The potential for use of haematological and anti-IgE humoral responses as phenotypic markers for tick resistance in cattle.

Approximately 80% of the global cattle population is at risk of infestation and infection by ticks and tick-borne diseases (TTBDs). The economic losses from animal mortality, reduced production, vector control costs and animal treatment are very substantial, hence there is an urgent need to develop and deploy alternative vector control strategies. Breeding for host tick resistance has the potential for sustainable large-scale TTBD control especially in cattle. The gold standard method for phenotyping tick resistance in cattle is by counting ticks on the body but is very laborious and subjective. Better methods for phenotyping tick resistance more objectively, faster and at scale, are essential for selecting host genetic resistance to ticks. This study investigated the correlation between haematological cellular profiles and immunological responses (immunoglobulin E, IgE) and full body tick counts in herds of Bos indicus and Bos taurus following artificial tick challenge with Rhipicephalus decoloratus larvae. Fifty-four Friesian and Ayrshire (Bos taurus) and 52 East African Zebu (Bos indicus) calves were each infested with ∼2500 larvae. Near-replete adult female ticks (≥ 4.5 mm) were counted daily from Day 20-25. Blood and serum samples were obtained from each animal on Days 0 and 23 for cellular blood and IgE titre analysis, respectively. The indicine cattle were refractory to R. decoloratus infestation in comparison with the taurine breed (P < 0.0001). Repeated measurements of blood components pre-infestation revealed a significant (P < 0.05) association with tick count in IgE and red blood cells, haematocrit, and haemoglobin post-infestation. There was also a strong positive correlation between the tick counts and red blood cell numbers, haemoglobin, haematocrit, and IgE concentration (P < 0.0001) following tick challenge. The application of this approach to phenotype host resistance needs to be assessed using higher cattle numbers and with different tick species or genera.

Big opportunities for tiny bugs: rush to boost laying hen performance using black soldier fly larvae meal.

Rising feed cost challenges due to expensive conventional protein sources continue to make headlines in Africa causing drops in profit margins. We assessed the impact of insect (Hermetia illucens Linnaeus larvae meal, HILM) protein as a substitute for soybean meal and sunflower seed cake on layer chicken performance and profitability. Our results showed that apart from the growers, chicks (12.37 g/bird) and layer hens (2.02 g/bird) fed diets with 75% HILM inclusion levels had significantly higher average daily weight gain. The average daily feed intake (ADFI) and feed conversion ratio (FCR) varied significantly when the chicks and layer hens were provided with the HILM-based diets. For the chicks and layer hens, the lowest ADFI and FCR were observed in birds subjected to diets with 75% and 100% HILM compared to the growers fed diets with 50% HILM. Significantly higher egg production was observed for layer hens fed diets containing 75% of HILM throughout the first (87.41%) and second (83.05%) phase production cycles. Layer hens fed HILM-based diets had a 3-10% increase in egg laying percentage. There was higher profit margins when birds were fed diets containing 75% of HILM (~1.83 and 5.98 US$ per bird), which mirrored the return on investment estimated at 63.95% and 33.36% for the pullets (growers) and laying hen, respectively. Our findings demonstrate that diets with 75% HILM provided optimum growth performance, reduced feeding costs, increased weight gain and egg production as well as improved economic returns for commercial on-farm poultry production systems.

Investigating volatile semiochemical production from Bos taurus and Bos indicus as a novel phenotype for breeding host resistance to ixodid ticks.

Ticks and tick-borne diseases cause significant loss in livestock production with about 80% world's cattle at risk. The cost of chemical control is high and there is an ever-increasing tick resistance to chemical acaricides. Genetic selection as alternative long-term control strategy is constrained by laborious phenotyping using tick counts or scores. This study explored the use of host volatile semiochemicals that may be attractants or repellents to ticks as a phenotype for new tick resistance, with potential to be used as a proxy in selection programmes. Approximately 100 young cattle composed of Bos indicus and Bos taurus were artificially infested with 2,500 African blue tick, Rhipicephalus decoloratus larvae, with daily female tick (4.5 mm) counts taken from day 20 post-infestation. Volatile organic compounds were sampled from cattle before and after tick infestation by dynamic headspace collection, analysed by high-resolution gas chromatography (GC) and subjected to multivariate statistical analysis. Using 6-day repeated measure analysis, three pre-infestation GC peaks (BI938 - unknown, BI966 - 6-methyl-5-hepten-2-one and BI995 - hexyl acetate) and one post-infestation GC peak (AI933 - benzaldehyde / (E)-2-heptenal) were associated with tick resistance (P < 0.01 and P < 0.05 respectively). The high correlation coefficients (r = 0.66) between repeated records with all volatile compounds support the potential predictive value for volatile compounds in selective breeding programmes for tick resistance in cattle.