An extensive in vitro experiment was planned to study the effect of varying levels of dietary cation-anion difference (DCAD) on in vitro nutrient digestibility and its effect on rumen microbes. For experiment, two negative DCAD diet were prepared from conventional prepartum total mixed ration (TMR) supplemented with anionic salt @ -50 (Low negative; LN), -100 (High

negative; HN) and a negative control without any anionic supplementation (CON1) was used for comparison. Similarly, two positive DCAD diet were prepared from conventional postpartum TMR with cationic salt supplementation @ +200 (Low positive; LP), +400 (High positive; HP) along with positive control (CON2) diet. DCAD diets was formulated using equation (% Na/0.023 + %K/0.039) – (%Cl/0.0355 + %S/0.016) mEq/100 gm of DM. Analysis of result revealed that negative DCAD (LN & HN) had better PF (mg/ml), NH3-N% and EMMP % then CON1 diet (p<0.01) and highest value was observed with HN DCAD suggesting that negative (especially HN) DCAD during prepartum can be helpful in improving rumen nutrient digestibility and microbial protein synthesis. Whereas, CON2 had better in vitro parameters (p<0.05) than positive DCAD (LP & HP) but no deleterious effect was observed, thus, suggesting that, both positive and negative DCAD are safe for use in ruminants.

Highlights

• Two negative (-50 & -100) and positive (+200 & +400) DCAD diets were prepared.
• Negative DCAD diet had better in vitro nutrient digestibility then control.
• Addition of cations and anions in ruminant ration is safe.