Ciência Animal Brasileira (Dec 2010)
AN ALTERNATIVE METHODOLOGY OF DETERMINING FEED SORTING IN TRANSITION DAIRY COWS FED GLYCEROL
Abstract
The objective of this study was to compare the standard methodologywith an alternative method to determine feed sorting in dairy cows during the transition period. Twenty-six Holstein multiparous cows were paired by expected calving date and fed diets containing either glycerol or high moisture corn from -28 through +56 days relative to calving (DRTC). Feed sorting was determined on -16, -9, +9, +15 and +51 DRTC in two different ways. Firstly, it was determinedas the actual intake of each screen of the Penn State Particle Separator (PSPS) consumed between 0-4, 4-8, 8-12 and 12-24 hours post feeding, and expressed as a percentage of the predicted intake of that correspondent screen. Secondly, by measuring the particle size distribution of feed consumed between 0-4, 4-8, 8-12 and 12-24 hours post feeding. The total mixed ration (TMR) at feeding and at each time post feeding was separated by size using the 3-screen (19, 8, and 1.18 mm) Penn State Particle Separator (PSPS) to yield long (>19 mm), medium (8 mm), short (1.18 mm), and fine particles (19 mm) and reduced (P1.18 mm) and fine particles (0.05) the proportion of DM% retained as medium particles (8 mm). Cows fed prepartum glycerol increased (P19 mm) according to the standard methodology (77.2 vs. 101.5%, control vs. glycerol) and also in the alternative methodology (9.2 vs. 17.8%, control vs. glycerol). Cows fed prepartum glycerol discriminated against (P1.18 mm) in the standard methodology (102.6 vs. 94.2%, control vs. glycerol) as well as in the alternative methodology (42 vs. 37.3%, control vs. glycerol). There was no response (P>0.05) of diet on feed sorting of fine particles (8 mm) according to the standard methodology (108.6 vs. 116.5%, control vs. glycerol), but did not (P>0.05) according to the alternative methodology. Cows fed postpartum glycerol discriminated against (P1.18 mm) according to the standard methodology (100.6 vs. 96.6%, control vs. glycerol), but did not (P>0.05) according to the alternative methodology. Feeding prepartum glycerol to transition dairy cows increases the preference for the long-stem forage particles of the diet. The alternative methodology proposed in this study is more reliable than the standard methodology to determine feed sorting.
