Prediction of the yields of milk constituents in dairy cows offered silage ad libitum and concentrates at a flat rate

Abstract

Individually recorded milk yields, yields and concentrations of milk components, food intakes and live weights of multiparous dairy cows given silage ad libitum and concentrates at a flat rate in weeks 4 to 13 of lactation and data for silage and concentrate composition from experiments conducted at four sites, were used to obtain simple correlations and multiple linear regressions of yields and concentrations of milk constituents on other variables.Simple correlations between yields and concentrations and other variables were low. Yield terms were most highly correlated with intake terms. Milk fat concentration was most highly correlated with silage fibre concentration. Milk protein concentration was most highly correlated with digestible energy intake. The best multiple regression models including time effects accounted proportionately for 0·35 of the variation in fat yield, 0·51 in protein yield, 0·55 in lactose yield, 0·39 in total milk yield, 0·19 in fat concentration, 043 in protein concentration and 0·19 in lactose concentration. Most of these models included terms for silage intake and cow live weight which are not generally available on farms. More practical models including fewer independent variates were therefore produced. These models accounted proportionately for 0·33 of the variation in fat yield, 048 in protein yield, 0·50 in lactose yield, 0·32 in total milk yield, 0·19 in fat concentration, 0·40 in protein concentration and 0·17 in lactose concentration.

The effects of wilting of grass prior to ensiling on the response to bacterial inoculation. 2. Intake and performance by dairy cattle over three harvests

“…The significant increase in protein concentration in milk following wilting in the present study may have reflected higher energy intakes from the wilted silages (Sporndly, 1989;Rook, Sutton and France, 1992). Positive responses in fat and protein concentrations in milk of this magnitude have been seldom recorded previously in comparisons of unwilted with wilted silages, and have important implications for milk quota management within European Union countries.…”

Meta-analysis of factors affecting milk component yields in dairy cattle

“…Hristov et al [ 7 ] showed the negative correlation of MPY with fermentable NDF and protein fraction B1 intakes. Diets for lactating dairy cows were formulated to be highly digestible and, in most situations, DMI was strongly related to intake of total digestible nutrients or energy (net energy for lactation or metabolizable energy) intake (Hristov et al, [ 19 ]). In Huhtanen and Hristov [ 8 ] the best prediction models for MPY were based on total digestible nutrients (TDN), CP intake and CP degradability.…”

Sources of variation in yields and concentrations of milk solids in dairy cows

“…Recent attempts to predict yields and concentrations of milk solids from food input variables and cow variables such as parity, live weight and food intake showed that a considerable proportion of the variation was not accounted for by these sources, particularly for milk fat concentration (Sporndly, 1989;Rook, Sutton and France, 1992). Atwal and Erfle (1990) examined day-to-day variation in milk fat yields and concentrations in cows over a 14-day period and suggested that there might be a 'wavelike' pattern with a 5-to 7-day wavelength which they suggested might be due to metabolic regulation of lipolysis on energy deficient diets.…”