Effects of early lactation concentrate level and glucogenic feed on feed intake, milk production and energy metabolism in dairy cows and heifers

In order to examine the effect of two levels of concentrate and the effect of glucogenic feed (0 l/d (GO) or 1 l/d (G1)) 16 multiparous and 16 primiparous Friesian cows were used in a factorial 2x2 design. The concentrate levels for multiparous cows were 11 kg/d (C11) and 15 kg/d (C15) and for primiparous cows 9 kg/d (C9) and 12 kg/d (C12). The glucogenic feed consisted of propylene glycol, polyols, molasses and niacin. All the animals were offered wilted silage nd libitum. The experimental period started from calving and lasted for 12 weeks. Multiparous cows substituted concentrate for silage when glucogenic feed was not given whereas with glucogenic feed the effect of concentrate on silage dry matter intake (DMI) was minor. Glucogenic feed had a minor effect on milk production at the higher level of concentrate and a negative effect on milk production at the lower level of concentrate. Due to this interaction the milk yield response to the higher level of concentrate was higher with glucogenic feed. The low rumen degradable protein supply in C11G1 was probably the cause of these interactions. The milk production response of primiparous cows to the higher level of concentrate was low. After peak yield the plasma insulin concentrations were higher with the higher concentrate level. This was accompanied by higher liveweight gain. In conclusion, the response of multiparous cows to higher concentrate level depended on the supply of rumen degradable protein, whereas the comparable response of primiparous cows was limited by milk yield potential and the needs of-growth. The glucogenic feed shelved an ability to increase plasma glucose and decrease the concentrations of ketones.