The Scope and Effect of Family Poultry Research and Development
Novel pairing technique for estimating feed intake and nutrient digestibility by scavenging village chickens
A. O. Ajuyah
Proper estimation of feed intake by the scavenging village chicken is an important prerequisite for improving feeding systems and management. In terms of energy expenditure it is estimated that the metabolic cost of scavenging for feed or feed procurement by the village chicken is between 40 to 90% of total energy input from all feed sources. Less than 30% of this total will be available for tissue deposition, growth and egg production. However, there is no or limited information in the literature on energy and nutrient partitioning by village chickens, neither data on quantitative and qualitative estimation of feed utilization and digestibility. Therefore, this paper proposes the use of pairing technique (one live and one dead bird) to determine feed digestibility, by relating nutrient composition of crop content to feacal excretion and ileum digesta content between different pairs of village chicken of similar age, weight and sex. The proposed method will enable us to acquire quantitative and qualitative data to facilitate the growth and development of the village poultry industry.
Key words: Crop content, feed intake, nutrient digestibility, scavenging, village chickens.
One of the major production constraints to the development and growth of the rural family poultry in most developing countries is the estimation of feed intake and feed utilization under scavenging conditions. Such data will provide the basis for improvement in feeding management, in terms of supplementary feeding and stocking density or birds per unit scavenging area. However, scavenging areas are dependent on extrinsic factors such as feed availability, seasonal variables (e.g. temperature, humidity, rainfall, cyclones, wind speed and direction), level of predation, health and intrinsic factors such as relative position on the pecking order which is also related to scavenging behavior, age and sex. Therefore, the feeding behavior of the scavenging chicken, which is free ranging, negates data acquisition under natural conditions without partial or total confinement of the chickens. However, in terms of energy expenditure it is estimated that the metabolic cost of scavenging for feed by the village chicken is between 40 to 90% of total energy input from all feed sources, less than 30% of which may be available for tissue deposition, growth and egg production. This is in addition to the variable nature of feed quality, the cumulative effects being poor growth rate and low levels of meat and egg production.
At the University of the South Pacific, physical separation of local domestic and kitchen waste by one of our students indicates that over 70% is in a form which the scavenging chicken cannot properly utilize e.g. bone scrap, leaves, paper products, vegetable stump, liquid, fibrous garden and kitchen waste, etc. From this waste, the chicken can obtain up to 90% of daily-required energy intake. It could therefore be inferred that supplementary protein might be the most limiting nutrient in the diets of scavenging chickens, in particular for younger birds and laying hens.
Except for the recent study of Roberts and Gunaratne (1992) and Gunaratne (1999), there has been no research done in scientifically based methodology for estimating the feed intake of village chickens under natural conditions. Furthermore, the "proportion of the crop content, which is household waste determined by visual inspection" as suggested by Gunaratne (1999), is subjective and depends on the person who inspects it. Although the authors suggested that the amount of protein and energy in the Scavenging Feed Resource Base of scavenging chickens can be determined from an analysis of crop content or by reasonable estimation, this method does not provide information on apparent and true digestibility of the feed. Therefore, detailed information on the qualitative and quantitative feeding habits of the scavenging chicken would form the basis of proper feed management in particular for large size flocks (50+).
The proposed pairing technique outlined below should enable the acquisition of quantitative and qualitative data to achieve the following objectives:
a) estimation of feed intake and utilization by the village poultry – digestibility studies.
b) determination of variation within and between population on efficiency of feed utilization – scope for genetic improvement.
c) determination of the effect of supplementary feeding and feed composition on the scavenging ability and growth rate of the rural chicken – scope for improved management.
The sample size for qualitative and quantitative analysis of feed utilization by scavenging village chickens should be based on total number of chickens in a pre-selected location or site. For example, given an area of about 400 m x 200 m or 80,000 m2 with 500-1000 chickens from 25 to 40 families, the sample size should be:
See Calculations - 1
In this case the sample size is 40-50 chickens, we multiplied by 2 because the above ratio is less than 5 % of the total chicken population. The birds should preferably be of similar age group, and half of the chickens (20) or one pair should serve as live control and the other half or pair slaughtered for physical and chemical examination of gut contents (negative control). All 40 experimental chickens should be firstly wing banded and the left wing flight feather clipped to unbalance the chicken during flight and for ease of capture.
