The Effects of Oil Palm Fronds Silage Supplemented with Urea-Calcium Hydroxide on Rumen Fermentation and Nutrient Digestibility of Thai Native-Anglo Nubian Goats

This study aimed to examine the combined effects of urea and calcium hydroxide ensiled oil palm fronds on rumen fermentation and digestibility of Thai native-Anglo Nubian goats. A 4 × 4 Latin square design was used to randomly assign four male crossbred goats (Thai native × Anglo Nubian). The dietary treatments were as follows: ensiled oil palm frond with no additives (EOPF as the control), urea 5% (50 g/kg fresh matter) (E-UOPF 5%), calcium hydroxide (Ca(OH)2) 5% (50 g/kg fresh matter) (E-CaOPF 5%), and combination of urea 2.5% (25 g/kg fresh matter) with Ca(OH)2 (25 g/kg fresh matter) (E-UCOPF 2.5%). The oil palm frond ensiled with different additives did not change the DM intake (p > 0.05). The total TMR intakes range from 69.39 to 77.09 g/kg BW0.75. The goats fed with E-UOPF 5.0% consumed significantly more CP than the other groups (p < 0.05). The E-UCOPF increased ME intake by 4.8%, compared with the control treatment (p < 0.05). E-UOPF 5% and E-UCOPF 2.5% significantly increased the CP digestibility by 19.7% and 17.1%, respectively (p < 0.05). Furthermore, E-CaOPF 5.0% and E-UCOPF 2.5% improved the NDF digestibility by about 10.9% and 9.90%, respectively (p < 0.05). The urea-containing oil palm frond (E-UOPF 5.0% and E-UCOPF 2.5%) had higher blood urea nitrogen (BUN) than the other groups (p < 0.05). The TVFA of goats fed E-UCOPF 2.5% was approximately 15.8% higher than that of goats provide EOPF (p < 0.05). The mean concentration of C3 increased by 7.90% and 11.61%, respectively, when E-CaOPF 5.0% and E-UCOPF 2.5% were provided instead of EOPF (p < 0.05). The total N intake and absorbed were highest (p < 0.05) when goats offered E-UOPF 5.0% (p < 0.05). The goats fed oil palm frond without additives had the lowest percentage of N-absorption/N intake (p < 0.05). This study clearly shows that the most suitable treatment is E-UCOPF 2.5%, which enhances DMD, nutrient digestibility, TVFAs, and nitrogen balance and has no negative effects on rumen microbes. This indicates that E-UCOPF 2.5% may be utilized as an alternate roughage source in TMR diets, accounting for at least 40% of the OPF. However, several factors still require consideration for urea-Ca(OH)2 treatments to be successful, including other concentrations of urea, moisture content, duration of pre-treatment, and the metabolizable protein system.