Herd Replacement Rate and Production Efficiency

Farm technical efficiency ratios e.g. milksolids per cow (kg MS/cow), use averaged figures and ignore detail that an effective economic analysis demands. A resource allocation optimisation linear program (LP) model, “GSL”, was used to analyse the effect on profit (cash surplus) of varying age-group production data (kg MS/cow/yr) for a 300 ha farm. Initially, the herd was fixed at 750 cows, average production 400 kg MS/animal /yr; all replacement heifers grazed off; flexible drying off and culling dates; cows grazed off in winter, 8-10 weeks. Common prices were assumed for milk, surplus calves and cull cows. Grazing off costs depended on age groups of heifers and cows. Initial herd (H) parameters were: replacement rate 25%; loss rate 5%; average cow life 6 years, represented as H:25/5/6. Heifer production as a percentage (P) of a mature cow (100): 2 yr old 70%; 3 yr old 85%; 4 yr old 95%, represented as P:70/85/95. The LP model purchased 736.4 t feed, produced 480 kg MS/mature cow, and profit (cash surplus) $938,260. When the LP was constrained to a herd structure of H:17/3/8; P:90/100/100; herd size 750; production 400 kg MS/animal, the model purchased 792 t feed, produced 422 kg MS/mature cow, and profit $952,795. When the LP was constrained only to production of 400 kg MS/animal, it calculated the optimum combination of resources: herd size 630; purchased feed 118 t. Total production was 252,360 kg MS; profit was $988,520. It was found that using average kg MS/cow to compare between scenarios for a farm is not an accurate predictor of farm system performance or change.