A principal component analysis required in technical assistance guidance for chilled raw milk producers

The purpose of the present study was to evaluate the principal component analysis (PCA) to guide technical assistance regarding several dairy farms’ issues, which includes improving microbiological quality and physical-chemical composition of raw refrigerated milk. Data of monthly analysis of fat, protein, lactose, dry defatted stratum, somatic cell count, total bacterial count, milk temperature of 8,101 samples of milk from expansion tanks and production of 78 farms located in the northern region of Minas Gerais, Brazil were processed. Descriptive statistical measures and Pearson correlation coefficient were estimated involving all evaluated traits during the dry and rainy seasons. In addition, multivariate analyses were performed using PCA. The results showed that two farm sites were negatively related to milk quality in both seasons. One farm stood out positively, being able to be used as a herd management model to drive technical assistance actions. Thus, PCA is efficient in simplifying large amounts of data, allowing simpler and faster technical herd management interpretation.

Keywords:
dairy cattle; milk quality; multivariate analyses; PCA

Authorship

Dyhogo Henrique Veloso Leal

Instituto de Ciências Agrárias, Universidade Federal de Minas Gerais, Av. Universitária, 1000, 39404-547, Montes Claros, Minas Gerais, Brazil. Universidade Federal de Minas GeraisBrazilMontes Claros, Minas Gerais, BrazilInstituto de Ciências Agrárias, Universidade Federal de Minas Gerais, Av. Universitária, 1000, 39404-547, Montes Claros, Minas Gerais, Brazil.

Alcinei Mistico Azevedo ^** Author for correspondence. E-mail: alcineimistico@hotmail.com

http://orcid.org/0000-0001-5196-0851

Anna Christina de Almeida

Otaviano de Souza Pires Neto

Eduardo Robson Duarte

Fernanda Santos Silva Raidan

The Commonwealth Scientific and Industrial Research Organisation, Horbart, Tasmania, Austália. The Commonwealth Scientific and Industrial Research OrganisationAustraliaHorbart, Tasmania, AustraliaThe Commonwealth Scientific and Industrial Research Organisation, Horbart, Tasmania, Austália.

* Author for correspondence. E-mail: alcineimistico@hotmail.com

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (6)
Tables (4)

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Figure 1
Scatter plot of 78 farms in relation to the top 1 and 2 principal components in rainy season.

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Figure 2
Scatter plot of 78 farms in relation to the top 1 and 3 principal components in rainy season.

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Figure 3
Scatter plot of 78 farms in relation to the top 2 and 3 principal components in rainy season.

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Figure 4
Scatter plot of 78 farms in relation to the top 1 and 2 principal components in dry season.

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Figure 5
Scatter plot of 78 farms in relation to the top 1 and 3 principal components in dry season.

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Figure 6
Scatter plot of 78 farms in relation to the top 2 and 3 principal components in dry season.

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Table 1
Descriptive analyses for milk composition¹, somatic cells count (CCS), total bacteria count (TBC) e milk yield (MY) and raw milk storage temperature (TEMP) in rainy and dry season in the North of Minas Gerais from 2014 to 2017.

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Table 2
Pearson correlation between quality and production traits of raw milk collected in dry (above diagonal) and rainy season (bellow diagonal) in the North of Minas Gerais.

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Table 3
Eigenvalue (EGV), individual (PEI%) and cumulative explained variance (PEA%, in percentage) for every principal component obtained from milk microbiological and chemical composition trait that determine the milk quality for dry and rainy season in the North of Minas Gerais.

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Table 4
Correlation between principal components and milk quality traits collected in rainy and dry seasons in the North of Minas Gerais.

Figure 1 Scatter plot of 78 farms in relation to the top 1 and 2 principal components in rainy season.

Figure 2 Scatter plot of 78 farms in relation to the top 1 and 3 principal components in rainy season.

Figure 3 Scatter plot of 78 farms in relation to the top 2 and 3 principal components in rainy season.

Figure 4 Scatter plot of 78 farms in relation to the top 1 and 2 principal components in dry season.

Figure 5 Scatter plot of 78 farms in relation to the top 1 and 3 principal components in dry season.

Figure 6 Scatter plot of 78 farms in relation to the top 2 and 3 principal components in dry season.

Table 1 Descriptive analyses for milk composition¹, somatic cells count (CCS), total bacteria count (TBC) e milk yield (MY) and raw milk storage temperature (TEMP) in rainy and dry season in the North of Minas Gerais from 2014 to 2017.

