Plan of nutrition in dairy goats diets on mammary gland development

Abstract

Rearing replacement dairy animals is one of the most costly phases on a dairy farm, foe being it an unproductive period. For that reason, high plane of nutrition is given to provide high gains and decrease age at sexual maturity. However, this high energy and protein consumption, during the prepubertal period, may affect body growth and mammary secretory tissue development. The aim of this experiment was to evaluate the effect of different average daily gains (ADG) and dry matter (DMI), crude protein (CPI) and metabolizable energy intake (MEI) on body and mammary development. Forty Saanen kids, 109.1±21.4 days old and 12.9±2.9 kg initial body weight, had their body and gland morphometry, and mammary parenchyma (PAR) measured until 30 days of pregnancy. They were separated in four diets with ten animals each, where each group received a different protein-rate diet 15, 17, 18 and 19% , allowing different ADG (90, 130, 170 and 210 g/day) and nutrient consumption. Mammary morphometry was obtained weekly, whereas body morphometry and mammary PAR at every fourteen days. For PAR access, a B-mode ultrasound with a 5.0 MHz convex probe was used to examine in a 2-dimension PAR area, perimeter and grey scale, of bothglands, throughout the trial. Data was analyzed with a multiple regression using RStudio software. Throughout the trial, all variables augmented. ADG had the major impact, influencing positively all body measurements (p<0.01) and mammary teat growth (p<0.01), PAR area (p<0.01), PAR perimeter (p<0.001). MEI influenced only rump length and chestwidth (p<0.05) on body growth, right PAR area and perimeter (p<0.05). CPI and DMI did not influence body growth; however, protein affected considerably PAR development, increasing area, perimeter, and maximum grey value. Allometry coefficients of PAR area were low whencompared to other body coefficients. However, it was possible to visualize a change of proportion in fifteen times for this variable, which means that PAR area increased more proportionally with time. Increasing levels of CPI, conversely from MEI, had an important and positive impact on body and mammary growth. Mammary growth could not be associatedwith any body growth pattern.