Siddhartha Shankar Layek

Behavioural signs of estrus and their relationship to time of ovulation in Zebu (Sahiwal) cattle

The present study reports the behavioural signs of estrus, their temporal distribution and duration of expression and their relationship with the time of ovulation in zebu cattle in order to identify the reliable sign(s) of estrus that could fairly predict the ovulation time. The onset, intensity and expression of various signs of estrus were continuously recorded till ovulation in 60 Sahiwal cows. Time of ovulation was determined by ultrasound examinations at 2h interval. Estruses were mostly of moderate (52%) or weak (34%) intensity. Mucus discharge, tumefaction of vulva and reddening of vulvar mucus membrane appeared early in relation to the ovulation time (31.27±1.97, 31.05±2.98 and 30.79±2.53h, respectively) in comparison to mounting (27.67±2.33h) and standing to be mounted (25.37±2.11h). Mucus discharge, tumefaction of vulva and reddening of vulvar mucus membrane persisted significantly more duration (P<0.01) than mounting and standing to be mounted. Further these cardinal signs appeared early in relation to time of ovulation, persisted for longer duration and expressed intensely. We conclude that mucus discharge, tumefaction of vulva and reddening of vulvar mucus membrane can be good predictor ovulation in this breed of cattle.

Cryopreservation of bull semen: Evolution from egg yolk based to soybean based extenders

Since the inception of bovine semen cryopreservation, egg yolk and milk based extenders have been used to protect sperm from the detrimental effects of cooling and freezing. In recent years, demand for alternatives to conventional commercial extenders has arisen as the risk of introducing exotic diseases through transporting egg yolk based products has been recognized. Egg yolk can also interfere with sperm evaluation and the presence of particulate material in the extender may reduce fertility. Soybeans contain lecithin, a phospholipid fraction that can substitute for high molecular weight lipoprotein and phospholipids from egg yolk and prevent or ameliorate damage to the sperm plasma membrane that occurs during extension, cooling, and cryopreservation. Soy lecithin based extenders have been evaluated for processing and freezing bovine semen, although extender from soybean milk has not been studied as extensively. Commercially available soy lecithin based extenders are used increasingly but remain under scrutiny and are not universally accepted. With these observations in mind, this review is intended to examine effects of conventional cryopreservation procedures, methods of assessment, and potential for developing soybean extract as an acceptable alternative to traditional egg yolk and milk based extenders for bull sperm cryopreservation.

Testicular Cell Indices and Peripheral Blood Testosterone Concentrations in Relation to Age and Semen Quality in Crossbred (Holstein Friesian×Tharparkar) Bulls

Present study analyzed the changes in peripheral blood testosterone concentrations and testicular cytogram in relation to age and semen quality in crossbred males. Three different age groups of crossbred males viz. bull calves (6 months, n = 5), young bulls (15 months, n = 5) and adult bulls (4 to 6 years, n = 8) were utilized for the study. Testicular fine needle aspiration cytology technique was used to quantify testicular cytology and their indices. Peripheral blood testosterone concentrations were measured using enzyme-linked immunosorbent assay method. Semen samples collected from adult bulls were microscopically evaluated for quality parameters. Mean peripheral blood testosterone concentrations in bull calves, young bulls and adult bulls were 2.28±0.09 ng/mL, 1.42±0.22 ng/mL and 5.66±1.08 ng/mL respectively, and that in adult bulls were significantly different (p<0.01) from young bulls and bull calves. There was no significant difference between the proportion of different testicular cells in bull calves and young bulls. Between young and adult bulls, significant differences (p<0.01) were observed in the proportion of spermatocytes, spermatozoa, and sperm: Sertoli cell ratio. The proportions of Sertoli cells showed a significant difference (p<0.01) between the three age groups. The number of primary spermatocytes had a positive correlation with peripheral blood testosterone concentrations in bull calves (r = 0.719, p<0.01). Number of Sertoli cells per 100 germ cells was negatively correlated with blood testosterone concentration in young bulls (r = −0.713, p<0.01). Among different semen parameters in adult bulls, ejaculate volume (r = 0.790, p<0.05) had positive relationship, and sperm motility had significant negative correlation (r = −0.711, p<0.05) with testosterone concentrations. The number of Sertoli cells and Sertoli cell index had a positive correlation with various semen quality parameters (p<0.001). Results of the present study conclude that number of Sertoli cells and Sertoli cell index are good indicators of semen quality, but peripheral blood testosterone concentrations may not have a direct relationship with various seminal attributes in crossbred bulls.

BEHAVIOURAL SIGNS OF ESTRUS IN DIFFERENT PARITY OF MURRAH BUFFALOES (BUBALUS BUBALIS): A COMPARATIVE STUDY

In dairy bovines, estrus detection is the key determinant of the herd fertility. However, owing to silent heat in buffaloes, it is difficult to detect estrus at proper time which in turn affects the estrus detection efficiency and reduces conception rate. Further, it is not clear whether the buffaloes during different parities have differential expression of estrus behaviour. Therefore, the present study was designed to study the behavioural signs of estrus expressed by Murrah buffaloes (n=94) belonging to different parities. Estrus detection was done by parading teaser bulls (4 times bull parading in a day), heat expectancy chart and visual observation of behavioural signs of estrus. The study revealed significantly (PThese results indicated that intensity of bellowing/vocalization, micturition and tail raising behaviours during estrus were poorly expressed in heifers and more focussed attention is needed to detect buffalo heifers in estrus.

Effect of short-term cooling on core body temperature, plasma cortisol and conception rate in Murrah buffalo heifers during hot-humid season

The present investigation studied the effect of short-term cooling around the time of artificial insemination (AI) on body temperature, plasma cortisol and conception rate (CR) in Murrah buffalo heifers. Buffalo heifers (n = 25) were divided into two groups i.e. control group (n = 9) and short-term cooling group (n = 16). In both the groups, estrus synchronization using ovsynch protocol and fixed time AI was carried out. Heifers in short-term cooling group were kept in a specially designed air condition room from 3 h before to 3 h after AI. Blood samples were collected for estimation of cortisol and progesterone and rectal and vaginal temperatures were measured before 3 h of AI, at the time of AI and after 3 h of AI. At the time of AI and after 3 h of AI, both rectal and vaginal temperatures were significantly (P < 0.05) lower in heifers subjected to short-term cooling compared to control group. After 3 h of AI, cortisol levels were significantly (P < 0.05) higher in control group (5.023 ± 0.74 ng/ml) compared to short-term cooling group (1.061 ± 0.99 ng/ml). A trend of higher CR was observed in short-term cooling group compared to control group (68.75 vs. 33.33%, P = 0.087). It may be inferred that short-term cooling reduced the stress at the time of AI and improved the CR in Murrah buffalo heifers during hot-humid season.