Understanding the nature of ruminant nutrition and digestion is essential to improve feeding management and animal production. Among many approaches, manipulating ruminant nutrition and fermentation through feed supplementation is being practised and researched. Over the last decade, the utilization of vegetable oils in feed formulation and their effects on various aspects of ruminants have been reported by many researchers. It is important to understand the lipid metabolism in ruminants by microorganisms because it affects the quality of ruminant-derived products such as meat and milk. Majority of vegetable oil supplementation could reduce rumen protozoa population in ruminants due to the effects of medium-chain fatty acids (FAs). However, vegetable oil also contains unsaturated FAs that are known to have a negative effect on cellulolytic bacteria which could show inhibitory effects of the fibre digestion. In this paper, the physiology of nutrient digestion of ruminants is described. This paper also provides a current review of studies done on improvement and modification of rumen fermentation and microbial population through vegetable oil supplementation.

No abstract

Oil palm frond (OPF) is a biomass residue from oil palm plantations that has received increasing interest for its promise as roughage resources to overcome limitations of ruminant feeding. However, the use of OPF as a feedstuff for optimal livestock productivity is limited by its high lignocellulosic content and low nutritional value. Chemical composition revealed that OPF was composed of 70% fibre and 22% soluble carbohydrates on a dry matter (DM) basis. Various physical, chemical, biological and physico-chemical treatments have been used to improve the digestibility of nutrients and the nutritional value of OPF. This review was conducted to study the treatment methods of OPF as a value-added feedstuff, and, to emphasize on the effects of treated OPF on in vitro ruminal fermentation and in vivo ruminant digestibility coefficients and growth performance. The biological treatment produced favourable outcomes in improving the nutritional value of OPF, and was more cost-effective, safe and environmentally friendly as compared to chemical and physical treatments. In vitro rumen fermentation studies on the digestibility and potential use of treated OPF as quality feedstuffs for ruminants have been widely reported. Several in vivo studies have found that small ruminants performed satisfactorily when fed diets with treated or pre-digested OPF at appropriate ratios. Nevertheless, chemically treated OPF has been found to be successfully used in both beef and dairy cattle feeding trials as it is a good source of protein and energy that can increase digestibility coefficients and have positive impacts on ruminal fermentation profiles and animal production.

Ammoniation of oil palm frond (OPF) with non‐protein nitrogen (N) sources has been shown to improve the nutritional value and digestibility of OPF in ruminants. This study evaluated the effect of treating OPF without (control) or with different urea levels (1%–5%) on chemical composition and in vitro gas production, digestibility and fermentation properties using goat rumen fluids. The results showed that the treated OPF with urea (1%–5%) had significantly lower (p < 0.05) dry matter (DM), organic matter (OM) and ash contents than that of the control. The crude protein (CP) content of treated OPF increased (linear p < 0.05; quadratic p < 0.05) with increasing levels of urea inclusion (1%–5%), whereas the contents of neutral detergent fibre (NDF) and acid detergent lignin (ADL) were significantly (p < 0.05) decreased. The CH4 (ml/500 mg DM incubated) production decreased (linear p < 0.05) with increasing levels of urea inclusion in treated OPF silage. However, in vitro DM and OM degradability were significantly (p < 0.05) increased by higher inclusion levels of urea (4% and 5%). OPF treated with 4% or 5% urea also revealed significantly (p < 0.05) higher total volatile fatty acids and ammonia‐N than the control and OPFs treated with 1%–3% urea. Ammoniation of OPF with urea improved its nutritional value and in vitro rumen fermentation profiles in goats. The impact was more pronounced for 4% or 5% urea‐treated OPF.

The study was conducted to develop a nutrient-balanced goat feed pellet from oil palm by-products and to assess the effects of the feed pellet on growth performance and carcass traits of Katjang goats. Treatment groups consisted of oil palm by-products based (OPB), control without addition of oil palm by-products control (CNT), and commercial (COM) pellets. Twelve 12-months-old Katjang goats were assigned to the three treatment groups and subjected to 14-weeks of feeding trial. Each group was offered 1.5% body weight (BW) of respective pellets and ad libitum supply of Napier grass. Feed intake (FI) was recorded daily and the BW of the goats was recorded weekly. At the end of the feeding trial, all goats were slaughtered for carcass traits study. All treatment groups showed no significant difference in BW increment (p=0.51) and average daily gain (ADG) (p=0.94). There were no significant differences (p>0.05) between the treatment groups for carcass traits parameters. As a conclusion, the OPB pellet has shown to contain complete nutrient for goat's diet and was comparable to the COM feed pellet in terms of growth performance of Katjang goat. The inclusion of oil palm by-products in the feed formulation did not adversely affect the carcass traits of the goats.