Fecal Ammonium in mice with CKD: gastrointestinal sequestration by SZC

Background: Urinary Ammonium (NH₄⁺) excretion is decreased in CKD but very little is known about fecal NH₄⁺excretion. Sodium Zirconium Cyclosilicate (SZC) is a cation-exchanger that selectively captures K⁺ in the gastrointestinal tract. We investigated if SZC can sequester NH₄⁺ in vivo and evaluated the effect of SZC on fecal NH₄⁺ in a mouse model of CKD. Methods: Mice with CKD induced by 5/6 kidney ablation were fed either a regular diet or a diet containing SZC (4g/Kg) and followed for 7 days. Feces NH₄⁺ was measured before and after addition of 50 mEq KCl/L to release NH₄⁺ from SZC. NH₄⁺ sequestered in SZC in the gastrointestinal tract was estimated from the delta fecal NH₄⁺observed when KCl was added to liberate the sequestered NH₄⁺. Results: In mice with CKD fecal NH₄⁺ excretion was higher than in normal mice and also higher than urine NH₄⁺ excretion measured concurrently. Using data pooled from the SZC diet, the delta NH₄⁺ was 6.5 ± 0.6 as compared to 0.6 ± 0.6 µmol/g on the normal diet p<0.0001. Conclusions:Fecal NH₄⁺ excretion in CKD is increased and about 6-fold higher than urine NH₄⁺ excretion revealing an important route of elimination of NH₄⁺ present in the GI tract. SZC administration sequesters a substantial portion of NH₄⁺ in the GI tract suggesting that the binding of NH₄⁺ offers therapeutic potential beyond its known primary action as a specific K⁺ binder.

Mustard bran in lactating dairy cow diets

Two trials using lactating Holstein cows were conducted to evaluate effects of a diet containing oriental mustard bran on dry matter intake (DMI), milk production, milk components, and organoleptic properties. In experiment 1, 34 lactating cows (24 multiparous and 10 primiparous; days in milk ≥ 50 d) were used in a switchback design to determine the lactational response and organoleptic quality of milk when the diet contained 8% oriental mustard bran (MB) versus a control diet (CON). Mustard bran replaced a portion of soybean meal and all the beet pulp in the CON diet. Milk yields were greater for cows fed the MB diet; however, no differences were found in DMI, 3.5% fat- (FCM) or solids-corrected milk. Milk components and components production were not affected by treatment. Milk organoleptic qualities were not affected by diet. In experiment 2, 22 lactating cows (16 multiparous and 6 primiparous; days in milk ≥ 21 d) were assigned randomly within parity to receive MB or CON from wk 4 to 19 postpartum in a randomized complete block design. Cows were fed CON wk 1 to 3 postpartum. The MB diet contained the same ingredients as the CON, except sunflower seed and a portion of soybean meal were replaced with mustard bran. Milk and components data were collected during wk 3 postpartum and used as covariates to adjust treatment means. Intake was greater for cows fed the MB diet; however, daily milk, 3.5% FCM, and solids-corrected milk yields were not different between diets. Milk components and component yields were not affected by treatment. Milk urea concentration was less for cows fed the MB diet. Although cows fed the MB diet had greater DMI, this was not translated into a higher milk 3.5% FCM/DMI production efficiency ratio. During experiment 2, many cows fed MB experienced minor to severe hemolysis with bloody urine. This hemolysis believed to be caused by the S-methyl-cysteine sulfoxide contained in mustard bran could have affected milk production efficiency. The increased milk yield observed in experiment 1 was not observed in experiment 2. Adding 8% of MB to lactating cow diets had a mixed effect on DMI and milk production. Milk component yields and milk quality were not affected. Feeding this level of MB presents a hemolytic danger to lactating dairy cows.