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Journal of Animal Science - Animal Physiology

The effect of the inclusion of recycled poultry bedding and the physical form of diet on the performance, ruminal fermentation, and plasma metabolites of fattening lambs1

 

This article in JAS

  1. Vol. 93 No. 8, p. 3843-3853
     
    Received: Dec 06, 2014
    Accepted: May 16, 2015
    Published: July 2, 2015


    2 Corresponding author(s): rozbeh_y@modares.ac.ir
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doi:10.2527/jas.2014-8789
  1. D. Mirmohammadi*,
  2. Y. Rouzbehan 2* and
  3. H. Fazaeli
  1. * Department of Animal Science, Faculty of Agriculture, Tarbiat Modares University, P.O. Box 14115-336, Tehran, Iran
     Animal Science Research Institute, P.O. Box 1483, Karaj 315, Iran

Abstract

During a 125-d experimental period, 24 Afshari × Kurdish male lambs initially weighing 25.2 ± 1.2 kg were grouped by BW and randomly assigned to treatments under a completely randomized design with a 2 × 2 factorial arrangement of treatments to evaluate the effects of feeding recycled poultry bedding (RPB; 0 and 200 g/kg DM) and the physical form of the diet (mash and block) on nutrient intake and digestibility, ruminal and plasma parameters, microbial N supply, N balance, feeding behavior, and growth performance of the lambs. Two diets with and without RPB in both mash and block form were prepared. Neither the inclusion of RPB nor the physical form of the diet affected the concentration of VFA or the total tract apparent digestibility of nutrients. Dietary RPB inclusion increased DMI (P < 0.01), tended (P = 0.10) to reduce ADG, and decreased G:F (P = 0.05). The physical form of the diet had no effect on DMI but decreased ADG (P = 0.01) and G:F (P = 0.02) in lambs fed on the block diet compared with those fed on the mash diet. Neither the inclusion of RPB nor the physical form of the diets had any effect on microbial N supply (g/d) and N retention. Rate of eating (P = 0.07), time spent eating (P = 0.87) and ruminating (P = 0.28), and total chewing activity (P = 0.65) were not affected by dietary RPB inclusion. Rate of eating decreased (P < 0.01) and time spent eating and total chewing activity increased (P = 0.01 and P = 0.02, respectively) in lambs fed on the block diet compared with those fed on the mash diet. Results of the current study showed that inclusion of RPB up to 200 g/kg DM in diets for fattening was possible without any effect on performance and animal health. Processing of feed into the mash form gave higher livestock productivity in comparison to the block form.



INTRODUCTION

Hot, dry weather and low precipitation in arid and semiarid regions has led to a shortage in the supply of common livestock feedstuffs (Abarghuei et al., 2010). The use of agricultural byproducts such as recycled poultry bedding (RPB) is often used as a strategy to overcome this problem (Azizi-Shotorkhoft et al., 2012). In the United States, China, and Brazil (leading countries in the poultry industry), production of dry RPB is more than 16.3, 14.6, and 12.1 million t/yr, respectively (Bolan et al., 2010). Feeding RPB to sheep has great economic potential, due to its low cost and high level of protein (183–238 g/kg DM), when used as a replacement for soybean meal in sheep diets (Obeidat et al., 2011, 2012).

When diets are processed and incorporated into a complete diet in block, mash, or pellet form, they can be successfully used to optimize growth and milk production from ruminant animals (Reddy et al., 2003). The advantage of processing feed into block form is to reduce transportation cost, storage space, and losses during storage (Samanta et al., 2003). These researchers also reported that slower consumption of the diet in block form compared with mash form led to an improved synchronous supply of energy and nitrogen in the rumen. However, processing feed into mash form, in comparison with block form, increases livestock productivity (Anandan et al., 2012).

Therefore, the present experiment was performed to assess the effect of the inclusion of RPB (at 200 g/kg DM) and physical form (PF; mash or block) in a complete diet on the performance, ruminal parameters, and plasma metabolites of growing lambs.


MATERIALS AND METHODS

This experiment was conducted at Tarbiat Modares University (Tehran, Iran) from January until June of 2012, in accordance with the Care and Use of Agricultural Animals in Research and Teaching (Federation of Animal Science Societies, 2010).

Diet Preparation

To produce RPB from fresh litter, the fresh litter was thermally processed by indirect steam pressure (indirect steam boiler, model ABR-H; Aralsan Heat Equipment Ltd., Istanbul, Turkey) at 70°C for 30 min (Table 1). Two feed formulations were formulated with and without RPB (0 vs. 200 g/kg of dietary DM; Table 2). Diets were formulated to be equal in ME and MP content and to meet requirements for growing lambs (NRC, 2007). Then, both types of formula were prepared in mash and block forms (Nazdaneh-Khorasan Co., Neyshabur, Iran). For the preparation of the experimental diet, all the dietary ingredients were mixed in a horizontal double-shaft paddle mixer (model SSHJ4; Xinxiang Hengfu Electronic Machinery Co., Ltd., Xinxiang, China) until uniform (mash form) and this feed mixture was transferred into an automatic feed block-making machine (model AFBMM; Perfect Hydro Machines India Pvt. Ltd., Gurgaon, India) with 421.8 kg/cm2 (6,000 psi) pressure to produce the block form.


