Abstract

The feed intake capacity (FIC) of pregnant, non-lactating Holstein-Friesian cows, selected for either high (H) or low (L) breeding values for live weight (LW), was measured when fed to appetite on hay (7.5 MJ ME/kg DM in 1998) and on pasture (11.1 MJ ME/kg DM in 1999). The H cows were heavier than the L cows in both years (546 v 482 kg; 540 v 464 kg in years 1 and 2 respectively), and the H cows ate significantly (P<0.01) more feed than the L cows in both years (12.5 v 11.1 kg hay DM, and 13.1 v 11.6 kg pasture DM per day in years 1 and 2 respectively. Regression analysis showed that for each 100-kg increase in LW, daily DMI per cow increased by 1.43 and 1.81 kg respectively in 1998, and 1999. Regression analysis of the data after conversion into log10 , showed that DMI was proportional to LW0.66 and LW0.65 in 1998 and 1999 respectively. These results indicate that the genetically heavier cows ate more DM than the genetically lighter cows. Nevertheless, the difference between maintenance costs and FIC (or "net" FIC) may be similar for both strains, so that the smaller intake of the lighter cows does not disadvantage their productive capacity.

A, Caicedo-Caldas, V Lemus-Ramirez, CW Holmes, and N Lopez-Villalobos

Proceedings of the New Zealand Society of Animal Production, Volume 61, Christchurch, 207-209, 2001