Browsing by Author "Souza, Alexandre H."
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Item Lack of complete regression of the Day 5 corpus luteum after one or two doses of PGF2α in nonlactating Holstein cows(Elsevier Science, 2014-02-01) Nascimento, Aníbal Ballarotti; Souza, Alexandre H.; Filho, Roberto Sartori; Wiltbank, Milo Charles; Keskin, Abdülkadir; Uludağ Üniversitesi/Veterinerlik Fakültesi/Klinik Bilimler Bölümü.; AAH-3831-2021; 24473229800The early corpus luteum (CL) (before Day 6) does not regress after a single PGF(2 alpha) treatment. We hypothesized that increasing PGF(2 alpha) dose or number of treatments would allow regression of the early CL (Day 5). Nonlactating Holstein cows (N = 22) were synchronized using the Ovsynch protocol. On Day 5 (Day 0 = second GnRH treatment), cows were assigned to: (1) control (N = 5): no further treatment; (2) 1PGF (N = 6): one dose of 25 mg PGF(2 alpha); (3) 2PGF (N = 5): two doses of 25 mg PGF(2 alpha) (50 mg) given 8 hours apart (second PGF(2 alpha) on Day 5 at the same time as the other PGF(2 alpha) treatments); (4) DPGF (N = 6): double dose of 25 mg PGF(2 alpha) (50 mg) given on Day 5. Blood samples were collected to monitor progesterone (P4) profiles in two periods. In the first period (0 to 24 hours), there were effects of treatment (P = 0.01), time (P < 0.01), and an interaction of treatment and time (P = 0.02). Group 1PGF versus control was different only at 12 hours (P = 0.02). Cows treated with DPGF were different than control at 4 hours (P = 0.04), 12 hours (P < 0.01), and 24 hours (P < 0.01). Only cows treated with 2PGF had lower P4 than control during the entire period and low P4(0.37 +/- 0.17 ng/mL) at 24 hours, usually indicative of luteolysis. In the second period (Day 5 to 15 of the cycle), there were effects of treatment (P < 0.01), time (P < 0.01), and interaction of treatment and time (P = 0.002). Group 1PGF was not different than control from Day 5 to 13 and P4 was greater than control on Day 14 (P = 0.01) and 15 (P < 0.01). Circulating P4 in DPGF cows was lower than control from Day 7 (P = 0.05) through 12 (P < 0.01). Likewise, there were differences between control and 2PGF from Day 7 to 13, but not on Day 14 and 15. On Day 15, all PGF(2 alpha)-treated groups had circulating P4 consistent with an active CL. Ultrasound evaluation confirmed that no CL from any group completely regressed during the experiment and no new ovulations occurred to account for functional CL later in cycle. In summary, a double dose of PGF(2 alpha) (twice on Day 5 or 8 hours apart) can dramatically decrease P4, consistent with classical definitions of luteolysis; however, these CL recover and become fully functional. Thus, the Day 5 CL of mature Holstein cows do not regress even to two doses of PGF(2 alpha).Item Managing the dominant follicle in high-producing dairy cows(Nottingham University, 2010) Wiltbank, Milo Charles; Filho, Roberto Sartori; Vasconcelos, José Luiz Moraes; Nascimento, Aníbal Ballarotti; Souza, Alexandre H.; Cunha, A. P.; Sangsritavong, Siwat; Guenther, Jerry N.; Lopez, Hernando; Pursley, James Richard; Gümen, Ahmet; Uludağ Üniversitesi/Veterinerlik Fakültesi/Klinik Bilimler Bölümü.; AAH-1406-2021; 6602393069Reduced reproductive efficiency has been reported in high-producing dairy cows. Sources of reproductive inefficiency include decreased expression of estrus, increased diameter of the ovulatory follicle and reduced fertility when cows are inseminated after estrus, increased incidence of double ovulation and twinning, and increased pregnancy loss. To overcome some of these inefficiencies, reproductive management programs have been developed that synchronize ovulation and enable effective timed artificial insemination (AI) of lactating dairy cows. Effective regulation of the corpus luteum (CL), follicles, and hormonal environment are critical for optimizing these programs. Recent programs, such as the 5-day CIDR program, Double-Ovsynch, G-6-G, and estradiol benzoate-CIDR programs were designed to more effectively control one or more physiological events. These events include synchronization of a new follicular wave at the beginning of the program, optimization of the circulating progesterone (P4) concentrations and duration of follicular dominance, optimized reductions in P4 and increases in circulating estradiol (E2) concentrations during the preovulatory period, and tightly synchronized ovulation of a follicle of optimal size and fertility for implementation of timed AI. The success of these programs has been remarkable, although there is substantial variability in effectiveness due to environmental, management, nutritional, genetic, and disease factors as well as potential variability in some aspects of reproductive physiology among