ADSA Graduate Student Production PhD Poster Competition

摘要

Fat inclusion can increase energy density of diets fed to ruminants, thereforereducing dry matter intake (DMI) required to meet caloric demands,however detrimental effects to rumen fermentation have been reported.There is evidence that not all fat sources have this negative response.Diets used for precision-feeding are more nutrient dense, allowing anincrease in energy and nutrient utilization efficiency while decreasingnutrient loss. We hypothesized that including poultry fat (PF) would reduceintake without compromising rumen fermentation in dairy heifers.Four Holstein and 4 Jersey cannulated heifers were randomly assignedto 4 treatments, included 55% forage diet with 4 increasing PF inclusionstarting with a basal concentration of fat in the diet [3% fat (0%PF); 5% fat (2% PF); 7% fat (4% PF); and 9% fat (6% PF)]. Treatmentsadministered according to a split-plot, 4 × 4 Latin square design for 4periods of 21 d [(16 d adaptation, (5 d sampling; rumen sampling werecollected on the last day of each period)]. Data were analyzed using theMIXED procedure of SAS with fixed effects of period, breed, PF inclusion,breed × PF interaction, and a random effect of heifer (breed) andrepeated measures when needed. There were no differences on rumenVFA between the Holstein and Jersey-group. Total VFA concentrationand acetate molar proportion decreased linearly with the increased levelof PF inclusion. Concurrently, there was a linear increase in propionatemolar proportion resulting in a linear reduction on the A:P ratio with PFincremental inclusion. Iso-butyrate molar proportion increased linearly asPF increased. Mean rumen pH was not affected by breed, but the PF inclusionshowed a linear increase on rumen pH (P < 0.03). Rumen NH3-Nconcentration was not affected by breed, but PF inclusion resulted in anincreasing linear trend on rumen NH3-N (P = 0.10). These results suggestthat Holstein and Jersey heifers had a similar pattern and rate of rumenfermentation and that increasing PF inclusion in precision feeding programis affecting rumen fermentation pattern mainly by reducing the A:P.