Effect of n-3 polyunsaturated fatty acid feeding on the fatty acid profile and odor of milk in danbred sows

Figures & data

Table 1. Composition, calculated nutrient, and analysed fatty acid content of the control and the experimental diets.

Ingredient (%)	Control	Experimental
Corn, %	44.0	44.0
Barley, %	26.7	26.7
Soybean meal, %	15.0	15.0
Vitamin and mineral premix^1, %	5.3	5.3
Alphasoy pig 530^2	3.0	3.0
Animal fat, %	2.0	2.0
Dried apple	2.0	2.0
Fish meal (70% crude protein)	1.0	1.0
Fish oil on inorganic carrier^3, %	–	1.0
Sunflower oil on inorganic carrier^3, %	1.0	–
Total, %	100.0	100.0
Nutrient/energy content (calculated values, as in feed)
Dry matter (%)	89.0	89.0
Crude protein (%)	16.0	16.0
Ether extract (%)	5.10	5.10
Crude fibre (%)	3.65	3.65
Crude ash (%)	5.30	5.30
Calcium (%)	0.80	0.80
Phosphorous (total) (%)	0.55	0.55
Sodium (%)	0.21	0.21
SID Lys^4 (%)	0.83	0.83
SID Met^4 (%)	0.28	0.28
SID Met + Cys^4 (%)	0.51	0.51
SID Thr^4 (%)	0.54	0.54
SID Trp^4 (%)	0.17	0.17
SID Val^4 (%)	0.66	0.66
MEs^5 (MJ/kg feed)	13.81	13.81
NEs^6 (MJ/kg feed)	10.79	10.79
Analysed fatty acid content (mg fatty acid/g feed)
C16:0	9.01	9.54
C18:0	3.31	3.43
C16:1	0.44	0.64
C18:1 (n-9c)	11.10	10.42
C18:2 (n-6c)	15.78	13.70
C18:3 (n-3)	0.82	0.88
C20:2 (n-6)	0.05	0.06
C20:3 (n-6)	0.02	0.03
C20:5 (n-3)	0.08	0.40
C22:5 (n-3)	0.04	0.12
C22:6 (n-3)	0.11	0.49
n-6:n-3	15.08	7.38

¹ Supplied per kg of lactation feed: vitamin A, 15,900 IU; vitamin D, 1590 IU; vitamin E, 90 mg; vitamin K, 2.1 mg; thiamine, 1.6 mg; riboflavin, 5.3 mg; niacin, 26.5 mg; pantothenic acid, 18.6 mg; pyridoxine, 3.7 mg; folic acid, 0.8 mg; vitamin B12, 0.03 mg; choline, 477 mg; I, 1.6 mg; Se, 0.42 mg; Zn, 127.2 mg, Fe 95.4 mg, Mn 53 mg and Cu 21.2 mg.

² Agila (Denmark).

³ 6.3 g/kg of fish oil (FO) or sunflower oil (SO) and 3.7 g/kg silicon dioxide (Producer: ADEXGO Kft., Hungary).

⁴ SID Lys = Standardized ileal digestible lysine, SID Met = Standardized ileal digestible methionine, SID Met + Cys = standardized ileal digestible methionine + cysteine, SID Thr = standardized ileal digestible threonine, SID Trp = standardized ileal digestible tryptophan, SID Val = standardized ileal digestible valine.

⁵ Metabolisable Energy for Swine.

⁶ Net Energy for Swine.

Composition and nutrient values of diets were provided by the feed manufacturer (farm).

Fatty acid composition was analyzed as detailed in section 2.4.

Table 2. Fatty acid composition of the control and the experimental sows’ milk.

Analysed fatty acid content (mg/mL of milk)	Control	Experimental	p-value
C12:0	0.29 ^c ± 0.05	0.24 ^d ± 0.06	0.07
C14:0	3.42 ± 0.48	3.19 ± 0.59	0.30
C16:0	27.52 ± 3.24	25.52 ± 3.43	0.15
C18:0	3.70 ± 0.87	3.83 ± 0.86	0.71
ΣSFAs	35.50 ± 4.43	33.22 ± 4.29	0.23
C16:1	6.21 ± 1.26	5.62 ± 1.62	0.33
C18:1 (n-9c)	20.52 ± 5.47	19.84 ± 5.97	0.77
ΣMUFAs	27.29 ± 6.27	26.03 ± 6.61	0.67
C18:2 (n-6c)	8.43 ^a ± 1.05	6.63 ^b ± 1.05	0.001
C18:3 (n-3)	0.36 ± 0.05	0.36 ± 0.05	0.97
C20:2 (n-6)	0.16 ± 0.04	0.15 ± 0.05	0.64
C20:3 (n-6)	0.09 ± 0.02	0.08 ± 0.02	0.67
C20:5 (n-3)	0.04 ^b ± 0.01	0.17 ^a ± 0.03	0.001
C22:5 (n-3)	0.17 ^b ± 0.03	0.28 ^a ± 0.06	0.001
C22:6 (n-3)	0.09 ^b ± 0.02	0.33 ^a ± 0.06	0.001
ΣPUFAs	9.92 ^a ± 1.26	8.61 ^b ± 1.30	0.02
Total fatty acid (mg/mL of milk)	72.71 ± 10.82	67.95 ± 10.26	0.59
Σn6	9.24 ^a	7.44 ^b	0.001
Σn3	0.69 ^b	1.17 ^a	0.001
n6/n3	13.42	6.35	–

SFAs, saturated fatty acids; MUFAs, monounsaturated fatty acids; PUFAs, polyunsaturated fatty acids ^a,b Different superscripts in the same row indicate a significant difference at min. p < 0.05. ^c,d Different superscripts in the same row indicate a tendency difference at the level of 0.05 < p < 0.1. Data without superscripts indicate that no statistical difference was found between the treatments.

