Today, bulk tank goat milk samples for payment are analyzed using mid-infrared (MIR) spectroscopy based on cow milk calibrations in Québec, Canada. The aim of the study was to compare milk fat, protein, SCC, and urea nitrogen (MUN) concentrations of goat milk analyzed by reference methods and MIR using cow milk calibrations. Bulk tank milk samples were obtained from 20 goat herds 5 times between March 2016 and February 2017. Samples were analyzed by MIR based on cow milk calibrations to obtain milk fat, protein, SCC, and MUN concentrations. Gravimetric method, determination of nitrogen content with Kjeldahl method, microscopy, and continuous flow analyses were considered as reference methods for fat, protein, SCC, and MUN concentrations, respectively. Proc MIXED of SAS with repeated measures in sampling time was used to compare MIR and reference methods. No significant difference was noted for milk fat and SCC concentrations between the 2 methods (Table 1). However, MIR underestimated milk protein concentration by 0.16 percentage point compared with the reference method (P = 0.02). In opposition, MIR overestimated MUN concentration compared with the reference method (P < 0.0001). As dairy goat producers in Québec, Canada are paid based on the milk components they sell and protein is the most profitable component, specific calibrations for goat milk should be developed or an adjustment should be proposed. In summary, MIR based on cow milk calibrations should be avoided to estimate protein and MUN concentrations of goat milk. Table 1. Comparison of milk component concentrations between mid-infrared (MIR) spectroscopy based on cow milk calibrations and reference method

Milk components	Mean	SD	Minimum	Maximum	P-value
Fat, %					0.69
MIR	3.72	0.43	2.76	5.38
Reference	3.77	0.46	2.84	5.62
Protein, %					0.02
MIR	3.33	0.28	2.80	4.72
Reference	3.49	0.30	2.96	5.04
MUN, mg/dL					<0.0001
MIR	29.4	3.8	17.8	38.8
Reference	19.0	3.8	10.3	27.0
SCC, ×1,000 cells/mL					0.93
MIR	1,381	543	337	3,152
Reference	1,290	470	294	2,589