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Effect of area specific mineral mixture supplementation on milk yield and reproductive traits of crossbred dairy cattle under sub-tropical region of north eastern India

Nutrients requirement plays a very crucial role in regulating biological systems, immunological, health, lactation and reproductive performance in dairy cattle.Therefore, the present study was conducted to assess the effect of area specific mineral mixture supplementation on milk yield, reproductive performance and economic of dairy cattle for a period of 120 days. Experimental animals were selected randomly from four villages of Dima Hasao district of Assam. Twenty lactating crossbred cattle (n=20) were divided into two groups (10 milch cows/group) viz., treatment (T2-supplement of 50gm mineral mixture/cattle/day) and control (T1-no supplementation) in a completely randomized designed. Results revealed significant (P<0.05) improvement in milk yield by 1.36 litre per day (18.68%), reproductive performance and benefit cost ratio (3.55 vs 3.11) in the studied. Thus, mineral mixture supplementation in the diet of dairy cattle gave better results in improving milk yield and reproductive efficiency for sustainability livelihood in smallholders’ dairy farming in hilly regions.


Introduction
India has been the world's largest milk producer for the last two decades, with a 22.67 percent share of global dairy production. Around 70 million Indian households are projected to be active in dairy production vis-à-vis 150 million households worldwide (FAO, 2020) [1] . The dairy sector is a major subsidiary occupation and source of income for 75 percent of the Indian population, of which 30 percent are poor, living in rural areas (Douphrate et al., 2013) [2] . In many livestock production systems, approximately two-thirds of improvements in livestock productivity can be attributed to improved nutrition (Fitzhugh, 1978) [3] . At present, the country is facing a net deficit of 35.6% green fodder, 10.95% dry crop residues and 44% concentrate feed ingredients to meet requirement of the growing livestock population (Dhawal et al., 2020) [4] . Ca, P, Na, Co, Cu, I and Zn are the minerals most likely to be deficient under grazing conditions (McDowell, 1993) [5] . However, in all types of dairy animals, the effects of mineral deficiency and metabolic disorders have been observed due to lower mineral and vitamins content, available energy, protein, and poor bioavailability of essential macro and micro minerals from different feed staffs (Bhanderi et al., 2014;Ramachandra et et., 2007;Sharma et al., 2005) [6. 7, 8] . In order to compensate for the low productivity of the animals, farmers fed only the productive animals optimally, and the rest of the animals (male, calves, spent female) are fed lower quantities or imbalanced diet. Nowadays, mineral nutrients play a key player role in controlling biological systems, development, health, lactation and reproduction, and microbial fermentation is well known in the animal rumen (Weiss, 2012;McDowell, 2003) [9,10] . In rural areas or hilly regions, dairy cattle are largely dependent on grazing and crop residue with little or no additional concentrate or mineral mixture except common salt (Garg et al., 2005) [11] . In the North Eastern Region (NER) of India, the total milk production in the region was 1454.17 thousand tones (17.60 percent) vis-à-vis the country's 187749.46 thousand tones (41.77 percent) (BAHS, 2019) [12] . Despite the socio-economic value of NER, under the smallholder dairy farming system, milk production is seasonally sensitive, with feed variations in both quantity and quality being the main driver. Due to feed scarcity, a dry season decrease in milk production of over 40 percent is a typical phenomenon. The adoption of improved technologies and practices for feed production, conservation and utilization in dairy farming communities is weak. Dairy productivity is constrained by farmers such as poor quality feed, shortage of feed resources, high cost of raw feed ingredients (65-70%), shortage of skilled and committed labour (28-32.5%), transportation charge were found to be major bottlenecks in these regions. In lactating dairy animal, insufficient supply of nutrient requirements led to a decline in milk yield, severe and prolonged energy and protein deficiency depresses reproductive function (NRC, 2001) [13] . Pressure on land and fodder resources and diminishing grazing land coupled with poor quality feed resources are one of the major challenges in dairy farming, especially widespread macro-and micromineral deficiency (Singh et al., 2014;Kumaresan et al., 2010) [14,15] . The mineral concentration in crops and forages depends on the genus, species, variety, form of soil, environment and stage of maturity of the fodder (Gowda et al., 2001) [16] . Mineral deficiencies or soil or forage imbalances have long been held responsible for low production and poor reproductive performance in tropical and subtropical agro-climatic conditions among cattle and buffaloes fed on crop residues (Garg et al., 2008;Ghosh et al., 2008;Das, 2003) [17,18,19] . With reference to area specific mineral mixture supplements in dairy cattle of these regions, literature is deficient or scanty. Increase in milk yield and reproductive efficiency as a result of area-specific mineral mixture supplementation recorded in some parts of India  [20,21,22] . Therefore, the aim of the present study was envisaged to assess the effect of area specific mineral mixture supplement on milk yield and reproduction performance of dairy animals under agro-climatic condition of hilly region of Dima Hasao, Assam.

