Effect of bird strain and gender on heart rate (HR) in beats/minute (bpm). Effect of bird gender on live body weight (BW), selected cut weight and offal in bareneck (NN), Ovamba (OV) and Potchefstroom Koekoek (PK) chickens.
GENERAL INTRODUCTION
- B ACKGROUND
- J USTIFICATION
- O BJECTIVES
- H YPOTHESES
- R EFERENCES
Determine the effect of strain, bird sex, and time of day on the behavior of free-range chickens NN, OV, and PK;. Poultry species and gender influence the behavior of free-range chickens NN, OV and PK;.
REVIEW OF LITERATURE
I NTRODUCTION
There is scope for exploiting the ability of local strains to adapt and survive in many challenging environmental and ecological conditions (Packard, 2014) given the growing demand for free range products worldwide. This review assesses the slow growth of chicken production in the context of the increasing popularity of organic meat and eggs in the context of the harsh environmental conditions prevailing in most parts of SSA.
C HICKEN PRODUCTION SYSTEMS
- Intensive systems
- Deep litter system
- Slatted floor system
- Battery cage system
- Semi-intensive systems
- Foraging chicken production systems
- Extensive production systems
There is little data on the foraging behavior of free-range chickens (Miao et al., 2005). Free-range scavenger hens are in direct contact with and can become infected with parasite vectors, soil, faeces (Abdelqader et al., 2008) and wild birds (Lervik et al., 2007).
S LOW - GROWING CHICKEN STRAINS
- Naked Neck
- Ovambo (OV)
- Potchefstroom Koekoek
- Venda
Less popular tribes, especially in South Africa, are the Nguni, Natal Game and the Zulu (Grobbelaar et al., 2010). Black Australorp roosters with White Leghorn hens and the Plymouth rock (Grobbelaar et al., 2010; Packard, 2014).
R OLE AND FUNCTIONS OF INDIGENOUS CHICKENS
T RENDS IN ORGANIC FARMING
While extensive farming systems predominate in developing countries, more by default than otherwise, the systems are well developed, as the meat and other products of such production systems are certified in the developed world. In addition, the organic market in the US alone has grown by 20% per annum over the past decade (ERS, 2002), while China has seen over 30% annual growth over the past five years (Jin, 2008).
F ACTORS INFLUENCING PRODUCTIVITY OF FREE - RANGE CHICKENS
- Strain and breeding for improved productivity
- Ambient temperature
- Body temperature
- Humidity
- Nutrition
Under free-range conditions, birds can be exposed to extremely high or low temperatures (Miao et al., 2005). However, the effects of humidity on thermoregulation and the performance of chickens depend on the ambient temperature (Lin et al., 2005).
E STIMATING NUTRIENT REQUIREMENTS OF FREE - RANGE CHICKENS
Where supplementation is done in the dry season (Mapiye et al., 2008), supplements are fed indiscriminately rather than preferentially. Different classes of chicks, including chickens, therefore compete for the allowance (Maphosa et al., 2004; Muchadeyi et al., 2004).
G UT MORPHOLOGY
Although an understanding of the seasonal feed intake of free-ranging birds is essential for developing supplementary feeding regimes, measuring the intake of foraging birds remains difficult due to the lack of appropriate methods (Miao et al., 2005). The visual assessment of crop content provides guidelines for diet composition, but cannot further quantify the pasture species consumed by foraging birds (Miao et al., 2005).
W ATER
However, there are views that some slow-growing species exhibit a high degree of tolerance to water scarcity and can survive at low water intake. This was attributed to either lower water requirements, a greater reliance on metabolic water to maintain hydration homeostasis, or a greater ability to budget body water economically in the former case.
P ARASITES
- Gastrointestinal parasites
- Ectoparasites of chickens
Among the diseases that reduce the productivity of free-range poultry, parasitic diseases are in the first place (Ashenaf and Eshetu, 2004). A higher incidence of parasitic diseases was observed in laying hens reared in free-range compared to cage-rearing systems (Fossum et al., 2009).
P REDATORS
T HE BEHAVIOUR AND WELFARE OF BIRDS
A SSESSING STRESS IN BIRDS
- Duration of tonic immobility
- Heterophil to lymphocyte (H/L) ratio
- Other indicators of stress
The more fearful birds show longer immobility responses when tonic immobility is induced (Altan et al., 2003). The TI test is based on a natural defensive response used by birds living in the wild when escaping a predator (Hrabcakova et al., 2012).
C ARCASS AND MEAT QUALITY
Other factors that have been used in the study of stress responses in chickens include; adrenal mediation directly by exogenous administration of adrenocorticotropin (ACTH) and exogenous administration of steroid moieties including corticosterone (Gross and Siegel, 1983), cortisone, cortisol, deoxycorticosterone and dexamethasone (Thaxton and Puvadolpirod, 2000b). Exposure to high environmental temperatures has adverse effects on poultry production efficiency and meat yield (Sandercock, 2001).
