Comparative Analysis of Milk Fatty Acids and Minerals of Indigenous vis-à-vis Crossbred Cattle and Buffaloes

Milk constituents including fat and protein percentage as well as fatty acid and mineral contents have drawn the attention of researchers in recent years, because of their direct effect on human health. The milk fat extracted from bovine milk constitute about 70% saturated fatty acid (SFA), 25% Mono unsaturated fatty acid (MUFA) and 5% Poly unsaturated fatty acid (PUFA) which deviates from the favourable fatty acid profile for human health of 30% SFA, 60% MUFA and 10% PUFA, respectively (Bilal et al., 2014). The SFAs are reported to be associated with the increased concentration of blood cholesterol and are responsible for cardiovascular diseases, weight gain and obesity (Pulina et al., 2017). Conversely, MUFAs, due to their cholesterol- declining properties (Schwingshackl and Hoffmann 2012) and PUFAs, due to influence on plasma lipids level associated in cardiac and endothelial functions are considered to lower the threat of coronary heart diseases (Zhang et al., 2016). Furthermore, conjugated linoleic acid modulates the plasma lipid concentrations and has anti-carcinogenic and anti-inflammatory effects (Palombo et al., 2018).

Minerals represent a small fraction of milk (approx. 8-9 g/L) and are distributed in the soluble and the colloidal phase depending on the chemical form (Zamberlin et al., 2012). Minerals play an important in regulation of biological systems and cellular metabolism, like calcium, phosphorus and magnesium are involved in development of bones and teeth (Soyeurt et al., 2009). The micro-minerals including Zn, Mn and Cu play pivotal roles in immune function and enzyme system (Dunshea et al., 2019). In recent times, the indigenous cattle milk demand has gained much popularity due to its A2 milk protein (Kumar et al., 2020).  But in a study it was observed that in Vrindavani crossbred cattle genotypic frequency of A2A2 was 0.42, whereas genotypic frequencies of A1A2 and A1A1 were 0.47 and 0.11, respectively (Kumar et al., 2019). Further, there is dearth of information about the fatty acid and mineral profile of cattle and buffalo milk. Thus, this study will provide an overview of the fatty acid and mineral content in the milk of indigenous cattle and buffalo, compared to crossbred cattle. The fatty acid and mineral profile of indigenous cattle will also provide scientific data for the superiority of indigenous cow milk in terms of their content, if any.

Only limited number of studies are available on the effect of breed and non-genetic factors on composition of milk fatty acid and mineral concentration in tropical countries like India having a wide range of bovine genetic resources. Thus, the objectives of present study was to compare fatty acid composition and mineral concentration in milk of indigenous cattle, crossbred cattle and buffalo, under a similar production system.

Experimental animals and farm
 
This study was conducted on 187 individual milk samples, which includes 124 crossbred Vrindavani cattle, 19 indigenous cattle (Tharparkar n=11; Sahiwal n=8) and 44 Murrah buffaloes, were collected from Cattle and Buffalo Breeding Farm, ICAR-IVRI, Izatnagar, Bareilly, India. Vrindavani cattle were developed as synthetic strain of composite cattle in India from the native indicine Hariana cattle crossed with three taurine dairy breeds: Holstein, Brown Swiss and Jersey (Singh et al., 2011). The animals are reared in loose housing system with free-stall dairy barn under tropical environmental conditions. During sample collection, animals were fed with green fodder and concentrate mixture composed of maize, wheat bran, Barley and Napier grass with other supplements.
 
Sample collection
 
Collection of milk samples were collected during January, 2019 from each animal. The morning milk samples were collected as suggested (Sharma et al., 2018). After proper mixing in plastic bottles, the milk samples were immediately transported to the laboratory on ice. The samples were homogenized using Vortex at 2400 rpm for thirty seconds before processing.
 
Estimation of milk constituents and fatty acid profile
 
After proper mixing of samples, the fat and protein percentage in 187 milk samples were analysed by using Lacto Scan milk analyser. The contents of different milk fatty acids were estimated using a gas chromatography (6890N, Agilent), which included SFAs (C6:0, C8:0, C10:0, C12:0, C14:0, C16:0, C18:0, C20:0, C24:0); MUFAs (C14:1, C16:1, C18:1n9c) and PUFAs (C20:2, C20:4n6 and C22:2).

Fatty acid profiling was done by direct FAME synthesis as explained by O’ Fallon et al., (2007) with slight modification. The unsaturation indices for milk fatty acid were calculated as the ratio of an unsaturated fatty acid to the sum of unsaturated and its corresponding saturated fatty acid, multiplied by 100 (Schennink et al., 2008).
 
Estimation of milk minerals
 
Milk samples were analyzed for macro-minerals including, Calcium (Ca), phosphorus (P) and microminerals including iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn). The estimation of calcium and phosphorus was done as reported previously (Talapatra et al., 1940). The concentration of micro minerals (Fe, Cu, Zn and Mn) was determined using atomic absorbance spectrophotometer in their mineral extracts.
 
Statistics
 
The Proc GLM procedure of SAS 9.3 (SAS Institute, Inc. 2008) was used for estimating the effect of breed type on milk as follow;

Y_ij = μ + B_i + e_ij

Where
Y_ij= The j^th observation of ith breed (3 level).
e_ij= Random error (NID = 0, σ²_e).

