&lt;i&gt;In vitro&lt;/i&gt; ruminal fermentation and fatty acid production by various oil seeds

P Kubelková,D Jalč,P Homolka,F Jančík

doi:10.4314/sajas.v48i3.13

Abstract

Rumen simulating techniques (Rusitec) were used to determine the impact of diets containing milled oilseeds on the fermentation parameters and amount of fatty acids (FA) in the effluent. High-forage diets containing no oilseeds (control diet (CD)) or 10% oilseed meal from rapeseed (RS), sunflower seed (SS), or flaxseed (FS) were used on a dry matter (DM) basis. No differences in DM digestibility were observed between the diets. Inclusion of SS and FS significantly reduced the pH values of the ruminal fluid, and a significant decline in the ammonia nitrogen (NH 3 -N) (mg/d) production in effluent was observed in the vessels with SS. Generally, oilseeds in these diets significantly reduced the amount of total fermentation gases (L/d); however, only a tendency toward methane (CH 4 , %) decrease was detected. The addition of oilseeds also significantly diminished the amount of total volatile fatty acids (VFA) produced (mmol/d). Significant reductions in the amounts of saturated FA in the vessels with RS and FS were observed compared with the CD and a significantly higher amount of monounsaturated fatty acids (MUFA) was noted in the vessels with RS. An increased amount of polyunsaturated fatty acids (PUFA), compared with the CD, was statistically significant only in the vessels with FS. Keywords: Flaxseed, high-forage diet, methane, rapeseed, sunflower seed

Highlights

Fat supplements such as oilseeds are included in the diets of ruminants to increase energy density, improve nutrient utilization, enhance milk and meat yields, and modify fatty acid (FA) composition (Soder et al, 2013)
The disappearance of dry matter (DM) after 48 hours incubation was determined from the weight loss after oven drying at 55 °C for 48 hours, and the residues were analysed for neutral detergent fiber (NDF) (Van Soest et al, 1991) in the presence of sodium sulphite without α-amylase treatment and the results presented as ash free
The oilseeds contained from 182 g/kg to 225 g/kg crude protein (CP) compared with 118 g/kg in barley meal

Summary

Introduction

Fat supplements such as oilseeds are included in the diets of ruminants to increase energy density, improve nutrient utilization, enhance milk and meat yields, and modify fatty acid (FA) composition (Soder et al, 2013). Dietary fats can modify the ruminal microbial population responsible for cellulose digestion (Getachew et al, 2001), reducing the rumen degradation of fibre and organic matter (Machmüller et al, 2006). The addition of unsaturated fat sources decreased the concentration of ammonia nitrogen (NH3-N) in the rumen (Egan et al, 1986) and enhanced the effectiveness of microbial nitrogen synthesis (Oldick & Firkins, 2000). Fats with high amounts of long-chain unsaturated fatty acids, such as sunflower and rapeseed oils, depressed the emissions of CH4 by approximately 22% of the total energy received by cows fed diets with high contents of forage (McGinn et al, 2004; Beauchemin & McGinn, 2006). It has been reported that fats do not have any specific effect on CH4 release, and that the evident decrease reflects a fall in the digestibility of the ration nutrients (Beauchemin et al, 2007)

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