High prices for heifer calves as feeders and current market prices for replacement bred heifers and cows brings to light the high cost associated with herd replacement and the value of longevity or stayability in the herd. Considering the differential cost between selling and culling a $600 cow and replacing her with a $1200 bred female, or holding back a $650 heifer and developing and breeding here at a cost $300 plus interest, the cost for every percent of herd replacement is around $4 to $6 for every cow in the herd. The depreciation and replacement cost at a 10% annual replacement rate becomes $50 against every cow in the herd. It rises to $80 per head at a 16% replacement rate. Replacement and deprecation are a major cost to cow-cow operators.

Cows have a limited production life. Most enter the herd as two year olds, come into greatest production from ages 5 to 9, and then start to drop off. By age 12 or so production likely fallen off significantly due to lose of teeth, unsoundness being less completive; resulting in lower condition, less milk, later breeding and lighter calves. Cows are routinely culled at some age or condition of teeth related to age and accounts for a primary reason for culling.

However herd data suggests by the time cows reach the age of ten, less than 20% of those brought in as two year olds are still in the here. Many have been culled much earlier primarily for reproduction reasons. They turned up open, lost a calf, or bred back to late for the herd schedule. A smaller percentage is culled for a variety of non-age related factors such as temperament, health, unsoundness, and low production. Some data suggests over 50% of replacements are culled before they are in the herd five years. This explains why typical herd replacement rates are often much higher than a theoretical 10% due to age, often 15 to 17%.

Certainly the average age of culled cows and the rate of replacement vary greatly and are highly affected by factors as operating style, herd management, as well as feed resources, climate, and genetics. Breeding and management studies and simulations suggest several factors that help reduce the number of young cows that leave the herd.

From a genetic standpoint, differences have been illustrated by breed type or crosses in the average years of productive life or percent remaining in the herd at some advanced age. Due to heterosis, crossbred cows tend to have a year of additional productive life than straightbreds. Predicted survival to 12 years with management to remove all open cows every year suggests differences between breeds and crosses of over 30% of cows remaining in the herd at age 12. An average advantage of crossbreds over straightbreds being 8.5%.

Breed associations with data reporting on herd inventories and cow disposal have developed a genetic evaluation for stayability, relating to the probability of a sire’s daughters staying in the herd to the age of six years. It is a fairly lowly heritable trait, however stayability EPDs are useful particularly on older sires with producing daughters to select for longevity. It is a compound trait composed of all the factors causing a cow to be culled prior to six years of age. Variation between sires is significant relating to about 7 percentage points from bulls at the upper and lower third percentiles.(7 more of 100 daughters likely to remain in herd at age 6.)

Heifer development and nutrition play a significant role in their prospects for staying in the herd. Having heifers grown to 65% of their projected mature weight at the start of the breeding season and be at a body condition score of 6 at calving are sound recommendations. There is a risk of over feeding yearling heifers of the wrong type and match to herd resources, insuring they breed as yearlings only to fail as 2 and 3 year olds. It can be advantageous to moderately feed heifers and limit the breeding season to identify the most fertile and fit heifers and finish developing the second year. This requires bred heifers and young cows are managed separate from the main herd for more targeted nutrition.

A pool of crossbred heifers: of adapted breeds; by sires of the right type with genetic superiority for stayability; growth and milk matched to feed resources; screened for soundness and disposition; of high health status; of appropriate age and weight for low cost development; fed to achieve targeted size by breeding with modest input; bred to proven calving easier sires wintered to calving at moderate condition; and then managed to avoid nutritional stress the following year; will increase your odds of bringing in replacements that stay in the herd a long time and minimize the herd replacement rate. Hopefully resulting in more cows in their years of greatest productivity, greater calf weights, lower depreciation/replacement cost per cow, fewer feed resources being utilized for non-producers; and a greater return to time, management, and a capitol invested in the cow business.