Browsing by Author "Yilmazbas-Mecitoglu, G."

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Comparing Conception Rate of the Repeat Breeder Vs. Normal Dairy Cows Following a Combined Treatment Protocol During the Warm Season
(Wiley-blackwell Publishing, inc, 2010) Keskin, A.; Yilmazbas-Mecitoglu, G.; Gumen, A.; Karakaya, E.; Cevik, S.; Okut, H.
Comparison of Responses To Ovsynch Between Holstein-Friesian and Swedish Red Cows
(Elsevier Science inc, 2011) Keskin, A.; Yilmazbas-Mecitoglu, G.; Gumen, A.; Karakaya, E.; Celik, Y.; Okut, H.; Wiltbank, M. C.
The Ovsynch protocol was designed to synchronize ovulation, thereby allowing timed artificial insemination (TAI) of all cows without detection of estrus. However, the effectiveness of Ovsynch in different breeds of dairy cows has not been previously compared. The aim of this study was to compare the response to Ovsynch in cycling lactating Holstein-Friesian (HF) and Swedish Red (SR) dairy cows. A total of 495 cyclic cows (n = 347 HF, n = 148 SR) were housed together and treated with Ovsynch (GnRH - 7 d - PGF(2 alpha) - 56 h - GnRH - 16 to 18 h - TAI). Ovulatory responses, synchronization rate, maximal follicle size at the time of AI, and percentage of pregnant cows per AI (P/AI at 31 and 62 d after AI) were compared between breeds. Ultrasonography was performed during Ovsynch at first GnRH, PGF(2 alpha), at time of AI, and 7 d after AI. Ovulatory response and synchronization rate were similar in HF versus SR cows (60.2 vs. 62.2%; 88.4 vs. 88.5%, respectively). Cows that ovulated to the first GnRH of Ovsynch had smaller follicle size at AT (15.9 +/- 0.1 vs. 16.4 +/- 0.2 mm). Maximal follicle size at AT was greater for HF (16.4 +/- 2.2 mm) than SR (15.5 +/- 2.3 mm) cows. The P/AI was greater for SR than HF cows at the 62-d pregnancy diagnosis (56.1 vs. 46.1%). In addition, pregnancy loss between 31 and 62 d of pregnancy was greater in HF (10.1%) than SR (3.5%) cows. Fertility was less in HF cows during the hot season (57.7 in cold vs. 38.1% in the hot season), whereas such a decrease was not observed in SR (60.0 in cold vs. 53.5% in the hot season) cows. Thus, although the GnRH treatments of Ovsynch were equally effective in SR and HF cows, pregnancy outcomes (P/AI at d 62 and pregnancy survival) were greater in SR than HF cows, and P/AI in SR cows was not compromised during the hot season as was found for HF cows.
Comparison of Responses To Ovsynch for Holstein-Friesian and Swedish-Red Cows
(Elsevier Science inc, 2010) Keskin, A.; Yilmazbas-Mecitoglu, G.; Gumen, A.; Karakaya, E.; Celik, Y.; Okut, H.; Wiltbank, M. C.
Conception Rate After Timed Artificial Insemination Protocols Using by Pgf2α and Gnrh in Dairy Heifers
(Wiley-blackwell, 2010) Gumen, A.; Keskin, A.; Yilmazbas-Mecitoglu, G.; Karakaya, E.; Alkan, A.; Guzeloglu, A.; Okut, H.
Effect of Hcg Vs. Gnrh at the Beginning of the Ovsynch on First Ovulation and Conception Rates in Cyclic Lactating Dairy Cows
(Elsevier Science inc, 2010) Keskin, A.; Yilmazbas-Mecitoglu, G.; Gumen, A.; Karakaya, E.; Darici, R.; Okut, H.
