In Vitro Evaluation of Organic and Inorganic Zinc Supplemented Diets on Rumen Microbial Fermentation

In-vitro studies were conducted to evaluate organic and inorganic zinc (Zn) based calf starters and TMRs for rumen microbial fermentation. Six mineral mixtures (MM) containing Zn as (inorganic) ZnSO₄ (I) or (organic) Zn-lysine (O) at 0.4%, 0.8% and their combinations i.e. MM₁ (I^0.8%O⁰), MM₂ (I^0.4%O⁰), MM₃(I₀O_0.8%), MM₄ (I⁰O^0.4%), MM₅ (I^0.4%O^0.4%) and MM₆ (I^0.2%O^0.2%) were prepared and used @ 2% in calf starters (CS₁, CS₂, CS₃, CS₄, CS₅ and CS₆). Total mixed rations (TMR₁, TMR₂, TMR₃, TMR₄, TMR₅ and TMR₆) were formulated using oats hay and calf starters (Roughages: Concentrate ratio= 50: 50). The chemical composition of CSs and TMRs was comparable and it was found that gas production (P<0.05) and true NDF digestibility was higher (P<0.01) in calf starter (CS₆) whereas the partioning factor and microbial mass production (MMP) were higher in the inorganic Zn containing CSs. The level of NH₃-N was the highest (P<0.01) in the organic Zn (CS₃ and CS₄) and lowest in combination (CS₅ and CS₆) calf starters. Among the TMRs, net gas production, true NDF and OM digestibility and ME were higher (P<0.05) in TMR₆ containing a combination of inorganic and organic Zn. Higher MMP (P<0.05) was achieved in inorganic Zn based TMRs. It may be concluded that fermentation and fiber digestibility improved in TMR with a combination of inorganic and organic Zn but higher MMP was achieved with inorganic Zn based ration.