F. L. Fluharty1, G. D. Lowe, and D. D. Clevenger
The Ohio State University Department of Animal Sciences
Seventy-two early weaned Targhee x Hampshire ram lambs (initial weight 79.6 ± 1.2 lb) were used in a randomized complete block design experiment to determine the effects of floor type on animal performance and carcass characteristics. Pen type affected dry-matter intake (DMI) (P < 0.01). Lambs on expanded metal consumed the least (2.72 lb/day), lambs on straw consumed the most (2.82 lb/day), and lambs on sand were intermediate. The differences in DMI resulted in lambs on expanded metal gaining weight slower (P < 0.05) than lambs on straw (0.57 vs. 0.63 lb/day, respectively). There were no differences (P > 0.10) in feed efficiency, total days on feed, or total dry-matter intake due to flooring or bedding. With high-concentrate and limit-fed diets, sand flooring and straw-bedded dirt floors resulted in improved animal performance compared to expanded metal floors. Straw consumption resulted in greater gut content weight, but did not negatively affect average daily gain (ADG) or feed efficiency.
In the eastern United States, high annual rainfall causes most lambs to be fed in enclosed or covered open-sided feedlots. The type of floor in these pens can range from dirt or sand flooring to even concrete or expanded metal flooring. Flooring type may affect animal behavior if the flooring material causes stress to the animal, and bedding may alter feed intake. The use of straw bedding may potentially provide a source of feed that results in inefficient utilization of high-concentrate diets. Therefore, a balance must exist between animal comfort and well-being, cleanliness, and economic efficiency.
High-concentrate diets are used efficiently for gain but may result in lambs having excess fat compared with lambs offered moderate-energy diets. Feeding lambs at a level less than ad libitum is one feasible way to slow the rate of fat deposition through reductions in energy intake (Fluharty and McClure, 1997). 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). Additionally, Bierman and Pritchard (1997) reported that a clean bunk management system reduced DMI and increased gain/feed without reducing ADG in steers. Restricting the intake of 100% concentrate diets to 85% of ad libitum intake 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, feeding lambs high-concentrate diets at levels below ad libitum intake has been shown to achieve carcasses with greater weights with similar fat levels and increased lean mass compared with grazing lambs on alfalfa, without the management requirements of intensive grazing systems (Fluharty et al., 1999). The objective of this experiment was to determine the effects of floor type and bedding on lamb growth and carcass characteristics when lambs were limited in intake to 3.0 to 3.5% of their body weight throughout the feeding period.
Seventy-two early weaned Targhee x Hampshire ram lambs (initial weight 79.6 ± 1.2 lb) were used in a randomized complete block design experiment to determine the effects of floor type on animal performance and carcass characteristics. The three pen floor types tested were sand, dirt bedded with straw, and expanded metal. Initial weight of the lambs served as the block. There were three weight blocks (light weight, 59 to 64 lb; middle weight, 65 to 73 lb; and heavy weight, 74 to 84 lb). The experiment began in April of 1998 and ended in July 1998. Composition of the diet is shown in Table 1. Diets were formulated to meet the dietary nutrient requirements of lambs according to NRC (1985). Feed samples were collected weekly and analyzed for DM (AOAC, 1984).
Table 1. Diet Composition. |
|
|---|---|
| Item | %, Dry Matter Basis |
|
Whole corn |
55.00 |
|
Ground corn |
11.47 |
|
Alfalfa pellets |
10.00 |
|
Soybean hulls |
10.00 |
|
Soybean meal |
11.00 |
|
Urea |
0.40 |
|
Limestone |
0.60 |
|
Dicalcium phosphate |
0.50 |
|
Trace mineral salta |
0.45 |
|
Vitamin A, 30,000 IU/g |
0.01 |
|
Vitamin D, 3,000 IU/g |
0.01 |
|
Vitamin E, 44 IU/g |
0.05 |
|
Selenium, 201 ppm |
0.09 |
|
Ammonium chloride |
0.40 |
|
Lasalocid, 150 g/kg |
0.022 |
|
Calculated composition: |
|
|
Crude protein, % |
15.31 |
|
Calcium, % |
0.52 |
|
Phosphorus, % |
0.43 |
|
NEm, Mcal/kg |
1.91 |
|
NEg, Mcal/kg |
1.28 |
|
aContained > 93% NaCl, 0.35% Zn, 0.28% Mn, 0.175% Fe, 0.035% Cu, 0.007% I, and 0.007% Co. |
|
Initial and final weights of the lambs were determined using the average of weights taken on two consecutive days, and seven-day intermediate weights were taken prior to feeding at 0800 hours. The seven-day intermediate weights were used to calculate the next week’s feed intake (3.25% of live weight). 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 of 120 to 130 lb.
