D. Norris

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.

ESTIMATION OF GENETIC PARAMETERS AND VARIANCE COMPONENTS FOR GROWTH TRAITS OF NGUNI CATTLE IN LIMPOPO PROVINCE, SOUTH AFRICA

Estimates of (co)variance and genetic parameters of birth, weaning (205 days) and yearling (365 days) weight were obtained using single-trait animal models. The data were analysed by restricted maximum likelihood, fitting an animal model that included direct and maternal genetic and permanent environmental effects. The data included records collected between 1976 and 2001. The pedigree information extended as far back as early 1960s. The heritabilities for direct effects of birth, weaning and yearling weights were 0.36, 0.29 and 0.25, respectively. Heritability estimates for maternal effects were 0.13, 0.16 and 0.15 for birth, weaning and yearling weights, respectively. The correlations between direct and maternal additive genetic effects were negative for all traits analysed. The results indicate that both direct and maternal effects should be included in a selection programme for all the traits analysed.

Effects of genetic and environmental factors on pre-weaning and post-weaning growth in West African crossbred sheep

Effects of genetic and environmental factors on pre-weaning and post-weaning growth were studied in West African crossbred sheep. Effects of lamb genotype (7/8 Sahelian–1/8 Djallonké, 3/4 Sahelian–1/4 Djallonké and 1/2 Sahelian–1/2 Djallonké; hereafter denoted 7/8Sa, 3/4Sa and 1/2Sa, respectively), parity, type of birth, sex of lamb and year-season of lambing on birth weight, weaning weight, 8-month weight and pre- and post-weaning growth rates were determined. At birth 7/8Sa and 3/4Sa lambs were heavier (p < 0.01) than 1/2Sa lambs. Lambs born to first-parity ewes were lighter (p < 0.01) at birth than lambs of older ewes. At weaning and 8 months of age, lambs born to fourth-parity ewes were heavier (p < 0.05) than those born to ewes of the other parities. Parity did not have any significant effects on pre-weaning growth rate. Lambs born in the rainy season of 2001 were significantly heavier at birth and at 8 months of age than those born in the dry season of 2001/02, but there was no difference between the two groups at weaning. Pre-weaning growth rate was significantly faster in lambs born in the dry season of 2001/02 but the reverse was true for post-weaning growth rate.

Relationships between Longevity and Linear Type Traits in Holstein Cattle Population of Southern Africa

Relationships between longevity and linear type traits were estimated using data on 34 201 cows with lifetime information and linear type scores. The longevity trait considered was the number of lactations initiated and the linear type traits were rump height, body depth, angularity, rear udder height, fore udder attachment, udder depth, fore teat placement and fore teat length. Fixed effects included in the models were herd year, season of calving and herd–date of classification–classifier and days in milk. Age at first calving and age at classification were included as linear and quadratic covariates. Heritability estimates were low for longevity and moderate for most type traits except rump height and fore teat length. All the phenotypic correlations between longevity and the linear type traits were slightly positive (0.01 to 0.09) except the relationships with rump height and fore teat length which were –0.01 and –0.02, respectively. Genetic correlations between longevity and udder traits as well as angularity were moderate to high and positive (0.22 to 0.48). The only notable negative genetic correlations were longevity with body depth and fore teat length (–0.15 and –0.07, respectively). The genetic correlations suggest that selection for udder traits and angularity should improve longevity in the Holstein cattle population.

Effects of stocking density and group size on the performance of white and brown Hyline layers in semi-arid conditions

The effect of housing two Hyline strains of commercial laying hens White Hyline (W-98) and Brown Hyline (Hyline Brown) at densities of 2, 3 or 4 per cage (1100, 733 or 550 cm2/hen, respectively) was investigated over 3 months. Hyline Brown layers gained more weight, laid more but lighter eggs, utilized feed more efficiently and had a lower mortality than W-98 layers. Housing birds 2 or 3 per cage resulted in greater body weight gain, higher egg production, heavier eggs, better feed conversion ratio and a lower mortality than housing them 4 per cage. There were significant interactions between strain and stocking density for egg production, egg weight, egg output and mortality. It is suggested that for egg production in semi-arid areas Hyline Brown hens could be used and housed at a density of 733 cm2/hen.

