Single or combined effects of date pits and olive pulps on productive traits, egg quality, serum lipids and leucocytes profiles of laying hens

Abstract

A six-week trial was conducted to evaluate the inclusion of date pits and olive pulps into corn-based diets (CDs) and their effects on performance, egg quality traits, serum lipid profiles and blood leucocytes subsets in laying hens. A total of 144 32-week-old Lohmann Selected Leghorn (LSL-Lite) laying hens were randomly distributed in 24 cages (six treatments and four replicates per treatment). The treatments were CD, wheat-based diets (WD), corn- and wheat-based diet (CWD), CD replaced with 20% date pits (DP) or 20% olive pulps (OP), or 10% date pits and 10% olive pulps (DP + OP). The results showed that the egg production and egg mass in the birds fed by-product diets were statistically (p<0.05) better than those fed WD and CWD and equal with those in CD group. The highest feed intake was observed in DP group and the lowest noted in the WD group. Treatments DP and OP also showed better (p<0.05) feed conversion ratio compared with treatments WD and CWD. In terms of egg quality traits, only yolk colour was affected by experimental diets (p<0.05). All serum lipid parameters were not significantly affected by experimental diets (p>0.05). Regarding the leucocyte profiles, only treatment WD showed higher (p<0.05) the heterophil: lymphocyte ratio compared with treatment CD. In conclusion, date pits and olive pulps could be partly used as alternative feedstuffs in the laying hens’ diets, without negatively affected the productive and health parameters

Keywords:

• date pits
• olive pulps
• productive performance
• blood parameters
• laying hens

1. Introduction

The high cost and restriction of high-quality raw materials for the poultry feed industry have resulted in an unconventional increase in the average cost per unit of production. Since about 70–80% of the production expenditure for intensively reared stocks is allocated to feed, it is necessary to continually evaluate new feed sources, including agriculture residues and food-industry wastes. In many countries, especially developing countries, reductions in feed costs are achieved by using cheaper and locally available feedstuffs (Al-Harthi et al. 2009). Wide ranges of these by-products including date pits and olive pulp, which are available in many countries, have already been causing environmental pollution problems.

Date pits are the residues obtained after extraction of oil from the date fruits and are produced in large amounts, which potentially can be used as a low-cost feed ingredient for poultry. The pit makes up approximately 10% of the total weight of the entire date seed. It contains a small amount but reasonably of protein and nitrogen-free extract, which somewhat is comparable to corn and barley (Kamel et al. 1981).

The olive pulps are the remaining raw materials after oil extraction from olive ripe fruit. Depending on methods of oil extraction (mechanical or solvent method), crude fat is variable in the pulps (Nefzaoui et al. 1982). It seems olive pulps can also be partly considered as energy source in poultry feeds.

In several studies, no negative responses in growth performance of broilers were caused by partly replacement of cereals with date pits (Hussein et al. 1998; Zaghari et al. 2009; Masoudi et al. 2010) and olive pulps into diets (Rabayaa et al. 2001; Abo-Omar et al. 2003).

Since date pits and olive pulps are produced in great quantities in Iran, and because of the low cost of these by-products, they can be used as the alternative feedstuffs in the laying hens’ diets.

Although there are reports indicating that the productivity and qualitative traits of eggs in laying hens were not adversely affected by the inclusion of date pits (Perez et al. 2000) and olive pulps (Zarei et al. 2011) in the diets, we found no scientific data regarding their effects on some health parameters such as serum lipids and leucocyte profiles. Moreover, the combined effects of these feedstuffs have not yet been investigated.

In the view mentioned above, this study was designed to investigate the singular and synthetic effects of date pits and olive pulps on laying hens’ performance and egg quality, serum lipid profiles and blood leucocyte subpopulations. The comparison was done between corn-based diets (CDs) containing date pits and olive pulps and diets based on corn or/ and wheat without tested by-products.

