Heritability estimates of enteric methane emissions predicted from fatty acid profiles, and their relationships with milk composition, cheese-yield and body size and condition

Figures & data

Table 1. Descriptive statistics of all the investigated traits.

Item	Mean	SD
Estimated Methane emissions^a
CH4/DMI, g/kg	21.34	1.58
CH4/CM, g/kg	14.26	1.63
dCH4, g/d	358	104
CH4/CYCURD, g/kg	100	16
CH4/CYSOLIDS, /kg	208	31
dDMIest, kg/d	17.1	5.5
Informative milk FAs (%FA)^b
4:0 - Butyric acid	3.45	0.90
16:0iso - Iso-Palmitic acid	0.32	0.09
18:1t10	0.29	0.09
18:1t11 - Vaccenic acid	1.20	0.37
18:1c9 - Oleic acid	18.33	3.19
18:2c9,c12 - Linoleic acid	2.04	0.59
Quality traits^c
Milk fat, %	4.23	0.72
Milk protein, %	3.71	0.43
%CYCURD, %	15.06	1.89
%CYSOLIDS, %	7.23	0.94
Daily yield traits^d
dMY, kg/d	24.5	7.9
dCMY, kg/d	25.6	8.1
dCYCURD, kg/d	3.66	1.17
dCYSOLIDS, k/d	1.76	0.57
Body size and condition
Heart girth, cm	200	8
Est. body weight, kg	668	51
Body condition score	2.97	0.34

^a Estimated Methane Emissions: CH₄/DMI, g/kg: methane yield, emitted per kg DMI; CH₄/CM, g/kg: methane intensity per kg fat and protein corrected milk produced; dCH₄, g/kg: daily methane production per cow; CH₄/CY_CURD, g/kg: methane intensity per kg of fresh cheese produced; CH₄/CY_SOLIDS g/kg: methane intensity per kg of cheese solids produced; dDMI_est, kg/d: estimated daily DMI of cows.

^b Informative milk FAs are the fatty acids included as independent variables in the equations used to estimate the enteric methane emissions (van Lingen et al. 2014).

^c Quality traits: %CY_CURD: wt of fresh cheese as % of processed milk; %CY_SOLIDS: wt of cheese solids as % of processed milk.

^d Daily yield traits: dMY: daily milk yield; dCMY: daily fat and protein corrected milk yield; dCY_CURD: daily production of fresh cheese per cow; dCY_SOLIDS: daily production of cheese solids.

Table 2. Marginal posterior densities of genetic variance (${\sigma }_{\mathrm{a}}^2$), herd-date variance (${\sigma }_{\mathrm{h}}^2$), residual variance (${\sigma }_{\mathrm{e}}^2$), heritability $(h^2)$ and herd-date variance as proportion of total variance $(\mathrm{HD})$ for all the investigated traits.

Item	Variances			$h^2$		$\mathrm{HD}$
	${\sigma }_{\mathrm{a}}^2$	${\sigma }_{\mathrm{h}}^2$	${\sigma }_{\mathrm{e}}^2$	Mean	HPD95^a	Mean
Estimated Methane emissions^b
CH4/DMI, g/kg	0.18	1.78	0.53	0.25	0.10; 0.43	0.71
CH4/CM, g/kg	0.12	1.45	0.94	0.12	0.01; 0.28	0.57
dCH4, g/d	916	4166	4371	0.17	0.02; 0.28	0.44
CH4/CYCURD, g/kg	17	149	88	0.16	0.03; 0.32	0.59
CH4/CYSOLIDS, /kg	82	497	317	0.20	0.05; 0.41	0.55
dDMIest, kg/d	1.7	13.3	11.6	0.12	0.02; 0.28	0.50
Informative milk FAs (%FA)^c
4:0 - Butyric acid	0.024	0.436	0.299	0.07	0.01; 0.20	0.57
16:0iso - Iso-Palmitic acid	0.001	0.004	0.003	0.18	0.07; 0.33	0.53
18:1t10	0.001	0.005	0.004	0.20	0.04; 0.43	0.51
18:1t11 - Vaccenic acid	0.011	0.089	0.041	0.20	0.06; 0.39	0.63
18:1c9 - Oleic acid	0.980	1.719	5.993	0.14	0.02; 0.33	0.20
18:2c9,c12 - Linoleic acid	0.025	0.247	0.091	0.21	0.08; 0.42	0.68
Quality traits^d
Milk fat, %	0.054	0.103	0.356	0.13	0.03; 0.29	0.20
Milk protein, %	0.023	0.023	0.058	0.28	0.12; 0.49	0.22
%CYCURD, %	0.513	0.920	1.568	0.25	0.11; 0.42	0.31
%CYSOLIDS, %	0.143	0.155	0.468	0.23	0.09; 0.41	0.20
Daily yield traits^e
dMY, kg/d	2.85	22.84	19.80	0.13	0.02; 0.27	0.50
dCMY, kg/d	3.35	25.21	24.28	0.12	0.02; 0.24	0.47
dCYCURD, kg/d	0.085	0.628	0.484	0.15	0.01; 0.39	0.52
dCYSOLIDS, k/d	0.021	0.143	0.120	0.15	0.04; 0.29	0.50
Body size and condition
Heart girth, cm	13	15	35	0.27	0.07; 0.51	0.24
Est. body weight, kg	438	601	1340	0.25	0.08; 0.44	0.25
Body condition score	0.026	0.021	0.050	0.33	0.17; 0.51	0.23

