Effects of supplementation of different levels of garlic (Allium sativum) on egg production, egg quality and hatchability of White Leghorn chicken

Meseret Asrat¹, Tesfaheywet Zeryehun, Negassi Amha¹ and Mengistu Urge¹

College of Veterinary Medicine, Haramaya University, P O Box-301, Haramaya, Ethiopia
tesfahiwotzerihun@yahoo.com
¹ College of Agriculture and Environmental Science, Haramaya University, P O Box 138, Haramaya, Ethiopia

Abstract

A 90 days study was conducted to evaluate the effect of feeding different levels of garlic powder inclusion on dry matter (DM) intake, egg production, egg quality, yolk cholesterol, fertility, hatchability, embryonic mortality, chicken mortality and chick quality of white leghorn layers. Some haematological values, total Protein and total immunoglobulin was also evaluated. A total of 180 chickens (156 layers and 24 cocks) with uniform body weight (BW) and eight month age were randomly distributed in to 12 pens and assigned to 4 treatments. Treatments were rations containing 0, 1, 2, and 3% garlic powder for Gp-1, Gp-2, Gp-3 and Gp-4, respectively.

The CP and ME content of treatment rations were 16-16.6% and 3021 -3244 kcal/kg DM, respectively. Body weight gain, hen-day and hen-housed egg production did not differ among treatments. Feed efficiency ratio (FER) and egg mass (EM) were not affected by the treatment. Albumen weight, albumen height, Haugh unit, yolk index, yolk height, egg weight, fertility, hatchability, embryonic mortality, chick weight and chick visual score were not affected by the treatments. An improvement was observed for yolk diameter, yolk weight, chick length and yolk color at 2% inclusion of garlic compared with other treatments. Shell thickness and and shell weight were not affected by the treatment. The mortality percentage of the control treatment was higher over other treatments.

Inclusion of 2% garlic powder improved yolk weight, yolk diameter, yolk color, and chick length, and lowered hen mortality. Mixing layer diets with 1-3% garlic powder could be used to improve some egg quality parameters without adverse effects on performance.

Keywords: garlic powder, mortality, prebiotics

Introduction

The poultry industry has occupied a leading role among agricultural industries in many parts of the world. The potential for further growth is obvious in view of the value of eggs and poultry meat as basic healthy foods in human diet (Daghir 2001). In Ethiopia, chickens are the most widespread, and almost every rural family owns birds, which provide a valuable source of family protein and extra cash incomes (Tadelle et al 2003). The total chicken population in the country is estimated to be 49.3 million. The majorities (97.3%) of these birds are indigenous breeds and maintained under a traditional system with little or no inputs for housing, feeding or health care (CSA 2011).

Eggs are a highly delicate food product, which could lose quality rapidly during the period between collection and consumption. Thus, improving and extending egg shelf life were included to the list of selection criteria for breeders and other researchers in the fields of production, management and nutrition. Reaching maximum egg production or body weight and producing disease free stock in return for each unit of feed intake is the aim of raising commercial poultry these days. But, there is negative correlation between productive traits and immune responses and also resistance against diseases (Demir et al 2003). Negative correlation between production and immunity in high performance strains, results in poor performance and immune responses (Demir et al 2003). Laying hen performance and egg quality are all heritable traits of major concern not only to breeders but also to industry and consumers this demand inspired many researchers to study the effects of various nutritional, environmental and managerial aspects to scale up these characteristics and to sustain high hen-production intensity as well.

Garlic (Allium sativum) is one of the most recognized plant species used for organic poultry production. Garlic is a bulbous perennial herb, closely related to the onion. It has anti-bacterial, anti-viral, anti-fungal, and anti-parasitic properties and has been used traditionally for ages to treat a wide array of diseases, namely, respiratory infections, ulcers, and diarrhea and skin infections (Fenwick and Hanley 1985). Reuter et al (1996) also reported garlic as a plant possessing antibiotic, anticancer, antioxidant, immune modulator, anti-inflammatory, hypoglycemic and cardiovascular- protecting effects. Garlic (Allium sativum) gained the trust of many scientists and cultural remedies all over the world for the prevention and treatment of many diseases and is broadly dispersed and consumed as a spice and herbal medicine for thousands of years.

