Impacts of supplementation and confinement feeding before the breeding season in Nellore Bulls on semen characteristics and in vitro fertilization

• Grant number: 24/07701-9
• Support Opportunities: Regular Research Grants
• Start date: February 01, 2025
• End date: January 31, 2027
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Nutrition and Feeding
• Principal Investigator: Arlindo Saran Netto
• Grantee: Arlindo Saran Netto
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil
• Associated researchers: Carl Robertson Dahlen ; Germán Darío Ramírez Zamudio ; Guilherme Pugliesi ; Juliano Coelho da Silveira ; Juliano Rodrigues Sangalli ; Maíra Bianchi Rodrigues Alves ; Miguel Henrique de Almeida Santana ; Paulo Fantinato Neto ; Paulo Roberto Leme ; Samat Amat ; Saulo da Luz e Silva

Abstract

Despite advancements in reproductive biotechnology and genetic selection, reproductive challenges affect Brazilian beef cattle. It is known that nutrition influences the quality of bull semen, with molecular and microbiological impacts that are crucial for fertility. These factors directly affect reproductive efficiency, highlighting the need for new strategies to optimize reproductive outcomes. This proposal aims to investigate how different nutritional systems before the breeding season can affect the fertility of Nelore bulls. It will focus on the microbiome, metabolome, and abundance of microRNAs in sperm and their effects on in vitro embryo fertilization. Forty-two young Nelore bulls, approximately 450 kg and 20 months old, will be distributed in a randomized block design and subjected to three treatments, with 14 bulls per treatment. The blocks within each treatment will be formed based on body weight, body condition score, and previous evaluation of sperm quality. The treatments will consist of a control group (CON) receiving 0.25 g/kg of body weight in mineral salt and kept on pasture; a supplemented group (SUP), with an offer of 1 g/kg of the body weight and kept on pasture; and a confined group (FLT) fed a 40:60 diet of corn silage and concentrate. The CON and SUP groups will be kept in separate Urochloa spp. paddocks by treatment. The diets for the SUP and FLT groups will be formulated to achieve an approximate weight gain of 0.800 kg and 1.700 kg per day over a total period of 112 days, respectively. During the experimental period, the bulls will be weighed every 14 days to monitor that the weight gain of the three treatments is within the target proposed in this research. At the beginning of the experimental period, and on days 56 and 112, carcass ultrasonography will be performed, registering the area and subcutaneous fat thickness of the Longissimus and the subcutaneous fat thickness under the Biceps femoris. Additionally, on the same days of the ultrasonographic evaluation, samples of semen, blood, and feces will be collected from each animal. Semen analyses will include sperm quality, microbiome, metabolome, and determination of the abundance of microRNAs. As for the feces samples, microbiome analyses will be performed, and metabolites and hormones will be measured in the blood. Subsequently, a semen aliquot from each bull will be reserved for in vitro fertilization assays, where cleavage rates, blastocyst rates, and embryo classification will be analyzed. After the experimental period, all bulls will be slaughtered, all parts of the reproductive tract will be weighed, and samples from the testicles and vesicular glands will be collected for microbiome analyses. Furthermore, samples from the testicles, vesicular glands, and portions of the epididymis's caput, corpus, and cauda will be collected for histological analyses. However, this study aims to expand the understanding of how bull nutrition can affect semen quality at a molecular and microbiological level and how this can impact fertility. With this knowledge, nutritional alternatives that can minimize the impacts of reproductive failures will be presented, which is a challenge in beef cattle farming. (AU)