Effects of substituting fish meal with poultry by-product meal in broiler diets on blood urea and uric acid concentrations and nitrogen content of litter

Abstract

This study was carried out to investigate the effects of dietary substitution of fish meal (FM) with poultry by-product meal (PBM) at 0%, 25%, 50%, 75% and 100% using 360, 1-day-old Arian broiler chicken. The birds were randomly allocated to 30 pens (at density of 0.08 m2/bird) in an open system partially controlled house. The chicks were raised under a photo regimen of 23:1h light to darkness up to 42 days. The five dietary treatments were offered to six replicates of 12 chicks each. Data on productive performance, serum concentrations of urea and uric acid and pH, moisture and nitrogen content of litter were collected at different ages. The mean weight gain, feed intake and feed conversion ratio were significantly decreased in the birds fed on diets containing more than 50% PBM compared to the control birds during days 1–21 of age (P < 0.01). Replacement of FM at different levels with PBM significantly affected either serum urea or uric acid concentrations (P < 0.05). The serum urea and uric acid concentrations was lower in the birds that received 100%-PBM containing diets. The mean nitrogen content of litter was similar among the experimental diets while the moisture content of litter tended to be lower for the birds fed on diets containing 25% PBM compared to the other birds (P < 0.10). No differences in litter pH were pointed out for dietary treatments. Treating the litter samples by Alum significantly increased their pH values (P < 0.01). The results suggest that, substitution of FM with PBM at different levels had no considerable impact on nitrogen contents of litter.

Keywords:

• blood urea
• broiler chicken
• poultry by-product meal
• uric acid

Introduction

Litter management in poultry production, as a mean to reduce ammonia emission, has been received increasing attention in modern poultry houses. It is well documented that high concentrations of ammonia in poultry houses have detrimental effects on the performance and health of the birds (Koerkamp 1994; Al Homidan et al. 2003; Ritz et al. 2004). Moreover, concerns have arisen with regard to ammonia emission from poultry litter as it may contribute to acidic precipitations. Atmospheric ammonia plays an important role in such precipitations. It has been reported that livestock wastes are the dominant source of ammonia emission in Europe, which has increased by 50% during 1950–1980 (Van der Hoek 1998).

Ammonia volatilization from poultry houses is mainly due to microbial breakdown of nitrogenous compounds of litter, predominantly uric acid, by uricase (Kimberly et al. 2008; Schefferle 2008). Different approaches have been implemented to reduce ammonia emission from poultry houses. Among the others, dietary manipulations and litter treatments are effective means to control ammonia emission at poultry houses level. Litter treatments are ammonia-reducing strategies which provide a better in-house environment for birds (Khosravinia 2006; Choi et al. 2008). Dietary manipulations have the potential to reduce the manure production and nutrients excretion by improving the overall efficiency of feed utilization in poultry. Therefore, such dietary manipulations may decrease the production of precursors necessary for gaseous as well as odorants emissions (Blair et al. 1999).

The reduction in mass of nutrient input and modification of nutrient form are two feeding strategies to reduce ammonia emission form poultry. The former, reduces the ammonia emission by lowering the dietary concentrations of nutrients which are involved in production of ammonia, such as dietary protein without having any detrimental effects on birds performance (Angel et al. 2006; Applegate et al. 2008). The latter, reduces the nutrients emissions from poultry houses by altering the chemical forms of the nutrients being excreted. Acidification of diets (Keshavarz 1991; Koerkamp 1994; Wu et al. 2007) and dietary inclusion of feed additives (such as urease inhibitors; Amon et al. 1995) are among the approaches considered to reduce the emission of nutrients by converting them to non-volatile forms.

It is also possible to reduce nitrogen excretion and therefore ammonia emission from poultry houses by including dietary protein sources with higher biological values. The current study investigates the effects of dietary replacement of fish meal (FM) with poultry by-product meal (PBM) on blood urea and uric acid and certain physico-chemical characteristics of litter in broilers chickens.

Materials and methods

Experimental diets

The PBM was manufactured using heads, legs and spent carcasses without inclusion of viscera. The precooked material was hydrolyzed under pressurized steam, de-oiled, dried and ground using a hammer mill. The material was then blended and sampled for further chemical analyses. The samples were analyzed for dry matter, crude protein, ether extract, ash, calcium and phosphorus (AOAC 1999). Metabolizable energy corrected for nitrogen (MEn) was estimated using the prediction equation from National Research Council (1994): The chemical compositions of the PBM used in the current study was reported by Khosravinia and Mohamadzadeh (2006). Experimental diets were prepared by substituting FM with PBM at 0%, 25%, 50%, 75% and 100% levels. All the experimental diets were formulated to be iso caloric-iso proteinous (Table 1). The diets offered to the birds for ad libitum consumption.