According to reports of Sonaiya and Swan (2004), traditional treatment and control of poultry disease is important for Ethiopia as most developing countries. These countries cannot afford to import veterinary medicine and vaccination for chickens. In Ethiopia, farmers were trying to treat their birds traditionally. A survey conducted by Mengesha et al (2011) on the use of garlic as traditional treatment for birds indicated that 48.5% of the respondents were feeding garlic-onion and alcohol with soften injera to sick birds.

Ethiopia has a potential to expand poultry production, hence improving product quantity and quality is very important. But to achieve higher production and good quality poultry products, the way of production is very vital. To this end, organic poultry production is one of the opportunities that the country can highly benefit and exploit in terms of feed cost, human health issues and the availability of alternative herbal medicaments. Garlic is widely produced throughout the country from lowland to higher altitude, which makes the availability of garlic easier. The total area under garlic production in 2006/07 reached 9,266 hectares and the production is estimated to be over 683,000 quintals (MOARD 2007).

The major phytogenic compound obtained from garlic is allicin. This compound is derived from naturally occurring amino acid allin which is transformed into allicin (dially- thiosulphanate) by the enzyme allinase. This enzyme is inactivated by heat, oxygen and water (Mantis et al 1978) leading to reduction in both odour and medicinal properties of garlic. In pursuit of improved broilers health and in order to fulfill consumer expectation in relation to food quality, poultry producers commonly apply natural feeding supplements, mainly herbs (Gardzielewska et al 2003). Recent research works on herbal formulations as feed additive have shown encouraging results with regards to weight gain, feed efficiency, lowered mortality and increased liveability in poultry birds (Kumar 1991; Babu et al 1992; Mishra and Singh 2000; Deepak et al 2002; Jahan et al 2008).

Until now little effort has been made so far to evaluate the effect of garlic in production and reproduction and quality of egg when added in layer ration. Therefore, this research is designed to evaluate the effects of supplementation of different levels of garlic (Allium sativum) on egg production, egg quality and hatchability of White Leghorn Chicken.

Materials and methods

Study area

The experiment was conducted at Haramaya University Poultry Farm located 505 km east of Addis Ababa, at an altitude of 1980 m.a.s.l, 9°26 ^’N latitude and 42^o3^’E longitude. The mean annual rainfall is 780 mm. The mean annual minimum and maximum temperatures are 8^oC and 24, respectively (AUA 1998).

Experimental ration and ingredients

The feed ingredients used in the formulation of the different experimental rations of this study were Maiz (42.7%), Wheat short (18%), Noug seed cake (23%), Soybean meal (8%), Lime stone (7%), (0.5%) and Vitamin premix (0.8%). The newly harvested or fresh garlic bulbs were purchased from local market. Peeled fresh garlic bulbs (cloves) were grinded and subsequently the garlic paste was thinly spread on a mat and air dried. The drying process which took 5 days on average continued until the garlic paste gets dried to the level it can be mixed thoroughly with the ration. The prepared garlic powder was mixed with the diet of laying hens based on the specified levels. The diet has been stored at room temperature until it is fed according to the specified levels for layer hens. The layer treatment ration was formulated on an isocaloric and isonitrogenous basis to meet the nutrient requirements of 2800-2900 Kcal ME/Kg DM and 16-17 % CP (NRC 1994), respectively and water was always available to the chickens.

Experimental design and treatments

The experiment was conducted in a completely randomized design, with 4 treatments each with 3 replications. A total of 156 White Leghorn pullets and 24 cockerels at 8 months of age were obtained from Haramaya University Poultry Farm. They were randomly distributed to each replication making up 13 white leghorn layers per pen and 2 cockerels per replicate and a total of 45 birds per treatment. The treatment ration was formulated as Gp-1: Ration containing 0% garlic (control), Gp-2: Ration containing 1% garlic, Gp-3: Ration containing 2% garlic, and Gp-4: Ration containing 3% garlic.

Management of experimental chickens

Birds were adapted to experimental diets for 7 days before the actual data collection started. The experimental houses have wire-mesh partitioned pens with teff straw litter material of approximately 10 cm depth. Before the placement of the birds into the experimental house the experimental pens, watering and feeding troughs, and laying nests were thoroughly cleaned, disinfected and sprayed against external parasites. The feed was offered in a group per pen or replication twice a day at 0800 and 1700 hours throughout the experimental period. Feed were offered in hanging tubular feeders, which were suspended approximately at a height of the backs of the birds and water was provided in a plastic fountains placed on a flat wood at the center of the pen. Water was available all the time and the experiment lasted for 90 day (three months). Vitamins were given to the birds, turning the litter and changing of extremely wet litter with clean and dry was carried out whenever required. Mortality of chickens was recorded as it occurred.

