Trop Anim Health Prod DOI 10.1007/s11250-016-1025-6
REGULAR ARTICLES
Nutritional quality and amino acid composition of diets consumed by scavenging hens and cocks across seasons Cyprial Ndumiso Ncobela 1 & Michael Chimonyo 1
Received: 8 December 2015 / Accepted: 14 February 2016 # Springer Science+Business Media Dordrecht 2016
Abstract The objective of the study was to determine the effect of season on nutritional quality and amino acid composition of diets that scavenging hens and cocks consume. Thirty hens and 30 cocks were purchased and slaughtered during each of the rainy, post rainy, cool dry and hot dry seasons. A total of 240 birds were used in the study. Fresh crop content weights were high (P < 0.05) during the cool dry season. Cereal grains, kitchen wastes, green materials, animal protein sources and inorganic materials were the main components of the crop contents. Crop contents varied with season and sex of bird (P < 0.05). The cereal grain weights were high during cool dry and hot dry seasons. Weights of animal protein sources (insects, locusts and termites) were higher (P < 0.05) during the rainy and post rainy seasons. Hens contained more animal protein sources (P < 0.05) than cocks. Hens had a higher (P < 0.05) lysine content during the rainy season than cocks. Histidine, serine, arginine, threonine, cysteine and lysine contents varied with seasons (P < 0.05). Methionine did not vary with season and sex of the bird. Nutritional supplementation of village chickens should, therefore, vary with seasons.
Keywords Amino acids . Cocks . Crop contents . Hens . Scavenging chickens . Seasons
* Michael Chimonyo
[email protected]
1
Animal and Poultry Science, School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, P bag X01 Scottsville 3209, Pietermaritzburg, South Africa
Introduction Scavenging chickens are an unexploited resource that is available to almost every resource-limited household (Mwalusanya et al. 2001). They are an integral part of rural communities. Despite their huge potential to improve food and nutrition security of undernourished rural households, several challenges limit their productivity (Sonaiya 1990; Dessie and Ogle 2001). One of the major challenges to chicken productivity is the inconsistent availability and quality of feed resources (Mwalusanya et al. 2002). Scavenging chickens hunt for feed materials from their surrounding environments. The materials consumed are influenced by the type of farming activities, locality, land size, flock size, planting to harvesting time, lifecycle of insects and seasonal conditions (Mwalusanya et al. 2002; Mekonnen et al. 2010). Since the nutritional quality of these scavengeable feed materials changes considerably (Ncobela and Chimonyo 2015), it is crucial to identify and characterize these sources of variation, as a first step in designing supplementation strategies to optimize production. Feed preferences for hens and growing chickens have been documented (Mwalusanya et al. 2002; Mekonnen et al. 2010). Hens predominantly prefer feed resources that are rich in proteins, calcium and phosphorous, such as insects and worms (Mekonnen et al. 2010). Growing chickens, on the other hand, tend to prioritize consuming energy-rich resources such as green forages and grains (Mwalusanya et al. 2002). Information on the feeding behaviour and nutritional composition of diets consumed by cocks is, to our knowledge, not available. This is despite the fact that cocks are the most commonly slaughtered class of chickens to maintain reasonable cock to hen ratio and to avoid fighting amongst each other (Wood et al. 1963). Since nutrient demands for hens may differ from that of cocks (NRC 1994), it is likely that the
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nutritional and physical compositions of feed resources they scavenge on differ. The objective of the study was, therefore, to assess the interaction of season and sex of bird on the physical and nutritional composition of the crop contents of scavenging chickens. It was hypothesized that the nutritional composition of feed items that scavenging chickens select varies with season and sex of bird.
Materials and methods Description of study site The study was conducted in Harry Gwala district municipality of KwaZulu-Natal province, South Africa from January to October 2014. The municipality receives a mean annual rainfall ranging from 800 to 1280 mm. It experiences four distinct seasons. These are the rainy (November to January), post rainy (February to April), cool dry (May to July) and hot dry (August to October) seasons. In the cool dry season, the district experiences mean annual temperatures range from 16.9 to 18 °C and occasional frost. Most residents in the district rely on crops and livestock for household consumption and income generation. Village chickens are among the important livestock species that are integral to the livelihoods of the households. The Harry Gwala district municipality is characterized by a variety of grass species which include Melinis repens, Cymbopogon excavatus and Paspalum dilatatum. Poor management of the grasslands has led to increases of grasses such as Eragrostis curvula, Eragrostis plana, Sporobolus africanus and Sporobolus pyramidalis (Mucina and Rutherford 2011). Common herbaceous plants are Amaranthus hybridus and Galinsoga parviflora. The majority of the households have backyard gardens. Common crops grown around the homesteads include maize, pumpkins, beans, taros, sweet potatoes and cabbages.
