Table 5. Changes in milk productivity and quality by year following low-methane feed supplementation

	Conventional feed		Low-methane feed	sig
	2021	2022	2023	sig
Milk yield (kg/day)	30.8±9.6^a	30.0±8.6^a	30.9±8.7^a	ns
Milk fat (%)	3.8±0.9^a	3.5±0.7^b	3.7±0.7^a	***
Milk protein (%)	3.4±0.4^a	3.3±0.3^b	3.3±0.4^b	***
Non-fat milk solid (%)	8.9±0.5^a	8.8±0.4^b	8.7±0.4^c	***
Somatic cell count (×10³/mL)	134.6±382.5^a	110.6±179.7^a	113.1±238.6^a	ns
MUN (mg/dL)	17.6±5.1^a	17.5±3.4^a	14.6±2.2^b	***
305-day milk yield (kg)	9,736.0±1691.3^a	9,840.4±1,836.4^a	9,738.3±1,590.5^a	ns
305-day milk fat (kg)	345.9±58.6^a	330.2±59.4^b	343.7±60.0^a	***
305-day protein yield (kg)	315.0±45.9^a	316.8±55.5^a	307.4±45.7^b	*
305-day SNF (kg)	849.1±136.1^a	851.5±154.2^a	838.6±132.6^a	ns
Mature equivalent milk yield (kg)	10,084.0±1,662.2^a	10,214.6±1,849.0^a	10,094.1±1,485.4^a	ns
Mature equivalent milk fat (kg)	363.7±62.5^a	347.2±64.6^b	360.7±59.4^a	***
Mature equivalent milk protein (kg)	332.7±46.1^a	333.9±56.2^a	324.1±42.0^b	**
Mature equivalent SNF (kg)	902.4±139.7^a	902.6±156.9^a	888.3±122.3^a	ns

Values are mean±SD.
p<0.05,
p<0.01,
p<0.001.
values with different superscripts in the same row differ significantly.
SNF, solids-not-fat; MUN, milk urea nitrogen; NS, not significant.