commercial dairy farms. Future programs will optimize the reproductive physiology while simplifying the protocol implementation and also match specific reproductive management protocols to specific farms and even specific cows (for example primiparous vs. multiparous).Item Managing the dominant follicle in lactating dairy cows(Elsevier Science, 2011-12) Wiltbank, Milo Charles; Filho, Roberto Sartori; Herlihy, Mary M.; Vasconcelos, José Luiz Moraes; Nascimento, Aníbal Ballarotti; Souza, Alexandre H.; Ayres, Henderson; Cunha, A. P.; Guenther, Jerry N.; Keskin, Abdülkadir; Gümen, Ahmet; Uludağ Üniversitesi/Tıp Fakültesi/Kadın Hastalıkları ve Doğum Anabilim Dalı.; AAH-1406-2021; AAH-3831-2021; 24473229800; 6602393069Reproductive efficiency is not optimal in high-producing dairy cows. Although many aspects of ovarian follicular growth in cows are similar to those observed in heifers, there are numerous specific differences in follicular development that may be linked with changes in reproductive physiology in high-producing lactating dairy cows. These include: I) reduced circulating estradiol (E2) concentrations near estrus, 2) ovulation of follicles that are larger than the optimal size, 3) increased double ovulation and twinning, and 4) increased incidence of anovulation with a distinctive pattern of follicle growth in anovular dairy cows. The first three changes become more dramatic as milk production increases, although anovulation has not generally been associated with level of milk production. To overcome reproductive inefficiencies in dairy cows, reproductive management programs have been developed to synchronize ovulation and enable the use of timed AI in lactating dairy cows. Effective regulation of the CL, follicles, and hormonal environment during each part of the protocol is critical for optimizing these programs. This review discusses the distinct aspects of follicular development in lactating dairy cows and the methodologies that have been utilized in the past two decades in order to manage the dominant follicle during synchronization of ovulation and timed AI programs.Item The profile of circulating FSH and follicular dynamics in beef heifers that are carriers of an allele for high fecundity(Oxford University, 2011-06) Bastos, Michele R.; Meschiatti, Murillo A. P.; Souza, Alexandre H.; Peters, Tonia L.; Morris, Chris A.; Kirkpatrick, Brian W.; Wiltbank, Milo C.; Mecitoğlu, Gülnaz Yılmazbaş; Uludağ Üniversitesi/Veterinerlik Fakültesi/Veterinerlik Doğum ve Jinekolojisi Anabilim Dalı.; 0000-0003-2817-3221; AAG-4440-2019Item Supplementation with estradiol-17 beta before the last gonadotropin-releasing hormone injection of the ovsynch protocol in lactating dairy cows(Elsevier Science, 2007-10) Souza, Alexandre H.; Silva, E.; Cunha, Arcelina Pacheco; Guenther, J. N.; Peto, C. M.; Caraviello, D. Z.; Wiltbank, Milo C.; Gümen, Ahmet; Uludağ Üniversitesi/Veteriner Fakültesi/Doğum ve Jinekoloji Anabilim Dalı.; 6602393069The aim of this study was to determine whether an increase in circulating estrogen concentrations would increase percentage pregnant per artificial insemination (PP/AI) in a timed AI protocol in high-producing lactating dairy cows. We analyzed only cows having a synchronized ovulation to the last GnRH of the Ovsynch protocol (867/1,084). The control group (n = 420) received Ovsynch (GnRH - 7 d - PGF2α - 56 h - GnRH -16 h - timed AI). The treatment group (n = 447) had the same timed AI protocol with the addition of 1 mg of estradiol-17β (E2) at 8 h before the second GnRH injection. Ovarian ultrasound and blood samples were taken just before E2 treatment of both groups. In a subset of cows (n = 563), pressure-activated estrus detection devices were used to assess expression of estrus at 48 to 72 h after PGF2α treatment. Ovulation was confirmed by ultrasound 7 d after timed AI. Treatment with E2 increased expression of estrus but overall PP/ AI did not differ between E2 and control cows. There was an interaction between treatment and expression of estrus such that PP/AI was greater in E2-treated cows that showed estrus than in E2-treated or control cows that did not show estrus and tended to be greater than control cows that showed estrus. There was evidence for a treatment by ovulatory follicle size interaction on PP/AI. Supplementation with E2 improved PP/ AI in cows ovulating medium (15 to 19 mm) but not smaller or larger follicles. The E2 treatment also tended to improve PP/AI in primiparous cows with low (S2.5) body condition score, and in cows at first postpartum service compared with Ovsynch alone. In conclusion, any improvements in PP/AI because of E2 treatment during a timed AI protocol appear to depend on expres sion of estrus, parity, body condition score, and size of ovulatory follicle.