2. Materials and methods

2.1. Birds and diets

All procedures of the experiment were in accordance with the animal welfare norms. One hundred and forty four Lohmann Selected Leghorn (LSL-Lite) hens, 32 weeks of age, were randomly selected from a 2000-hens flock based on same weights and production rate. After two weeks of adaptation, the hens were randomly allotted into six experimental diets. The experiment was conducted in a completely randomised design with six diets as experimental treatments, which were as follows: Corn-based diet (CD), wheat-based diet (WD), corn- and wheat-based diet (CWD), CD replaced with 20% date pits (DP), CD replaced with 20% olive pulps (OP) and CD replaced with 10% date pits and 10% olive pulps (DP + OP). Therefore, six iso-caloric and iso-nitrogenous diets (Metabolisable energy (ME) = 2720 kcal/kg and CP = 15.42% of diet) were formulated (Table 1). There were four replicates (cages) per treatment and six hens per replicate. Hens were maintained at a 16:8 h light:dark cycle. The birds were housed into galvanised wire cages with dimensions 25×40×45 cm and had free access to their assigned diet and water during the feeding period.

Table 1. Feed ingredients and chemical composition of the experimental diets.^a

Ingredient,% of diet	CD	WD	CWD	DP	OP	DP + OP
Corn	66.18	–	43.95	41.00	41.96	41.61
Wheat	–	66.86	30.29	–	–	–
Fish meal	3.00	3.00	3.00	3.00	3.00	3.00
Soybean meal^b	15.92	7.08	12.75	18.83	20.24	19.40
Palm kernel meal	–	–	–	20.00	–	10.00
Olive pulp	–	–	–	–	20.00	10.00
Wheat bran	4.89	7.96	–	2.51	–	1.26
Soybean oil	–	5.15	–	5.05	5.05	5.05
Limestone	7.77	7.83	7.80	7.24	7.34	7.30
Dicalcium phosphat	1.31	1.22	1.29	1.38	1.42	1.39
Common salt	0.24	0.18	0.22	0.26	0.26	0.26
Vitamin-mineral premix^c	0.50	0.50	0.50	0.50	0.50	0.50
DL-Methionine	0.19	0.22	0.20	0.23	0.23	0.23
Calculated composition
ME, kcal/kg	2720	2720	2720	2720	2720	2720
Crude protein,%	15.42	15.42	15.42	15.42	15.42	15.42
EE,%	2.93	6.66	2.68	7.98	8.07	8.02
Crude Fiber,%	3.14	3.40	2.80	12.89	13.06	13.00
Ca,%	3.42	3.42	3.42	3.42	3.42	3.42
Non Phytate Phosphorus%	0.42	0.42	0.42	0.42	0.42	0.42

^a CD, corn-based diet; WD, wheat-based diet; CWD, corn- and wheat-based diet; DP, CD + 20% date pit; OP, CD + 20% olive pulp; DP + OP, CD + 10% date pit + 10% olive pulp.

^b Containing 44% crude protein.

^c The vitamin and mineral premix provide the following quantities per kilogram of diet: Vitamin A, 10000 IU (all-trans-retinal); cholecalciferol, 2000 IU; vitamin E, 20 IU (α-tocopheryl); vitamin K3, 3.0 mg; riboflavin, 18.0 mg; niacin, 50 mg; D-calcium pantothenic acid, 24 mg; choline chloride, 450 mg; vitamin B12, 0.02 mg; folic acid, 3.0 mg; manganese, 110 mg; zinc, 100 mg; iron, 60 mg; copper, 10 mg; iodine, 100 mg; selenium, 0.2 mg; antioxidant, 250 mg.

2.2. Chemical analysis

Proximate analyses of date pits and olive pulps, as shown in Table 2, were performed on the components of dry matter (DM), crude protein (CP), ether extract (EE), crude fibre (CF) and ash, according to AOAC (2000) procedures. Calcium (Ca) and total phosphorus (P) were determined by atomic absorption and spectrophotometer, respectively (FAO 1980). ME content of these feedstuffs were determined using Scott et al.'s (1976) equation (ME = 53 + 38 (CP% + 2.25×EE%+ 1.1×NFE%)).

Table 2. Nutrient composition^a of date pit and olive pulp.