The experiment should commence with all the 40 birds confined in cages and feed withdrawn for 24 hours, this is to ensure complete emptying of the gastro-intestinal tract. However, drinking water should be provided ad libitum. The next day all the chickens should be released to scavenge for feed, and at regular intervals e.g. every two hours, 4 chickens should be caught and confined in cages. The village chicken is a continuous nibbler, and stops feeding only when the crop and gizzard are filled to capacity. Nibbling resumes once ingested feed starts moving from these organs, and occurs quite often in a day. In addition, over 80% of ingested free-range feed will remain in the crop for more than 2 hours after ingestion because of their large particle sizes, quality and the amount required to fill the crop. Therefore, based on this regulatory mechanism, one pair of chickens should be immediately slaughtered for physical and chemical determination of crop and ileum digesta contents. The other pair should be fed a diet containing an indigestible and visible marker dye such as chromic oxide, and total feacal excretion is to be collected until the appearance of dye in the droppings. Total feacal excretion and total crop content should be recorded and proximate analysis including energy content carried out on oven dried samples. Calculations for apparent and true nutrient digestibility are as shown below:
a. Apparent digestibility of nutrients, for example protein.
See Calculations- 2
b. True digestibility of nutrients, for example protein.
See Calculations- 3
To improve precision and reduce variability between and within flocks, birds of similar phenotype and genotype should serve as pairs. In addition adjustments should be made for differences in composition between actual feed consumed and crop content by multiplying by a pre-determined factor for the different nutrients, in particular for carbohydrates and energy, since starch digestion or hydrolysis has been initiated by ptyalin produced in the mouth. Data collected over a 24-hour period at 2 hourly interval would provide useful information on scavenging behavior of the village chicken including qualitative and quantitative characteristics of feed resources.
Scavenging is the main feeding system for smallholder poultry units, as a result of which village chicken production is usually classified as a low-input and low-output system (Kitalyi, 1999). However, feed procurement by the village chicken represents a significant proportion of energy expenditure and the importance of feed in scavenging chicken production is usually poorly estimated. To determine feed utilization by the village chicken, Gunaratne et al. (1993) analyzed crop content and reported similar results with previous study by Prawirokusumo (1988). They concluded that proximate analysis of feed and crop content and the presence of substantial amount of abdominal fat in all hens indicated that the availability of protein was a constraint on production in that environment. High abdominal fat deposition may be predisposed by multiple factors, and may also indicate inefficient nutrient utilization, including protein. Therefore, the determination of the chemical composition of crop content only is a poor indicator of nutrient utilization or digestibility.
This method suggests an indirect or pairing technique for the quantitative and qualitative estimation of feed utilization and digestibility by the village chicken, based on physical and chemical analysis of crop content in addition to chemical analysis of feacal excretion and ileum digesta content. Data obtained should provide a basis for improvement in feeding practices and feed management, based on input and output relationship. For example, it is possible that intake and availability of protein by scavenging chickens are dependent on the feeding habit of their live protein sources, worms and insects, etc., which occurs mainly at dawn and dusk or after rainfall. Therefore, to improve productivity based on efficient utilization of protein, energy supplying supplementary feed such as grains may be provided only at noon when live protein sources may be scarce or hibernating. Finally, proper understanding of nutrient utilization by the village chickens will provide information on feed conversion ratio, growth rate and therefore facilitated genetic selection and improvement in flock management.
Gunaratne, S.P. (1999): Feeding and nutrition of scavenging village chickens. Free communication 2, this First INFPD/FAO Electronic Conference on Family Poultry
Gunaratne, S.P., Chandrasiri, A.D.N., Hemalatha, W.A.P.M. and Roberts, J.A. (1993): The feed resource base for scavenging village chickens in Sri Lanka. Tropical Animal Health and Production 26: 249-257, cited by Gunaratne, S. P. in this First INFPD/FAO Electronic Conference on Family Poultry.
Kitalyi A.J. (1999): Family poultry management systems in Africa. This First INFPD/FAO Electronic Conference on Family Poultry
Prawirokusumo, S. (1988): Problems to improve small-scale native chickens' management in Southeast Asian countries. Proceedings, 18th World's Poultry Congress, Japan, pp. 113-117, cited by Gunaratne, S.P. in this First INFPD/FAO Electronic Conference on Family Poultry.
Roberts, J.A. and Gunaratne, S.P. (1992): The scavenging feed resource base for village chickens in a developing country. Proceedings, 19th World's Poultry Congress, Vol. 1, pp. 822-825, cited by Gunaratne, S. P. in this First INFPD/FAO Electronic Conference on Family Poultry.