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The effects of diet formulation, manufacturing technique, and antibiotic inclusion on broiler performance and intestinal morphology
©2010 Poultry Science Association, Inc.
The effects of diet formulation, manufacturing technique, and antibiotic inclusion on broiler performance and intestinal morphology N. P. Buchanan, K. G. S. Lilly, and J. S. Moritz1 Division of Animal and Nutritional Sciences, West Virginia University, Morgantown 26506 Primary Audience: Feed Mill Managers, Nutritionists, Researchers, Broiler Producers SUMMARY Optimizing the diet formulation and manufacturing technique improves pellet quality. However, high pellet quality must equate to improved broiler performance to justify the increased cost output. The objective of the current study was 2-fold: 1) to assess broiler performance based on changes in pellet quality obtained by altering the diet formulation and manufacturing technique, and 2) to assess broiler performance when using pelleted diets including and excluding antibiotics. Experimental treatments were arranged in a 2 × 2 × 2 factorial design consisting of 2 diet formulations (least cost or research based), 2 manufacturing techniques (thin die with a fast production rate or thick die with a slow production rate), and 2 antibiotic inclusions (including antibiotics or excluding antibiotics). Starter diets were fed in crumbled form and grower diets were fed in pelleted form. Antibiotic inclusion had no effect on broiler performance. Feeding the research-based formulation improved live weight gain and decreased fat pad yield compared with feeding the least-cost formulation. Moreover, the research-based formulation was found to be most beneficial for carcass and breast yield when the thin die plus fast production rate technique was used. In conclusion, to maximize broiler performance, the diet formulation and manufacturing technique must be considered. Key words: antibiotic, histology, nutrigenomics, pellet durability 2010 J. Appl. Poult. Res. 19:121–131 doi:10.3382/japr.2009-00071
DESCRIPTION OF PROBLEM The feed manufacturing process is costly both in capital investment and in execution [1]. Some of the benefits of pelleting include improved feed handling, decreased ingredient segregation, increased bulk density, and improved feed flow [2, 3]. However, maintaining high pellet quality from the feed mill to the feed pan is difficult. Scheideler [4] conducted a survey of 4 US broiler integrators and found that feed fines present at 1
Corresponding author: [email protected]
the pellet cooler averaged 33% of the total diet. Once feed was loaded into trucks and transported to the farm, feed fines increased to 59% of the total diet. Finally, once feed was augured to the feed pan inside the broiler house, feed fines increased to 63 to 72% of the total diet [4]. Failure to maintain a high pellet quality throughout transportation and conveyance has the potential to affect broiler performance negatively. High pellet quality is related to an increase in productive energy and thus an im-
122 provement in performance [5]. McKinney and Teeter [5] estimated that broilers could spare 187 kcal/kg of energy by consuming pellets with a pellet durability index (PDI) of 100 vs. a PDI of 0. In more practical terms, a 25 percentage point increase in PDI (61.72 vs. 87.29) has been associated with a decrease in feed conversion of 5 points while maintaining similar BW gain [6]. Moreover, small changes in pellets of very high quality (89.68 vs. 93.84) have been associated with even greater feed conversion enhancement while maintaining similar BW gain [7]. Conversely, poor management of pellet quality can increase feed conversion by as much as 13% [8]. These studies emphasize the importance of producing high-quality pellets that maintain structural integrity from the feed mill to the feed pan. There are several ways to manipulate pellet quality. Turner [9] postulated that 60% of the factors that affect pellet quality [diet formulation (40%); particle size (20%)] occur before the pelleting process, whereas the other 40% of factors [conditioning (20%); die specifications (15%); cooling (5%)] occur during the pelleting process. However, Turner [9] failed to consider interactions that may occur between these factors during the pelleting process. Buchanan and Moritz [10] reported that interactions exist between diet formulation and manufacturing technique [10]. Compared with a least-cost diet formulation, supplemental inclusion of protein [10, 11] and moisture [6, 12] improved pellet durability by 10 percentage points when the diets were manufactured using a thin die and a fast production rate. When the same diets were manufactured using a thick die and a slow production rate, pellet durability of the supplemented diet improved by only 6 percentage points [10]. High pellet quality is associated with an improvement in broiler performance [6, 7, 13] but is not without potential negative connotations. Pellets disintegrate in the crop and esophagus and pass directly through the proventriculus and gizzard. This process results in a greater presence of feed in the gastrointestinal tract (GIT) [14]. Alone, more feed in the GIT would not be considered a negative factor. However, more feed in the GIT provides a substrate for bacterial proliferation [14]. Engberg et al. [14] found greater concentrations of anaerobic bacteria in
JAPR: Research Report the gizzard and greater concentrations of coliform bacteria in the ileum of pellet-fed birds compared with mash-fed birds. Moreover, when finely ground feedstuffs are pelleted, even more coliforms are present in the GIT of broiler chickens [14]. An increased prevalence of pathogenic bacteria in the GIT may necessitate the use of subtherapeutic levels of antibiotics. Antibiotics are commonly fed to production animals in the United States to promote growth and to control disease [15]. However, consumer pressure has resulted in a reduction in antibiotic use in poultry feeds [16]. Sims et al. [16] found that the exclusion of antibiotics in pelleted turkey rations reduced 18-wk live weight by 4.7% but did not significantly affect feed conversion. The authors also noted an increase in the prevalence of Clostridium perfringens and a decrease in intestinal villus height in turkeys with the exclusion of antibiotics [16]. Long villi are typically equated with excellent gut health and high absorptive efficiency [16]; thus, a reduction in intestinal villus height might correspond to suboptimal health conditions. The objective of the current study was to evaluate the effects of varying pellet quality, obtained via manipulation of the diet formulation and manufacturing technique, on broiler performance and health. Additionally, the effects of antibiotic inclusion in pelleted diets were examined by evaluating broiler performance and intestinal morphology.
MATERIALS AND METHODS All animals were reared according to protocols established by the West Virginia University Animal Care and Use Committee. Diets and Treatments Diet formulations are represented in Table 1. Two diets, an industry-based least-cost diet (LC) and a modified research-based diet (RB), were formulated to meet Cobb-Vantress [17] nutrient recommendations for broilers (Table 1). The LC was formulated using feedstuffs common to commercial formulation. Nutrient specifications were imported into a commercially available feed formulation program, and the
Buchanan et al.: PELLET QUALITY AND PERFORMANCE program utilized least-cost formulation. The RB contained the same feedstuffs. However, based on past research by Buchanan and Moritz [10], this formulation contained an increased level of CP (3.87 percentage points) and was supplemented with moisture (tap water). The small changes in the RB formulation, although more expensive, have been shown to improve pellet quality. Moreover, these changes could easily be implemented in commercial poultry production if the benefits proved to be cost effective.
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Experimental treatments consisted of various pellet qualities obtained via manipulation of the diet formulation and manufacturing technique (Table 2) [10]. The LC and RB formulations were manufactured using 2 techniques: a thick die and slow production rate (TS) or a thin diet and a fast production rate (TF). This design resulted in a 2 (diet formulation) × 2 (manufacturing technique) factorial design. The precise experimental methodologies are described in the report by Buchanan et al. [10]. To mimic current
Table 1. Diet formulations and nutrient parameters Broiler starter diet Item Ingredient Corn Soybean meal (48%) Distillers grains with solubles Wheat middlings Meat and bone meal Animal-vegetable fat Dicalcium phosphate Limestone Lysine Methionine Salt NB30001 Threonine Coban 602 BMD3 Calculated nutrient ME, kcal/kg CP, % Calculated digestible amino acid Lysine Methionine Threonine TSAA Calculated total amino acid content, % Lysine Methionine Threonine Valine Arginine Tryptophan 1
Least cost
Research based
Broiler grower diet Least cost
Research based
55.03 26.75 5.00 5.00 2.53 2.00 1.23 0.79 0.41 0.36 0.34 0.25 0.18 0.08 0.05
46.15 34.92 5.00 5.00 4.63 2.00 0.69 0.52 0.06 0.31 0.31 0.25 0.03 0.08 0.05
61.84 19.55 5.00 5.00 3.00 2.00 1.02 0.78 0.55 0.38 0.26 0.25 0.23 0.08 0.05
53.30 27.38 5.00 5.00 5.04 2.00 0.50 0.53 0.23 0.33 0.22 0.25 0.09 0.08 0.05
3,028 21.50
3,028 25.37
3,172 19.50
3,172 23.37
1.33 0.69 0.85 1.03
1.33 0.69 0.85 1.03
1.25 0.68 0.80 1.01
1.25 0.68 0.80 1.01
1.38 0.67 0.87 1.05 1.41 0.26
1.40 0.68 0.87 1.26 1.74 0.32
1.31 0.67 0.83 0.92 1.19 0.22
1.35 0.67 0.84 1.12 1.52 0.27
Supplied per kilogram of diet: manganese, 0.02%; zinc, 0.02%; iron, 0.01%; copper, 0.0025%; iodine, 0.0003%; selenium, 0.00003%; folic acid, 0.69 mg; choline, 386 mg; riboflavin, 6.61 mg; biotin, 0.03 mg; vitamin B6, 1.38 mg; niacin, 27.56 mg; pantothenic acid, 6.61 mg; thiamine, 2.20 mg; menadione, 0.83 mg; vitamin B12, 0.01 mg; vitamin E, 16.53 IU; vitamin D3, 2,133 ICU; vitamin A, 7,716 IU. 2 Active drug ingredient monensin sodium at 60 g/lb (90 g/ton inclusion; Elanco Animal Health, Indianapolis, IN), as an aid in the prevention of coccidiosis caused by Eimeria necatrix, Eimeria tenella, Eimeria acervulina, Eimeria brunette, Eimeria mivati, and Eimeria maxima. 3 Bacitracin methylene disalicylate at 50 g/lb (50 g/ton inclusion; Alpharma, Fort Lee, NJ), for increased rate of BW gain and improved FE.