Item	Date pit	Olive pulp
ME^a (Kcal/kg)	1983.82	1791.12
Dry matter (%)	92.11	87.97
Crude protein (%)	7.45	6.05
Crude fiber (%)	47.18	48.60
Ether extract (%)	4.82	5.32
Crude ash (%)	3.10	2.80
NFE^b (%)	29.56	25.20
Calcium (%)	0.91	0.68
Total phosphorous (%)	0.09	0.04

^a Metabolizable Energy (ME) was calculated according to the formula of Scott et al. (1976): ME = 53 + 38 [% CP+(2.25 ×% EE)+(1.1 ×%NFE)].

^b NFE, Nitrogen free extract = DM - (CP + EE + CF + Ash).

2.3. Productive performance

Three experimental periods were established: 34–36 weeks, 37–39 weeks and overall period (34–39 week). Eggs were collected and weighed daily per bird. The average egg weight, cumulative egg weight per birds and egg production (%) for each treatment were calculated during each period. Egg mass was calculated by multiplying egg weight by egg production. Feed intake (FI) per cage was recorded as the average FI/d/hen. Feed conversion ratio (FCR) was determined as feed consumed per egg mass.

2.4. Egg quality traits

At six weeks of experiment, eggs were taken from each treatment for three consecutive days, weighed and egg index (the height: length ratio) and shell weight, yolk and albumin height, width and length were recorded. The Haugh unit and yolk index were calculated as described by Stadleman (1977). Egg shell thickness was measured by averaging measurements at three separate locations (tip, flat end and equator) using electronic digital caliper scale. Yolk colour was determined using a Roche yolk colour fan (DSM nutritional products Co.). Colour scales ranged from 1 (pale yellow) to 15 (intense orange).

2.5. Serum lipid parameters

On day 42 of the experimental period, 3 ml of blood was collected from the brachial vein from two birds of each pen (eight birds per treatment). Serum was isolated by centrifugation at 3000×g for 10 minutes. Total cholesterol, triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), very low-density lipoprotein cholesterol (VLDL-C) and low-density lipoprotein cholesterol (LDL-C) in serum samples were determined using corresponding reagent kit (Pars Azmoon Company, Tehran, Iran) and an automatic biochemical analyser (Clima, Ral. Co, Espain).

2.6. Blood leucocyte subset counts

To study the effects of different treatments on blood leucocyte subpopulations, blood samples of two birds from each replicate were collected from the wing vein at the end of experiment, and ethylene diamine tetraacetic acid (EDTA)-containing blood samples were stained according to protocol described by Lucas and Jamroz (1961); subsequently, the different leucocyte subsets were counted.

2.7. Statistical analyses

All data obtained from the trials were subjected to the analysis of variance procedure of statistical analysis system (SAS 2001) according to completely randomised design. Means were separated by Duncan's new multiple range test. The level of significance was determined at p<0.05.

3. Results

3.1. Productive performance

The results of egg production and average egg weight of laying hens are shown in Table 3. Based on the results of this experiment, the egg production was lower (p<0.05) in treatment WD than other treatments except CWD. In terms of egg weight, there were no significant differences between hens fed by-product diets and those fed CD, whereas the egg weight of hens fed WD and CWD was lower compared with that of those fed by-product diets during weeks 37–39 or the overall period. Statistical analysis of data on egg mass showed that egg mass value was higher (p<0.05) in the birds fed DP compared with WD and CWD groups during the entire experimental period; additionally, other groups were intermediate and differed significantly (p<0.05) only with WD group (Table 4). The feed intake response was similar to egg mass. Feeding diets DP or OP yielded significant decreases (p<0.05) in FCR compared with diet WD during the overall experimental period.

Table 3. Effect of different experimental diets¹ on some performance parameters in laying hens.