Trials Two trials were conducted. First, a structured questionnaire was administered to a selected random sample. Secondly, 30 households were identified with the assistance of the traditional leadership in the villages to sell at least one hen and one cock every season in 2014. Trial 1: household sampling for questionnaire administration and data collection All farmers who owned chickens were identified. A total of 160 households were then randomly selected based on ownership of scavenging chicken and willingness to participate in
the study. Each farmer who owned chickens had an equal probability of being selected for the study. The leadership, community project leaders and extension officers were actively involved in the identification of the farmers. A structured questionnaire was administered to households by four trained enumerators. The enumerators were obtained from the district municipality to make the interviewees comfortable with responding to questions and to provide reliable data. All selected households responded to all the questions. The questionnaire captured household demography, socioeconomic status and management of chickens. Transect walks were also made in the participating households to explore resource endowments and assess socioeconomic status of the households and the chicken breeds used. Trial 2: birds sampling and collection of crop contents From the 160 households interviewed in trial 1, 30 households who could afford to sell a hen and a cock in each of the four seasons were then selected. A total of 240 Ovambo chickens were used in the study. The hens had to go through at least one cycle of laying period while the cocks had to be at least 1 year old. The farmers indicated that pullets attained point-of-lay at about 6 months of age and also indicated that mature hens tended to have more experience in scavenging insects and other feed materials than younger birds. The cock had to show signs of sexual maturity, such as treading, crowing, pecking and chasing hens, copulating, mounting, tidbitting, waltzing and wing flipping. The sampling of the crop contents in the households was conducted over 2 days in each season. The same household was used to reduce across-household variation in the provision of supplementary feeds and housing. Birds were slaughtered in four different months to accommodate different seasons of the year. Birds were collected directly from the households between 1700 and 1900 h after spending the day scavenging. Live birds were weighed and slaughtered by any member of the household. Most of the chickens were slaughtered by cutting and dislocating cervical region using a sharp knife and manually plucking feathers after few minutes of hot water dipping of the carcass. Each bird was eviscerated and the digestive tract opened. The collection of crop contents was conducted in November to January (rainy season), February to April (post rainy season), May to July (cool dry season), and August to October (hot dry season). The crop of each bird was collected and placed in polyethylene plastic containers before being enclosed to cooler box with ice. They were then transported to the University of KwaZulu-Natal (UKZN), Animal and Poultry Science Laboratory. It took about 2 hours to transport the crops from study site to UKZN. Afterwards, they were allowed to defrost. The crop for each bird was dissected and the contents were sun-dried for 4 hours to avoid putrefaction before visual and microscopic observation. Observable feed particles were
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identified by visual observation. The tiny feed particles were identified using a low (×10) magnified microscope. The feed resources were identified and partitioned on as-is basis. These feed resources were physically partitioned and categorized as grains, kitchen wastes, green forages, animal protein sources, mineral sources and miscellaneous materials. Partitioned feed materials were weighed before they were mixed together for each bird. The crop contents of each bird were put into plastic bottles and stored at −20 °C, pending nutritional analyses (Mwalusanya et al. 2002). To account for differences in mean bird weights between treatments, the fresh contents of each bird were scaled to body weight. A scaled average fresh crop content was, therefore, calculated as the weight of fresh crop contents per kilogram body weight.
