Table 1.

Summary of the data used in the meta-analysis of the effect of different strategies for enteric methane abatement.

Study code	Source	Animal	Strategy	Methane analysis method	n
1	Alemu et al. (2019)	Sheep	Phytochemicals, NO3-	GreenFeed	22
2	Beauchemin et al. (2006)	Beef	Phytochemicals, oil, organic acid	Chamber	8
3	Beauchemin et al. (2007)	Beef	Oil	Chamber	4
4	Beauchemin et al. (2009)	Dairy	Oil, protozoa control	Chamber	4
5	Benchaar (2016)	Dairy	Phytochemicals, ionophores	SF6	8
6	Benchaar et al. (2015)	Dairy	Oil, protozoa control	Chamber	6
7	Bird et al. (2008)	Sheep	Protozoa control	Chamber	7
8	Caetano et al. (2019)	Beef	Phytochemicals	GreenFeed	10
9	Carulla et al. (2005)	Sheep	Phytochemicals, protozoa control	Chamber	6
10	Carvalho et al. (2016)	Beef	Oil	SF6	9
11	Chung et al. (2013)	Beef	Phytochemicals, protozoa control	Chamber	8
12	Cooprider et al. (2011)	Beef	Ionophores	Chamber	4
13	Cosgrove et al. (2008)	Sheep	Oil	SF6	2
14	Ding et al. (2012)	Sheep	Oil	other	3
15	Duthie et al. (2018)	Beef	NO3-	Chamber	18
16	El-Zaiat et al. (2014)	Sheep	Phytochemicals, NO3-	Chamber	6
17	Fiorentini et al. (2014)	Beef	Oil, protozoa control	SF6	9
18	Grainger et al. (2008)	Dairy	Oil	SF6	6
19	Grainger et al. (2008b)	Dairy	Ionophores	Chamber/SF6	15
20	Grainger et al. (2009)	Dairy	Phytochemicals	SF6	10
21	Grainger et al. (2010)	Dairy	Ionophores	Chamber/SF6	10/15
22	Granja-Salcedo et al. (2019)	Beef	NO3-	SF6	10
23	Guyader et al. (2015a)	Dairy	phytochemicals, NO3-	Chamber	4
24	Guyader et al. (2015b)	Dairy	Oil, NO3-, protozoa control	Chamber	4
25	Guyader et al. (2016)	Dairy	Oil, NO3-	Chamber	8
26	Haisan et al. (2014)	Dairy	3-nitrooxypropanol (3-NOP)	SF6	5
27	Haisan et al. (2017)	Dairy	3-NOP	SF6	6
28	Hegarty et al. (2008)	Sheep	Protozoa control	Chamber	6
29	Hess et al. (2016)	Sheep	Phytochemicals, protozoa control	Chamber	6
30	Hollmann et al. (2012)	Dairy	Oil	Chamber	6
31	Holtshausen et al. (2009)	Dairy	Phytochemicals, protozoa control	Chamber/SF6	4
32	Hosoda et al. (2005)	Dairy	Phytochemicals	Chamber	4
33	Hristov et al. (2013)	Dairy	Phytochemicals	SF6	8
34	Hristov et al. (2015)	Dairy	3-NOP	GreenFeed	12
35	Hulshof et al. (2012)	Beef	NO3-	SF6	8
36	Hünerberg et al. (2013a)	Beef	Oil	Chamber	8
37	Hünerberg et al. (2013b)	Beef	Oil	Chamber	4
38	Johnson et al. (2002)	Dairy	Oil	SF6	4
39	Jordan et al. (2006a)	Beef	Oil	Chamber	10
40	Jordan et al. (2006b)	Beef	Oil	SF6	12
41	Jordan et al. (2007)	Beef	Oil	SF6	4
42	Jose Neto et al. (2019)	Beef	Oil	SF6	9
43	Kim et al. (2019)	Beef	3-NOP	GreenFeed	9
44	Kinley et al. (2020)	Beef	Seaweed	Chamber	5
45	Klevenhusen et al. (2011)	Sheep	Phytochemicals, protozoa control	Chamber	6
46	Lee et al. (2015)	Beef	NO3-	Chamber	8
47	Lee et al. (2017)	Beef	NO3-	Chamber	7
48	Lee et al. (2017)	Beef	NO3-	Chamber	7
49	Li et al. (2012)	Sheep	NO3-	Chamber	5
50	Li et al. (2013)	Sheep	NO3-	Chamber	6
51	Li et al. (2018)	Sheep	Seaweed	Chamber	6
52	Liu et al. (2011)	Sheep	Phytochemicals, oil	Chamber	8
53	Lopes et al. (2016)	Dairy	3-NOP	GreenFeed	6
