The comparative intensity of estrus in spontaneous and synchronized estrus is depicted in Table 3. The intense type of intensity of estrus was higher in induced estrus cows as compared to spontaneous estrus cows. The results are non-significant (p<0.05) between the groups. The intense type of intensity of estrus was non significantly higher in induced estrus cows as compared to spontaneous estrus cows are in agreement with
Shahid et al., (2019), Alves et al., (2009) and
Landaeta et al., (2002) reported higher intensity of estrus in induced cows as compared with spontaneous cows in Non-Descript, Guzera and Angus breed of cows, respectively. In contrast,
Singh et al., (2020) reported higher estrus intensity in spontaneous cows as compared to induced cows, which is not in agreement with present findings.
A slightly better intensity of estrus observed in present study with induced estrus in cows might be due to the reason that GnRH injection at day 0 might have resulted in synchronous follicular emergence and timely follicular development at the start of treatment. Thus, amore finely delineated endocrine regulation might have induced a wave of follicular development. Low intensity of estrus is a limiting factor in the use of AI and other reproductive management techniques depends upon visualization of estrus. Therefore, the higher estrus intensity score achieved by estrus induction may be helpful in application of AI
(Shahid et al., 2019). Social factors could have also contributed to differences observed in the intensity of estrus between synchronized and spontaneous estruses. Synchronization of estrus increases the number of cows in estrus at particular time. Consequently, the coincidence of several cows in estrus leads to formation of sexually active groups, which promote increased mounting activity in females
(Lemaster et al., 1999).
The overall conception rate in intense and moderate + weak estrus inseminated with sexed semen were depicted in Table 4. The overall conception rate was observed higher (15.90%) with non-significant difference (p<0.05) in intense type of intensity as compared to moderate + weak type of intensity which might be due to unlike strong estrus, weak estrus has been associated with elevated progesterone levels
(Schopper et al., 1993) that exert a suppressive effect on the amplitude and the amplitude and the frequency of LH pulses in the preovulatory period
(Savio et al., 1993). A shortened duration of estrus in cows with weak signs in connection with improper timing of insemination can be related to fertilization failures
(Yoshida and Nakao 2005). The overall difference in first service conception rate observed in intense and Moderate + weak estrus is in accordance with
Mallory et al., (2013) reported pregnancy rate with sexed semen in heifers that displayed estrus after synchronization by 20% points higher compared to those that did not express apparent signs.
In present study, the higher first service conception rate was observed in spontaneous estrus cows compared to the synchronized cows with overall first service conception rate 39.28%. The overall proportion of female calves born was 90.90% (Table 5). The first service conception rate observed after inseminated with sexed semen in spontaneous estrus was higher (7.14%) as compared with induced estrus with non-significant (p<0.05) difference. The non significant (p<0.05) higher first service conception rate observed in spontaneous estrus compared to induced estrus might be due to the larger number of ovulations that occurred within the time appropriate for sexed sperm. The tendency towards interaction between the bull and the type of estrus is in accordance with the decreased conception rate related to the use of sexed semen for synchronized services compare to non-synchronized services
(Abdel-Azim 2010).
The non-significant difference observed in conception rate in induced and spontaneous estrus cows inseminated with sexed semen is in harmony with
Kurykin et al., (2017) reported 37.2 and 40.1% conception rate in spontaneous and induced estrus, respectively with non-significant difference. The lower conception rate observed in induced estrus as compared to spontaneous estrus is in agreement with
Kurykin et al., (2016) observed 41.9 and 53.4 per cent conception rates in induced and spontaneous estrus, respectively. The overall conception rate observed in present findings are in concurrence with
Kurykin et al., (2017) reported 38.6% conception rate in lactating Holstein cows.
Sharma et al., (2018) observed 40% conception rate in dairy cows inseminated with sex sorted semen.
Joshi et al., (2021) observed the overall conception rate of sex sorted semen was 39.92±0.5 percent in Indian breeds of cattle.
Norman et al., (2010) observed 39% conception rate with sexed semen in Holstein heifers.
Mallory et al., (2013) reported 38% overall conception rate in Holstein heifers inseminated with sex sorted semen.
Patel and Jethva (2019) observed 39.53% pregnancy rate in crossbred (HF x Gir) heifers.
DeJarnette et al., (2011) observed 38% conception rates in Holstein heifers using 2.1 x 106 concentration of sex sorted semen and
Rhinehart et al., (2011) observed 38% conception rates in heifers inseminated with sexed semen.
Shinde et al., (2021) reported 40% conception rate with sex sorted semen in Gir cows. The overall female calves born observed in present study are in concurrence with
Shekalgorabi et al., (2017) reported 91.1% female calves in Holstein heifers using sexed semen.
Joshi et al., (2021) observed 90.9% female calve by using sex sorted semen in Indian cattle breeds.
Seidel et al., (2008) observed 92% female calves using sexed sperms in Angus cows.
Frijters et al., (2009) observed 91.6% female calves using sexed semen.
Guner et al., (2021) observed 89.8% female calves using sex sorted semen in Holstein heifers.
Abdalla et al., (2014) observed 89.6% female calves inseminated with sexed semen in Holstein heifers.
The effect of days in milk on pregnancy rate in spontaneous and induced estrus was depicted in Table 6. The conception rate is higher in 60-100 days in milk as compared to 101-150 days in milk with non-significant (p<0.05) difference. The higher conception rate observed in above 60 days in milk are in concurrence with
DeJarnette et al., (2010) and
Maicas et al., (2020) stated that conception rate of cows inseminated at above 60 days in milk has greater conception rate compared to below 60 days in milk.
The present finding regarding conception rate observed in 101-150 days in induced estrus is similar with
Kurykin et al., (2017) reported 37.4% conception rate in induced estrus cows. Thus targeting the use of sexed semen to elite cows based on days in milk at insemination highlighted as suitable criteria for identifying lactating cows suitable for insemination with sex sorted sperm.
(Maicas et al., 2020).
The parity wise pregnancy rate in spontaneous and induced estrus was depicted in Table 7. From the present study it was observed that as the parity increases the conception rate decreases with non-significant difference. Difference in fertility between primiparous and multiparous cows may depend on differences in milk yield, energy balance and metabolic changes. Greater energy demands for milk synthesis may increase the risk of fertility influencing problems due to the higher susceptibility of high producing cows to metabolic and endocrine disorders
(Chebel et al., 2004). The decrease in conception rate as parity increases of sexed semen in present study are in accordance with
DeJarnette et al., (2008), Kurykin et al., (2017), Maicas et al., (2019), Maicas et al., (2020), reported decrease in conception rate as parity increases.
The conception rate observed in second parity cows inseminated with sexed semen in spontaneous estrus is in harmony with the findings reported by
Kurykin et al., (2017) reported 35.6 percent conception rate in second parity lactating HF cows inseminated with sexed semen. The present findings regarding conception rate observed in first parity in induced estrus cows is in accordance with
Maicas et al., (2019) observed 45.2% conception rate in first parity with sex sorted sperm in induced estrus. The present findings regarding conception rate observed in second parity in induced estrus cows is in accordance with
DeJarnette et al., (2008) and
Karakaya et al., (2014) reported 31.3 and 33.3% conception rate in second parity with sexed and sex sorted semen, respectively in cows.