Monitoring of the declining trend of Polychlorobifenyls concentration in milk of contaminated dairy cows

Figures & data

Table 1 Chemical composition and nutritional traits of the diets.

Feeds	Dry period (kg/day)	Lactating period (kg/day)
Corn silage	6.0	22.0
Alfalfa hay	-	3.5
Grass hay	9.0	1.0
Concentrate	1.6^*	12.0^°
Mix corn (70%) and barley (30%)	-	1.5
Straw	1.0	-
Dry matter intake, kg/d	9.49	19.9
Moisture, %	45.42	46.22
Crude protein, % DM	12.77	16.50
Crude fibre, % DM	28.39	30.82
Fats, % DM	2.21	2.36
Starch, % DM	10.95	16.56

* Mineral-vitamin supplementation (kg as fed): Vit. A U 25,000; Vit. D₃ U 1000; Vit. E mg 40; Cu mg 15; Zn mg 100; Mn mg 23; I mg 1.50; Se mg 0.34; Co mg 0.30.

° Mineral-vitamin supplementation (kg as fed): Vit. A U 25,000; Vit D₃ U 1500; Vit. E mg 40; Cu mg 20; Zn mg 110; Mn mg 23; I mg 1.80; Se mg 0.34; Co mg 0.38.

Table 2 PCBs precursor and monitoring ion in MS-MS.

PCBs sorted in order of retention time	Precursor ion	Monitoring ions
PCB 18	258	186, 220
PCB 28, 31	258	186, 220
PCB 52	292	222, 258
PCB 44	292	222, 256
PCB 101	326	256, 291
PCB 149	326	254, 290
PCB 118	360	290, 325
PCB 153	360	290, 325
PCB 138	360	290, 325
PCB 180	394	324, 360
PCB 194	430	360, 395

Table 3 Initial PCB content and time required in order that PCB content become lower than maximum acceptable level.

	Cow 1	Cow 2	Cow 3	Cow 4	Cow 5	Cow 6
	214	228	235	242	240	233
Initial PCB content of milk, ng/g fat	1388	1142	709	958	596	490
Days to drop under 100, ng/g fat	167	165	209	144	not reach	189
Average milk yield, kg/d	29.3	28.9	24.5	23.2	22.5	26.0

Table 4 PCB concentration (ng/g wet weight) in blood, milk and several tissues at the end of the experiment.

	Cow 1	Cow 2	Cow 3	Cow 4	Cow 5	Cow 6
	214	228	235	242	240	233
Body fat	90.5	194.3	460.7	224.4	241.3	150.4
Tail fat	98.3	134.0	375.0	206.7	177.8	155.8
Liver	0.4	0.9	0.8	1.1	1.2	0.9
Kidney	2.3	5.5	10.2	6.0	8.7	7.9
Blood	0.5	0.6	1.0	0.5	0.7	0.6
Milk	1.1	1.5	1.6	1.3	1.9	1.6

Table 5 Variations of PCB congeners percentage in milk (on sum of PCB) during the trial.

PCB congeners
	28	52	101	118	138	153	180
First week	0.61^A^a	0.15^a	14.55^B^c	34.91^B^c	26.99^A^B^a	18.75	4.04^b
First month	1.35^A^b^a^b	0.31^a^b	14.13^B^b^c	35.64^B^c	26.55^A^a	18.67	3.34^a^b
Second month	3.02^B^C^b^c	0.75^a^b^c	12.79^A^B^b	30.61^A^B^b	32.63^B^C^b	19.63	0.57^a
Third month	4.26^C^D^c^d	1.22^b^c	12.01^A^a	25.54^A^a^b	34.23^C^b^c	22.22	0.53^a
End trial	5.59^D^d	1.32^c	11.12^A^a	23.07^A^a	37.67^C^c	21.22	nd^*
SE	0.592	0.326	0.477	1.424	1.504	1.648	1.053

* Under the detection level. Means in the same column with different upper letter significantly differ.

SE = standard error of the means.

a,b,c,d P<0.05

A,B,C,D P<0.01.

Table 6 Congener profiles of blood, milk and tissue (percentage of PCB’s sum).

PCB congeners
	28	52	101	118	138	153	180	SE congeners
Body fat	^A 0.99^A^a	^A^a 0.24^A^a	^A^B^b 8.98^B^c	^A^a 24.08^C^d	^B^b 31.44^E^f	^A^B^a 27.73^D^e	^b 6.53^B^b	0.648
Tail fat	^A 1.04^A^a	^A^a 0.25^A^a	^A^B^b 8.67^B^b	^A^a 22.08^C^c	^B^C^b 31.80^D^d	^B^b 29.27^D^d	^b 6.88^B^b	1.099
Liver	^A 0.48^A^a	^A^a 0.12^A^a	^A^B^b 8.91^B^b	^A^a 20.35^C^c	^D^c 38.90^E^e	^B^b 28.72^D^d	^a^b 3.17^A^B^a	1.969
Kidney	^A 0.31^A^a	^A^a 0.07^A^a	^B^b 9.96^B^b	^A^B^a 24.61^C^c	^B^C^a 31.93^D^d	^B^b 31.12^D^d	^a 2.00^A^a	0.980
Blood	^A 0.67^A^a	^A^B^a 0.33^A^a	^A^a 4.44^A^a	^B^b 34.92^B^c	^A^a 24.76^B^b	^B^b 32.54^B^b^c	^a 1.23^A^a	3.205
Milk	^B 5.59^A^B^a	^B^b 1.32^A^a	^B^b 11.12^B^b	^A^a 23.07^C^c	^C^D^c 37.68^D^d	^A^a 21.22^C^c	udl	1.575
SEtissue	0.619	0.252	1.343	2.624	1.544	1.741	1.284

Means in the same row, with different right upper letter significantly differ. Means in the same column with different left upper letter significantly differ.

SE = standard error of the means.

a,b,c,d,e,f P<0.05;

A,B,C,D,E P<0.01.

udl= Under the detection level.