The influence of feeding canola oil steeped Asparagopsis armata on resulting fatty acid profile and dairy processing properties of cow's milk

The addition of red seaweeds from the genus Asparagopsis to the diet of dairy cattle has emerged as a promising methane mitigation strategy. Research to date characterizing the effect of feeding Asparagopsis derived formulations on milk processing properties for manufacture of products such as cheese and yoghurt has been limited. With the potential for adverse changes to milk properties intrinsically connected to the cows' diet it is important to elucidate the effect of dietary methane mitigation products on milk properties. The aim of this research was to evaluate the effect of feeding two formulations of Asparagopsis armata steeped in canola oil (ASP-Oil) to lactating dairy cows on compositional and functional properties of milk. Thirty-nine lactating, multiparous, Holstein-Friesian cows were randomly allocated one of three supplement treatments that was added to a similar basal diet: control of canola oil (CON), ASP-Oil with the seaweed biomass removed (ASP1), and ASP-Oil with the seaweed biomass retained (ASP2) over a 32-day experiment. Treatments were given twice daily, using a pulse feeding technique, with the oils combined with a grain concentrate during each milking. The basal diet consisted of vetch hay ad libitum and 7.0 kg DM/d of the grain mix. Results demonstrated there was no difference in milk headspace volatiles measured in whole milk samples, or the rennet-induced and acid-induced gelation properties of skimmed milk from cows fed the CON or ASP-Oil treatment diets. Moreover, differences in the diet had only a minor effect on milk fatty acid profile. These results indicate that methane mitigation protocols that involve the introduction of A. armata to dairy cow diets can be utilized without negative effects on milk fatty acid profile, processability, or function.