Dietary application of dried citrus pulp, with or without soybean oil, in lactating Holstein cow diet: Effects on feed intake, digestibility, performance, a milk fatty acid profile and total phenolics

The effect of dietary dried citrus pulp (DCP), with or without soybean oil (SO), on nutrient intake and digestibility, performance, milk fatty acids (FAs) profiles, and total phenolic (TP) was studied in lactating cows. Ten lactating Holstein cows (145 ± 25 DIM and average body weight (BW) of 650 ± 40 kg) were allocated to a changeover 5 × 5 Latin square design with 28-d periods. Treatments included the control diet, diet without SO and DCP; SO0 + DCP1, diet without SO and containing 86.5 g DCP/kg DM; SO0 + DCP2, diet without SO and containing 173 g DCP/kg DM; SO1 + DCP1, diet containing 17.3 g SO and 86.5 g DCP per kg DM; SO1 + DCP2, diet containing 17.3 g SO and 173 g DCP per kg DM. The maximum EE digestibility was observed for SO1 + DCP1 diet (P = 0.030). The addition of DCP and SO to experimental diets could not affect the milk production. The milk TP (mg/mL, P = 0.003 and mg/d, P = 0.030) production was increased as a result of the addition of SO and DCP. The milk produced by cows fed with the control diet contained lower C4:0 compared to that of cows fed with other diets (P = 0.014). Concentrations of C8:0 (P = 0.028), C10:0 (P = 0.003) and C12:0 (P = 0.0001) within the milk of cows with SO0 + DCP1 diet were lower than those with SO0 + DCP2 diet. The interaction effect of SO and DCP on C16:1 was significant (P = 0.022). The concentration of C18:0 in the milk of cows fed with SO (P = 0.008) or DCP (P = 0.002) was lower than those with the control diet. The low and high levels of SO-contained DCP, as well as high level of DCP without SO respectively increased the concentration of C18:1 trans (P = 0.002), total monounsaturated fatty acids (TMUFA) (P = 0.046) and decreased the content of total saturated fatty acids (TSFA) (P = 0.022). The milk produced by cows supplemented with SO had higher levels of C18:1 (P = 0.039) and C18:2 cis (n-6) (P = 0.0005) compared to those with the control diet. Current findings suggested that SO plus DCP could be added to the diets of dairy cow without any detrimental effects on the performance. Also, it could be useful due to the existence of TP and unsaturated fatty acids (UFA).