Ruminal availability of starch content and degradability of crude protein in diets based on silage cane sugar to dairy cows

Abstract

The proper functioning of the rumen and consequently, high milk production are dependent on the supply of diet metabolizable energy and protein. One of the main points sought in the nutrition of dairy cows is the understanding of the factors that influence the efficiency of protein fractions utilization in relation to the supply of energy sources to meet the cows' requirements. This study will be carried out by three main experiments, which aim to evaluate the effect of replacing dry grounded corn (DGC) by grounded, rehydrated and ensilaged corn (GREC) in diets with sugarcane as roughage. By the inclusion of GREC, this study will evaluate the effect of increasing levels of dietary CP content (12, 14, 16 and 18%) and degradability of dietary CP (60:40, 70:30, 80:20 and 90:10, RDP:RUP ratio) on intake, milk yield and composition, ruminal parameters and metabolic profile of dairy cows. GREC will be achieved by grounding dry corn and subsequent recovery of 30% moisture by addition of inoculant with water and latter ensiling. Twelve Holstein cows, multiparous, in the middle phase of lactation and producing 22.0 kg milk/d will be grouped into three balanced and contemporary 4x4 Latin squares during the experimental period of 21 days, 14 days for diet adaptation and remainder to samples collection. Blood samples will be collected at 16th day of each experimental period for measurement of blood parameters. Milk samples for analysis of composition, somatic cell count, total nitrogen, allantoin and urea will be collected in the morning and afternoon milking during the last seven days of each experimental period. Spot urine samples will be collected on the 16th day of each period to estimate the microbial synthesis. Analyses of pH, short chain fatty acids and ammonia nitrogen will be performed from rumen fluid samples collected through esophagic sounding at 19th day of each experimental period. Digestibility will be determined by internal indicator iADF after collection of feces samples from 15st to 18th day of each experimental period. Overall, we expect by the results of this study to contribute scientifically to better understanding of the starch source effectiveness regarding the source, content and degradability of protein in diets with sugarcane silage as forage. (AU)