Reproductive efficiency can be defined as the number of cows exposed to the bull that became pregnant, typically within a defined breeding season. Increasing pregnancy and calving percentage has a direct impact on the number of calves born, weaned and available for selling and can thus have a direct impact on the producer’s profitability. One of the best indicators of reproductive efficiency is pounds weaned per exposed female, as this accounts for the proportion of cows that did not get bred. Open cows do carry a cost, and the goal is to not only ensure that as many heifers and cows get bred and rebred every season as possible, but to wean a healthy calf as well.
Several factors impact reproductive efficiency, including selection and genetics, herd health and management, as well as meeting the cow’s nutritional requirements. Cows in poor nutritional status are less likely to cycle, become pregnant, give birth to a healthy, live calf and get rebred.
Reproductive failures are often tied to suboptimal trace mineral nutrition, which can impact not only the individual animal but the well-being of her offspring, too.
Trace minerals are involved in the synthesis of reproductive hormones, the reduction of free radicals and the improvement of the uterine microenvironment for embryonic implantation, as well as fetal growth and development. Considering that, for the most part, reproductive organs develop during early gestation, it is clear how the dam’s nutritional and trace mineral status can impact fetal development and future performance, as well.
Since most grains and forages typically vary in terms of their nutritive value, especially trace mineral concentration, supplementation can become a necessity. Supplemental copper, zinc, manganese and selenium are especially needed to optimize the cattle herd’s trace mineral status, as meeting their trace mineral requirements is fundamental for achieving optimal immunity, health, reproductive efficiency and growth.
Knowing this, supplemental trace minerals are provided to bridge the gap between the amount available through the forages and the cow’s nutritional requirements. However, the form in which those trace minerals are provided – either inorganic or organic – can impact how the herd will respond to the trace mineral program.
Inorganic trace minerals – including sulfates, oxides, chlorides and hydroxies – are typically inexpensive byproducts of other industrial processes and are often fed in excess to avoid deficiencies. However, due to the lower relative bioavailability of inorganic trace minerals, animals do not necessarily benefit from oversupplementation. Additionally, these high levels of inorganic trace minerals are often associated with mineral-to-mineral antagonisms, a higher degree of vitamin degradation and higher levels of excretion into the environment.
Organic trace minerals – for example, proteinates and organic selenium yeast – are closer to the form in which trace minerals are found in nature. As a result, organic trace minerals offer better absorption and utilization, which translates to a higher bioavailability and fewer dietary interactions, meaning that minerals offered in an organic form can typically be supplemented at lower levels.
The advantages of supplementing with organic trace minerals have been well documented and include improved ovarian activity, increased conception rates and getting cattle bred back sooner. Typically, calves from cows supplemented with organic trace minerals are also in better health and immune status, which has a positive impact on growth and weaning weights.
Organic trace minerals can also affect fertility parameters in successive generations, and this is often referred to as fetal or maternal programming.
In a recent beef study, the response of Angus and Brangus cows and their calves to either inorganic or organic (i.e., proteinates and selenium yeast) trace mineral sources was evaluated. The results of that study were decisive:
- For cows supplemented with organic trace minerals 90 days pre-calving throughout the heifer developmental period (year one), heifer calves reached puberty nine days earlier and were confirmed pregnant eight days earlier than heifers from the inorganic-supplemented cows.
- The results for year two, where cows were supplemented for the entire year and calves were thus exposed to organic trace mineral supplementation from conception throughout the heifer development period (year two), the heifers from cows supplemented with organic trace minerals reached puberty 41 days earlier and were confirmed pregnant 18 days earlier than heifers from inorganic mineral-supplemented cows.
Clearly, trace mineral source can directly impact fertility parameters in successive generations, which is important when selecting and retaining heifers as part of the herd. Additionally, year-round supplementation through a high-quality trace mineral program can impact both the individual animal and her female offspring’s reproductive efficiency, as measured by her age at puberty, age at calving and lifetime performance.
Optimizing trace mineral status and reproductive efficiency is especially important in purebred herds and operations focusing on embryos. When looking at the follicular dynamics and embryo quality of beef cows, researchers have reported that supplementation with organic trace minerals (proteinates) resulted not only in the increased diameter of ovulatory follicles but also led to improved in vitro maturation and embryo cleavage. This is significant, as early embryo cleavage is a strong biological indicator of embryo potential and is often used as a measure of embryo quality.
Deciding on a proper supplementation program can thus have many practical and long-term implications, including:
- Organic trace minerals can potentially benefit reproductive performance via improved regulation of the estrus cycle, shorter calving intervals and improved implantation rates, as well as reproductive efficiency in successive generations.
- As such, when developing one’s own breeding cattle or acquiring replacement females, the emphasis should not only be on genetics; nutritional predisposition should also be taken into consideration.
- Given the potential return on investment associated with organic trace minerals in terms of health, reproductive efficiency and gains of cattle, year-round supplementation is not only economically feasible but could also have a direct impact on the future performance and profitability of the herd.
By producing more pounds of beef with the same number of cows or fewer, improvements in reproductive efficiency are also linked to sustainable (and economical!) beef production.