Chemical composition of the experimental treatment diets

Representative samples were taken from each of the feed ingredients used in formulation of the experimental diet is indicated in Table 1. Dry matter (DM), crude protein (CP), crude fiber (CF), ether extract (EE) and total ash content by the method of AOAC (1990). Nitrogen was determined by using Kjeldhal procedure and CP was computed by multiplying the N content by 6.25. The metabolisable energy (ME) value was determined indirectly following the method given by Wiseman (1987) as follow:

ME (Kcal/ kg DM) = 3951+ 54.4EE – 88.7CF – 40.8Ash

The calcium, phosphorus and other mineral contents analysis were determined by atomic absorption spectrophotometer and UV (ultra violet). When the mean result of duplicates was not similar, the mean value of the two duplicates was taken, provided that the percentage error was not greater than 5%.

Dry matter intake, body weight gain, egg production and feed conversion ratio

A measured amount of feed was offered twice a day at 0800 and 1700 hours to the layers in each pen on ad libitum base. Feed refusal from each replicate was collected the next morning before the daily offer is given. The feed offer and refusal were recorded for each replicate and multiplied by the respective DM content. The amount of DM consumed was determined by the difference between the DM offered and refused. The difference between feed offered and refused was divided by the number of birds and experimental period to calculate the mean daily dry matter intake of each bird. Samples of feed offered were taken at each mixing and that of refused were taken every day from each pen and pooled per treatment, and sub samples of both were taken at the end of the experiment. Then, the samples of feed offered and refused daily per treatment were analyzed for their nutrient content according to the method mentioned earlier.

The hens were weighed at the beginning and end of the experiment. The weight per pullet was calculated as average of weights of pullets in the pen and recorded to form the initial body weight. Final body weight was taken at the end of the experiment and recorded. Body weight change per pen per bird was determined by the difference between the final and initial body weight. Average daily body weight gain or lose per bird for each pen was computed by dividing body weight change to the number of experimental days. Average body weights of each replicate were used for data analysis.

Eggs were collected twice a day from each pen at 10:00 am and 5:00 pm hours. The sum of the two collections along with the number of birds alive on each day in each pen was recorded. Rate of lay was expressed as the average percentage hen-day and hen- housed egg production based on the average values from each replicate following the method of Hunton (1995) as follows:

% Hen-day egg production = (Number of eggs collected per day/ Number of hens present that day)*100

% Hen-housed egg production = (Number of eggs collected per day/Number of hens originally housed)*100

Eggs collected daily were weighed immediately after collection. Average egg weight was calculated as the total weight of daily collected eggs divided by the number of eggs laid in each replicate. Then, average egg mass per hen per day was calculated using the following formula described by North (1984) as M = P x W, where; M = Average egg mass per hen per day; P = percent hen-day egg production; W = average egg weight in gram

Egg quality measurement

The internal egg quality was measured through break out analysis method. A total of 3 eggs per replicate were randomly taken from each treatment and their quality was measured once a week for 12 times. Accordingly, the egg quality parameters including egg shell quality (egg shell weight and its membrane), albumen weight, and height, and Haugh unit, yolk quality were determined. Yolk color was determined using Roche fan measurement strips where the scale was viewed from above and held in such a manner that the surface did not appear glossy (Vuilleumiler 1969); yolk diameter and height were determined using ruler and tripod micrometer, respectively; while weight of the yolk was measured by sensitive balance.

The Huagh Unit was determined by the following formula (Huagh 1937):

Huagh unit (H.U)=1oolog[H-(√G(30W^0.37-100)/100 +1.9], where H= albumen height (mm); G= 32.2, and W= weight of egg (g).

Yolk index was computed using the following formula:

Yolk index = (Yolk Height/Yolk Diameter)*100

Fertility and hatchability of eggs , chick quality and embryonic mortality

The eggs for incubation were collected for seven consecutive days and stored under recommended condition at the farm.

Fertility was determined by candling the incubated eggs on the 7 ^th day of incubation. Eggs that were fertile, i.e. eggs having small dark spot, numerous blood vessels arising from those dark spot of yolk were kept further in the incubator (North 1984). Fertility for each replication was computed by employing the following formula given by Bonnier and Kasper (1990).