Ovulatory response to the first GnRH of Ovsynch is a very important factor for determining the outcome of a successful synchronization. The aim of the present study was to develop a protocol to increase the percentage of cows that ovulated in response to the first administration of Ovsynch. This study was designed to compare ovulation rates in response to GnRH or hCG at the beginning of Ovsynch and to evaluate the effects of this manipulation on pregnancy. Cows (n = 371) with corpus luteum (CL) and at least one follicle greater than 10 mm diameter size on either ovary were included in the study. Cows were divided into two groups. The Ovsynch protocol began with GnRH (10 mu g) in the GPO group (n = 161; GnRH-7d-PGF2 alpha-56h-GnRH-18h-AI), whereas in the HPG group, the first GnRH of the Ovsynch was replaced with 1500 IU hCG (n = 210; hCG-7d-PGF2 alpha-56h-GnRH-18h-AI). Ovarian ultrasonography was performed at the times of GnRH or hCG and of PGF2 alpha administration, at the time of artificial insemination (AI) and seven days after Al, to determine ovulation. Maximal follicle size at the beginning of the Ovsynch did not affect on response to the first GnRH/hCG treatment. Conception rate (31 d) was 0.6 times more likely to be higher (P < 0.001) in cows that responded to the first hormonal administration of Ovsynch than in those that did not respond (95% CI = 0.29-0.71). Conception rate was found to be different between the HPG (37.6%, 79/210) and the GPO groups (48.4%, 78/161). Thus, beginning of the Ovsynch protocol with hCG did not increase ovulation and conception rate in lactating dairy cows, suggesting that hCG is not a suitable replacement of the first GnRH of Ovsynch. However, our results do show that increasing the ovulation rate in response to the first hormonal administration of Ovsynch can have a significant effect on conception rate. (C) 2010 Elsevier Inc. All rights reserved.
Effect of Post-Ai Cephapirin on Conception Rate in Repeat Breeder Cows
(Wiley-blackwell Publishing, inc, 2010) Yilmazbas-Mecitoglu, G.; Keskin, A.; Karakaya, E.; Gumen, A.; Celik, Y.; Okut, H.
The Effect of Preovulatory Follicle Size at the Time of Insemination on Pregnancy in Lactating Dairy Cows
(Wiley-blackwell, 2011) Keskin, A.; Yilmazbas-Mecitoglu, G.; Karakaya, E.; Celik, Y.; Okut, H.; Gumen, A.; Wiltbank, M.
Effect of Presynchronization Strategy Before Ovsynch on Fertility at First Service in Lactating Dairy Cows
(Elsevier Science inc, 2012) Gumen, A.; Keskin, A.; Yilmazbas-Mecitoglu, G.; Karakaya, E.; Alkan, A.; Okut, H.; Wiltbank, M. C.
The aim of this study was to evaluate the effect of presynchronization with or without the detection of estrus on first service pregnancy per artificial insemination (P/AI) and on Ovsynch outcome in lactating dairy cows. A total of 511 cows were divided randomly but unevenly into 3 treatment groups at 44 to 50 days in milk (DIM). Ovsynch was started at the same time (69 to 75 DIM) in all three groups. Cows in the Ovsynch group (CON, N = 126) received no presynchronization before Ovsynch, and all cows were bred by timed AT (TAI). Cows in the presynchronization with estrus detection (PED) and the presynchronization with only TAI (PTAI) groups received two doses of prostaglandin F-2 alpha (PGF) 14 days apart, starting at 44 to 50 DIM. Ovsynch was initiated 11 days after the second PGF treatment. Cows in the PED group (N = 267) received AI if estrus was detected after either PGF injection. Cows that were not determined to be in estrus after PGF injection received Ovsynch and TAI. Cows in the PTAI group (N = 118) were not inseminated to estrus, with all cows receiving TAI after Ovsynch. The ovulatory response to the first GnRH injection administered as part of Ovsynch differed (P = 0.002) among treatment groups (83.1% in PTAI, 72.6% in PED, and 62.7% in CON). However, the ovulatory response to the second injection of GnRH during Ovsynch did not differ among treatment groups. Of the 267 PED cows, a total of 132 (49.4%) exhibited estrus and were inseminated. The P/AI at the 31-day pregnancy diagnosis was similar between the cows in the PED group with AI after estrus detection (37.9%; 50/132) and those bred with TAI (34.1%; 46/135). The P/AI in the CON group (46.8%; 59/126) was greater (P < 0.05) than that in the PED group (36.0%; 96/267). In addition, the P/AI in the CON group was greater (P = 0.04) than that in the PED cows receiving TAI (34.1%; 46/135) but less than that in the PED cows bred to estrus (37.9%; 50/132) (P = 0.16). At the 31-day pregnancy diagnosis, the cows in the PTAI group had greater P/AI (55.9%; 66/118) than both those in the PED group (P < 0.01; either estrus or TAI) and those in the CON group (P = 0.08). Thus, presynchronization with PGF (PTAI) increased the ovulatory response to Ovsynch and improved P/AI in dairy cows. Interestingly, the breeding of cows to estrus during presynchronization reduced fertility to the TAI and overall fertility, including cows bred to estrus and TAI. These results indicate that maximal fertility is obtained when all cows receive TAI after the presynchronization protocol. (C) 2012 Elsevier Inc. All rights reserved.
