Abstract

Chopped switchgrass (SG) and chopped bermudagrass (BG) were evaluated as alternatives to pine shavings (PS) for broiler litter over 3 flocks. Twenty-four pens were filled with the 3 litter types. Live performance parameters included mortality, BW, BW gain, feed consumption, and feed conversion. Mortality was not different for litter type or flock. All other live variables were different (P < 0.0001) for flock. Mean foot pad scores (FPS) were only different (P < 0.0001) for flock. Litter performance variables included litter and cake moisture content (MC), pH, litter ammonia concentration, and cake nutrient values [nitrogen, phosphorus, and potassium (N–P–K)]. Litter and cake MC differed by litter type and flock (P < 0.0001). Litter MC was 1% lower for SG than BG or PS. Cake depth observations were similar for litter type. Litter pH differed by flock (P = 0.008) while cake pH differed for both litter type (P = 0.05) and flock (P < 0.0001). Beginning and ending litter ammonia concentration were different for flock (P < 0.0001). Potassium was different for both litter type (P = 0.04) and flock (P < 0.0001) while nitrogen and phosphorus differed only by flock (P < 0.0001). Chopped SG and BG performed as well as PS as a litter material over 3 grow-out cycles. Based on the results of this study, chopped grass materials appear to be a viable alternative to PS for broiler bedding.

DESCRIPTION OF PROBLEM

Pine shavings (PS) have been the preferred bedding material (litter) for broiler production for many years but have become increasingly expensive or difficult to obtain. Many alternative materials have been evaluated for litter including wood by-products, paper and waste materials, sand, and crop residues [1, 2]. Many of these materials are linked to specific regions and harvesting seasons, and like sand, may be uneconomical for many growers due to transportation and energy costs.

Using chopped grass as a litter material could have many benefits. Grasses are typically perennial plants that grow readily throughout the southeastern United States. Grasses can be grown on marginal lands and once established can produce biomass for many years. Chopped grass bedding typically has a lower bulk density when compared to wood chips (∼150 vs. ∼250 kg m−3, respectively), making it cheaper to transport on a weight basis. Grass can be purchased through local forage and cattle producers if not directly grown on the poultry farm and the current management practices and equipment necessary to grow and harvest grasses are readily available.

Nakaue [3] evaluated the use of chopped grass seed straw as an alternative to wood shavings in the Pacific Northwest. However, the grass species were not specified. The chop length was kept to less than two inches to reduce the incidence of litter caking. The preliminary study concluded that broilers reared on the chopped straw had lower mean BW but had better feed conversions than broilers reared on wood shavings. Stocking the broilers at higher densities (0.066 and 0.083 m2/broiler; 0.71 and 0.89 ft2/broiler) created higher incidence of litter caking and foot pad irritation as compared to a density of 0.102 m2/broiler (1.1 ft2/broiler) on chopped grass seed straw. He concluded that grass seed straw could be used as a litter as long as chop length was maintained at less than 2 in. [3].

Bermudagrass, Cynodon spp., is a perennial forage grass that covers millions of acres across the southern United States. It can yield biomass in the range of 11 to 16 Mg ha−1 (5 to 7 tons acre−1) with good management and ample rainfall [4]. Chopped bermudagrass (BG) hay was compared against PS for use in rearing hen turkeys [5]. Round bales weighing 362 to 454 kg (800 to 1,000 lb) were unrolled and chopped to 1.27 to 2.54 cm (0.5 to 1.0 in.) in length using a silage cutter. No differences were found in turkey live performance or litter condition.

The emerging renewable biofuels market has expended significant effort to develop high yielding energy crops like switchgrass (SG). SG, Panicum virgatum, is a high-yielding forage crop with varieties like Alamo yielding 22.4 Mg ha−1 (10 tons acre−1) in the southeastern United States [6]. Davis et al. [2] compared chopped Alamo SG to PS as broiler bedding in a small pen trial over a single flock. No differences were found in live performance or in carcass weights. However, the frequency of foot pad dermatitis was significantly decreased with SG. Hulet et al. [7] compared chopped miscanthus, chopped willow, poplar shavings, and PS as bedding for broilers. At 42 d age, all live performance variables were similar for litter types.