View Full Table | Close Full ViewTable 1.

Chemical composition and biological analysis of recycled poultry bedding (RPB; g/kg of DM unless otherwise noted)

 
Item RPB
DM, g/kg of fresh weight 926
Chemical composition1
    CP 251
    aNDFom 376
    ADFom 179
    ADL 64.6
    Ether extract 22.3
    Ash 156
    Cu, mg/kg of DM 51.7
    Zn, mg/kg of DM 383
    RDP,2 g/kg of CP 209
    RUP,2 g/kg of CP 41.6
    MP 143
    ME,3 MJ/kg of DM 9.21
Biological analysis,1 log10 cfu/g
    Total count 1.89
    Escherichia coli 0.0
    Salmonella 0.0
1Mean values were calculated from the analysis of 4 samples in triplicate.
2Estimated from CP content of RPB and N degradation parameters (measured in a digestion trial) according to the Agricultural and Food Research Council (1993).
3Estimated as 0.80 × digestible OM (DOM; g/g of DM) × 18.5 (MJ/kg of DOM; Deshck et al., 1998).

View Full Table | Close Full ViewTable 2.

Ingredient and chemical composition of the diets fed in the trial

 
Diet1
Item RPB0 RPB200
Total mixed ration ingredient, g/kg of DM
    Alfalfa hay 250 250
    Wheat straw 50 50
    Recycled poultry bedding 0 200
    Barley grain 187 163
    Wheat grain 113 140
    Wheat bran 220 80
    Molasses 120 80
    Meat meal 30 10
    Urea 5 2
    Sodium bicarbonate 5 5
    Salt white 5 5
    Minerals and vitamins premix2 5 5
    Bentonite 10 10
DM, g/kg, as-fed basis 876 889
Chemical composition
    OM 910 896
    CP 151 155
    aNDFom3 391 369
    ADFom4 202 192
    ADL 51.7 51.4
    Ether extract 39.8 39.5
    Ca 9.47 10.5
    P 4.89 5.33
    Mg 3.28 3.69
    K 19.1 18.8
    Na 5.71 6.01
    Zn, mg/kg DM 53.8 88.2
    Cu, mg/kg DM 8.24 11.1
    Mn, mg/kg DM 77.3 92.5
    RDP,5 g/kg of CP 98.1 109
    RUP,5 g/kg of CP 52.9 45.7
    MP5 92.4 93.5
    ME,6 MJ/kg of DM 11.5 11.8
1RPB0 = diet containing 0 g/kg DM recycled poultry bedding (RPB); RPB200 = diet containing 200 g/kg DM RPB.
2Provided per kilogram of DM: 171 g Ca, 73.4 g P, 38.8 g Mg, 14.1 g K, 5.33 g S, 2.93 g Fe, 3.44 g Zn, 22.6 mg Se, 826 mg Cu, 21.7 mg/kg Se, 44.1 mg Co, 422,000 IU vitamin A, 37,000 IU vitamin D, and 2,424 IU vitamin E.
3aNDFom.
4ADFom.
5Calculated from coefficient of degradability for individual feed ingredients according to the Agricultural and Food Research Council (1993) guidelines.
6Calculated by the following equation (AFRC, 1993); ME = 0.0157 × DOMD.

Animals Study

Twenty-four growing local Afshari × Kurdish male ram lambs (25.2 ± 1.2 kg initial BW) were randomly divided into 1 of 4 treatment groups. The treatments consisted of the following: 1) without RPB in mash form, 2) without RPB but in block form, 3) with RPB (200 g/kg DM) in mash form, and 4) with RPB (200 g/kg DM) but in block form. Before starting the experiment, animals were housed in individual pens (1.5 by 0.9 m), treated for internal parasites (triclabendazole + levamisole, 12 mL per each lamb; Darou-Pakhsh Co., Iran), and vaccinated (Enterotoxaemia Vac, 3 mL per each lamb; Razi Vaccine and Serum Research Institute, Iran) against common diseases as well as having a 20-d adjustment period to allow the lambs to acclimatize to the experimental conditions and diets before beginning the 105-d growing period. Throughout the experimental period, animals were allowed ad libitum (15% in excess of the previous day’s intake) access to feed and water. Lambs were fed twice daily at 0800 and 1600 h, respectively. Feed offered and refused was weighed and recorded every day before morning feeding. Samples of feed offered and refused were stored in the freezer at –20°C. The liveweight changes were measured at 2-wk intervals and the ADG was estimated by fitting a simple linear regression model of weight over time (Rattanaronchart et al., 1983). Gain efficiency was calculated by dividing the ADG by DMI.