Effects of Presynchronization With Gonadotropin-Releasing Hormone-Prostaglandin F2α or Progesterone Before Ovsynch in Noncyclic Dairy Cows
(Elsevier Science inc, 2012) Yilmazbas-Mecitoglu, G.; Karakaya, E.; Keskin, A.; Alkan, A.; Okut, H.; Gumen, A.
The aim of this study was to evaluate the efficiency of presynchronization with GnRH and PGF(2 alpha) or with progesterone on overall Ovsynch (OVS) outcomes in noncyclic dairy cows. Cows were scanned 7 d apart with ultrasonography to determine cyclicity. Noncyclic cows (n = 281; no corpus luteum on ovaries at both examinations) were randomly divided into 3 groups. In the GP group (n = 108), the cows received GnRH and PGF(2 alpha) (PGF) administrations 7 d apart, and OVS was started 11 d after PGF (GnRH-7 d-PGF-11 d-OVS). In the P4 group (n = 90), the cows were treated for 7 d with an intravaginal progesterone (P4) implant (PRID), and then OVS was started 11 d after removal of the implant (7 d PRID-11 d-OVS). The control group (CON, n = 83) did not receive any presynchronization, and OVS was started at the same time as in the other groups (18 d-OVS). The percentage of cows that became cyclic at the beginning of OVS was lower in the CON group (38.6%; 32/83) than in the presynchronization groups (66.7%, 72/108 in GP; 71.1%, 64/90 in P4). The response to the first GnRH of OVS did not differ among groups (63.9%, 53/83 in CON; 67.6%, 73/108 in GP; 63.3%; 57/90 in P4), and synchronization rates were similar among the groups (74-82%). The cows that responded to presynchronization treatments (GP or P4) had higher pregnancy per artificial insemination (P/AI) than did nonresponding cows. Pregnancy per AI at 31 d did not differ between groups (30.1%, 25/83 in CON; 43.5%, 47/108 in GP; and 35.6%, 32/90 in P4). However, CON cows (24.1%, 20/83) had lower P/AI at 62 d than GP cows (41.7%, 45/108). Embryonic loss was higher in CON (20%, 5/25) compared with the P4 group (3%, 1/32). The administration of GnRH followed by PGF or exogenous progesterone (PRID) similarly increased the percentage of cows that became cyclic before Ovsynch in noncyclic cows, but fertility did not improve. However, the cows that responded to presynchronization had higher fertility rates than the nonresponding cows.
Effects of Presynchronizations With Gnrh/Pgf2α Vs. Progesterone Before Ovsynch in Noncyclic Dairy Cows
(Elsevier Science inc, 2010) Yilmazbas-Mecitoglu, G.; Keskin, A.; Gumen, A.; Karakaya, E.; Darici, R.; Okut, H.
Effects of Reducing Interval From Gnrh To Pgf2α in Ovsynch Protocol on Pregnancy Rate in Cyclic Lactating Dairy Cows
(Elsevier Science inc, 2010) Gumen, A.; Yilmazbas-Mecitoglu, G.; Keskin, A.; Karakaya, E.; Celik, Y.; Okut, H.