Effect of feeding heat-processed broiler litter in pellet-form diet on the performance of fattening lambs

Abstract

Thirty-six male Moghani lambs (31.4 ± 3.2 kg body weight) were used to investigate the effect of feeding heat-processed broiler litter (HBL) on the growth performance and carcass characteristics using a completely randomized design (nine animals per diet). The used HBL was produced commercially by indirect heating (based on the flow of hot steam) BL at 80°C for 20 minutes. The experimental diets were contained HBL at the levels of 0, 70, 140 or 210 g/kg dry matter (DM). Dry matter intake (DMI), average daily gain (ADG), harvest data and carcass characteristics of the animals were recorded. The final body weight (FBW), cold carcass weight, DMI, ADG, feed efficiency (FE) and cost per unit production in the lambs fed diet free of HBL (control diet) were 51.3 kg, 27.0 kg, 1700 g/day, 245 g/day, 0.144 and US$1.83, respectively. Feeding the increasing levels of HBL had no significant effect on the FBW, DMI, ADG, FE and carcass weight. Back-fat thickness was decreased [linear (L), P = 0.05] with increasing the level of HBL in the diet. From the offal parts, weight of internal fat was decreased (L, P = 0.035) as the dietary level of HBL elevated. Dietary treatment had no effect on the weights of lean, bone and fat in carcass and dissected legs. Fat weight of dissected loin was decreased (L, P = 0.05) as the dietary level of HBL increased. As the level of HBL elevated in diet, cost per unit production was decreased (L, P = 0.04). It is concluded that using HBL up to 210 g/kg DM in diet of fattening Moghani lambs was possible without any effect on feed intake, growth performance and animal health, but reduced loin fat, internal fat and cost per unit production.

Keywords:

• heat-processed broiler litter
• intake
• weight gain
• carcass
• lamb

1. Introduction

Limitation and fluctuating quantity and quality year-round supply of conventional feeds in many countries have increased the costs of livestock production. However, using agro-industrial by-products, such as broiler litter (BL), is mostly considered to overcome this problem in certain circumstances.

In Iran, production of dry BL exceeds 1.3 million tonnes/year (Azizi-Shotorkhoft et al. 2012). The BL can be used as a fertilizer for pastures, but economically its value becomes more when utilized as a feed ingredient (Jacob et al. 1997). Relatively less cost and great contents of crude protein (CP) [150 to 350 g/kg dry matter (DM); Goetsch & Aiken 2000] and some required minerals (Rankins et al. 2002) suggest the potential value of BL as a ruminant feedstuff. Moreover, the use of this by-product as ruminant feed can lead to the reduction of environmental pollution.

However, to decrease pathogenic bacteria and to improve nutrient availability and palatability, poultry bedding must be processed before feeding to animals (Rankins et al. 2002). Different processed BL has been successfully used in ruminant diets (Negesse et al. 2007; Azizi-Shotorkhoft et al. 2012, 2013). With substituting 0, 150, 300 or 450 g of deep-stacked BL per kilogram diet DM, Elemam et al. (2009) found the lambs fed 450 g/kg of deep-stacked BL in diet had greatest final body weight (FBW) and average daily gain (ADG) compared to those fed control diet. Chaudhry and Naseer (2012) replaced cotton seed cake by deep-stacked BL at the levels of 0, 130, 260 or 390 g/kg DM in diets of buffalo steers. They concluded that deep-stacked BL can be used up to 260 g/kg DM in ruminant rations. Feeding autoclaved (121°C; 15 minutes) BL to Awassi lambs at the levels of 0, 100 or 200 g/kg diet DM had no effect on FBW and dry matter intake (DMI) but improved the meat quality (Obeidat et al. 2011).

This study was performed to assess the effect of different levels of heat-processed broiler litter (HBL) in pellet-form diets on fattening performance and carcass characteristics of fat-tailed Moghani lambs.

2. Materials and methods

2.1. Experimental diets and animal study

The HBL (large scale, commercially processed at 80°C for 20 minutes), which obtained from the manufactory in Sabzevar (Khorasan, Iran), was contained a mixture of bird excreta, feather, spilled feed (about 6% of total ration offered to poultry, in the poultry farms supplying BL for the manufactory), cardboard (4%) and buttonwood shavings (34%). To remove pathogenic bacteria and to improve BL quality, the material was processed under an indirect thermal operation in a special hot tank (with a capacity of 5 tonnes) for 20 minutes. The tank was comprised of two walls between which a hot steam (80°C) was flowed. Finally, the produced HBL was ground to pass a 6-mm sieve by the factory.