Table 3. The chemical composition of the control and the experimental milk samples.

	Control	Experimental	p-value
Dry matter ^1 (% w/w)	18.91 ± 1.01	18.47 ± 1.78	0.57
Milk protein ^1 (% w/w)	5.06 ± 0.18	5.15 ± 0.37	0.12
Milk fat ^1 (% w/w)	7.84 ± 0.82	7.49 ± 1.25	0.37
Days of lactation	13.92 ± 2.91	12.50 ± 1.57	0.16

¹ Before milking, sows were injected IM with 10 IU oxytocin.

Figure 1. PCA score plot of milk samples based on the odour profiles described by all sensors, indicating the four groups of samples (CON1: control, 1st sampling, green diamond; CON2: control, 2nd sampling, pink star; EXP1: experimental, 1st sampling, blue square; EXP2: experimental, 2nd sampling, red triangle).

Figure 2. LDA results for the discrimination of the control (CON, blue square) and experimental (EXP, red triangle) milk samples based on the odour profiles described by all sensors.

Figure 3. Spider plot of the electronic nose (EN) data of the control (blue) and experimental (red) milk samples on the plane defined by the five selected sensors, indicating the names of the sensors (retention index and column type) on the angle, and intensity values (area under the chromatogram peak at the respective retention index) along the radius.

Figure 4. Bi-plots showing the loading vectors and the score plots of milk samples (CON1: control, 1st sampling, blue square; CON2: control, 2nd sampling, red triangle; EXP1: experimental, 1st sampling, green diamond; EXP2: experimental, 2nd sampling, pink star) in the plane of (a) PC1-PC2 and (b) PC2-PC3 when the PCA was performed with data from five selected sensors.

Figure 5. Bi-plot showing the LDA results for the discrimination of the control (CON, blue square) and experimental (EXP, red triangle) milk samples based on the odour profiles described by five selected sensors, and the loading vectors representing the dominance of the sensors.

Table 4. Assignment of the retention indices corresponding to the five selected sensors.

Retention index	GC column type ^+	Relative dominance ^++	Assigned chemical ^+++	Associated attribute
666	1-A	100%	3-Methyl butanol	Choking alcohol odour ^1 Saccharomyces cerevisiae metabolite ^1 Off-flavor in bovine milk ^2
463	2-A	25.7%	Acetaldehyde	Suffocating smell ^1 The smell of various plants ^1 Saccharomyces cerevisiae metabolite ^1 Escherichia coli metabolite ^1 Mouse metabolite ^1 Rancid odour in bovine milk ^2
510	2-A	97.1%	Lactic acid	Nearly odourless, weak unpleasant odour ^1 Intermediate in bacterial fermentation of sugar ^1
566	2-A	71.4%	Dimethyl sulphide	Disagreeable odour ^1 Algal metabolite ^1 produced naturally by some marine algae ^1
1117	2-A	78.6%	Acetyl pyrazine	Aromatic ketone ^1 The smell of seeds, nuts, meats, popcorn, bread crust, vinegar, potato snack ^1

⁺ 1-A: MXT-5; 2-A: MXT-1701. ⁺⁺ The dominance of each selected sensor in proportion to the most dominant one (100%) along with the 1st discrimination factor clearly discriminating the milk samples of the experimental (FO) and control (SO) groups during the LDA. ⁺⁺⁺ Based on the AroChemBase v7 database of AlphaSoft v16. ¹ PubChem Database (2020). ² Kang et al. (2014).

Figure 6. The chromatograms of sunflower oil (a,c) and fish oil (b,d) recorded using GC columns MXT-5 (a,b) and MXT-1701 (c,d), with the indications (red circles) of peaks specific for fish oil appearing in EXP milk samples (retention index 666 on column 1-A, 566 and 1117 on column 2-A, refer to Table 4 for assignment).

PubChem [Database]. 2020. [cited 25 Oct 2020]. Available from: https://pubchemdocs.ncbi.nlm.nih.gov/. Natl Cent Biotechnol Inf, US. Bethesda, MD: National Library of Medicine.

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Kang NK, Jun TS, Yang YS, Kim YS. 2014. Analysis of volatile flavor compounds in milk using electronic nose system. J Sens Sci Technol. 23:320–325. doi:10.5369/JSST.2014.23.5.320.

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Data availability statement

The data presented in this study are available upon request from the corresponding author.