Effects of importing semen of Holstein, Holstein-Friesian and Jersey bulls on the future profitability of an Argentine dairy farm

摘要

Effects of mating strategies and payment systems on farm profit (dollar/ha) of an Argentine dairy herd were evaluated. The mating strategies were: upgrading to Holstein, upgrading to Holstein-Friesian, upgrading to Jersey and rotational crossbreeding Holstein-Friesian X Jersey using imported semen. Holstein bulls were selected for milk yield whereas Holstein-Friesian and Jersey bulls were selected on an economic index combining estimated breeding values for lactation yields of milk, fat and proteinand mature cow body weight weighted by respective relative economic values. Payment systems were milk volume, fat yield, protein yield, milk solids (fat plus protein) yield and multiple components based on fat, protein and volume. Phenotypic and economic performances for a period of 20 years were obtained with deterministic modelling. Phenotypic performance was predicted from the genetic merit of bulls and cows, and effects of breed, heterosis, age and genotype X environment interaction. Feed requirements per cow were estimated for maintenance, lactation, pregnancy, and growth of the replacements. Dry matter requirements were supplied by a ration composed of pasture (80 p.100), silage (10 p.100) and concentrate (10 p. 100). Stocking rate was calculated by assuming 6000 kg of dry matter utilised annually per hectare. Productivity per hectare was calculated as performance per cow multiplied by stocking rate. Profit was calculated as the difference between income (milk and beef) and costs related to thenumber of cows and the land area farmed. Upgrading the herd to Holstein for 20 years resulted in the heaviest cows with the highest per cow production of milk, fat and protein, highest feed requirements per cow, the lowest stocking rate, the lowest production of fat and protein per hectare and the highest production of milk per hectare. Upgrading to Jersey resulted in the lightest cows with the lowest per cow production of milk, fat and protein, lowest feed requirements per cow, consequently, the highest stocking rate, the highest production of fat per hectare, intermediate production of protein per hectare and the lowest production of milk per hectare. Rotational Holstein-Friesian x Jersey crossbreeding resulted in similar production of fat and protein per hectare to upgrading to Jersey although this was achieved with a lower stocking rate. Profit in the base year was calculated to be 103 dollar/ha. Upgrading to Holstein resulted in the highest profit (322 dollar/ha) in year 20 if milk was paid on milk volume. Upgrading to Jersey resulted in the highest profit (311 dollar/ha) in year 20 if milk was paid on fat yield. Rotational crossbreeding resulted in the highest profit in year 20 for all other payment systems. Results suggest that semen from bulls of foreign populations must be strategically used according to production and economic circumstances if profitability is to be maximised. Interactions between genotype and physical environment and between genotype and economic environment must be carefully considered. Rotational crossbreeding systems could increase profitability of Argentine dairy herds under the market conditions assumed in this analysis.