Methane production – and DMI – falls when fish oil fed to beef steers
Take Home Message: The inclusion of 2% fish oil in the diet of steers will reduce methane output by approximately 25%, but will also reduce intake by 10%.
Feeding fish oil to beef steers can reduce the amount of methane they produce – good news for the environment. But not so good, however, is an associated reduction in feed intake. And the effect of this on animal performance and meat quality requires further investigation, according to scientists at University College Dublin, who carried out trials to assess the effect of feeding a concentrated fish oil to beef steers, on intakes and CH4 emissions.
Irish livestock account for 0.55 million tonnes of methane (CH4) annually from enteric fermentation and manure management, but recent studies have shown the potential to reduce ruminal methanogenesis through strategic dietary supplementation with polyunsaturated fatty acids (PUFAs).
“This is likely to be mediated, in part, through the unsaturated double bonds of PUFA acting as ‘sinks’ for free hydrogen during ruminal biohydrogenation,” said Kirstie Petrie, who led the research team in Dublin and shared its findings with delegates at this year’s British Society of Animal Science annual conference.
Six mature Limousin crossbred steers took part in the trial. Animals were housed in slatted floor pens and fed individually. Feed was offered in two equal portions at 8.00am and 4.00pm daily. Steers were fed a 50:50 forage:concentrate diet, with barley straw as the forage source. Intakes were restricted to 95% of voluntary intake.
Three concentrates were manufactured to supply fish oil at zero, 1% and 2% DMI and all diets were formulated to be iso-nitrogenous (14% CP DM). The fish oil contained 43% EPA and 19% DHA. Dry matter intake was measured daily.
Following a 21-day dietary adaptation period, daily CH4 emissions were measured on all steers on days 23 to 27 of each of three 28-day experimental periods, using the sulphur hexafluoride (SF6) tracer technique.
The CH4 and SF6 samples collected from the steers were analysed by gas chromatography and adjusted for ambient concentrations.
“And we found that dietary supplementation with 2% fish oil resulted in a decrease of both daily and intake corrected CH4 production,” said Miss Petrie. “But this was associated with a linear decrease in intake – 9.5% – in the animals fed at the 2% level. The greatest incremental decrease in both absolute and feed intake corrected CH4 emissions was recorded between 1 and 2% dietary fish oil inclusion,” she added
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