Chemical analyses of chicken crop contents All crop content samples were analysed in duplicate. The dry matter content (DM) was analysed in accordance to the standards of the Association of Official Analytical Chemists (AOAC) based on the official method 934.01 (AOAC 1990). To determine DM, the crop contents were heated in an oven at 100 °C for 16 h. Samples were then ground and milled to pass through a 1-mm sieve. Ash content was determined by incinerating the sample at 550 °C for 16 h (AOAC 1990). Nitrogen content of the DM was determined using the Duma Combustion in a Leco Truspec Nitrogen Analyser, St Joseph, MI, USA, according to 900.03 of AOAC (1990). Crude protein (CP) content was determined by multiplying the nitrogen content by a conversion factor of 6.25. Ether extract (EE) was determined using the Soxhlet apparatus according to method 920.39 of AOAC (1990). The crude fibre (CF) was determined using the ANKOM, AOCS Ba 6a-05. Neutral detergent fibre (NDF) content was determined according to ANKOM Technology Method 7-07-06, and acid detergent fibre (ADF) was determined according to ATM 08-26-05 using ANKOM200 Fibre Analyser (Ankom, Macedon, NY, USA) according to Van Soest et al. (1991). The CF content was determined using the ANKOM, AOCS Ba 6a-05. The NDF content was assayed using heat stable α-amylase (Sigma A3306, Sigma Chemical Co., St. Louis, MO, USA). Nitrogen-free extract (NFE) was calculated using the equation NFE (g/kg) =1000 − (CP g/kg + CF g/kg + EE g/kg + ash g/kg) (NRC 2001). The true metabolizable energy (TME) (MJ/kg dry matter) levels were determined by an indirect method using the formula TME = (3951 + 54.4EE − 88.7CF − 40.8 ash) × 0.004184 (Wiseman 1987). Amino acid analysis was conducted using the Technicon Sequential Multi sample amino acid analyser (TSM), as described by AOAC (1990). Calcium and phosphorus contents were determined by atomic absorption flame spectroscopy, according to method 6.5.1 (AOAC 1990).
Ethical considerations The questionnaire used in trial 1 was granted ethical approval (HSS/0584/013M) by the University of KwaZulu-Natal Human Social Science Research Committee. The study in trial 2 was granted the ethical clearance certificate (Reference number: 115/ 14-15/Animal) by the Animal Ethics Committee. Statistical analyses All data were analysed using SAS (2008). Household demography and chicken management were analysed using PROC FREQ of SAS (2008). The association between the sex of bird and season on the occurrence of animal protein sources was determined using the chi-square test. Data on physical and nutritional composition of crop contents were analysed using general linear models procedure of SAS (2008) based on the model: Yijk ¼ μ þ Si þ B j þ ðS BÞi j þ εijk; where; where Yijk is an observation for a physical, nutritional and amino acid composition of the diet, μ is the overall mean, Si is the effect of ith season, Bj is the effect of jth sex of bird, (S × B)ij the interaction of season and sex of bird, eijk is the random error. Least square means (LSMEANS) were generated and separated using the LSMEANS and PDIFF options, respectively using SAS (2008).
Results Trial 1: household demography and chicken management Table 1 shows a brief demographics and socioeconomic status of Harry Gwala municipality. The majority of the farmers were females and they relied chiefly on child support and old-age grants from the government. Scavenging chickens were integral components of all the households. Within each household, about 40 % of the chickens were owned by children. Seven out of 10 of the households did not provide appropriate overnight housing. From about 1900 h, they rested in tree branches and human dwellings. Sixty percent of those households that provided overnight housing for their chickens cleaned the houses. None of the households used disinfectants to clean their chicken houses. Provision of drinking water was occasional. The common chicken breeds kept were Natal game, Ovambo, Naked Neck and Venda. All the farmers allowed hens to scavenge with their chicks. Virtually, all (95 %) farmers reported that feed availability ranked as the biggest challenge to village chicken production. Three quarters of the respondents occasionally supplemented the diets of their chickens with maize grain. Rotten maize was commonly
Trop Anim Health Prod Table 1 Demographic and socioeconomic information of Harry Gwala district municipality