To measure the digestibility of nutrients, at d 92 of the fattening period, 5 lambs from each treatment were selected on the basis of BW (51.1, 48.9, 52.0 and 51.6 kg) as representing the average BW in each experimental diet. Animals were individually placed in metabolism crates for a period of 14 d, allowing 7 d for adaptation to metabolism crates and 7 d for the collection period. Feed offered and refusals were weighed and recorded daily, and samples of these were then stored in a –20°C freezer until use. At the same time, total urine produced daily was collected in plastic vessels containing 100 mL of sulfuric acid solution (10%, vol/vol), to keep the final pH below 3 (to prevent bacterial growth and the loss of ammonia-N), placed below the urine outlet in the metabolism crates. The volume of urine collected every morning from an individual animal was measured. To prevent the precipitation (particularly of uric acid) of purine derivatives (PD) in urine during storage (Chen and Gomes, 1992), 10 mL of daily amount was sampled, diluted with 40 mL distilled water, and then stored at –20°C for the estimation of total N and PD.

Blood samples were collected via the jugular vein (in 10-mL vacutainer tubes; Vacutainer PST lithium heparin; Ava Pezeshk, Tehran, Iran) at 0800, 1100, and 1400 h on Days 24, 61, and 89. Samples were centrifuged (1,500 × g for 15 min at 25°C), and an aliquot of plasma was removed and stored at –20°C until analyzed. On Days 26, 63, and 91, ruminal fluid (approximately 100 mL) was sampled by stomach tube at 0800, 1100, and 1400 h and filtered through 4 layers of muslin cloth, and samples were collected for ammonia-N (5 mL being added to 1 mL of 0.2 N HCl) and VFA (1 mL was mixed with 0.25 mL of a solution containing 20 mM 2-ethylbutyric acid and 200 mL/L of orthophosphoric acid) analysis.

The same animals, facilities, experimental design, treatments (experimental diets), and feeding management used in the performance trial were adopted. Two observers were used to visually record the feeding behavior observations at 5 min intervals for 24 h on Days 44, 64, and 83 of the fattening period (Araujo et al., 2008). The time spent for each animal observation was not more than 5 s. Eating, ruminating, and total chewing times were determined and expressed as minutes per day. Time (expressed in minutes) expended in each activity was calculated by the number of observations recorded and multiplied by 5. Total chewing time was considered the sum of eating and ruminating times (Weidner and Grant, 1994). Eating, ruminating, and total chewing times were also expressed as minutes per gram of DM and NDF intakes.

Laboratory Analyses

The pooled samples of feed offered, refusals, and feces were dried at 55°C in a forced-air oven (model FC-610, Advantec; Toyo Seisakusho Co. Ltd., Tokyo, Japan) to achieve a constant weight. Then, the dried samples were ground to pass through 1-mm sieve and were analyzed for DM, OM, CP, and ether extract (methods 967.03, 942.05, 976.06, and 920.29, respectively; AOAC, 1990). Dietary aNDFom and ADFom concentrations were analyzed following the method described by Van Soest et al. (1991) with addition of heat stable α-amylase (A3306; Sigma) and sodium sulfite and were corrected for residual ash. The ADL was determined by solubilization of cellulose with 72% sulfuric acid, according to the method described by Robertson and Van Soest (1981). Diet and plasma samples were analyzed for determination of major and trace elements by an assay kit (Pars Azmun Diagnostics, Tehran, Iran). The concentrations of glucose, plasma urea N (PUN), triglycerides, creatinine, total protein, albumin, Zn, and Cu were measured using kits from Pars Azmun Diagnostics by a spectrophotometer (Jenway 6300; Jenway Ltd., Essex, UK).

Analysis of VFA in the ruminal fluid was performed by gas–liquid chromatography using ethyl-butyric acid as the internal standard as described by Cottyn and Boucque (1968). Ammonia-N concentration was determined using a phenol-hypochlorite assay (Broderick and Kang, 1980).

Estimation of microbial N was performed based on urinary PD excretion (Chen and Gomes, 1992). Before the analysis, all samples were thawed and pooled for each lamb in proportion to daily urine output. Briefly, allantoin and xanthine plus hypoxanthine and uric acid were respectively measured using the colorimetric, xanthine oxidase (MAK078; Sigma), and uricase (02101203; MP Biomedicals) methods. The following nonlinear equation is used to describe the relationship between absorption of PD (x; mmol/d) and excretion of PD in urine (y; mmol/d; Chen and Gomes, 1992):in which W0.75 is metabolic BW (kg) of the animal and 0.84 is the recovery of absorbed PD in urine. Based on Eq. [1], the amount of exogenous PD absorbed can then be estimated from the daily excretion of PD. The calculation of x from y based on Eq. [1] can be performed by means of the Newton–Raphson iteration process, as given below (Chen and Gomes, 1992):in whichand the derivative of f(x) is f(x) = 0.84 – 0.038 W0.75exp(–0.25x).

Finally, produced microbial N was estimated on the following equation (Chen and Gomes, 1992):in which microbial N is expressed in grams N per day; x is expressed in millimoles per day; 0.83, 70, and 0.116 are digestibility of microbial purines; N content of purines is 70 mg N/mmol; and ratio of purine N:total N in mixed rumen microbes is taken as 11.6:100, respectively.

