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The Use of Test Day Information to Predict Energy Intake of Dairy Cows in Early Lactation

Massey University, Palmerston North, New Zealand 11222

Corresponding author—e-mail: c.heuer{at}massey.ac.nz.

This study aimed to validate a previously developed model for the estimation of energy balance in high producing dairy cows from test day information during the first 12 wk of lactation. Monensin (an ionophor) increases the energy status of dairy cows. Gold standard for the validation was a higher energy status, indicated by lower blood ketone body concentrations, lower percent milk fat, and higher milk-yield of monensin-supplemented than control cows in 8 randomized block design feeding trials. Estimated energy intake (eE_intake) was calculated as estimated energy balance (eEB) plus energy in actual milk produced (in units of MJ_nel) plus a constant or variable amount of energy required for maintenance. The variable amount was based on BW, while the constant was the average BW in each parity group (1, 2, 3, 4+). Both eEB and eE_intake were compared between groups of cows with and without monensin supplementation (n = 600 lactations). The trials started with a presupplement period during lactation wk 2 to 5 followed by a supplementation period during lactation wk 6 to 12. During the presupplement period, both eEB and eE_intake were similar for all cows. At 2, 3, and 8 wk after starting the monensin supplementation, the eEB of the supplemented cows was significantly higher, while eE_intake was significantly higher throughout the supplementation period. The results were similar for the 2 methods of calculating energy for maintenance, variable or constant. The feed conversion efficiency, calculated as kg of fat-protein corrected milk per MJ_nel of eE_intake, was highest in first calving cows compared with cows having more lactations, and correlated with standard milk production at trial group level. It was concluded that eE_intake was a valid measure of net energy absorption.

Key Words: predicting energy balance • herd test data • dairy herd

Abbreviation key: ACAC = acetoacetate, BHB = beta-hydroxy-butyrate, eEB = estimated energy balance, eEI = estimated energy intake, FPCM = fat-protein-corrected milk