Periwinkle shell as an alternative calcium source on performance and egg quality of layer hens

N W Anizoba, S O C Ugwu, N E Ikeh, I E Uzochukwu, O F Orazulike and N S Machebe

Department of Animal Science, University of Nigeria, Nsukka
nnenna.nnajiofor@unn.edu.ng

Abstract

This study aimed at verifying the possibility of replacing limestone by periwinkle shell in the diet of layers. A total of one hundred and five (105), sixteen (16) weeks old pullets (weighing 1238± 12g) were randomly assorted into five (5) treatments groups with twenty-one (21) birds per treatment in a completely randomized experimental design. In the diets, the limestone was substituted by periwinkle shell (PS) at 0% (PS0), 25% (PS25), 50% (PS50), 75% (PS75) and 100% (PS75). Results showed that birds fed PS75 had the highest (P<0.05) feed intake and hen day egg production with an improved feed conversion ratio. The earliest age at onset of egg production was reached with birds fed P75. The inclusion levels of periwinkle shell significantly (P<0.05) improved most of the external and internal egg quality parameters studied with the best result recorded among the laying hens fed PS75 and PS100. On the other hand, there was no significant (P>0.05) effect on initial body weight, final body weight, total weight gain, egg weight, egg surface area, albumen weight, yolk weight, yolk height, yolk index and yolk colour. Based on the results obtained from the present study, it can be concluded that PS75 was appropriate for laying hens and the inclusion of periwinkle shell in layers ration as calcium source is more beneficial than limestone.

Key words: diet, environmental waste, limestone, poultry

Introduction

The success of poultry production depends on adequate feeding of quality feeds. Consequently, there are several registered commercial poultry feed manufacturers in Nigeria that are expected to meet the demands of prospective poultry farmers (Idahor and Adua 2010). Unfortunately, they are being accused of non compliance with the recommendations for different growth phases of poultry birds (Nweze 2008). Ultimately the purpose of poultry production is to convert feeds not edible by humans or surplus food resources into table eggs, chicken-meat and other by-products. Surprisingly, the so-called surplus foods are inadequate thus feed ingredients become unavailable or increasingly so expensive that most poultry farmers in Nigeria cannot afford them resulting in low poultry productivity (Omole et al 2005). This phenomenon will obviously lead to continuous competition for feed/food ingredients between the poultry industry and the human population. Therefore to drastically reduce this problem, several researchers have suggested the utilization of alternative feedstuffs in poultry nutrition (Agiang et al 2004; Idahor et al 2011a; Olomu 2011).

Calcium is used to improve the health of livestock, particularly bone health, but also in laying birds as a supplement to improve the quality and strength of eggshells. Eggshell quality is important in poultry production because a large number of eggs with defective shells cause great economic loss to the producer (Lavelin et al 2000). According to Leeson and Summers (2005), the use of medullar bones for eggshell formation results in sudden loss of 2g of body calcium therefore, a calcium bone reserve must be build up before the production period. A calcium source in the digestive system is an important factor for formation of eggs with optimum shell quality (Keshavarz and scot 1993). This implies that the source of calcium and its solubility in the gizzard influence eggshell quality and hen productivity. A low solubility is preferable to very rapid one, because the former more closely matches the prolonged duration of need for calcium supply to the shell gland in laying hens (Leeson and Summers 2005).

Periwinkle shell is very rich in calcium and can be manipulated to yield various calcium compounds. The shell is the hard, rigid outer calcium carbonate covering of certain animals (Ugoeze and Chukwu 2015). Roth-Bassell and Clydesdale (1990) found a differential solubility of each calcium source tested at different pH. The mean values show that calcium carbonate and marble dust are the most soluble. bivalve shell, periwinkle shell and oyster shell are of medium solubility while egg shell and snail shell dissolve more slowly with less than 50% solubility after 1 h in 0.1 N HCl. Such differences in solubility should be considered before these potential ingredients are used for diet formulation. Many calcium sources have been introduced and are in practical use with birds, such as egg shell, oyster shell, limestone and others ((Omole et al 2005; Safaa et al 2008 and Saunders-Blades et al 2009) but there is lack of information on the use of periwinkle shell as calcium sources for laying hens which currently has added to the environmental waste menace. For sustainable development, wastes should be recycled, reused and channeled towards the production of value added products (Abdulrahman et al 2014).

However, more recently and with more modern feed mixes, it has been shown that the addition of shells (Venus gallina) to a limestone supplement significantly improved the egg production performance of laying hens (Çath et al 2012). This means that shells are at least a comparable to commonly used limestone as a source of calcium for livestock with several studies (Oso et al 2011; McLaughlan et al 2014) suggesting that shell derived calcium carbonate (CaCO₃) can out-perform limestone.

