Evaluation of high levels of rice milling byproducts in chicken layer diets: effects on layer performance, egg quality and economic returns

J G Maina, W N Kamau* and L W Kabuage**

University of Nairobi, College of Agriculture and Veterinary Sciences, Department of Animal Production, P. O. Box 29053 (00625), Nairobi, Kenya
maina.joyce78@gmail.com
* Ministry of Livestock Development, P. O. Box 34188 - 00100 Nairobi, Kenya
** Kenyatta University, Department of Agriculture Resource Management, School of agriculture
and enterprise development, P. O. Box 43844-00100, Nairobi, Kenya

Abstract

A study was done to evaluate feeds containing high levels of rice-milling by-products fed to layer chicken between 21 – 36 weeks and to determine economic returns to farmers from such diets. The rice based diets were also compared to a control diet based on maize and soybean meal, and a popular commercial layers diet used by poultry farmers. The rice by-products evaluated included Special Coarse Bran, Fine bran and broken rice. Special Coarse Bran is an inexpensive rice milling by-product produced during the rice milling process as a single combined product, consisting of rice bran, rice grains and some hulls. One hundred and sixty ISA brown layers were used for this purpose. They were housed in a battery cages measuring 45 x 45 x 18 inches and fitted with feeding and drinking troughs. Natural lighting system consisting of 12 day hours was used. Birds were vaccinated twice against Guboro on the 10^th and 21^st day while New Castle and Fowl Pox vaccines were given at twelve and a half weeks respectively. Five diets consisting of a commercial layer diet, a control diet based on maize and soybean meal and 3 test diets were used in the study. The commercial layer diet was a popular layer feed purchased from Unga Feeds Company in Nairobi. The three test diets contained 40% of broken rice, 20% fine bran and other ingredients.  Special coarse bran was added at 0, 5, and 10% of the diet respectively to make diets SCB-0, SCB-5 and SCB-10 which contained 60%, 65% and 70% of rice milling by-products respectively. Each diet was fed to 4 replicates of 8 birds making a total of 32 birds on each dietary treatment.

Birds fed on the commercial layer diet and the maize soybean control diet gained more weight and produced more eggs than those fed on test diets based on rice milling by-products. However, when economic returns were considered, gross margins were higher with rice based diets than with the commercial and the maize/soybean control diet. 

Key words: special coarse bran, broken rice, fine bran, gross margins

Introduction

Inadequacy of high quality and inexpensive raw materials makes animal feeds expensive in Kenya, particularly feeds for non-ruminant animals such as pigs, poultry and fish. Maize and its milling by-products have conventionally been used as the main sources of energy in animal feeds (Rama et al 2000). Maize, however, is also the staple food for most communities in Kenya, thus creating competition between animals and human beings for the commodity, which makes animal feeds expensive. There is need to evaluate alternative sources of energy and protein to facilitate the development of a sustainable animal industry. Rice milling by-products are plentiful, inexpensive and have potential to be successfully incorporated into poultry feeds.

According to Kuria et al (2003) eighty percent of all the rice consumed in Kenya is grown at the Mwea Irrigation scheme in Kirinyaga where abundant amounts of rice-milling by-products are also produced in the process of rice-milling. From inception of Mwea Irrigation scheme to 1998, rice milling was done by a government corporation, the National Irrigation Board in a multiple step process which produced rice hulls, coarse rice bran and broken rice as separate products. In 1998, milling operations were forcefully taken over by small scale farmers (National Irrigation Board, Kenya, 1998, Kibutha and Mutero, 2000) where rice was processed in a single stage process producing a single combined by-product referred to as “special coarse bran”. There is no documented information on the nutritional quality of this product. Such information would facilitate the development of appropriate technologies for utilization of the by-product.

According to Kingori (2012), approximately 10% of the total eggs produced are downgraded due to external defects while 1% is due to internal defects.  External defects include shell quality, cleanliness, shape, texture and soundness. Egg quality defects lower the grade, consumer appeal, storage/shelf life, hatchability, and increase egg breakage and cost of packaging. The purpose of this study was to evaluate the effects of feeding broken rice, fine bran and graded levels of special course bran on the performance of layer chicken and on internal and external egg quality parameters. An economic evaluation was also done to determine the diets that gave the highest economic returns to farmers.

Materials and Methods

Management of experimental birds

One hundred and sixty ISA brown layer chicks were obtained from a commercial hatchery (Kenchick Ltd) and used in the study. They were housed in a battery brooder for the first four weeks and thereafter transferred to battery cages in a grower/ layer house up to twenty weeks of age. The dimensions of the layer house were 35 feet (length) by 15 feet (width) and with long, wide corridors that served as working spaces. Natural lighting system, which was relatively constant at 12 hours per day, was used. This was provided through open sides of the house and chicken wire mesh in place. The open sides also provided adequate ventilation. Birds were housed in cages made of metallic wire mesh and measuring 45 by 45 by 18 inches and fitted with feeding and drinking troughs during the laying stage. A set of four (4) cages constituted an experimental unit. The first three cages in each experimental unit housed three birds each, while the fourth cage housed one bird. The birds were vaccinated twice against Gumboro at 10^th and 21^st day while the New Castle and Fowl pox vaccines were given at twelve and a half weeks respectively. Feed and water were ad libitum. Water troughs were cleaned daily to remove contamination from feed particles. The feed troughs were filled to three-quarter level to prevent spillage. Fecal material collecting on the floor under the cages was removed twice weekly to prevent any excessive build-up. 