	Egg production (%)			Egg weight(g)
Item	34–36 wk	37–39 wk	overall	34–36 wk	37–39 wk	overall
CD	93.0^a	94.5^ab	93.8^a	61.9	61.0^ab	61.5^ab
WD	81.9^b	74.0^c	77.8^b	59.7	59.3^b	59.5^b
CWD	89.1^ab	84.6^bc	86.8^ab	60.0	59.9^b	59.9^b
DP	93.8^a	97.3^a	95.4^a	62.9	63.7^a	63.3^a
OP	92.7^a	93.8^ab	93.3^a	62.7	62.6^a	62.6^a
DP + OP	91.1^ab	93.9^ab	92.5^a	62.4	62.8^a	62.6^a
SEM	1.40	5.15	3.66	1.34	1.10	1.21

Note: Values in the same column not sharing a common superscript differ significantly (P<0.05).

¹ CD, corn-based diet; WD, wheat-based diet; CWD, corn- and wheat-based diet; DP, CD + 20% date pit; OP, CD + 20% olive pulp; DP + OP, CD + 10% date pit + 10% olive pulp.

Table 4. Effect of different experimental diets¹ on other performance parameters in laying hens.

	Egg mass(g /d /hen)			Feed intake (g /d /hen)			Feed conversion ratio (g:g)
Item	34–36 wk	37–39 wk	overall	34–36 wk	37–39 wk	overall	34–36 wk	37–39 wk	Overall
CD	56.0^ab	58.0^ab	57.0^ab	117.5^a	118.4^a	117.9^ab	2.10	2.04	2.07^ab
WD	43.8^c	43.3^c	43.6^c	100.8^c	96.9^b	98.9^c	2.30	2.24	2.27^a
CWD	51.5^b	50.9^bc	51.1^b	109.2^b	111.4^a	110.3^b	2.12	2.19	2.16^ab
DP	59.2^a	61.9^ab	60.4^a	119.5^a	120.7^a	120.1^a	2.02	1.95	1.99^b
OP	56.9^ab	68.5^a	57.9^ab	116.6^a	114.7^a	115.7^ab	2.05	1.96	2.00^b
DP + OP	56.1^ab	68.8^a	57.4^ab	120.0^a	117.5^a	118.8^ab	2.14	2.00	2.07^ab
SEM	2.9	4.56	3.22	1.65	2.16	1.82	0.13	0.14	0.12

Note: Values in the same column not sharing a common superscript differ significantly (P<0.05).

¹ CD, corn-based diet; WD, wheat-based diet; CWD, corn- and wheat-based diet; DP, CD + 20% date pit; OP, CD + 20% olive pulp; DP + OP, CD + 10% date pit + 10% olive pulp.

3.2. Egg quality traits

The effects of dietary treatments on egg quality traits of laying hens are shown in Table 5. Only yolk colour was affected by treatments, so that the birds fed all diets except CWD, showed better (p<0.05) yolk colour than those fed WD.

Table 5. Effect of different experimental diets¹ on egg quality parameters in laying hens.

SCWD(mm)	SW^2(g)	Haugh unit	Yolk colour	Yolk index (%)	Egg index (%)	Item
0.36	6.69	67.59	8.75^a	48.21	76.07	CD
0.38	6.77	66.67	4.00^b	48.75	75.92	WD
0.37	6.60	64.65	7.25^ab	47.30	75.86	CWD
0.38	6.95	66.83	8.25^a	48.15	75.13	DP
0.36	6.72	68.53	8.25^a	49.43	74.70	OP
0.34	6.50	69.45	8.25^a	48.80	75.87	DP + OP
0.02	0.24	1.77	0.63	0.76	0.55	SEM

Note: Values in the same column not sharing a common superscript differ significantly (P<0.05).

¹ CD, corn-based diet; WD, wheat-based diet; CWD, corn- and wheat-based diet; DP, CD + 20% date pit; OP, CD + 20% olive pulp; DP + OP, CD + 10% date pit + 10% olive pulp.

3.3. Serum lipids

Regarding the serum lipid parameters, there were no significant differences (p > 0.05) among experimental treatments (Table 6). However, a trend was observed towards decreasing TG, total cholesterol, VLDL-C and LDL-C, as well as increasing HDL-C, in the serum of birds fed by-product diets compared with other diets, especially WD and CWD.

