Browsing by Author "Cunha, A. P."
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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.