This study aimed at evaluating the possibility of the replacement of limestone with periwinkle shell as an alternative calcium source in commercial layer diets.

Materials and methods

Location and duration of the study

The experiment was conducted at the poultry unit of the Department of Animal Science, Teaching and Research farm, University of Nigeria, Nsukka. Nsukka lies in the Derived Savanah Region and is located on longitude 6^o 25¹ N and latitude 7 ^o 24 ¹ E. The town is situated at an altitude of 430m above sea level. The climate in this area is humid tropical, with average annual rainfall range of 1680-1700mm. The mean air temperature is 26.6^o C (Breinholt et al 1981). The experiment lasted through a period of 12weeks (3months).

Collection of experimental feed ingredients

Periwinkle shell was sourced from the South-Eastern part of Nigeria. After collection, the periwinkle shell was washed severally by agitating in a sink under continuously flowing tap water until they were freed from the dark outer coatings. The shells were oven dried at temperature of 40^oC to reduce the moisture content but not to destroy the chemical contents. The dried shells were pulverized in a Hammer Mill after which they were used to substitute the limestone in layer diet. The periwinkle shell has 36.76 % Ca (Ajakaiye et al 1997) while the limestone contains 38 % Ca. The shell does not contain toxic factors, such as lead, cadmium, and arsenic (Ugoeze and Chukwu 2015).

Experimental birds and management

A total of one hundred and five (105) point- of- lay (POL) Isa Brown pullet of sixteen (16) weeks old purchased from a reliable farm were used for the study. They were placed on a commercial grower mash until they have reached puberty i.e age at first lay (20 weeks±9days) before being placed on the experimental rations for twelve weeks. The pullets were randomly assigned to five (5) treatments with twenty-one (21) birds per treatment. Each treatment was further divided into three (3) replicate groups with seven (7) birds each, housed in commercial cage equipped with individual pens well disinfected and cleaned in advance. Feed and water were supplied ad libitum to the birds. They were provided the same management conditions (temperature, light and vaccination programme). The control diet (PS0) contained 0% periwinkle shell, while in PS25, PS50, PS75 and PS100 diets, limestone was substituted by periwinkle shell at 25%, 50%, 75% and 100%, respectively (Table 1). The diets were prepared to meet the nutrient requirements of laying hens according to NRC recommendations (NRC 2005). The proximate composition of the experimental diet was carried out according to the standard method of association of officials’ analytical chemist (AOAC 1990).

Laying performance

Birds were individually wing-tagged in order to monitor individual body weight as well as the group body weight at the start (20 wk) to finish (32 wk). Body weight was obtained by weighing hens individually from each replicate weekly using a 10.1 kg capacity precision weighing balance (models A and D Weighing GK-10K industrial balance) made in China. Mean of each group was taken (A) and that of the previous week (B) was subtracted from it (A-B). The difference between the two divided by seven days gave the daily weight gain for a particular day in a week i.e., (A-B)/7 = daily wt gain (DWG).

Feed intake was determined by offering a known quantity of feed (X) to each replicate, morning and evening and the left over (Y) weighed the following morning. The difference between X and Y (X-Y) gave the quantity of feed consumed.

Average feed intake (g) = quantity of feed given – leftover feed

Feed conversion ratio was calculated daily from these data but was presented as the averages for the complete 16-wk period.

Egg numbers were recorded daily and summarized on a weekly basis throughout the experimental period (i.e., 20-32 weeks). Hen day egg production was evaluated by dividing the average number of eggs laid per bird per week by the average number of birds multiplied by seven, and the result was multiplied by 100.

Age at first lay was determined as the age at which the first egg was laid (Lawrence and Fowler 2002).

Egg quality analysis

Seventy-five (75) eggs were randomly selected at the end of the experiment for egg quality analysis by then the pullets have reached more than 50% of their laying performance. The eggs were collected daily and analyzed weekly for both the internal and external egg qualities with five (5) eggs randomly selected per replicate (i.e.15 eggs/treatment) for the assessments.

Egg weight was taken for every egg collected for the hens and the weighing was done for all the collected eggs within one hour of collection using a sensitive electronic balance (D & G sensitive scale) to the nearest 0.01g and the measurement was expressed in grammes.

The egg shells for each replicate were allowed to dry naturally at room temperature for 24 hours then weighed on an electronic sensitive balance with accuracy of 0.01 g to determine the shell percent.

