Appendix 13 -Impact of improved reproduction in northern Australian cow herds

Abstract

Summary Using expert opinion, Breedcow herd models representing ABARES statistical regions across north Australia were constructed and from this an estimated weaning rate of 67% was derived. Beef CRC outputs, especially variations in EBV for age at puberty and PPAI in both Brahmans and tropical composites, coupled with preliminary modelling of potential response rates to selection, suggest that reducing both by approximately 30 days in continuously-mated Brahmans and 14 days in seasonally-mated composites was feasible over a 10-year period. The expected change was a 5% increase in pregnancy rate, except in herds where pregnancy rates are already high. Effects on mortality rates or individual animal values were unpredictable. This change was modelled using Breedcow, along with an increase in replacement bull values of $500-1,000 and a one-third reduction in bull to female mating ratios. In herds with base pregnancy rates of 80$2/weaner; cattle sales by ~6%; average gross margins per cow and AE by ~$6 and ~$7, respectively. With a $500 bull premium, the gross margins were a further$1-2 higher; ie, overall bull costs did not increase on average. A 33% adoption rate in herds with weaning rates less than 70% is expected to increase annual beef business margins by ~$12-15M per year in north Australia; this extends to a predicted regional annual economic impact of ~$40M, depending on premiums paid for high-fertility bulls. Abbreviations and acronyms use