Different forage sources for F1 Holstein x Gir dairy cows

We evaluated the effect of four different forage sources on the performance of crossbred dairy cows under tropical conditions. The experiment was carried out on the Experimental Farm of the Agricultural Research Company of Minas Gerais, in Felixlandia-MG, Brazil. Twelve crossbred F1 Holstein x Gir cows were allocated to a triplicated 4 x 4 Latin square, balanced for residual effect, with each diet assigned to one group of three cows each period. The experiment had four treatments and five experimental periods of 21 days, with 14 days for adaptation and 7 days for data collection. The treatments included sorghum silage, corn silage, fresh sugarcane and sugarcane silage treated with 1% calcium oxide. Three markers LIPE (R), titanium dioxide and iADF were used to estimate the individual intake and the apparent digestibility of the feed for the cows in each group. The data were subjected to analysis of variance and compared by a Tukey's test at 5% probability using the PROC GLM of SAS, version 8.0 for Windows software. The dry matter intake (DMI) and organic matter intake (OMI) were highest (P<0.05) for cows consuming corn silage (P<0.05) than for cows consuming sorghum silage, fresh sugarcane and sugarcane silage. The DMI for fresh sugarcane was lower than for corn silage and sorghum silage (P<0.05). DMI was least when cows were fed sugarcane silage (P<0.05). The dry matter digestibility (DMd) and organic matter digestibility (OMd) of corn silage, sorghum silage and fresh sugarcane were similar (P>0.05) but all were higher than for the sugarcane silage-based diet (P<0.05). Milk yield by cows fed corn silage and sorghum silage was similar (P>0.05) but both were higher than for cows fed sugarcane silage and fresh sugarcane. Non-esterified fatty acids in the plasma were the greatest (P<0.05) for cows fed sugarcane silage. Nitrogen balance was the greatest for cows fed corn and sorghum silage, followed by fresh sugarcane and then sugarcane silage (P<0.05). The sugarcane silage-based diet resulted in low intake, low digestibility, low efficiency of nitrogen utilization, and high mobilization of body reserves by F1 Holstein x Gir cows, but supported a milk production similar to cows fed fresh sugarcane. Corn silage and sorghum silage resulted in satisfactory cow performance and nitrogen utilization, even when the forage:concentrate ratio was high. (C) 2011 Elsevier B.V. All rights reserved.