Table 6. Effect of different experimental diets^a on serum lipid profiles^b (mg/dl) in laying hens.

LDL-C	VLDL-C	HDL-C	TG	Total cholesterol	Item
106.75	40.8	54.50	214.3	202.5	CD
134.25	53.22	53.50	246.1	247.1	WD
134.25	46.3	50.75	236.5	221.3	CWD
106.50	37.9	59.75	199.7	196.3	DP
92.50	35.0	65.00	180.1	193.7	OP
102.75	38.3	70.25	191.8	199.8	DP + OP
19.8	6.4	9.7	33.6	31.3	SEM

Note: Values in the same column not sharing a common superscript differ significantly (P<0.05).

^a CD, corn-based diet; WD, wheat-based diet; CWD, corn- and wheat-based diet; DP, CD + 20% date pit; OP, CD + 20% olive pulp; DP + OP, CD + 10% date pit + 10% olive pulp.

^b TG, triglyceride; HDL-C, high-density lipoprotein cholesterol; VLDL-C, very low-density lipoprotein cholesterol and LDL-C, low-density lipoprotein cholesterol.

3.4. Leucocyte profiles

The leucocyte profiles of laying hens fed with different experimental diets are detailed in Table 7. The birds fed diet WD had a significantly lower (p < 0.05) lymphocyte count and higher heterophil:lymphocyte ratio than those fed diet CD. The birds fed WD statistically (p<0.05) had lower count than those on the control CD. The other leucocyte subsets were similar among experimental treatments (p > 0.05).

Table 7. The effect of different experimental diets¹ on proportion of leucocyte subsets in the blood of laying hens.

	Leucocyte subsets (%)
H:L	H^3	L^2	Basophils	Eosinophils	Monocytes	Item
0.47^b	28.50	60.25^a	4.50	2.00	4.75	CD
0.64^a	34.00	53.25^b	6.00	2.50	4.25	WD
0.58^ab	32.25	56.00^ab	4.50	2.00	5.25	CWD
0.54^ab	30.75	56.50^ab	5.75	2.50	4.50	DP
0.58^ab	32.00	55.25^ab	5.00	2.25	5.50	OP
0.56^ab	31.25	56.00^ab	5.75	2.25	4.75	DP + OP
0.049	1.386	1.403	0.343	0.108	0.297	SEM

Note: Values in the same column not sharing a common superscript differ significantly (P<0.05).

¹ CD, corn-based diet; WD, wheat-based diet; CWD, corn- and wheat-based diet; DP, CD + 20% date pit; OP, CD + 20% olive pulp; DP + OP, CD + 10% date pit + 10% olive pulp.

² Lymphocyte.

³ Heterophils.

4. Discussion

Generally, using the agricultural by-products and food industry wastes in poultry rations not only reduce the consumption of important feed ingredients, which have nutritive values for human nutrition, but also improve economic efficiency. In order to find out which and how much by-products can be used in poultry nutrition, various experiments are required with using different types of poultry. The current study designed to evaluate the effects of CD replaced partially with date pits and olive pulps on productive and health parameters in laying hens.

Our results indicated the inclusion of date pits and olive pulps separately or as the combination of both to CD made no negative effects on performance and egg quality parameters. In several experiments with broilers, no deleterious effects were observed on growth performance due to addition of date pits (Hussein et al. 1998; Zaghari et al. 2009; Mohebbifar & Torki 2011) and olive pulps (Rabayaa et al. 2001; Abo-Omar et al. 2003;) to diets. We found limited experiments on the use of these feedstuffs in the diet of laying hens. The results of the trial by Perez et al. (2000) indicated that date pits can be used up to 40% without significant effect on egg production and FCR, which is consistent with the results obtained from the present study. Zangeneh and Torki (2011) also used three levels of olive pulps in laying hen diets (0, 4.5 and 9%) and found no deleterious effect in terms of egg production and egg quality.