The least squares mean of individual and indices of milk fatty acid profile and mineral content for the different breeds are reported in Table 1. The fat percentage was significantly (P£0.05) higher (8.400±0.27) in Murrah buffaloes than crossbred (4.280±0.10) and indigenous (4.150±0.21) cattle. The protein percentage was significantly (P£0.05) higher in milk of Murrah buffaloes (3.140±0.02) and indigenous (3.000±0.02) cows than crossbred (2.810±0.02) cattle. The analysis of variance indicated highly significant (P<0.0001) breed differences in the concentration of almost all fatty acid composition traits under investigation, except C22:2. Further the mineral profile (except Ca and P) of indigenous cattle, crossbred cattle and buffalo differ significantly from each other. The concentration of SFAs (C6:0, C8:0, C10:0, C12:0, C14:0, C16:0, C18:0, C20:0, C24:0) were found to be significantly (P<0.001) higher in the Murrah buffaloes than the crossbred and the indigenous cattle (Table 1). The findings were in agreement with previously reported higher fraction of saturated fatty acid in buffalo milk (Pegolo et al., 2017). However, Haggag et al., (1987) found lower concentration of saturated fatty acid in the Egyptian buffalo compared to the Egyptian cow milk.  However, MUFA and PUFA content (C16:1, C20:2, C20:4n6, C22:6N3) were higher in the indigenous cattle (0.434±0.07, 0.280±0.06, 0.096±0.02 and 0.450±0.08 gm/100 gm of milk, respectively) in comparison to crossbred cattle (0.247±0.02, 0.230±0.01, 0.031±0.00 and 0.178±0.02, gm/100 gm of milk, respectively) and Murrah buffaloes (0.214±0.07, 0.065±0.01, 0.050±0.01 and 0.211±0.03 gm/100 gm of milk, respectively). The concentration of Oleic acid (C18:1n9c) was found to be significantly higher (P<0.001) in crossbred cattle (0.38±0.02 gm/100 gm of milk), while the concentration of C14:1 (0.108±0.02 gm/100 gm of milk) was higher (P<0.0001) in buffaloes. In addition, the buffalo milk showed lower contents of C22:2 (0.447±0.11 gm/100 gm of milk) to the indigenous (0.459±0.13 gm/100 gm of milk) and the crossbred (0.596±0.04 gm/100 gm of milk) cows. The concentration of higher PUFAs content (C20:2, C20:4n6 and C22:6N3) in indigenous cattle also has been reported earlier (Sharma et al., 2018). The higher concentration of PUFA and low SFA in indigenous cattle milk suggest its beneficial effect to human health. Considering the unsaturation index, buffalo milk contained significantly higher amount of C14 index and C18 index (1.178±0.02 and 1.227±0.02) than crossbred (1.110±0.01 and 1.113±0.02) and indigenous cattle (1.066±0.01 and 1.065±0.01). The C16 index was highest in crossbred cattle (23.895±1.53), while C20 index was highest in indigenous cattle (2.835±1.62).



The average concentration of Ca and P in milk did not differ significantly between different bovine breeds (Table 2). The Cu and Mn contents were found to be significantly (P<0.0001) higher in the Murrah buffaloes (1.817±0.05 and 2.271±0.03 mg/l, respectively) followed by the indigenous cattle (1.291±0.11 and 2.026±0.10 mg/l, respectively) and the crossbred cattle (1.071±0.05 and 0.922±0.06 mg/l, respectively), respectively. However, the Fe and Zn concentration were significantly higher in indigenous cattle (9.421±1.05 and 5.461±0.32 mg/l, respectively) in comparison to Murrah buffaloes (7.692±0.39 and 4.548±0.28 mg/l, respectively) and crossbred cattle (9.175±0.29 and 3.642±0.12 mg/l, respectively). Patel et al., (2018) has also reported the higher Ca content in Murrah milk, while the higher phosphorus content was in indigenous milk. The significant difference in milk mineral content among breeds was also reported by Mariani et al., (2002), with lower mineral content in Holstein-Friesian compared to Brown Swiss, Reggiana and Modenese breeds. The higher content of micro-minerals (Fe and Zn) in indigenous cattle milk are involved in boosting immune related pathways and other cellular physiological processes (Yamaguchi et al., 2010). Inadequate concentration of Fe and Zn in diet may hamper the absorption and function of other nutrients leading to challenges in normal development of the animal.

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This study provided an overview of fatty acid profile and mineral concentration in milk of crossbred and indigenous cattle vis-à-vis Murrah Buffaloes reared under the same managemental and feeding regime. The milk of indigenous cattle breed had significantly higher concentration of beneficial minerals contents (P, Fe, Zn) and unsaturated fatty acids (USFAs), suggested its greater potential benefit on human health compared to crossbred cattle and Murrah buffalo. Thus, the effort should be made to valorise the milk of indigenous breed.

The authors duly acknowledge the financial support rendered by ICAR-IVRI, Izatnagar and world bank funded CAAST-ACLH project of NAHEP.

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