Table 1. Composition of starter and finisher diets with different levels of substituting fish meal with poultry by-products (PBP).

	PBP (%) in starter diets (1–21 days)					PBP (%) in finisher diets (22–42 days)
Ingredients (%)	0	25	50	75	100	0	25	50	75	100
Yellow maize	60.0	60.4	61.6	62.3	63.2	61.5	62.9	63.6	64.0	63.9
Soybean meal	22.0	22.4	22.4	22.6	23.0	18.4	18.8	19.4	19.5	19.6
Wheat	6.05	5.50	4.35	3.55	2.55	10.0	8.10	7.20	6.65	6.90
Wheat bran	0.00	0.00	0.00	0.00	0.00	0.85	0.90	0.60	0.95	0.80
FM	8.00	6.00	4.00	2.00	0.00	5.00	3.75	2.50	1.25	0.00
PBP meal	0.00	2.00	4.00	6.00	8.00	0.00	1.25	2.50	3.75	5.00
Fat	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00
Bone meal	1.50	1.35	1.35	1.35	1.25	1.50	0.50	1.50	1.17	1.17
CaCo3	0.60	0.55	0.45	0.35	0.30	0.80	0.80	0.80	0.77	0.60
Salt (NaCl)	0.25	0.20	0.15	0.15	0.15	0.20	0.15	0.15	0.20	0.22
V + MM^a	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50	0.50
DL-methionine	0.10	0.00	0.10	0.10	0.15	0.15	0.15	0.15	0.15	0.15
L-lysine	0.15	0.10	0.10	0.20	0.10	0.10	0.10	0.10	0.10	0.15
Vitamin C	0.10	0.10	0.10	0.10	0.10	0.00	0.00	0.00	0.00	0.00
ME (kcal/kg)	3001	3001	3001	3001	3001	3001	3001	3001	3001	3001
Crude protein	21.50	21.50	21.42	21.41	21.4	18.70	18.70	18.70	18.70	18.70
Crude fibre	3.10	3.10	3.10	3.10	3.10	3.10	3.10	3.10	3.10	3.10
Available calcium	0.91	0.90	0.91	0.93	0.93	0.90	0.94	0.97	0.90	0.87
Available phosph.	0.44	0.42	0.42	0.41	0.38	0.38	0.38	0.39	0.35	0.35
Lysine	1.20	1.20	1.20	1.20	1.20	1.05	1.03	1.01	1.00	1.00
Methionine	0.53	0.41	0.48	0.46	0.49	0.51	0.49	0.48	0.47	0.45
Met. + Cyst.	0.81	0.70	0.80	0.77	0.79	0.76	0.75	0.75	0.74	0.73

^a Vitamin + mineral mixture: supplied mg/kg diet.

Experimental flock and data collection

Three hundred and sixty day-old straight run Arian chicks were randomly allocated to 30 pens (at density of 0.09 m2/bird) furnished with wood shavings litter in an open system partially controlled house. Each of five experimental diets was offered to six pens of 12 chicks each. Data on weight gain, feed intake and feed conversion ratio were recorded at days 1–21 and 21–42 of experiment. All birds were slaughtered to evaluate the carcass related traits at day 42. At the same time, an approximately 200 g of litter samples were taken from the top layer of 50 mm depth at 10 predetermined locations in each pen. The litter sample from each pen was then thoroughly mixed and two sub samples of 50 g were taken in which litter moisture and litter pH was determined, respectively. The sub sample considered for pH measurement was further divided in two parts while one part was cautiously mixed with aluminium sulphate [alum, Al2(SO4)3·14H2O] (10 g/ kg) and the other part remained intact. The Nitrogen content of litter samples was measured at day 42 according to AOAC (1999). The pH of litter samples were determined with (10%, w/w) and without blending with alum.

Statistical analysis

Considering each pen as an experimental unit, data collected were subjected to one-way analysis of variance using Generalized Linear Model (GLM) procedure of SAS® (SAS institute 1998). The statistical model consisted of the fixed effect of experimental diets. Differences between treatments were analysed by a Duncan's multiple range test (Duncan 1955). For all statistical analysis, significance was declared at P < 0.05. The difference between alum treated and non-treated litter samples were examined using t-test. Prior to statistical analysis, percentage data were subjected to arc sine transformation.

Results

The effects of substituting FM with PBM on common economic parameters of the birds were presented in Table 2 and were discussed in detail by Khosravinia and Mohamadzadeh (2006). Briefly, weight gain, feed intake and feed conversion ratio were significantly decreased in birds fed on diets containing PBM levels higher than 50% during days 1–21 of age (P < 0.01). No significant differences were demonstrated in all productive performance indicators as well as carcass weight, carcass yield and mortality percentage during 22–42 days and 1–42 days from the birds fed on diets differing for PBM/FM inclusion level (Table 2; P > 0.05).

