Effects of sodium chloride on sheep. 2. Voluntary feed intake and changes in certain rumen parameters of young Merino wethers g

摘要

While grazing native pasture, seven groups of 4 young Merino wethers received the following supplements daily via rumen cannulae: 0, 5 (Control), 15 and 30 g salt (NaCl); and 5, 15 and 30 g NaCl + 20 g crude protein (CP) each. There was a non-significant (P ≤ 0,05) tendency for digestible organic matter (DOM) intake to decrease with incremental levels of NaCl and to increase with CP supplementation (33,8; 34,5; 31,5; 31,3; 35,5; 35,8 and 31,3 g DOM / Wkg0.75 day-1). Although only some of the differences were significant (P ≤ 0,05), rumen pH tended to decrease with incremental levels of NaCl, as well as with CP supplementation (6,64; 6,58; 6,51; 6,59; 6,45; 6,51 and 6;25). CP supplementation had a significant (P ≤ 0,05) elevating effect and incremental levels of NaCl a non-significant (P ≤ 0,05) elevating effect on rumen NH3 (4,72; 3,44; 3,51; 4,71; 7,74; 10,14 and 8,22 mg NH3/ 100 ml rumen fluid). Volatile fatty acids (VFA) were, besides significant (P ≤ 0,05) differences in acetic acid between a few treatments, apparently not affected to any real extent by either NaCI or CP supplementation and the overall pattern of VFA proportions remained similar for all groups with an approximate ratio of 76:15:9. The tendency for CP to reduce ruminal Na was not significant (P ≤ 0,05), whereas the wethers receiving 0 g NaCl had a significantly (P ≤ 0,05) lower rumen Na concentration (1,367; 2,385; 2,876; 2,632; 1,674; 2,458 and 2,293 g Na 1-1). The wethers receiving 0g NaCl had a significantly (P ≤ 0,05) elevated ruminal K concentration (2,821; 0,715; 1,031; 1,027; 0,747; 1,064 en 0,995 g K I-1 ). Diurnal variations in rumen indices are also discussed. It is suggested that Na and K imbalances in the extra- and intra-cellular body fluid compartments, increased the maintenance energy expenditure of the wethers, thereby inducing the deleterious effects on production parameters.