Holistic vision of dairy herds: reproductive management, timed-artificial insemination programs, nutrition and heat stress

• Ano de defesa: 2023
• Autor(a) principal: Consentini, Carlos Eduardo Cardoso
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Dairy cow; Estresse térmico; Fertilidade; Fertility; Heat stress; Inseminação artificial em tempo fixo; Nutrição; Nutrition; Timed-artificial insemination; Vaca leiteira
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/11/11139/tde-05022024-100715/

The objective of this PhD dissertation was to address different aspects that affect reproductive performance of dairy herds. The first chapter is a review that discusses how reproductive management affects reproduction, presenting strategies for the first postpartum service and re-inseminations. In addition, the review discusses key points that affect fertility of timed-artificial insemination (TAI) programs, such as promoting follicular wave emergence at the beginning of the protocols, high concentration of progesterone (P4) during preovulatory follicle development, and the importance of the hormonal environment in the periovulatory period and post-ovulation. Furthermore, the review discusses how nutrition, genetics, heat stress, body condition score, health and the transition period affect reproductive performance. The second chapter involves an experiment in which two pre-synchronization strategies and two TAI protocols were compared, establishing four reproductive programs for the first TAI postpartum. Despite the difference on pharmacological bases, the reproductive programs promoted similar results and high fertility, and the results showed a same efficiency of an established program, Double-Ovsynch, compared with the novel program developed by our research group, Double E-Synch. In the study of chapter 3, optimizations during the estradiol (E2) plues P4-based TAI protocol were evaluated, and we observed an increase in fertility when a treatment with gonadotropin-releasing hormone (GnRH) was added at the beginning of the conventional protocol initiated with only E2 benzoate. Chapter 4 includes an article in which information related to nutrition and reproduction from commercial dairy herds was retrospectively evaluated. These are field data that suggested that diets with a high concentration of non-fiber carbohydrates in early lactation may have a negative effect on fertility and reproductive performance in high production commercial dairy farms. The fifth chapter discusses another important factor that affects fertility, heat stress. Data were collected during one year on a commercial farm and the results confirmed negative effects on fertility of variables associated with heat stress, such as rectal temperature at the time of AI, season of the year and temperature and humidity index (THI). Finally, we conclude that it is important for farms and professionals to have a holistic vision within the herd, looking for to understand and control factors that affect fertility, in addition to implementing optimized TAI programs and effective reproductive management strategies to guarantee high service rates and fertility, aiming to achieve high reproductive efficiency with high milk production.