There were four lambs per replicate pen and six replicate pens per each of the three treatments. The expanded metal 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. The pens containing sand or dirt with straw bedding were 8.5 x 15.4 ft, and also had a fence-line feed bunk (5 ft), and had an automatic water supply available at all times.
The lambs were offered feed at 3.0 to 3.5% of body weight throughout the trial. The following schedule was used: week 1, 3.0%; weeks 2 to 3, 3.5%; weeks 4 to 5, 3.25%; weeks 6 to 8, 3.0%; and weeks 9 to 14, 3.25%. This schedule was expected to result in a gain of approximately 270 g/day (0.6 lb) based on the energy content of the diet.
Two lambs were removed from the trial and from the statistical analysis. One lamb on the straw treatment was removed due to a rectal prolapse, and one lamb on the metal flooring was removed due to excessive wool picking. Lambs were slaughtered when their pen reached the predetermined terminal weight range to determine final carcass measurements. Lambs were slaughtered at a commercial abattoir. Chilled carcass weights were determined 48 hours after slaughter, and backfat, internal fat, and loin-eye area (LEA) were measured.
Statistical analysis was performed using the GLM procedure of SAS (1988) for a randomized complete block design experiment, blocked by initial weight of the lambs. Performance and carcass data were analyzed using a model that included effects due to treatment, block, and the treatment x block interaction. There were no significant interactions, so the treatment x block interaction was dropped from the model. Pen was used as the experimental unit for lamb performance, and animal was used as the experimental unit for carcass data. Visceral organ data were analyzed using animal as the experimental unit. Only lambs from the large block were used for visceral organ data. Therefore, the model only included effects due to treatment. Treatment means were compared with Fisher’s protected LSD using the PDIFF statement of SAS (1988) when protected by a significant (P < 0.05) 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).
The diet was an 80% concentrate, 20% forage diet, with whole-shelled corn fed at 55% of the diet, and the remaining ingredients fed in a pelleted supplement. Alfalfa pellets and soybean hulls each were fed at 10% of the diet (Table 1).
Pen type affected DMI (P < 0.01). Lambs on expanded metal consumed the least (2.72 lb/day), lambs on straw consumed the most (2.82 lb/day), and lambs on sand were intermediate (Table 2). The differences in DMI resulted in lambs on expanded metal gaining weight slower (P < 0.05) than lambs on straw (0.57 vs. 0.63 lb/day, respectively). There were no differences (P > 0.10) in feed efficiency, total days on feed, or total DMI due to flooring or bedding.
Table 2. Effects of Pen Characteristics on Lamb Performance. |
||||
|---|---|---|---|---|
|
Item |
Expanded Metal | Sand | Straw | SEMa |
|
No. of lambs |
23 | 24 | 23 | |
|
Initial wt, lb |
77.6 | 77.6 | 77.8 | 0.2 |
|
DMIa, lb/day |
2.72b | 2.76c | 2.82d | 0.01 |
|
Gain, lb/day |
0.57e | 0.60ef | 0.63f | 0.01 |
|
Gain/feed, lb/lb |
0.211 | 0.219 | 0.224 | 0.005 |
|
Days on feed |
85.5 | 84.3 | 83.2 | 2.0 |
|
Total DMI, lb |
230.9 | 230.9 | 233.3 | 6.6 |
|
Final wt, lb |
126.3 | 128.3 | 130.1 | 1.1 |
| a Dry-matter intake and SEM = standard
error of mean. b,c,d Means within a row with different superscripts differ (P < 0.01). e,f Means within a row with different superscripts differ (P < 0.05). |
||||
There were no differences (P > 0.10) in visceral organ weight due to floor type or bedding (Table 3). However, lambs bedded with straw had the numerically heaviest rumen/reticulum, omasum, abomasum, small intestine, and large intestine weights, which could be explained by their having the greatest (P < 0.05) amount of gut contents. An attempt was made to measure the amount of straw consumed. However, the nipple waterers in the pens bedded with straw had excessive dripping, which made the straw in the vicinity of the waterers very wet. Therefore, we were unable to correct for moisture content of the straw accurately enough to measure the amount of straw consumed.