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124 Table 2. Crumble particle size and pellet quality of experimental treatments
Item Treatment3 Research-based diet using a thick die run slowly Least-cost diet using a thick die run slowly Research-based diet using a thin die run fast Least-cost diet using a thin die run fast P-value SEM Fisher’s LSD
Grower diet
Starter diet crumble particle size,1 μm
Modified pellet durability,2 %
Fines, %
2,080 1,702 1,720 1,271 — — —
89.47a 83.04b 79.48c 69.86d 0.0001 0.32 1.11
16.26d 20.75c 26.53b 33.64a 0.0001 0.78 2.69
a–d
Means within a column without a common superscript differ significantly (P ≤ 0.05). Nonreplicated descriptive data. 2 Modified pellet durability index (using five 13-mm hex nuts for added pressure on pellets). 3 Antibiotic inclusion was not a factor in determining pellet quality. For example, the research-based diet using a thick die run slowly with antibiotic had the same pellet durability as the research-based diet using a thick die run slowly without antibiotic. 1
industry practice, a third factor, antibiotic inclusion, was implemented. The inclusion of an antibiotic factor resulted in a 2 (diet formulation: LC or RB) × 2 (manufacturing technique: TS or TF) × 2 [antibiotic inclusion: 0 (No) or 0.05% (Anti) inclusion] factorial design comprising 8 total experimental treatments. For diets containing antibiotics, a 0.05% top-dressed inclusion of bacitracin methylene disalicylate [18] was added before pelleting. Broilers and Housing Each treatment was blocked by pen location and replicated 8 times. A total of 1,280 Cobb 500 male broilers [17] were sorted by BW and allotted to 1 of 64 floor pens [0.69 × 2.44 m (2.26 × 8.00 ft)] on d 3. Broilers were placed at a stocking density of 20 birds/pen and reared in a negative-pressure barn. Lighting, temperature, and ventilation were monitored and altered to create optimal rearing conditions. Temperature was initially set at 35°C (90°F) and was decreased by 5°F each week until the mean room temperature was 22°C (70°F). Each pen contained Ziggity nipple drinkers [19] and feed pans adapted to hoppers [20]. Chicks were given ad libitum access to the experimental treatments. Starter rations were fed in crumbled form from 3 to 21 d, and grower rations were fed in remixed pelleted form from 21 to 40 d. Remixed pellets were obtained by placing 91 kg (200 lb) of pellets into a vertical-screw mixer for 2 min. This method was meant to mimic the stressors associated
with transportation and conveyance. Percentages of fines obtained by remixing pellets corresponded to modified PDI (MPDI) values; thus, experimental treatments fed to broilers in this study would be indicative of feed that had been transported and conveyed (Table 2). All broilers were reared on built-up litter obtained from a commercial broiler house and transported to the West Virginia University poultry farm. Microbial analysis of the litter confirmed the presence of Escherichia coli and C. perfringens [21]. Broiler Performance Data Collection Live weight gain, feed intake, feed conversion, and percentage of mortality were determined from 3 to 21 d, 21 to 40 d, and 3 to 40 d. On d 40, three male broilers per pen, ±100 g of the mean pen BW, were processed at the West Virginia University pilot processing plant. Carcass weight, boneless, skinless breast yield, fat pad yield, and gizzard yield data were obtained. Intestinal Morphology On d 21 and 40, one male broiler per pen from blocks 2, 3, 6, and 7 was randomly selected and killed. The central ileum of each broiler was extracted and flushed with sterile water. A 2-cm section was removed and fixed in 10% neutral buffered formalin for histological evaluation. After paraffin embedding, 8-μm sections of tissue were cut, deparaffinized, and stained with hematoxylin and eosin. Villi were observed
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Table 3. Performance variables of 3- to 41-d broiler chickens Live weight gain, kg/bird
Feed intake, kg/pen
Feed conversion, kg/kg
Mortality, %
Treatment1 RB-TS-Anti RB-TF-Anti LC-TS-Anti LC-TF-Anti RB-TS-No RB-TF-No LC-TS-No LC-TF-No P-value SEM Fisher’s LSD
2.71abc 2.74a 2.68bcd 2.65cd 2.68abcd 2.72ab 2.65d 2.64d 0.0112 0.02 0.06
89.95 91.09 90.34 88.41 88.67 89.33 92.58 89.39 0.7808 1.81 —
1.86 1.82 1.87 1.83 1.83 1.83 1.90 1.84 0.7710 0.03 —
5.63 3.13 3.75 3.75 5.00 5.63 2.50 1.88 0.5826 1.56 —
Main effect and interaction, P-value Formulation Manufacturing technique Antibiotic Formulation × manufacturing technique Formulation × antibiotic Manufacturing technique × antibiotic Formulation × manufacturing technique × antibiotic
0.0002 0.6697 0.1758 0.0952 0.9455 0.6849 0.9901
0.7432 0.5204 0.9720 0.1827 0.2267 0.7343 0.8790
0.2772 0.1664 0.7261 0.5391 0.5536 0.9315 0.5121
0.0962 0.5743 0.7786 0.7786 0.2636 0.5743 0.4005
Item
a–d
Means within a column without a common superscript differ significantly (P ≤ 0.05). RB-TS-Anti = research-based diet + thick die run slowly with antibiotic; RB-TF-Anti = research-based diet + thin die run fast with antibiotic; LC-TS-Anti = least-cost diet + thick die run slowly with antibiotic; LC-TF-Anti = least-cost diet + thin die run fast with antibiotic; RB-TS-No = research-based diet + thick die run slowly with no antibiotic; RB-TF-No = research-based diet + thin die run fast with no antibiotic; LC-TS-No = least-cost diet + thick die run slowly with no antibiotic; LC-TF-No = least-cost diet + thin die run fast with no antibiotic. 1
microscopically using a light microscope set to 10× magnification. Villus height was measured from the tip of the villi to the crypt area and villus width was measure at half height. Measurements were based on at least 10 well-oriented villi per broiler. Villus surface area was calculated as a cylinder based on height and width at half height. Statistical Analysis Two separate statistical analyses were performed. A diet formulation × manufacturing technique × antibiotic inclusion factorial analysis was performed to explore the main effects and all possible interactions for broiler performance and intestinal histology. Additionally, multiple comparisons were performed. Significant differences were further explored using Fisher’s LSD test. Boneless, skinless breast yield, fat pad yield, and gizzard yield data were tested for normality. All statistics were calculated using the GLM procedure of the Statistical Analysis System [22]. Alpha was designated as 0.05.