Four iso-caloric and iso-nitrogenous diets containing 0, 70, 140 or 210 g of HBL/kg DM (Table 1) were formulated to meet the requirements for fattening lambs according to nutrient requirements of small ruminants (NRC 1985). The experimental diets were formulated to meet the requirements of growth rate of 250 g/day and DMI of 1400 g/day for fattening male lambs at 4–7 months of age. After mixing all of the diet ingredients, the experimental diets were prepared under heat (50–60°C) and pressure (between rollers and flat die) in the pellet-form in cylindrical shape (diameter 15 mm; length 25 mm) using pelletizing machine (Pishgam Industrial Company, Iran). The diets were offered to the animals three times a day at 8:00, 14:00 and 20:00 hours ad libitum to ensure 5% orts and fresh water was available at all the times.

Table 1. Ingredients and chemical composition of the experimental diets (g/kg DM or as stated).

	Experimental diets^a
	HBL0	HBL70	HBL140	HBL210
Ingredients
Alfalfa hay	150	140	140	120
Wheat straw	72.5	72.5	64.2	65.0
Wheat bran	157	110	75	35
Barley grain, ground, dry	260	280	285	270
Maize grain, ground, dry	70.0	75.0	75.0	100
Wheat grain, ground, dry	135	135	145	150
Sugar beet pulp, dry	100	80.0	50.0	40.0
Soybean meal	40.0	22.5	15.0	0.0
Processed broiler litter	0.0	70.0	140	210
Urea	2.9	2.5	0.30	0.0
Sodium bicarbonate	2.95	3.0	3.0	3.0
Limestone	4.9	4.5	2.5	2.0
Minerals and vitamins^b	2.5	2.5	2.5	2.5
Salt	2.5	2.5	2.5	2.5
Chemical composition
DM (g/kg fresh weight)	907	910	914	915
Crude protein	136	136	136	136
Metabolizable protein	90.5	89.6	89.4	88.7
Ash-free neutral detergent fibre	336	339	340	339
Ash-free acid detergent fibre	163	159	154	147
NFC	451	448	441	439
Starch	370	364	360	355
Ether extract	20.9	19.1	18.6	18.1
Ash	52	59	67	74
Calcium	5.40	5.55	5.20	5.30
Phosphorus	4.10	4.15	4.30	4.40
Copper (mg/kg DM)	6.75	9.50	12.4	15.1
Metabolizable energy^c (MJ/kg DM)	10.63	10.63	10.63	10.63

Chemical compositions of the diets were calculated from each feed composition.

^a Diets were: heat-processed broiler litter (HBL) included in the diets at 0 (HBL0), 70 (HBL70), 140 (HBL140) or 210 (HBL210) g/kg of dietary DM.

^b Contained (per kilogram): 99.2 mg Mn, 50.0 mg Fe, 84.7 mg Zn, 1.0 mg Cu, 1.0 mg I, 0.2 mg Se, 9000 IU vitamin A, 2000 IU vitamin D, and 18.0 IU vitamin E (Roshd Daneh Co., Iran).

^c Calculated from each feed ME content, which were analysed.

Thirty-six male fat-tailed Moghani lambs (31.4 ± 3.2 kg body weight) of 135 ± 15 days of age were randomly assigned into the four dietary groups using completely randomized design (nine animals per diet). The lambs were individually housed in concreted floor pens (1.2 × 1.1 m), with wood chips as litter, in a close shed building. According to the weather condition during the animal study (May to August), the pens were cleaned weekly. The animals were allowed an adaptation period of 14 days followed by a data collection period of 84 days (total 98 days). The initial 14 days were considered as adaptation of the lambs to the individual pens, diets and experimental conditions. In this period, the amount of dietary HBL was gradually elevated in ration offered to each animal to reach the levels considered as the experimental levels in dietary treatments. At the start of the adaptation period, all the animals were treated for external (1 ml of Azantole 10% per 7 litre of water, as spraying method; Bayer, Germany) and internal (triclabendazole + levamisole, 12 ml per lamb; Darou-Pakhsh Co., Iran) parasites and vaccinated against enterotoxaemia (3 ml per lamb; Razi Vaccine and Serum Research Institute, Iran).

During the experimental period, feed offered and corresponding ort per lamb were recorded daily. Samples of feed and ort were collected daily and bulked for subsequent analyses. The representative samples were pooled to obtain a composite per lamb within the treatment. All the animals were individually weighed at the beginning and the end of the experiment and at 21-day intervals before the 8:00 hours feeding, after 16 hours feed deprivation. For each lamb, the ADG was calculated by linear regression analysis of body weight vs. time. Efficiency of production (return on investment and cost per unit production) was obtained using following equations (Harris 1970):

Return on investment per lamb was calculated as income got from the sale of 1 kg live weight gain divided by cost of feed offered for 1 kg of live weight gain.