Availability of wood products and by-products such as wood chips, saw dust, and wood shavings will continue to decline as manufacturing processes become more efficient and byproducts are diverted to energy markets. This increased demand will likely make traditional wood-based litter materials economically unfeasible for poultry producers and alternative sustainable sources of litter material must be identified. The objective of this study was to compare chopped SG and chopped BG to PS as a broiler litter material over multiple heavy broiler flocks.

MATERIALS AND METHODS

Husbandry Procedures

A total of 1,152 Ross × Ross 708 chicks were obtained from a commercial hatchery for each of 3 flocks. Chicks were placed on October 13, January 14, and March 25 for Flock 1, Flock 2, and Flock 3, respectively. Chicks were sexed (50% male and 50% female) and randomly distributed (48 birds/pen) among 24 floor pens measuring 1.52 × 2.74 m (5 × 9 ft) at 0.087 m2/bird (0.94 ft2/bird) in a tunnel-ventilated research facility. Each pen was equipped with a tube feeder and a nipple drinker line; feed and water were available ad libitum. Air temperature was maintained at 33°C (91°F) at placement and reduced as birds aged to a final temperature of 21°C (70°F). A four-phase feeding program was used, composed of a starter (1 to 14 d), grower (15 to 28), finisher (29 to 41), and withdrawal (42 to 48); all diets were formulated to meet or exceed NRC recommendations [8]. All procedures were approved by the USDA Agricultural Research Service Animal Care and Use Committee at the Mississippi State University location.

Treatments

Three litter materials, PS, SG, and BG, were each placed at a depth of 8.9 cm (3.5 in.) in 8 replicate pens (Figure 1a–c). PS were obtained from a commercial sawmill. SG and BG bales were obtained from research plots at the Mississippi State University Bearden Dairy Research Center. Bales were chopped in a hammer-mill using a 0.64-cm (0.25-in.) screen. A litter amendment was not applied during this study.

Figure 1.

Pens filled with a) chopped switchgrass (SG), b) chopped bermudagrass (BG), and c) pine shavings (PS) at the beginning of Flock 1.

Figure 1.

Pens filled with a) chopped switchgrass (SG), b) chopped bermudagrass (BG), and c) pine shavings (PS) at the beginning of Flock 1.

Measurements

Birds and feed were weighed for each pen at 14, 28, 42, and 48 d age to determine BW BW gain (BWG), feed consumption (FC), and FCR. The incidence of mortality was recorded daily. At 49 d age, 10 birds (5 males + 5 females) were selected randomly from each pen to obtain foot pad scores (FPS). Foot pad scores were assigned to 3 classes: 0 = no visible lesions; 1 = mild lesions; 2 = severe lesions [9].

Litter and cake moisture content (MC) (wet basis), pH, and litter ammonia concentration were measured for each pen (n = 24) at the beginning (0 d) and end of each flock (48 d). Litter MC and pH were measured at 0 d from a composite litter sample collected from 5 locations in each pen (4 corners plus center). Cake MC and pH were measured at 48 d from a composite cake sample. Litter samples were oven dried at 103°C for 24 h [10]. Cake was removed by hand with a pitch fork. Observations of cake depth and volume were completed before a portion of the cake sample was frozen to measure nutrient values [nitrogen, phosphorus, and potassium (N–P–K)] [11]. Nutrient values were reported on a DM basis.

Litter ammonia concentration was measured (Figure 2) with a stainless steel dynamic flux chamber (DFC) connected to a photoacoustic field gas monitor [12]. The DFC was constructed similar to Woodbury et al. [13]. An internal stir fan [14] was used to keep the DFC sampling space uniform. A 10-min sampling period for ammonia concentration was determined from preliminary measurements. To reduce temporal variability in litter ammonia concentration due to changing temperatures throughout the day, only 4 pens of each treatment (n = 12) were measured.

Figure 2.

Litter ammonia concentration was collected with a dynamic flux chamber connected to a photoacoustic ammonia analyzer.

Figure 2.

Litter ammonia concentration was collected with a dynamic flux chamber connected to a photoacoustic ammonia analyzer.

