When does the hind become a priority over the calf in autumn? When should we switch our focus from weaning weight (this years production) to hind conception and mating date (next years production)? We can attempt to answer these questions now that we know some of the science linking condition score and reproduction.
What is driving the profitability of our deer farm?
The number of live calves produced each season is a major driver. It is normally expressed as the number (or weight) of surviving calves produced annually per breeding hind - or the 'weaning rate' of the herd. Less calves born have both direct and indirect impacts on farm production and profitability.
Direct effects are due to less calves for sale.
Current calf losses range from 2 -15% in mixed age hinds and 5 -25% (or greater) in first calvers.
This affects potential income by approximately +/- $225/100 hinds mated for every 1% shift in survival (valued at weaning as a 50kg weaner @ $4.50/kg LW).
Indirect effects are related to later calving, higher culling and changing age structure of the herd. Later calving means lower weaning weight. Less calves means more dries so a higher number of replacements kept. More replacements means younger hinds which tend to rear lighter calves (calves born to first calvers are born on average 17 days later and potentially 5.5kg lighter at weaning). The number of calves sold also declines as weaning percentage declines.
Leaving the calf on the hind in autumn will help improve calf liveweight gain. On-farm studies show that calves may grow on average 50g/d faster between March and June if left unweaned. Variation between farms is high, and often higher than 50g/d, showing that farmer management is very important.
Post-rut weaning may delay conception date by an average of 10 days (equal to 4kg weaning weight).
Again farm to farm variation is high, and relates to the management of the farmer. The extra growth rate of the calf may add 4kg to June weight (80 days at 50g/d), but 10 days later conception may lower June weight by 4kg (10 days at 400g/d). The two practices tend to cancel one another out over time and often hind condition is the buffer. However losses can be more significant than this as losses in hind condition can lead to further reproductive losses.
What is the overall effect of hind condition on future productivity?
Condition score and changes in condition score are relatively sensitive indicators of potential performance.
Condition score 3 or reduced down to 3.
Very few conception failures and high pregnancy rate.
Slight delay in conception only if condition score loss was rapid.
7-10 days delay in conception.
10-14 day delay in conception.
Loss of condition score in hinds is most likely in late summer and early autumn when the amount of feed available declines below approximately 1800kg DM/ha. The table above shows how a lower BCS at mating reduces the number of calves weaned, and delays the start of calving.
This loss of BC directly impacts the return per hind and increases the necessary cost of feed. It is cheaper to buy feed to keep condition score on the hind, rather than trying to gain it back later.
Both direct and indirect impacts can be calculated at the whole herd level. Here they are calculated as if we are running a herd at a constant BCS of 3, 2.5 or 2. Because the hinds are lighter, then we can run more, so each example is calculated using the same amount of feed as the original herd of 1000 hinds in condition score 3, weaning in early March, culling wet dries and hinds over 10 years old.
* Days to weaning are higher for better feed hinds because the calves are born earlier.
Even by being able to run more hinds if they are in lower condition we still find that the economic optimum is when hinds have a condition score of 3, so we can use hind condition score as an indicator of when making weaning decisions.
98% conception rate in Mixed-Age hinds.
85% in the first cycle.
7 November start of calving.
Are my hinds in condition score 3 in mid-January?
Am I ready to wean (see Weaning Management)?
Can I get my stag in early?
How much feed do I have and what is the quality?
How fast are my calves growing?