Variations in packed cell volume among Gambian cattle: Assessment of biological and environmental determinants in free-range systems.

The use of packed cell volume (PCV) to monitor health status of cattle is widely known but this prognostic approach can be complex to interpret due to several factors affecting its values. This research therefore aims to explain variations in PCV values with focus on the biological and environmental fixed determinants that would assist veterinary practitioners and scientists in better understanding of such information, especially in the free-range cattle husbandry systems. A total of 921 blood samples covering three cattle genotypes were collected from almost the entire length of The Gambia for PCV analysis by the microhaematocrit technique and then, trypanosomosis diagnosis based on microscopy. The data were analysed using general linear model with the univariate procedure. Further, pairwise comparisons of estimated marginal means were conducted using least significant difference option. Standard errors of means, 95 % confidence intervals, and also descriptive statistics were presented. The overall mean of PCV was 26.6 %, with the minimum and maximum values as 12.0 and 44.0 %, respectively. Trypanosomosis status, sex, age, body condition, feeding type, region of sampling, season of sampling, and region × season interaction are determinants with statistically significant (P < 0.05) effect on PCV. However, there was no significant effect (P > 0.05) of coat colour and genotype on PCV. Considering the observed trypanosome-induced complexity, the effect of trypanosomosis progression on PCV variation requires further investigation. This study demonstrates that there are many determinants that should be carefully considered in routine screening, interpretation, and determination of cattle health status based on PCV.