Dietary ripe or unripe papaya (Carica papaya) peel powder improves egg quality in laying hens

Diarra Siaka Seriba, Waqa Taiwo, Tonga Kalatisi, Gilu Monica, Manu’a Oscar Pio and Andrew Stacey

School of Agriculture and Food Technology, the University of the South Pacific, Alafua Campus, Samoa
siakadi2012@gmail.com

Abstract

The effects of stage of ripening and dietary concentration of papaya peel powder on egg production, egg quality and gut health of laying hens was investigated. Two levels (25 and 50 g/kg) of ripe and unripe papaya peel powder were fed each to 3 replicates containing 10 Shaver Brown hens in a completely randomized design. Stage of ripening or dietary concentration had no effects on feed intake (FI), hen-day production, egg weight, egg mass and feed conversion ratio. There were no dietary effects on egg shape index, surface area and shell thickness but papaya peel powder supplementation improved Haugh unit (HU) and yolk colour. Dietary concentration or stage of ripening of papaya peel meal had no effects on ileal Lactobacilli and E. coli counts. We concluded that at concentrations up to 50 g/kg, dietary papaya peel powder have no effects on egg production and gut health regardless of the stage of ripening but even 25 g/kg improves egg quality in terms of Haugh unit and yolk colour. These findings have practical implications in the South Pacific region where green papaya fruits are always wasted. More studies are needed on dietary concentrations that might improve egg performance and gut microbiota.

Key words: egg production, feed additives, gut health

Introduction

Feed additives are included in poultry diets to improve feed conversion and product quality. However, the use of commercial feed additives in the feed is rapidly declining due to possible public health concerns and increasing demand for organic foods. In addition, commercial feed additives may not be readily accessible by small to medium scale farmers in most developing countries. Several plant products contain substances which have antimicrobial, anti-stress, anticoccidial, digestion-enhancing and anti--oxidative properties and the use of these as additives in poultry feed is attracting more research interest.

Papaya (Carica papaya) is a very important agro-forestry crop all over the South Pacific region, which may be found under coconut trees or in mixed-cropping with other fruits or root crops. This inexpensive fruit has a high nutritive value and is naturally rich in vitamins and minerals (Krishna et al 2008). It is a rich source of enzymes including papain and chymopapain and other anti-oxidant compounds which are known to improve poultry performance (Fouzder et al 1999). Papaya fruits are also reported to possess antimicrobial (Osato et al 1993) and cholesterolemic activities (Vij and Prashar 2015) which justify their application as phyto additives in poultry feed.

Papaya pulp from ripe fruits is consumed fresh but unripe papaya is also peeled and used in curries. Large quantities of unripe papaya fruits also fall naturally from the trees in the region and are wasted. During papaya processing, huge quantities of peels are discarded (Diarra 2018), which could be used as potential supplements in livestock and poultry feeds. Kamaruzzaman et al (2005) reported that feeding papaya peel meal at 120 g/kg had no adverse effect on broiler growth. The beneficial effect of papaya peel meal on egg production has also been reported by Fouzder et al (1999). One way of adding value to papaya peels could be its use as feed additive. Several factors including the stage of maturity of the fruit, processing methods, age of birds and diet composition may all affect utilization of papaya peel meals by poultry (Gueye 2002; Diarra 2018).

This research compared the effects of supplementing diets with peels from ripe and unripe papaya fruits on egg production and quality. We tested the hypotheses that dietary concentration of papaya peel meal and stage of maturity will not affect the production and quality of eggs from laying hens.

Materials and methods

Experimental site

The study was conducted at the Poultry farm of the School of Agriculture and Food Technology of the University of the South Pacific, Alafua Campus Samoa, where papaya is a major fruit crop. The ripe fruit is mainly eaten fresh but large quantities of unripe fruits are always found under the trees and these go as waste.

Processing of papaya peel and diet formulation

Peels from ripe (yellow) and unripe (hard green) fruits, collected under papaya trees in the school premise, were chopped into small pieces, sun-dried foor 72 h and ground to pass through a 1mm sieve. A control layer diet was formulated to contain 176 g crude protein /kg (Table 1). The basal diet was supplemented with papaya peel powder at 2.5 and 5 g/kg. Some steps of papaya peel powder processing powder are shown in Photo 1

Photo 1. Unripe (A) and ripe (B) papaya peels

Experimental birds and management

Shaver Brown hens (n=150; 147 days-old) weighing 1610 ± 92 g were allotted to 15 floor pens The experimental diets were fed ab-libitum to 3 replicate pens in a completely randomized design. Clean drinking water was supplied throughout a 70-day experiment. A 16-hour lighting programme was maintained throughout the period of the experiment. The animal ethics committee of the University of the South Pacific approved the experimental protocol.