Effect of dietary lysine to crude protein ratio on performance of male Ross 308 broiler chickens

Two experiments were conducted to determine the effect of dietary lysine to crude protein ratio on performance of male Ross 308 broiler chickens. In each experiment the diets were isocaloric and isonitrogenous but with different lysine to crude protein ratios. A complete randomized design was used in both experiments, the starter (1–21 days) and grower (22–42 days) experiments. The three starter diets, based on lysine to crude protein ratios, were L0 (0.055), L1 (0.066) and L2 (0.077), while grower diets were L3(0.047), L4(0.061) and L5(0.074). A quadratic type equation was used to determine ratios for optimum growth rate, feed conversion ratio, breast meat yield and breast meat nitrogen content. Dietary lysine to crude protein ratios of 0.066 and 0.077 supported optimum growth rate and feed conversion ratio, respectively, during the starter period. Dietary lysine to crude protein ratios of 0.073, 0.073, 0.069 and 0.079 supported optimum growth rate, feed conversion and breast meat yield and nitrogen content during the grower phase. Dietary lysine to crude protein ratio had no effect on diet intake and digestibility. The results indicate that at each phase a single dietary lysine to crude protein optimized both growth rate and feed conversion ratio. However, the ratio for optimum breast meat yield was lower than that for optimum growth rate and feed conversion ratio. These findings have implications on ration formulation for broiler chickens.

Determinants of livestock farmers’ perception of future droughts and adoption of mitigating plans

Purpose – The purpose of this paper was to determine if there is an association between farmers’ socio-economic profile and their perception of climate change and related events (drought). Understanding of farmers’ perceptions of drought and climate change may assist in informing policy decisions and development of appropriate intervention strategies. Design/methodology/approach – Discriminant analysis was used to assess the relative importance of the discriminating characteristics (socio-economic characteristics) through the utilization of the weights of the discriminant function. Findings – Age, education, literacy level, farm type, location and gender were important predictors of how farmers perceive climate change and drought phenomena. Originality/value – Most of the studies carried out in the study area were largely descriptive and did not find the association between farmer socio-economic profiles and how they perceive climate change and drought events. This paper also uses discriminant analysis wh...

Effects of Different Levels of Coriander (Coriandrum sativum) Seed Powder and Extract on Serum Biochemical Parameters, Microbiota, and Immunity in Broiler Chicks

The use of herbs and spices has gained increasing interest as feed additives and possible alternative to antibiotics in poultry production. The effects of using different levels of coriander seed powder or extract on selected blood parameters, intestinal microflora, and immune response of broiler chickens were investigated in this study. A total of 420-day-old broiler chicks were randomly assigned to 7 treatments with 4 replicates and fed for 42 days. Results showed that inclusion of 2.0% coriander powder in broiler diets lowered total cholesterol while blood urea was significantly higher in birds on T4 compared to T1 and T2. Furthermore, there were no treatment effects on Lactobacillus bacteria; however, the population of E. coli was significantly higher in the ileum of chickens fed T0. Noticeable significant improvements of antibody titer against Newcastle, infectious bronchitis, and infectious bursal disease were observed in birds receiving coriander extract in water. Immunoglobulin G antibody against sheep red blood cells showed significant improvement in birds fed T3; likewise, immunoglobulin M was significantly higher in birds on T2 and T3 at 28 d of age. These results revealed that coriander extract or powder can be used as antibiotic alternative in broiler feeds.

Effect of ascorbic acid supplementation level to diets of indigenous Venda hens on egg production, hatchability and subsequent productivity of chicks

An experiment was conducted to determine the effect of ascorbic acid supplementation level to the diets of indigenous Venda hens on egg production, hatchability and subsequent productivity of the chicks. The first part of the study determined the effect of ascorbic acid supplementation level to the diets of Venda hens on feed intake, egg production, egg weight, egg content, hatchability and chick hatch-weight. Seventy five Venda hens were randomly assigned to five dietary ascorbic acid treatment levels with three replications, each having five hens. A complete randomized design was used. The treatments were A 0 (0 ascorbic acid/kg DM feed), A 200 (200 mg ascorbic acid/kg DM feed), A 500 (500 mg ascorbic acid/kg DM feed), A 1000 (1000 mg ascorbic acid/kg DM feed), A 1500 (1500 mg ascorbic acid/kg DM feed). Ascorbic acid supplementation to the diets of indigenous Venda hens improved (P 0.05) on diet digestibility, metabolisable energy, nitrogen retention and mortality of their chickens. These results have implications on ration formulation for indigenous Venda hens. Keywords: Indigenous Venda chickens, ascorbic acid supplementation, optimum feed intake, feed conversion ratio, growth rate, live weight, mortalit

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.