RESULTS AND DISCUSSION Broiler Performance and Carcass Quality Table 3 contains performance data from 3 to 40 d. Only the overall growth period (3 to 40 d) is discussed unless more specific growth periods are needed to support overall observations. Table 4 describes the carcass characteristics of broilers processed on d 40. To negate the effects of varying live weight gain, the breast weight, fat pad weight, and gizzard weight were recorded as percentages of carcass weight. Antibiotic inclusion had no effect on broiler performance or carcass quality (P > 0.05; Table 3 and 4). Antibiotics are used at subtherapeutic levels to prevent disease and are most effective under conditions of stress (i.e., the presence of unfavorable microorganisms), extremes in ambient temperature, disease, crowding, and poor management [23]. To ensure a typical production challenge, broilers were reared on built-up litter obtained from a commercial poultry house. After completion of the study, analysis of the lit-
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126 Table 4. Carcass characteristics of 40-d broiler chickens Carcass, kg
Breast, % of carcass
Fat pad, % of carcass
Gizzard, % of carcass
Treatment1 RB-TS-Anti RB-TF-Anti LC-TS-Anti LC-TF-Anti RB-TS-No RB-TF-No LC-TS-No LC-TF-No P-value SEM Fisher’s LSD
2.04bc 2.11a 2.05bc 2.01c 2.06ab 2.07ab 2.02bc 2.00c 0.0015 0.02 0.05
32.07ab 32.52a 31.28bc 30.78c 31.12bc 32.14ab 31.41abc 30.67c 0.0095 0.41 1.13
1.47c 1.31c 1.95ab 1.85ab 1.62bc 1.39c 2.06a 2.06a 0.0001 0.12 0.34
1.88 1.92 1.91 2.09 2.01 1.96 2.02 2.14 0.0883 0.07 —
Main effect and interaction, P-value Formulation Manufacturing technique Antibiotic Formulation × manufacturing technique Formulation × antibiotic Manufacturing technique × antibiotic Formulation × manufacturing technique × antibiotic
0.0002 0.9951 0.3404 0.0132 0.7010 0.4424 0.1969
0.0015 0.8417 0.2506 0.0194 0.2421 0.7639 0.4812
0.0001 0.1666 0.1085 0.4128 0.7630 0.9351 0.6262
0.0375 0.1459 0.0911 0.1126 0.9230 0.4212 0.8379
Item
a–c
Means within a column without a common superscript differ significantly (P ≤ 0.05). RB-TS-Anti = research-based diet + thick die run slowly with antibiotic; RB-TF-Anti = research-based diet + thin die run fast with antibiotic; LC-TS-Anti = least-cost diet + thick die run slowly with antibiotic; LC-TF-Anti = least-cost diet + thin die run fast with antibiotic; RB-TS-No = research-based diet + thick die run slowly with no antibiotic; RB-TF-No = research-based diet + thin die run fast with no antibiotic; LC-TS-No = least-cost diet + thick die run slowly with no antibiotic; LC-TF-No = least-cost diet + thin die run fast with no antibiotic. 1
ter bed confirmed the presence of the unfavorable microorganisms E. coli (2.5 million/g of dry litter) and C. perfringens (10,500/g of dry litter). However, extreme changes in ambient temperatures, crowding, and poor management did not occur. Therefore, it is likely that the broilers were not exposed to a challenge sufficient to induce a response associated with antibiotic inclusion. Live weight gain and feed conversion trends did not follow changes in pellet quality. Broilers fed the treatments with the highest pellet quality [RB-TS-Anti and RB-TS-No; MPDI = 89.47, fines = 16.26%] did not exhibit improved live weight gain or feed conversion (P > 0.05) compared with broilers fed the treatments with the lowest pellet quality [LC-TF-Anti and LC-TFNo; MPDI = 69.86, fines = 33.64%]. Despite attempts to produce experimental treatments that would mimic current industry pellet quality, the pellets fed in this study could still be considered high quality. The MPDI values ranged from 69.86 to 89.47% and percentage of fines ranged
from 33.64 to 16.26% (Table 2). Greenwood et al. [13] found that broilers fed diets containing 20 and 30% fines did not differ in BW gain or feed conversion. Additionally, Moritz et al. [6] found a 5-point improvement in feed conversion with a 25 percentage point increase in the PDI. However, the PDI values used by Moritz et al. [6] ranged from 61.72 to 87.29, a greater range than the one used in this study. Cutlip et al. [7] found a 20-point improvement in feed conversion when the PDI improved from 89.68 to 93.84, above the PDI range for the current study. It is plausible that the pellet quality used in the study fell into a neutral zone for broiler performance. Despite broiler performance not being directly affected by pellet quality, formulation main effects were observed. Feeding the RB diet formulation resulted in higher broiler live weight gain (P = 0.0002) and lower fat pad (P = 0.0001) and gizzard yields (P = 0.0375) compared with feeding the LC diet formulation. The RB and LC diets were formulated to have the same digest-
Buchanan et al.: PELLET QUALITY AND PERFORMANCE ible amino acid content for methionine, lysine, threonine, and TSAA (Table 1). Additionally, all diet formulations met or exceeded total amino acid recommendations established by CobbVantress [17]. However, the RB diet had higher total amino acid contents for valine, arginine, and tryptophan (Table 1) and an overall increase in CP of 3.87 percentage points. The most efficient utilization of amino acids occurs when broilers are fed concentrations at or below, not above, their requirement [24]. However, positive performance has been correlated with the feeding of excess amino acids. Corzo et al. [24] reported increased BW, decreased fat accretion, and higher breast fillet and tender yields when broilers were fed diets with excess concentrations of essential amino acids. Additionally, Bartov and Plavnik [25] reported increased breast meat yield when broilers were fed diets with moderate excesses in CP. A formulation × manufacturing technique interaction was observed for carcass weight (P = 0.01) and breast yield (P = 0.02). Carcass weight and breast yield were not different for broilers fed either diet formulation manufactured using TS (P > 0.05). However, when the same diets were manufactured using TF, the RB resulted in a marked increase in carcass weight and breast yield compared with the LC. By design, use of TS would result in a longer retention time in the die; thus, feed would have greater exposure to heat. The combination of heat and moisture found in the pelleting process could lead to Maillard reaction products that reduce the availability of essential amino acids, most notably lysine [26]. Perhaps the use of TS resulted in some denaturation of proteins during processing that created decreased amino acid digestibility. Therefore, birds fed the RB-TF treatment, formulated with higher concentrations of amino acids and manufactured with less exposure to heat, had the most potential to utilize amino acids for muscle accretion. Feed intake and mortality were not affected by experimental treatments (P > 0.05). Intestinal Morphology Table 5 contains intestinal morphology data obtained from 21-d broilers, whereas Table 6 contains intestinal morphology data obtained from 40-d broilers. A significant diet formulation × manufacturing technique × antibiotic
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inclusion interaction was observed for 21-d villus height and surface area (P = 0.0213; P = 0.0001, respectively). Inclusion of antibiotic in the starter diets resulted in lower villus heights for all treatments, with the exception of LC-TF. The most dramatic change in 21-d villus height was for the antibiotic in the RB-TS treatment. Inclusion of antibiotic in the RB-TS treatment reduced villus height by 23.6% compared with RB-TS with no antibiotic. Although antibiotic inclusion did not affect broiler performance for the duration of the experiment, a significant antibiotic effect was observed for the 3- to 21-d period. Antibiotic inclusion improved live weight gain (P = 0.002; data not presented), with broilers fed the RB-TS-Anti diet having greater live weight gain than broilers fed the RB-TS-No diet (P < 0.05). Villus surface area did not differ for broilers fed the starter diets manufactured using the TF technique despite antibiotic inclusion. However, antibiotic inclusion reduced villus surface area for broilers fed RB-TS and increased villus surface area for broilers fed LC-TS. However, 21-d villus surface area did not correspond to changes in 21-d broiler live weight gain (data not presented). A significant diet formulation × manufacturing technique × antibiotic inclusion interaction was also observed for villus height in 40-d broilers (P = 0.0001). However, antibiotic inclusion had the opposite effect on villus height in this period compared with the 21-d broilers. Antibiotic inclusion in the grower diets increased villus height, with the exception of the LC-TS treatment. Antibiotic inclusion in the LC-TS treatment decreased villus height compared with the exclusion of antibiotic. Larger villus height is associated with a healthier intestinal tract [16], whereas shorter villus height is largely associated with the presence of a challenge [27]. We suggest that the change in villus height from the 21- to 40-d period associated with antibiotic inclusion did improve the health of the GIT for the duration of the experiment. However, this effect was not sufficient to elicit a growth response. A diet formulation × manufacturing technique interaction affected villus surface area for 40-d broilers (P = 0.0074). Broilers fed diets manufactured using TF had a greater villus surface area compared with broilers fed diets
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128 manufactured using TS; however, no difference in villus surface area was observed between the RB and LC formulations. In contrast, when the same diets were manufactured using TS, the surface area of the RB treatment was much lower than the surface area of the LC treatment. Perhaps the greater surface area for broilers fed the diets manufactured using TF aided in the improvement in carcass weight and breast yield observed for broilers fed the RB-TF treatments. At this time, the authors cannot speculate on the mechanism responsible for these findings. Economic Analysis The monetary investment needed to make high-quality pellets is well established. After capital investment, the majority of cost is associated with 1) ingredients, 2) labor, and 3) energy use [28]. Although tap water is very inexpensive, adding supplemental protein in any form is a costly investment [29]. Moreover, using a thick die and slowing the production rate increases energy use, thus increasing the cost of production.