Statistical Analyses

This study was conducted as a completely randomized design with 8 replicate pens and 3 litter type treatments. Data were analyzed with an ANOVA and means were separated using Fisher's LSD [15]. Analyses were performed with the PROC MIXED model [16]. All mortality and litter moisture content data were subjected to arcsine transformation. Statistical significance was established at P ≤ 0.05.

RESULTS AND DISCUSSION

Live performance variables including mortality, BW, BWG, FC, and FCR were compared for each litter type over 3 flocks. Mortality was not different between litter type (P = 0.60) or flock (P = 0.07). Mean mortality for PS, SG, and BG was 1.08 ± 0.03%, 0.76 ± 0.03%, and 1.25 ± 0.03%, respectively. The effect of litter type and interaction of litter type and flock was not different for BW, BWG, and FC. Litter type was different (P = 0.04) for FCR at 42 d with mean values of 1.70 ± 0.003, 1.69 ± 0.003, and 1.69 ± 0.003 for PS, SG, and BG, respectively. The effect of flock was different (P < 0.0001) for all parameters (Table 1). Flock 2 and 3 live performance was similar to Davis et al. [2]. Flock 3 had slightly lower BW and BWG and is likely attributable to warmer weather conditions at the end of the flock. This study differed from Nakaue [3] where both BW and FCR were significantly lower for chopped grass seed straw compared to wood shavings.

Table 1.

Live performance responses from placement for broilers reared on 3 litter treatments.