Data collection

Feed consumption was monitored by difference between the quantities supplied and left over. Egg production was recorded per pen and hen-day production calculated as:

Eggs were weighed using a digital scale (Jadever JKH-500 series, Smartfox, Auckland, NZ) sensitive to 0.1 g and egg mass calculated as the product of eggs collected by the mean egg weight. Feed conversion ratio (feed/gain) was calculated per pen as the ratio of feed consumed to egg mass. Five eggs were collected per pen weekly for egg quality measurements. The length and width of the egg were taken using a digital veneer caliper and shape index calculated as:

Egg surface area (cm²) was calculated according to Nasr et al (2012) as 3.98 ×W^0.7056, where W is the weight of the egg. The eggs were broken on a glass table and shell thickness measured at 3 points (broad, narrow and mid-point) using a digital veneer caliper. Eggshell thickness was taken as the mean of 3 measurements. The height of the albumen was taken immediately at 3 places using a tripod spherometer. Haugh unit (HU) was calculated according to Eisen et al (1962) as: HU = 100 log (h-1.7w^0.37 + 7.6), where h is albumen height and w the weight of the egg. Yolk colour was evaluated using a Roche yolk colour fan (Hoffman-La Roche Ltd, Basel, Switzerland), graduated from 1 to 15.

At the end of the feeding trial, 1 bird was euthanised per pen (by cervical dislocation) for ileal microbial count. The ileum was removed from the Meckel’s diverticulum to the ileo-caecal joint. Ileal digesta was transferred into sterile tubes placed on ice and taken immediately to the Microbiology Laboratory for Escherichia coli and Lactobacillus counts. Samples were serially diluted from initial 10^-1 to 10^-9. About 100 µl of diluted samples were plated on the Eosin Methylene Blue (EMB) and deMan, Rogosa and Sharpe (MRS) agar media for E. coli and Lactobacillus), respectively. The media were incubated at 37º C for 24 and 48 hours under anaerobic and aerobic conditions, respectively. Colony counting was performed according to colony morphology and expressed as logarithm of colony forming unit (CFU) per gram of sample.

Statistical analysis

Data were subjected to analysis of variance (Steel and Torrie 1980) of a completely randomized design using the GLM of SPSS. Significant differences were reported at p = 0.05.

Results

Birds fed the test diets consumed more feed that those fed the control diet (Table 2). There were no treatment effects on hen-day production, egg weight, egg mass and feed: gain. There were no dietary effects on egg shape index, surface area and shell thickness (Table 3). Haugh unit of the 5 g/kg ripe peel powder group increased compared to the control. Haugh unit did not differ between the control and other test diets as well as among the test diets. Deeper yolks were recorded on the ripe peel supplemented 5 g/kg compared to the control. Yolk colour did not differ between the control and 2.5 g unripe peel/kg.

There were no dietary effects on Lactobacilli and E. coli counts and the ratio Lactobacilli: E. coli. (Table 4).

Discussion

The reason for increased feed iintake on the papaya supplemented diets may have been due to enhanced palatability. Several compounds identified in papaya fruit including vitamins (Pal et al 1980; Bron and Jacomino 2006; Bari et al 2006) and antioxidants (Mahattanatawee et al 2006; Gonzalez-Agular et al 2009) may improve its palatability. The presence of papain and other proteolytic enzymes in papaya (Noshad et al 2018) may also improve feed intake through enhanced digestibility of papaya peel supplemented diets. This difference in feed intake was not however, reflected in the egg performance parameters. These findings are in agreement with those of Leke et al (2018) who found an increase in feed intake of laying hens fed diets supplemented with papaya peel meal at30 g/kg diet. These authors also observed no effect of dietary papaya peel meal on egg production. There is therefore need for further studies with higher dietary concentrations of the powder to discern the possible effect of stage of maturity.

Haugh unit (HU) is an important measurement of egg freshness. The improved HU on the test diets may be attributed to the beneficial effects of papaya peel constituents. Dietary carotenoid content is a major factor affecting the yolk colour of eggs. Increased carotenoid content of papaya with ripening is well documented (Pal et al 1980; Bari et al 2006). The pattern of yolk observed in this study was attributed to higher carotenoid in the ripe peel. Leke et al (2018) also reported deeper colored yolks in laying hens fed diets containing 30 g ripe papaya peel meal/kg. The similarity in yolk color between the 25 g/kg ripe and 50 g/kg unripe further confirms the low carotenoid content of the unripe fruit. Where deeper coloured yolks are desirable, papaya peel will be a good alternative to commercial coloring agents both in terms of cost and safety.

The beneficial effects of papaya peel meal supplementation on gut microbial count in poultry is documented (Osata et al 1993; Kadiri et al 2016; Oloruntola et al 2018). The antimicrobial activity of papaya peel has been attributed to several phytogenic compounds including alkaloids and polyphenols (Oloruntola et al 2018). The similarity in ileal microbial count in this study may be due to lower dietary concentration with resultant low intake of the antimicrobial agents.

Conclusions

• We conclude that at inclusion levels up to 50 g/kg, the stage of ripening of papaya peel meal has no beneficial effects on egg performance parameters.
  
  
• Dietary papaya peel meal improved egg freshness and yolk colour.
  
  
• These findings have practical implications in the South Pacific region where green papaya fruits are always wasted.
  
  
• More research is needed in higher concentrations that would improve egg performance.

Acknowledgments

Authors acknowledge the teaching and research farm of the school of agriculture and food technology of the University of the South pacific for providing the experimental birds, feed and space.

Conflict of interest statement

Authors declare no conflict of interest.

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