Therefore, a basic economic analysis was conducted to correlate the cost of production with the profit from the final product. With current prices [29], the ingredients needed to formulate the LC would cost $370.64/metric ton ($336.17/ ton). The ingredients used to compose the RB formulations would cost $377.42/metric ton ($342.32/ton). The local rate for high-use electricity is $0.02327/kW·h [30]. With these price estimations and feed consumption amounts per treatment, the total cost of the 4 pelleted diets was calculated (Table 7). Additionally, the total amount of boneless, skinless chicken breast yield was calculated (Table 7). Taking into consideration the total cost of manufacturing a diet and dividing that value by the total product produced, we calculated the production cost ($/unit of product; Table 7) [31]. The total cost of the LC-TF treatment ($530.08) in this study was less than the total cost of all other treatments. The cost of ingredients and electricity for this treatment was the lowest, and these broilers consumed a low volume of feed relative to broilers fed the other
Table 5. Intestinal morphology of 21-d broiler chickens Item Treatment1 RB-TS-Anti RB-TF-Anti LC-TS-Anti LC-TF-Anti RB-TS-No RB-TF-No LC-TS-No LC-TF-No P-value SEM Fisher’s LSD Main effect and interaction, P-value Formulation Manufacturing technique Antibiotic Formulation × manufacturing technique Formulation × antibiotic Manufacturing technique × antibiotic Formulation × manufacturing technique × antibiotic a–e
Villus height, μm
Villus surface area, mm2
518.5e 584.4cd 565.6d 564.7d 678.9a 630.2b 613.9bc 575.3d 0.0001 11.8 32.8
264.9c 369.4b 359.8b 371.2b 425.6a 371.7b 281.3c 374.2b 0.0001 15.5 43.0
0.0057 0.5035 0.0001 0.0903 0.0001 0.0001 0.0213
0.3035 0.0004 0.0466 0.2213 0.0001 0.0796 0.0001
Means within a column without a common superscript differ significantly (P ≤ 0.05). RB-TS-Anti = research-based diet + thick die run slowly with antibiotic; RB-TF-Anti = research-based diet + thin die run fast with antibiotic; LC-TS-Anti = least-cost diet + thick die run slowly with antibiotic; LC-TF-Anti = least-cost diet + thin die run fast with antibiotic; RB-TS-No = research-based diet + thick die run slowly with no antibiotic; RB-TF-No = research-based diet + thin die run fast with no antibiotic; LC-TS-No = least-cost diet + thick die run slowly with no antibiotic; LC-TF-No = least-cost diet + thin die run fast with no antibiotic. 1
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Table 6. Intestinal morphology of 40-d broiler chickens
Item Treatment1 RB-TS-Anti RB-TF-Anti LC-TS-Anti LC-TF-Anti RB-TS-No RB-TF-No LC-TS-No LC-TF-No P-value SEM Fisher’s LSD Main effect and interaction, P-value Formulation Manufacturing technique Antibiotic Formulation × manufacturing technique Formulation × antibiotic Manufacturing technique × antibiotic Formulation × manufacturing technique × antibiotic
Villus height, μm
Villus surface area, mm2
724.6c 854.9a 727.5c 865.3a 640.8d 782.3b 848.2a 772.4bc 0.0001 19.0 52.9
365.6de 495.3ab 407.1cd 470.4abc 330.7e 518.5a 432.8bc 509.9a 0.0001 23.2 64.6
0.0001 0.0001 0.0173 0.0001 0.0007 0.0002 0.0001
0.0952 0.0001 0.4162 0.0074 0.2424 0.2744 0.5013
a–e
Means within a column without a common superscript differ significantly (P ≤ 0.05). RB-TS-Anti = research-based diet + thick die run slowly with antibiotic; RB-TF-Anti = research-based diet + thin die run fast with antibiotic; LC-TS-Anti = least-cost diet + thick die run slowly with antibiotic; LC-TF-Anti = least-cost diet + thin die run fast with antibiotic; RB-TS-No = research-based diet + thick die run slowly with no antibiotic; RB-TF-No = research-based diet + thin die run fast with no antibiotic; LC-TS-No = least-cost diet + thick die run slowly with no antibiotic; LC-TF-No = least-cost diet + thin die run fast with no antibiotic. 1
treatments. However, these broilers also produced a low yield of boneless, skinless breast tissue. In contrast, the broilers fed the RB-TF treatment produced a high yield of boneless, skinless breast tissue (Table 4). Even though the
RB-TF feed cost more ($544.48), the increase in boneless, skinless breast yield corresponded to a savings in production costs of $0.14/kg compared with broilers fed the LC-TF treatments (Table 7). Therefore, it is evident that the
Table 7. Basic economic analysis of boneless, skinless breast production using different diet formulation and feed manufacturing techniques1 Treatment2 RB-TS RB-TF LC-TS LC-TF 1
Total cost of feed, $
Boneless, skinless breast produced, kg
Production cost,3 $/kg
Savings,4 $/kg
538.88 544.48 546.56 530.08
175.84 185.29 177.60 172.16
3.06 2.94 3.08 3.08
+0.02 +0.14 +0.00 —
Nonreplicated descriptive data. Cost of feed ingredients for the research-based diet was $377.42/metric ton. Cost of feed ingredients for the least-cost diet was $370.64/metric ton. 2 RB-TS = research-based diet manufactured using a thick die run slowly; RB-TF = research-based diet manufactured using a thin die run fast; LC-TS = least-cost diet manufactured using a thick die run slowly; LC-TF = least-cost diet manufactured using a thin die run slowly. 3 Production cost = total cost of feed/total product produced. 4 Production cost compared with the production cost of LC-TF. The LC-TF was chosen because it is the combination of diet formulation and manufacturing technique that is often used in the commercial feed industry.
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130 increased ingredient cost of an RB formulation could be justified by the greater return in boneless, skinless chicken breast yield. This research emphasizes the impact of the diet formulation and manufacturing technique on pellet quality and subsequent broiler performance and yield. The authors appreciate that additional factors affect pellet quality. However, because of the improved carcass weight and breast yield, commercial integrated feed mills may be able to justify the increased cost associated with the use of diet formulations with higher protein and moisture.
CONCLUSIONS AND APPLICATIONS
1. The RB formulations improved broiler growth and decreased fat pad yield compared with the LC formulations. 2. Carcass quality was influenced by the interactions that occurred between diet formulation and manufacturing technique. 3. Antibiotic inclusion in high-quality broiler diets had no effect on broiler performance but did affect villus height, an indicator of good intestinal health. 4. Using a RB formulation manufactured using a thin die and a fast production rate resulted in a $0.14/kg savings compared with using an LC formulation manufactured in the same manner.
REFERENCES AND NOTES 1. Moritz, J. S. 2007. Impact of the pelleting process on dietary nutrients and supplemental enzymes. Pages 11–13 in Proc. Arkansas Annu. Nutr. Conf., Rogers, AR. 2. Fairfield, D. A. 2003. Pelleting for profit—Part 1. Feed Feeding Dig. 54:1–5. 3. Behnke, K. C. 1994. Factors affecting pellet quality. Pages 44–54 in Proc. Maryland Nutr. Conf. Feed Manuf., College Park. Maryland Feed Ind. Counc. and Univ. Maryland, College Park. 4. Scheideler, S. E. 1995. Poultry feeds: Is pelleting cost effective? Feed Manage. 46:21–26. 5. McKinney, L. J., and R. G. Teeter. 2004. Predicting effective caloric value of nonnutritive factors: I. Pellet quality and II. Consequential formulation dead zones. Poult. Sci. 83:1165–1174. 6. Moritz, J. S., R. S. Beyer, K. J. Wilson, K. R. Cramer, L. J. McKinney, and F. J. Fairchild. 2001. Effect of moisture addition at the mixer to a corn-soybean-based diet on broiler performance. J. Appl. Poult. Res. 10:347–353. 7. Cutlip, S. E., J. M. Hott, N. P. Buchanan, and J. S. Moritz. 2008. Effect of steam conditioning practices on pel-
let quality and growing broiler nutritional value. J. Appl. Poult. Res. 17:249–261. 8. Winowiski, T. 1988. Wheat and pellet quality. Feed Manage. 39:58–64. 9. Turner, R. 1995. Bottomline in feed processing— Achieving optimum pellet quality. Feedstuffs 46:30–33. 10. Buchanan, N. P., K. G. S. Lilly, C. K. Gehring, and J. S. Moritz. 2010. The effects of altering diet formulation and manufacturing technique on pellet quality. J. Appl. Poult. Res. 19:112–120. 11. Briggs, J. L., D. E. Maier, B. A. Watkins, and K. C. Behnke. 1999. Effect of ingredients and processing parameters on pellet quality. Poult. Sci. 78:1464–1471. 12. Fairchild, F., and D. Greer. 1999. Pelleting with precise mixer moisture control. Feed Int. 20:32–36. 13. Greenwood, M. W., P. M. Clark, and R. S. Beyer. 2004. Effect of feed fines level on broilers fed two concentrations of dietary lysine from 14 to 30 days of age. Int. J. Poult. Sci. 3:446–449. 14. Engberg, R. M., M. S. Hedeman, and B. B. Jensen. 2002. The influence of grinding and pelleting of feed on the microbial composition and activity in the digestive tract of broiler chickens. Br. Poult. Sci. 44:569–579. 15. Centers for Disease Control and Prevention. 2005. National Antimicrobial Resistance Monitoring System (NARMS) Frequently Asked Questions (FAQ) About Antibiotic Resistance—Why are antibiotics used in food-producing animals? http://www.cdc.gov/narms/faq_pages/7. htm Accessed March 2007. 16. Sims, M. D., K. A. Dawson, K. E. Newman, P. Spring, and D. M. Hooge. 2004. Effects of dietary mannan oligosaccharide, bacitracin methylene disalicylate, or both on the live performance and intestinal microbiology of turkeys. Poult. Sci. 83:1148–1154. 17. Cobb-Vantress Inc., Siloam Springs, AR. 18. Bacitracin methylene disalicylate, Alpharma Inc., Bridgewater, NJ. 19. Water system, Ziggity Systems Inc., Middlebury, IN. 20. Feed pan and hopper, Kuhl Corporation, Flemington, NJ. 21. Superior Laboratories Inc., Galloway, OH. 22. SAS Institute. 2000. The SAS System for Windows 2000. Release 8.1. SAS Inst. Inc., Cary, NC. 23. USDA, Agricultural Research Service. 1972. Antibiotics in animal and poultry feeds—A critical review of research. Publ. 44-237. USDA, Agric. Res. Serv., Washington, DC. 24. Corzo, A., M. T. Kidd, D. J. Burnham, E. R. Miller, S. L. Branton, and R. Gonzalez-Esquerra. 2005. Dietary amino acid density effects on growth and carcass of broilers differing in strain cross and sex. J. Appl. Poult. Res. 14:1–9. 25. Bartov, I., and I. Plavnik. 1998. Moderate excess of dietary protein increased breast meat yield of broiler chicks. Poult. Sci. 77:680–688. 26. Beyer, R. S. 2000. The impact of feed milling and manufacturing procedures on nutrient availability and microbial content of poultry feed. Pages 151–162 in 2000 California Anim. Nutr. Conf. PG Ag Products, Fresno, CA. 27. Alfaro, D. M., A. V. F. Silva, S. A. Borges, F. A. Maiorka, S. Vargas, and E. Santin. 2007. Use of Yucca schidigera extract in broiler diets and its effects on performance results obtained with different coccidiosis control methods. J. Appl. Poult. Res. 16:248–254.
