Effect of Supplementation of Essential Cation , Anion or Combination of Both on the Digestibility of Cation Minerals in Diet of Cows

August 2014 | Volume 2 | Issue 8 | Page 433 Abstract | Study was undertaken to assess the digestibility of essential cation minerals viz., Ca2+, Mg2+, Cu2+, Zn2+, Fe2+ and, Mn2+ when electrovalency of mineral supplement was positive or negative. Lactating Deoni cows were divided into 4 groups of 4 each in completely randomized block design and fed 8 KG fresh para grass, ad lib ragi straw and concentrate supplement without mineral mixture (control) or fortified with essential cation (T1) or anion (T2) minerals or both together (T3). The net electrical charge in the mineral mixtures in T1, T2 and T3 were +0.87, –1.55 and –0.64, respectively. DM (p = 0.96), OM (p = 0.96), CP (p = 0.99), Fe2+ (p = 0.98) and Mn2+ (p = 0.83) intakes were not significantly different between CG and TGs. Net charge in T2 affected CP digestibility adversely (p< 0.05). Ca2+ digestibility was apparently (p = 0.29) higher in T2 and T3. Lack of Phosphorus (P–) source in T1 affected the Ca2+ utilization in comparison to T2 and T3. Mg2+ digestibility was higher (P< 0.05) in T2 and T3 than CG and T1. Cu2+ digestibility was not significantly (p= 0.77) different between groups. Zn2+ (p < 0.01), Fe2+ (p < 0.01) and Mn2+ (p < 0.01) digestibility was significantly different between CG and TGs and appeared that the net electrical charge of mineral mixture influenced the digestibility of opposite ions. Study concluded that cation mineral digestibility was better when net electrical charge of mineral mixture was negative. Kiran BaBu S., Bandla SrinivaS*


INTRODUCTION
U nderwood (1981) suggested 22 essential mineral elements to farm animals based on their concentration in the blood i.e., either >100 or < 100 mg/dl blood plasma and categorised to 7 macro and 15 micro minerals, respectively.Another classification was drawn on the basis of net electrical charge of ions such as cation or anion (Srinivas, 2012), which is relevant in the nutrition of higher forms of animals (Miller, 1981).Delaquis and Block (1995) discussed the dietary anion and cation concept with reference to the systemic acid-base balance of the animal that is basic for all nutrient transportation.Although dietary cation-anion balance (DCAB) is relevant in dairy animals, the con-cept is restricted to balance between few cations (Na + and K + ) and, few anions (Cl -, S -and P -).This needs to be extended to understand the functional importance of all essential mineral ions supplemented in mineral mixtures (Srinivas, 2012).Present study was conducted with an objective to evaluate the digestibility of essential cation mineral elements when net electrical charge (electrovalency) of mineral ion in the mineral mixtures was positive (cationic) or negative (anionic).into 4 groups of 4 animals each.Cows were fed with 8 KG of fresh para grass (Brachiaria mutica) and ad lib ragi straw (Elusine coracana) at 8 AM and 5 PM, respectively and, supplemented concentrate mixture (consisted of 35 parts of maize, 15 parts of groundnut meal and 50 parts of wheat bran without mineral mixture and common salt) in 2 equal parts twice in a day as per the requirements (ICAR, 1998).Control group (CG) was fed basal diet without additional mineral supplements apart from those naturally present in the diet.Treatment groups (TG) supplemented mineral mixture consisted of only essential cation (T1) or, anion (T2) minerals or, both cation and anion mineral elements together (T3) added to concentrate supplement fed in CG.Composition of mineral mixtures containing cation or, anion mineral compounds is presented in Table 1.

digeStiBility trial
Digestibility trial was conducted after a preliminary period of feeding for 1 month.Trial consisted of 5 d of collection period.Body weight of animals, at zero hour of feeding and watering, recorded for 2 consecutive days before and after the trial.Faecal samples collected during trial period at 8:30 AM and sub-sampled to 1/400 parts.A part of sample was preserved with known quantities of 10 % H 2 SO 4 (V/V) in preweighed glass bottles to estimate nitrogen (N).Dried samples of feed offered, left over feed (orts), and faeces were pooled for 5 d for chemical analysis.

ChemiCal analySiS
Dried samples of feed offered, orts, and faeces analysed for dry matter (DM), organic matter (OM), crude protein (CP) and total ash (AOAC, 2005).Minerals in feed and faecal samples were estimated using inductively coupled plasma (ICP) optical emission spectrometry (Optima 8000, M/s Pelkin elmer, Waltham, U.S.A) after predigesting the samples by modified method of closed system of acid digestion (US-EPA, 2001).The digested samples were cooled and filtered through Whatmann filter paper No1.Repeated washings were given to digestion tube and filter paper using Millipore water and final volume made to 10 ml.Subsequent dilutions were made as for the concentration of the element and estimated important cations viz., calcium (Ca 2+ ), magnesium (Mg 2+ ) copper (Cu 2+ ), zinc (Zn 2+ ), iron (Fe 2+ ) and manganese (Mn 2+ ).