Measuring of bulk density in each experimental diet with 10 replicates was performed based on the beginning and end of the experimental period. To measure bulk density in the mash diets, sampling from different parts of the completely mixed ration was performed. Then, the bulk density was calculated by filling and weighing a cubic box with known volume (Anandan et al., 2012). For block diets, bulk density was calculated in each block. Initial weight and volume (width × height × length) of each block was measured (Table 7). Then, bulk density was determined simply by dividing the weight by the volume for each block (Anandan et al., 2012). In blocked samples, hardness was expressed as peak force (N) needed for breaking of the samples. The hardness testing was performed using a computer-controlled servo-hydraulic Instron testing machine (model 8506; Instron Ltd., Buckinghamshire, England) with 2,500 kN capacity, as described by Thomas (1998).

Biological Analysis

The counts of total bacteria, Escherichia coli, and Salmonella were determined according to the methods of Clesceri et al. (1998). One gram of each RPB sample was added to 9 mL of buffered peptone water (Fisher Scientific, Ottawa, ON, Canada), vortexed for 60 s, and then serially diluted 10-fold in buffered peptone water, resulting in dilutions ranging from 10–1 to 10–8 for enumeration. The counts of total bacteria, E. coli, and Salmonella in the serially diluted samples were quantified using plate count agar medium, MacConkey agar medium, and xylose lysine deoxycholate agar medium (numbers 1.05463, 1.05465, and 1.05287, respectively; Merck, Darmstadt, Germany). The media were transferred to sterile plates after sterilization (autoclaved at 120°C and 1.5 atm for 15 min). Then, 20 μL of each dilution was spread onto the medium, with 3 replicates (plates) and 2 observations in each. All tubes and plates were incubated at 37°C for 24 h. The bacterial colonies were counted immediately after removal from the incubator. Bacteria were enumerated by a visual count of colonies by using the best replicate set from dilutions that resulted in 30 to 300 colonies per plate. The microbial enumerations of samples were expressed as log10 cfu per gram.

Statistical Analysis

Obtained data were analyzed using PROC MIXED of SAS (SAS Inst. Inc., Cary, NC). All data were normally distributed (Shapiro–Wilk test from the UNIVARIATE procedure of SAS; W ≥ 0.95). All data, except physical characteristics of diets, were analyzed as a 2 × 2 factorial arrangement under a completely randomized design, considering the fixed effects of factors RPB (0 and 200 g/kg DM), PF of diet (mash and block), and RPB × PF interaction. Ruminal fermentation (ammonia-N and VFA) and plasma parameters were analyzed as repeated measures assuming an ar(1) covariance structure. The effect of sampling days (discrete variable) and sampling hour (continuous variable) and their interaction were not significant (P > 0.05) for any of the variables and were, therefore, not included in the final model; data were averaged per lamb and the mean values were used in the statistical analysis. The statistical significance and tendency were declared at P ≤ 0.05 and P < 0.10, respectively. Means are presented as least squares means. Data on physical properties were statistically analyzed using the GLM procedure to assess diet effect.


RESULTS

Chemical Composition and Biological Analysis of Recycled Poultry Bedding and Diets

Chemical and biological analyses of the RPB are presented in Table 1. The thermal processing method used in the present study completely eliminated E. coli and Salmonella from the raw RPB. A separate chemical analysis for the experimental diets (Table 2) illustrated a numerical difference in some components in the diets.

Rumen Fermentation and Plasma Parameters

The effects of RPB inclusion and PF of diet on ruminal and plasma parameters are presented in Table 3. The average ruminal ammonia-N concentration was greater (P < 0.01) for lambs fed diets containing RPB but was not affected (P = 0.19) by the PF of the diet. The molar proportions of VFA and acetate to propionate ratio were not affected by the experimental diet.


View Full Table | Close Full ViewTable 3.

Effect of recycled poultry bedding (RPB) level and physical form (PF; mash vs. block) on rumen fermentation and plasma metabolites in growing lambs

 
Level of RPB in diet, g/kg DM
0.0
200
P-value
Item Mash Block Mash Block SEM RPB1 PF
Ruminal parameters
    Ammonia, mg/dL 12.1 9.92 18.5 16.6 1.56 <0.01 0.19
    VFA, mol/100 mol
        Acetate 63.3 64.7 63.8 64.3 1.28 0.95 0.46
        Propionate 22.2 20.1 20.1 19.8 1.02 0.25 0.25
        Butyrate 12.0 12.8 13.4 13.5 0.55 0.08 0.44
        Isovalerate 0.82 0.93 0.78 0.95 0.08 0.91 0.13
        Valerate 1.54 1.35 1.79 1.35 0.15 0.45 0.06
        Acetate: propionate 2.87 3.23 3.19 3.3 0.21 0.39 0.30
Plasma parameters
    Metabolites, mg/dL
        Glucose 53.5 53.6 50.1 51.2 1.66 0.10 0.71
        Plasma urea-N 15.9 15.0 19.2 17.4 1.02 0.01 0.21
        Triglycerides 34.9 26.8 33.4 24.6 4.05 0.65 0.04
        Creatinine 1.45 1.22 1.42 1.44 0.18 0.60 0.57
    Proteins, g/dL
        Total protein 6.61 6.32 6.81 5.89 0.98 0.84 0.45
        Albumin 4.06 3.91 4.24 3.88 0.71 0.91 0.73
    Minerals, µg/mL
        Zn 1.07 1.05 1.09 1.07 0.08 0.85 0.79
        Cu 0.67 0.63 0.59 0.66 0.04 0.60 0.74
1RPB = diets containing 0 vs. 200 g/kg DM RPB.

