Housing is one of the key determinants of animal comfort, and in turn the productivity and welfare of animals. This study was an attempt to evaluate the effect of housing modifications on the biochemical, productive, and reproductive aspects of milking Sahiwal cows reared in hot arid region of the Great Thar Desert. On expected lines, the mean THI values were close to 80 in all the groups, indicating heat stress on animals. Other researchers have also reported THI in the zone of stress for dairy cows in northern India during summer and hot humid seasons (Bhan et al. 2012). The sheds with heat amelioration devices in the form of fans and water sprinkling however maintained lower THI compared to G1 and G2. This corroborates with the earlier reports have also shown lower temperature concomitant with housing modification (Singh et al. 2014; Kumar et al. 2011; Chanpongsang et al. 2010 and Gaughan et al. 2010) who found significantly. Moreover, use of evaporative cooling in dairy barns lowered the THI by some points (Sinha et al. 2019; Bucklin et al. 2009).
Different housing modifications have been associated with improved performance of animals (Lowe, Lively and Gordon 2019). In our study, the cows housed in shelter provided with heat alleviating measures coupled with and without rubber mat flooring showed significantly better milk yield. Use of fogger with fans significantly improved the milk production of crossbred dairy cows (Sinha et al. 2019). Spraying water on animals reduces the heat load (Tresoldi et al. 2018) and negates the adverse impact of heat stress to some extent. Earlier studies in cows and buffaloes have also shown the animals housed with heat stress alleviation strategies to maintain higher production (Yadav et al. 2016; Ambulkar et al. 2011; Chanpongsang et al. 2010 and Agarwal 2004). However, cows reared on rubber mats alone without any heat alleviation strategies did not improve production, agreeing with the reports of Upadhyaya et al. (2015), Eicher et al. (2013) and Pempek and Botheras, (2009). Furthermore, the composition of milk in cows of different treatment groups did not show a significant difference in means of milk fat, protein, lactose, SNF and total solids during the study improved. However, the treatment groups with heat stress amelioration strategies showed a significant difference with higher milk lactose, and proteins during the last two or three fortnights. These findings are in accordance with the reports of Upadhyay et al. (2015), and Eicher et al. (2013) who noted no difference in milk composition of animals housed with or without rubber mat on floors. Though effect of heat amelioration strategies has been conflicting on milk composition, with Shiao et al. (2011), Smith et al. (2006) and Aggarwal, (2004) reporting no effect of cooling strategies on milk composition of cows and buffaloes, Seerapu et al. (2015) reported significant effect of cooling strategies on milk composition of Mehsana buffaloes. The trend in milk composition of treatment groups in this study indicates use of sustained cooling strategies overtime can bring about improved performance of animals.
Biochemical attributes are one of the crucial indicators of stress in animals. Both ALP and AST are considered as crucial enzymatic markers of heat stress. The mean ALP and AST did not differ significantly among treatment groups, however, both G3 and G4 groups with cooling strategies maintained lower ALT, consistent with earlier report in buffaloes (Vijayakumar et al. 2011). Furthermore, the AST level was significantly lower in all three treatment groups during the last two fortnights. Researchers have reported a significant increase in ALT activity in heat stressed animals (Pandey et al. 2013; Bhan et al. 2012; Abdelatif and Alameen 2012; Sharma and Kataria 2011). While Bhan et al. (2012) and Calmari et al. (2011) reported an increased AST activity in heat stressed animals. Our findings indicate a positive effect of cooling strategies on heat stress amelioration in G3 and G4 cows, which translated into lower ALT and AST activities in cows of these groups. There was significant effect of cooling strategies coupled with or without rubber mat floors on serum cholesterol levels. The higher cholesterol levels can be indicative of higher feed intake in these groups due to decreased heat load. However, no significant difference was evident in serum glucose, BUN, and total proteins among cows of different treatment groups, which concurs with earlier reports (Das et al. 2013; Kumar 2012; Vijayakumar et al. 2011). On the other hand, the serum cortisol level, an important indicator of stress (Indu et al. 2014) was significantly lower in G4 cows compared to other three groups, while control group had highest mean cortisol levels. This indicates lower stress in the animals of animals housed in shed provided with cooling devices, and in animals with rubber mat floor compared to cows housed in shed with concrete floor. Use of foggers coupled with fans resulted in lower blood cortisol levels in crossbred dairy cows (Sinha et al. 2019). Buffalo heifers maintained with heat stress amelioration strategies also had lower cortisol levels (Verma et al. 2016; Vijayakumar et al. 2011), while heat stressed animals maintained higher blood cortisol (Marai and Habeeb 2010; Dikmen et al. 2008).