The use of faecal Na concentration as an indicator of Na status in lactating crossbred cows.
Khalili M. | Varvikko T. | Lindgren E.
An experiment was carried out with four rumen fistulated crossbred Friesian x Zebu lactating cows to evaluate the Na content of faeces as an indicator of Na status in cattle. In addition, the effect of NaCl supplementation on the animal performance and rumen parameters was examined. The cows were fed a basal diet of oat-vetch hay and concentrate containing low Na. The diets were supplemented as follows; Diet 1, no supplement (low barley, low Na); Diet 2, 3 g NaCl kg total dietary DM-1 (low barley adequate Na); Diet 3, 3.0 kg barley (high barley, low Na) and Diet 4, 3.0 kg barley and 3.0 g NaCl total dietary DM-1 (high barley, adequate Na). Intake significantly (p less than 0.01) increased after NaCl supplementation when high barley was fed. Provision of NaCl significantly (p less than 0.05) increased milk production. High consumption of barley also significantly (p less than 0.01) increased milk production irrespective of NaCl. Increased barley consumption significantly (p less than 0.05) decreased rumen fluid pH. The concentration of Na in the rumen fluid pH. The concentration of Na in the rumen fluid supernatant significantly (p less than 0.05) decreased on low Na diets, and the concentration of K increased (p less than 0.05). The concentration of Na in blood plasma did not change following the NaCl supplementation. Faecal Na and Na/K ratios were significantly (p less than 0.01) lower on the low Na than on the NaCl supplemented diets. There was no variation in Na and Na/K ratios in faecal samples collected at 0, 3, 6 and 8 h after the morning feed on two consecutive days. Faecal Na on the low Na diets were below the critical level of 1 g kg DM-1. It would appear that the determination of Na in grab samples of faeces is a practical procedure for determining the Na status of cattle.
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