Sources and levels of rumen protected fat on energy balance of dairy cows grazing a tropical pasture

Abstract Text: The objective of this experiment was to investigate the effects of supplementation lactating cows grazing a tropical pasture receiving two levels of calcium salts of palm oil (CSPO) or calcium salts of soybean oil (CSSO) on energy balance. Five rumen-cannulated cows (115 ± 8.1 DIM) were used in a Latin square 5x5 and subjected to the following treatments: a) control (no fat); b) 400 g CSSO cow^-1 d^-1; c) 700 g CSSO cow^-1 d^-1; d) 400 g CSPO cow^-1 d^-1; and e) 700 g CSPO cow^-1 d^-1. Treatment periods were 24 d in length and cows grazed paddocks of Pennisetum purpureum and received 8 kg cow^-1 d^-1 (DM) of concentrate. Concentrate of treatment control was composed by ground corn (82.8%), soybean mean (12%), urea (0.2%), sodium bicarbonate (1%) and mineral/vitamin premix (4%) and fat supplementation replaced ground corn. To estimate fecal excretion, cows were orally dosed with titanium dioxide twice daily for 15 d. Forage intake was calculated from total fecal excretion and feed digestibility. Indigestible NDF (estimated as NDF residue after 240 h of in situ incubation) was used as an internal marker to estimate digestibility. NE_L intake, milk NE_L and NE_L in empty BW gain was calculated according to NRC (2001). Data were analyzed using a mixed model with animal and period as random effects. The means were compared using a Tukey test. Both levels of CSPO increased NE_L intake (27.7 Mcal/d). There was no difference in NE_L intake between control and 400 g CSSO (26.1 vs. 26.0 Mcal/d), but both were greater than 700 g CSSO (25.4 Mcal/d). The milk NE_L (Mcal/d) was greater for 400 g CSPO (13.1) and 700 g CSPO (12.9) in comparison to control (12.1) and 400 g CSSO (11.6). The lowest milk NE_L was observed in 700 g CSSO (10.3), due to the lowest milk yield and milk NE_L per kg of milk observed in this treatment. The NE_L in empty BW gain (Mcal/d) was greater in 700 g CSSO (3.03) compared with 400 g CSSO (2.65), and both levels of CSPO (2.05 and 2.28 for 400 and 700 g, respectively). The control showed the lowest NE_L in empty BW gain (1.63) among the treatments. Dairy cows grazing tropical pasture supplemented with sources of fat increased energy intake with CSPO and the energy consumed was used differently according to the source of fat supplemented.   

Keywords: palm oil, soybean oil