Supplementing trace minerals can benefit cattle health, reproduction and growth, but it takes the right minerals at the right times, along with considerations for toxicity and antagonisms from minerals already in the diet. And while mineral supplementation is not a new tool, researchers continue to refine the practice for optimum results. These efforts become increasingly important as consumer and regulatory pressures grow to end the use of antimicrobials for growth promotion and further limit their use for prevention of disease.
Veterinarians in beef practice potentially can help cow-calf, stocker and feedyard clients adopt mineral programs that pay at each production stage. Ideally, a mineral program begins with the cow, both for her nutritional status and for that of her calf.
Most beef cows probably could benefit from some mineral supplementation year-around. Recent research indicates though, that the right supplement program, focused on the third trimester of gestation, could produce long-term, in fact lifetime benefits to the developing calves.
Several studies have shown that cow nutrition during the final trimester can affect calf performance, and others have demonstrated that trace minerals are essential for fetal development.
North Dakota State University animal scientist Kim Vonnahme, Ph.D., has conducted a variety of studies into developmental programming in cattle and sheep, looking at the effects of dietary restrictions at different stages of gestation. While early placental development is important in the overall development of the fetus, Vonnahme says her research has shown the cow can compensate better than earlier believed during early gestation, maintaining blood and nutrient flow to the placenta even when her diet is restricted.
Research indicates that during mid to late gestation, when the fetus experiences rapid growth, restrictions in the cow’s nutrient status or other stressors could have more profound effects on long-term calf performance. Vonnahme also notes that while placental growth slows during the last half of gestation, placental function increases dramatically, with uterine blood flow increasing approximately three- to four-fold to support the exponential rate of fetal growth.
Minerals at the right time
Researchers at Oregon State University recently conducted a trial to determine whether supplementing copper (Cu), manganese (Mn), zinc (Zn) and cobalt (Co) to late-gestating cows will result in increased postnatal offspring productivity. They also examined whether organic-complexed sources of those key minerals might transfer to the gestating calf more efficiently than inorganic sources.
Oregon State University animal scientist Reinaldo Cooke, Ph.D., participated in the study, results of which are published in the Journal of Animal Science.
Cooke and his team designed the study to mimic typical production systems in Western rangeland environments. For many ranchers, providing supplements is difficult during the summer months when cows are spread across extensive acreage. Later in gestation, ranchers gather the cows into close-in pastures in preparation for calving season, providing a good opportunity to supply them with supplements. It turns out that, in addition to being convenient, trace-mineral supplementation during the third trimester provides significant benefits to the developing fetus and the dam.
The study used 84 pregnant cows, sorted into three treatment groups:
· Control: no supplemental zinc, manganese, copper or cobalt
· Inorganic: diet supplemented with inorganic zinc, manganese, copper and cobalt
· Organic supplement: diet supplemented with 7 grams per head per day of Availa®4, a combination of complexed zinc, manganese, copper and cobalt from Zinpro Corporation
The trace-mineral levels between inorganic and organic treatments were equivalent for each mineral, so only the source of trace mineral differed between the two treatments. The researchers note that the control diet met minimum standard requirements for Cu, Co, Mn, and Zn, whereas the inorganic and organic supplement diets provided nearly 200% of NRC requirements for Zn, Cu, and Mn and over 2,000% of NRC requirements for Co. “Therefore, results from this experiment should not be associated with trace mineral deficiency in the control diet but with potential fetal programming effects of additional Cu, Co, Mn, and Zn intake by supplemented cows.” The study results highlight a concept called Generational Nutrition®, says Jason Russell, a Ph.D. nutritionist with Zinpro.
The researchers fed the three diets through the third trimester until calving. After calving, all the cows and calves were treated the same with inorganic trace mineral supplements.
At the initial tests, as the cows came off rangeland grazing at the end of their second trimester of gestation, none were deficient for the four critical trace minerals. Prior to calving, the researchers collected liver biopsies from cows and at calving collected liver samples from calves and samples from placentas.
In the cows prior to calving, liver cobalt concentrations were slightly higher in cows consuming the organic supplements, copper levels higher in cows receiving inorganic sources, manganese levels similar in both groups and zinc higher in cows receiving inorganic minerals. In the placenta samples, cows receiving the organic sources were somewhat higher for all four minerals. Cooke notes inorganic and organic sources improved trace-mineral status of cows versus controls, but the organic forms (from Availa-4) seemed to transfer better to the calves.
Weaning weights averaged 519 pounds for calves from cows receiving the organic supplement versus 491 pounds for those from the group receiving the inorganic minerals. The calves from the organic-mineral group had a $70 per head advantage over controls at weaning while the inorganic-mineral group had a $32 per head advantage. The control groups, Cooke notes again, were not considered mineral deficient.
Reduction in BRD
The researchers sent the calves to a grow lot following weaning and then to a finishing lot. During the growing period, 42% of the control calves required bovine respiratory disease (BRD) treatment, compared with 59% of calves from inorganic-supplemented cows and 20% of calves from cows receiving organic mineral supplements. The relative weight advantages between treatments were maintained throughout the feedlot phase and post-harvest. The researchers concluded that the organic formulation of mineral supplements in cows decreased BRD in their calves during the critical receiving period.
Russell explained that all calves in the study population were fed for harvest and therefore, it was not possible to measure differences in fertility among replacement heifers. However, heavier heifer weaning weights in the organic-supplement group, which carried over through finishing, suggest supplementation of the gestating dam could result in heifers expressing puberty earlier and conceiving earlier during their first breeding season.
Stress amplifies demand for trace-mineral nutrition, Russell says. Supplements during the receiving phase at feedyards can improve calf health and performance, but ideally, calves should have adequate stores of mineral nutrients prior to weaning and shipping.
Maybe, Cooke says, cow-calf producers should provide more trace minerals to cows than currently believed. He adds that supplementation during the first and second trimester probably would improve calf performance further, but the Oregon trial focused on supplementing during the third trimester due to the extensive range-production environment for early gestation cows and its limits on controlling mineral intake.
Russell notes there are several key times for mineral supplementation, including prior to calving for fetal development and prior to breeding for optimum cow fertility. In this trial, the cows were supplemented during the final 94 days of gestation. Adding another 90 days to carry cows through breeding would mean a total of about six months of supplementation. Where possible, Russell says producers might consider supplementing cows with Availa-4 year-around.
The additional cost for the Availa-4 supplement used in this trial, Russell says, is about 2.5 cents per head per day, or just over $9 per head for year-around supplementation. At that cost, he notes, six to seven pounds of extra weaning weight per calf would pay for the supplement. In this trial, calves in the organic-supplement group averaged 53 pounds heavier than control calves at weaning and 28 pounds more than calves born to cows supplemented with inorganic trace minerals. So, the program can easily pay for itself at the cow-calf level while providing additional health and performance benefits through the growing and finishing stages. Russell emphasized that when evaluating trace mineral supplement options, it is important to ensure health and performance claims are validated by peer-reviewed research and generate a return on investment for producers.