Materials and Methods 2.1 Study area
This experiment was carried out in lactating crossbred cattle under front line demonstrations at autonomous Dima Hasao district of Assam, India. Selection of four villages (Gadain Razi, Krishna Nagar, Upper Bagetar, and Lodi) by simple random sampling techniques was used for the study. This zone is located between 24 0 58 to 25.32 0 N latitude and 92.27 0 to 93.43 0 E longitudes with an altitude varying from 140 to 1868 meters above the mean sea level. The area experiences sub-tropical and humid climate zone with temperature varies from 6.02 0 C to 14.7 0 C during winter and 14.31 0 C to 33.06 0 C during summer and 1145mm of annual rainfall.

Animal, Experimental diet and management
All the animals were selected at a mid stage of 2 nd lactation, milk yield and parity. A total of twenty lactating crossbred cattle (n=20) were divided into two groups (10 milch cows/group) viz., treatment and control. Animals from the treatment group (n=10) were fed area specific mineral mixture (AAUVETMIN) developed by Assam Agricultural University at the rate of 50 gram/cattle/day, whereas cattle from the control group were not given any supplementation. Composition of area Specific Mineral Mixture ((AAUVETMIN) contain calcium (17.60), Phosphorus (7.00), Magnesium (1.50), Zinc (0.13) and copper (0.08) respectively, measured in percentage by mass. Feeding practices by farmers were similar in both the group except the supplementation of AAUVETMIN in the treatment group only. Standard animal management practices were followed in the farmer's field. Animals were fed green fodder, hay and concentrate feed as per specific recommendation of standard feeding ration schedule (ICAR, 2013) [23] . Water was offered ad libitum throughout the experimental period. The feeding trial was lasted for 120 days.

Data collection on milk yield, reproductive performance and cost benefit ratio
Milk yield was recorded daily, twice both in morning and evening at 6:00 and 17:00 hours by the farmers and at weekly interval by the researcher. Data on reproductive traits viz. post-partum estrus, service period and number of artificial insemination required for conception were recorded on the basis of dairy cow owner's response. The benefit cost ratio for all the groups were calculated. A training programme was conducted for the farmers before starting the experiment to educate them for feeding and correct method of data recording on different parameters in the adopted villages.

Statistical Analysis
The data were analyzed statistically as per Snedecor and Cochran, 1989 [24] and student's t-test of significance (2 way split analysis of variance) between groups were performed using SPSS for Windows (version 17.0 Microsoft).

