Foraging patterns and volatile fatty acid production levels from the Boran and Nguni cows in drought-stricken arid rangelands

The objective of this study was to determine the effect of breed and parity on plant selection patterns and volatile fatty acid production levels from the Boran and Nguni cows grazing arid rangelands. A total of 24 cows (12 from each breed) were randomly selected for the study and were identified according to their parities (P1 −4). Faecal samples were collected through rectal grabs for 6 consecutive days once a month, and rumen liquor samples every fortnight for 12 months using a stomach tube. A total of 11 herbaceous and 8 browse forage plant species were positively identified from the faecal samples of all the cows. Boran cows produced higher (P < 0.05) pooled averages of acetic (48.5 ± 5.81 mM), propionic (16.3 ± 1.81 mM) and butyric acid (10.7 ± 1.46 mM). Parity significantly influenced volatile fatty acid (VFAs) production (P < 0.05). Nguni cows produced higher (P < 0.05) concentrations of iso-butyric, iso-valeric and valeric acid. The higher molar concentrations of VFAs in Boran support that the breed is capable of mobilizing fat when the need arises, while in Nguni cows VFAs are an adaptive behaviour modification towards the lower nutritional status of rangeland plants. The VFAs are a clue to enteric methane production; hence, we recommend proxy evaluations based on our results.