Variable
Percentage (n = 160)
Farmers who were single Farmers who were unemployed
56.0 64.7
Food secure households throughout the year
37.5
Major source of income Child support grant only
44.4
Old age grants
33.3
Formal work Households owning cocks
22.3 62.9
Households headed by women
53.7
Households regarding chickens as the most important Households with multiple ownership of chickens
57.5 81.2
Households providing supplementary feeding
75.0
Households providing overnight accommodation for chickens Households owning other livestock (cattle, sheep, goats)
32.5 48.8
Households using bought-in supplements for village chickens
5.0
used to feed chickens, especially during the post-harvest period. The farmers reported that village chickens show remarkable scavenging skills, unlike broilers and commercial-laying birds. Village chickens are able to hunt down insects, locusts and worms to meet their nutrient requirements. Scavenging of feeds occurred throughout the year for all classes of chickens. The farmers argued that birds that failed to scavenge were prone to predation. Extension officers also indicated that when imported birds are let to scavenge, they were prone to predation. Wild cats (80 %) and snakes (63 %) were reported as the important predators for chickens. Extension officers highlighted that the scavenging trait could be heritable and should be further improved to enhance the contribution of village chickens to rural livelihoods. Trial 2: birds and physical components of the crop contents Body weights of the chickens differed (P < 0.05) with season and the sex of bird. The interaction between season and sex of bird on the body weight of chickens was significant. The body weight of the birds was highest (P < 0.05) during the cool dry (2028.1 ± 149.89 g) and post rainy seasons (2001.9 ± 11.37 g). Cocks (2030.7 ± 146.71 g) had a higher (P < 0.05) body weight than hens (1766.1 ± 07.25 g). Cocks had a higher body weight than hens during the rainy season (P < 0.05) while during the post rainy season, the body weights of both sexes were similar (P > 0.05). The scaled fresh crop contents varied considerably with seasons. The scaled fresh crop content weights were highest (P < 0.05) during the cool dry season. There were more hens (P < 0.05) that had animal protein sources in the crop contents during rainy and post rainy seasons than cocks, which was not observed in the other seasons (Table 2). Common animal
materials found in the crops were beetles (Coleoptera), locusts (Acrididae), caterpillars (Larva), earthworms (Eisenia fetida and Perionyx excavatus), bugs (Hemiptera) and ants (Formicidae). The presence of insects, locusts or worms was associated with season (P < 0.05) and sex of bird (P < 0.01). A high number of hens (80 %) contained animal protein sources in their crops compared to cocks. Only a quarter of the slaughtered birds had animal protein sources during the cold and hot dry seasons in their crops. Three out of 10 chickens had kitchen wastes in their crops during the hot dry season. The effects of season and sex of bird on the weight of the crop contents and their physical components are given in Table 3. Cereal grains were the largest component of the crop contents (P < 0.05). The weight of the cereal grains in the crop was highest during cool dry and hot dry seasons (P < 0.05). Zea mays was the main cereal grain found in the crops during cool dry and hot dry seasons. Oryza sativa grains were mostly observed during the rainy season. The amount of kitchen wastes in the crops did not vary (P > 0.05) with either season or sex of bird. The common components of kitchen waste found in crops were cooked mealie meal, potato peels, cooked vegetable trimmings and canned fish remnants. The fresh weight of green materials in Table 2 Percentage of cock and hens which had animal protein sources in their crop contents across seasons Seasons
Cock
Hen
Significance
Rainy Post rainy Cool dry Hot dry
33.3 16.7 25.0 80.0
90.9 56.5 27.3 71.2
** * NS NS
*P < 0.05, **P < 0.01, NS not significant (P > 0.05)
Trop Anim Health Prod Table 3
Effects of seasons and sex of bird on the components of crop contents of scavenging chickens
Components
Scaled fresh crop contents (g) Physical component (g/kg) Cereal grains Kitchen wastes Green materials Animal protein sources Mineral sources Miscellaneous materials
Seasons (S)
Sex of birds (B)
P value
Rainy
Post rainy
Cool dry
Hot dry
Hens
