Cattle sales and deemed cost of sales 3 months to 31 Mar 13  $000 12 months to 31 Dec 12  $000 3 months to 31 Mar 12  $000  (reviewed) Cattle sales 40,569  236,812  37,4 63  Cost of sales (37,669) (219,078) (35,372) Selling expenses (2,900) (17,73 4) (2,091) Deemed cost of sales (40,569) (236,812) (37,463) Sales margin - -  - Cattle Fair Value Adjustments Cattle purchases (5,683) (62,131) (10,848) Fair value of purchases 8,801  75,875  13,446  Freight & other costs (669) (5,368) (619) Fair value adjustments (1,333) 32,030  6,973  Biological transformation 1,116 40,406 8,952 Market value changes (43,179) (12,224) (6,002) Natural increase 7,897  70,375  12,974  Attrition (3,448) (10,793) (3,433) Other (52) (214) (39) Total cattle fair value adjustments (37,666) 87,550 12,452 3 months to  31 Mar 13  $000 3 months to  31 Mar 13  Head 1 2 months to  31 Dec 12  $000 1 2 months to  31 Dec 12  Head 3 months to  31 Mar 12  $000  (reviewed) 3 months to  31 Mar 12  Head  (reviewed) Calf accrual opening 19,386  96,323  16,796  88,077  16,796  88,077  Net movement 5,444 27,369  1,660  8,246  10,004 43,000 Net fair value adjustments* (225) - 930 - 1,438 - Calf accrual closing 24,605 123,692 19,386 96,323 28,238 131,077 Average Value per head $199 $201 $215 NOTES TO THE CONSOLIDATED FINANCIAL STATEMENTS CONT For the three months ended 31 March 2013 15. BIOLOGICAL ASSETS — LIVESTOCK (CONTINUED) Unbranded Calves Calves are valued internally as there is no observable market for them� The value is based on the $/head market value for older trading cattle  adjusted for weight differential� A 5% movement in $/head would give rise to a value change of $1,200,000� The number of head in the calf  assessment is derived from the number of productive cows, the results of pregnancy testing, and the percentage of brandings assessed each year�  A 5% change in the number of calves would give rise to a value change of $1,200,000� *These fair value adjustments are recognised in the Cattle fair value adjustments line of the Consolidated Income Statement� 84 Australian Agricultural Company Limited