S UMMARY
The increasing popularity and demand for free-range and organically produced meat and eggs provides an opportunity for intensified free-range chicken production. Potential environmental stressors should be evaluated in light of their effects on bird behavior, physiology, gut morphology, welfare and thus overall performance of free-range chickens.
R EFERENCES
Prevalence and distribution of gastrointestinal helminths and their effect on weight gain in free-range chickens in central Zambia. Effect of a free-range rearing system on growth performance, carcass yield and meat quality of slow-growing chicken.
EFFECTS OF STRAIN AND SEX OF BIRD ON THE BEHAVIOUR OF FREE-RANGE
I NTRODUCTION
Free-range systems make use of slow-growing strains, which are more suitable for these production systems (Castellini et al. 2002; Gordon and Charles 2002). Slow growing strains are preferred for their pigmentation, taste, flavor and leanness (Moreda et al., 2013).
M ATERIALS AND M ETHODS
- Animal ethics
- Study site description
- Treatments and experimental design
- Housing, feeding and health management
- Observations and data collection
A thermometer was kept in the house just above the level of the birds and used to monitor temperature changes. For behavioral observations, 3 birds, one of each species, in each of 4 pens were randomly selected and marked with ink on the tip of the tail 20 min before leaving the cage at 07:00.
S TATISTICAL ANALYSES
Ambient temperature (°C) and relative humidity (%) were recorded on the same days as behavioral observations. As a result, meteorological data reported in the current study correspond to measurements made on the day of observation.
R ESULTS
- Meteorological observations
- Body weights
- Time spent foraging and drinking water
- Time spent standing and walking
- Other observations
Breed and sex of birds were the only factors that (P < 0.05) influenced time spent walking. Breed and sex of birds were the only factors that (P < 0.05) influenced time spent walking.
D ISCUSSION
Broiler chickens exposed to high temperatures and humidity have been reported to have reduced body weight, possibly indicating reduced feed intake (Lin et al., 2005). The high THI values ​​found in the current study discouraged foraging due to increased heat stress (Lin et al., 2005).
C ONCLUSIONS
The high THI had a positive influence on standing and preening behaviour, as birds normally thermoregulate during behavioral changes. High ambient humidity exacerbates the effects of high temperatures by reducing the effectiveness of panting to induce evaporative cooling from the airways (Warriss et al., 2005).
R EFERENCES
Changes in the body temperature response of bareneck and normally feathered chickens to heat stress. Response of bareneck (Nana) and normal (Nana) broilers to dietary energy levels in a subtropical climate.
PHYSIOLOGICAL RESPONSES IN SLOW-GROWING CHICKENS UNDER
I NTRODUCTION
In chickens, as Ta increases, heat production decreases while heat release increases (Lin et al., 2005). They are known to be thermally tolerant (Fathi et al., 2013) and generally adapted to harsh environmental conditions.
M ATERIALS AND M ETHODS
- Animal ethics
- Description of study site
- Treatments and experimental design
- Bird management
- Brooding, feeding and health management
- Data collection and measurements
- Meteorological measurements
- Body weights
- Physiological responses
- Statistical analyses
Similarly, males and females of the three test strains were separated by wire mesh in a 4 Ă— 10 m poultry house. The stethoscope was placed on the left side of the breast of the inverted bird after separating the feathers to expose as much skin as possible.
R ESULTS
- Body weight changes
- Physiological responses
- Rectal temperature
- Breathing rate
- Heart rate
Body weight (BW) according to strain and sex of bird for Naked Neck (NN), Ovambo (OV) and Potchefstroom Koekoek (PK) chickens used in the study. Influence of strain and gender of bird on heart rate (HR) in beats/minute (bpm) a, b, x: Heart rates (HR) that differ significantly (P < 0.05) within a specific gender are indicated by different letters (a ) shown , b) for males and (x) for females of different strains.
D ISCUSSION
Evaporative heat loss increases with Ta and decreases with increasing RH (Lin et al., 2010). However, in a study by Yahav et al. no genotype benefit was observed during exposure to temperature cycles.
C ONCLUSIONS
The mean BR range observed in this study is wider but generally lower than the 40 to 60 breaths/min observed in broilers (Nascimento et al., 2012). When the thermal requirements of chickens are not met, heat stress can occur, depending on strain, plumage and feed (Lin et al., 2010).
R EFERENCES
Bare neck and crest genes for the improvement of chickens reared under high ambient temperature: Growth performance and egg production. Heat stress impairs performance parameters, causes intestinal injury and reduces macrophage activity in broilers." Poultry science.
GUT MORPHOLOGY AND HISTOLOGICAL PARAMETERS OF ILEAL MUCOSA IN
I NTRODUCTION
Birds on free-range systems forage on fibrous material of plant origin and insects with a high fiber concentration that improve nutrient digestion and intestinal morphology (Awad et al., 2008). The functional surface area of ​​the intestine is increased by villi and microvilli on cells (Zhang et al., 2015).
