Protein profile of cow milk from multibreed herds and its relationship with milk coagulation properties

Figures & data

Table 1. Number (frequency between brackets) of herds and cows involved in the study, and number of records (frequency between brackets) within herd and breeds.

Item^a	Number (frequency, %)	Number of records (frequency, %)
Herds
BS + HF	148 (30.27)	57,358 (32.99)
HF + SI	113 (23.11)	40,388 (23.23)
BS + SI	84 (17.18)	23,247 (13.37)
BS + HF + SI	68 (13.91)	28,794 (16.56)
SI + AG	28 (5.73)	10,513 (6.05)
HF + AG	22 (4.50)	5470 (3.15)
HF + SI + AG	11 (2.25)	3968 (2.28)
BS + AG	8 (1.64)	2501 (1.44)
BS + HF + AG + SI	4 (0.82)	711 (0.41)
BS + HF + AG	3 (0.61)	883 (0.51)
Overall	489 (100.00)	173,841 (100.00)
Cows
BS	4483 (35.77%)	64,429 (37.14%)
HF	4013 (32.02%)	52,127 (30.05%)
SI	3319 (26.48%)	46,387 (26.74%)
AG	718 (5.73%)	10,898 (6.28%)
Overall	12,533 (100.00%)	173,481 (100.00%)

^aBS: Brown Swiss; HF: Holstein-Friesian; SI: Simmental; AG: Alpine Grey.

Table 2. Number of test day records, mean, standard deviation (SD), range and coefficient of variation (CV) for milk yield, composition, somatic cell score, urea, detailed protein composition and coagulation properties.

Trait	No of records	Mean	SD	Range	CV, %
Milk yield, kg/d	173,841	26.51	7.45	51.20	28.10
Milk composition, %
Fat	171,742	4.14	0.68	4.68	16.46
Crude protein	173,484	3.50	0.38	2.48	10.94
Casein	173,397	2.75	0.31	2.01	11.24
Somatic cell score, units	173,841	2.40	1.87	9.59	78.06
Milk urea, mg/dL	173,841	21.36	7.07	44.9	33.09
Protein fractions, g/100 mL
α-Casein	173,678	1.54	0.19	2.40	12.50
β-Casein	169,187	1.04	0.18	1.57	16.79
κ-Casein	169,188	0.58	0.13	1.03	21.78
β-Lactoglobulin	170,557	0.30	0.11	1.07	36.61
α-Lactalbumin	173,803	0.08	0.01	0.11	8.01
Protein fractions, % of crude protein
α-Casein	172,911	43.91	2.81	19.20	6.39
β-Casein	168,652	29.84	3.93	26.66	13.19
κ-Casein	168,707	16.57	3.35	20.64	20.18
β-Lactoglobulin	169,977	8.52	2.97	17.40	34.90
α-Lactalbumin	173,187	2.18	0.26	1.77	12.01
Milk coagulation properties^a
RCT, min	159,206	21.64	3.86	19.62	17.83
k20, min	168,563	5.71	1.29	8.05	22.55
a30, mm	127,123	16.75	9.97	48.96	59.48
IAC	125,814	100.58	4.50	24.41	4.48

^aRCT: rennet coagulation time; k₂₀: curd-firming time; a₃₀: curd firmness 30 min after rennet addition. IAC: index of milk aptitude to coagulate

Table 3. F-values of fixed effects of breed (B), month of sampling (M), parity order (P), stage of lactation (S) and their first-order interactions and percentage of total variance explained by random effects of herd, cow nested within breed and residual for milk yield, composition, somatic cell score, urea, detailed protein composition and coagulation properties.