The higher crude fibre level and presence of anti-nutritional materials like non-starch polysaccharide (NSP) in date pits (Daud & Jarvis 1992) and olive pulps (Abo-Omar et al. 2003) probably are the limiting factors for using them in the poultry diet. However, in the current study, adding these by-products to the diets had no adverse effect on performance and health parameters, which is probably due to their inclusion levels. Moreover, another cause may be related to the fact that the low ME of by-product diets for hens was compensated by dietary oil, which neutralises their negativity. In general, it can be said that the usage dose of these feedstuffs in laying hens’ diet depends on their processing methods and probably chemical composition of basal diet.

The results of current study clearly indicated that WD (about 67% wheat) had the adverse effects on productive performance and egg quality of laying hens compared with other treatments. Moreover, the CWD (containing about 30% wheat) had slightly negative effects on performance and egg quality parameters. The negative effects of higher levels of wheat in poultry feed is clearly associated with the presence of xylans as the principal NSPs in wheat, which increase the viscosity of the gut contents following impediment of the circulation and absorption of nutrients (Annison & Choct 1991). Monogastric animals lack the enzymes in the digestive tract to degrade NSPs. Thus, to use higher doses of feed ingredients containing these anti-nutritional substances, it is necessary to supplement diets with NSP-degrading enzymes (Bedford & Schulze 1998).

Experimental diets did not yield any significant results on egg quality parameters except yolk colour score. At the end of experimental period, yolk colour values of hens fed WD was significantly lower than those of hens fed CD with or without by-products. Yolk colour is an important quality index for consumers, although the variation for preferred yolk colour has been found between geographical areas. If WDs are used without an additional source of carotenoids, the decline in yolk pigmentation may be resulted in reduced consumer acceptability for some applications (Beardsworth & Hernandez 2004). The preferred colour values ranges from 8 to 14 on the Roche colour fan (scale 1–15), i.e. from moderate yellow to orange (Nys 2000). Although the wheat is major crop produced in Iran, it should not be used as a main energy source of the laying hens’ diets without adding yellow natural or artificial colour additives due to its negative effect on yolk colour.

Regarding the serum lipid profiles, although there were no significant differences among treatments, but the birds fed diets containing date pits and olive pulps showed a trend to decrease total cholesterol, TG, and LDL-C levels and also to increase HDL-C levels in the serum. It may be associated with higher levels of crude fibre in the rations containing by-products, as shown in Table 1. Sarikhan et al. (2009) reported that higher fibre levels in the poultry diet reduce serum TG, total cholesterol and LDL-C levels. Although the mechanisms that higher dietary fibre may reduce blood fat levels are not fully understood, it has been proposed that the increased viscosity associate with soluble fibres may postpone the emptying of gastrointestinal tract, decrease intestinal motility and fat absorption thereby reducing lipid absorption (Razdan & Pettersson 1994).

Regarding to leucocyte subsets, the birds fed wheat control diet showed a decrease lymphocyte proportion and increased H:L ratio than other groups. This ratio is an index of response to a stressor (Maxwell 1993). The higher H:L ratio in laying hens fed WD seems to associate with an increased risk of developing stress conditions due to their diet chemical composition. The addition of by-product to the diets had no adverse effects on leucocyte profile, which may be due to the less health or welfare risks during the whole experimental period.

5. Conclusions

In conclusion, it could be suggested that date pits and olive pulps can be used, singly or in combination, at the level of 20% in the laying hens diets without negatively affecting their productivity and health. However, the potential effects of these by-products on growth and health parameters may be variable because of differences in the inclusion level, in composition and in origin. Therefore, we suggest further research on the same by-products to incorporate in poultry diets and their nutrition value in various doses and locations to achieve more comprehensive results. Moreover, the low-energy value of date pits and olive pulps requires to be balanced with a high-energy fat source to meet the energy needs of hens. However, more information is needed about the nutrients’ bioavailability in laying hens consuming diets containing above-mentioned feedstuffs.

Acknowledgements

This work was partly supported by company of Amol Joojeh in Iran. We are grateful to Mr Amir Miran the managing director and Mr Lotfollah Izadi the production manager of the company.