Source of rice milling by-products and experimental diets

The rice milling by-products used in this study were obtained from the Mwea Irrigation scheme in Kirinyaga County. Fine bran and broken rice were obtained from the large scale mill owned by the National Irrigation Board, while Special course bran was obtained from the small scale millers. The other ingredients were obtained from a feed manufacturing company (Sigma Feeds Ltd), while maize was purchased from local traders. All ingredients and experimental diets were analyzed for their proximate constituents and calcium and phosphorus levels using methods described by the Association of Official Analytical Chemists (AOAC 1998). 

Five diets comprising of a commercial layer diet (COMM), a control diet based on maize and soybean meal (MSOY) and 3 test diets containing different levels of rice milling by-products (SCB-0), SCB-5, and SCB-10) (Table 1) were used in the study. The commercial diet was a commercial layer diet based purchased from one of the biggest feed millers in Kenya, while the maize soybean meal control diet was formulated without rice milling by-products for purposes of comparison. The three test diets were made from maize combined with 40% of broken rice, 20% fine bran, graded levels of coarse bran (0 – 10%) and other ingredients as shown in Table 1. The proximate composition and calcium and phosphorus contents of the diets are shown in Table 2 below.

Data collection

Layer chicken performance

Data on feed intake, body weight gain, egg production and weight of eggs was taken weekly over the 16 weeks of the study. Feed intake for each replicate per treatment was calculated as the difference between feed offered at the beginning of each week and the leftover at the end of the week. This was used to calculate the feed intake per bird. The total weight of birds for each replicate in a treatment was taken every week from which the mean body weight per bird in each treatment was computed. The mean body weight per bird for each replicate in a treatment at week 36 was used to compute the treatment mean. The difference between the mean weight of birds at 20 and 36 weeks of age was used to compute the weight gain per treatment.  

Egg production and quality

Eggs were collected 3 times a day and the mean number of eggs in each treatment was computed every week. Data was pooled together to give a mean for the 16 weeks laying period. Thereafter, the total number of eggs per treatment was divided by the number of eggs in each treatment to get the mean number of eggs laid per bird. Treatment means were calculated as the average of the four replicates. Egg mass and quality parameters were assessed as described below.  

Egg weight and mass

The total weight of eggs for each treatment was computed every week and divided by the number of birds in each treatment to give the egg mass per bird per week. The mean weight of eggs was computed from the total egg mass divided by the number of eggs for each treatment. The egg mass per bird divided by the number of eggs gave the mean weight of eggs per bird. Egg mass per bird was computed for the 16 experimental weeks. 

Egg shell strength

This was determined by the specific gravity method as used by Jacob (1993). Nine salt solutions with specific gravity ranging from 1.060 to 1.100 were prepared. Specific gravity of the salt solutions was increased at intervals of 0.05. Two eggs were selected at random from each replicate and labelled appropriately. The salt solutions were placed in beakers of 500 ml capacity and two eggs from each replicate immersed in each of the solutions separately. The strength of the solution in which each egg first floated was recorded as the specific gravity of the egg. The mean specific gravity of eggs from each of the replicates was computed as the average strength of the two solutions where each of the eggs floated. Treatment means were calculated as the average of the four replicates. 

York colour

One of the two eggs used for the assessment of shell strength was further used for yolk colour assessment. It was broken into a petri-dish and colour identified using a Roche colour fan. Treatment means were calculated as mean colour scores for the replicates. 

Yolk mottling

Yolk mottling was assessed using the following scoring system:

1. No visible mottling

2. Very slightly spotted (usually a small oval blemish of less than 0.15 cm in diameter.

3. Slightly spotted (2 – 4 small blemishes of 0.15 cm in diameter or 1 blemish of 0.3 cm diameter.

4. Moderate spots (easily detectable, often appearing as swirls or undulated shape covering 5 – 15% of exposed yolk surface

5. Severely spotted (covering up to 33% of exposed yolk surface)

6. Very severely spotted (covering up to 60% of exposed yolk surface)

Blood and meat spots

The method used was similar to that used by Jacobs (1993) through visually assessing the incidence of blood spot and meat spot blemishes. The scoring system used to was similar to that used to assess yolk mottling above. 

Economic evaluation

The market prices of ingredients were used to compute the break-even prices of the formulated diets. The mean feed intake per bird for each treatment over the experimental period multiplied by the unit cost of the corresponding experimental diet was used as the basis of computing the cost of feeding one bird. The selling price per tray of eggs multiplied by the number of trays/bird egg mass was the basis of computing the income. Net income per bird was computed as the difference between the income and cost of feeding. This was just a simple assessment to serve as an indicator on performance of diets and their costs and not a gross margin computation.

