Effects of varying sources of Cu, Zn, and Mn on mineral status and preferential intake of salt-based supplements by beef cows and calves and rainfall-induced metal loss

Association of rainfall pattern with the disappearance of mineral mixtures fed cattle managed on tropical pastures

The objective of the present study was to evaluate the association between rainfall and the disappearance of mineral mixtures in the supplementation of cattle on pasture. Supplement consumption and rainfall data were obtained from five experiments carried out between 2016 and 2022. The experiments lasted from 84 to 126 days and had 12 to 18 paddocks formed by Brachiaria spp. under grazing by beef cattle (n = 544), receiving mineral supplementation. Supplement disappearance (SD), difference between the amount offered and leftovers (considering intake and losses) and precipitation (PR), was measured over periods of 14 to 21 days. The periods (n = 565) were classified as very dry, dry, normal, rainy, and very rainy, using the Quantis method. The number of rainy days (RD) and the average precipitation per RD (APRD) per period and the average body weight (BW) of the animals in the periods were also determined. Linear regression analyses assessed the association between BW, PR, RD, and APRD. The average PR in the periods studied was 68.5 mm, ranging from 0.00 to 160.3 mm. Each period had up to six RD, with up to 129.5 mm precipitated. The average BW was 270 kg, ranging from 208 to 335 kg and the average SD was 82.2 g/animal/day, ranging from 0.52 to 176.7 g/animal/day. Differences in RD and APRD are consistent across precipitation classes. In the regression analysis, the model with the highest coefficient of determination was the one that contained the linear and quadratic terms for the RD variable. Including linear and quadratic terms of all variables in a multiple regression represented more than half of the variation in the disappearance of the supplement (R2 = 0.5823). There is no clear relationship between the intensity of precipitation, reflected in the form of classes, and the disappearance of supplements offered to cattle on pasture since dry and very rainy periods can be equivalent. However, variables that characterize the precipitation pattern are more relevant than animal live weight to explain existing variations in supplement disappearance. Among them, the frequency with which precipitation occurs (number of rainy days in the period) seems to be more important than the precipitation rate itself, probably because it is related to the volume of precipitation accumulated in the period.

Evaluation of Trace Mineral Sources

Several trace mineral sources, including inorganic, numerous organic, and hydroxychloride sources, are available for dietary supplementation or inclusion in a free-choice supplement. Inorganic forms of copper and manganese differ in their bioavailability. Although research results have been variable, organic and hydroxychloride trace minerals are generally considered more bioavailable than inorganic sources. Research indicates that fiber digestibility is lower in ruminants fed sulfate trace minerals compared with hydroxychloride and some organic sources. Compared with free-choice supplements, individual dosing with rumen boluses or injectable forms ensures that each animal receives the same quantity of a trace mineral.

Trace Mineral Supplementation of Beef Cattle in Pasture Environments

The United States Department of Agriculture defines pastureland as "A land cover/use category of land managed primarily for the production of introduced forage plants for livestock grazing." The purpose of this article is to review trace mineral supplementation for beef cattle in this environment. Supplementation of trace minerals in these environments is accomplished with the use of a trace mineralized salt or a complete mineral-vitamin product that contains macrominerals, trace minerals, and vitamins. The form of the supplement may influence uptake and utilization. Supplementation may be augmented with pulse dosing with injectables or oral products.

Trace Mineral Feeding and Assessment

Trace minerals are commonly supplemented in ruminant feeds as many common feeds are deficient in one or more of the trace minerals. The requirement of trace minerals needed to prevent classic nutrient deficiencies is well established, thus those cases most commonly occur when no supplement is provided. The more common challenge for the practitioner is to determine if additional supplementation is needed to enhance production or decrease disease occurrence.

Powder and agglomerated free-choice minerals for grazing cattle: animal responses and chemical and physical alterations of the mineral mixture

The aim was to evaluate the animal response and the chemical and physical changes of free-choice mineral mixtures fed to grazing cattle. Growing beef cattle were fed either powder (POW) or agglomerated (AGL) mineral mixtures in three different experiments (Exp.), carried out in pastures of Brachiaria grass. In Exp. 1 and 2, the mineral mixtures were disposed in unsheltered troughs (POWun vs. AGLun), being delivered once (D0, Exp.1) or twice (D0 and D8, Exp. 2), throughout 14-day periods. In Exp. 3, POWun and AGLun were additionally compared to POW in sheltered troughs (POWshe), and the mineral mixtures were disposed in D0, throughout 21-day periods. Non-consumed supplement was removed and sampled on D14 (Exp. 1 and 2) or D21 (Exp. 3). Evaluations included average daily body weight gain (ADG), daily disappearance of the supplement (DSD), penetration force of the supplement mass, faecal chemical composition and serum levels of Ca, P and Mg. In Exp. 1, no effects were observed on ADG and faecal mineral concentrations, however, changes in mineral concentrations and a 40% reduction in Na concentration in the supplement were observed, compared to the initial concentration. AGLun had a lower penetration force. In Exp. 2, there were no effects on DSD and faecal mineral concentrations. POWun showed a smaller reduction in Na content compared to AGLun, and AGLun showed lower penetration force. In Exp. 3, the treatments did not affect ADG, but there was a trend towards higher DSD and serum phosphorus (P) concentration for AGLun (p = 0.08). Higher faecal Na concentration was observed for AGLun and higher Na concentration occurred in non-consumed mixture of POWshe. Mineral supplements offered in uncovered troughs showed altered chemical and physical characteristics, with possible effects on supplement intake. However, the general changes are unlikely to alter animal performance.

Trace Mineral Nutrition of Grazing Beef Cattle

Simple Summary

The trace mineral nutrition of grazing beef cattle is an essential, but often complicated component of the management program. Throughout the annual cycle, forage is the primary source of trace mineral supply to grazing cattle, but concentrations vary depending on a multitude of factors. Trace mineral deficiencies are common when relying solely on forage to meet cattle requirements. Selenium, Cu, Zn, Mn, Co, and I are the trace minerals most commonly found to be deficient in forage. Trace mineral antagonists, such as Fe, Mo, and S, are commonly found in forage and exist in varying concentrations further complicating the success of satisfying the requirement of grazing cattle. Trace mineral-fortified, salt-based, free-choice supplements are the most common supplementation strategies available. Cattle voluntarily consume these supplements to satisfy their salt craving and thus indirectly receive supplemental trace minerals. Managing salt inclusion and seasonal variation in voluntary intake are essential to the success of this management system. Supplements can be formulated with a variety of trace mineral ingredients available to the industry, which are generally grouped into different source categories. Other supplementation strategies to supply trace minerals to grazing cattle include fortification of energy and protein supplements, biofortification, injectable trace minerals, and boluses.

Abstract

The trace mineral requirements of grazing beef cattle are often complicated by different environmental factors, such as the lack of specific trace minerals or the presence of trace mineral antagonists in forage. Nearly every region of the world has specific implications related to trace mineral nutrition of grazing cattle. Since forage is the most significant contributor to trace mineral nutrition, it is important to consider the concentrations of trace minerals and antagonists and how they may impact the performance of cattle consuming them. This review attempts to provide an update on the trace minerals commonly found to be inadequate in forage, supplementation strategies to address deficiency including a discussion on supplemental trace mineral source, and the complications presented by mineral antagonists. Although the review focuses on beef cattle grazing systems of the United States, the information herein is derived from both extensive native range and intensive planted pasture.