Effect of oil palm meal on nutrient utilization and milk production in lactating dairy cows fed with urea-treated rice straw

Abstract

Five Holstein-Friesian crossbred dairy cows were randomly assigned according to a 5 × 5 Latin square design to study the effects of different inclusion levels of oil palm meal (OPM) at 0%, 10%, 20%, 30% and 40% in the concentrate on feed intake, nutrient digestibility, rumen fermentation and milk production in lactating dairy cows. Cows received urea-treated rice straw ad libitum as a roughage source. The results showed that the concentrate intake and total dry matter intake were significantly (p < 0.05) highest in cows fed with 10–20% oil palm meal (OPM) in concentrate, while roughage intake was not significantly (p > 0.05) different among treatments. Similarly, dry matter, organic matter, and natural detergent fiber were significantly (p < 0.05) higher in cows fed with 10% OPM in the concentrate than those in other treatments, resulting in the highest nutrient intake (p < 0.05). Feed intake, nutrient digestibility and nutrient intake significantly (p < 0.05) decreased with increasing levels of OPM up to 30–40% in the concentrate. Blood-urea nitrogen, ruminal temperature, ruminal pH, NH3N, total volatile fatty acids, acetic acid and butyric acid were similar among treatments (p > 0.05), whereas, propionic acid decreased with increasing levels of OPM in the concentrate, which was lowest in cows fed 40% OPM, resulting in the significantly (p < 0.05) highest acetic acid to propionic acid ratio and methane production. Furthermore, milk yield was significantly (p < 0.05) the highest in cows fed concentrate with 10–20% OPM, while feeding cows OPM did not affect milk composition (p > 0.05). In conclusion, the optimum level of OPM in the concentrate for lactating dairy cows fed with urea-treated rice straw as a roughage source in this study should not exceed 20%.