Effect of zeolite A on rumen fermentation and phosphorus metabolism in dairy cows

Abstract

The aim of the present study was to determine the effect of zeolite A on several physiological parameters and on mineral metabolism in the rumino-intestinal-tract of cows. Eight double fistulated (rumen and proximal duodenum) cows were fed maize silage, grass silage and concentrate. Zeolite A was added to the ration over a period of three weeks at 0, 10 and 20 g/kg dry matter (DM). The daily feed amounts were adjusted to the current performance and varied between 3.9 and 15.5 kg/d. Rumen fluid, duodenal chyme and faeces were sampled to characterise the nutrient digestibility. Blood samples were taken to analyse the concentration of inorganic phosphate. Zeolite A supplementation led to a significantly reduced ruminal DM digestibility and fermentation of organic matter. The molar proportion of acetate in the rumen increased, and propionate as well as valerate decreased significantly after zeolite A supplementation. The concentration of the total fatty acids and ruminal pH were not affected. No effect on faecal digestion of DM, organic matter nor on calcium and magnesium digestion was observed. Otherwise the phosphorus (P) concentration in rumen fluid correlated negatively with the mean zeolite A intake (r (2) = 0.75; p = 0.0003). Further, the faecal excretion of P increased significantly for cows with the highest zeolite A dosage (36.9 g P/d) compared to the control group (29.9 g P/d). The lower digestibility of P resulted in a significantly decreased concentration of inorganic P in serum from a basal value of 2.05-1.16 mmol/l six days after starting zeolite A supplementation. The zeolite A treated cows showed a significantly higher Al concentration already in rumen fluid (14.31 and 13.84 mmol/l) compared to the control cows (6.33 mmol/l). The Al flow in the duodenum was also higher for zeolite A treated cows.

Effects of In-Feed Inclusion of Clinoptilolite on Blood Serum Concentrations of Aluminium and Inorganic Phosphorus and on Ruminal Ph and Volatile Fatty Acid Concentrations in Dairy Cows

“…This is confirmed by the results of previous studies in ruminants where no significant effect of clinoptilolite on blood serum P was recorded [5,20,23,24]. On the contrary, the supplementation of synthetic zeolite A seems to have a negative effect on phosphorus metabolism, which is reflected in the low-serum P concentration [9,[25][26][27].…”

“…The exact mechanism by which clinoptilolite might affect the molar proportion of volatile fatty acids in rumen is currently unknown and needs further investigation. Similar alterations of the molar proportions of the volatile fatty acids have been recorded in previous experiments as well [9,17,18], but other researchers observed that clinoptilolite increased the proportion of propionate [15,16]. However, in the latter experiments clinoptilolite was added to high-concentrate diets and not at high-roughage diets as at the present study.…”

“…If a considerable amount of clinoptilolite is hydrolyzed, the released aluminium (Al) may interfere with the utilization of several minerals, with phosphorus absorption and metabolism being the most affected [8]. Although this hypothesis has not been tested yet for natural zeolites, some researchers recently found increased levels of Al in the rumen of cows that were receiving synthetic zeolite A, indicating that synthetic zeolites are hydrolyzed even in rumen [9]. Moreover, they observed reduced bioavailability of dietary phosphorus and significantly lower blood serum phosphorus in cows that were fed zeolite A [10].…”

“…However, the changes on the proportion of volatile fatty acids are not constant. In some studies it is concluded that zeolites increase the proportion of propionate [15,16], and in others, decrease the proportion of propionate [17,18] and valerate [9], and increase that of acetate [9,17].…”

“…Average (mean ± SE) ruminal pH values in rumen fluid samples that were obtained at weekly intervals for 12 weeks (rumen fluid collection time,[1][2][3][4][5][6][7][8][9][10][11][12], from the eight cows of group A that received a ration supplemented with 200 g of clinoptilolite per day and the eight cows of group B that were left untreated as controls Average (mean ± SE) total volatile fatty acid concentrations (mmol/L) and molar proportions of acetate, propionate and valerate (%) in rumen fluid samples that were obtained at weekly intervals for 12 weeks (rumen fluid collection time,[1][2][3][4][5][6][7][8][9][10][11][12], from the eight cows of group A that received a ration supplemented with 200 g of clinoptilolite per day and the eight cows of group B that were left untreated as controls…”