	Fixed effects								Random effects
Trait	B	M	P	S	B × M	B × S	B × P	S × P	σ^2herd, %	σ^2cow (breed), %	σ^2residual, %
Milk yield, kg/d	1078.04	269.55	3456.84	3600.22	5.78	10.48	21.00	81.10	34.79	24.42	40.78
Milk composition, %
Fat	188.71	316.65	55.93	451.25	4.78	8.97	14.00	5.51	12.46	25.97	61.57
Crude protein	1107.83	958.20	396.88	5147.91	8.51	32.98	9.72	10.70	13.37	43.07	43.56
Casein	1079.55	962.77	465.25	4822.38	7.09	31.41	14.06	11.87	13.48	44.22	42.30
Somatic cell score, units	38.19	7.64	433.46	254.79	2.34	3.37	10.36	3.96	6.68	19.72	73.60
Milk urea, mg/dL	349.60	41.97	76.93	105.65	10.58	4.07	2.56	3.88	22.63	14.80	62.56
Protein fractions, g/100 mL
α-Casein	817.82	1447.12	462.33	1784.73	9.62	15.19	15.31	4.83	15.51	35.24	49.25
β-Casein	372.77	171.97	719.31	2577.06	11.70	8.74	4.34	6.15	12.72	44.59	42.69
κ-Casein	636.01	316.92	2373.15	195.22	11.53	3.26	8.57	2.47	7.45	39.55	53.00
β-Lactoglobulin	155.13	796.64	193.68	544.63	4.76	12.35	5.04	4.82	5.45	35.99	58.56
α-Lactalbumin	193.71	268.27	52.53	104.87	2.76	9.53	15.23	3.29	11.19	33.30	55.50
Protein fractions, % of crude protein
α-Casein	122.73	778.81	382.37	580.35	5.91	8.47	11.20	2.59	12.17	22.43	65.40
β-Casein	140.34	125.45	960.77	639.77	11.49	4.60	3.09	3.99	10.96	43.73	45.31
κ-Casein	219.83	709.81	2156.74	108.32	11.73	1.65	5.79	2.53	8.43	37.12	54.46
β-Lactoglobulin	452.70	582.23	262.84	205.62	6.24	10.36	7.68	3.98	5.51	35.13	59.36
α-Lactalbumin	1327.26	275.62	241.77	3135.61	7.57	24.43	12.61	5.62	8.64	42.39	48.97
Milk coagulation properties^a
RCT, min	5.03	67.93	176.08	325.09	9.03	5.75	20.17	3.31	7.66	28.98	63.37
k20, min	138.61	94.36	86.54	138.1	2.17	3.11	14.47	2.72	5.78	24.59	69.62
a30, mm	979.99	168.45	564.51	717.95	4.73	9.25	6.35	2.45	8.10	38.94	52.95
IAC	15.79	59.52	156.01	164.13	2.87	4.11	16.42	3.09	5.31	28.51	66.18

^aRCT: rennet coagulation time; k₂₀: curd-firming time; a₃₀: curd firmness 30 min after rennet addition. IAC: index of milk aptitude to coagulate.

All fixed effects were highly significant (p<.001).

Table 4. Least squares means (standard error) of milk yield, composition, somatic cell score, urea, detailed protein composition and coagulation properties.

Trait	Brown Swiss	Holstein-Friesian	Alpine Grey	Simmental
Milk yield, kg/d	25.16 (0.17)^c	29.37 (0.17)^a	20.79 (0.25)^d	25.67 (0.17)^b
Milk composition, %
Fat	4.27 (0.013)^a	4.04 (0.013)^c	3.86 (0.024)^d	4.12 (0.014)^b
Crude protein	3.62 (0.006)^a	3.30 (0.006)^c	3.53 (0.012)^b	3.51 (0.007)^b
Casein	2.84 (0.005)^a	2.58 (0.005)^c	2.76 (0.01)^b	2.75 (0.005)^b
Somatic cell score, units	2.50 (0.029)^ab	2.47 (0.029)^b	2.52 (0.057)^a	2.19 (0.031)^c
Milk urea, mg/dL	23.33 (0.168)^a	20.15 (0.168)^d	21.87 (0.252)^b	21.09 (0.172)^c
Protein fractions, g/100 mL
α-Casein	1.58 (0.004)^a	1.44 (0.004)^d	1.54 (0.007)^c	1.56 (0.004)^b
β-Casein	1.12 (0.003)^a	1.02 (0.003)^d	1.08 (0.007)^b	1.03 (0.004)^c
κ-Casein	0.60 (0.002)^a	0.47 (0.002)^d	0.58 (0.005)^b	0.54 (0.003)^c
β-Lactoglobulin	0.29 (0.002)^b	0.32 (0.002)^a	0.29 (0.004)^b	0.33 (0.002)^a
α-Lactalbumin	0.074 (0.0001)^c	0.076 (0.0001)^b	0.077 (0.0002)^a	0.077 (0.0001)^a
Protein fractions, % of crude protein
α-Casein	43.67 (0.051)^b	43.59 (0.051)^b	43.62 (0.093)^b	44.45 (0.054)^a
β-Casein	31.05 (0.081)^a	30.93 (0.081)^ab	30.62 (0.163)^b	29.33 (0.087)^c
κ-Casein	16.63 (0.066)^a	15.05 (0.067)^c	16.68 (0.135)^a	15.37 (0.071)^b
β-Lactoglobulin	7.91 (0.047)^c	9.74 (0.048)^a	8.08 (0.102)^c	9.23 (0.052)^b
α-Lactalbumin	2.07 (0.004)^b	2.33 (0.004)^c	2.21 (0.008)^a	2.22 (0.004)^a
Milk coagulation properties^A
RCT, min	21.50 (0.068)^b	21.52 (0.069)^b	21.82 (0.138)^a	21.32 (0.073)^c
k20, min	5.28 (0.022)^d	6.49 (0.022)^a	5.56 (0.046)^c	5.86 (0.024)^b
a30, mm	17.76 (0.162)^a	14.15 (0.17)^c	16.27 (0.337)^b	16.41 (0.179)^b
IAC	100.93 (0.074)^a	100.49 (0.078)^b	100.32 (0.157)^b	100.97 (0.082)^a