Table 2. Effect (mean ± SE) of substituting FM with poultry by-product on weight gain, feed intake, feed conversion ratio, carcass weight (CW), carcass yield (CY) and morality (Mor.) of broiler chickens.

	Level of substituting FM with poultry by-product (%)
	0	25	50	75	100	PBP effect
Weight gain (g)
1–21 days	462.9 ± 7.19^a	437.4 ± 6.39^b	439.1 ± 8.27^b	435.1 ± 9.65^b	427.5 ± 5.21^b	*
22–42 days	1200.3 ± 24.51	1176.3 ± 22.45	1191.1 ± 25.87	1211.6 ± 19.97	1212.6 ± 30.11	NS
1–42 days	1663.2 ± 28.51	1613.7 ± 24.01	1630.1 ± 32.88	1647.3 ± 18.47	1640.6 ± 33.41	NS
Feed intake (g)
1–21 days	944.3 ± 19.11^a	903.5 ± 7.69^a	846.3 ± 22.74^b	836.3 ± 11.97^b	829.5 ± 23.36^b	***
22–42 days	2698.0 ± 105.2	2475.7 ± 54.7	2600.3 ± 122.3	2703.3 ± 73.6	2535.7 ± 83.9	NS
1–42 days	3642.3 ± 122.3	3379.2 ± 53.0	3446.7 ± 132.9	3539.7 ± 72.6	3365.2 ± 9.4	NS
Feed conversion ratio (feed intake: weight gain)
1–21 days	2.040 ± 0.037^ab	2.065 ± 0.034^a	1.927 ± 0.054b^c	1.922 ± 0.027^c	1.940 ± 0.050^c	***
22–42 days	2.247 ± 0.109	2.104 ± 0.037	2.183 ± 0.084	2.231 ± 0.087	2.091 ± 0.072	NS
1–42 days	2.189 ± 0.089	2.094 ± 0.026	2.115 ± 0.072	2.148 ± 0.063	2.052 ± 0.064	NS
CW (g)	1254.6 ± 6.84	1202.5 ± 49.40	1201.9 ± 20.49	1229.1 ± 15.82	1217.6 ± 31.09	NS
CY (%)	73.72 ± 1.06	72.81 ± 1.93	72.62 ± 0.54	72.92 ± 0.58	72.47 ± 1.14	NS
Mor. (%)	6.94 ± 2.5	5.55 ± 1.75	8.33 ± 2.15	7.50 ± 3.56	6.94 ± 2.56	NS

Note: Means with in a row with no common superscript differ significantly (P < 0.05).

NS, non significant.

* P < 0.05; **P < 0.01; ***P < 0.001.

There were significant differences between the experimental diets with regard to serum urea and uric acid concentrations (Table 3). Full substitution of FM with PBM significantly decreased the serum urea and uric acid concentrations of birds. The birds fed on diets in which 25% of FM was replaced with PBM had the lowest litter nitrogen content among the experimental treatments (Table 4; P < 0.05). The birds fed on diets containing 100% PBM instead of FM experienced the wettest litter (19.23%, Table 4). The results showed that combining the two protein sources at the proportion of 25 PBM /75 FM significantly lowered the litter nitrogen content as well as litter moisture (Table 4; P < 0.05). The experimental diets showed no significant effect on the litter pH (Table 4; P > 0.05). Addition of 10 g/kg aluminium sulphate [alum, Al2(SO4)3·14H2O] into the litter, significantly lowered the pH value of the samples (Table 4).

Table 3. Mean values (±SE) of nitrogenous components of blood for treatments considered.

	Serum (mg/dl)
R. level^1 (%)	Urea	Uric acid
0	3.25 ± 0.22^ab	3.16 ± 0.31^ab
25	3.55 ± 0.21^a	4.15 ± 0.73^a
50	3.67 ± 0.26^a	3.68 ± 0.37^a
75	3.25 ± 0.18^ab	3.22 ± 0.27^ab
100	2.83 ± 0.17^c	2.63 ± 0.27^b
SEM	0.096	0.132
	P > F
R. level (%)	0.0464	0.0325

Note: Means within a column with no common superscript differ significantly (P < 0.05).

R. level, replacement level of FM with poultry by-products; SEM, standard error for pooled means.

Table 4. Mean values (±SE) of litter characteristics for treatments considered.

