Objective The present study was conducted to select a plant oil without inhibitory effects on rumen fermentation and microbes, and to determine the optimal supplementation level of the selected oil in a series of in vitro studies for dietary application. Then, the selected oil was evaluated in a feeding study using Thai crossbred beef cattle by monitoring growth, carcass, blood and rumen characteristics. Methods Rumen fluid was incubated with substrates containing one of three different types of plant oil (coconut oil, palm oil, and soybean oil) widely available in Thailand. The effects of each oil on rumen fermentation and microbes were monitored and the oil without a negative influence on rumen parameters was selected. Then, the dose-response of rumen parameters to various levels of the selected palm oil was monitored to determine a suitable supplementation level. Finally, an 8-month feeding experiment with the diet supplemented with palm oil was carried out using 12 Thai crossbred beef cattle to monitor growth, carcass, rumen and blood profiles. Results Batch culture studies revealed that coconut and soybean oils inhibited the most potent rumen cellulolytic bacterium Fibrobacter succinogenes , while palm oil had no such negative effect on this and on rumen fermentation products at 5% or higher supplementation level. Cattle fed the diet supplemented with 2.5% palm oil showed improved feed conversion ratio (FCR) without any adverse effects on rumen fermentation. Palm oil-supplemented diet increased blood cholesterol levels, suggesting a higher energy status of the experimental cattle. Conclusion Palm oil had no negative effects on rumen fermentation and microbes when supplemented at levels up to 5% in vitro . Thai crossbred cattle fed the palm oil-supplemented diet showed improved FCR without apparent changes of rumen and carcass characteristics, but with elevated blood cholesterol levels. Therefore, palm oil can be used as a beneficial energy source.

The effects of PS were determined as a concentrate added to feed and of the days it was short-term and long-term fed to fattening dairy steers on their growth performance, carcass characteristics, meat quality, and economic return. The experimental units comprised 36 feedlot dairy steers arranged as a 2 ⋅ 3 factorial in a completely randomized design. The first term (diet factors) consisted of ground corn (GC), ground cassava (CA), or pineapple stem starch (PS) at 37% dry matter (DM) in the concentrate. The second term (feeding factors) consisted of feeding the concentrate from 1 to 206 days (short-term feeding) or from 1 to 344 days (long-term feeding). At the end of the feeding term periods, the animals were slaughtered and the growth performance, carcass characteristics, and meat quality were evaluated. The average daily gain (ADG), feed:gain ratio, dry matter intake (DMI), hot carcass and cool carcass percentages, and backfat thickness were greater for steers on short-term than on long-term feeding. Feeding the different starch sources had no negative influence on the growth performance, carcass characteristics, and meat quality. However, the ADG of steers fed PS tended (P = 0.07) to be higher than for those fed GC or CA. In addition, the concentration of the fatty acid C14:1 in the longissimus dorsi muscle was the highest in steers fed CA. Different starch sources had similar values for saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA.) Long-term feeding increased MUFA. Pineapple stem starch could be a useful feed ingredient for feedlot steers as an alternative starch source for energy.

No abstract