The percent shell was calculated as: [shell weight (g) / egg weight (g)] × 100

The albumen and yolk heights were determined by utilizing the egg quality slide rule (Mohammed and Dei 2013). Albumin and yolk width were taken as the maximum cross sectional diameter of the albumin and yolk using a pair of calipers while albumin and yolk length was taken as the maximum vertical section of the albumin and yolk using a pair of calipers. Finally, the albumen index and yolk index were calculated as follows:

Albumen index = albumen height [albumen length + albumen width /2] × 100

Albumen and yolk weight were separated with the help of spatula and poured in two clean beakers and weighed in an analytical balance with accuracy of 0.01 g (Sinha et al 2017). The percent albumen was calculated as the ratio of albumen weight to the total egg weight and percent yolk was calculated as the ratio of yolk weight to the total egg weight according to Olawumi and Ogunlade (2008) as shown below:

Egg shell thickness (mm) was determined by using a micrometer screw gauge. Three (3) measurements were made on the sharp, blunt and equator of an egg and the average of the three values were considered as shell thickness of the egg as described by Ehtesham and Chowdhury (2002).

Egg length which is measured as the distance between the broad end and narrow end of the egg and the egg width which is measured as the diameter of the egg at the widest cross-sectional region were determined using a pair of vernier caliper to the nearest 0.01 cm (Olawumi and Ogunlade 2008). From the data obtained, the egg shape index was calculated according to Anderson et al (2004) as shown below:

Surface area (cm²) of each egg was calculated by using the formula of Carter (1975), (3.9782W^.7056), where W is the egg weight in grams.

Haugh Unit (HU) was estimated as HU= 100 log (H+7.57–1.7W^0.37)

Where:

H: albumen height.

W: egg weight (as reported by Oluyemi and Roberts 2000).

Eggshell weight per surface area (ESWSA), expressed in mg/cm², was determined according to Abdallah et al (1993) using the following formular:

ESWSA = {ESW/ [3.9782 x (EW^0.7056)]} x 1000

Where:

ESW = eggshell weight,

EW = egg weight

Egg specific gravity (ESG) proposed by Kul and Seker (2004):

ESG= EW/ (0.968EW – 0.4759ESW)

Where:

EW: egg weight.

ESW: egg shell weight.

Yolk colour was evaluated with the Roche calorimetric fan with a colour of 1 to 15

Statistical analysis

All the data collected were subjected to analysis of variance (ANOVA) in a completely randomized design using the general linear model procedure of statistical models for social science (SPSS version 16).When the analysis of variance indicated the existence of significant difference between the treatment means, Duncan’s multiple range test was used to locate the treatment means that was significantly different and significance was accepted at a 5.00% level. The experimental model was:

Yij= μ + ti+ eij where;

Yij= the response variable

μ= overall mean

ti = treatment effect

eij= error component

Results and discussion

Laying performance

The result of the performance of layer birds fed periwinkle shell as a replacement for limestone are presented in Table 2. The highest average feed intake (p<0.05) was seen on birds fed PS75 though, statistically similar with those that received dietary PS50 while the lowest (p<0.05) value was observed in birds fed P0, PS25 and PS 100. This could be attributed to the fact that although energy is the largest determinant of feed intake, hens have a specific appetite for calcium and therefore may vary feed intake to accommodate calcium needs (Safamehr et al 2013). The result showed a negative impact on increasing dietary periwinkle shell on birds’ intake which was most profound with PS100. Olivera (2001) observed a quadratic effect, when 3.6% calcium was added to diet, feed intake was decreased. This could be attributed to the fact that excess calcium has a neutralizing effect in the intestines which caused a rise of intestinal pH thereby causing deficiency by formation of insoluble calcium phosphate in the digestive tract (Keshavars 2000) and impairs metabolic functions (Kheiri and Rahmani 2006) that caused the birds to refrain from eating.

A better (P<0.05) FCR value was seen in birds fed P75 though statistically similar to P50 compared with those in other treatments. Improved Feed conversion ratio with decreased dietary calcium observed in PS50 and PS75 was associated with the capacity of the birds to maintain optimal egg production with an increase in their feed intake. The increase in their feed intake for calcium translates into more nutrients for egg production.

Higher egg production percentage and best feed conversion ratio occurred by using PS75 in this study than PS100 in the diet. This means that in calcium low diet, the parathyroid gland releases parathyroid hormone (PTH) which in turn stimulates the conversion of vitamin D₃ to the steroid hormone 1,25(OH)₂D₃. Increased production of 1,25(OH) ₂D₃ in the kidney results in increased intestinal absorption of calcium and phosphorus and bone reabsorption and reduces calcium and/or phosphorus excretion by the kidney (Proszkowiec- Weglarz and Angel 2013) to maintain normal plasma calcium and phosphorus concentration. These results proved that in calcium low diets, there is higher calcium utilization due to higher efficiency of intestinal absorption. So, birds improve the utilization of dietary calcium within their physiological limits as a form of compensation.