  Flock 13 Flock 24 Flock 35 
Age Variable1 PS2 SG BG Pooled PS SG BG Pooled PS SG BG Pooled 
  Mean Mean Mean SEM Mean Mean Mean SEM Mean Mean Mean SEM 
0 to 14 d BW (g) 435a 423b 423b 412b,c 409c 412b,c 367d 374d 370d 
 BWG (g) 396a 378b 379b 372b 396b 372b,c 325c 332c 328c 
 FC (g) 540a 522b 518b 506b,c 494c 499c 460d 467d 461d 
 FCR 1.37c,d 1.38b,c 1.36c,d 0.011 1.36c,d 1.34d 1.34d 0.011 1.41a 1.41a,b 1.4a,b 0.012 
15 to 28 d BW (g) 1,488a 1,486a,b 1,469a,b 11 1,460a,b 1,457b 1,463a,b 11 1,397c 1,403c 1,401c 12 
 BWG (g) 1,449a 1,441a 1,425a 12 1,420a 1,417a 1,423a 12 1,354b 1,361b 1,359b 12 
 FC (g) 2,203a 2,180a,b 2,155b 14 2,096c 2,077c,d 2,082c 14 2,028e 2,029e 2,036d,e 15 
 FCR 1.52a 1.51a,b 1.50a–c 0.005 1.48d 1.46d 1.46d 0.005 1.50b,c 1.49c 1.49b,c 0.005 
29 to 42d BW (g) 2870a 2,873a 2,855a 17 2,827a 2,833a 2,837a 17 2,688b 2,707b 2,709b 18 
 BWG (g) 2,831a 2,828a 2,811a 18 2,787a 2,793a 2,797a 18 2,646b 2,665b 2,667b 19 
 FC (g) 4,812a 4,820a 4,738a,b 31 4,697b 4,680b 4,677b 31 4,547c 4,562c 4,575c 31 
 FCR 1.700b,c 1.690c 1.680c,d 0.006 1.680c,d 1.670d 1.670d 0.006 1.720a 1.710a,b 1.710a,b 0.006 
43 to 48d BW (g) 3,394a 3,397a 3,374a 27 3,352a 3,352a 3,367a 27 3,158b 3,177b 3,192b 28 
 BWG (g) 3,354a 3,352a 3,329a 27 3,312a 3,312a 3,327a 27 3,115b 3,134b 3,150b 29 
 FC (g) 6,086a 6,080a 6,025a,b 45 5,947b 5,910b 5,936b 45 5,676c 5,717c 5,745c 48 
 FCR 1.8a–d 1.81a–c 1.8b–d 0.008 1.79c,d 1.79c,d 1.78d 0.008 1.82a 1.82a,b 1.82a 0.009 
49d FPS 0.58a,b 0.59a 0.42b,c 0.06 0.58a,b 0.38c 0.39c 0.06 0.75a 0.63a,b 0.78a 0.06 
  Flock 13 Flock 24 Flock 35 
Age Variable1 PS2 SG BG Pooled PS SG BG Pooled PS SG BG Pooled 
  Mean Mean Mean SEM Mean Mean Mean SEM Mean Mean Mean SEM 
0 to 14 d BW (g) 435a 423b 423b 412b,c 409c 412b,c 367d 374d 370d 
 BWG (g) 396a 378b 379b 372b 396b 372b,c 325c 332c 328c 
 FC (g) 540a 522b 518b 506b,c 494c 499c 460d 467d 461d 
 FCR 1.37c,d 1.38b,c 1.36c,d 0.011 1.36c,d 1.34d 1.34d 0.011 1.41a 1.41a,b 1.4a,b 0.012 
15 to 28 d BW (g) 1,488a 1,486a,b 1,469a,b 11 1,460a,b 1,457b 1,463a,b 11 1,397c 1,403c 1,401c 12 
 BWG (g) 1,449a 1,441a 1,425a 12 1,420a 1,417a 1,423a 12 1,354b 1,361b 1,359b 12 
 FC (g) 2,203a 2,180a,b 2,155b 14 2,096c 2,077c,d 2,082c 14 2,028e 2,029e 2,036d,e 15 
 FCR 1.52a 1.51a,b 1.50a–c 0.005 1.48d 1.46d 1.46d 0.005 1.50b,c 1.49c 1.49b,c 0.005 
29 to 42d BW (g) 2870a 2,873a 2,855a 17 2,827a 2,833a 2,837a 17 2,688b 2,707b 2,709b 18 
 BWG (g) 2,831a 2,828a 2,811a 18 2,787a 2,793a 2,797a 18 2,646b 2,665b 2,667b 19 
 FC (g) 4,812a 4,820a 4,738a,b 31 4,697b 4,680b 4,677b 31 4,547c 4,562c 4,575c 31 
 FCR 1.700b,c 1.690c 1.680c,d 0.006 1.680c,d 1.670d 1.670d 0.006 1.720a 1.710a,b 1.710a,b 0.006 
43 to 48d BW (g) 3,394a 3,397a 3,374a 27 3,352a 3,352a 3,367a 27 3,158b 3,177b 3,192b 28 
 BWG (g) 3,354a 3,352a 3,329a 27 3,312a 3,312a 3,327a 27 3,115b 3,134b 3,150b 29 
 FC (g) 6,086a 6,080a 6,025a,b 45 5,947b 5,910b 5,936b 45 5,676c 5,717c 5,745c 48 
 FCR 1.8a–d 1.81a–c 1.8b–d 0.008 1.79c,d 1.79c,d 1.78d 0.008 1.82a 1.82a,b 1.82a 0.009 
49d FPS 0.58a,b 0.59a 0.42b,c 0.06 0.58a,b 0.38c 0.39c 0.06 0.75a 0.63a,b 0.78a 0.06 

a–eMeans with different superscripts within a row differ significantly (P < 0.05).

1Performance variables include: mean BW, BW gain (BWG), feed consumption (FC), FCR, and foot pad scores (FPS).

2Pine shavings (PS), switchgrass (SG), and bermuda grass (BG) used as a litter material.

3Values represent the mean of 8 replicate pens placed on October 13 (Fall Flock).

4Values represent the mean of 8 replicate pens placed on January 14 (Winter Flock).

5Values represent the mean of 8 replicate pens placed on March 25 (Spring Flock).

Mean FPS (Table 1) were not different (P = 0.07) between litter types but there were flock differences (P < 0.0001). Mean FPS were lowest for both SG (0.38 ± 0.06) and BG (0.39 ± 0.06) in Flock 2. Although the litter types were statistically similar, Figure 3 illustrates the frequency of bird feet having FPS of 0, 1, or 2. Foot pad downgrade frequency (FPS = 1 and 2) was less for grass litter (44.5%, 38.0%, and 33.7% for PS, SG, and BG, respectively). This trend differed from conclusions presented by Nakaue [3]. Their study showed that higher stocking densities created more litter caking and increased foot pad irritation on chopped grass seed straw when compared to wood shavings (no foot pad data provided). However, Nakaue [3] did not increase the bird densities proportionally on the wood shavings to that of the chopped grass. This study paralleled FPS results reported in [2]; and Smith [5] found no differences in turkey FPS when comparing chopped BG hay to PS litter.

