Effects of supplementing oil palm (Elaeis guineensis Jacq.) leaf methanolic extracts on rumen fermentation and meat quality of boer goats

Red meat and its meat products have been associated with significant risks of chronic metabolic disorders in human, as well as about one-fifth of annual global green-house gas emissions. Therefore, production of meats with healthier fatty acid profiles that are also environmentally sustainable, is of major interest to the meat industry. Oil palm fronds (OPF) have been used in ruminant feeds as a source of roughage. The incorporation of OPF in the diet has been shown to improve meat quality, and reduced saturated fatty acids (SFA) content in the meat. Being a readily available and abundant agriculture byproduct, OPF has the potential of being utilized as a feed source. The potency of OPF in improving rumen fermentation and nutrient digestion is related to the phytochemical compounds found in OPF. Therefore, it is logical to investigate the feasibility of using OPF extracts to improve ruminal nutrient digestion and meat quality, while restricting methane emissions from the ruminant. In view of the significance and potential applications of oil palm leaves extract (OPLE), the current study investigated the effects of OPLE on growth performance, carcass characteristics, meat quality and tissue fatty acid profiles in Boer goats, fed diets supplemented with different concentrations of OPLE. Nutritional and physiological changes in the rumen as a result of OPLE supplementation such as changes in rumen fermentation, gas production and as well as the composition of microbial populations were evaluated. The present study was conducted in three phases at Universiti Putra Malaysia (UPM). In the first phase, oil palm leaves were obtained and subjected to extraction and characterization procedures. Oil palm leaf extract (OPLE) was extracted using methanol and characterized. Anti-oxidant activity of OPLE and the associated compounds were identified using gas chromatography-mass spectrometry (GC-MS).In the second phase of the study, the effects of OPLE on in vitro methane production, in vitro and in vivo rumen fermentation, bio-hydrogenation and microbial population were determined. In the third phase, the effects of OPLE supplementation was performed on 21 Boer goats. The study investigated the growth performance, nutrient digestibility, carcass characteristics, meat quality, tissue fatty acid profile and rumen characteristics following OPLE supplementation at different concentrations in goats. Rumen bio-hydrogenation and fermentation, fatty acid composition of the rumen digests, lipid content of the liver, muscles, subcutaneous fatty acid and adipose tissue were also determined. Other parameters that were investigated, included the PPARα, PPARγ and Stearoyl CoA desaturase (SCD) gene expression in LD muscle and liver. Results showed that oil palm leaves produced significant amount of methanolic OPLE extract. Methanolic extraction of oil palm leaves produced higher (8.28%) phenolic compounds compared to hexane (3.10%) and chloroform (3.08%). The results also confirmed that OPLE possessed potent anti-oxidant activity as well as strong scavenging activity of 2,2-Diphenyl-1-picrylhydrazyl (DPPH). The GC-MS results revealed the presence of 56 compounds in OPLE. In vitro gas and methane production in goats was also reduced significantly following dietary OPLE supplementation in goats. There were also changes in the rumen bacterial flora following OPLE supplementation, an indication that the OPLEcompounds had selective antimicrobial effects. Additionally, acetic and butyric acid concentrations were increased, while propionic acid contents declined. The volatile fatty acids (VFA) content were no different between OPLE supplemented and non-supplemented groups in both in vitro and in vivo studies. Overall, the totalVFA concentration was not affected by the addition of 7.5 mg/kg dry matter (DM) of extract compared to control, suggesting that the OPLE did not affect ruminal digestion adversely. Significant reduction in the concentration of saturated fatty acids (SFA) in the OPLE treated groups was also recorded. The present study also established that OPLE caused induction in color stability, reduction in lipid oxidation, cholesterol levels, in vitro bio-hydrogenation as well as reduction in SFA in meat samples and stabilization in meat pH. Other findings included the fact that OPLE supplement did not affect rumen fermentation and nutrients digestibility despite the positive effect of OPLE supplement on rumen biohydrogenation (BH). Based on the findings of the study, it is concluded that OPLE had the potential to be employed as a supplement in ruminant diet which could enhance the production of higher quality ruminant meat. Using OPLE as supplement in goat fattening diets alsomitigated gas and methane production in rumen without affecting rumen fermentation. The 56 compounds identified in the study could be further refined to serve as feed supplements in industries associated with animal nutrition and production.

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