Suitable statistical procedures were followed for analysis of the data recorded under various experiments in this study. Different statistical designs were considered for analysis of data as per Snedecor and Cochran (1994) and analysis was done using SPSS programme.

Effects of ASMM supplementation on different reproductive parameters recorded in the present study have been detailed in Table 1.

This study revealed that overall mean birth weight of the calves in control and treatment group of animals were 20.14 ± 1.70 and 19.56 ± 1.09 kg, respectively. Birth weight between the groups did not differ (P>0.05). The findings are in agreement with work done by Olson et al. (2009) and Dhakal et al. (2012). Improper feeding particularly trace mineral deficiency in the feed during the last phase of gestation could lead to different reproductive disorders like retention of foetal membranes, neonatal weakness and low birth weight (Dhakal et al., 2012). In the present investigation, we found that the onset of first post-partum oestrus in control and treatment group was 108.1 ± 16.23 and 92.3 ± 9.95 days, respectively i.e. ASMM supplementation leads to an early onset (P<0.05) of estrus post-parturition. In the present study, it was observed that most of the animals of the treatment group came in to first post-partum estrus, whereas; only four animals of control group exhibited estrus post-parturition. Oestrus signs were detected by visual signs like oedema of the vulva, congestion of mucus membrane, and presence of mucus discharge. Results are in agreement with Mohapatra et al. (2012) and Verma (2015) who observed that heifers and cattle supplemented with ASMM exhibited oestrus in higher percent compared to untreated animals. In general, low fertility is associated with delayed or suppressed oestrus commonly found in phosphorus, copper and zinc deficient animals (Smith and Akinbamijo, 2000; Underwood and Suttle, 2003; Dhami et al, 2018). Effect of ASSM on conception rate at first postpartum oestrus is one of important parameters to measure the reproductive efficiency.The result of the present investigation clearly showed that supplementation of ASMM increased (P<0.05) conception rate in treatment than control groups (77.78 versus 22.22 %). Our results of early onset of first postpartum estrus in treatment than control animals are similar to the previous work of Koley and Biswas, (2004), Rabiee et al. (2010) and Agrawalla et al. (2017), who also observed that mineral supplementation reduces the time of onset of first postpartum estrus therby decreases days to first service postparturition and hence improves conception rate in bovine species. Poor nutrition in association with poor reproductive management leads to delayed puberty, inefficient oestrus detection, long post-partum anoestrus, low conception rates, high rates of embryonic mortality, long calving intervals and a general lowering in the fertility of the herd. The improvement in reproductive efficiency may be attributed to more bioavailability of minerals and the beneficial action of minerals on the neuroendocrine axis and reproductive function.

Effect of ASMM supplementation on milk constituents in both the groups have been presented in Table 2. The overall mean of fat, total solid, solid not fat, total ash and CP % did not differ between the groups (P>0.05). Similar findings have also been reported by various researchers (Rabiee et al, 2010; Begum et al, 2010; Singh et al, 2016), who found no significant changes in milk components such as milk protein, milk fat and milk SNF between the supplemented and non-supplemented groups. In the present study, we found that the overall mean milk yield in control and treatment group was 9.42 ± 0.54 and 10.76 ± 0.37 kg/day respectively. Mean value of milk yield was significantly (p<0.05) higher in treatment than control groups. This finding is in full agreement with Singh et al. (2016), who reported the overall difference in milk yields of control and treatment (ASMM supplemented) groups was significant (P<0.05). These findings are also similar to those of Hackbart et al. (2010) who reported an increase in milk production in dairy cattle at the mid-lactation stage of milk production. In Indian conditions, Tiwari et al. (2013) have reported an increase in milk production as well as increased in total lactation length in cattle post area specific mineral mixture supplementation. Nocek et al. (2006) observed an increase in milk production during the second lactation as compared to the first lactation post-mineral supplementation. Sahoo et al. (2017) and Saxena et al. (2008) also found increased milk yield by supplementation of area specific mineral mixture in dairy cattle of the hilly region. Outcome of our study clearly showed that feeding of the mineral mixture could improve milk production potential of crossbred cows due to an impact on the milk-producing cells in the udder (Gupta et al., 2017).

Supplementation of area-specific mineral mixture resulted in an early onset of first postpartum estrus, enhanced conception rate and increased the milk yield without any significant effects on milk constituents like milk fat, total solids, total ash, CP, SNF. The addition of specific deficient minerals in the form of ASMM is, therefore, recommended to the feed of the dairy cows preferably during last trimester of pregnancy to obtain better reproductive efficiency and higher milk production.

The authors are thankful to the Director and Joint Director (Academic), ICAR- National Dairy Research Institute Karnal India and the Director, ICAR- Eastern Regional

Station, National Dairy Research Institute, Kalyani, West Bengal, India for providing necessary facilities for the work. The first author is thankful to Indian Council of Agriculture Research, New Delhi for providing an opportunity to pursue Master degree.