For individual lamb, the cost per unit production was computed as the cost of feed offered for total body weight gain (as US dollar) divided by total body weight gain (kg).

2.2. Killing and sampling procedures

At the end of the experimental period, all the lambs were weighed after 16 hours feed deprivation and harvested by exsanguinations using conventional humane procedures. After complete bleeding, the bodies were skinned and external organs (skin, head and feet) were separated and weighed. The carcasses were eviscerated and internal organs or tissues including heart, liver, kidneys, spleen, lungs, kidney-pelvic-gut fat (internal fat) and digestive tract were separated and weighed. Empty body weight was obtained by subtracting the weight of digestive content from harvest weight. The hot carcasses were weighed and chilled at +4°C for 24 hours. Dressing percentage was determined as a ratio of fasting live weight and cold carcass weight. The cold carcasses of all the lambs were weighed and halved carefully. Then, the right side carcasses were cut into six wholesale cuts namely neck, shoulder, brisket, loin, legs and fat-tail, and weighed separately (Kyanzad 2001). All the cuts, except fat-tail, were dissected into the main tissue components (lean, bone and fat) and weight of each tissue was recorded. The back-fat thickness of the left side carcasses was measured over the deepest part of the loin-eye muscle. Musculus longissimus linear dimensions were measured on the chilled carcasses (Abdullah et al. 1998). M. longissimus depth was determined as the maximum depth at right angle to the width measurement. M. longissimus width was determined as the maximum width across the surface of the M. longissimus.

2.3. Analytical methods

HBL, diets and ort samples were oven-dried at 60°C to reach a constant weight, and then ground to pass a 1-mm diameter sieve (Wiley Mill, Swedesboro, USA). DM (# 930.15), N (# 984.13), ether extract (EE) (# 920.39) and ash (# 924.05) were analysed using standard methods as described in AOAC (1990). Starch content of the HBL was analysed according to AOAC (# 996.11; 1990). The ash-free neutral detergent fibre (NDFom) and ash-free acid detergent fibre (ADFom) were determined and expressed exclusive residual ash according to Van Soest et al. (1991). Non-fibre carbohydrate (NFC) content was calculated as NFC = 1000 – (NDFom g/kg DM + CP g/kg DM + EE g/kg DM + ash g/kg DM). Calcium, Mg, Cu, Mn, Fe and Zn were measured by atomic absorption, Na and K by fame emission spectrometer (Temminghoff & Houba 2004) and P by vanadate/molybdate (yellow) method (Chapman & Pratt 1961). The content of metabolizable protein (MP) in the HBL was measured using in situ degradability technique (AFRC 1992). The metabolizable energy (ME) value of HBL was calculated using the equation described by Deshck et al. (1998). The in vitro digestible OM (as g/kg DM), which was determined using rumen fluid and pepsin in two stages (Tilley & Terry 1963), was converted to an ME content, using 18.5 MJ as the gross energy per kilogram digested OM, and the factor 0.80 commonly used to convert digestible energy to ME (Deshck et al. 1998):

2.4. Statistical analysis

The data were analysed using MIXED procedures of SAS (Version 9.1, SAS Institute, Cary, NC, USA) in a completely randomized design, where initial body weight was used as a covariate for analysing the differences in body weight gain. For carcass, loin and leg measurements, the weights of carcass, loin and leg were included as covariates, respectively. The model included only the fixed effect of dietary treatment because the experimental design was completely randomized, and lamb was the random variable. The compound symmetry was used as a covariance structure in the model. Furthermore, a polynomial contrast was used to test the linear (L) or quadratic (Q) effects of HBL on measured traits.

3. Results

The HBL contents of DM, CP, MP, EE, NDFom, ADFom, ash, NFC, starch, Ca, P, Mg, K, Na, Fe, Mn, Cu, Zn and ME were 930, 238, 145, 22.3, 353, 185, 184, 203, 19.2, 16.4, 9.4, 5.7, 7.3, 0.43 g/kg DM, 1029, 324, 52, 345 mg/kg DM and 9.3 MJ/kg DM, respectively.

3.1. Feed intake and growth performance

Increasing the level of HBL in the diet had no effect (P > 0.05) on the FBW, DMI ADG and feed efficiency (FE) (Table 2). As HBL level elevated in diet, return on investment increased (L, P = 0.02), but cost per unit production decreased (L, P = 0.04).