Cocks
S
B
S×B
0.03 ± 0.002b
0.02 ± 0.002c
0.04 ± 0.002a
0.03 ± 0.002b
0.03 ± 0.001a
0.03 ± 0.002a
**
NS
NS
29.0 ± 6.71b 20.4 ± 5.82 7.9 ± 0.75a 1.5 ± 0.23a 1.4 ± 0.22a 1.2 ± 0.36
26.8 ± 6.92b
52.1 ± 6.36a
49.8 ± 7.23a
36.6 ± 4.08a
42.3 ± 5.46a
*
NS
NS
17.4 ± 5.29 5.1 ± 0.80b 1.0 ± 0.19a 0.9 ± 0.19 ab
15.4 ± 7.26 4.3 ± 1.12b 0.4 ± 0.38b 0.5 ± 0.25b
4.2 ± 8.43 3.3 ± 1.08b 0.4 ± 0.22b 00.4 ± 0.23b
17.8 ± 3.71 5.0 ± 0.60a 1.1 ± 0.12a 0.9 ± 0.15a
10.9 ± 5.71 5.3 ± 0.73a 0.6 ± 0.24b 0.7 ± 0.17a
NS ** ** **
NS NS * NS
NS ** NS NS
4.5 ± 3.10
3.4 ± 2.68
4.9 ± 2.02
4.4 ± 1.69
2.7 ± 1.95
NS
NS
NS
Values in the same row with different superscript letters differ (P < 0.05) *P < 0.05, **P < 0.01, NS not significant (P > 0.05)
crops was highest (P < 0.05) during the rainy season. Prominent green materials observed in the crop contents were Melinis repines, Cymbopogon excavatus, Paspalum dilatatum, Amaranthus hybridus and Galinsoga parviflora. The weight of animal protein sources in the crops was highest (P < 0.05) during the rainy and post rainy season. The weights of animal protein sources were higher in hens than cocks (P < 0.05). Inorganic matter, which was predominantly comprised of soil, sand, stones, grits, chicken bones and egg shells, occurred mostly (P < 0.05) during rainy season. Chemical composition of crop contents The chemical composition of the crop contents is given in Table 4. Hens and cocks had a similar DM content during Table 4
rainy and cool dry season. The DM content was, however, higher during the hot dry season in cocks compared to the hens. Crude protein and CF concentrations were higher (P < 0.05) in the rainy season. There was a significant interaction (P < 0.05) between season and sex of bird on the level of CP content. Hens had a higher (P < 0.05) CP during the rainy season than cocks. Cocks, on the other hand, had a higher CP than hens during cool dry season. The NDF and ADF were highest (P < 0.05) in the hot dry season than the other seasons. Season and sex of bird did not affect ash, calcium and phosphorus contents. Nitrogen-free extract and TME content were highest (P < 0.05) in the cool dry season. The relationship between TME and CP is depicted in Fig. 1. The CP content was highest during the rainy season and TME content was lowest (P < 0.05).
Effect of season and sex of bird on the nutritional composition in the diet of scavenging chickens
Chemical components (g /kg) Season (S) Rainy Dry matter Crude protein
668.3 ± 35.53 92.2 ± 5.75a
Ether extract Crude fibre NDF ADF Ash NFE TME (MJ/kg) Calcium (mg/kg) Phosphorous (mg/kg)
Sex of bird (B)
P value
Post rainy
Cool dry
Hot dry
Hens
Cocks
S
B
S×B
665.8 ± 31.17
624.9 ± 42.33
724.5 ± 36.43
661.3 ± 30.29
680.4 ± 41.44
NS NS *
18.9 ± 3.12 207.0 ± 11.57a 554.2 ± 36.73b 417.7 ± 40.99b
93.5 ± 5.76a 18.6 ± 3.12 169.9 ± 10.97b 671.7 ± 34.11a 566.8 ± 37.97a
81.9 ± 5.81b 18.6 ± 3.20 141.2 ± 13.88b 536.9 ± 47.72b 415.1 ± 53.12b
82.1 ± 6.64b 18.2 ± 3.79 120.6 ± 13.18b 749.5 ± 41.58a 649.5 ± 46.28a
90.9 ± 4.84a 19.0 ± 1.85 151.1 ± 7.45a 634.9 ± 23.53a 531.1 ± 26.19a
83.7 ± 7.15b 21.6 ± 2.76 168.3 ± 9.98a 621.3 ± 32.80a 493.2 ± 36.52a
* NS ** ** **
* NS NS NS NS
* NS NS NS NS
361.7 ± 53.85 267.8 ± 40.71b 3.1 ± 0.71b 108.6 ± 29.81 23.5 ± 2.77
287.4 ± 50.01 296.1 ± 40.71b 4.0 ± 0.71b 30.5 ± 27.41 22.8 ± 2.83
199.4 ± 69.95 471.7 ± 41.66a 7.9 ± 0.73a 64.1 ± 43.71 23.7 ± 4.05
413.9 ± 60.96 244.4 ± 49.47b 3.5 ± 0.86b 65.9 ± 34.39 20.7 ± 3.18
340.6 ± 23.53 339.9 ± 24.12a 4.9 ± 0.42a 83.1 ± 19.83 23.3 ± 2.67
290.6 ± 48.09 300.2 ± 36.00a 4.3 ± 0.63a 54.9 ± 28.82 22.0 ± 1.84
NS ** ** NS NS
NS NS NS NS NS
NS NS NS NS NS
Values in the same row with different superscript letters differ (P < 0.05) NDF neutral detergent fibre, ADF acid detergent fibre, NFE nitrogen-free extract, ME metabolizable energy *P < 0.05, **P < 0.01, NS not significant (P > 0.05)
Trop Anim Health Prod 120
10
100
8 7
80
6 60
5 4
40
3 2
Crude protein (g/kg)
True metabolisable energy (MJ/kg)
9
hen and cock, except for cysteine. Methionine, the first limiting amino acid in chickens, was not affected by season and sex of the bird. The concentration of lysine and cysteine in the crop contents was generally low across all seasons. There was a significant interaction between season and sex of bird on lysine concentration. The concentration of lysine in hens was highest during the rainy season, while, in cocks, it was highest during the cool dry season (P < 0.05).
