Jones W. Ngambi

Genetic parameter estimates for body weight in local Venda chickens

Genetic parameters were estimated for Venda chicken body weights at hatching, and at 4 weeks, 10 weeks and 21 weeks of age. A single-trait animal model with restricted maximum-likelihood procedures was used. Random effects were additive direct and maternal genetic, common environmental and error. The heritability estimates for direct effects were 0.36, 0.25, 0.41 and 0.22 for hatch, 4 weeks, 10 weeks and 21 weeks, respectively. The maternal effects were estimated at hatch and 4 weeks of age and were not present at later ages. Common environmental effects disappeared with increasing age. There was an antagonistic relationship between direct and maternal effects. The results show potential for genetic improvement of indigenous Venda chickens through selection. Maternal effects should be considered if selection is carried out at early ages.

Productivity of Angora goats in the communal rangelands of Molimo-Nthuse area in Lesotho

Production parameters were determined for kidding, offtake and mortality rates, and milk production and composition of Angora goats in two communal agro-ecological zones, Mountains and Lowlands, of Molimo-nthuse area in Lesotho. True incidence rates and risk rates as used in dynamic populations were used to calculate the different production parameters. A completely randomized design was used to compare the differences between the two agro-ecological zones. Angora goats in the two agro-ecological zones produced milk similarly (p > 0.05) in amounts and composition. There were no significant (p > 0.05) differences in annual kidding, mortality and offtake rates between Angora goats kept in the Lowlands and those in the Mountains. However, high mortality rates and mortality risk rates were observed in both zones. Thus, the risk rates that suckling Angora goats would die within their first 6 months after birth were 28% and 34% for the Mountains and Lowlands, respectively. It is suggested that future emphasis should be on reducing kid mortality through better herding of the goats and improvement of pre- and post-partum nutrition of the doe in this communal livestock farming system.

Growth and haematological response of indigenous Venda chickens aged 8 to 13 weeks to varying dietary lysine to energy ratios

The effect of feeding varying dietary lysine to energy levels on growth and haematological values of indigenous Venda chickens aged 8 - 13 weeks was evaluated. Four hundred and twenty Venda chickens (BW 362 ± 10 g) were allocated to four dietary treatments in a completely randomized design. Each treatment was replicated seven times, and each replicate had fifteen chickens. Four maize-soya beans-based diets were formulated. Each diet had similar CP (150 g/kg DM) and lysine (8 g lysine/kg DM) but varying energy levels (11, 12, 13 and 14 MJ ME/kg DM). The birds were reared in a deep litter house; feed and water were provided ad libitum. Data on growth and haematological values were collected and analysed using one-way analysis of variance. Duncans test for multiple comparisons was used to test the significant difference between treatment means (p < 0.05). A quadratic equation was used to determine dietary lysine to energy ratios for optimum parameters which were significant difference. Results showed that dietary energy level influenced (p < 0.05) feed intake, feed conversion ratio, live weight, haemoglobin and pack cell volume values of chickens. Dry matter digestibility, metabolizable energy and nitrogen retention not influenced by dietary lysine to energy ratio. Also, white blood cell, red blood cell, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration in female Venda chickens aged 91 days were not influenced by dietary lysine to energy ratio. It is concluded that dietary lysine to energy ratios of 0.672, 0.646, 0.639 and 0.649 optimized feed intake, growth rate, FCR and live weight in indigenous female Venda chickens fed diets containing 8 g of lysine/kg DM, 150 g of CP/kg DM and 11 MJ of ME/kg DM. This has implications in diet formulation for indigenous female Venda chickens.