Plasma concentrations of PUN increased (P = 0.01) with the inclusion of RPB into the diet. Plasma concentrations of glucose, triglycerides, total protein, albumin, creatinine, Zn, and Cu were unaffected by the experimental diet.

Nutrient Digestibility, Intake, and Growth Performance

The effects of RPB inclusion and PF of diet on nutrient digestibility, intake, and growth performance of lambs are presented in Table 4. Because there were no interactions of RPB × PF, only the main effects are listed in the table. Total tract apparent digestibility of dietary DM, OM, CP, ether extract, NDF, and ADF were unaffected by the experimental diet. The inclusion of RPB in the diet increased intake of DM (P < 0.01), OM (P = 0.01), and CP (P < 0.01). However, nutrient intake was not affected by the PF of the diet. Average daily gain was not influenced in lambs fed RPB diet compared with those offered RPB-free diet, whereas G:F was decreased (P = 0.05) by the dietary inclusion of RPB. Lambs fed block diet had lower ADG (P = 0.01) and G:F (P = 0.02) when compared with those offered mash diet. Final BW was not affected by experimental diet.


View Full Table | Close Full ViewTable 4.

Effect of recycled poultry bedding (RPB) level and physical form (PF; mash vs. block) on intake, total tract apparent digestibility, and performance in growing lambs

 
Level of RPB in diet, g/kg DM
0.0
200
P-value
Item Mash Block Mash Block SEM RPB1 PF
Apparent digestibility, g/kg
    DM 658 679 678 671 11.2 0.61 0.50
    OM 693 705 708 699 10.2 0.68 0.89
    CP 684 679 678 658 11.6 0.24 0.28
    aNDFom2 509 522 511 512 18.5 0.81 0.71
    ADFom3 516 547 531 504 15.5 0.37 0.90
   Ether extract 634 640 646 629 15.2 0.94 0.74
Intake
    DM, g/d 1,663 1,654 1,852 1,886 59.3 <0.01 0.84
    OM, g/d 1,524 1,509 1,648 1,673 53.7 0.01 0.93
    CP, g/d 253 248 294 305 9.01 <0.01 0.74
    aNDFom, g/d 693 794 695 693 24.0 0.05 0.06
    ADFom, g/d 327 332 324 308 11.5 0.25 0.61
    Ether extract, g/d 65.0 66.1 72.7 74.2 2.35 0.08 0.74
Growth performance
    Initial BW, kg 25.3 25.6 25.5 25.6 1.08 0.86 0.90
    ADG, g/d 288 252 291 279 8.70 0.10 0.01
    G:F, g/g DM 0.17 0.15 0.15 0.14 0.052 0.054 0.020
    Final BW, kg 55.4 52.2 55.9 54.3 1.28 0.30 0.07
1RPB = diets containing 0 vs. 200 g/kg DM RPB.
2aNDFom.
3ADFom.

Microbial N and N Balance

The effects of RPB inclusion and the PF of the diet on microbial N supply and N balance are presented in Table 5. Because there were no interactions of RPB × PF (P > 0.05), only the main effects are listed in the table. Urinary allantoin, uric acid, xanthine, and hypoxanthine and the estimated microbial N were not different (P > 0.05) among the diets. Inclusion of RPB in the diet increased intake of N (P = 0.03), fecal N excretion (P = 0.03), and total N excretion (P < 0.01). However, N retention was not affected by the inclusion of RPB or the PF of the diet.


View Full Table | Close Full ViewTable 5.

Effect of recycled poultry bedding (RPB) level and physical form (PF; mash vs. block) on microbial N supply and N balance in growing lambs

 
Level of RPB in diet, g/kg DM
0.0
200
P-value
Item Mash Block Mash Block SEM RPB1 PF
Intake,2 g/d
    DM 1,654 1,736 1,957 1,809 120 0.14 0.78
    DOMI3 1,077 1,116 1,205 1,166 65.4 0.19 0.97
Urinary purine derivatives, mmol/d
    Allantoin 13.4 11.5 13.7 13.1 0.55 0.10 0.03
    Uric acid 2.99 3.17 3.26 3.20 0.11 0.20 0.60
    Xanthine + hypoxanthine 1.84 1.64 1.88 1.81 0.07 0.19 0.10
Microbial N supply
    Microbial N, g/d 15.3 13.6 15.8 15.1 0.62 0.11 0.06
N balance, g/d
    N intake4 39.5 41.1 49.1 45.4 2.91 0.03 0.71
    Fecal N excretion 12.6 13.2 15.8 15.4 1.01 0.03 0.92
    Urinary N excretion 17.7 19.4 24.1 21.0 1.93 0.06 0.75
    Total N excretion 30.2 32.5 39.8 36.4 2.10 <0.01 0.73
    N retention 9.33 8.38 9.19 8.97 1.38 0.76 0.80
1RPB = diets containing 0 vs. 200 g/kg DM RPB.
2Intake during sampling days.
3DOMI = digestible OM intake.
4Crude protein intake during sampling days/6.25.

