The effect of water intake prior to blood sampling on packed cell volume in sheep

The effect of water intake prior to blood sampling on subsequent packed cell volume (PCV) was investigated in ewe lambs (8 months of age) of the Dohne Merino, Merino and Letelle flocks at Grootfontein Agricultural Development Institute. On the afternoon of the day before the experiment was conducted, a blood sample for a baseline PCV value (R) was taken from each animal. The following day, 15 ewes of each breed (n = 45) were dosed with 1 litre of water and another 15 of each (n = 45) were used as a control. Blood samples for PCV were taken concurrently for both the control and water treatment groups before the dose (0), and at 15, 30 and 60 minutes after dosing. PCV were subsequently determined with the microcapillary centrifuge technique. Baseline PCV of Letelle ewes was higher (32.4 +/- 0.6) than that of the Dohne Merino (29.7 +/- 0.6) and Merino (28.7 +/- 0.6) ewes. Furthermore, recovery rate at 30 minutes after treatment also differed among breeds. Although there were significant differences between the control and water treatment groups at R and 0 minutes, which were probably due to inherent animal differences, there were no significant differences between PCV of the 2 groups during the remainder of the experimental period. Overall it can be concluded that water intake before blood sampling for the determination of PCV has no significant effect on haematocrit. Differences among breeds were more pronounced than those between treatment groups.