Statistical analysis

Treatment means were calculated using Microsoft Excel Program, while analysis of variance was done using Genstat Discovery Edition. Significant treatment means were separated using Duncan’s Multiple Range test according to Steel and Tory (1992).

Results and Discussion

Chemical Composition of Mwea rice milling by-products 

Fine bran had higher levels of lipids compared to broken rice and special course bran (Table 3). It also had high ash and crude protein contents. Fine bran is a mixture of pericap, seed coats and some aleurone layer. The latter component is relatively rich in protein which explains the high protein levels of fine bran compared to broken rice. The rice bran used in this study had lower crude protein levels and higher fiber content than that used by Samli et al (2006), but the crude fat contents were similar. Special coarse bran had a lower protein and higher fiber content than fine bran and broken rice. The crude protein contents of the diets (Air-dry basis) was 16.4% in the commercial diet, 17.9% in the control diet and 17.2% in diets based on the rice based diets. Crude fiber, ether extract, phosphorus and calcium were all within the stated stipulations (NRC 1998).  

Layer performance

Feed intake was lowest in birds fed on SCB-0 and highest among birds fed SCB-10, containing 10% Special course bran and 70% of rice milling by-products (Table 4). Birds fed on this diet (SCB-0) also had the lowest body weight and weight gain at 36 weeks of age. They gained less weight than those fed the all the other diets. It is not clear why birds fed this diet performed poorly compared to other treatments.

Egg production and quality

Trends in egg production closely followed those observed in weight gain, where birds fed on the commercial layers diet produced the highest number of eggs closely followed by birds fed on the maize/soya control diet.  Among birds fed diets based on rice milling by-products, those fed on SCB-0  produced the least number of eggs, while those fed SCB-5 with 65% rice milling by-products) produced the highest number.  

A similar trend was observed for egg mass (kg/bird) where birds fed on the commercial layer diet (COMM) and the maize/soya control diet (MSOY) had the highest egg mass, while among those fed on rice based diets, those fed on SCB-5 had the highest egg mass. 

In studies by Haghnazar and Rezaei (2004), it was demonstrated that inclusion of rice bran in layer diets increased egg weight, possibly due to elevated levels of linoleic acid in such diets. In this study, birds fed on diets made from rice milling byproducts produced eggs with lower egg mass than the commercial layer diet and the maize soya control diet. The best feed conversion ratio (kg feed: kg eggs) was recorded among birds fed on COMM and the MSOY diet, while those fed on SCB-10 had the poorest conversion of feed to eggs.

Egg quality parameters assessed in this study (yolk mottling, meat spots, blood spots and specific gravity) were not significantly affected by diet (Table 5).

Economic returns from diets

The gross margins per bird of the different diets are shown in Table 6 below. Birds fed the rice based diets gave higher economic returns than those fed on commercial diet and the maize/soya control diet. The gross margins for birds fed on the commercial diet were the least (115 Ksh per bird), while diets containing 10% special coarse bran had the highest returns of 163.8 KSh per bird.

Conclusions

• The best diets in terms of bird performance were the commercial layer diet and the maize/soybean control diet. Birds fed on these diets had the best performance in all the parameters assessed. However, birds fed on rice based diets had the highest gross incomes and gross margins. From this study, the general conclusion is that farmers would make more money using rice based diets than the commercial layer diet they are currently using.

References

Association of official Analytical Chemists (AOAC)  1998. Official methods of analysis 16^th Edition 1998 Maryland, AOAC International.

Kuria J N, Ommeh H, Kabuage L W, Mbogo S and Mutero C 2003: Technical Efficiency of rice producers in Mwea Irrigation Scheme. Proceedings of the African Crop Science Conference Vol 6 668 – 673.

Jacob J P 1993: The feeding value of Kenyan sorghum, sunflower seed cake and sesame seed cake for poultry. PhD thesis, The University of British Columbia.

Kabutha C and Mutero C 2000. From Government to Farmer-Managed Smallholder Rice Schemes: The Unresolved Case of the Mwea Irrigation Scheme.  http://publications.iwmi.org/pdf/H030840.pdf 

Kingori A M 2012. Egg Quality Defects: Types, Causes and Occurrence: a  Review. J Anim Prod Adv 2012, 2(8): 350-357.

National Irrigation Board (NIB) 2007. Latest news and upcoming events. http://www.nib.or.ke

National Research Council (NRC) 1998: Nutrient requirements of Poultry (Ninth Revised Edition). The National Academy Press. Washington, D.C.

Rama S V, Reddy M  R, Prarharaj N K and Shyam G S 2000. Laying Performance of broiler Breeder Chickens Fed Various Millets or Broken Rice as a Source of Energy at a Constant Nutrient Intake. Tropical Animal Health and Production (32) 329-338

Received 23 February 2013; Accepted 11 June 2013; Published 1 July 2013

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