Milkoscan ft spectrometer

Twin cows calved between August 2019 and January 2020, when cows were 23–29 months old. The body weight (BW, kg) of the cows was recorded daily after each milking using an automatic scale. Daily milk yield (kg/day) and dry matter intake (kg/day) were monitored throughout the lactation period. Morning and evening milk samples for analyses of fat, protein, and lactose were taken once on the lactation weeks 2 and 3 and every fourth week thereafter. Milk analyses were provided by Valio Ltd. milk laboratory in Seinäjoki using MilkoScan FT+ spectrometer (Foss Electric, Hillerød, DK). Daily average milk fat, protein, and lactose content were calculated based on the morning and evening milk yields. Energy-corrected milk yield (ECM) was calculated as proposed by Sjaunja et al. (1990) . Metabolizable energy intake (MEI, MJ/d) and average residual energy intake (REI, ME MJ/d) were calculated for each lactation month, except when cows were on summer pasture. REI was calculated by fitting a multiple linear regression model with ECM, metabolic BW (BW^0.75), and piecewise regressions of BW gain or BW loss on the MEI. Thereafter, the daily residuals from the prediction equations were defined to be REI (Mäntysaari et al., 2012 (link)). Cows with low REI values are defined as efficient.