54	Ma et al. (2015)	Sheep	Phytochemicals	Chamber	6
55	Ma et al. (2017)	Sheep	Phytochemicals	Chamber	6
56	Machmüller et al. (2000)	Sheep	Oil, protozoa control	Chamber	3
57	Machmüller et al. (2001)	Sheep	Oil, protozoa control	Chamber	3
58	Machmüller et al. (2003)	Sheep	Oil, protozoa control	Chamber	3
59	Malik et al. (2017)	Sheep	Phytochemicals, protozoa control	SF6	10
60	Mao et al. (2010)	Sheep	Phytochemicals, oil	Chamber	8
61	Martin et al. (2008)	Dairy	Oil	SF6	8
62	Martin et al. (2016)	Dairy	Oil	SF6	4
63	Martinez-Fernandez et al. (2018)	Beef	3-NOP	Chamber	4
64	McGinn et al. (2004)	Beef	Oil, organic acid, ionophores	Chamber	8
65	McGinn et al. (2009)	Beef	Oil	SF6	30
66	Melgar et al. (2020)	Dairy	NO3-	GreenFeed	24
67	Moate et al. (2011)	Dairy	Oil	Chamber	4
68	Moate et al. (2014)	Dairy	Phytochemicals, protozoa control	SF6	10
69	Mohammed et al. (2004)	Dairy	Phytochemicals, protozoa control	Chamber	4
70	Moreira et al. (2013)	Sheep	Phytochemicals	SF6	3
71	Mwenya et al. (2005)	Dairy	Ionophores	Other	4
72	Newbold et al. (2014)	Beef	NO3-	Chamber	6
73	Nguyen and Hegarty (2017)	Beef	Oil, protozoa control	Chamber	6
74	Nolan et al. (2010)	Sheep	NO3-	Chamber	4
75	Norris et al. (2020)	Beef	Phytochemicals, protozoa control	Chamber	8
76	Odongo et al. (2007)	Dairy	Oil	Chamber	6
77	Odongo et al. (2007b)	Dairy	Ionophores	Other	12
78	Olijhoek et al. (2016)	Dairy	NO3-	Chamber	4
79	de Oliveira et al. (2007)	Beef	Phytochemicals	SF6	8
80	Patra et al. (2011)	Sheep	Phytochemicals	Chamber	4
81	Pen et al. (2007)	Sheep	Phytochemicals	Chamber	4
82	Rebelo et al. (2009)	Beef	NO3-	SF6	10
83	Reynolds et al. (2014)	Dairy	3-NOP	GreenFeed	6
84	Romero-Perez et al. (2014)	Beef	3-NOP	Chamber	8
85	Romero-Perez et al. (2015)	Beef	3-NOP	Chamber	8
86	Roque et al. (2019)	Dairy	Seaweed	GreenFeed	12
87	Rossi et al. (2017)	Beef	Oil	SF6	7
88	Santoso et al. (2004)	Sheep	Phytochemicals	Chamber	4
89	Silva et al. (2018)	Beef	Oil	SF6	6
90	Soltan et al. (2013)	Sheep	Phytochemicals	Chamber	6
91	Staerfl et al. (2012)	Beef	Phytochemicals, protozoa control	Chamber	6
92	Sun et al. (2017)	Beef	NO3-	Chamber	4
93	Tiemann et al. (2008)	Sheep	Phytochemicals	Chamber	6
94	Troy et al. (2015)	Beef	Oil, NO3-	Chamber	6
95	Van Wesemael et al. (2019)	Dairy	3-NOP	GreenFeed	10
96	van Zijderveld et al. (2010)	Sheep	NO3-	Chamber	5
97	van Zijderveld et al. (2011a)	Dairy	Oil, Phytochemicals	Chamber	10
98	van Zijderveld et al. (2011b)	Dairy	NO3-	Chamber	5
99	Velazco et al. (2014)	Beef	NO3-	GreenFeed	10
100	Veneman et al. (2015)	Dairy	oil, NO3-	Chamber	6
101	Villar et al. (2019)	Beef	oil, NO3-	Chamber	4
102	Vyas et al. (2016)	Beef	3-NOP	Chamber	5
103	Vyas et al. (2018a)	Beef	3-NOP	Chamber	5
104	Vyas et al. (2018b)	Beef	3-NOP, ionophores	Chamber	5
105	Waghorn et al. (2008)	Dairy	Ionophores	SF6	16
106	Wang et al. (2009)	Sheep	Phytochemicals	Chamber	4
107	Yang et al. (2017)	Beef	Phytochemicals, protozoa control	Chamber	4
108	Zhou et al. (2011)	Sheep	Phytochemicals, protozoa control	Chamber	3

n = total number of animals.