Buchanan et al.: PELLET QUALITY AND PERFORMANCE 28. Behnke, K. C. 2008. Department of Grain Science and Industry, Kansas State University, Manhattan. Personal communication. 29. USDA. 2008. Current grain prices. http://search.ams. usda.gov/mndms/2008/07/LS20080725WGRSTOCK.PDF Accessed July 2008.
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30. Allegheny Energy, Greensburg, PA. 31. Methods for calculating production cost and savings: 1) production cost = (cost of feed × feed intake) + energy use during manufacture/boneless, skinless breast weight; 2) savings = production cost of LC-TF − production cost of treatment.
The effects of diet formulation, manufacturing technique, and antibiotic inclusion on broiler performance and intestinal morphology N. P. Buchanan, K. G. S. Lilly, and J. S. Moritz1 Division of Animal and Nutritional Sciences, West Virginia University, Morgantown 26506 Primary Audience: Feed Mill Managers, Nutritionists, Researchers, Broiler Producers SUMMARY Optimizing the diet formulation and manufacturing technique improves pellet quality. However, high pellet quality must equate to improved broiler performance to justify the increased cost output. The objective of the current study was 2-fold: 1) to assess broiler performance based on changes in pellet quality obtained by altering the diet formulation and manufacturing technique, and 2) to assess broiler performance when using pelleted diets including and excluding antibiotics. Experimental treatments were arranged in a 2 × 2 × 2 factorial design consisting of 2 diet formulations (least cost or research based), 2 manufacturing techniques (thin die with a fast production rate or thick die with a slow production rate), and 2 antibiotic inclusions (including antibiotics or excluding antibiotics). Starter diets were fed in crumbled form and grower diets were fed in pelleted form. Antibiotic inclusion had no effect on broiler performance. Feeding the research-based formulation improved live weight gain and decreased fat pad yield compared with feeding the least-cost formulation. Moreover, the research-based formulation was found to be most beneficial for carcass and breast yield when the thin die plus fast production rate technique was used. In conclusion, to maximize broiler performance, the diet formulation and manufacturing technique must be considered. Key words: antibiotic, histology, nutrigenomics, pellet durability 2010 J. Appl. Poult. Res. 19:121–131 doi:10.3382/japr.2009-00071
DESCRIPTION OF PROBLEM The feed manufacturing process is costly both in capital investment and in execution [1]. Some of the benefits of pelleting include improved feed handling, decreased ingredient segregation, increased bulk density, and improved feed flow [2, 3]. However, maintaining high pellet quality from the feed mill to the feed pan is difficult. Scheideler [4] conducted a survey of 4 US broiler integrators and found that feed fines present at 1
Corresponding author: [email protected]
the pellet cooler averaged 33% of the total diet. Once feed was loaded into trucks and transported to the farm, feed fines increased to 59% of the total diet. Finally, once feed was augured to the feed pan inside the broiler house, feed fines increased to 63 to 72% of the total diet [4]. Failure to maintain a high pellet quality throughout transportation and conveyance has the potential to affect broiler performance negatively. High pellet quality is related to an increase in productive energy and thus an im-
122 provement in performance [5]. McKinney and Teeter [5] estimated that broilers could spare 187 kcal/kg of energy by consuming pellets with a pellet durability index (PDI) of 100 vs. a PDI of 0. In more practical terms, a 25 percentage point increase in PDI (61.72 vs. 87.29) has been associated with a decrease in feed conversion of 5 points while maintaining similar BW gain [6]. Moreover, small changes in pellets of very high quality (89.68 vs. 93.84) have been associated with even greater feed conversion enhancement while maintaining similar BW gain [7]. Conversely, poor management of pellet quality can increase feed conversion by as much as 13% [8]. These studies emphasize the importance of producing high-quality pellets that maintain structural integrity from the feed mill to the feed pan. There are several ways to manipulate pellet quality. Turner [9] postulated that 60% of the factors that affect pellet quality [diet formulation (40%); particle size (20%)] occur before the pelleting process, whereas the other 40% of factors [conditioning (20%); die specifications (15%); cooling (5%)] occur during the pelleting process. However, Turner [9] failed to consider interactions that may occur between these factors during the pelleting process. Buchanan and Moritz [10] reported that interactions exist between diet formulation and manufacturing technique [10]. Compared with a least-cost diet formulation, supplemental inclusion of protein [10, 11] and moisture [6, 12] improved pellet durability by 10 percentage points when the diets were manufactured using a thin die and a fast production rate. When the same diets were manufactured using a thick die and a slow production rate, pellet durability of the supplemented diet improved by only 6 percentage points [10]. High pellet quality is associated with an improvement in broiler performance [6, 7, 13] but is not without potential negative connotations. Pellets disintegrate in the crop and esophagus and pass directly through the proventriculus and gizzard. This process results in a greater presence of feed in the gastrointestinal tract (GIT) [14]. Alone, more feed in the GIT would not be considered a negative factor. However, more feed in the GIT provides a substrate for bacterial proliferation [14]. Engberg et al. [14] found greater concentrations of anaerobic bacteria in
JAPR: Research Report the gizzard and greater concentrations of coliform bacteria in the ileum of pellet-fed birds compared with mash-fed birds. Moreover, when finely ground feedstuffs are pelleted, even more coliforms are present in the GIT of broiler chickens [14]. An increased prevalence of pathogenic bacteria in the GIT may necessitate the use of subtherapeutic levels of antibiotics. Antibiotics are commonly fed to production animals in the United States to promote growth and to control disease [15]. However, consumer pressure has resulted in a reduction in antibiotic use in poultry feeds [16]. Sims et al. [16] found that the exclusion of antibiotics in pelleted turkey rations reduced 18-wk live weight by 4.7% but did not significantly affect feed conversion. The authors also noted an increase in the prevalence of Clostridium perfringens and a decrease in intestinal villus height in turkeys with the exclusion of antibiotics [16]. Long villi are typically equated with excellent gut health and high absorptive efficiency [16]; thus, a reduction in intestinal villus height might correspond to suboptimal health conditions. The objective of the current study was to evaluate the effects of varying pellet quality, obtained via manipulation of the diet formulation and manufacturing technique, on broiler performance and health. Additionally, the effects of antibiotic inclusion in pelleted diets were examined by evaluating broiler performance and intestinal morphology.
MATERIALS AND METHODS All animals were reared according to protocols established by the West Virginia University Animal Care and Use Committee. Diets and Treatments Diet formulations are represented in Table 1. Two diets, an industry-based least-cost diet (LC) and a modified research-based diet (RB), were formulated to meet Cobb-Vantress [17] nutrient recommendations for broilers (Table 1). The LC was formulated using feedstuffs common to commercial formulation. Nutrient specifications were imported into a commercially available feed formulation program, and the
Buchanan et al.: PELLET QUALITY AND PERFORMANCE program utilized least-cost formulation. The RB contained the same feedstuffs. However, based on past research by Buchanan and Moritz [10], this formulation contained an increased level of CP (3.87 percentage points) and was supplemented with moisture (tap water). The small changes in the RB formulation, although more expensive, have been shown to improve pellet quality. Moreover, these changes could easily be implemented in commercial poultry production if the benefits proved to be cost effective.
