Methane reduction, health and regulatory considerations regarding Asparagopsis and bromoform for ruminants

Figures & data

Table 1. Summary of studies in ruminants fed Asparagopsis^a with details of the studies, and the methane response (reduction) expressed per mg of bromoform.

Reference and pertinent experimental design details	DMI (kg/day)	Methane (g per kg Dry Matter Intake, DMI)	Asparagopsis inclusion rate in diet (DM basis)	Treatment (days)	Number of animals	Methane response (g/kg DMI compared with control)	Methane response: kg per gram bromoform	Inclusion rate of bromoform (mg/kg diet DM or g/tonne diet DM)	Bromoform (mg per day)	Bromoform (mg per kg LW)
Dried Asparagopsis systems
Kinley^b	Feedlot steers		Brahman-Angus (477/604 kg)			A. armata - Bromoform (6.55 mg per g seaweed DM)
	9.3	0.2	0.33%	30 + 60	5	10.8	0.50	21.8	202	0.37
	10.8	6.8	0.17%	30 + 60	5	4.2	0.38	10.9	118	0.22
	8.0	10.0	0.08%	30 + 60	5	1.0	0.18	5.4	44	0.08
	8.9	11.0	0.00%	30 + 60	5	0	0	0	0	0
Roque^c	Lactating cows		Holstein-Friesian (729/759 kg)			A. armata - Bromoform (1.32 mg per g seaweed DM)
	17.3	8.3	1.84%	21	12	6.1	0.25	24.3	420	0.56
	24.9	11.5	0.92%	21	12	2.9	0.24	12.1	303	0.41
	27.9	14.4	0.00%	21	12	0	0	0	0	0.00
Roque^d	Feedlot steers		Hereford (352/583 kg)			A. taxiformis - Bromoform (7.8 mg per g seaweed DM)
Low Forage
High Asp	10.7	2.5	0.83%	63	7	9.9	0.15	64.4	689	1.47
Low Asp	10.8	3.8	0.45%	63	7	8.6	0.25	35.0	378	0.81
Control	11.5	12.4	0.00%	63	7	0	0	0	0	0.00
Med Forage
High Asp	10.0	3.9	0.83%	21	7	15.3	0.24	64.4	644	1.38
Low Asp	10.8	10.6	0.45%	21	7	8.6	0.25	35.0	378	0.81
Control	12.2	19.2	0.00%	21	7	0	0	0	0	0.00
High Forage
High Asp	8.4	10.6	0.83%	63	7	11.5	0.18	64.4	541	1.16
Low Asp	9.7	14.9	0.45%	63	7	7.2	0.21	35.0	340	0.73
Control	10.3	22.1	0.00%	63	7	0	0	0	0	0.00
Fennessy^e	Wether sheep		Romney-cross (42kg)			A. armata - Bromoform (6.6 mg per g seaweed DM)
	0.89	2.4	0.61%	16	5	15.9	0.37	42.5	36	0.86
	0.88	4.8	0.41%	16	6	13.5	0.50	27.1	24	0.57
	0.96	14.5	0.19%	16	6	3.8	0.30	12.8	12	0.29
	0.87	18.3	0.00%	16	5	0	0	0.0		0.00
Reference	DMI (kg/day)	Methane (g per kg Dry Matter Intake, DMI)	Asparagopsis inclusion rate in diet	Treatment (days)	Number of animals	Methane response (g/kg DMI compared with control)	Methane response: kg per gram bromoform	Inclusion rate of bromoform (mg/kg diet DM or g/tonne diet DM)	Bromoform (mg per day)	Bromoform (mg per kg LW)
Oil-based Asparagopsis system
Alvarez-Hess et al^f	Lactating cows (fed twice daily)		Holstein-Friesian (578 kg)			A. armata – Bromoform (480 mg/cow/day in canola oil ex steeped A. armata)
	30.1	24.6	NA	27	13
	28.4	13.8			11	11.4	0.67	16.9	480	0.83
	28.8	16.4			11	9.9	0.59	16.7

^a Stefenoni et al is not included as bromoform content is not presented; Muizelaar et al. is not included as there are no data on methane emissions; Li et al (2018) is not included as the bromoform content of the Asparagopsis is not defined.

^b https://doi.org/10.1016/j.jclepro.2020.120836; Methane - open-circuit chambers, CSIRO Lansdown Research Station; feed intake - physical

^c https://doi.org/10.1016/j.jclepro.2019.06.193; Feed intake - Calan gates; Methane - GreenFeed, C-Lock, Inc., Rapid City, South Dakota, USA

^d https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0247820; Methane - GreenFeed; Feed intake - Calan gates

^e Methane - open-circuit respiration chambers, AgResearch, Palmerston North, New Zealand; feed intake - physical

^f https://www.sciencedirect.com/science/article/abs/pii/S0377840123000135?dgcid=author; Methane - modified SF6 (sulphur hexafluoride) tracer technique; Feed intake - Gallagher bin weight system

Figure 1. The relationship between the reduction in methane emissions and the bromoform intake for five sets of data (the full data are in Table 1).

Table 2. Estimated dietary exposure from bromoform for a 70 kg adult based on reported background values in milk from untreated animals and with allowance for drinking water standards.

Dietary contributor	Intake (kg or L per day)^a	Residue (mg/kg or mg/L)	Exposure (mg/kg bw/day)	Percentage of WHO TDI^b
Milk	1.5	0.017	0.00036	2.0
Water	2	0.100	0.00286	15.9
Total	17.9

^a Intake values derived from WHO 2012, 2022.

^b WHO TDI: 0.018 mg/kg bw/day (WHO 2022).