...today's research to satisfy the markets of tomorrow. The New Zealand Society of Animal Production has been the major NZ forum for the presentation of research results on farmed animals including: sheep, cattle, dairy, deer and goats for over 50 year's. Over 520 farmers, farm advisors, veterinarians, scientists and university students are members of the Society.

2008 Contents page

Effect of genotype and diet on feed conversion efficiency of dairy cows during a 600-day extended lactation

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C.V.C. PHYN, C. CLARK, P.W. ASPIN and E.S. KOLVER

Proceedings of the New Zealand Society of Animal Production 68: 100-104

This study investigated the effect of genotype and diet on the gross feed conversion efficiency (FCE) of cows milked for 600-day extended lactations (24-month season) compared with 300-day lactations (12-month season). North American (NA) and New Zealand (NZ) Holstein-Friesians (HF) grazed pasture and were supplemented with either 0, 3 or 6 kg DM concentrate/cow/day. In a normal 12-month season, gross FCE was greater for NZ HF compared with NA HF cows when fed 0 or 3 kg DM concentrate (96 and 104 vs. 90 and 99 kg milksolids (MS)/t dry matter intake (DMI), respectively), but similar when fed 6 kg DM (101 kg MS/t DMI). However, during an extended 24-month season, NZ HF cows had a lower gross FCE than NA HF when fed 6 kg DM concentrate (86 vs. 99 kg MS/t DMI, respectively) and similar FCE when fed 0 or 3 kg DM (85 and 94 vs. 86 and 99 kg MS/t DMI, respectively). Regardless of diet, gross FCE in an extended lactation was 98% of that obtained in a normal season for NA HF cows, but only 88% for NZ HF, indicating that NA HF are better suited to converting feed into high MS production in extended lactations.

Keywords: NZSAPAB; genotype; supplements; extended lactation; feed conversion efficiency

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Last modified: 2nd August 2008