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Experimental treatments consisted of various pellet qualities obtained via manipulation of the diet formulation and manufacturing technique (Table 2) [10]. The LC and RB formulations were manufactured using 2 techniques: a thick die and slow production rate (TS) or a thin diet and a fast production rate (TF). This design resulted in a 2 (diet formulation) × 2 (manufacturing technique) factorial design. The precise experimental methodologies are described in the report by Buchanan et al. [10]. To mimic current
Table 1. Diet formulations and nutrient parameters Broiler starter diet Item Ingredient Corn Soybean meal (48%) Distillers grains with solubles Wheat middlings Meat and bone meal Animal-vegetable fat Dicalcium phosphate Limestone Lysine Methionine Salt NB30001 Threonine Coban 602 BMD3 Calculated nutrient ME, kcal/kg CP, % Calculated digestible amino acid Lysine Methionine Threonine TSAA Calculated total amino acid content, % Lysine Methionine Threonine Valine Arginine Tryptophan 1
Least cost
Research based
Broiler grower diet Least cost
Research based
55.03 26.75 5.00 5.00 2.53 2.00 1.23 0.79 0.41 0.36 0.34 0.25 0.18 0.08 0.05
46.15 34.92 5.00 5.00 4.63 2.00 0.69 0.52 0.06 0.31 0.31 0.25 0.03 0.08 0.05
61.84 19.55 5.00 5.00 3.00 2.00 1.02 0.78 0.55 0.38 0.26 0.25 0.23 0.08 0.05
53.30 27.38 5.00 5.00 5.04 2.00 0.50 0.53 0.23 0.33 0.22 0.25 0.09 0.08 0.05
3,028 21.50
3,028 25.37
3,172 19.50
3,172 23.37
1.33 0.69 0.85 1.03
1.33 0.69 0.85 1.03
1.25 0.68 0.80 1.01
1.25 0.68 0.80 1.01
1.38 0.67 0.87 1.05 1.41 0.26
1.40 0.68 0.87 1.26 1.74 0.32
1.31 0.67 0.83 0.92 1.19 0.22
1.35 0.67 0.84 1.12 1.52 0.27
Supplied per kilogram of diet: manganese, 0.02%; zinc, 0.02%; iron, 0.01%; copper, 0.0025%; iodine, 0.0003%; selenium, 0.00003%; folic acid, 0.69 mg; choline, 386 mg; riboflavin, 6.61 mg; biotin, 0.03 mg; vitamin B6, 1.38 mg; niacin, 27.56 mg; pantothenic acid, 6.61 mg; thiamine, 2.20 mg; menadione, 0.83 mg; vitamin B12, 0.01 mg; vitamin E, 16.53 IU; vitamin D3, 2,133 ICU; vitamin A, 7,716 IU. 2 Active drug ingredient monensin sodium at 60 g/lb (90 g/ton inclusion; Elanco Animal Health, Indianapolis, IN), as an aid in the prevention of coccidiosis caused by Eimeria necatrix, Eimeria tenella, Eimeria acervulina, Eimeria brunette, Eimeria mivati, and Eimeria maxima. 3 Bacitracin methylene disalicylate at 50 g/lb (50 g/ton inclusion; Alpharma, Fort Lee, NJ), for increased rate of BW gain and improved FE.
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124 Table 2. Crumble particle size and pellet quality of experimental treatments
Item Treatment3 Research-based diet using a thick die run slowly Least-cost diet using a thick die run slowly Research-based diet using a thin die run fast Least-cost diet using a thin die run fast P-value SEM Fisher’s LSD
Grower diet
Starter diet crumble particle size,1 μm
Modified pellet durability,2 %
Fines, %
2,080 1,702 1,720 1,271 — — —
89.47a 83.04b 79.48c 69.86d 0.0001 0.32 1.11
16.26d 20.75c 26.53b 33.64a 0.0001 0.78 2.69
a–d
Means within a column without a common superscript differ significantly (P ≤ 0.05). Nonreplicated descriptive data. 2 Modified pellet durability index (using five 13-mm hex nuts for added pressure on pellets). 3 Antibiotic inclusion was not a factor in determining pellet quality. For example, the research-based diet using a thick die run slowly with antibiotic had the same pellet durability as the research-based diet using a thick die run slowly without antibiotic. 1
industry practice, a third factor, antibiotic inclusion, was implemented. The inclusion of an antibiotic factor resulted in a 2 (diet formulation: LC or RB) × 2 (manufacturing technique: TS or TF) × 2 [antibiotic inclusion: 0 (No) or 0.05% (Anti) inclusion] factorial design comprising 8 total experimental treatments. For diets containing antibiotics, a 0.05% top-dressed inclusion of bacitracin methylene disalicylate [18] was added before pelleting. Broilers and Housing Each treatment was blocked by pen location and replicated 8 times. A total of 1,280 Cobb 500 male broilers [17] were sorted by BW and allotted to 1 of 64 floor pens [0.69 × 2.44 m (2.26 × 8.00 ft)] on d 3. Broilers were placed at a stocking density of 20 birds/pen and reared in a negative-pressure barn. Lighting, temperature, and ventilation were monitored and altered to create optimal rearing conditions. Temperature was initially set at 35°C (90°F) and was decreased by 5°F each week until the mean room temperature was 22°C (70°F). Each pen contained Ziggity nipple drinkers [19] and feed pans adapted to hoppers [20]. Chicks were given ad libitum access to the experimental treatments. Starter rations were fed in crumbled form from 3 to 21 d, and grower rations were fed in remixed pelleted form from 21 to 40 d. Remixed pellets were obtained by placing 91 kg (200 lb) of pellets into a vertical-screw mixer for 2 min. This method was meant to mimic the stressors associated
with transportation and conveyance. Percentages of fines obtained by remixing pellets corresponded to modified PDI (MPDI) values; thus, experimental treatments fed to broilers in this study would be indicative of feed that had been transported and conveyed (Table 2). All broilers were reared on built-up litter obtained from a commercial broiler house and transported to the West Virginia University poultry farm. Microbial analysis of the litter confirmed the presence of Escherichia coli and C. perfringens [21]. Broiler Performance Data Collection Live weight gain, feed intake, feed conversion, and percentage of mortality were determined from 3 to 21 d, 21 to 40 d, and 3 to 40 d. On d 40, three male broilers per pen, ±100 g of the mean pen BW, were processed at the West Virginia University pilot processing plant. Carcass weight, boneless, skinless breast yield, fat pad yield, and gizzard yield data were obtained. Intestinal Morphology On d 21 and 40, one male broiler per pen from blocks 2, 3, 6, and 7 was randomly selected and killed. The central ileum of each broiler was extracted and flushed with sterile water. A 2-cm section was removed and fixed in 10% neutral buffered formalin for histological evaluation. After paraffin embedding, 8-μm sections of tissue were cut, deparaffinized, and stained with hematoxylin and eosin. Villi were observed
Buchanan et al.: PELLET QUALITY AND PERFORMANCE
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Table 3. Performance variables of 3- to 41-d broiler chickens Live weight gain, kg/bird
Feed intake, kg/pen
Feed conversion, kg/kg
Mortality, %
Treatment1 RB-TS-Anti RB-TF-Anti LC-TS-Anti LC-TF-Anti RB-TS-No RB-TF-No LC-TS-No LC-TF-No P-value SEM Fisher’s LSD
2.71abc 2.74a 2.68bcd 2.65cd 2.68abcd 2.72ab 2.65d 2.64d 0.0112 0.02 0.06
89.95 91.09 90.34 88.41 88.67 89.33 92.58 89.39 0.7808 1.81 —
1.86 1.82 1.87 1.83 1.83 1.83 1.90 1.84 0.7710 0.03 —
5.63 3.13 3.75 3.75 5.00 5.63 2.50 1.88 0.5826 1.56 —
Main effect and interaction, P-value Formulation Manufacturing technique Antibiotic Formulation × manufacturing technique Formulation × antibiotic Manufacturing technique × antibiotic Formulation × manufacturing technique × antibiotic
0.0002 0.6697 0.1758 0.0952 0.9455 0.6849 0.9901
0.7432 0.5204 0.9720 0.1827 0.2267 0.7343 0.8790
0.2772 0.1664 0.7261 0.5391 0.5536 0.9315 0.5121
0.0962 0.5743 0.7786 0.7786 0.2636 0.5743 0.4005
Item
a–d
Means within a column without a common superscript differ significantly (P ≤ 0.05). RB-TS-Anti = research-based diet + thick die run slowly with antibiotic; RB-TF-Anti = research-based diet + thin die run fast with antibiotic; LC-TS-Anti = least-cost diet + thick die run slowly with antibiotic; LC-TF-Anti = least-cost diet + thin die run fast with antibiotic; RB-TS-No = research-based diet + thick die run slowly with no antibiotic; RB-TF-No = research-based diet + thin die run fast with no antibiotic; LC-TS-No = least-cost diet + thick die run slowly with no antibiotic; LC-TF-No = least-cost diet + thin die run fast with no antibiotic. 1
microscopically using a light microscope set to 10× magnification. Villus height was measured from the tip of the villi to the crypt area and villus width was measure at half height. Measurements were based on at least 10 well-oriented villi per broiler. Villus surface area was calculated as a cylinder based on height and width at half height. Statistical Analysis Two separate statistical analyses were performed. A diet formulation × manufacturing technique × antibiotic inclusion factorial analysis was performed to explore the main effects and all possible interactions for broiler performance and intestinal histology. Additionally, multiple comparisons were performed. Significant differences were further explored using Fisher’s LSD test. Boneless, skinless breast yield, fat pad yield, and gizzard yield data were tested for normality. All statistics were calculated using the GLM procedure of the Statistical Analysis System [22]. Alpha was designated as 0.05.