^a HPD95: bounds of the 95% high posterior density interval.

^b Estimated Methane Emissions: CH₄/DMI, g/kg: methane yield, emitted per kg DMI; CH₄/CM, g/kg: methane intensity per kg fat and protein corrected milk produced; dCH₄, g/kg: daily methane production per cow; CH₄/CY_CURD, g/kg: methane intensity per kg of fresh cheese produced; CH₄/CY_SOLIDS g/kg: methane intensity per kg of cheese solids produced; dDMI_est, kg/d: estimated daily DMI of cows.

^c Informative milk FAs are the fatty acids included as independent variables in the equations used to estimate the enteric methane emissions (van Lingen et al. 2014).

^d Quality traits: %CY_CURD: wt of fresh cheese as % of processed milk; %CY_SOLIDS: wt of cheese solids as % of processed milk.

^e Daily yield traits: dMY: daily milk yield; dCMY: daily fat and protein corrected milk yield; dCY_CURD: daily production of fresh cheese per cow; dCY_SOLIDS: daily production of cheese solids.

Table 3. Sensitivity analysis of the heritability ($h^2$) and herd effect (HD) obtained excluding alternatively from the entire dataset of phenotyped cows those belonging to the extreme dairy systems (traditional farms with tied cows or modern farms using total mixed rations), or parities (primiparous or old cows), or lactation stages (fresh cows and late lactation cows).^a

Item	Entire dataset	All dairy systems excluded		All parities excluded		Entire lactation excluded
		Tied cows	Modern TMR	1st	≥ 4th	DIM <60 d	DIM >240 d
Cows with EME, N.	1,091	753	746	768	817	926	762
CH4/DMI, g/kg
h^2, mean	0.25	0.29	0.31	0.34	0.31	0.25	0.17
h^2, SD	0.08	0.10	0.11	0.12	0.11	0.08	0.08
HD, mean	0.71	0.68	0.69	0.70	0.69	0.73	0.70
CH4/CM, g/kg
h^2, mean	0.12	0.25	0.21	0.14	0.09	0.09	0.29
h^2, SD	0.06	0.11	0.09	0.09	0.04	0.04	0.14
HD, mean	0.57	0.59	0.55	0.54	0.56	0.64	0.54
CH4/CYCURD, g/kg
h^2, mean	0.16	0.17	0.22	0.15	0.18	0.16	0.39
h^2, SD	0.08	0.08	0.09	0.08	0.09	0.07	0.13
HD, mean	0.59	0.56	0.58	0.55	0.58	0.61	0.58
CH4/CYSOLIDS, g/kg
h^2, mean	0.20	0.24	0.30	0.22	0.19	0.15	0.39
h^2, SD	0.09	0.10	0.12	0.10	0.09	0.08	0.12
HD, mean	0.55	0.54	0.54	0.52	0.55	0.59	0.53
dCH4:
h^2, mean	0.17	0.23	0.24	0.21	0.21	0.16	0.15
h^2, SD	0.08	0.10	0.10	0.10	0.11	0.09	0.08
HD, mean	0.44	0.30	0.41	0.46	0.44	0.44	0.46

^a Boldface indicates estimated average $h^2$ values of reduced datasets being at least 1.0 SD unit above or below the corresponding estimated h² value of the entire dataset.

