 | 3.24 | 2.95 | 3.13 | 0.04 |
|
Days on testb |
62.7 | 50.8 | 57.8 | 55.7 | 2.4 |
|
ADG, lbc |
0.59 | 0.76 | 0.67 | 0.69 | 0.02 |
|
G/Fd, lb/lb |
0.208 | 0.235 | 0.224 | 0.219 | 0.007 |
|
Total DMI, lb |
178.8 | 164.5 | 170.2 | 173.3 | 7.9 |
| 1 DMI = Dry-matter intake, ADG =
average daily gain, G/F = gain/feed, and SEM = standard error of mean. a Corn processing x feed-delivery system interaction (P < 0.05). b Corn processing effect (P < 0.01). c Corn processing effect (P < 0.001). d Corn processing effect (P<0.05). |
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Lambs fed whole corn had a greater ADG (P < 0.001) (0.76 vs 0.59 lb/day), feed efficiency (P < 0.05) (0.235 vs. 0.208 lb gain/lb feed), and required fewer (P < 0.01) days on feed (50.8 vs. 62.7) compared with lambs fed ground/pelleted corn. Once again, there were no differences (P > 0.10) in ADG, feed efficiency, or days on feed between lambs that had the amount of feed offered adjusted daily and those allowed ad libitum access to feed.
There was a corn processing x feed-delivery system interaction (P < 0.05) for dressing percentage (Table 5). When ground/pelleted corn was fed, there were no differences (P > 0.41) in dressing percentage between daily adjusted and ad libitum fed lambs (53.3 vs. 52.8%, respectively). However, when whole-shelled corn was fed, the daily adjusted lambs had a lower (P < 0.05) dressing percentage (51.4%) compared with the lambs offered feed ad libitum (52.9%). In contrast to Experiment 1, lambs fed ground/pelleted corn had a larger (P < 0.01) L. dorsi area compared with lambs fed whole-shelled corn. Lambs offered feed ad libitum did not (P > 0.10) have a greater backfat depth than lambs that received a daily adjustment in intake. However, ad libitum fed lambs had a greater leg conformation score (P < 0.01), higher quality grade (P < 0.05), and a higher percent kidney, pelvic, and heart fat (P < 0.05).
Table 5. Effects of Corn Processing and Feed-Delivery System on Wether Lamb Performance and Carcass Characteristics. |
||||
|---|---|---|---|---|
| Corn Processing | Feed-Delivery System | |||
|
Item1 |
Ground | Whole | Daily | Ad Libitum |
|
No. of lambs |
28 | 24 | 26 | 26 |
|
Initial wt, lb |
86.4 ± 0.9 | 86.7 ± 0.9 | 86.7 ± 0.9 | 86.2 ± 0.9 |
|
Final wt, lb |
127.2 ± 1.8 | 130.1 ± 2.0 | 128.8 ± 1.8 | 128.6 ± 1.8 |
|
Days on testa |
71.3 ± 1.0 | 55.7 ± 1.1 | 63.3 ±1.0 | 63.8 ± 1.0 |
|
ADG, lb |
0.58 ± 0.02 | 0.42 ± 0.02c | 0.68 ± .02 | 0.68 ± 0.01 |
|
Hot carcass wt, lb |
67.5 ± 1.1 | 67.8 ± 1.2 | 67.5 ± 1.1 | 67.9 ± 1.1 |
|
Chilled carcass wt, lb |
66.6 ± 1.1 | 66.8 ± 1.2 | 66.4 ± 1.1 | 66.8 ± 1.1 |
|
Dressing, %b |
53.0 ± 0.3 | 52.6 ± 0.3 | 52.4 ± 0.3 | 52.8 ± 0.3 |
|
Backfat depth, in |
0.23 ± 0.04 | 0.22 ± 0.02 | 0.21 ± 0.02 | 0.24 ± 0.02 |
|
Leg conformationc,d |
10.2 ± 0.1 | 10.8 ± 0.2 | 9.8 ± 0.1 | 10.4 ± 0.1 |
|
Quality gradec,e |
10.5 ± 0.1 | 11.0 ± 0.2 | 10.4 ± 0.1 | 10.7 ± 0.1 |
|
KPH fate, % |
3.9 ± 0.1e | 3.5 ± 0.1f | 3.7 ± 0.1 | 4.0 ± 0.1 |
|
L. dorsi area, in2f |
2.70 ± 0.06 | 2.38 ± 0.07 | 2.57 ± 0.08 | 2.53 ± 0.06 |
|
Yield gradeg |
3.7 ± 0.1 | 3.8 ± 0.1 | 3.5 ± 0.1 | 3.7 ± 0.1 |
| 1 ADG = Average daily gain and KPH
fat = kidney, pelvic, and heart fat. a Corn processing effect (P < 0.001). b Corn processing x feed-delivery system interaction (P < 0.05). c 9 = Good+, 10 = choice-, and 11 = choice. d Feed-delivery system effect (P < 0.01). e Feed-delivery system effect (P<0.05). f Corn processing effect (P<0.01). g Yield grade = 1.66 - (0.05 x leg conformation code) + (0.25 x % KPH fat) + (6.66 x adjusted for fat thickness, inches). |
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Implications
Lambs fed whole corn have a greater dry-matter intake and average daily gain, and require fewer days on feed compared with lambs fed ground/pelleted corn. Because of differences in days on feed, there were no differences in total pounds of feed required to reach market weight between lambs fed ground/pelleted corn and those fed whole shelled corn. There were no consistent benefits to adjusting feed daily vs. offering feed ad libitum. Lambs consumed between 3.2 to 4.2% of body weight during the experiments. Therefore, comparisons of results between these lamb studies and cattle studies where the animals consume 2.0 to 2.5% of their body weight on a daily basis may lead to erroneous conclusions. Differences in feeding behavior and amount of feed consumed as a percent of body weight between feedlot lambs and steers makes across species comparisons questionable. Feeding ground/pelleted corn diets to lambs limits feed intake and minimizes differences in intake due to bunk management compared with whole-shelled corn diets.
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