RESULTS AND DISCUSSION Broiler Performance and Carcass Quality Table 3 contains performance data from 3 to 40 d. Only the overall growth period (3 to 40 d) is discussed unless more specific growth periods are needed to support overall observations. Table 4 describes the carcass characteristics of broilers processed on d 40. To negate the effects of varying live weight gain, the breast weight, fat pad weight, and gizzard weight were recorded as percentages of carcass weight. Antibiotic inclusion had no effect on broiler performance or carcass quality (P > 0.05; Table 3 and 4). Antibiotics are used at subtherapeutic levels to prevent disease and are most effective under conditions of stress (i.e., the presence of unfavorable microorganisms), extremes in ambient temperature, disease, crowding, and poor management [23]. To ensure a typical production challenge, broilers were reared on built-up litter obtained from a commercial poultry house. After completion of the study, analysis of the lit-
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126 Table 4. Carcass characteristics of 40-d broiler chickens Carcass, kg
Breast, % of carcass
Fat pad, % of carcass
Gizzard, % of carcass
Treatment1 RB-TS-Anti RB-TF-Anti LC-TS-Anti LC-TF-Anti RB-TS-No RB-TF-No LC-TS-No LC-TF-No P-value SEM Fisher’s LSD
2.04bc 2.11a 2.05bc 2.01c 2.06ab 2.07ab 2.02bc 2.00c 0.0015 0.02 0.05
32.07ab 32.52a 31.28bc 30.78c 31.12bc 32.14ab 31.41abc 30.67c 0.0095 0.41 1.13
1.47c 1.31c 1.95ab 1.85ab 1.62bc 1.39c 2.06a 2.06a 0.0001 0.12 0.34
1.88 1.92 1.91 2.09 2.01 1.96 2.02 2.14 0.0883 0.07 —
Main effect and interaction, P-value Formulation Manufacturing technique Antibiotic Formulation × manufacturing technique Formulation × antibiotic Manufacturing technique × antibiotic Formulation × manufacturing technique × antibiotic
0.0002 0.9951 0.3404 0.0132 0.7010 0.4424 0.1969
0.0015 0.8417 0.2506 0.0194 0.2421 0.7639 0.4812
0.0001 0.1666 0.1085 0.4128 0.7630 0.9351 0.6262
0.0375 0.1459 0.0911 0.1126 0.9230 0.4212 0.8379
Item
a–c
Means within a column without a common superscript differ significantly (P ≤ 0.05). RB-TS-Anti = research-based diet + thick die run slowly with antibiotic; RB-TF-Anti = research-based diet + thin die run fast with antibiotic; LC-TS-Anti = least-cost diet + thick die run slowly with antibiotic; LC-TF-Anti = least-cost diet + thin die run fast with antibiotic; RB-TS-No = research-based diet + thick die run slowly with no antibiotic; RB-TF-No = research-based diet + thin die run fast with no antibiotic; LC-TS-No = least-cost diet + thick die run slowly with no antibiotic; LC-TF-No = least-cost diet + thin die run fast with no antibiotic. 1
ter bed confirmed the presence of the unfavorable microorganisms E. coli (2.5 million/g of dry litter) and C. perfringens (10,500/g of dry litter). However, extreme changes in ambient temperatures, crowding, and poor management did not occur. Therefore, it is likely that the broilers were not exposed to a challenge sufficient to induce a response associated with antibiotic inclusion. Live weight gain and feed conversion trends did not follow changes in pellet quality. Broilers fed the treatments with the highest pellet quality [RB-TS-Anti and RB-TS-No; MPDI = 89.47, fines = 16.26%] did not exhibit improved live weight gain or feed conversion (P > 0.05) compared with broilers fed the treatments with the lowest pellet quality [LC-TF-Anti and LC-TFNo; MPDI = 69.86, fines = 33.64%]. Despite attempts to produce experimental treatments that would mimic current industry pellet quality, the pellets fed in this study could still be considered high quality. The MPDI values ranged from 69.86 to 89.47% and percentage of fines ranged
from 33.64 to 16.26% (Table 2). Greenwood et al. [13] found that broilers fed diets containing 20 and 30% fines did not differ in BW gain or feed conversion. Additionally, Moritz et al. [6] found a 5-point improvement in feed conversion with a 25 percentage point increase in the PDI. However, the PDI values used by Moritz et al. [6] ranged from 61.72 to 87.29, a greater range than the one used in this study. Cutlip et al. [7] found a 20-point improvement in feed conversion when the PDI improved from 89.68 to 93.84, above the PDI range for the current study. It is plausible that the pellet quality used in the study fell into a neutral zone for broiler performance. Despite broiler performance not being directly affected by pellet quality, formulation main effects were observed. Feeding the RB diet formulation resulted in higher broiler live weight gain (P = 0.0002) and lower fat pad (P = 0.0001) and gizzard yields (P = 0.0375) compared with feeding the LC diet formulation. The RB and LC diets were formulated to have the same digest-
Buchanan et al.: PELLET QUALITY AND PERFORMANCE ible amino acid content for methionine, lysine, threonine, and TSAA (Table 1). Additionally, all diet formulations met or exceeded total amino acid recommendations established by CobbVantress [17]. However, the RB diet had higher total amino acid contents for valine, arginine, and tryptophan (Table 1) and an overall increase in CP of 3.87 percentage points. The most efficient utilization of amino acids occurs when broilers are fed concentrations at or below, not above, their requirement [24]. However, positive performance has been correlated with the feeding of excess amino acids. Corzo et al. [24] reported increased BW, decreased fat accretion, and higher breast fillet and tender yields when broilers were fed diets with excess concentrations of essential amino acids. Additionally, Bartov and Plavnik [25] reported increased breast meat yield when broilers were fed diets with moderate excesses in CP. A formulation × manufacturing technique interaction was observed for carcass weight (P = 0.01) and breast yield (P = 0.02). Carcass weight and breast yield were not different for broilers fed either diet formulation manufactured using TS (P > 0.05). However, when the same diets were manufactured using TF, the RB resulted in a marked increase in carcass weight and breast yield compared with the LC. By design, use of TS would result in a longer retention time in the die; thus, feed would have greater exposure to heat. The combination of heat and moisture found in the pelleting process could lead to Maillard reaction products that reduce the availability of essential amino acids, most notably lysine [26]. Perhaps the use of TS resulted in some denaturation of proteins during processing that created decreased amino acid digestibility. Therefore, birds fed the RB-TF treatment, formulated with higher concentrations of amino acids and manufactured with less exposure to heat, had the most potential to utilize amino acids for muscle accretion. Feed intake and mortality were not affected by experimental treatments (P > 0.05). Intestinal Morphology Table 5 contains intestinal morphology data obtained from 21-d broilers, whereas Table 6 contains intestinal morphology data obtained from 40-d broilers. A significant diet formulation × manufacturing technique × antibiotic
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inclusion interaction was observed for 21-d villus height and surface area (P = 0.0213; P = 0.0001, respectively). Inclusion of antibiotic in the starter diets resulted in lower villus heights for all treatments, with the exception of LC-TF. The most dramatic change in 21-d villus height was for the antibiotic in the RB-TS treatment. Inclusion of antibiotic in the RB-TS treatment reduced villus height by 23.6% compared with RB-TS with no antibiotic. Although antibiotic inclusion did not affect broiler performance for the duration of the experiment, a significant antibiotic effect was observed for the 3- to 21-d period. Antibiotic inclusion improved live weight gain (P = 0.002; data not presented), with broilers fed the RB-TS-Anti diet having greater live weight gain than broilers fed the RB-TS-No diet (P < 0.05). Villus surface area did not differ for broilers fed the starter diets manufactured using the TF technique despite antibiotic inclusion. However, antibiotic inclusion reduced villus surface area for broilers fed RB-TS and increased villus surface area for broilers fed LC-TS. However, 21-d villus surface area did not correspond to changes in 21-d broiler live weight gain (data not presented). A significant diet formulation × manufacturing technique × antibiotic inclusion interaction was also observed for villus height in 40-d broilers (P = 0.0001). However, antibiotic inclusion had the opposite effect on villus height in this period compared with the 21-d broilers. Antibiotic inclusion in the grower diets increased villus height, with the exception of the LC-TS treatment. Antibiotic inclusion in the LC-TS treatment decreased villus height compared with the exclusion of antibiotic. Larger villus height is associated with a healthier intestinal tract [16], whereas shorter villus height is largely associated with the presence of a challenge [27]. We suggest that the change in villus height from the 21- to 40-d period associated with antibiotic inclusion did improve the health of the GIT for the duration of the experiment. However, this effect was not sufficient to elicit a growth response. A diet formulation × manufacturing technique interaction affected villus surface area for 40-d broilers (P = 0.0074). Broilers fed diets manufactured using TF had a greater villus surface area compared with broilers fed diets
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128 manufactured using TS; however, no difference in villus surface area was observed between the RB and LC formulations. In contrast, when the same diets were manufactured using TS, the surface area of the RB treatment was much lower than the surface area of the LC treatment. Perhaps the greater surface area for broilers fed the diets manufactured using TF aided in the improvement in carcass weight and breast yield observed for broilers fed the RB-TF treatments. At this time, the authors cannot speculate on the mechanism responsible for these findings. Economic Analysis The monetary investment needed to make high-quality pellets is well established. After capital investment, the majority of cost is associated with 1) ingredients, 2) labor, and 3) energy use [28]. Although tap water is very inexpensive, adding supplemental protein in any form is a costly investment [29]. Moreover, using a thick die and slowing the production rate increases energy use, thus increasing the cost of production.