Figure 3.

Frequency of foot pad lesion scores for each litter treatment (PS = pine shavings, SG = chopped switchgrass, BG = chopped bermudagrass). Foot pad scores were: 0 = no visible lesions; 1 = mild lesions; 2 = severe lesions.

Figure 3.

Frequency of foot pad lesion scores for each litter treatment (PS = pine shavings, SG = chopped switchgrass, BG = chopped bermudagrass). Foot pad scores were: 0 = no visible lesions; 1 = mild lesions; 2 = severe lesions.

Litter performance variables including litter and cake MC, pH, litter ammonia concentration, and cake nutrient values (i.e., N–P–K), were compared for each litter type (Table 2). Litter MC was different for both litter type (P = 0.0008) and flock (P < 0.0001). The mean MC was 1% lower for SG as compared to PS and BG. The initial MC of the litter types were extremely dry (6 to 7.5%) for Flock 1 and doubled to 10 to 13% by Flock 3. Cake MC was different for both litter type (P = 0.0004) and flock (P < 0.0001). Cake MC was highest (32 to 41%) for Flock 1 and lowest (22 to 26%) for Flock 3. Although these cake MC are lower than typical, the trends correspond to less ventilation during the fall flock and more ventilation during the spring flock. Visual appraisal of cake depth concluded that litter types were similar. Physical effort to remove cake was similar between the grass and PS litter types because the chop length was 1 in. or less for both grasses. Litter pH (0 d) was not recorded for Flock 1 due to failed testing (Table 2). Litter pH was not different (P = 0.52) for litter type but was significant (P = 0.008) for Flocks 2 and 3. Flock 3 had higher pH levels than Flock 2 that would correspond to increasing levels of fecal matter. Cake pH (48 d) was different for both litter type (P = 0.05) and flock (P < 0.0001). Cake pH was highest for Flock 1 and lowest for Flock 2.

Table 2.

Litter and cake parameters from placement of broilers reared on 3 litter treatments.

  Flock 13 Flock 24 Flock 35 
Variable1 Day PS2 SG BG Pooled PS SG BG Pooled PS SG BG Pooled 
  Mean Mean Mean SEM Mean Mean Mean SEM Mean Mean Mean SEM 
Litter moisture (%) 9.8b,c 8.7c 10.1b 0.01 7.4d 6.0e 6.3e 0.01 10.8b 10.3b 12.5a 0.01 
Cake moisture (%) 48 32.6b 37.3a 40.9a 0.03 22.6d 22.9d 25.8c,d 0.03 24.1d 25.6c,d 28.4b,c 0.03 
Litter pH     7.21b 7.44a,b 7.48a,b 0.18 7.72a,b 7.82a 7.86a 0.18 
 48 8.94b 9.06a 9.07a 0.04 8.49d 8.53d 8.54d 0.04 8.59c,d 8.58c,d 8.66c 0.04 
Ammonia (%) 0b 0b 0b 5b 3b 6b 27a 28a 30a 
 48 124b 125b 127b 14 182a 177a 189a 14 96b,c 81c 100b,c 14 
Total nitrogen6 (g/kg) 48 16.0c 16.2c 17.7c 1.5 37.8a,b 37.6a,b 38.1a 1.5 35.9a,b 34.4a,b 33.8b 1.5 
Phosphorus (g/kg) 48 13.4b 14.5b 14.9b 2.0 32.7a 31.4a 32.8a 2.0 30.2a 30.9a 28.3a 2.0 
Potassium (g/kg) 48 14.6c 15.9c 18.3c 1.7 31.2a,b 31.9a,b 35.8a 1.7 28.7b 28.7b 30.5b 1.7 
  Flock 13 Flock 24 Flock 35 
Variable1 Day PS2 SG BG Pooled PS SG BG Pooled PS SG BG Pooled 
  Mean Mean Mean SEM Mean Mean Mean SEM Mean Mean Mean SEM 
Litter moisture (%) 9.8b,c 8.7c 10.1b 0.01 7.4d 6.0e 6.3e 0.01 10.8b 10.3b 12.5a 0.01 
Cake moisture (%) 48 32.6b 37.3a 40.9a 0.03 22.6d 22.9d 25.8c,d 0.03 24.1d 25.6c,d 28.4b,c 0.03 
Litter pH     7.21b 7.44a,b 7.48a,b 0.18 7.72a,b 7.82a 7.86a 0.18 
 48 8.94b 9.06a 9.07a 0.04 8.49d 8.53d 8.54d 0.04 8.59c,d 8.58c,d 8.66c 0.04 
Ammonia (%) 0b 0b 0b 5b 3b 6b 27a 28a 30a 
 48 124b 125b 127b 14 182a 177a 189a 14 96b,c 81c 100b,c 14 
Total nitrogen6 (g/kg) 48 16.0c 16.2c 17.7c 1.5 37.8a,b 37.6a,b 38.1a 1.5 35.9a,b 34.4a,b 33.8b 1.5 
Phosphorus (g/kg) 48 13.4b 14.5b 14.9b 2.0 32.7a 31.4a 32.8a 2.0 30.2a 30.9a 28.3a 2.0 
Potassium (g/kg) 48 14.6c 15.9c 18.3c 1.7 31.2a,b 31.9a,b 35.8a 1.7 28.7b 28.7b 30.5b 1.7 

