DIM in high-yielding dairy cows

Feed intake increased steadily from 14.9 0.2 kg DM/d (wk 1 p.p.) to over 22 kg DM/d in wks 7-12 of period 1. NEB had a nadir in wk 1 p.p. with -46.1MJ NEL/d and cows covered only 70% of their energetic requirements by feed intake. EB turned positive in wk 9 p.p. over all cows and reached a level of 103% of the calculated demand before experimental period 2. During period 2 restricted cows had a mean DM1 of 10.3 kg/d and thereof covered 51% of their energy requirements, whereas control cows had a DM1 of 21.1 kg/d and an energy balance of 104%. In wk 1 of realimentation control cows still had a higher feed intake than restricted cows (20.4 vs. 18.7 kg DM/d F 0.01). EB for restricted cows turned positive again in wk 2 of realimentation and averaged 109% of the calculated demand until the end of the study (control cows 108%). 

The LW decreased after parturition from 668 kg (wk 1 p.p.) to 647 kg (wk 4 p.p.). In period 2 feed restricted cows showed a lower LW than control animals (627 vs. 655 kg P 0.0S). During the realimentation period restricted cows gained LW and were equal to control cows in wk 2. 

Fenwick, M. A., R. Fitzpatrick, D.A. Kenny, M.G. Diskin, J. Patton, J.J. Murphy and D.C. Wathes, 2008. Interrelationships between negative energy balance (NEB) and IGF regulation in liver of lactating dairy cows. Domestic Animal Endocrinology 34, 31-44. 

Van Dorland, H.A., S. Richter, I. Morel, M.G. Doherr, N. Castro, and R.M. Bruckmaier, 2009. Variation in hepatic regulation of metabolism during the dry period and in early lactation in dairy cows. J. Dairy Sci. 92, 1924-1940. 

Dietary supplies of energy and protein to dairy cows are 2 important levers by which milk yield and composition can be modulated in the short term. When one of those supplies increases, milk yield increases curvilinearly and reaches plateaus (Coulon and Remond, 1991 Verite and Delaby, 2000). However, energy and protein suppHes often vary simultaneously, but only few studies have addressed their possible interaction (Gordon and Forbes, 1970 Krohn and Andersen, 1980 Broderick, 2003). The objective of this trial was thus to build response equations of milk yield and composition to joint variations of energy and protein supplies, and to determine whether those responses depend on parity and production level. 

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