Table 3. Effects of Pen Characteristics on Lamb Visceral Organ Mass. |
||||
|---|---|---|---|---|
|
Item |
Expanded Metal | Sand | Straw | SEM |
|
No. of lambs |
8 | 8 | 8 | |
|
Final wt, lb |
127.4 | 130.1 | 130.3 | 2.0 |
|
Liver wt, lb |
2.60 | 2.57 | 2.57 | 0.09 |
|
Kidney wt, lb |
0.32 | 0.31 | 0.32 | 0.01 |
|
Visceral fat wt, lb |
3.46 | 3.40 | 3.41 | 0.27 |
|
Rumen/reticulum wt, lb |
2.55 | 2.56 | 2.60 | 0.06 |
|
Omasum wt, lb |
0.21 | 0.22 | 0.24 | 0.02 |
|
Abomasum wt, lb |
0.40 | 0.43 | 0.43 | 0.02 |
|
Small intestine wt, lb |
2.37 | 2.52 | 2.60 | 0.11 |
|
Cecum wt, lb |
0.15 | 0.17 | 0.15 | 0.01 |
|
Large intestine wt, lb |
1.04 | 1.13 | 1.19 | 0.07 |
|
Content wt, lb |
15.23a | 15.97a | 18.84b | 0.90 |
| a,b Means within a row with different superscripts differ (P < 0.05). | ||||
Lambs on expanded metal had the lowest leg conformation score, lambs on straw had the greatest leg conformation score, and lambs on sand were intermediate (P < 0.05) (Table 4). There were no other differences in carcass characteristics due to floor type and bedding.
Table 4. Effects of Pen Characteristics on Lamb Carcass Characteristics. |
|||
|---|---|---|---|
|
Item |
Expanded Metal | Sand | Straw |
|
No. of lambs |
20 | 20 | 19 |
|
Final wt, lb |
128.1 ± 1.8 | 130.5 ± 1.8 | 132.3 ± 1.8 |
|
Hot carcass wt, lb |
67.9 ± 1.1 | 69.8 ± 1.1 | 31.2 ± 1.1 |
|
Dressing, % |
52.9 ± 0.4 | 52.6 ± 0.4 | 52.0 ± 0.4 |
|
Fat depth, in |
0.21 ± 0.02 | 0.18 ± 0.02 | 0.18 ± 0.02 |
|
Leg conformationa |
11.0 ± 0.2b | 11.3 ± 0.2bc | 11.7 ± 0.2c |
|
Quality gradea |
11.1 ± 0.1 | 11.1 ± 0.1 | 11.3 ± 0.1 |
|
KPH fat1, % |
3.2 ± 0.1 | 3.1 ± 0.1 | 3.3 ± 0.1 |
|
Ribeye area, in2 |
2.94 ± 0.08 | 2.78 ± 0.08 | 2.94 ± 0.08 |
|
Yield graded |
3.3 ± 0.1 | 3.2 ± 0.1 | 3.1 ± 0.1 |
| 1 KPH fat = Kidney, pelvic, and
heart fat. a 10 = Choice- and 12 = Choice+. b,c Means within a row with different superscripts differ (P < 0.05). d 1.66 - (0.05 x leg conformation) + (0.25 x % KPH fat) + (6.66 x fat depth, inches). |
|||
Even though animal numbers were relatively small, lambs on expanded metal had the lowest production in each of the areas where differences were found. Recent advances in ethology (the study of animal behavior) have shown that production practices that result in stress or discomfort may result in slightly reduced productivity, but that the reductions are cumulative and together they can greatly reduce productivity (Curtis and Stricklin, 1991). Frustration and discomfort may result in increased animal aggression (Gonyou, 1994). The one animal that had to be removed from this experiment as a result of excessive wool picking was on the expanded metal floor. Fraser et al. (1991) reported that the lack of straw resulted in increased tailbiting in pigs vs. those animals with access to straw. It is possible that the relatively low feed intakes and forage content of the diet in the current experiment combined with differences in animal comfort due to differences in flooring and bedding were responsible for the animal responses found in the current experiment.
Implications
With high-concentrate, limit-fed diets, sand flooring and straw-bedded dirt floors resulted in improved animal performance compared to expanded metal floors. Straw consumption resulted in greater gut content weight but did not negatively affect average daily gain or feed efficiency.
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