Changes in metabolism and milk production during and after feed deprivation in primiparous cows selected for different milk fat content
2003
Agenas, Sigrid | Dahlborn, Kristina | Holtenius, Kjell
The objectives of this experiment were to study changes in metabolism and milk production due to feed deprivation in peak-lactating primiparous cows and also to investigate whether cows selected for different milk fat content show differences in the response to feed deprivation. A total of 12 primiparous cows averaging 69±9 (S.D.) days in milk were subjected to a 48-h period of total feed deprivation and were monitored for 9 days after feed deprivation. The cows were chosen from a selection program in which high yielding dairy cows of the Swedish Red and White breed are selected for either high (HFI) or low (LFI) milk fat percentage, but with the same amount of energy in the milk. HFI cows showed a more pronounced insulin-response when plasma glucose increased after refeeding. Furthermore, β-hydroxybutyrate in plasma was higher in HFI cows. Plasma non-esterified fatty acid concentration increased more than 20 times in both HFI and LFI cows when feed was removed, plasma glucose and insulin decreased and plasma urea increased. Milk yield had decreased 24 h after feed removal and was at most decreased to 51% of the initial yield. Milk content of fat, protein and lactose was similar between the selection lines but sodium and potassium in milk was higher in LFI cows. It was shown that high-yielding primiparous cows have the ability to regain milk yield and composition after a short period of feed deprivation in peak lactation.
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