Effect of vegetation density on survival of South African free-ranging indigenous chicken broods.

The survival of juveniles from hatching until recruitment is a critical determinant of indigenous chicken population growth under extensive free-range production systems. A longitudinal study was conducted to investigate the impact of vegetation cover on survival of indigenous chicken broods in Msinga, South Africa. Survival records of 281 chicks hatched in sparsely vegetated (SV) communal lands and 233 hatched chicks in densely vegetated (DV) resettlement areas were collected from hatch until 12 weeks of age. Data on probable cause of death of individual chicks was collected using a structured checklist. Kaplan-Meir survival distributions and log rank tests were used to estimate the survival functions of broods between vegetation cover types. Logistic regression analysis was used to determine the association between management factors and mortality risk in SV and DV. Chick survival from hatching to 12 weeks was higher in SV (55 ± 3.14%) than DV (41 ± 4.19%) (P < 0.05). Mean chick survival time did not differ between SV (56 ± 3.30 days) and DV (49 ± 3.23 days) (P > 0.05). Aerial predators were the major cause of chick mortality (over 60%) followed by terrestrial predators (30%) in both vegetation cover types. The odds of mortality were higher in DV compared to SV (P < 0.05). It was concluded that increasing vegetation cover decreases survival of scavenging chicks between hatching and end of brooding at 12 weeks of age, and therefore brood management actions should ensure adequate protection of free-ranging chicken broods in densely vegetated rearing habitats.

Effects of water restriction on the growth performance, carcass characteristics and organ weights of naked neck and ovambo chickens of southern Africa.

In semi-arid areas of Southern Africa, dehydration can compromise the performance and welfare of local chickens, particularly during the growing period when confinement is curtailed and birds are left to scavenge for feed and water. The effect of water restriction on the growth performance was compared in Naked Neck (NNK) and Ovambo (OVB) chickens that are predominant in Southern Africa. A total of 54 eight-wk-old pullets each of NNK and OVB chickens with an initial average weight of 641±10 g/bird were randomly assigned to three water intake treatments, each having six birds for 8 wk. The water restriction treatments were ad libitum, 70% of ad libitum and 40% of ad libitum intake. Nine experimental pens with a floor space of 3.3 m(2) per strain were used. The pens were housed in an open-sided house with cement floor deep littered with a 20 cm layer of untreated wood shavings. Feed was provided ad libitum. Average daily water intake (ADWI), BW at 16 weeks of age (FBW), ADG, ADFI, feed conversion ratio (FCR) and water to feed ratios (WFR) were determined. Ovambo chickens had superior (p<0.05) FBW, ADG and ADWI than NNK chickens. Body weight of birds at 16 weeks of age, ADG, ADFI, ADWI, and WFR declined progressively (p<0.05) with increasing severity of water restriction while FCR values increased (p<0.05) as the severity of water restriction increased. Naked Neck chickens had better FCR at the 40% of ad libitum water intake level than Ovambo chickens. The dressing percentage per bird was higher in water restricted birds than those on ad libitum water consumption, irrespective of strain. Heart weight was significantly lower in birds on 40% of ad libitum water intake than those on ad libitum and 70% of ad libitum water intake, respectively. In conclusion, NNK chickens performed better than OVB chickens under conditions of water restriction and would be ideal to raise for meat and egg production in locations where water shortages are a major challenge.

Physicochemical properties of breast meat from water-stressed naked-neck and Ovambo chickens.

1. Differences in growth performance, physicochemical properties and fatty acid composition of breast muscle from water-stressed 16-week-old naked-neck (NNK) and Ovambo (OVB) chickens were investigated. 2. OVB chickens had superior (P < 0.05) slaughter weights at 16 weeks of age, average daily gain (ADG) and average daily water intake (ADWI) than NNK chickens. Body weights of birds at 16 weeks of age, ADG, average daily feed intake (ADFI), ADWI and water to feed ratio (WFR) declined progressively with increasing severity of water restriction while the opposite was observed for feed conversion ratio (FCR) values. NNK chickens had better FCR at the 40% of ad libitum water intake than OVB chickens. 3. Meat from NNK chickens had higher redness (a*) values at the 40% of ad libitum water intake but lower lightness (L*) and yellowness (b*) values at 70% of ad libitum and ad libitum water intakes compared with OVB chickens. 4. There was no interaction between strain and water intake on most fatty acids, except for the proportion of elaidic acid (C18:1t9) higher in meat from NNK compared with OVB chickens given water at 40% of ad libitum. Water restriction to 40% of ad libitum water intake had a positive influence on the proportions of linoleic acid (C18:2n-6), arachidonic acid (C20:4n-6), adrenic acid (C22:4n-6), docosahexaenoic acid (C22:6n-3), total polyunsaturated fatty acid (PUFA), total omega-3 PUFA and total omega-6 PUFA proportions, but resulted in lower proportions of total monounsaturated fatty acids (MUFAs) compared with 70% of ad libitum and ad libitum water intakes. 5. It was concluded that cooking loss, meat redness values, omega-3 and omega-6 PUFA proportions and n-6/n-3 ratio of NNK chickens improved with increasing severity of water restriction compared with OVB chickens.

Haematological and serum biochemical responses of chickens to hydric stress.

Dehydration can be extremely damaging to the performance and welfare of indigenous chickens. The effect of water restriction on haematological and biochemical parameters was compared in Naked Neck (NNK) and Ovambo (OVB) chickens. A total of 54 8-week-old pullets each of NNK and OVB chickens with an initial average weight of 641 ± 10 g/bird were randomly assigned to three water intake treatments with three replications, each having six birds. The water restriction treatments were ad libitum, 70% and 40% of ad libitum intake. Nine experimental pens with a floor space of 3.3 m2 per strain were used. Feed was provided ad libitum. Packed cell volume (PCV), erythrocyte count (RBC), mean corpuscular volume (MCV) and total leucocyte count (WBC), and biochemical parameters (uric acid (UA)), creatinine (CREAT), total protein (TP), albumin (ALB), globulin (GLOB), triglyceride (TGA), total cholesterol (TC), high- (HDLC) and low- (LDLC) density lipoprotein cholesterol and activity of alanine transaminase (ALT), alkaline phosphatase (ALP) and aspartate transaminase (AST) were determined from blood collected after 60 days of water restriction. PCV was higher (P < 0.05) in NNK than OVB chickens offered water ad libitum, but similar in birds offered 70% and 40% of ad libitum. There were no differences in RBC and MCV values between strains, but MCV was higher in birds on 40% than 70% of ad libitum water intake, irrespective of strain. Naked neck chickens had higher (P < 0.05) WBC values than OVB at 40% restriction level, but lower WBC than OVB at 70% water restriction level. UA, CREAT, TGA, TC, LDLC, TP and GLOB increased (P < 0.05) with each increment in water restriction, but the increase in CREAT and TC was more pronounced in OVB than NNK chickens. The opposite was observed for UA. ALT activity indicated that liver function was not affected by water restriction. It was concluded that the two strains can withstand up to 40% of ad libitum water restriction, but NNK tolerated water stress better than OVB chickens.