Estimated Methane Emissions (EME): CH₄/DMI, g/kg: methane yield, emitted per kg DMI; CH₄/CM, g/kg: methane intensity per kg fat and protein corrected milk produced; CH₄/CY_CURD, g/kg: methane intensity per kg of fresh cheese produced; CH₄/CY_SOLIDS g/kg: methane intensity per kg of cheese solids produced; dCH₄: daily methane production per cow.

Table 4. Mean of the marginal posterior distribution of additive genetic correlations among the estimated EME traits and between EME traits and informative milk fatty acids (FAs), milk quality, daily yield, and body size traits.^a

Item	Yield	Intensity			Production
	CH4/DMI	CH4/CM	CH4/CYCURD	CH4/CYSOLIDS	dCH4
Estimated EME traits^b
CH4/CM, g/kg	0.53	–
CH4/CYCURD, g/kg	0.78	0.68	–
CH4/CYSOLIDS, /kg	0.76	0.76	0.94	–
dCH4, g/d	0.02	0.23	0.10	0.27	–
Informative milk FAs (%FA)^c
4:0 - Butyric acid	0.03	−0.72	−0.19	0.07	0.04
16:0iso - Iso-Palmitic acid	0.64	0.03	0.45	0.56	−0.49
18:1t10	−0.43	−0.64	−0.39	−0.10	−0.65
18:1t11 - Vaccenic acid	−0.06	−0.48	−0.24	−0.31	−0.86
18:1c9 - Oleic acid	−0.25	−0.89	−0.54	−0.79	−0.70
18:2c9,c12 - Linoleic acid	−0.92	−0.65	−0.78	−0.66	−0.05
Quality traits^d
Milk fat, %	−0.64	0.15	−0.19	−0.24	0.27
Milk protein, %	−0.53	−0.03	−0.35	−0.47	−0.23
%CYCURD, %	−0.81	0.00	−0.64	−0.54	0.26
%CYSOLIDS, %	−0.70	−0.17	−0.49	−0.62	0.04
Daily yield traits^e
dMY, kg/d	0.08	−0.19	−0.03	0.17	0.84
dCMY, kg/d	−0.28	−0.26	−0.28	−0.14	0.95
dCYCURD, kg/d	−0.48	−0.18	−0.50	−0.24	0.91
dCYSOLIDS, k/d	−0.33	−0.16	−0.41	−0.40	0.86
Body size and condition
Heart girth, cm	0.32	0.20	−0.18	0.09	−0.63
Estimated body weight, kg	0.31	0.40	0.26	0.44	−0.65
Body condition score	0.03	0.14	−0.09	−0.17	−0.74

^a Boldface indicates additive genetic correlations with >95% of posterior probability accumulated above 0 (positive estimates) or below 0 (negative estimates).

^b Estimated Methane Emissions: CH₄/DMI, g/kg: methane yield, emitted per kg DMI; CH₄/CM, g/kg: methane intensity per kg fat and protein corrected milk produced; dCH₄, g/kg: daily methane production per cow; CH₄/CY_CURD, g/kg: methane intensity per kg of fresh cheese produced; CH₄/CY_SOLIDS g/kg: methane intensity per kg of cheese solids produced; dDMI_est, kg/d: estimated daily DMI of cows.

^c Informative milk FAs are the fatty acids included as independent variables in the equations used to estimate the enteric methane emissions (van Lingen et al. 2014).

^d Quality traits: %CY_CURD: wt of fresh cheese as % of processed milk; %CY_SOLIDS: wt of cheese solids as % of processed milk.

^e Daily yield traits: dMY: daily milk yield; dCMY: daily fat and protein corrected milk yield; dCY_CURD: daily production of fresh cheese per cow; dCY_SOLIDS: daily production of cheese solids.

Estimated Methane Emissions (EME): CH₄/DMI, g/kg: methane yield, emitted per kg DMI; CH₄/CM, g/kg: methane intensity per kg fat and protein corrected milk produced; CH₄/CY_CURD, g/kg: methane intensity per kg of fresh cheese produced; CH₄/CY_SOLIDS g/kg: methane intensity per kg of cheese solids produced; dCH₄: daily methane production per cow.

van Lingen HJ, Crompton LA, Hendriks WH, Reynolds CK, Dijkstra J. 2014. Meta-analysis of relationships between enteric methane yield and milk fatty acid profile in dairy cattle. J Dairy Sci. 97(11):7115–7132.

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