We’ve been discussing Measures of Cow Herd Performance, including calculating pounds of calf weaned per cow exposed. While doing so we concluded that while weaning weight is important, it is not the best measure of cow herd performance. To increase weaning weight, emphasis is often placed on increased milk production, increased growth, or both. This often results in increased feed costs for the herd, which can offset the benefit of a heavier calf if not watched.
Today, we are going to shift gears and talk about ways to positively impact post-partum interval (PPI) and pregnancy rates. Consider the following criteria for an efficient beef cow herd:
1) Calving interval (number of days between calves) is 365 days or less.
2) Females raise a calf to weaning.
3) Cow mature weight and milk production fit the resources and need little to no extra feed or supplements.
If the calving interval is 365 days or less, a cow or heifer must be rebred and be pregnant by about 80 to 85 days after calving (gestation is 280 to 285 days). To make this happen, we must understand the factors that impact the post-partum interval length.
The post-partum interval (PPI) is the time from calving until the cow resumes a fertile estrous cycle. After calving, cows will enter post-partum anestrus. Anestrus means cows are not exhibiting normal estrous cycles and cannot become pregnant. Under “ideal” conditions, the anestrus lasts 40 to 60 days in beef females. During this time, uterine involution (the uterus returns to normal size) occurs and she prepares herself for the next pregnancy (Managing Postpartum Anestrus in Beef Cows for a Successful Breeding Season). If conditions are not ideal, PPI can last 100 days or more.
What factors impact the post-partum interval?
Cow age – 2 and 3-year-old females have longer PPI.
Body condition at calving – thin cows, BCS 4 and less have longer PPI.
Calving difficulty – dystocia lengthens PPI.
Because first-calf heifers have a longer PPI, they should be bred to calve their first calf ahead of the mature cow herd. Even with ideal management for reproductive performance, first-calf heifers will have a longer PPI, so they need extra time post-calving to get ready reproductively to become pregnant with their second calf. Breeding to a calving ease bull is also recommended.
Looking to animal condition, feed cows to calve in BCS of 5, and first-calf-females to calve in BCS of 6. Depending on feeds available, first-calvers will likely require some supplementation to get to BCS 6 prior to calving. For the mature (3-years-old and older) cows, if they can be in BCS 5 before calving with little to no supplementation that would indicate milk production and mature weight fit the feed/forage resources. If replacement heifers are selected from within the herd and mature cows must continually be fed extra feeds and supplements to get them to ideal body condition before calving, then reevaluate your breeding program. It may indicate mature cow weight is increasing, milk production is increasing, or both are increasing at the same time.
Using these indicators, producers can track herd performance over time and see how management and year affect productivity, as well as compare themselves to regional benchmarks. Good records, however, are key to using these indicators, so plan how your record keeping can be improved next year knowing what indicators to keep an eye out for.
-Ben Beckman is a beef systems Extension Educator serving the counties of Antelope, Cedar, Knox, Madison and Pierce. He is based out of the Cedar County Extension office in Hartington. You can reach him by phone: (402) 254-6821 or email: ben.beckman@unl.edu