Cow longevity or retention is an important economic trait to cow-calf producers; however, longevity has relatively low heritability. Although there is a lot of opportunity to increase cow herd retention rate in cow-calf herds, research showing genetic selection or management strategies making substantial impacts on longevity is limited. We do know heifer development and other management strategies can impact cow herd retention. Decreasing the number of cows culled due to reproductive failure decreases the number of replacement heifers needed, lowers overall replacement costs and increases total pounds of calf weaned since older cows tend to wean a larger calf.
Developing replacement heifers is one of the most expensive and complex management decisions for a cow-calf producer and also has long-term implications for profitability. Reducing heifer investment costs while maintaining reproductive performance is important for profitability due to the number of calf crops required to pay for development costs – anywhere from 3 to 10 years of age to pay off development and opportunity costs, depending on the cost of production and initial heifer costs. The issue for many producers in semiarid environments is heifer development costs and challenges in rebreeding young cows.
Supplementing for reproduction efficiency
Previous long-term research has illustrated that managing cows under nutritionally limited environments may lead to adaptations that result in relatively high levels of reproductive success under lower input levels. In New Mexico, we showed the impact of programming animals to fit their given environment and how nutritional inputs and even type of protein supplement (i.e., low-rumen undegradable protein supplements versus high-rumen undegradable protein supplements) can have on cow herd longevity (Figure 1).
We fed yearling spring-born beef heifers one of three developmental treatment groups:
- Range developed and fed a 36% crude protein (CP) cottonseed meal-based supplement containing 36% rumen undegradable protein (RUP)
- Range developed and fed a 36% CP cottonseed meal-based supplement containing 50% RUP
- Fed a commercial concentrate growing diet in a drylot formulated to achieve 1.5 pounds of gain per day
Protein supplements were fed three days a week at a rate equivalent to 2 pounds daily per heifer. During the developmental treatment period, heifers developed at a moderate rate of gain in the feedlot had increased average daily gain (ADG) of 1.5 pounds per day from the initiation of treatments to the start of breeding compared to range-raised heifers consuming low-quality range with protein supplementation (0.57 pounds per day). Even with the low ADG until breeding, the retention rate in the breeding herd through 5 years of age for range-developed heifers fed a high-RUP supplement had 68% retention compared to 41% retention for range-raised heifers fed a lower-RUP supplement and 42% retention rate for heifers developed in a feedlot.
A short-term (fewer than 100 days) change in replacement heifer management of taking heifers out of their limited nutrient environment resulted in long-term cow productivity and retention. This data indicates two things. The first is that the type of protein matters. RUP sources can impact short- and long-term reproductive performance. The second is that managing heifers to fit their environment improves the probability of long-term cow herd retention in limited nutrient environments.
Breedback
Rebreeding percentage and timing of pregnancy in summer-calving young cows (2- and 3-year-olds) can be a major challenge for beef producers. To combat this issue, select heifers with the ability to rebreed in a declining forage quality environment. In a long-term heifer study, Red Angus-Simmental crossbred heifers were utilized to determine the impact of converting March-born heifers (convert) into a May-calving herd compared to May-born heifers (Figure 2). May-born heifers were retrospectively grouped into two different groups: heifers born in the first 21 days of calving as a heifer calf (early) or heifers born after the 21 days of calving as a heifer calf (late). After 5 years of age, retention rate was increased in convert cows compared to early and late May-born cows, with no difference between the two May-born heifer groups.
In breeding seasons with limited forage quality, selecting older heifers born in earlier calving seasons may allow for increased forage intake capacity. The inability of young cows to consume enough energy, especially during early lactation, is a driver of delayed resumption of estrus and ultimately decreased pregnancy rates. Older animals even at a similar bodyweight tend to have increased forage intake. This may be advantageous during periods when forage quality is approaching 7% CP or less. In resource-limited breeding seasons, cow-calf producers may want to consider purchasing heifers from earlier-calving herds from similar environments and management to increase long-term profitability.
Postpartum management
Other management strategies outside of heifer selection and development that may increase longevity would be early postpartum management strategies. This period from calving until the cow conceives is the most critical period in a cow’s production cycle, and minimizing this period is important for several reasons. A shortened postpartum interval, or a large percentage of cows cycling prior to breeding, will result in having increased conception rates than cows that cycle later, which is largely due to cows having more chances of getting pregnant during a defined breeding season. This can be a large challenge in some environments due to limited nutrients in semiarid and arid environments. If protein and energy requirements are not being met, the postpartum interval can be increased, causing a delay in conception date and subsequent delay in calving.
Strategically fed protein supplementation has been shown to improve fertility under certain conditions, including thin body-conditioned cows. One thing to remember is that not all protein is created equal for ruminants, due to rumen fermentation. Rumen degradable protein (RDP) supplements such as alfalfa hay or cottonseed meal help increase forage intake and digestibility of low-quality forages; however, once rumen microbes’ need for protein is met, RUP sources such as dried distillers grains (DDG) can have a larger impact on cow performance. Our research has shown that protein sources high in RUP and low in RDP can increase pregnancy rates and decrease the postpartum interval in young beef cows.
In addition to protein type, some feed additives have been used to effectively shorten the postpartum interval of young beef cows. Ionophores have been shown to shorten postpartum intervals by an average of 18 days across several different studies with cows and first-calf heifers. A product that increases glucose availability to ruminants, fed in protein supplements at low amounts (40 grams per day) during early lactation has been shown to shorten postpartum intervals of young range beef cows by seven days and increase overall pregnancy rates.
References omitted but are available upon request by sending an email to an editor.
