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    EFFECT OF TIMING OF ARTIFICIAL INSEMINATION RELATIVE TO SPONTANEOUS ESTRUS ON REPRODUCTIVE PERFORMANCE AND CALF GENDER RATIO IN REPEAT BREEDER HOLSTEIN COWS
    (Pakistan Agricultural Scientists Forum, 2016) Bayril, T.; Yilmaz, O.; Cak, B.
    This study was conducted to investigate the effect of the interval between the onset of spontaneous estrus and artificial insemination (AI) on reproductive performance and calf sex ratio in repeat breeder Holstein cows. Two hundred eighty lactating Holstein cows were used in this study. The animals were artificially inseminated at different times (0-6, 7-12, 13-18, or 19-24 h) after the onset of spontaneous estrus. Reproductive performance did not differ between cows inseminated at 0-6 h (n = 70), 7-12 h (n = 70), 13-18 h (n = 70), or 19-24 h (n = 70) after the onset of estrus [pregnancy rate: 0-6 h, 57.1%; 7-12 h, 65.7%; 13-18 h, 54.3%; and19-24 h, 62.9%; embryonic mortality rate: 0-6 h, 8.5%; 7-12 h, 5.7%; 13-18 h, 5.7%; and19-24 h, 7.1%; calving rate: 0-6 h, 48.6%; 7-12 h, 60%; 13-18 h, 48.6%; and19-24 h, 55.7%; twinning rate: 0-6 h, 2.9%; 7-12 h, 0%; 13-18 h, 5.7%; and 19-24 h 2.9%; and calf sex ratio (F/M): 0-6 h, 64/36%; 7-12 h, 48/52%; 13-18 h, 42/58%; and19-24 h, 46/54%; P>0.05]. In general, pregnancy rates of the groups inseminated at different postpartum times differed (P<0.01) and were higher in the group inseminated at >151 days postpartum. Pregnancy rates were similar in groups inseminated in the second and third parities, but were lower in the group inseminated in the fourth parity. In conclusion, rates of pregnancy, embryonic mortality, calving, and twinning of repeat breeder Holstein cows did not differ between cows subjected to AI at different times after the onset of spontaneous estrus. The timing of AI in repeat breeder cows did not influence the calf sex ratio. Pregnancy rate of repeat breeder cows was influenced by postpartum time and parity number.
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    The Technical and Financial Effects of Parenteral Supplementation with Selenium and Vitamin E during Late Pregnancy and the Early Lactation Period on the Productivity of Dairy Cattle
    (Asian-Australasian Assoc Animal Production Soc, 2015) Bayril, T.; Yildiz, A. S.; Akdemir, F.; Yalcin, C.; Kose, M.; Yilmaz, O.
    This study aimed to determine the effects of parenteral selenium (Se) and vitamin E supplementation on economic impact, milk yield, and some reproductive parameters in high-yield dairy cows in the dry period and in those at the beginning of lactation. At the beginning of the dry period, cows (n = 323) were randomly divided into three groups as follows: Treatment 1 (T1), Treatment 2 (T2), and Control (C). Cows in group T1 received this preparation 21 days before calving and on calving day, and cows in group T2 received it only on calving day. The cows in the control group did not receive this preparation. Supplementation with Se increased Se serum levels of cows treated at calving day (p<0.05). Differences in milk yield at all weeks and the electrical conductivity values at the 8th and 12th weeks were significant (p<0.05). Supplementation with Se and Vitamin E decreased the incidence of metritis, the number of services per conception and the service period, but had no effects on the incidence of retained fetal membrane. A partial budgeting analysis indicated that Se supplementation was economically profitable; cows in group T1 averaged 240.6$ per cow, those in group T2 averaged 224.6$ per cow. Supplementation with Se and Vitamin E has been found to increase serum Se levels, milk yield, and has positive effects on udder health by decreasing milk conductivity values and incidence of sub-clinical mastitis.