Results and discussion 3.1 Effects on Milk yield
The experiments were performed with dietary supplementation area specific mineral mixture to find out whether AAUVETMIN will have any effect or any change on milk yield, reproductive performance and benefit cost ratio in crossbred dairy cattle in this hilly region. The observations on milk production, reproductive traits and economic impact on dairy cattle are presented in Table-1. The average milk yield in treated group was found significantly higher (p<0.05) as compared to its yield observed in control group. These finding were in agreement with the results reported by Srivara (2019) [20] ; Meher et al. (2017) [21] and Gupta et al. (2017) [25] in crossbred cattle. Pandey et al. (2018) [26] and Nocek et al. (2006) [27] also reported increase in milk yield due to supplementation of area specific mineral mixture in dairy cattle. Mohsina et al. (2017) [28] and Tiwari et al. (2013) [29] reported feeding of area specific mineral mixture increased milk yield 25% in field trials. Similar to the present findings, Hackbart et al. (2010) [30] observed increase in milk production at 14 week supplementation of organic trace minerals to cattle. This finding was in line with Akila et al. (2013) [31] and Senthilkumar et al. (2015) [32] who were reported that supplementation of TANUVASmineral mixture to a dairy cattle resulted in increase in milk yield by 1.46± 0.14 and one litre per day in cow respectively. Singh et al. (2016) [33] observed significantly higher (p<0.05) milk production in supplemented animal with mineral mixture. However, result indicating that dietary mineral mixture supplementation attributes improved milk production potential of cattle could be due to having impact on the mammary myoepithials cells-smooth muscle alpha-actin (ACTA2) in the udder during lactation. Further, synergistic effect of micro and micro elements contribute in the working of memory cells to enhance their productivity. This finding was in accordance with Ghosh et al. (2016) [34] and Rohilla et al. (2007) [35] observation. The present results support the findings of Rabiee et al. (2010) [36] and Mohsina et al. (2017) [28] observed no significant differences in milk fat % and milk SNF % between the supplemented and non-supplemented groups of animals.

Effects on reproductive performance
Reproductive traits i.e. onset of first Post-partum estrus after calving, service period and number of insemination per conception were also recorded during the experimental period as shown in Table-2. These reproductive traits significantly (P≤0.05) differed in the treatment group of dairy animals as compared to control group. The supplemented group of animals voluntary waiting period (48.37 days) was observed slightly lower than the control group (63.21 days). On average onset of first postpartum estrus was observed to occur 14.84 days earlier in the supplement animals as compared to control group. Moreover, the mineral mixture fed group with a service period (62.37 days) was also found significantly (P≤0.05) lower than the control group (86.21 days). Similar findings were also reported by Sivara (2019) [20] , Gupta et al. (2017) [25] , Sahoo et al. (2017) [37] , Mohapatra et al. (2012) [38] and Devasenat et al. (2010) [39] in crossbred cattle. Significant effect of service period and number of insemination required for conception was  [40] regarding improvement in general health score condition of the cows after area specific mineral mixture supplementation. The improvement in reproductive efficiency in cattle could be attributed due to mineral supplementation as compared to the performance of non-supplemented group was very clear in this study.

Cost of milk production and Benefit Cost ratio (BCR)
The economic analysis of the data revealed that dietary supplementation of area specific mineral mixture enhances the milk yield by 18.68 % per day in treated group. It could be inferred from Table-3 that benefit cost ratio was higher (p<0.05) in supplement animals as compared to control 3.11 a 3.55 b 0.61 5.62 ** Numbers of observations are given in parentheses. Means bearing the different superscript within a row differ statistically significant; * P<0.05; **P<0.01; Ϯ price is varies in hilly region, NS-Non significant group. The feeding cost of per litre of milk was lower (₹ 22.73) in treatment group as compared to control group (₹ 25.80). Gross return from sale of milk (₹ 691.20 vs 582.40) and net profit litre of milk was found to be higher in treatment group (₹ 57.34) than control group (₹ 54.31). The BCR was also found higher in treatment group as compared to control (₹ 3.55 vs 3.11). Similar result to the present finding was in accordance with Sivara (2019) [20] in milch cattle.

Conclusions
It can be concluded from the present study that dietary supplementation of mineral mixture to the lactating crossbred