Comparative CpG methylation kinetic patterns of cis-regulatory regions of heat stress-related genes in Sahiwal and Frieswal cattle upon persistent heat stress.

The kinetic patterns of CpG methylation of the cis-regulatory region of heat stress-related genes on exposed to heat stress (at 42 °C) between the Sahiwal and Frieswal cattle was compared in the present study. Using an in vitro whole blood culture model, cells were continuously exposed to heat stress (at 42 °C) for 6 h. Methylation levels of five genes, viz., GPX1, HSP70, HSP90, c-FOS, and JUN were estimated by SyberGreen-based quantitative methylation-specific PCR (qMSP) assay. CpG methylation kinetics at different time points of heat stress (0.5, 1, 2, 4, 6 h) were analyzed using mixed ANOVA. The initial methylation level, estimated at 37 °C, of HSP70 was significantly high in the Sahiwal breed. A significant (p<0.001) time-dependent hypomethylation of an antioxidant gene (GPX1) CpG islands was detected at the acute phase of the stress. Heat shock protein gene (HSP70) showed a similar CpG methylation kinetics where the hypomethylation was prominent from 1 h and persisted up to 4 h. The heat stress responses of both Sahiwal and Frieswal cattle were identical as there was no distinctiveness in the methylation kinetics of CpG islands of studied genes. The acclimatization of Frieswal cattle-a breed developed in India over the years to the tropical climatic conditions, maybe one of the reasons for this similarity. Thus, the present study results could pave a path to understand the molecular mechanism of heat stress and adaptation of indigenous and crossbred cattle populations to the changing scenario in tropical climate conditions.

Development of a RAPD marker-based classification criterion for quality semen production in Holstein crossbred bulls.

In cattle production systems, an intense selection pressure for production traits has resulted in the decline of fertility traits. To optimize an efficient reproduction system, the inclusion of both male and female fertility traits in the selection process is very much essential. RAPD (Random Amplified Polymorphic DNA) was developed as a molecular biology tool and has been extensively used, to study intra- and interspecific genetic diversity. The present study was undertaken to utilize RAPD primers to investigate the association between DNA markers and semen quality traits viz. Sperm concentration, total sperm count ejaculate and initial sperm motility and thereby to identify good/poor semen producers. DNA isolated from the blood samples of healthy bulls was subjected to RAPD-PCR. The multiple regression analysis followed by independent t test was carried out to identify suitable markers. Based on the results, only 12 bands were identified as marker suitable for any of the quality trait. This includes, OPA2 ~ 760, OPA2 ~ 700, OPA6 ~ 1,200, OPA9 ~ 400, OPA9 ~ 380, OPA12 ~ 970, OPA14 ~ 715, OPA14 ~ 605, OPA16 ~ 485, OPA17 ~ 860 and OPA18 ~ 480. Multiple regression analysis selected, OPA2 ~ 760 and OPA2 ~ 1,750 for sperm concentration and OPA2 ~ 760, OPA2 ~ 700, OPA9 ~ 620, OPA4 ~ 670 and OPA18 ~ 1,015 for total sperm count/ejaculate. But the t test revealed a significant association between OPA2 ~ 760 and total sperm count. Further, discriminant function analysis also identified this marker in the first step itself. The results of the present study can be exploited as a low-cost alternative strategy for identification of good /poor semen producers in crossbred bulls at an early age.

Role of seminal MDA, ROS, and antioxidants in cryopreservation and their kinetics under the influence of ejaculatory abstinence in bovine semen.

Despite many cryopreservation techniques in bovine semen, various stressors' detrimental effects remain a significant issue. The present study targeted to assess the role of semen quality parameters, sperm function tests, lipid peroxidation, reactive oxygen species (ROS), and different antioxidants in the cryopreservation of bovine semen. Further, the kinetics of lipid peroxidation, ROS, and antioxidants on repeated semen collection under short ejaculatory abstinence were studied. We designed a comparative study where bulls were grouped into good and low freezable semen groups (Freeze-groups) based on their post-thaw motility. All the bulls included had similar initial motility and qualified minimum standards for initial semen parameters viz. semen volume and sperm concentration. The present study detected a higher lipid peroxidation and ROS viz. superoxide anions (•O2-) and a lower total antioxidant capacity (TAC) in the low freeze-group compared to the good freeze-group. The ROS and antioxidants showed unique kinetics on repeated semen collection at short intervals, and no significant change was detected in semen volume, sperm motility, and sperm concentration. This study detected higher head abnormalities and poor acrosome integrity in the low freeze-groups. The present study results indicated that the sperm head might be the most vulnerable part of the sperm to cryopreservation stress. The present study finds significantly higher lipid peroxidation and ROS levels and reduced antioxidant capacity as the primary reasons for low cryopreservability. Further, repeated semen collection with a shorter or lack of abstinence does not impose any significant change in the semen volume and sperm concentration; moreover, it could be beneficial for higher antioxidant levels and lower lipid peroxidation levels. As seminal plasma has both inhibitory and stimulatory roles in sperm function and cryopreservation, identifying the critical role players of seminal plasma and identifying sperm related changes in cryopreservation could predict the cryopreservability potential of semen.

Effect of automatic cluster remover settings on milkability, milk quality and milking irregularities of crossbred cows.

Automatic cluster remover (ACR) settings regulate the end of milking by detaching the clusters based on milk flow dropping below a preset level, which needs to be standardised for different breeds of dairy animals based on their production. A study was conducted to find out the best ACR setting for milking Indian crossbred cows based on milkability, milking irregularities and milk quality. Fifty six crossbred dairy cows in lactations 1 to 4 were categorised into three groups based on the level of production; low (N = 16; 18 kg/d). The ACR settings tested were 0.1, 0.2, 0.3 and 0.4 kg/min, keeping the vacuum level and pulsation settings constant. The ACR settings significantly (P < 0.01) affected the milk yield at all levels of production with a significant effect (P < 0.01) on machine-on time at 0.4 kg/min. The yield during the first 2 min of milking, average flow and peak flow rates were not affected at any level of production. The average electrical conductivity in milk was significantly (P < 0.01) lower for the low and medium yield cows without affecting the mean somatic cell count. At 0.4 kg/min, more cluster reattachments were needed because of significant amount of milk remaining in the udders post-cluster removal.