Feeding Behavior and Physical Characteristics of Diets

The effects of RPB inclusion and PF of diet on feeding behavior data are presented in Table 6. Because there were no interactions of RPB × PF (P > 0.05) and diet × time (P > 0.05), only the main effects are listed in the table. Also, physical properties of experimental diets are listed in Table 7. The rate of eating tended to be affected (P = 0.07) by inclusion of RPB in the diet but was decreased (P < 0.01) by PF of diet. There was a tendency for an interaction between RPB and PF for rate of eating (P < 0.08). Total chewing activity was not affected by RPB inclusion (P = 0.65) but was increased (P = 0.02) by PF of diet. There was a tendency for an interaction between RPB and PF for total chewing activity (P < 0.08). Time spent for eating activity was not affected by RPB inclusion but was increased (P = 0.01) by PF of diet. Time spent for ruminating activity was unaffected by experimental diets. With respect to bulk density of experimental diets, there was an interaction (P = 0.01) between RPB and PF. Overall, processing of diet in block form led to increase of bulk density; on the other hand, inclusion of RPB in the diet decreased (P < 0.01) bulk density of experimental diets and hardness of complete feed block.


View Full Table | Close Full ViewTable 6.

Effect of recycled poultry bedding (RPB) level and physical form (PF; mash vs. block) of diets on feeding behavior of lambs

 
Level of RPB in diet, g/kg DM
0.0
200
P-value
Item Mash Block Mash Block SEM RPB1 PF
Intake,2 g/d
    DM 1,925 1,968 2,162 2,230 127 0.06 0.66
    aNDFom3 800 942 806 818 52.6 0.27 0.16
Rate of eating, g DM/min 9.00 6.66 8.83 8.40 0.41 0.07 <0.01
Chewing, min/d 559 705 604 628 35.4 0.65 0.02
Eating, min/d 217 303 253 273 20.4 0.87 0.01
Ruminating, min/d 342 402 350 355 17.6 0.28 0.08
Nonchewing, min/d 880 734 835 811 35.4 0.65 0.02
1RPB = diets containing 0 vs. 200 g/kg DM RPB.
2Average of intake recorded on 3 days of feeding behavior trial (d44, 64, and 83).
3aNDFom.

View Full Table | Close Full ViewTable 7.

Physical characteristics of experimental diets

 
Level of RPB1 in diet, g/kg DM
0.0
200
P-value2
Item Mash Block Mash Block SEM RPB PF RPB × PF
Bulk density, kg/m3 345 742 315 632 15.1 <0.01 <0.01 0.01
Hardness, N/cm2 72.1 59.1 3.17 <0.01
1RPB = recycled poultry bedding.
2RPB = diets containing 0 vs. 200 g/kg DM RPB; PF = physical form (of diets; mash vs. block).


DISCUSSION

Chemical Composition and Biological Analysis of Recycled Poultry Bedding and Diets

Using RPB in a ruminant diet has always been controversial and has stimulated a great deal of study in defense of its safety (Capucille et al., 2004; Obeidat et al., 2011). The presence of pathogenic organisms in raw RPB (Jeffrey et al., 1998; Martin et al., 1998) and heavy metals, which might cause serious hazards to animal and human health, are cause for safety concern (Rankins et al., 2002). One method used to overcome the risk of feeding RPB to ruminant animals is heat processing (Azizi-Shotorkhoft et al., 2012). In the present study, Table 1 shows that heat processing eliminated the E. coli and Salmonella spp. and decreased total bacteria count to less than 20,000 cfu/g, which is within the safety ranges reported by Caswell et al. (1975).

The high DM content (926 g/kg fresh weight) of RPB could be related to the heat processing and was similar to the amount reported by Azizi-Shotorkhoft et al. (2012). The high CP content of RPB indicates that RPB could be used as a source of protein in ruminant diets. However, the quality of protein in the RPB is lower in comparison with many other plant protein sources. The RPB used in our study had an NDF and ADF content close to the amounts reported by Azizi-Shotorkhoft et al. (2012; 353 and 185 g/kg of DM, respectively) and Obeidat et al. (2011; 334 and 215 g/kg of DM, respectively), whereas the respective values in the current study were less than the amounts reported in the study of Capucille et al. (2004; 528 and 317 g/kg of DM, respectively). It seems that the NDF content of the RPB can vary substantially due to various factors such as the type of bedding material used (e.g., straw, wood shavings, rice hulls, corn cobs, and peanut hulls) and the extent of heat damage occurring during heat processing (Capucille et al., 2004), indicating the importance of determining the chemical composition of RPB before incorporating it into diets. Due to high negative correlation reported between ash and ME content of the RPB, the ash content is one of the most important measures of the quality of RPB (R2 = –0.97; Deshck et al., 1998). In the present study, the ash content of RPB was within the acceptable range for ruminant feed (i.e., between 114 and 167 g/kg DM) as reported by Deshck et al. (1998). Consequently, this has led to high concentration of ME in RPB (Table 1).

