Phenotypic and genetic characterisation of methane emission predicted from milk fatty acid profile of Sarda dairy ewes

Figures & data

Table 1. Equation retrieved in literature for estimating methane yield and intensity in dairy cows.

Methane	Equation		Reference
Yield, g/kg DMI	23.39 + 9.74 × C16:0iso – 1.06 × (C18:1t10 + C18:1t11) – 1.75 × C18:2c9,c12	(1)	van Lingen et al. (2014)
	24.6 + 8.74 × C17:0anteiso – 1.97 × (C18:1t10 + C18:1t11) – 9.09 × C18:1c11 + 5.07 × C18:1c13	(2)	Dijkstra, Van Zijderveld, et al. (2011)
	27.13 – 3.04 × C4:0 + 2.71 × C6:0 – 1.63 × (C18:1t10 + C18:1t11)	(3)	Van Engelen et al. (2015)
	27.2 – 7 × CLAc9,t11	(4)	van Gastelen et al. (2017)
	22.9 + 20.9 × C15:0iso – 9.6 × C15:0anteiso + 7.6 × C17:0 – 2.4 × C18:1t11 – 2.7 × C18:1c11 – 4.4 × C18:3n3	(5)	van Gastelen et al. (2018)
	21.0 + 10.5 × C16:0iso – 2.7 × C18:1c11 – 0.8 × C18:1t10 – 1.1 × C18:2c9,c12	(6)	Bougouin et al. (2019)
Intensity, g/kg FPCM	21.13 – 1.38 × C4:0 + 8.53 × C16:0iso – 0.22 × C18:1cis-9 – 0.59 × (C18:1t10 + C18:1t11)	(7)	van Lingen et al. (2014)
	16.5 + 24.6 × C15:0iso – 15.5 × C17:0 + 52.4 × C22:0	(8)	van Gastelen et al. (2017)
	8 + 24.8 × C15:0iso + 10.3 × C17:0iso – 6.6 × C18:1c11 + 22.7 × DPA	(9)	van Gastelen et al. (2018)

DMI: dry matter intake; FPCM: fat and protein corrected milk.

Table 2. Description of the involved dataset.

Effect	Level of the effect	Number of ewes
DIM	1	118
	2	219
	3	256
	4	251
	5	120
Parity	1	180
	2	121
	3	148
	4	162
	5	115
	6	94
	7	144
Lambing month	1	145
	2	124
	3	399
	4	296

DMI: dry matter intake.

Table 3. Descriptive statistic of methane yield (CH₄, g/kg DMI) and methane intensity (CH₄, g/kg FPCM) estimation using published equations.

Equation	Mean	SD	Min	Max	Reference
Methane yield, CH4, g/kg DMI
(1)	20.4	1.5	10.4	25.6	Van Lingen et al. (2014)
(2)	19.4	2.4	4.3	24.2	Dijkstra, Van Zijderveld, et al. (2011)
(3)	19.8	2.1	5.8	24.1	Van Engelen et al. (2015)
(4)	20.0	3.3	5.1	25.2	Van Gastelen et al. (2017)
(5)	19.6	4.6	4.3	30.0	Van Gastelen et al. (2018)
(6)	20.4	1.0	12.8	24.0	Bougouin et al. (2019)
Mean (1)–(6)	19.9	2.1	10.5	24.2
Methane intensity, CH4, g/kg FPCM
(7)	15.1	1.1	10.2	19.2	Van Lingen et al. (2014)
(8)	21.0	3.6	4.2	37.8	Van Gastelen et al. (2017)
(9)	19.8	2.8	10.0	29.8	Van Gastelen et al. (2018)
Mean (7)–(9)	18.7	2.0	10.3	26.2

Mean values for methane yield or methane intensity were the average of the equations across animals.

DMI: dry matter intake; FPCM: fat and protein corrected milk.

Figure 1. Effect of lactation stage (days in milk, DIM) on methane yield (a) and methane intensity (b). DMI: dry matter intake; FPCM: fat and protein corrected milk.

Figure 2. Phenotypic correlations estimated between methane emission (yield and intensity) and other milk traits. Bold values indicate significant correlation (p < .05).

Table 4. Heritability, variance explained by the flock test date and genetic correlations estimated for methane yield and intensity using the bivariate models.

	Heritability		Flock test day contribution		Genetic correlations
Trait	eMY	eMI	eMY	eMI	eMY	eMI
Milk daily production	0.12 ± 0.05	0.04 ± 0.03	0.64 ± 0.05	0.65 ± 0.05	−.05  ± 0.32	−.32  ± 0.59
Fat	0.14 ± 0.05	0.03 ± 0.03	0.63 ± 0.05	0.65 ± 0.05	0.64 ± 0.20	0.04 ± 0.53
Protein	0.12 ± 0.05	0.04 ± 0.03	0.64 ± 0.05	0.65 ± 0.05	0.35 ± 0.37	−.37e ± 0.55
Lactose	0.12 ± 0.05	0.05 ± 0.03	0.64 ± 0.05	0.65 ± 0.05	−.05o ± 0.28	−.28o ± 0.36
pH	0.11 ± 0.05	0.04 ± 0.03	0.64 ± 0.05	0.65 ± 0.05	−.05o ± 0.34	−.34o ± 0.51
Casein	0.12 ± 0.05	0.03 ± 0.03	0.64 ± 0.05	0.65 ± 0.05	0.40 ± 0.36	−.36i ± 0.60
Urea	0.12 ± 0.05	0.07 ± 0.04	0.64 ± 0.05	0.65 ± 0.05	0.29 ± 0.44	0.68 ± 0.34
NaCl	0.11 ± 0.05	0.04 ± 0.03	0.64 ± 0.05	0.65 ± 0.05	0.09 ± 0.30	0.43 ± 0.43
SCS	0.11 ± 0.06	0.02 ± 0.03	0.64 ± 0.05	0.66 ± 0.05	0.26 ± 0.68	−.68i ± 0.39
Methane yield		0.06 ± 0.04		0.63 ± 0.05		0.46 ± 0.38
Methane intensity	0.12 ± 0.05		0.64 ± 0.05		0.46 ± 0.38
Mean chain length	0.11 ± 0.05	0.06 ± 0.05	0.65 ± 0.05	0.64 ± 0.05	0.05 ± 0.48	0.75 ± 0.30
Mean unsaturation	0.10 ± 0.05	0.06 ± 0.04	0.64 ± 0.05	0.65 ± 0.05	−.05  ± 0.33	0.72 ± 0.30
Mean cis unsaturation	0.10 ± 0.04	0.08 ± 0.04	0.65 ± 0.05	0.65 ± 0.05	0.21 ± 0.39	0.82 ± 0.20
Mean trans unsaturation	0.16 ± 0.06	0.04 ± 0.03	0.59 ± 0.05	0.65 ± 0.05	−.05  ± 0.03	−.03  ± 0.51
Cis/trans ratio	0.13 ± 0.05	0.05 ± 0.03	0.62 ± 0.05	0.65 ± 0.05	0.77 ± 0.14	0.67 ± 0.29

eMY: methane yield (CH₄, g/kg DMI); eMI: methane intensity (CH₄, g/kg FPCM).

DMI: dry matter intake; FPCM: fat and protein corrected milk.

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Data availability statement

The data supporting this study may be available from the corresponding author upon reasonable request.