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Publication Date
1981
Description
The New Zealand dairy industry is almost totally reliant on grazed herbage for the production of milk solids, but few data exist on the efficiency with which lactating cows utilize energy of fresh herbage offered as the sole diet. One hundred thirty-two energy balances have been conducted by indirect calorimetry using cows at two levels of feeding and at two stages of lactation over 3 years. Mixed pasture suitable for grazing and cut twice daily was the sole diet. Data for the utilization and partitioning of energy have been subjected to regression analysis on a within-cow basis. Efficiency of utilization of metabolized energy (ME) for energy balance ( milk + tissue) was higher in early lactation ( spring) than in midlactation (autumn) (56% and 50%, respectively), and at both stages of lactation efficiency was lower than the 60% proposed by van Es (1975). Reasons for reduced efficiency of utilization of ME were associated with higher heat increment of feed/unit intake in midlactation. The factors responsible included changing feed composition, reduction in ME content of the herbage, and increased energy cost of excretion of excess nitrogen in midlactation.
Citation
Trigg, T E.; Parr, C R.; and Cox, N R., "Utilization of Energy of Fresh Pasture by Lactating Dairy Cows" (1981). IGC Proceedings (1977-2023). 13.
(URL: https://uknowledge.uky.edu/igc/1981/section11/13)
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Utilization of Energy of Fresh Pasture by Lactating Dairy Cows
The New Zealand dairy industry is almost totally reliant on grazed herbage for the production of milk solids, but few data exist on the efficiency with which lactating cows utilize energy of fresh herbage offered as the sole diet. One hundred thirty-two energy balances have been conducted by indirect calorimetry using cows at two levels of feeding and at two stages of lactation over 3 years. Mixed pasture suitable for grazing and cut twice daily was the sole diet. Data for the utilization and partitioning of energy have been subjected to regression analysis on a within-cow basis. Efficiency of utilization of metabolized energy (ME) for energy balance ( milk + tissue) was higher in early lactation ( spring) than in midlactation (autumn) (56% and 50%, respectively), and at both stages of lactation efficiency was lower than the 60% proposed by van Es (1975). Reasons for reduced efficiency of utilization of ME were associated with higher heat increment of feed/unit intake in midlactation. The factors responsible included changing feed composition, reduction in ME content of the herbage, and increased energy cost of excretion of excess nitrogen in midlactation.