% Fertility = (Total fertile eggs/Total egg set)*100

At the 21^st and 22^nd days of incubation, hatched chicks were collected and counted to determine hatchability in relation to the number of fertile eggs (North, 1984). The percentage hatchability for each replicate was computed according to the formula given by Rashed (2004) and Fayeye et al (2005).

% Hatchability on fertile egg base = (Number of Chicks hatched/Total Fertile eggs)*100

% Hatchability on total egg base = (Number of Chicks hatched/Total eggs set) X 100

Chick quality was measured using three different methods, which includes visual scoring, measuring day old chicks’ weight and length on 5 randomly selected chicks. The body weight of the chicks in grams (g) was measured using a sensitive balance. Chick length was recorded in centimeters (cm). All the three measurements were conducted on the same chick samples.

Embryonic mortality was determined by candling eggs at 14^th and 18^th days of incubation and the last three days of hatching. Mortality was classified as early, mid and late according to Butcher (2009) and embryonic mortality was computed according to the formula given by Rashed (2004).

% of early mortality = (Total number of early dead embryo/Total number of fertile eggs)*100

% of mid mortality = (Total number of mid dead embryo/ Total number of fertile eggs)*100

% of late mortality = (Total number of late dead embryo/ Total number of fertile eggs)*100

Data analysis

The data were subjected to statistical analysis using Statistical Analysis Software (SAS) (2008) version least significance difference (LSD) was used to locate the treatment means that were significantly different (Gomez and Gomez 1984). The model used for statistical analysis was:

Yij= µ + Ti + eij, where: Yij = the response variable; = over all mean; Ti = treatment effect, and eij = random error

General logistic regression analysis was employed for data recorded on fertility (fertile/infertile), hatchability (hatched/unhatched), yolk color (1/2/…/8), embryonic mortality (alive/dead) and visual scoring (poor/normal). The general logistic regression model is given below:

Model: ln π /1- π = β0+ β1*(X)

Test H₀: No treatment effect (i.e., ₁=0) vs. H _A: significant treatment effect ( ₁ where, Β= slope; X=treatment

Results and discussion

Feed intake and body weight gain

Effect of different levels of garlic powder in layers ration on dry matter (DM) intake and performance of layers are shown in Table 2. The DM intake of layers was 70.10, 80.96, 73.47 and 82.62 g/bird/day (SEM =1.888) for Gp-1, GP-2, Gp-3 and Gp-4, respectively and the highest DM intake was for Gp-4, but GP-2 is more than Gp-3 and Gp-1. In agreement with the current result, Khan et al (2007) showed that inclusion of 0, 2, 6, and 8% garlic powder (P<0.01) increased the feed consumption with increasing levels of dietary garlic in laying hens. This is an attribute of rich aromatic oils content of garlic which enhances digestion. Adibmoradi et al (2006) reported that garlic administration enhanced villus height and crypt depth and decreased epithelial thickness and goblet cell numbers in duodenum, jejunum and ileum of birds. Similar results were also reported by Nusairat (2007).

The morphological changes in the birds gut proclaim improvement in the digestive capacity and improved activity of pancreatic enzyme. In contrast, Khan et al (2008) found that supplementation of garlic powder had no effect on the feed consumption and feed efficiency in native Desi laying hens. Chowdhury et al (2002) reported that feed consumption, feed efficiency and egg production were not affected by supplementation of 0, 2, 4, 6, 8 or 10% garlic paste (P > 0.05) as averaged over the 6-week period. The discrepancy between results of this experiment and other similar work might be resulted due to the fact that the duration of the experiment was different and also the difference in garlic products.

Body weight parameters are presented in Table 2. There were no significant differences (P>0.05) in the 0, 1, 2 and 3% garlic powder supplemented groups for body weight gain. Qureshi et al (1983) as well did not report any differences in final body weight and daily feed consumption of pullets fed diets with various garlic products at levels equal to about 50 kg/ton of added garlic bulb. However, Lewis et al (2003) and Demir et al (2003) reported improved feed conversion ratio and body weight gain in broilers fed garlic. The variation may be due to the difference in garlic preparation as a feed supplement.

Based on the data in Table 2, HDEP and HHEP increased with curvilinear trends (Figure 1; R2 =0.97 and 0.97) as the level of garlic powder in the diet was increased. With 3% garlic powder, the HDEP was increased by 5% and HHEP by 16%. Feed conversion was not affected by addition of garlic powder.

Figure 1. HDEP and HHEP of white leghorn chicken fed diet containing different levels of garlic powder.

