Abstract

The objective of this work was to compare individual intake and grazing behaviour of different strains of Holstein-Friesian dairy cows. Strains tested were high breeding worth 1990’s Holstein-Friesian of overseas (OS90) or NZ origin (NZ90), and a 1970 NZ strain of Friesian (NZ70), farmed under different feeding systems defined by feed allowance per cow per year. Feed allowance ranged from 4.5 to 7.0 t DM cow-1 year-1, based on different stocking rates and supplement inputs. Each system (one strain at one total annual allowance) was managed using a common set of decision rules and all the strains were in similar body condition score (BCS) at calving. Milksolids production, liveweight and BCS were measured routinely, and during September 2002 (55-75 days in milk) daily DMI and digestibility (DMD) were estimated for each cow by the n-alkane method. Grazing behaviour was observed visually. Daily milksolids yield (per cow and per 100 kg LW) were similar for NZ90 and OS90, which were higher than NZ70 (p<0.01). At the start of the season OS90 cows were heavier (p<0.05) than cows of the other two strains and NZ90 cows heavier (p<0.05) than NZ70 cows, however they were similar in BCS. During September OS90 cows were just slightly heavier than the other two strains (p=0.16), but with lower BCS (p<0.01). Between the start of the season and September, LW and BCS decreases for OS90 cows were significantly higher (p<0.05) than for cows in the other two strains. Slightly higher DMI (per cow and per 100 kg LW) were recorded for the NZ90’s than for NZ70 and OS90. Grazing time, ruminating time or biting rate was similar across strains. These results suggest that the OS90 was not able to eat sufficient pasture and used more body energy reserves to produce similar MS yield as NZ90.

JL, Rossi, KA MacDonald, B Thorrold, CW Holmes, C Matthew, and J Hodgson

Proceedings of the New Zealand Society of Animal Production, Volume 64, Hamilton, 232-236, 2004