R. level (%)	Litter N (%)	Litter moisture (%)	Litter* pH(–Alum)	Litter* pH(+Alum)
0	1.77 ± 0.06^ab	17.57 ± 1.13^ab	6.07 ± 0.1^a	4.99 ± 0.1^a
25	1.70 ± 0.04^b	15.17 ± 0.64^b	6.08 ± 0.1^a	4.81 ± 0.2^a
50	1.79 ± 0.06^a	16.90 ± 1.19^ab	6.02 ± 0.2^a	5.06 ± 0.1^a
75	1.76 ± 0.06^ab	16.80 ± 0.65^ab	6.02 ± 0.1^a	4.88 ± 0.1^a
100	1.75 ± 0.04^ab	19.23 ± 1.12^a	6.23 ± 0.1^a	4.82 ± 0.2^a
SEM	0.047	0.474	0.055	0.066
	P > F
	0.8106	0.0920	0.7819	0.7227

Note: Means within a column with no common superscript differ significantly (P < 0.05); *The difference between pH+ alum and pH– alum was significant ( = –13.62, P < 0.05).

R. level: replacement level of FM with poultry by-products; SEM, standard error for pooled means.

Discussion

Based on the zootechnical parameters studied, inclusion of PBM in starter diets caused significant decrease in productive performance of the birds (Table 2). Silva et al. (2002) reported the same results when PBM was incorporated at 50% and 100% level in maize-soybean meal practical diets. The lower performance of the birds fed on PBM in the early ages may have been due to the lower digestibility of this protein source compared to FM. This can be demonstrated by the higher nitrogen excretion (in terms of litter N% in this study) and poorer metabolisability of nitrogen in birds fed with PBM containing diets as reported by Silva et al. (2002) and Kirkpinar et al. (2004).

There are evidences which suggest that dietary manipulation through incorporation of perfect combinations of different protein sources into broiler diets is a useful mean to reduce litter nitrogen content and subsequently ammonia emission from poultry houses (Ferguson et al. 1998). The results of current study showed that the source of dietary protein has a remarkable effect in blood uric acid and urea concentrations (Table 3). Such effects are expected to be reflected in the nitrogen (N) content of faeces as well as in the litter. However, litter samples did not differ in nitrogen content and no consistent trend was observed in nitrogen content of litter for increased substitution levels of FM with PBM. Nonetheless, the nitrogen content was numerically lower for the litter samples which were collected from the pens of the birds fed with diets in which FM was replaced with PBM by 25% (Table 4). As confirmed by Silva et al. (2002), this implies that inclusion of perfect combination of different protein sources in broiler diets might be a useful mean to reduce litter nitrogen content and subsequently ammonia emission from poultry houses. The mean litter moisture and pH at day 42 was not significantly affected by increasing levels of PBM inclusion in the diets. However, litter samples from the pens assigned to the birds fed on control diets (containing no PBM) tended to have higher values compared to those fed with 25% PBM-included diets (Table 4). Due to high ambient temperatures, the lower values for litter moisture were recorded in the current study. There is a well-known association between litter pH and ammonia emission from litter (Ferguson et al. 1998). Higher nitrogen content in litter provides ureolytic bacteria with a precursor which results in a higher level of NH3 and consequently a higher pH value.

Protein sources with greater biological value lead to greater nitrogen retention and subsequently in higher growth rates in birds. Moreover, it would be expected that a dietary protein source with higher biological value causes a lower urea and uric acid concentrations in blood serum compared to those with lower biological values (Bandegan et al. 2010). Therefore, urea and more decisively uric acid can be used as influential criteria to assess the bio-availability of a protein source alone or in combination with different protein sources for broilers. Indeed, our data supported such an idea. The birds fed on diets containing 100% FM showed higher weight gain compared to the other birds at days 1–21. Many studies reported that, manipulation of protein sources in poultry diets can alter the nitrogen content of litter and thereby ammonia emission (Hai & Blaha 2000; McGrath et al. 2005). Substituting dietary crude protein sources with the ones with higher biological values and inclusion of synthetic amino acids in poultry diets were the main policy in such studies (Angel et al. 2006; Richert and Sutton 2006).

Inclusion of 10 g/kg alum in litter samples significantly decreased the litter pH in all treatments (Table 4). The pH lowering effect of alum in poultry litter was confirmed by Do et al. (2005). The prominent advantage of alum-reduced pH is lowered microbial activity. Therefore, alum is an effective chemical treatment in reducing ammonia (NH3) emissions and solubility of certain nutrients in poultry litter (Smith et al. 2001).

The results of current study suggest that FM can be totally replaced by PBM in broiler diets without increasing the nitrogen content of the litter. It is possible that the narrow differences in blood uric acid and urea of the birds fed the different experimental diets were reflected as faecal nitrogen so that little differences were observed in nitrogen content of litter among the experimental treatments. It is also possible that the immediate initiation of huge ureolytic activity of litter microbes obliterated faecal nitrogen resulting in almost similar nitrogen content in the litter.