Herbage intake, grazing behaviour and feed conversion efficiency of
lactating Holstein-Friesian lactating cows which differ genetically for liveweight
D. Laborde, J.G. Garcia-Muniz and C.W. Holmes
Department of Animal Science, Massey University, Private Bag 11222,
Palmerston
E-Mail:
Proceedings of the New Zealand Society of Animal Production. 1998,
58: 128-131
Two experiments were carried out to compare the feed conversion
efficiency at high pasture allowances in early (EXP1) and mid-lactation
(EXP2) of genetically heavy (H) or light (L) Holstein-Friesian cows (H =
487, L = 410 kg, P<0.001). Average milksolids (MS) yield was not
significantly different in EXP1 (H = 1.73, L = 1.64 kg MS), but the H
line had higher MS yield than the L line in EXP2 (H = 1.70, L = 1.54
kg/cow/day, P<0.001). The mean individual dry matter intakes (DMI,
kg/cow/day), measured using the n-alkanes technique, were higher for H
cows in both EXP1 (H = 15.5 and L = 13.9; P<0.05) and EXP2 (H = 12.2
and L = 10.8; P<0.05). However, herbage intake was not significantly
different between the H and L cows when adjusted to a common MS yield.
Feed conversion efficiency (g MS/kg DMI) was slightly higher for the L
cows during EXP1 (H = 114, L = 120, P = <0.1), but not different for H
and L cows during EXP2 (H = 144, L = 143). The calculated bite size of
the H cows was on average 0.095 g DM/bite (pooled for the two
experiments) heavier (P<0.05) than that of the L cows, but the L cows
showed a consistently faster rate of biting than the H cows (H = 51, L =
56 bites/min, P<0.05). Although the H cows had higher MS yield than
the L cows, especially in EXP2, the higher MS yield was not associated
with increased efficiency, presumably because the H cows required more
energy for maintenance than the L cows.
Keywords: NZSAPAB;
Feed conversion efficiency; grazing behaviour; dairy cows; live
weight.
Last Updated 12-09-1998