Traits¹	Parameters²
Traits¹	Maximum	Minimum	Mean	SE	CV (%)	CI 95%
Dry season
MY (L prod^-1coleta^-1)	2993.36	49.75	711.83	89.67	111.25	533.27 - 890.38
DDE (g 100^-1 g)	9.26	8.37	8.77	0.02	2.23	8.73 - 8.82
LC (g 100^-1 g)	4.69	4.19	4.47	0.01	2.63	4.45 - 4.50
FC (g 100^-1 g)	4.35	2.71	3.88	0.03	6.81	3.82 - 3.94
PROT (g 100^-1 g)	3.67	3.05	3.31	0.01	3.77	3.28 - 3.34
TBC (1000 UFC mL^-1)	1194.22	8.87	266.50	34.02	112.73	198.76 - 334.24
CCS (1000 CS mL^-1)	1819.50	173.64	491.70	33.79	60.68	424.43 - 558.98
Temp (ºC)	4.75	2.91	3.71	0.04	9.61	3.62 - 3.79
Rainy season
VOL (L prod^-1coleta^-1)	3010.84	36.91	718.42	85.91	104.93	547.32 - 889.52
DDE (g 100^-1 g)	9.15	8.29	8.77	0.02	2.05	8.73 - 8.81
LACT (g 100^-1 g)	4.69	4.25	4.52	0.01	2.41	4.45 - 4.54
FC (g 100^-1 g)	4.47	2.71	3.66	0.03	8.35	3.59 - 3.73
PROT (g 100^-1 g)	3.62	2.98	3.25	0.01	3.48	3.23 - 3.28
TBC (1000 UFC mL^-1)	2479.48	6.25	426.95	61.76	126.94	303.94 - 549.96
CCS (1000 CS mL^-1)	1870.17	219.29	521.04	36.66	61.75	448.02 - 594.06
Temp. (ºC)	5.00	2.99	3.78	0.05	10.91	3.69 - 3.88

¹Milk yield: MY; Defatted dry extract content: DDE. Lactose content: LC. Fat content: FC. Protein content: PROT; Total bacteria count: TBC; Somatic cells count:CCS. ²Standard error: SE. Coefficient of variation: CV. Confidence interval: CI.

Table 2 Pearson correlation between quality and production traits of raw milk collected in dry (above diagonal) and rainy season (bellow diagonal) in the North of Minas Gerais.

Traits¹	MY	CCS	DDE	LC	FC	PROT	TEMP	TBC
MY	-	0.0 ^ns	-0.26*	0.07 ^ns	-0.17 ^ns	-0.39**	-0.16 ^ns	-0.33**
CCS	0.09 ^ns	-	-0.43**	-0.43**	0.15 ^ns	-0.27*	0.09 ^ns	0.08 ^ns
DDE	-0.26*	-0.47**	-	0.75**	0.15 ^ns	0.86**	0.06 ^ns	0.19 ^ns
LC	-0.07 ^ns	-0.59**	0.79**	-	-0.02 ^ns	0.32**	-0.09 ^ns	0.02 ^ns
FC	0.13 ^ns	0.32**	0.01 ^ns	-0.19 ^ns	-	0.17 ^ns	0.10 ^ns	0.14 ^ns
PROT	-0.36**	-0.23*	0.85**	0.35 **	0.15 ^ns	-	0.14 ^ns	0.24 *
TEMP	-0.03 ^ns	0.03 ^ns	0.2 ^ns	0.08 ^ns	0.2 ^ns	0.24*	-	-0.07 ^ns
TBC	-0.26 *	-0.08 ^ns	0.19 ^ns	0.17 ^ns	-0.12 ^ns	0.15 ^ns	-0.04 ^ns	-

¹MY = Milk yield; CCS = Somatic cells count; DDE = Defatted dry extract content; LC = Lactose content; FC = Fat content; PROT = Protein content; TEMP = Milk storage temperature; TBC = Total bacteria count. nsNot significant at level of 5% by t test. *Significant at level of 5%. **Significant at level of 1% by t test.

Table 3 Eigenvalue (EGV), individual (PEI%) and cumulative explained variance (PEA%, in percentage) for every principal component obtained from milk microbiological and chemical composition trait that determine the milk quality for dry and rainy season in the North of Minas Gerais.

PC	Dry season			Rainy season
PC	ATV	PEI%	PEA%	ATV	PEI%	PEA%
1	2.72	34.02	34.02	2.89	36.10	36.10
2	1.64	20.51	54.53	1.49	18.69	54.78
3	1.06	13.28	67.81	1.19	14.93	69.71
4	0.90	11.31	79.11	0.79	9.89	79.60
5	0.65	8.16	87.28	0.78	9.80	89.40
6	0.56	6.98	94.26	0.47	5.90	95.30
7	0.46	5.71	99.96	0.37	4.68	99.99
8	0.00	0.37	100.00	0.00	0.01	100.00

Table 4 Correlation between principal components and milk quality traits collected in rainy and dry seasons in the North of Minas Gerais.

Traits1	Rainy Season			Dry Season
Traits1	CP1	CP2	CP3	CP1	CP2	CP3
MY	-0.40	0.02	0.72	-0.40	0.63	-0.06
CCS	-0.64	-0.45	-0.33	-0.52	-0.53	0.03
DDE	0.95	-0.18	0.10	0.97	0.09	-0.05
LC	0.81	0.21	0.33	0.70	0.49	0.03
FC	-0.14	-0.79	0.09	0.18	-0.52	-0.06
PROT	0.77	-0.43	-0.14	0.86	-0.21	-0.09
TEMP	0.21	-0.60	0.14	0.08	-0.37	-0.83
TBC	0.32	0.19	-0.63	0.30	-0.51	0.60

¹MY = Milk yield; CCS = Somatic cells count; DDE = Defatted dry extract content; LC = Lactose content; FC = Fat content; PROT = Protein content; TEMP = Milk storage temperature; TBC = Total bacteria count.

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A principal component analysis required in technical assistance guidance for chilled raw milk producers

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[1] * Author for correspondence. E-mail: alcineimistico@hotmail.com