A series of experiments was conducted to evaluate the effects of nutrition during calfhood (defined as the period from 10 to 26-30 wk of age) and peripubertal period (defined as the period from 27-31 to 70-74 wk of age) on sexual development and reproductive function in beef bulls. The overall objective of these experiments was to evaluate the effects of nutrition on endogenous metabolic hormones (leptin, insulin, GH, and IGF-I), gonadotropins and testosterone concentrations, sexual development, sperm production, and semen quality in bulls. The results of these experiments demonstrated that nutrition affected GnRH secretion and sexual development in bulls. Increased nutrition during calfhood resulted in a more sustained increase in LH pulse frequency during the early gonadotropin rise and greater testicular development at maturity. On the other hand, low nutrition during calfhood suppressed LH secretion during the early gonadotropin rise and resulted in delayed puberty and reduced testicular development at maturity. When low nutrition was accomplished by restricted feed intake, hypothalamic and pituitary function were compromised and LH secretion was more severely affected. Temporal associations between LH secretion patterns and circulating IGF-I concentrations implied that IGF-I is a possible signal to the central metabolic sensor involved in translating body nutritional status to the GnRH pulse generator. Nutrition also affected testicular steroidogenesis (testosterone concentrations), indicating effects on the number or function of Leydig cells, or both. Age-related increases in physiological and GnRH-stimulated circulating testosterone concentrations were hastened in bulls receiving high nutrition and delayed in bulls receiving low nutrition; these effects were probably mediated by both LH secretion and IGF-I concentrations. Circulating leptin and insulin may have only permissive roles on GnRH secretion, but may enhance testicular development. Growth hormone concentrations decreased concomitantly with increasing IGF-I concentrations during sexual development in bulls, suggesting that the testes could contribute considerable amounts of circulating IGF-I. In conclusion, management strategies to optimize reproductive function in bulls should focus on increasing nutrition during calfhood.

A series of experiments was conducted to evaluate the effects of nutrition during calfhood (defined as the period from 10 to 26-30 wk of age) and peripubertal period (defined as the period from 27-31 to 70-74 wk of age) on sexual development and reproductive function in beef bulls. The overall objective of these experiments was to evaluate the effects of nutrition on endogenous metabolic hormones (leptin, insulin, GH, and IGF-I), gonadotropins and testosterone concentrations, sexual development, sperm production, and semen quality in bulls. The results of these experiments demonstrated that nutrition affected GnRH secretion and sexual development in bulls. Increased nutrition during calfhood resulted in a more sustained increase in LH pulse frequency during the early gonadotropin rise and greater testicular development at maturity. On the other hand, low nutrition during calfhood suppressed LH secretion during the early gonadotropin rise and resulted in delayed puberty and reduced testicular development at maturity. When low nutrition was accomplished by restricted feed intake, hypothalamic and pituitary function were compromised and LH secretion was more severely affected. Temporal associations between LH secretion patterns and circulating IGF-I concentrations implied that IGF-I is a possible signal to the central metabolic sensor involved in translating body nutritional status to the GnRH pulse generator. Nutrition also affected testicular steroidogenesis (testosterone concentrations), indicating effects on the number or function of Leydig cells, or both. Age-related increases in physiological and GnRH-stimulated circulating testosterone concentrations were hastened in bulls receiving high nutrition and delayed in bulls receiving low nutrition; these effects were probably mediated by both LH secretion and IGF-I concentrations. Circulating leptin and insulin may have only permissive roles on GnRH secretion, but may enhance testicular development. Growth hormone concentrations decreased concomitantly with increasing IGF-I concentrations during sexual development in bulls, suggesting that the testes could contribute considerable amounts of circulating IGF-I. In conclusion, management strategies to optimize reproductive function in bulls should focus on increasing nutrition during calfhood.