Egg production

The hen-day and hen-housed egg production of layers are presented in Table 5 and shown in Figure 2 and Figure 3, respectively. Although it was held numerically higher performance when compared to control diet fed group of hens, the hens supplemented with different levels of garlic didn’t differ in the performance. This experiment agreed with the findings of Reddy et al (1991) who reported that the values of body weight, egg production, egg weight, and feed efficiency of laying hens were not affected by supplementation of diets with 0.2 g/kg garlic oil. Yalcin et al (2006) showed that supplementing garlic powder at level of 5 or 10 g/kg showed numerical increase in hen-day egg production and a significant increase in egg weight. Similarly, Khan et al (2007) reported that laying hens fed dried garlic (2-8%) did not show a significant change when compared to the control diet fed group.

Gp-1 = Ration containing no garlic powder, Gp-2 =Ration containing 1% garlic powder, Gp-3 =Ration containing 2% garlic powder, Gp-4 =Ration containing 3% garlic powder

Figure 2. Weekly average hen-day egg production of white leghorn chicken fed diet containing different levels of garlic powder.

Gp-1 = Ration containing no garlic powder, Gp-2 =Ration containing 1% garlic powder, Gp-3 =Ration containing 2% garlic powder, Gp-4 =Ration containing 3% garlic powder

Figure 3. Average weekly hen-housed egg production of white leghorn chicken fed different levels of garlic powder.

Egg weight and mass

The egg weight and mass are presented in Table 2. There was no difference (P>0.05) in egg weight and egg mass between treatments. In agreement with the present study, Safaa (2007) indicated that egg weight and production performance were not affected by 2 % garlic addition. Khan et al (2008) and Chowdhury et al (2002) reported that egg weight was not affected by 0, 2, 6 or 8% garlic powder (P > 0.05) or by 0, 2, 4, 6, 8 or 10% garlic paste (P>0.05) as averaged over the six-week period, respectively. In contrast, Yalcin et al (2006) found that egg weight increased (P < 0.01) when laying hens were fed 5 and 10 g/kg garlic powder supplementation. And also Sakine and Onbasilar (2006) reported that egg weight increased with dietary garlic powder supplementation (P<0.01). These different results could arise from the use of different garlic sources, methods of preparation of garlic powder, and strains or age of layers used in the experiments.

Feed conversion ratio

The feed conversion ratio of layers is presented in Table 2. The feed conversion ratio did not differ between treatments. In agreement with the present study, Reddy et al (1991) reported that the values of body weight, egg production, egg weight, feed efficiency of laying hens were not affected by the supplementation of diets with 0.2 g/kg garlic oil. Chowdhuury et al (2002) added different levels of garlic to layers diet and reported no significant effects of this supplementation on growth feed intake and feed efficiency.

Egg quality parameters

The mean values of shell, albumen, and yolk weight are shown in Table 3. There was no difference in shell and albumen weight between the treatments. Yolk weight was higher in Gp-3 comparing to other treatments. Safaa (2007) who found similar result with the present study indicated that (2 %) addition of dietary garlic increased yolk weight, yolk color and Haugh unit and Chowdhury et al (2002) reported that sun-dried dietary garlic increased yolk weight. Ramakrishna et al (2003) reported that garlic supplementation probably enhanced the activities of the pancreatic enzymes and provided micro-environment for better nutrient utilization in rats. If this hold true on chicken, it partially explains the upward deviation in eggs’ components weight due to garlic administration compared to the controlled-fed group of hens. In contrast, Yalcin et al (2006) noted that yolk weight did not differ among dietary treatments experiments and Mottaghitalab and Taraz (2002) showed that the inclusion of 0, 5, 10 and 15 g/kg garlic powder decreased yolk weight. The diversity of garlic preparation and administration methods makes it harder to contrast our results with those in literature. Lawson et al (1992) recognized allicin to be an active component in garlic and they demonstrated that allicin is unstable and poorly absorbed from the digestive tract. Furthermore, garlic preparations that are produced by heat or solvent processes known to void allinase, and hence allicin may not be formed (Yu et al 1989).

The albumen and yolk height of layers are presented in Table 3. There was no difference in albumen and yolk height between the treatments. Pappas et al (2005) characterizes the decline in albumen deterioration rate as a function of the antioxidant status of egg contents. They proposed that organic selenium enhance the egg’s antioxidant status by upgrading the glutathione peroxidase activity in yolk and albumen. This in turn slows the process of lipid and protein oxidation during storage period; hence more valuable egg quality by extended storage time.

