Genetic background of calcium and phosphorus phases predicted from milk mid-infrared spectra of Holstein cows

Figures & data

Table 1. Mean, range, and coefficient of variation (CV) of milk yield and quality traits, mineral fractions, and coagulation properties predicted by mid-infrared spectroscopy.

Trait^a	Mean	Range	CV, %
Milk yield, kg/d	29.71	47.00	25.35
Protein, kg/d	0.96	1.90	0.11
Fat, kg/d	1.16	3.16	9.72
Protein, %	3.31	2.27	10.55
Fat, %	4.02	4.73	17.15
SCS	2.56	13.27	73.82
Minerals
Ca
Total, mg/kg	1351.05	864.52	10.83
Micellar, mg/kg	963.42	871.56	14.25
Soluble, mg/kg	282.54	284.18	15.75
Micellar/soluble, w/w	3.44	4.98	23.01
P
Total, mg/kg	1032.35	774.78	13.37
Micellar, mg/kg	602.94	579.97	15.31
Soluble, mg/kg	365.19	313.66	13.57
Micellar/Soluble, w/w	1.55	2.72	27.55
Milk coagulation properties
RCT, min	22.20	18.31	16.42
k20, min	6.22	7.53	19.32
a30, mm	14.00	42.13	63.24

^aSCS: somatic cell score; RCT: rennet coagulation time; k₂₀: curd-firming time; a₃₀: curd firmness 30 min after enzyme addition to milk.

Figure 1. Effect of parity on micellar and soluble phases of Ca and P, and their ratio.

Figure 2. Effect of lactation stage on micellar and soluble phases of Ca and P, and their ratio.

Table 2. Additive genetic variance (σ²_a), permanent environmental variance (σ²_w), heritability (h²), and repeatability (t) of Ca and P phases from univariate analyses^a, and average, minimum and maximum heritability estimates from bivariate analyses.

Trait	Univariate analyses				Bivariate analyses
	σ^2a	σ^2w	h^2	t	Average	Minimum	Maximum
Ca
Micellar, mg/kg	55.637	10.316	0.520	0.616	0.519	0.518	0.521
Soluble, mg/kg	7.149	1.272	0.518	0.610	0.517	0.516	0.518
Micellar/soluble, w/w	0.238	0.044	0.548	0.650	0.541	0.541	0.553
P
Micellar, mg/kg	30.744	6.775	0.513	0.626	0.512	0.511	0.516
Soluble, mg/kg	8.115	1.634	0.533	0.640	0.532	0.531	0.534
Micellar/soluble, w/w	0.047	0.009	0.472	0.561	0.471	0.470	0.475

^aStandard errors of heritability and repeatability ranged from 0.013 to 0.014 and 0.004 to 0.005, respectively.

Table 3. Phenotypic (below diagonal) and genetic correlations^a (above diagonal) between Ca and P phases and their ratio.

Trait	Ca			P
	Micellar	Soluble	Micellar/Soluble	Micellar	Soluble	Micellar/Soluble
Ca
Micellar, mg/kg		–0.299	0.735	0.906	–0.317	0.897
Soluble, mg/kg	–0.256		–0.834	–0.530	–0.210	–0.240
Micellar/soluble, w/w	0.720	–0.809		0.871	–0.075	0.642
P
Micellar, mg/kg	0.896	–0.477	0.853		–0.086	0.760
Soluble, mg/kg	–0.396	–0.132	–0.160	–0.177		–0.643
Micellar/soluble, w/w	0.886	–0.243	0.643	0.768	–0.670

^aStandard errors ranged from 0.002 to 0.008 and 0.010 to 0.025 for phenotypic and genetic correlations, respectively.

Table 4. Phenotypic (r_p) and genetic (r_a) correlations^a of milk Ca and P phases (mg/kg) and their ratio (w/w) with yield and quality traits, and coagulation properties.

Trait^b		Ca			P
		Micellar	Soluble	Micellar/Soluble	Micellar	Soluble	Micellar/soluble
Milk yield, kg/d	rp	–0.256	0.088	–0.233	–0.270	0.059	–0.211
	ra	–0.406	0.277	–0.480	–0.524	0.013	–0.318
Protein, kg/d	rp	0.041	–0.099	0.074	0.089	0.036	0.026
	ra	0.284	0.022	0.098	0.262	–0.020	0.198
Fat, kg/d	rp	0.053	0.053	0.039	0.045	–0.042	–0.10
	ra	0.444	–0.124	0.354	0.407	–0.198	0.370
Protein, %	rp	0.647	–0.417	0.665	0.783	–0.066	0.519
	ra	0.658	–0.449	0.694	0.808	–0.002	0.520
Fat, %	rp	0.399	–0.038	0.332	0.402	–0.1364	0.261
	ra	0.649	–0.358	0.654	0.700	–0.163	0.551
SCS	rp	–0.018	–0.004	–0.023	–0.039	0.064	–0.049
	ra	–0.098	–0.042	–0.046	–0.106	0.113	–0.132
RCT, min	rp	–0.134	–0.030	–0.091	–0.171	0.241	–0.243
	ra	–0.201	–0.020	–0.117	–0.207	0.236	–0.326
k20, min	rp	–0.509	0.221	–0.466	–0.650	0.109	–0.413
	ra	–0.576	0.295	–0.535	–0.732	0.083	–0.524
a30, mm	rp	0.314	–0.108	0.288	0.406	–0.186	0.375
	ra	0.376	–0.134	0.317	0.441	–0.159	0.422

^aStandard errors ranged from 0.003 to 0.008 and 0.009 to 0.044 for phenotypic and genetic correlations, respectively.

^bSCS: somatic cell score; RCT: rennet coagulation time; k₂₀: curd-firming time; a₃₀: curd firmness 30 min after enzyme addition to milk.