Submitted by ROGÉRIO FONSECA GUIMARÃES PERES null (rfgperes@yahoo.com.br) on 2017-01-14T21:47:17Z No. of bitstreams: 1 OK Tese Doutorado com Ficha Catalográfica Rogerio Peres Final.pdf: 3471137 bytes, checksum: afcec40d26ee7845fa56d00b5abdc36e (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-01-17T14:03:15Z (GMT) No. of bitstreams: 1 guimaraes_rf_dr_bot.pdf: 3471137 bytes, checksum: afcec40d26ee7845fa56d00b5abdc36e (MD5) / Made available in DSpace on 2017-01-17T14:03:15Z (GMT). No. of bitstreams: 1 guimaraes_rf_dr_bot.pdf: 3471137 bytes, checksum: afcec40d26ee7845fa56d00b5abdc36e (MD5) Previous issue date: 2016-12-12 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Os hormônios metabólicos IGF-1, GH e leptina são alterados de acordo com o status nutricional dos animais. O objetivo desse trabalho foi determinar as concentrações desses hormônios em vacas paridas e novilhas Nelore entre 12 e 16 meses de idade e seus efeitos na reprodução nos experimentos do Capítulo 2. No Capítulo 3, vacas primíparas, multíparas e novilhas Nelore de dois anos foram suplementadas ou não com milho moído durante o protocolo de IATF até o diagnóstico de gestação com o intuito de avaliar a alteração nos hormônios metabólicos e seus impactos na reprodução. No Capítulo 4, multíparas Nelore de duas fazendas foram suplementadas ou não com virginiamicina adicionada ao sal mineral. Em todos os experimentos as fêmeas foram submetidas a protocolos de IATF e colocadas com touro até o fim da estação de monta, sendo que apenas nos experimentos do Capítulo 3, as fêmeas receberam segunda IATF caso estivessem vazias antes da entrada dos touros. No experimento 1 do Capítulo 2 e no experimento 1 do Capítulo 3 houve efeito linear positivo da concentração de IGF-1 no dia da inseminação na probabilidade de prenhez a IATF. Em todos os experimentos realizados, também houve efeito linear positivo da concentração de IGF-1 no dia da inseminação na probabilidade de prenhez ao final da estação de monta, exceto no experimento 2 do capítulo 2. A concentração de IGF-1 no diagnóstico de gestação apresentou efeito linear negativo na probabilidade de prenhez em quatro estudos. O efeito do GH e da leptina nos parâmetros reprodutivos não foi consistente entre os estudos. A suplementação com milho não alterou a taxa de prenhez à IATF, mas houve tendência no aumento da prenhez na segunda inseminação e aumentou a taxa de prenhez ao final da estação de monta de primíparas, diminuiu a taxa de prenhez ao final da estação de monta em multíparas e aumentou somente o peso a desmama dos bezerros de primíparas. A suplementação com virginiamicina não aumentou a taxa de prenhez a IATF e ao final da estação de monta na Fazenda A, enquanto que na fazenda B não aumentou a taxa de prenhez a IATF, mas aumentou a porcentagem de fêmeas ciclando no diagnóstico de gestação e uma tendência no aumento da probabilidade de prenhez ao final da estação de monta. O peso a desmama aumentou em ambas fazendas com suplementação de virginamicina. Conclui-se que o IGF-1 no momento da IA e no momento do DG são possíveis importantes marcadores de fertilidade em bovinos e que estratégias nutricionais podem alterar esses hormônios com ou sem impacto na reprodução. / The metabolic hormones IGF-1, GH and leptin change according to nutritional managmentof the herd. The aim of these trials was to measure the concentration of these metabolic hormones in 12-16 months old Nellore heifers and multiparous cows and associate with the reproduction performance in experiments of Chapter 2. In Chapter 3, 2-years old heifers, primiparous and multiparous Nellore cows received or not ground corn starting in the begginning of TAI protocol until pregnancy check on day 30 to associate with metabolic hormones and reproduction. In Chapter 4, multiparous Nellore cows of two farms were supplemented or not with virginiamycin in mineral salt and the association with metabolic hormores and reproduction was evaluated. In all studies TAI was performed and bulls stayed from 7 days after TAI until the end of breeding season, except on trials of Chapter 3, which second TAI was performed in open cows before being exposed to bulls. In experiment 1 of Chapter 2 and experiment 1 of chapter 3 there was a linear positive effect of IGF-1 concentration on day of insemination on TAI pregnancy rate. In all trials, IGF-1 concentrations on insemination had a linear positive effect on pregnancy rate in the end of breeding season, except in experiment 2 of chapter 2. The IGF-1 concentrations on pregnancy rate had a linear negative association with TAI pregnancy rate in 4 studies. Concentraions of GH and leptin had no consistent association with reproduction rates. Corn supplementation did not alter TAI pregnancy rate, but tended to improve pregnancy rate on second AI and increased final pregnancy rate in primiparous cows, reduced final pregnancy rate in multiparous cows and increased weaning rate of primiparous calves supplemented with corn. Virginiamycin supplementation did not increase TAI and final pregnancy rates in farm A, while farm, B did not increase TAI pregnancy rate, but increased the percentage of cycling cows on pregnancy check and tended to increase final pregnancy rate in the end of the breeding season. In both farms, calves weaning weight increased with virginiamycin supplementation. In conclusion, IGF-1 concentrations on TAI and pregnancy check can be possible markers for fertility in Bos indicus cows and nutritional strategies can change metabolic hormones affecting or no reproduction parameters. / FAPESP: 2014/03209-0

East Tennessee has one of the most rapidly growing Hispanic population in the country. Further, it has been previously reported that this population is at an increased risk for developing metabolic syndrome (MetS), which is characterized by central obesity, abnormal blood lipids, hypertension, insulin resistance, and glucose intolerance. Our collaborators at the Johnson City Community Health Center (JCCHC) observed these indicators of MetS even in young children, between the ages of two and ten. The principle objective of this research project was to examine the prevalence of risk factors for MetS and establish an expanded metabolic profile of young Hispanic children. These factors have not been previously examined in this population. Our working hypothesis is that even at a young age markers of MetS, specifically dysregulated hormone levels, are present in this pediatric population. Methods: In this cross-sectional analysis, a total of 118 Hispanic children between 2-10 years of age (Mean 6.4 ± 2.7, 45% male) age adjusted anthropometric measurements and blood samples were obtained. Blood samples were analyzed for glucose, and lipids (triglycerides, LDL (low density lipoprotein) and HDL (high density lipoprotein) cholesterol) and C-reactive protein through ETSU clinical labs. Insulin, adiponectin, leptin, ghrelin, CRP, IL-6, and TNF-a levels were measured using commercially available assays (Bio-Rad® Multiplex Immunoassay System). Results: There was a significant positive correlation with leptin and adiponectin levels and BMI. Further, children with 2 or more risk factors for metabolic syndrome (as determined by age- and sex-specific: waist circumference, blood pressure, HDL, and triglyceride measures) had significantly elevated leptin levels. The proportional relationship between these metabolic hormone levels and the central obesity indicator confirms that metabolic abnormalities are present in the pediatric Hispanic population at a young age in Northeast Tennessee. The predisposition for this demographic developing metabolic syndrome is evident with indicators being present so early in life. With Tennessee being ranked third in the nation for Hispanic population growth rate, these findings indicate a need for early age intervention protocols for Hispanic children in order to reduce their risk of developing metabolic syndrome.