Abstract

A computer modes was developed to calculate the effect of a sires genetic merit on the yields of fat, protein and milk produced by his daughters, and on their liveweight, feed requirements and achievable stocking rates. Herd statistics, costs and prices were based on average figures for 1992. The effect of a 1 unit increase in sire Breeding Indexes (BI's) for fat, protein and milk and a 1 kg increase in average daughter liveweight on marginal farm profit per hectare were +$0.48, +$0.98, -$0.36 and -$0.49 respectively in the year of the daughters first lactation. That is, in terms of effects on gross margin per hectare, an increase of 1 unit in protein BI (sire) was equivalent to either +2 fat BI (sire), -3 milk BI (sire) or -2 kg in average daughter liveweight. The net effect of a 1 kg increase in average cow liveweight across a whole herd was calculated as being a reduction of approximately $1.30 in marginal profit per hectare. Trends in future yields of milk components were predicted from an on-farm (per cow) and an industry (supply) perspective. These trends were assumed to be solely due to genetic improvement and were based on estimated rates of genetic gain in both New Zealand (NZ) and the United States of America (USA). Based on these estimates, milk supply to the industry could increase between 30-50% in the next 30 years. This would require annual processing capacity increases in the order of 1.2 - 1.5% per year. Over the last 16 years, increases in milk supply due to greater yields per cow (genetics + management) have only been averaging around 0.6% per year. Careful planning may be required by the dairy industry in order to cope with future supply increases.

JM, Clark, CW Holmes, and DJ Garrick

Proceedings of the New Zealand Society of Animal Production, Volume 54, , 281-284, 1994