M ATERIALS AND M ETHODS
- Animal ethics
- Study site description
- Experiment 1: Effect of feeding provitamin A bio-fortified maize on body weights, gut morphology
- Birds, diet and management
- Laboratory analyses of feeds
- Experiment 2: Effect of strain and sex of bird on gut and ileal villus morphology in NN, OV and
- Bird management
- Brooding, feeding and health management
- Data collection
- Body weight
- Sampling procedure
- Gut and intestinal anatomy
- Statistical analyses
The birds were weighed on a digital scale, euthanized by cervical dislocation and slaughtered by exsanguination. Birds were weighed individually on a digital scale, model UME CCS-150K, S/N: NXC 100020, to determine BW.
R ESULTS
- Experiment 1
Effect of feeding PABM and WM on carcass, carcass, processed weight and ileal villus characteristics.
E XPERIMENT 2
- Strain differences
- Internal organ weights and ileal villus morphology
Interaction effects between diet and bird sex on weight and morphological characteristics of ileal villi. Effect of bird sex on body weight, carcass weight, heart, ventricle, stomach and abdominal fat pad weight.
D ISCUSSION
The absence of differences in AFP yield, in the present study, is consistent with findings of Santos et al. Higher fat yield in females was also observed in the study of Santos et al.
C ONCLUSIONS
It is important to note that there are several key factors that have been inconsistent between studies on the effects of different rearing systems on bird performance (Li et al., 2016), hence the need for more research in this area focusing particularly on the small intestine as changes in its fine morphology absorption rate, weight gain, therefore performance, can change (Rezaian and Hamedi, 2012).
R EFERENCES
Effects of dietary inclusion of probiotics and synbiotics on growth performance, organ weights and intestinal histomorphology of broilers. Effects of different rearing systems on growth performance, carcass and meat quality of medium-growing chickens.
EFFECT OF STRAIN, SEX OF BIRD AND REARING SYSTEM ON DURATION OF
I NTRODUCTION
The duration of tonic immobility (TI), the ratio of heterophils to lymphocytes (H/L) and the weight of lymphoid organs are reliable indicators of stress in chickens (Altan et al., 2003). Animals attacked by predators often enter a state of TI in which individuals appear to simulate death (Edelaar et al., 2012).
M ATERIALS AND M ETHODS
- Animal ethics
- Study site
- Treatments, experimental design and bird management
- Bird management
- Brooding, feeding and health management
- Data collection and measurements
- Tonic immobility
- Heterophil to lymphocyte (H/L) ratio
- Organ weights
- Statistical analyses
Twelve birds were randomly selected per path to represent each of the 3 tribes and both sexes. On the last day of the experiment, all birds were weighed using a digital scale (Jadever JPS-1050, Micro Preciso Calibraton Inc, USA; ±1 g sensitivity).
R ESULTS
- Levels of significance
- Mortality and body weights
- Duration of tonic immobility
- Leucocyte and heterophil to lymphocyte (H/L) ratio
- Organ weights
Effect of bird strain on the duration of tonic immobility (TI) in bareneck (NN), Ovambo (OV) and Potchefsroom Koekoek (PK) chickens. Hens had significantly (P < 0.05) larger spleens than roosters in the PK strain, whereas spleens were heavier in males of the other 2 strains.
D ISCUSSION
TI durations in the current study are shorter than values ​​reported for pheasants (Hrabcakova et al., 2012). The duration of TI was longer in birds housed in deep litter than in free-ranging birds (Campo et al., 2008).
C ONCLUSIONS
Reduced relative spleen weight was observed in heat-exposed broilers in a separate study (Quinteiro-Filho et al., 2010). Tryptophan deficiency is known to reduce productivity in poultry, but supplementation did not significantly reduce relative spleen weight in stressed chickens (Moneva et al., 2008).
R EFERENCES
Tonic immobility is a measure of predator boldness: an application of Bayesian structural equation modeling. Evaluation of tonic immobility in common pheasants kept in different housing systems during the laying period.
EFFECT OF STRAIN, SEX AND REARING SYSTEM ON CARCASS AND FAT YIELD
I NTRODUCTION
M ATERIALS AND M ETHODS
- Animal ethics
- Study site description
- Treatments, experimental design and bird management
- Bird management
- Brooding, feeding and health management
- Data collection
- Statistical analyses
R ESULTS
- Body, carcass and dressed weights
- Portion and giblet weights
D ISCUSSION
C ONCLUSIONS
R EFERENCES
GENERAL DISCUSSION, CONCLUSIONS AND RECOMMENDATIONS
G ENERAL DISCUSSION
C ONCLUSIONS
R ECOMMENDATIONS
R EFERENCES
ETHICAL APPROVAL
LIST OF PUBLICATIONS