Discussion
20
1 0
0
Rainy
Post rainy Cool dry Seasons
Metabolisable energy
Hot dry
crude protein
Fig. 1 Seasonal changes in true metabolizable energy and crude protein in the crop contents
Amino acid composition of crop contents Amino acid concentrations varied with season (P < 0.05) (Table 5). Histidine, serine, arginine, threonine and cysteine contents were significantly higher during cool dry season. For the essential amino acids, no difference was observed between Table 5
The high proportion of female-headed households observed in the study area indicates that females are liable for any homestead-related activities. Women play a major role in poultry production and management, in both female and male-headed households (Mekonnen et al. 2010). Scavenging chickens dominate other livestock in rural settings because they require low levels of inputs (Mwalusanya et al. 2001). Keeping chickens in human dwellings might limit the numbers and predispose them to diseases and parasites (Sonaiya 1990). Unavailability of housing to chickens indicates that farmers consider village chickens to be adapted to local harsh conditions such that they need no improvements in management. Mata and Mwakifuna (2012) suggested that the
Effect of season and sex of bird on the amino acid components in the diet of scavenging chickens
Amino acids components (g /kg)
Season (S)
Sex of bird (B)
P value
Rainy
Post rainy
Cool dry
Hot dry
Hens
Cocks
S
B
S×B
Histidine# Serine Arginine# Glycine Aspartate Glutamine Lysine# Threonine# Alanine Proline Cysteine# Tyrosine
1.8 ± 0.03b 3.5 ± 0.03ab 3.6 ± 0.04ab 4.9 ± 0.05 5.0 ± 0.07 11.3 ± 0.18 0.2 ± 0.04a 2.8 ± 0.03a 4.9 ± 0.06 6.0 ± 0.06 1.0 ± 0.02a 3.9 ± 0.04
1.8 ± 0.03b 2.9 ± 0.03b 2.8 ± 0.04b 4.4 ± 0.05 4.5 ± 0.07 9.9 ± 0.18 0.1 ± 0.04b 2.3 ± 0.03a 4.2 ± 0.06 5.6 ± 0.06 1.0 ± 0.02a 3.9 ± 0.04
3.0 ± 0.03a 3.9 ± 0.03a 4.3 ± 0.04a 5.5 ± 0.05 4.5 ± 0.07 11.4 ± 0.18 0.2 ± 0.04a 3.0 ± 0.03a 5.1 ± 0.06 7.5 ± 0.06 1.0 ± 0.02a 4.9 ± 0.04
1.6 ± 0.03b 1.2 ± 0.03c 1.3 ± 0.04c 3.9 ± 0.05 2.9 ± 0.05 8.7 ± 0.18 0.1 ± 0.04b 1.3 ± 0.03b 3.8 ± 0.06 5.5 ± 0.06 0.2 ± 0.02b 3.5 ± 0.04
2.1 ± 0.02 2.9 ± 0.02 3.2 ± 0.03 5.0 ± 0.04 4.1 ± 0.05 10.5 ± 0.13 0.1 ± 0.04 2.4 ± 0.02 4.6 ± 0.04 6.4 ± 0.04 0.6 ± 0.02a 4.4 ± 0.03
1.9 ± 0.02 2.9 ± 0.02 2.8 ± 0.03 4.3 ± 0.04 4.0 ± 0.05 10.9 ± 0.13 0.1 ± 0.04 2.3 ± 0.02 4.4 ± 0.02 6.0 ± 0.04 1.0 ± 0.02b 0.38 ± 0.03
* ** ** NS NS NS * * NS NS * NS
NS NS NS NS NS NS NS NS NS NS * NS
NS NS NS NS NS NS * NS NS NS NS NS
Methionine Valine# Isoleucine# Leucine Phenylalanine
1.6 ± 0.02 4.3 ± 0.04 3.0 ± 0.03 8.1 ± 0.10 4.6 ± 0.06
1.5 ± 0.02 2.8 ± 0.04 2.6 ± 0.03 7.4 ± 0.10 4.5 ± 0.06
1.8 ± 0.02 4.8 ± 0.04 3.0 ± 0.03 9.3 ± 0.10 5.9 ± 0.06
1.1 ± 0.02 3.4 ± 0.04 2.2 ± 0.03 7.0 ± 0.10 4.3 ± 0.06
1.5 ± 0.01 4.3 ± 0.03 2.8 ± 0.02 7.8 ± 0.07 5.2 ± 0.04
1.4 ± 0.01 3.7 ± 0.03 2.6 ± 0.02 8.1 ± 0.07 4.6 ± 0.04
NS NS NS NS NS
NS NS NS NS NS
NS NS NS NS NS
Values in the same row with different superscript letters differ (P < 0.05) #
Essential amino acids for chickens
*P < 0.05, **P < 0.01, ns P > 0.05
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scavenging behaviour is one of the traits of economic importance in rural chickens. It is important to estimate the degree of inheritance of the trait and develop genetic improvement programmes for village chickens, particularly where organic chicken production is targeted. The observed occasional dietary supplementation of village chickens concurs with earlier findings (Mwalusanya et al. 2002; Mekonnen et al. 2010). Dietary supplementation depends on feed availability. Indiscriminative feeding favours stronger individuals, such cocks and adult hens, to consume larger portions of the supplemented feed. In other terms, pullets, chicks and cockerels face a higher risk of not accessing the supplemented feed than their stronger counterparts. As a result, chicks and other small individuals are likely to be