Breed and Sex Differences in the Gross Anatomy, Digesta pH and Histomorphology of the Gastrointestinal Tract of Gallus Gallus Domesticus

ABSTRACT A study was conducted to investigate the influence of breed and sex in the gross anatomy, digesta and histology of Ross 308 broiler and Venda chickens. Chickens were slaughtered at 90 days of age and the pH of the digestive organs was measured immediately after slaughter. The digestive organ weights and lengths of Ross 308 broiler and Venda chickens were measured. Tissue samples of the duodenum, ileum and jejunal from each treatment group were collected and histologically examined. Higher (p<0.05) gizzard pH values were observed in male and female of Ross 308 broiler and Venda chickens. The jejunal and ileal pH values were lower (p<0.05) for Venda chickens than in Ross 308 broiler chickens. The absolute weights of the gastrointestinal tract, crop, proventriculus and gizzard were lighter (p<0.05) in Venda chickens than in Ross 308 broiler chickens. The relative organ weights of the GIT, proventriculus, gizzard and caeca were higher (p<0.05) in Venda chickens than in Ross 308 broiler chickens aged 90 days. Male chickens had higher (p<0.05) relative organ weights than female chickens. Interactions between breed and sex influenced (p<0.05) the absolute weights of the crop, proventriculus, caeca and large intestine. Ileum villus heights of female Venda chickens were higher (p<0.05) than those of female and male Ross 308 broiler and Venda chickens. The male and female Ross 308 broiler chickens had higher (p<0.05) ileum and duodenum crypt depths than male and female Venda chickens. The duodenum and ileum villus height/crypt depth ratios were higher (p<0.05) in male and female Venda chickens than Ross 308 broiler chickens. In overall, male broiler chicken performed better.

Morphological differentiation of indigenous goats in different agro-ecological zones of Vhembe district, Limpopo province, South Africa

The study was carried out to differentiate indigenous female goats in different agro-ecological zones based on their morphological traits. 551 mature female goats from semi-arid, dry sub-humid and humid agro-ecological zones were considered in this study. The morphological traits analysed were Body Weight, Body Length, Shoulder Height, Hip Height and Heart Girth. Stepwise discriminant analysis was used to check the discriminating power of the variables. Canonical discriminant procedure was applied to determine differences between indigenous goats in different zones. The analysis showed that all the variables measured have discriminating power. In canonical discriminant analysis, the first canonical variable determined was significant and accounted for 91.87% of the variation, but the second canonical variable was not significant and accounted 8.13% of the variation. The pairwise Mahalanobis distances between indigenous goats in semi-arid and dry sub-humid as well as between semi-arid and humid were significant. The pairwise distance between goats in dry sub-humid and humid was not significant. Discriminant model function correctly allocated 60.31% (semi-arid), 58.06% (humid) and 38.46% (dry subhumid) of indigenous goats into their original agro-ecological zone.

Effect of pre-weaning selection on estimates of genetic parameters and breeding values for post-weaning growth rate of beef bulls on test.

Data on South African Angus cattle consisting of 45 259 records on weaning weight (WWT), 4 360 records on average daily gain from on-farm test (ADG-D) and 1 118 from centralized test (ADG-C) were analyzed to evaluate the effect of pre-weaning selection on estimates of genetic parameters and subsequent estimated breeding values (EBV) for post-weaning average daily gain. (Co)variance components and genetic parameters for weaning weight (WWT), ADG-C and ADG-D were estimated by REML procedures fitting three different animal models. Model 1 was a univariate model of WWT, ADG-C or ADG-D and did not account for the effect of pre-weaning selection on post-weaning ADG. Model 2 was a two-trait model of WWT and either ADG-C or ADG-D. Model 3 was a multi-trait animal model including WWT, ADG-C and ADG-D. Estimates of heritability for ADG-C were 0.39 ± 0.080, 0.42 ± 0.060 and 0.44 ± 0.010 from Model 1, 2 and 3 respectively. Corresponding estimates for ADG-D were 0.18 ± 0.020, 0.19 ± 0.020 and 0.21 ± 0.020 respectively. Rank correlations based on EBVs for ADG-C for all bulls were 0.92, 0.83 and 0.94 for Model 1 vs. Model 2, Model 1 vs. Model 3, and Model 2 vs. Model 3, respectively and they indicated a possible re-ranking of bulls when including or excluding a correlated pre-weaning trait. Rank correlations for ADG-D also followed a similar trend. Inclusion of pre-weaning information in genetic analysis for post-weaning average daily gain is necessary to account for selection at weaning.