Agroscope, Institute for Plant Production Sciences IPS, 1260 Nyon, Switzerland

Roughage to concentrate ratio and salt supply in ruminants

In two balance trials with 15 and 16 lactating Saanen goats (model animal for cows), the effects of different sodium cloride (NaCl) supplies and roughage to concentrate ratios on performance and metabolism were investigated. The NaCl supply levels ranged from 100 to 200 and 300 % of Swiss recommendations (RAP, 1999). The tested roughage to concentrate ratios were 50:50 and 80:20. The following parameters were recorded: feed intake, water consumption, milk performance, milk contents, nutrient and mineral balance completed with metabolic profile and salivary Na and K concentrations.<br>The NaCl oversupply had no negative effects neither on feed intake nor on milk performance or milk composition. On the other hand, digestibility of main nutrients was slightly reduced although the majority of the observed differences did not reach a significant level. Goats offered a NaCl supply exceeding feeding standards excreted significantly more urinary Na (Ø 50 %) in relation to Na intake than goats fed the recommended NaCl quantity (Ø 27 %). The latter group, however, had a higher fecal Na excretion (Ø 33 % compared to 26 %). Thus, Na retention did not significantly differ between treatments. Cl retention was negative for most goats independent of the NaCl supply level. The extent of the negative Cl retention is greater in high roughage diets (-9 % in relation to Cl intake) compared to the lower roughage ratio (-4.3 %). The varying NaCl supplies and roughage to concentrate ratios did not modify blood and salivary parameters in a biologically relevant way.

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