Twice daily feeding of canola oil steeped with Asparagopsis armata reduced methane emissions of lactating dairy cows

Abstract

Red seaweeds have emerged as a potent methane-mitigating feed additive in ruminant diets. However, to date they have only been applied to production systems where total mixed rations (TMR) are given. New formulations are being developed to increase the application of red seaweeds, mainly Asparagopsis spp., across different production systems including those without TMR such as grazing-based systems. One product of interest is Asparagopsis armata steeped in edible oil (ASP-Oil) to extract and stabilise the primary antimethanogenic compound, bromoform. The aim of this study was to determine the effect of feeding two formulations of ASP-Oil, with (ASP-Oil 1) and without (ASP-Oil 2) the seaweed biomass removed, on enteric methane emissions, dry matter intake (DMI), milk yield and milk composition of dairy cows over 32 d. Thirty-nine lactating, multiparous, Holstein-Friesian (75 ± 20.6 days in milk) were randomly allocated to one of the three treatments; control (CON; basal diet + 134 g canola oil), ASP-Oil with the seaweed biomass removed (ASP1; basal diet + 134 g ASP-Oil 1), and ASP-Oil without the seaweed biomass removed (ASP2; basal diet + 145 g ASP-Oil 2 + 12 g canola oil). The treatments were given twice daily, using a pulse feeding technique, as a concentrate/oil supplement during each milking. The basal diet consisted of vetch hay ad libitum and 7.0 kg DM/d of a grain mix. Individual forage intakes were measured daily via electronic monitoring of individual cows at the feed bins. Methane emissions were measured using the modified sulphur hexafluoride tracer technique on days 27–32. At the rate of 136 g/d, there was no significant effect of treatment on DMI or milk yield, however during the transition period a rate of 268 g/d decreased hay intake. The supplementation of ASP1 and ASP2 decreased energy corrected milk (ECM; P = 0.029) compared to those cows offered the CON diet. Methane production (g/d) of cows given the ASP1 diet was 44 % lower than cows on the CON diet, methane yield (g/kg DMI) was 44 % lower, and methane intensity (g/kg ECM) was 38 % lower. For the ASP2 cows, the reductions were 39 % for methane production, 33 % for methane yield, and 31 % for methane intensity. Feeding the ASP-Oil increased bromoform concentrations in milk. However, the concentrations detected were demonstrated to be considerably lower than published safe concentrations in milk for human consumption (100 μg/L). These results show that the ASP-Oil has potential to be used as a methane mitigating feed additive when fed in a pulse feeding system.