The incidence of SCK was maximum (P<0.05) in winter in comparison to hot-humid season in the farm cows (30.23 vs. 26.31%). However, in field cows the incidence of SCK was low (10.71%) than the farm cows in winter season. No incidence of SCK was found in hot-humid season in the cows selected from the field (Fig 1). The incidence was low
viz., 10.52 and 8.0% during the autumn season in field and farm cows, respectively. In spring season the SCK was 11.11 % in the farm cows, but no incidence was found in the field cows. The incidence of SCK was undetectable during 5-40 and 41-60 days postpartum in Sahiwal cows, however crossbred farm cows exhibited significantly higher (P<0.05) incidence (20/55) than Sahiwal (2/50). Buffaloes did not show the incidence of SCK and disorders like retention of placenta, dystocia and mastitis. The overall incidence of SCK in the farm animals in early lactation of 5-20, 21-40, 41-60 days increased steadily and was 6.89, 10.34 and 34.28%, respectively (Table 2). No incidence of SCK was found during 5-20 days of lactation in field animals. Parity-wise incidence of SCK in the farm animal indicated a gradual rise with advancing parity from I to III and above parity. Under field conditions, no incidence of SCK was detected in Ist parity. The incidence of SCK was 2 out of 34 in the I parity farm buffaloes, however no incidence was found in buffaloes under field conditions. Sahiwal cows suffered from SCK in III parity only (2/20) but no incidence was reported in I and II parity cows.
The milk production level did not influenced SCK incidence in Indigenous Sahiwal cows and Murrah buffaloes. The incidence was scanty in Sahiwal (2/29) and buffaloes (2/55) producing milk yield between 10-20 kg/d (Table 3). Contrary to this, incidence was significantly more (P<0.05) in crossbred cows producing milk yield of 10 to 20 kg/d (11/36). Thus higher milk producing cows exhibited maximum SCK incidence in farm animals. In field animals the milk yield of cows and buffaloes ranged between 9.3 to 32.64 kg/d (av.20.97kg/d) and 8.51 to 12.56 kg/d (av.10.53kg/d). Mean urine ketone bodies level was lower (P<0.05) in buffaloes as compared to cows (4.14 mg/dl vs. 7.86 mg/dl ; Fig 2). It was found that high yielding cows producing 28.50 to 32.64 kg milk/d had higher (P<0.01) level of urine ketone bodies (10.95-12.25mg/dl) in comparison to av.4.65 mg/dl level in medium producers (av.11.44 kg/d). Field buffaloes producing milk yield of 8-10kg/d was found to have av.4.14mg/dl urine ketone bodies. Further, mean urine glucose level did not vary between the cows and buffaloes.
In the present study, it has been observed that the low producing cows are least susceptible to SCK or clinical ketosis in comparison to high producing animals
(Singh, 2002; Chakrabarti., 2006; Samiei et al., 2013). Since season has indirect effect on SCK incidence due to management factor and change in quality of feed and fodders, the effect of Hot-humid season was more on SCK incidence in comparison to the rest of the seasons. Temperature with high relative humidity (RH) further exacerbates the stress level
(Marai et al., 2007). The high THI in this study might have contributed to higher SCK incidence in high producing cows due to impaired immunity, inadequate fodder and increase in physiological reactions indicating stress on animals
(Waldron, 2010). THI adversely influence milk yield of cattle and a decrease milk yield by 0.2 kg/unit of THI over 72
(Ravagnolo et al., 2000; Thirunavukkarasu et al., 2011). The high temperature in summer elevates physiological reactions like respiration rate, pulse rate, rectal temperature and reduce feed intake in cattle
(Valente et al., 2015; Aleena
et_al2018). The decline in feed intake, metabolism, body weight and milk yields is an physiological adjustment to alleviate the heat imbalance and the drop in the lactation yield is proportional to the length of the heat stress
(Habeeb et al., 2018a). Further, the availability of feed quality and energy become one of the rate limiting factors for the milk secretion in summer season
(Liinamo et al., 2012; Manzanilla-pech et al., 2014). Therefore high yielding cows suffer more from ketosis than the low yielders
(Chakrabarti, 2006). Since milk yield gradually increases with the advancement of parity, the high parity (III) animal had more SCK incidence than the animals of I and II parity which resulted in a significant decline in milk yield (15.48 vs 7.72Kg/d) in healthy vis a vis SCK cows in this study. Thus a decline of 25-60 percent in milk production in bovine clinical ketosis may occur in cows
(Kumar et al., 2015). The inadequate energy intake in summer attenuate requirement of glucose which causes mobilization of body reserves, fatty liver and increase in rate of ketone body production resulting in ketosis
(Benedixen et al., 1987). The higher incidence of SCK during 41- 60d of early lactation was due to the peak yield and the associated negative energy balance which is most often attained during these days of lactation
(Mir and Malik., 2002). This corroborated the higher incidence of SCK in farm cows producing higher milk yield >20kg/day in comparison to medium milk yield <10kg/day. Due to this reason factors like stage of lactation, (41- 60d), number of parity (III and above) and hot- humid (HH) season influenced the SCK incidence in this study. The higher incidence of SCK in HH season was due to high THI>80 thereby suggesting adoption of appropriate measures like adequate shelter and nutrient availability and the timely detection of SCK incidence by dairy farmers. The buffaloes and Sahiwal cows were least affected by above factors due to their thermal tolerance adoptability and medium milk production level
(Behera et al., 2020). Further buffaloes and cows can withstand rigors of high temperatures if they are provided with adequate shelter,
ad lib green fodder and water availability
(Ludri and Singh, 1987; Yadav et al., 2016).