Birds on PS100 had the highest (p<0.05) age at first egg lay while birds on PS75 and PS50 reached the point of lay earlier than those on PS100. This could be attributed to the fact that birds have the ability to regulate their feed intake to meet their own needs for calcium and to adjust to low dietary calcium levels. Therefore, attempting to eat for the deficient nutrient (calcium), birds would over consume the other nutrients and energy in the feed. The over consumption of energy has been suggested to be responsible for the increase in body weight and the accelerated early attainment of puberty observed. However, Keshavarz et al (1993) did not observe any effect on performance when 33% fine limestone was substituted with oyster shell in the diets of laying hens.

Egg quality analysis

The result of the egg quality of layer birds fed periwinkle shell as a replacement for limestone are presented in Table 3. Physiologically, only an increase in age of birds increased egg weights resulting in decrease of egg shell thickness and its weakness. Therefore, lack of difference (p>0.05) in egg weights by different calcium sources is in agreement with Cheng and Coon (1990) who concluded through a series of experiments that switching from limestone to oyster shell in short-term laying trails caused no significant differences in layer performance including egg weight. That is to say that longer period of feeding high calcium diets to younger hens may be required before a significant adverse effect on performance will be detected.

There was significant (P<0.05) difference in egg shell thickness between the treatment groups fed on the treatment ration containing different levels (0-100%) of periwinkle shell in the current study. The highest eggshell thickness was obtained from eggs of hens fed the diet containing periwinkle shell at PS100. This result is consistent with the results obtained from Safaa et al (2008) who found an improvement in egg shell thickness for brown egg layer hens fed diets containing 4.0% calcium compared to those fed diets containing 3.5% calcium from 58 to 73 weeks of age. The increase in eggshell thickness may be because of the presence of the coarse particles of periwinkle shell. This shows that the larger particles (PS) would remain in the gizzard (an acidic environment) longer than limestone because of their low solubility, thereby having greater calcium retention than the small particle. However, the acidic environment would help to dissociate the calcium carbonate into ionic calcium, hence producing more available calcium for absorption. Hence, the more calcium that is available to the shell gland during egg shell synthesis, the thicker the egg shell will ultimately be.

The improved (P<0.05) egg shell weight observed in birds supplemented with periwinkle shell at 50%, 75% and 100% caused a decrease in the high gas interchanges through egg shell pores which finally improved albumin quality and haugh unit. A newly laid egg has an albumen height of 5 to 9 mm. In this study, albumen height and albumen index are in the range of 6.71-9.00mm and 5.26-7.83% respectively which indicates freshness. According to the United States Department of Agriculture (USDA), a haugh unitof 72 and above (score AA) is acceptable and indicates freshness in egg (Durunna et al 2007). Thus, the haugh unit obtained from all the group is an indication that eggs produced by hens were of standard quality. This result is in line with the findings of Guinotte and Nys (1991) who found significant differences in egg shell weight and haugh unit when hens were fed calcium.

The result showed that eggshell weight per surface area (ESWSA) increases or improves (P<0.05) as dietary calcium levels increase. Oliveira (2001) fed similar calcium levels (2.8, 3.2, 3.6, 4.0, and 4.4%) to commercial layers, but did not verify any effect on ESWSA. A possible reason for this difference may be the layer age, Oliveira (2001) used 72- to 88-week-old hens, whereas in this present experiment, birds were younger (20 weeks of age) at the beginning of the experimental period, and therefore, due to their high calcium requirements, responded better to dietary calcium in terms of eggshell weight per surface area. These differences among studies demonstrate the importance of determining the nutritional requirements of commercial layers as a function of bird age. The increase in ESWSA in group fed PS50, PS75 and PS100 may be explained by the study of Vicenzi (1996) who found that excessive dietary calcium increased calcium deposits in the egg, thereby increasing ESWSA.

Specific gravity is an indirect tool for eggshell evaluation because it is related to eggshell thickness and eggshell percentage. Generally, the higher (P<0.05) specific gravity value observed in group fed PS100 is related to thicker eggshell and shell weight per unit of surface area which is a desirable characteristic in the egg industry (Keshavarz and Quimby 2002). This result is in agreement with Pelicia et al (2009b) who reported that increasing the dietary calcium level up to 4.5% enhanced the eggshell percentage and eggshell weight per surface area as well as egg specific gravity

Conclusions

• Birds fed PS75 had the best feed conversion ratio which corresponds to a higher hen day egg production.
  
  
• The substitution levels of periwinkle shell improved most of the external and internal egg quality parameters studied with the best result recorded among the laying hens fed PS75 and PS100.
  
  
• Periwinkle shell can conveniently replace the use of limestone in the laying hens’ diet as a satisfactory calcium source while simultaneously reducing the environment burden of landfills.
  
  
• The use of periwinkle shell makes it possible to formulate a diet of lower cost, more appropriate to birds with a highly digestible calcium source at lower dietary concentration thereby maintaining the quality of the final product which is the egg.

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