Table 2. Effect of HBL on intake and growth performance of lambs.

	Level of HBL in diet (g/kg DM)					P value
	0	70	140	210	SEM	Linear	Quadratic
Initial body weight (kg)	30.7	31.7	31.1	32.0	1.16	0.89	0.87
Final body weight (kg)	51.3	50.9	50.4	52.5	0.71	0.86	0.48
DMI (kg/day)	1.70	1.78	1.62	1.70	0.024	0.12	0.18
ADG (g/day)	245	229	230	244	5.4	0.87	0.60
FE (gain:feed)	0.144	0.129	0.136	0.144	0.009	0.37	0.17
Return on investment	3.35	3.24	3.77	3.86	0.126	0.023	0.14
Cost per unit production^a	1.83	1.86	1.60	1.56	0.101	0.034	0.15

^a All costs in US dollar at the moment of conducting the experiment.

3.2. Carcass characteristics

The empty body weight, carcass weight, cold dressing percentage, digestive content, M. longissimus depth and width, and the weights of neck, shoulder, brisket, loin, legs and fat-tail were not affected by the diet (Table 3). Back-fat thickness was decreased (L, P = 0.05) with increasing the level of HBL in diet. The lambs receiving the greater dietary level of HBL had the lesser (L, P = 0.03) internal fat weight. In all the lambs, no differences were recorded for the weights of lean, bone and fat (Table 4). For dissected loin, fat weight was decreased (L, P = 0.05) as the level of HBL increased in diet.

Table 3. Effect of HBL on harvesting data of lambs.

	Level of HBL in diet (g/kg DM)					P value
	0	70	140	210	SEM	Linear	Quadratic
Harvesting data
Empty body weight (kg)	43.6	42.9	43.2	45.2	0.64	0.34	0.42
Hot carcass weight (kg)	27.6	27.3	27.6	28.7	0.41	0.21	0.26
Cold carcass weight (kg)	27.0	26.6	27.0	28.0	0.41	0.28	0.33
Cold dressing percentage	52.6	53.1	53.1	52.6	0.28	0.94	0.93
Digestive contents (kg)	7.65	7.20	7.56	8.01	0.166	0.41	0.28
Empty digestive tract (kg)	3.12	3.06	3.15	3.27	0.093	0.26	0.38
Back-fat thickness (mm)	8.90	8.80	7.0	7.4	0.43	0.052	0.22
M. longissimus width (mm)	55.1	52.1	54.3	53.5	0.85	0.48	0.92
M. longissimus depth (mm)	25.7	26.9	25.0	25.5	0.61	0.66	0.41
Carcass cuts (kg)
Neck	1.60	1.68	1.70	1.70	0.044	0.75	0.79
Shoulder	3.96	3.92	3.70	3.90	0.062	0.43	0.25
Brisket	4.68	4.68	4.70	4.96	0.126	0.77	0.71
Loin	3.24	3.30	3.38	3.34	0.067	0.58	0.57
Legs	7.60	7.54	7.68	7.88	0.103	0.78	0.68
Fat-tail	5.98	5.22	5.70	6.22	0.272	0.16	0.16
Offal parts (kg)
Skin	5.10	4.93	5.10	5.40	0.091	0.16	0.18
Head	2.42	2.24	2.26	2.30	0.045	0.29	0.35
Feet	0.96	0.95	0.99	1.10	0.033	0.15	0.18
Internal fat	0.57	0.47	0.41	0.39	0.074	0.035	0.11
Liver	0.81	0.75	0.78	0.81	0.022	0.87	0.88
Heart	0.21	0.19	0.19	0.19	0.046	0.48	0.39
Kidneys	0.13	0.13	0.12	0.13	0.012	0.26	0.13
Lung	0.55	0.61	0.56	0.58	0.016	0.59	0.62
Spleen	0.08	0.08	0.08	0.07	0.011	0.58	0.69

Table 4. Effect of HBL on carcass characteristics of lambs.