Rumen Fermentation and Plasma Parameters

Ruminal ammonia-N concentrations were within the optimal range (i.e., 8.5 to over 30 mg/dL) reported by McDonald et al. (2011). Inclusion of RPB in the diet increased the ruminal ammonia-N concentration, which is probably due to the higher CP intake of animals fed the RPB diet. This is consistent with Muia et al. (2001), Animut et al. (2002), and Capucille et al. (2004), who noted that dietary RPB increased ruminal ammonia-N concentration.

As VFA are the end products of ruminal fermentation and represent the adequacy of energy supply for the ruminants (Van Soest, 1994), a reduction in their concentration would be nutritionally unfavorable for the animal. Neither the inclusion of RPB nor the diet’s PF influenced the individual VFA proportions (acetate, propionate, and butyrate) in the rumen. It seems, therefore, that the inclusion of RPB up to 200 g/kg DM did not cause any problem in the end products of ruminal fermentation. Similarly, Capucille et al. (2004) found that the inclusion of RPB in steer diets up to 350 g/kg of DM did not affect the concentration of individual VFA in ruminal fluid. However, Muia et al. (2001) found that the inclusion of RPB in the diet of Friesian cows at 910, 3,650, and 6,500 g RPB/cow per day increased the concentration of acetate and propionate. Such discrepancies may be due to diet type, PF of diet, animal variety, level of RPB inclusion, and sampling methods (Muia et al., 2001; Capucille et al., 2004).

Plasma metabolite concentrations represent an integrated index of the adequacy of nutrient supply in relation to nutrient utilization that is independent of physiological state and gives an immediate indication of nutritional status at that point in time (Cronjé and Pambu-Gollah, 1996). In our study, the plasma concentrations of glucose (50–80 mg/dL), PUN (8–20 mg/dL), creatinine (1.2–1.9 mg/dL), total protein (6–7.9 g/dL), albumin (2.4–3.0 g/dL), Zn (0.8–1.2 μg/mL), and Cu (0.7–1.3 μg/mL) in all lambs were within the typical ranges previously reported for sheep (Radostitis et al., 2007). The concentration of triglycerides were in the typical range reported for fat-tailed Iranian sheep (18.03–50.93 mg/dL; Mojabi, 2011), whereas the respective value was greater than the typical range (0–14 mg/dL) reported by Radostitis et al. (2007). The higher concentration of PUN in animals fed RPB diets may be related to a greater concentration of ruminal ammonia-N. Similarly, Hennessy and Nolan (1988) reported that PUN is highly correlated with ruminal ammonia-N. Plasma albumin content reflects the dietary conditions and decreases in unhealthy animals (Radostitis et al., 2007). As expected, there was no sign of deficiency or toxicity in regards to the plasma levels of Cu and Zn (Radostitis et al., 2007). According to the results obtained from plasma metabolites, the dietary RPB or the PF of the diet had no influence on the concentration of these metabolites.

Nutrient Digestibility, Intake, and Growth Performance

Apparent total-tract digestibility of nutrients was not affected by RPB inclusion or the PF of the diet, which can be explained by the ideal ruminal fermentation characteristics such as ammonia-N values (Table 3) in all experimental diets (Van Soest, 1994). The lack of effect on nutrient digestibility with the inclusion of RPB concurred with the previous research study (Animut et al., 2002). However, in opposition to the results obtained in the current study, another study feeding RPB at levels of 200 or 400 g/kg DM had decreased nutrient digestibility in Awassi sheep compared with those fed a diet free of RPB (Obeidat et al., 2011, 2012). They suggested that the decline in the digestibility in RPB diets is caused by the litter material containing wood shavings (about 25%), which are almost completely indigestible. The lack of effect of PF of diets on the nutrient digestibility was inconsistent with the results of Anandan et al. (2012), who reported that OM, ADFom digestibility were decreased in lambs fed mash diets compared with those offered blocked diets. Anandan et al. (2012) proposed that the decline in digestibility in animals that consumed mash diets was due to the higher DM intake compared with those fed blocked diets (Van Soest, 1994).