nutritionally impaired. The observation that few chickens had access to kitchen waste during the hot dry season suggests that households are likely not to be food secure for the whole year. It was estimated that more than 60 % of the households were not food secure. As such, few food left-overs are available for chicken consumption. The use of rotten maize in chicken feeding, although predisposing chickens to mycotoxins, indicates the sustainability of smallholder crop-livestock farming systems. Farmers recycle resources that are available to them. It is, however, crucial to determine whether, and to what extent, the performance of village chickens is impaired by toxic substance presence of mycotoxins. Seasonal and sex of bird effects on body weight were expected. The daily energy intake is likely to vary with the individual bird and with season, depending on the availability of energy-rich feed resources. High body weight of cocks than hens agrees with Maphosa et al. (2004) and is attributed to hormonal differences between the two sexes. High body weight of chickens during the cool dry season could be because of the abundance of maize grain (Goromela et al. 2008). Cereal grains are in high levels of dietary energy which results in high body weight (Proudfoot and Hulan 1987). The cool dry season is the time of the year when harvesting of cereal grains often occurs (Dessie and Ogle 2000). The abundance of cereal grains in the crop is, therefore, expected to be high since it corresponds to harvesting time. High amounts of kitchen waste during rainy season could be due to frequent and bulk cooking for visiting relatives since it is the popular period of family get-together functions. Food and, consequently, kitchen waste are abundant. High occurrence of green materials during the rainy season could be related to the abundance of emerging green sprout shoots that are palatable to the birds (Dessie and Ogle 2000; Mwalusanya et al. 2002). The finding that crop contents had high amounts of animal protein sources during rainy season could be attributed to the abundance of insects and invertebrates
during the rainy season (Ncobela and Chimonyo 2015). The difference in the amount of animal protein sources between hens and cocks is, however, difficult to explain. It could, however, be related to selective feeding behaviour which depends upon the nutritional requirements. Hens and cocks have different requirements (Nonis and Gous 2008) and, thus, select different feed resources during scavenging to meet their requirements. Surprisingly, both cocks and hens scavenged as one flock. Hens could have better ability to scavenge for protein-rich resources (Mekonnen et al. 2010) probably to meet nutrient for egg production. High amounts of mineral materials in the crop contents during the rainy season is related to the abundance of termites and earthworms that are fouled with sand, soils and grits after rainfall (Dahouda et al. 2008). The observed high CP content during the rainy season compared to other seasons could be related to the abundant swarm of insects and ample availability of worms and young plants found in the rainy season. High CP and lysine content in hens during the rainy season could be associated with selective feeding behaviour. High CP and lysine contents in scavenging cocks compared to hens during cool dry season could be associated with the physical dominance of cocks in the flock. Mekonnen et al. (2010) reported that DM was higher during the harvesting season. The CF content in the crop contents was higher than those reported earlier (Pousga et al. 2005). In commercial layers, the recommended CF for ration is 50 g/kg (Feltwell and Fox 1978). Crude fibre is poorly digested by endogenous enzymes (Mekonnen et al. 2010). High CF content in the crop contents of chickens during rainy season could be due to occurrence of green materials such as herbs and legumes