	Level of HBL in diet (g/kg DM)					P value
	0	70	140	210	SEM	Linear	Quadratic
Carcass components (kg)
Lean	11.9	12.2	12.3	12.8	0.31	0.18	0.83
Bone	4.48	4.44	4.69	4.79	0.144	0.11	0.15
Total fat^a	10.6	9.96	9.98	10.4	0.41	0.58	0.32
Lean to total fat ratio	1.13	1.22	1.23	1.16	0.065	0.23	0.57
Total fat proportion (%)	39.3	37.4	40.0	37.3	1.32	0.21	0.16
Loin composition (g)
Lean	1683	1715	1754	1755	42.6	0.45	0.42
Bone	951	967	1042	1033	39.2	0.14	0.23
Fat	606	618	585	552	28.4	0.050	0.43
Lean to fat ratio	2.78	2.78	2.99	3.17	0.156	0.15	0.28
Leg composition (g)
Lean	4010	4012	4107	4154	97.4	0.42	0.54
Bone	1408	1423	1440	1557	51.2	0.14	0.38
Fat	2182	2105	2133	2169	69.5	0.28	0.23
Lean to fat ratio	1.84	1.91	1.93	1.92	0.084	0.65	0.87

^a Total fat, fat-tail plus subcutaneous and intramuscular fat.

4. Discussion

4.1. Feed intake and growth performance

The lack of DMI differences among the experimental lambs was related to the relatively similar chemical composition (Table 1) and physical form (all the diets were in pellet form) of the diets, because composition and physical characteristics of feed affect the feed intake (Baumont 1996). Similar ADG among the treatments was in parallel to comparable DMI of the lambs, since the growth rate greatly depends on optimization of feed intake by animals and feed conversion to gain (Olfaz et al. 2005). The similar FE was related to the relatively unchanged DMI and ADG among the experimental lambs. Other researchers, also, reported no differences in FBW, DMI, ADG and FE when lambs fed on diets contained different levels of deep-stacked (Elemam et al. 2009) and autoclaved (Obeidat et al. 2011) BL. In another study by Mavimbela et al. (2000), ADG not affected when sheep fed diets containing sun-dried BL at the levels of 0, 280 or 560 g/kg.

The growth rate and FE in our lambs were lesser and DMI was greater compared to those predicted by NRC (1985), because the prediction equations used to estimate the performance of lamb in NRC (1985) were not obtained in Moghani breed sheep.

The improvement of production efficiency (cost per unit production) was due to the reduction of feed cost related to using HBL (relatively less cost CP supplement in Iran) in diet, and decrease the dietary proportion of soybean meal because traditional protein supplements price has risen in the last years (Ramos et al. 2009). Reduction of cost per kilogram live weight gain for the lambs fed 450 g/kg of BL in diet compared to those fed the control diet has been shown by Elemam et al. (2009).

4.2. Carcass characteristics

Feeding HBL had no adverse effect on the animal health, carcass characteristics and meat appearance. The numerically improved carcass weight in the lambs fed the diet contained 210 g HBL/kg DM compared to the other groups was associated to the better final BW in the former (Fàbrega et al. 2011; Hailu et al. 2011). In other researches, fasting live weight, weights of carcass, carcass cuts, non-carcass components, dressing percentage (Obeidat et al. 2011), and percentages of meat, bone and fat (Mavimbela et al. 2000) were not influenced by using BL in sheep ration. The same empty digestive tract weights among the animals could reflect the similar feed intake (Titi et al. 2008).

The similar weights of neck, shoulder, brisket, loin, legs and fat-tail among the experimental animals were associated to the similar ADG and DMI (Table 2). The lack of differences in offal weights, exception for internal fat, was possibly because these organs are more related to the animal's size than to its growth (Fimbres et al. 2002). Carcass component affect by animal weight. Energy requirement for deposition fat is more than lean tissue and customers prefer leaner carcass (Esenbuga et al. 2009). The numerically lesser carcass fat percentage in the lambs fed the diets contained increasing levels of HBL compared to those fed control diet could be reflect relatively improved carcass quality, depends on market and consumer demand. Jeremiah and Gibson (2003) reported no differences in meat chemical composition for Holstein steers fed diet containing poultry litter when compared to steers fed control diet.

The reductions of back-fat thickness, carcass fat and internal fat weight with increasing the rate of HBL in the diet might reflect lesser fat deposition and fatness. This was probably due to the effect of HBL on lipogenesis process by reducing ruminal production of acetate related to the fact that acetate can be used to synthesize subcutaneous fat (Obeidat et al. 2011). Additionally, the reductions of body fat could be, in part, due to decrease dietary EE content (Table 1) and thereby lesser EE intake in the lambs offered increasing level of HBL.

5. Conclusion

Using the HBL in the diet of Moghani fattening lambs up to 210 g/kg of dietary DM had no effect on feed intake, growth performance and animal health, but back-fat thickness, dissected loin fat, internal fat and cost per unit production reduced. HBL can be a cheap and safe feedstuff for use as a nitrogen source in sheep diet. Moreover, the use of HBL as a feedstuff can reduce environmental pollution.