StatiStiCal analySiS
Data were subjected to descriptive statistics and variances between groups mean were compared using CRD based on the following model: Where, Y ij was any observation for which, µ was population mean, T i was treatment effect, B j was block effect, and e ij was random error component (Das and Giri, 1991).Pairwise comparison between group means was tested by DMRT and significance was denoted by alpha superscripts with probability (p) ranged from 0.01 to 0.05.
CP digestibility was significantly reduced (p < 0.05) in T2 which could be probably because of more net negative charge of ions in the mineral mixture.Hu et al., (2007)    digestibility was apparently (p = 0.29) higher in T2 and T3.Probably lack of P -source in the cationic mineral mixture affected the Ca 2+ utilization in T1.In general, the ideal ratio of Ca 2+ and P -intake is 1:2 to 2:1 (Horst et al., 1994).Ca 2+ to P -ratio in Ca 2 PO 4 is about 2:1.Mg 2+ intake (p < 0.01), and digestibility (p < 0.05) were significantly different in CG and TGs.Mg 2+ digestibility was higher in T2 or T3 than CG and T1.Mg 2+ digestibility improved in T2 where mineral mixture consisted of anion mineral elements i.e., net electrical charge was negative.Weiss ( 2004) reported that mean apparent digestibility of Mg 2+ was ranging from -0.04 to 0.33.According to NRC (2001), optimum Mg 2+ digestibility is 43 %.Mg 2+ digestibility in diet can be affected by increased K + intake above the stipulated requirement in the diet (Weiss, 2004).
Intake of Cu 2+ was significantly (p < 0.01) different between CG and TGs but, digestibility was not significantly (p = 0.77) affected Cu 2+ in CG utilized more efficiently because it was in lower concentration than in TGs.According to Ivan and Grieve (1975) Cu 2+ concentration in liver was inversely proportional to the dietary Zn 2+ and, directly proportional to dietary Mn 2+ supplementation.Mn 2+ was not added in the cation mineral mixture but, Zn 2+ was included.Zn 2+ intake in CG or TGs was 15 folds higher than Cu 2+ .According to Weiss (2004), Zn 2+ intake should not exceed the dietary Cu 2+ intake by more than 5 folds.Probably, higher ratio of Zn 2+ in the mineral mixture   2001).Zn 2+ intake (p < 0.05) and digestibility (p < 0.01) were significantly different in CG and TGs.Significantly higher digestibility in T3 (59 %) than T1 (39 %) indicated that Zn 2+ digestion improved in the presence of anion minerals such as P -, I -, Mo -and Se -.Fe 2+ intake was not significantly (p = 0.98) different between CG and TGs because, it was not fortified in the cation or cation + anion mineral mixture since Fe 2+ availability from the diet was sufficient to meet the requirements.Fe 2+ digestibility was negative in CG (-4 %) and significantly lesser than TGs (p < 0.01).Fe 2+ digestibility was comparable between T2 (23 %) and T3 (36 %) but not with T1 (2 %).Fe 2+ utilization also improved in the presence of anions; P -, I -, Mo -and Se -, present in T2 and T3.Mn 2+ intake was not significantly (p= 0.83) different as its availability in the basal diet was sufficient to substantiate requirement.Digestibility of Mn 2+ was significantly (p < 0.01) different between CG and TGs.Mn 2+ utilization also improved when net ion charge was negative.Cations homeostasis is partially dependent on endogenous faecal excretion controlled by the intestinal tract, liver and pancreas while, anions homeostasis is partially dependent on renal excretion (Buckley, 2000) thus, enumerating both the ions are mutually exclusive but collectively exhaustive.According to Block (2011), subjects such as ratios of Ca 2+ to P and N to sulphur, interactions between Mg 2+ and K + , Mn 2+ and Cu 2+ , and vitamin E and Se have been investigated and addressed however, no unifying concepts on mineral balances have been proposed yet.Our result indicated that utilization of some of the cation mineral elements e.g., Ca 2+ , Mg 2+ , Zn 2+ , Fe 2+ and Mn 2+ were improved in the presence of anion mineral elements P -, I -, Mo -and Se -.

CONCLUSIONS
Study revealed that interaction between electrical charge carried by the cation and anion group of minerals in the mineral mixtures and their net electrovalency influenced the digestibility.Digestibility of cation mineral elements improved when net ion charge was negative.

Advances in Animal and Veterinary Sciences August 2014 | Volume 2 | Issue 8 | Page 435Table 1 :
reported adverse impact of net negative charge on CP digestibility in dairy cows.Although net electrical charge in T3 was negative, CP digestibility was not reduced.Considering the result ofHu  et al., (2007)as well as CP digestibility observed in this study, we presume that CP digestibility might be Composition of ion specific mineral supplements.

Table 2 :
Net charge of the ions in mineral supplements.

Table 3 :
Chemical composition of diet.

Table 4 :
Feed and mineral intake and digestibility in different groups.