The yolk index and diameter of layers is presented in Table 3. There was no difference in yolk index among the eggs from hens consumed diets containing different levels of garlic powder and the control diet. The yolk index is a measure of the standing-up quality of the yolk. The yolk index values of the eggs from the various treatment groups ranged 0.41-0.42, which is within the accepted range of 0.33-0.50 for fresh eggs (Ihekoronye and Ngoddy 1985). The results of the experiments showed that the yolk diameter of layers in Gp-3 was higher than the other treatments.

The Haugh unit of layers was not different among treatments (Table 3). The values obtained for haugh unit for all treatments is within the standard value for egg quality determination based on this parameter. In agreement with this experiment results, a study conducted by Yalcin et al (2006) reported that the supplementation of garlic powder had no effect on egg albumen index, egg shell index and egg haugh unit values when laying hens were fed 5 and 10 g/kg garlic powder for 22 weeks. However, Lim et al (2006) reported that with an increasing level of dietary garlic powder, the haugh unit linearly increased after 2 weeks of storage

Egg shell thicknesses of layers are presented in Table 3. There was no difference in egg shell thickness among the eggs from hens consumed diets containing different levels garlic powder and the control diet. This finding is in agreement with the one reported by Sakine and Onbasilar (2006) who showed that the supplementation of garlic powder had effect on egg breaking strength, shell thickness, albumen index, yolk index and Haugh unit.

The logistic regression results for yolk color showed significant difference (pr >chisq <0.0001 at α = 0.05) with Wald chiSq value of 26.4 among the treatments. The treatment means from SAS output are presented in Table 4. The odd ratio value of Ga-1 vs. Ga-4 shows that Ga-1 has 0.467 times the odds of receiving a lower score than Ga-4 and the other follow the same trend. The Roche color fan reading recorded during the experiment ranges from 1 (pale yellow) to 8, with majority of the egg having 2 and 3 values on the yolk color point (Table 4). The Roche color fan number 7 to 8 (deeper yolk color) is accepted by consumers in most areas (Leeson and Summers 1997). But, the result of the present study is lower than this level for all treatments. Yolk color was greater in 2% addition of dietary garlic powder compared with control and other treatments in the 12th week. In agreement with the present result, Safaa (2007) reported that 2% addition of dietary garlic increased yolk weight, yolk color and Haugh unit. In contrast Birrenkott et al (2000) reported no differences in color and flavor in eggs from hens consuming up to 3% dietary garlic powder.

Fertility and hatchability of eggs are presented in Table 5. Wald chi-square statistics indicated that fertility and hatchability were not significant at α= 0.05 level of significance.

The mean percentage of embryonic mortality and chick quality are shown in Table 5 and 6, respectively. Based on Wald chi-square statistics the present result indicated that visual scoring of chicks and embryonic mortality were not significant at α= 0.05 level of significance. The statistical analysis showed no difference in chick weight. But, there was difference in chick length among the four treatments.

The mean percentage of mortality is shown in Table 5.During the entire experimental period, the birds were observed for morbidity and mortality. The average percentage mortalities of birds were 19, 13, 10 and 10% in the groups fed diets supplemented with garlic powder at 0, 1, 2 and 3%, respectively. The mortality percentage among the control and those supplemented with garlic powder were very high and it is lower in layers fed with diet consist of garlic powder. The result of the present study contradicts with Yalçın et al (2006) who reported that garlic powder supplementation has no effect on mortality in laying hens. The post mortem examination indicated that mortality was due to Ascaris and Swallowing head syndrome. Thus, decreased mortality in layers fed garlic powder containing diets may be attributed to the anti-parasitic action of garlic (Fenwick and Hanley 1985).

As indicated in the Table 5, the percentage of mortality of hens decreased in a curvilinear (Figure 4; R²=1) as the level of garlic inclusion in the diets increased.

Figure 4. Percentage of mortality in White Leghorn chickens fed with different levels of garlic powder.

Conclusions

• The present study revealed that inclusion of 2% garlic powder had significantly improved yolk weight, yolk diameter, yolk color and chick length, and in lower hen mortality compared to control group.
  
  
• It was concluded that mixing layer diets with 1-3% garlic powder can improve some egg yolk and egg shell parameters without adverse effects on performance and egg quality traits.

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Received 3 August 2017; Accepted 30 January 2018; Published 1 March 2018

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