Studies suggest there are differences in corn vs. molasses supplements on trace mineral status. Two experiments were conducted to compare the availability of trace minerals offered to Brahman-crossbred heifers in either grain- or molasses-based supplements. Heifers were grazing bahiagrass pastures.

The study results suggest components in molasses-based supplements decreased the accumulation of copper (Cu) in the liver of beef heifers. The sulfur (S) and molybdenum (Mo) components of molasses may be responsible, at least in part, for this antagonism.

Experiment 1: Two supplements were formulated using corn and cottonseed meal or molasses and cottonseed meal.

Experiment 2: A third treatment consisted of corn and cottonseed meal with additional S to equal the amount naturally supplied by the molasses and cottonseed meal.

  • No differences were detected in heifer body weight change in Experiments 1 and 2.

  • In both experiments, liver iron (Fe), manganese (Mn) and zinc (Zn) concentrations were not affected by supplement treatments.

  • Molybdenum tended to accumulate in the liver of heifers fed molasses and cottonseed meal.

  • In Experiment 1, Cu accumulation was less in the heifers fed molasses and cottonseed meal.

In Experiment 2, heifers receiving Cu from corn and cottonseed meal had higher liver Cu levels than heifers fed molasses and cottonseed meal and the corn and cottonseed meal with additional S.

Hartington and Pate, University of Florida.

The most important determinants of beef carcass value are external fat content and intramuscular (IM) fat deposits (marbling). External fat lowers value while marbling increases value.

The previous assumption was that external fat was necessary as evidence that marbling was present. The reality is that there is a very weak relationship between these variables. We are also learning that the prediction tool of expected progeny difference (EPD) might be useful for identifying cattle that will produce lean carcasses with ample marbling.

Before commercial cattle feeders can take advantage of this potentially valuable knowledge, more must be learned about when and how marbling develops.

To do this, South Dakota researchers have identified high and low marbling EPD progeny groups of known age and parentage. These steers are being fed high grain diets typically used in feedlots. Subjects will be harvested when weighing 700, 850, 1,000, 1,150 and 1,300 lbs.

IM fat cell development and metabolism and body composition will be studied at each growth stage. The data will be used to help feeders optimize diets, implant strategies and market weights of cattle.

South Dakota State University research project - KB9660.

Zinc source may impact performance, immune response and carcass characteristics of growing and finishing steers. Sixty Angus and Angus x Hereford steers were used to determine the effect of zinc level and source. Treatments consisted of controls, ZnO, Zinc proteinate-A and ZnProt-B.

  • Performance and carcass measurements were similar in steers fed the two ZnProt sources.

  • Zinc supplementation, regardless of source, increased average daily gain (ADG) during the growing phase.

  • In the finishing phase, ADG and gain/feed tended to be higher for steers fed ZnProt compared with those supplemented with ZnO.

  • Gain and feed efficiency were similar for control and ZnO-supplemented steers during the finishing phase.

  • Steers fed ZnProt had heavier hot carcass weights and slightly higher dressing percentages than those in the control or ZnO treatments.

  • Quality grade, yield grade, marbling and backfat were increased by Zn supplementation but were not affected by Zn source.

  • Humoral immune response following vaccination with infectious bovine rhinotracheitis also was not affected by treatment.

Spears and Kegley, North Carolina State University.