Biological and economic consequences of changes in voluntary culling policies

The objectives of this study were to estimate and compare the biological and economic consequences of the implementation two policies including non-optimal and optimal culling decisions. For this purpose, data were collected during 2015 and 2016 from one of large dairy herds inIsfahan province. Then using different procedure of SAS software (NLIN, MEANS, LIFETEST), the biological parameters of this herd (including the shape of Lactation curve, risk of involuntary culling and probability of pregnancy in different milk periods and month in milk after calving) were estimated. In the following, by entering the biological and financial parameters to the bio_economic model developed in DairyVIP software, the herd status was simulated in different situations. The basis for optimal and non-optimal decisions were minimizing the opportunity cost and reach the daily production of non-pregnant cows to less than 20 kg, respectively. By implementing optimal policies, the annual culling rate increased from 31.9% to 41.9%, which resulted in an increase of 9,650,000 rials in heifers purchase cost. However, an increase in the revenue from the sale of milk calves and culled cow led to 3,390,000 Rials an overall improvement in net annual profit by each cow. The results of this research can help to change in dairy producer's attitude toward the replacement decision.