Therefore, a basic economic analysis was conducted to correlate the cost of production with the profit from the final product. With current prices [29], the ingredients needed to formulate the LC would cost $370.64/metric ton ($336.17/ ton). The ingredients used to compose the RB formulations would cost $377.42/metric ton ($342.32/ton). The local rate for high-use electricity is $0.02327/kW·h [30]. With these price estimations and feed consumption amounts per treatment, the total cost of the 4 pelleted diets was calculated (Table 7). Additionally, the total amount of boneless, skinless chicken breast yield was calculated (Table 7). Taking into consideration the total cost of manufacturing a diet and dividing that value by the total product produced, we calculated the production cost ($/unit of product; Table 7) [31]. The total cost of the LC-TF treatment ($530.08) in this study was less than the total cost of all other treatments. The cost of ingredients and electricity for this treatment was the lowest, and these broilers consumed a low volume of feed relative to broilers fed the other
Table 5. Intestinal morphology of 21-d broiler chickens Item Treatment1 RB-TS-Anti RB-TF-Anti LC-TS-Anti LC-TF-Anti RB-TS-No RB-TF-No LC-TS-No LC-TF-No P-value SEM Fisher’s LSD Main effect and interaction, P-value Formulation Manufacturing technique Antibiotic Formulation × manufacturing technique Formulation × antibiotic Manufacturing technique × antibiotic Formulation × manufacturing technique × antibiotic a–e
Villus height, μm
Villus surface area, mm2
518.5e 584.4cd 565.6d 564.7d 678.9a 630.2b 613.9bc 575.3d 0.0001 11.8 32.8
264.9c 369.4b 359.8b 371.2b 425.6a 371.7b 281.3c 374.2b 0.0001 15.5 43.0
0.0057 0.5035 0.0001 0.0903 0.0001 0.0001 0.0213
0.3035 0.0004 0.0466 0.2213 0.0001 0.0796 0.0001
Means within a column without a common superscript differ significantly (P ≤ 0.05). RB-TS-Anti = research-based diet + thick die run slowly with antibiotic; RB-TF-Anti = research-based diet + thin die run fast with antibiotic; LC-TS-Anti = least-cost diet + thick die run slowly with antibiotic; LC-TF-Anti = least-cost diet + thin die run fast with antibiotic; RB-TS-No = research-based diet + thick die run slowly with no antibiotic; RB-TF-No = research-based diet + thin die run fast with no antibiotic; LC-TS-No = least-cost diet + thick die run slowly with no antibiotic; LC-TF-No = least-cost diet + thin die run fast with no antibiotic. 1
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Table 6. Intestinal morphology of 40-d broiler chickens
Item Treatment1 RB-TS-Anti RB-TF-Anti LC-TS-Anti LC-TF-Anti RB-TS-No RB-TF-No LC-TS-No LC-TF-No P-value SEM Fisher’s LSD Main effect and interaction, P-value Formulation Manufacturing technique Antibiotic Formulation × manufacturing technique Formulation × antibiotic Manufacturing technique × antibiotic Formulation × manufacturing technique × antibiotic
Villus height, μm
Villus surface area, mm2
724.6c 854.9a 727.5c 865.3a 640.8d 782.3b 848.2a 772.4bc 0.0001 19.0 52.9
365.6de 495.3ab 407.1cd 470.4abc 330.7e 518.5a 432.8bc 509.9a 0.0001 23.2 64.6
0.0001 0.0001 0.0173 0.0001 0.0007 0.0002 0.0001
0.0952 0.0001 0.4162 0.0074 0.2424 0.2744 0.5013
a–e
Means within a column without a common superscript differ significantly (P ≤ 0.05). RB-TS-Anti = research-based diet + thick die run slowly with antibiotic; RB-TF-Anti = research-based diet + thin die run fast with antibiotic; LC-TS-Anti = least-cost diet + thick die run slowly with antibiotic; LC-TF-Anti = least-cost diet + thin die run fast with antibiotic; RB-TS-No = research-based diet + thick die run slowly with no antibiotic; RB-TF-No = research-based diet + thin die run fast with no antibiotic; LC-TS-No = least-cost diet + thick die run slowly with no antibiotic; LC-TF-No = least-cost diet + thin die run fast with no antibiotic. 1
treatments. However, these broilers also produced a low yield of boneless, skinless breast tissue. In contrast, the broilers fed the RB-TF treatment produced a high yield of boneless, skinless breast tissue (Table 4). Even though the
RB-TF feed cost more ($544.48), the increase in boneless, skinless breast yield corresponded to a savings in production costs of $0.14/kg compared with broilers fed the LC-TF treatments (Table 7). Therefore, it is evident that the
Table 7. Basic economic analysis of boneless, skinless breast production using different diet formulation and feed manufacturing techniques1 Treatment2 RB-TS RB-TF LC-TS LC-TF 1
Total cost of feed, $
Boneless, skinless breast produced, kg
Production cost,3 $/kg
Savings,4 $/kg
538.88 544.48 546.56 530.08
175.84 185.29 177.60 172.16
3.06 2.94 3.08 3.08
+0.02 +0.14 +0.00 —
Nonreplicated descriptive data. Cost of feed ingredients for the research-based diet was $377.42/metric ton. Cost of feed ingredients for the least-cost diet was $370.64/metric ton. 2 RB-TS = research-based diet manufactured using a thick die run slowly; RB-TF = research-based diet manufactured using a thin die run fast; LC-TS = least-cost diet manufactured using a thick die run slowly; LC-TF = least-cost diet manufactured using a thin die run slowly. 3 Production cost = total cost of feed/total product produced. 4 Production cost compared with the production cost of LC-TF. The LC-TF was chosen because it is the combination of diet formulation and manufacturing technique that is often used in the commercial feed industry.
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130 increased ingredient cost of an RB formulation could be justified by the greater return in boneless, skinless chicken breast yield. This research emphasizes the impact of the diet formulation and manufacturing technique on pellet quality and subsequent broiler performance and yield. The authors appreciate that additional factors affect pellet quality. However, because of the improved carcass weight and breast yield, commercial integrated feed mills may be able to justify the increased cost associated with the use of diet formulations with higher protein and moisture.
CONCLUSIONS AND APPLICATIONS
1. The RB formulations improved broiler growth and decreased fat pad yield compared with the LC formulations. 2. Carcass quality was influenced by the interactions that occurred between diet formulation and manufacturing technique. 3. Antibiotic inclusion in high-quality broiler diets had no effect on broiler performance but did affect villus height, an indicator of good intestinal health. 4. Using a RB formulation manufactured using a thin die and a fast production rate resulted in a $0.14/kg savings compared with using an LC formulation manufactured in the same manner.
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30. Allegheny Energy, Greensburg, PA. 31. Methods for calculating production cost and savings: 1) production cost = (cost of feed × feed intake) + energy use during manufacture/boneless, skinless breast weight; 2) savings = production cost of LC-TF − production cost of treatment.