The partial replacement of corn silage by sugarcane silage plus crude glycerin and the effect of sensory feed additives for dairy cows
Crude glycerin may compensate for the energy loss during the ensiling of sugarcane. The partial replacement of corn silage (CS) with an iso-NDF amount of sugarcane silage plus crude glycerin (SG), added or not of sensory feed additives (SA), was evaluated. Thirty-two Holsteins (182 DIM) were individually fed a standardization diet for 2 weeks and a treatment for 44 days. The main statistical model contained covariate, block, forage, additive, interaction, time, and its two and three term interactions. Treatments were (% of DM): CS (30.2%) or CS (15%), sugarcane silage (10%), and crude glycerin (3.3%); with or without SA (Luctarom SFS-R 3386-Z and 1353-Z. Lucta, Spain) added to corn and then to forages in the mixer. Diets also contained 9.2% sorghum silage, 4.4% Tifton hay, and 24.5±0.5 forage NDF. SA reduced milk yield in CS (32.2 vs. 31.1 kg/d) and increased in SG (30.3 vs. 31.7 kg/d) (P<0.01 interaction); yields of lactose and solids followed the same trend (P<0.05). SG increased DMI (22.6 vs. 21.9 kg/d, P<0.01), while there was a trend for decreased DMI in response to SA (22.5 vs. 22.0 kg/d, P=0.07). The ratio of milk to DMI had a greater positive response to SA in SG (1.34 vs. 1.43) than in CS (1.44 vs. 1.46) (P=0.03 interaction). SG increased the contents of fat (P=0.01) and protein (P=0.08), improving milk solids (P=0.03). There was no effect on feed sorting from 7AM to 1PM (P>0.38). From 2PM to 7PM, SG induced selection in favor of particles >19mm (P=0.05), and, when added to CS, SA induced the rejection of 8-19mm particles and consumption of <8mm particles, but had no effect when added to SG (P<0.01 interaction). The intake rate from 7AM to 1PM was faster in SG (P<0.01), and it tended to be slower when SA was added to CS (P=0.05 interaction). Plasma glucose content was reduced by SA in CS and increased in SG (P=0.01 interaction). PUN did not respond to treatments (P>0.39). There was a trend for reduced plasma gamma-glutamyl transferase on SG (P=0.09). Chewing activity was similar across treatments (P>0.49), as well as the daily excretion of urinary allantoin (P>0.11), ruminal fluid pH (P>0.24), and protozoa count (P>0.48). Total tract apparent digestibility was not determined by treatments (P>0.39) neither the intake of digestible OM (P>0.72). The partial replacement of CS by SG plus SA was a plausible alternative for feeding dairy cows.
Glycerin, sugarcane silage, sorting