^ARCT: rennet coagulation time; k₂₀: curd-firming time; a₃₀: curd firmness 30 min after rennet addition. IAC: index of milk aptitude to coagulate.

Least squares mean with different superscript letters within a row are significantly different (p<.01).

Figure 1. Least squares mean of (A) α-casein (α-CN), (B) β-casein (β-CN), (C) κ-casein (κ-CN), (D) β-lactoglobulin (β-LG) and (E) α-lactalbumin (α-LA) across stage of lactation for Brown Swiss (

), Holstein-Friesian (

), Alpine Grey (

), and Simmental (

) cows, expressed as g/100 mL of milk (left side) or percentage of crude protein (right side) of the figure.

Figure 2. Least squares mean of (A) α-casein (α-CN), (B) β-casein (β-CN), (C) κ-casein (κ-CN), (D) β-lactoglobulin (β-LG) and (E) α-lactalbumin (α-LA) across parity class for Brown Swiss (

), Holstein-Friesian (

), Alpine Grey (

), and Simmental (

) cows, expressed as g/100 mL of milk (left side) or percentage of crude protein (right side) of the figure.

Table 5. Pearson correlation coefficients for protein fractions (measured as % of crude protein) and milk coagulation properties.

Trait	α-Casein	β-Casein	κ-Casein	β-Lactoglobulin	α-Lactalbumin	RCT	k20	a30	IAC
Protein fractions
α-Casein	–	−0.49	−0.22	0.19	0.33	0.06	0.13	0.01	0.01
β-Casein	−0.52	–	0.04	−0.32	−0.15	0.17	0.10	−0.18	−0.14
κ-Casein	−0.32	0.18	–	−0.56	−0.46	0.21	−0.12	−0.10	−0.24
β-Lactoglobulin	0.21	−0.33	−0.61	–	0.48	−0.22	−0.22	0.22	0.23
α-Lactalbumin	0.24	−0.05	−0.34	0.28	–	0.06	0.11	−0.01	0.00
Milk coagulation properties^a
RCT	0.05	0.19	0.27	−0.38	−0.03	–	0.39	−0.74	−0.93
k20	0.12	0.20	−0.05	−0.26	0.39	0.53	–	−0.54	−0.44
a30	0.07	−0.22	−0.16	0.30	−0.04	−0.77	−0.49	–	0.94
IAC	0.08	−0.20	−0.25	0.32	0.03	−0.90	−0.47	0.96	–

Above the diagonal, Pearson correlation coefficients calculated from raw data; under the diagonal, Pearson correlation coefficients calculated from studentised residuals estimated by the model.

^aRCT: rennet coagulation time (min); k₂₀: curd-firming time (min); a₃₀: curd firmness 30 min after rennet addition (mm).

IAC: index of milk aptitude to coagulate

All correlations differed from zero (p<.001).

Table 6. Results from Lagrange constrained optimisation of protein relative concentration for milk coagulation properties and index of milk aptitude to coagulate.

Protein fractions, % of crude protein	Optimisation range	Optimising concentrations
		RCT^a	k20	a30	IAC
α-Casein	34.67–53.87	38.85	35.96	38.00	39.97
β-Casein	16.20–42.86	24.30	16.20	20.65	22.38
κ-Casein	7.03–27.67	16.68	27.67	21.34	17.91
β-Lactoglobulin	1.38–18.78	18.78	18.78	18.62	18.35
α-Lactalbumin	1.39–3.16	1.39	1.39	1.39	1.39

^aRCT: rennet coagulation time (min); k₂₀: curd-firming time (min); a₃₀: curd firmness 30 min after rennet addition (mm).

IAC: index of milk aptitude to coagulate.

Data availability statement

None of the data were deposited in an official repository. The data that support the findings presented in this study are available from the first author or corresponding author upon reasonable request.