Effect of nutrition and the EPD from bulls for sexual precocity on puberty in Nellore heifers

• Grant number: 13/09921-1
• Support Opportunities: Scholarships in Brazil - Doctorate
• Effective date (Start): August 01, 2013
• Effective date (End): July 31, 2016
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Production
• Principal Investigator: Alexandre Vaz Pires
• Grantee: Marcos Vinicius de Castro Ferraz Junior
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Nellore is the main breed created in Brazilians beef cattle production systems. The late onset of puberty in Nellore heifers is one of the problems for this breed. Thus, studies of the effect of nutrition on the expression of puberty are needed. However, a major problem of this type of study is the genetic heterogeneity of this breed. The objective is to evaluate the interaction between nutrition and expected progeny differences (EPD) for sexual precocity heifers. Will be used 56 weaned heifers with 7 months old, resulting from IVF (in vitro fertilization), daughters of bulls 4 (2 with positive EPD and 2 with negative EPD to sexual precocity). These heifers will be divided into two groups, one with high gain (ADG) (700 kg / animal / day n = 28 heifers) and one with low ADG (300 g / animal / day n = 28 heifers). Forming a 2x2 factorial scheme, in which the first factor is the EPD from bull and the factor 2 is ADG, thus four treatments High EPD and High ADG (HEHA), High EPD and Low ADG (HELA), Low EPD and High ADG (LEHA), Low EPD and Low ADG (LELA). The heifers will be housed in pens (2 per pen) to control dry matter intake (kg and % BW), ADG and feed efficiency (FE) calculated as ADG / CMS. The ADG and puberty will be evaluated by weekly weighing, ultrasound (US) and blood samples for measurement of progesterone (P4). It will also be collected weekly blood samples for measurement of IGF-1, IGF-1 as well as P4 will be evaluated by chemiluminescence (IMMULITE ® 1000 - Siemens Healthcare Diagnostics). The heifers will be considered as puberty when has a corpus luteum in the US and P4 concentration greater than 1 ng/mL. Once a month, the heifers over 230 kg of body weight will be US scaned daily for 10 days in order to characterize the follicular wave development. Whose variables are the diameter of the dominant follicle, the duration of the follicular wave development, the number of follicles per follicular wave development and uterine horn diameter. At 7 and 14 months old heifers underwent biopsy of adipose tissue to assess gene expression for leptin. Will be used a randomized block design (which will be considered the mothers of heifers as a block) in a 2x2 factorial design. Continuous variables will be analyzed by the MIXED procedure and the variables with binomial distribution will be analyzed by the GLIMMIX procedure (SAS 9.3). (AU)

Academic Publications

(References retrieved automatically from State of São Paulo Research Institutions)

FERRAZ JUNIOR, Marcos Vinicius de Castro. Puberty of heifers: 1 - Effect of nutrition and EPD of sire for sexual precocity on puberty in Nellore heifers; 2 - Effect of early weaning and nutrition in metabolic imprinting on puberty in Nellore and crossbreed (Angus x Nellore) heifers. 2016. Doctoral Thesis - Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) Pirassununga.