a–eMeans with different superscripts within a row differ significantly (P < 0.05).

1Performance variables include: mean BW, BW gain (BWG), feed consumption (FC), and FCR.

2Pine shavings (PS), switchgrass (SG), and bermuda grass (BG) used as a litter material.

3Values represent the mean of 8 replicate pens placed on October 13 (Fall Flock).

4Values represent the mean of 8 replicate pens placed on January 14 (Winter Flock).

5Values represent the mean of 8 replicate pens placed on March 25 (Spring Flock).

6DM basis.

Litter ammonia concentration under the DFC was different (P < 0.0001) for flock but was not different (P = 0.87) for litter type. Ammonia concentration (parts per million) at the beginning of each flock increased from Flock 1 and 2 (0 to 6 ppm) to Flock 3 (37 to 30 ppm). Litter ammonia concentration at the end of each flock was different for flock (P < 0.0001) but not for litter type (P = 0.66). Flock 2 had the highest ending ammonia concentrations (177 to 189 ppm) while Flock 3 had the lowest (81 to 100 ppm).

Cake nutrient values were tested (Table 2). Litter nutrients (N–P–K) were lowest in Flock 1 for all litter types because the litter was unused. Total N and P (gram/kilogram) were different for flock (P < 0.0001) but not for litter type (P = 0.9). Potassium (gram/kilogram) was different for both litter type (P = 0.04) and flock (P < 0.0001). Potassium was highest for BG during Flock 2. Based on the results of this study along with positive results reported by [5, 2, 7], chopped grass materials appear to be a viable alternative to PS for broiler bedding.

CONCLUSIONS AND APPLICATIONS

  1. Chopped SG and BG performed as well as PS for broiler litter over 3 flocks.

  2. Mortality was different for neither litter type nor flock, whereas BW, BWG, FC, and FPS were different for flock only. Litter type was different for FCR at 42 d age.

  3. Litter MC, cake MC, cake pH, and cake K differed by both litter type and flock, whereas litter pH, litter ammonia concentration, and cake N and P differed only by flock.

  4. Chopped grasses must be scaled to commercial farm demonstrations to determine how close they perform to PS under the management of typical farmers.

Funding was provided through a grant from Mississippi Agricultural and Forestry Experiment Station–Strategic Research Initiative with bedding materials provided in part by the Mississippi State University, Sustainable Energy Research Center.

1
Approved for publication as Journal Article No. J-12104 of the Mississippi Agricultural and Forestry Experiment Station, Mississippi State University.
Primary Audience: Researchers, Flock Supervisors

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