High rates of nitrogen ruminal degradation in RPB diets (as can be seen from high ruminal ammonia-N in Table 3) compared with those without RPB may be due to an increased ruminal rate of passage resulting in increased feed intake in animals on RPB diets vs. those fed diets free from RPB. Also, the increased feed intake in animals offered RPB diets may be due to the high mineral content in RPB, which accelerated the passage rate of digesta in the rumen as suggested by Muia et al. (2001). Consistent with our results, Capucille et al. (2004) reported that DM intake increased for steers fed 350 g/kg RPB compared with those fed a diet without RPB. However, a previous study with growing lambs found no effect on DM intake when including RPB at 100 and 200 g/kg DM as a replacement for soybean meal (Obeidat et al., 2011). Variations in the DM intake response to RPB feeding are probably related to factors such as the components of the control diet, the level of RPB, and the chemical composition of RPB.

Feed intake was not affected by PF of the diet. Inconsistent with our results, Anandan et al. (2012) reported that a diet in mash form led to increased intake compared with lambs fed block form. Anandan et al. (2012) assumed that the higher intake observed in mash fed animals might have been supported by a lesser retention time of the smaller feed particles of the mash diets. They also assumed that greater chewing activity in lambs fed the block diet could lead to an increase in heat production of animals and ultimately decreased intake.

Although lambs fed RPB diets had higher intake, their ADG was not affected in comparison to those offered RPB-free diets (Table 4). Based on digestible OM intake (Table 4), the absence of significant differences in ADG is because the absorbed energy from RPB diets was utilized less efficiently than that from RPB-free diets. Moreover, the higher CP intake, ruminal ammonia-N concentration, PUN concentration, and urinary N excretion and lower glucose concentrations in plasma support the less efficient use of energy in lambs fed RPB diets in comparison to those offered RPB-free diets. Consistent with our results, feeding RPB-containing diet to Awassi lambs at 200 g/kg DM (Obeidat et al., 2011) and inclusion of RPB in lamb diets up to 300 g/kg (Elemam et al., 2009) did not affect ADG

In the current study, the dietary inclusion of RPB significantly decreased G:F, which is primarily related to the greater DMI, with no effect on ADG in animals fed RPB diets in comparison to those offered RPB-free diets (Table 4). Higher CP intake in animals fed RPB diets was not synchronized with efficient use of energy, which implies that more energy is needed when RPB is added to the diet. Similarly, including RPB at 0 or 150 g/kg in diets for lambs did not affect feed efficiency (Elemam et al., 2009), whereas when RPB was fed at levels of 300 or 450 g/kg, feed efficiency decreased; the authors suggested that the lower G:F could be related to the lower energy density when RPB was included in the diet.

Lower ADG in lambs fed block diets might be related to more energy spent in eating and chewing activity (as shown in Table 6). Lower ADG in lambs fed the block form agree with the findings of Anandan et al. (2012), who reported that the processing of diet in block form reduced ADG in lambs compared with the mash form. Anandan et al. (2012) suggested that the reduction in ADG may be due to a lower intake.

Microbial N and N Balance

Although animals fed RPB diets consumed more N than those on RPB free diets, N balance was not affected due to higher total N excretion (Table 5). Caswell et al. (1978) reported that N excretion increased for sheep fed a 184 g RPB/kg diet compared with those fed a control diet; however, Caswell et al. (1978) reported no major difference between the experimental and control diets in term of N retention.

Urinary excretions of total PD, which are indicators of microbial protein arriving at the duodenum (Balcells et al., 1991), were not significantly affected by either RPB inclusion or the PF of the diet. Yield of microbial protein produced in the rumen is maximized when the ratio of available energy (fermentable OM) to protein (nitrogen) is optimized. Therefore, the absence of any difference in the microbial N between animals fed RPB diets compared with those fed diets without RPB is probably due to the lack of energy available for producing more microbial N with high ruminal ammonia-N concentration in animals fed the RPB diet.

Feeding Behavior and Physical Characteristics of Diets

The lack of effects of RPB inclusion on time spent eating and ruminating are inconsistent with those reported by Rossi et al. (1998), who investigated the effect of 2 sources of RPB in small and large particle size fractions in the diets of steers at 0.5% BW. Results from this study reported decreased eating and ruminating time with RPB inclusion. The difference in results was likely related to factors such as NDF content and level of concentrate in the diet.

The slower rate of eating and, consequently, longer eating and chewing time of lambs fed the block diet compared with the mash diet may be due to different physical characteristics of the block diets such as hardness, resistance to fracture, and bulk density (Thomas, 1998; Anandan et al., 2012). Hardness is a physical property of pelleted and blocked diets that can be considerably changed by heating and pressing during processing. This parameter describes the resistance of a material to break under static force and directly related to the distribution of particles (Thomas, 1998). Differences in the hardness of diets with and without RPB in block form may be related to less temporal disassociation between feed ingredients in each feed formula. Bulk density is one of the most important feed characteristics that could be affecting the handling, storage, and transport costs of feeds (Anandan et al., 2012). In the present study, the process of block making from low bulk density roughage resources improved feeing management (i.e., reducing the storage space and allowing full mechanization for handling and transportation).

Conclusions

Dietary inclusion of RPB up to 200 g/kg DM (mash form) reduced the cost of the ration with no negative effect on the growth performance and animal health of fattening lambs.

 

References

Footnotes


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