Epsilon Archive for Student Projects

Abstract

Rumen passage rate depends upon the feed's particle size, specific gravity, and chemical composition. Since rumen epithelium is the leading site of Mg absorption, changes in the rumen passage rate may influence magnesium (Mg) absorption. The study investigated the impact of changes in the forage physical form and maturity on Mg absorption by altering the feed's physical form and NDF contents and monitoring how these two factors could be manipulated to reduce the risk of Mg deficiency in cattle. Eight (8) Swedish Red cattle, four fistulated and four non-fistulated, were enrolled in the study and given the experimental diets for the study period of 21 days. The rumen passage rate was measured using the fibre fraction of the roughages mordanted with 2 grams of Cr through serial faecal sampling for 132 hours after feeding the Cr-marker. The other parameters recorded were daily Mg intake, Mg digestibility, Mg proportion in urine and faeces, dry matter digestibility, Mg excreted in urine, faeces and milk and total mean retention time (TMRT). The statistical analysis using SAS statistical software with the stage of cut (early vs late) and nature of processing (chopped vs extruded) as independent variables showed that the stage of cut influenced the dry matter digestibility, Mg intake and digestibility. Processing, i.e., extrusion, decreased the particle size and lowered the dry matter digestibility compared to the control group. Most dietary Mg is excreted through the faeces, and a smaller proportion is excreted in the urine. The processing method did not influence the proportion of Mg in urine and faeces. Stage of cut had a statistically significant relationship with the Mg proportion in faeces. The smaller fraction of Mg excreted in the milk was independent of the stage of cut and the nature of the processing. The total mean retention time (TMRT), the primary measure of rumen passage rate, depends upon the density and size of the particles but was not affected by the independent variables used in the study. The stage of cut was thus a more important regulator of Mg metabolism than the processing.