Phenotypic analysis of milk composition, milk urea nitrogen and somatic cell score of Italian Jersey cattle breed

Figures & data

Table 1. Descriptive statistics of milk yield, composition traits, MUN and SCS of Italian Jersey cows.

Trait	No of records	Mean	SD	Minimum	Maximum
Milk yield, kg/d	416,846	20.11	6.61	2.00	46.50
Fat, %	415,849	5.18	1.13	0.50	9.86
Protein, %	416,547	4.08	0.49	2.04	6.11
Casein, %	198,713	3.16	0.39	1.04	5.26
Lactose, %	324,233	4.77	0.23	3.68	5.69
MUN, mg/dL	188,294	23.51	8.00	0.09	55.80
SCS, units	415,794	3.35	1.85	−3.64	10.84

MUN: milk urea nitrogen; SCS: somatic cell score.

Table 2. F-values and significance of fixed effects, and proportion of total variance accounted by herd-test-day (σ²_HTD, %) and cow (σ²_cow, %) effects for milk yield, composition traits, MUN and SCS (n = 13,476).

Trait	Fixed effects						Random effects		RSD
	DIM	P	Calving season	Milking frequency	Recording type	DIM × P	σ^2HTD, %	σ^2cow, %
Milk yield, kg/d	337.55***	19.41***	5.64***	39.24***	134.77***	7.64***	10.94	33.26	4.57
Fat, %	37.01***	4.12***	6.32***	26.32***	1.01	1.56***	18.27	14.73	0.88
Protein, %	166.38***	7.52***	4.29***	50.61***	3.42	1.64**	11.31	21.51	0.36
Casein, %	106.43***	4.94***	4.82***	23.28***	0.08	1.89***	9.77	18.46	0.31
Lactose, %	59.42***	47.86***	0.90	3.69	5.26*	3.05***	11.92	17.84	0.19
MUN, mg/dL	4.63***	4.32***	5.78***	21.97***	4.06*	1.41*	53.09	6.28	4.95
SCS, units	11.13***	33.05***	2.00	34.91***	0.20	2.26***	5.99	22.36	1.49

DIM: days in milk; P: parity; RSD: residual standard deviation; MUN: milk urea nitrogen; SCS: somatic cell score.

* p < .05, **p < .01, ***p < .001.

Table 3. Pearson correlations coefficients between milk yield, composition traits, MUN and SCS (n = 13,476).

Trait	Fat	Protein	Casein	Lactose	MUN	SCS
Milk yield	−0.25	−0.26	−0.24	0.23	0.07	−0.20
Fat		0.50	0.52	−0.31	−0.09	0.10
Protein			0.98	−0.35	−0.02	0.11
Casein				−0.32	−0.03	0.09
Lactose					0.06	−0.39
MUN						−0.11

MUN: milk urea nitrogen; SCS: somatic cell score.

p < .001 for all correlations.