Ruminant Nutrition: Carbohydrates and Lipids

摘要

The term “precision-feeding” refers to a program that provides heiferswith the correct amount of nutrients necessary for adequate growth withoutaffecting future performance. Including poultry fat (PF) can accuratelymeet caloric requirements and reduce dry matter intake (DMI) when dietsare isocaloric and isonitrogenous. However, high fat intake may lead toreduction in fiber digestibility and inadequate rumen fermentation. Yet,reduction of DMI as PF is incorporated into diets can provide similar energyto the animal limiting the negative effects associated with fat inclusion.The objective of this study was to evaluate the effects on nutrient digestionof including different levels of PF inclusion in precision feeding dairyheifers. We hypothesized that including PF would further reduce intakewithout compromising nutrient digestibility in dairy heifers. Treatmentsincluded 55% forage diet with 4 levels of PF inclusion starting with a basalconcentration of fat in the diet [3% fat (0% PF); 5% fat (2% PF); 7% fat(4% PF); and 9% fat (6% PF)]. Holstein and Jersey heifers were randomlyassigned to treatments and administered according to a split-plot, 4 × 4Latin square design (21-d periods). Data were analyzed using the MIXEDprocedure of SAS. There were no differences on OM apparent digestibilitycoefficients (dC) between the Holstein and Jersey-group. However, NDFdC was higher (P < 0.01) in Holstein heifers (68.40 vs. 61.34 ± 1.2%),but the Jersey-group had higher ADF (34.15 vs. 44.58 ± 1.6%), and N dC(90.01 vs. 92.04 ± 0.3%). The inclusion of PF did not affect OM, NDF, andADF dC. However, the EE and N dC increased linearly with the increasedlevel of PF inclusion. The Holstein-group spent more time to finish theirmeal (P < 0.05) than the Jersey-group (65.33 vs. 59.94 ± 1.6 min), and thePF inclusion showed a linear decrease in the time spent to finish the meal.These results suggest that Holstein utilized NDF more efficiently. In thecurrent study, increasing dietary PF inclusion up to 9% DM reduced DMIwithout affecting OM and fiber digestibility but increased EE and N dC.