that are rich in fibre. The consumption of undesirable materials such as feathers and pieces of wood may also contribute to high fibre levels. High indigestible fibre results in poor availability nutrients. The TME content was high during the cool dry season. The high TME and NFE value in the cool dry season in comparison to other seasons could be explained by the increased availability of cereal grains which had just been harvested (Dessie and Ogle 2000). Since feed consumption is largely determined by the energy requirements (Amaka Lomu et al. 2004), chickens are likely to require more energy during the cool dry season to maintain body temperature. The requirement for proteins is based on the amino acid content of the protein, rather than the CP per se. Amino acids are the building blocks of the muscle, metabolic proteins and enzymes that are required for maintenance (including scavenging requirements), supporting growth and egg production. It is, however, acknowledged that low CP content of diets leads to a lack of non-essential amino acids, reduces potassium levels and alters ionic balance (Dozier et al. 2008). The amino acid requirements for village chickens are, however,
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not known. The overall low amino acid levels could be as a result of scarcity or inconsistent availability of animal protein sources in the scavenging terrain. In addition, maize is deficient in the essential amino acids (Minh 2005). This could explain the low lysine content in crop contents during the cool dry season. Season did not affect the concentrations of glycine, asparate, glutamine, alanine, proline, tyrosine, methionine, valine, isoleucine, leucine and phenylalanine. These findings suggest that these amino acids are consistently available from the consumed feed materials throughout the year. However, they had a tendency to be low in concentration. Hens had higher amounts of essential amino acids than cocks, except for cysteine, where cocks had higher amounts than hens. The difference is not clear. Cysteine was low during the hot dry season. The digestibility of these amino acids needs to be determined, if attempts to accurately formulate feeds for scavenging chickens are to be made. Methionine is the first limiting amino acid in the diet of chickens (Ravindran and Bryden 1999). Season and sex of the bird did not affect methionine availability in the present study. Provision of adequate amounts of methionine diet of scavenging poultry will inevitably meet the needs for other amino acids. There is, therefore, a need to identify locally available methionine and lysine-rich feed resources such as earthworms, silkworm pupae (Zhenjun et al. 1997; Ncobela and Chimonyo 2015).
Conclusions The nutritional quality and amino acid composition varied with season and sex of bird. Cereal grains were abundant during the cool dry season. The amounts of animal protein and inorganic sources were notably high during rainy season. The animal protein sources were higher in hens than cocks during the rainy season. The NDF and ADF were highest in the hot dry season. Apart from lysine, the amino acids were significantly high during cool dry season. Lysine content was higher during the rainy season compared to other season in hens. Acknowledgements The authors are expressing unreserved gratitude to the Department of Agriculture, Forestry and Fisheries, Food Security Project for financial support Compliance with ethical standards The questionnaire used in trial 1 was granted ethical approval (HSS/0584/013M) by the University of KwaZulu-Natal Human Social Science Research Committee. The study in trial 2 was granted the ethical clearance certificate (Reference number: 115/14-15/Animal) by the Animal Ethics Committee. Conflict of interest The authors declare that they have no conflict of interest.
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