The physiological and metabolic effects of stressors associated with long duration transportation on male Bos indicus cattle

A series of experiments were conducted to examine the effect of stressors associated with long duration transportation, particularly feed and water deprivation, on male Bos indicus cattle. In experiment 1, the effects of feed and water deprivation on microbial counts and rumen kinetics of Bos indicus steers were examined. Cannulated steers (n=4) were either deprived (deprived steers) for 72 hours or had ad libitum access (control steers) to feed and water in a 2 x 4 cross-over design. Rumen fluid was collected at day -6, 0, 4 and 9. Feed and water deprivation occurred from day -3 to day 0. Feed and water deprivation caused decreases in the numbers of cellulolytic bacteria (1.4 v 0.4 cfu x 10⁶ /mL; P = 0.001), live (23.7 v 0.8 x 10⁹/mL; P = 0.001), dead (12.7 v 0.5 x 10⁹/mL; P = 0.001) and total bacterial counts (36.4 v 1.4 x 10⁹/mL; P = 0.001) at day 0, compared with the control steers. However, the deprived steers had greater numbers of cellulolytic bacteria (2.7 v 50.1 cfu x 10⁶ /mL; P = 0.001), live (18.3 v 42.2 x 10⁹/mL; P = 0.001), dead (6. 5 v 19.1 x 10⁹/mL; P = 0.001) and total bacterial counts (24.8 v 61.3 x 10⁹/mL; P = 0.001) from rumen fluid on day 4, compared with the control steers. The numbers of total protozoa in rumen fluid from the deprived steers were less than (551.2 v 2.4 x 10³/mL; P = 0.001) the control steers on day 0. However, the deprived steers had fewer protozoa in rumen fluid than the control treatment on day 4 (P = 0.001) and day 9 (P = 0.001). The concentrations of acetic, butyric, propionic and total VFA in rumen fluid from steers deprived of feed and water were less than the concentrations found in the control steers on day 0 (P = 0.001). The concentrations of VFA from deprived steers were not different to the concentrations of the same VFAs from the control steers at day 4 and 9. There were no differences between control and treatment groups for in vitro gas production (GP) on day -6. The cumulative in vitro GP from the control steers was greater than the deprived steers (P = 0.001) on day 0. However, the in vitro GP was not different for the following incubations on day 4 and 9. These results indicate that feed and water deprivation would have a negative but transient effect on the rumen kinetics of Bos indicus steers. Furthermore, these results would suggest that between one and four days after re-feeding the rumen environment returns to pre-deprivation functionality. The results from experiment one led to the development of a second hypothesis; that treatment of Bos indicus bulls with fresh rumen fluid immediately after transportation would assist in returning the rumen to pre-stress functionality and therefore increase dry matter intake and glycogen concentration in the muscle. In this second experiment, twelve Bos indicus bulls were allocated to one of two treatment groups: rumen transfaunation (n = 6) given 10 kg of rumen fluid after transport or Control (n = 6), given 10 kg of deionised water after transport. Glycogen concentrations of the M semimembranosus, M. semitendinosis and M. Longisimus dorsi were measured before transport on day -7 and after transport on day 0, day 1, day 4 and day 9. Feed intake, liveweight gain, plasma metabolites and electrolytes were recorded on the sampling days. Rumen fluid transfaunation increased the dry matter intake of treated bulls compared to the bulls treated with deionised water. However, rumen transfaunation had no effect on glycogen concentrations of the M. semimembranosus, M. semitendinosus and M. Longisimus dorsi compared to the bulls treated with deionised water in this study. The M. semimembranosus and the M. semitendinosus decreased in glycogen concentration immediately after transport on day 0 but replete to pre–transportation concentrations within 1 day. However, the M. Longisimus dorsi demonstrated no change in glycogen concentration between the pre-transportation sample on day -7 and day 0 or day 1 after transportation. The M. Longisimus dorsi of the bulls increased in glycogen concentration between day 1 and day 4 after transportation. The bulls in this experiment demonstrated that muscle glycogen, as measured at the M. longissimus dorsi, cannot recover to sufficient concentrations (40 to 45 μmol of glycogen concentration per gram muscle) to ensure normal meat quality until between one and four days of rest when feeding Rhodes grass hay ad libitum.