Effects of source of supplemental zinc on performance and humoral immunity in beef heifers1

Impact of an Injectable Trace Mineral Supplement on the Immune Response and Outcome of Mannheimia haemolytica Infection in Feedlot Cattle

The study aimed to assess the impact of injectable trace mineral ("ITM"; Multimin90; Fort Collins, CO) supplementation on bacterial infection in cattle. Angus-crossbred steers (n = 32) were organized into two blocks by initial body weight. Steers were maintained on a ryelage and dry-rolled corn-based growing diet without supplementation of Zn, Cu, Mn, and Se for the duration of the study. The steers were transported 6 h, then randomized into three treatment groups: control received sterile saline ("CON"), ITM administered 1 day after transport (6 days before infection, "ITMPRE"), and ITM administered 2 days post infection (dpi) concurrent with antibiotic treatment ("ITMPOST"). Steers were infected with Mannheimia haemolytica on day 0, and all were treated with tulathromycin at 2 dpi. Plasma levels of Zn, Cu, and Se did not differ among treatments (P ≥ 0.74). Liver Se was higher in ITMPRE at 2 dpi (P < 0.05), and both ITM groups had higher liver Se at 5 dpi (P < 0.05) compared to CON. A time × treatment interaction was detected for liver Cu (P = 0.02). Clinical scores were lower (P < 0.05) in ITMPRE on 1 and 8 dpi and ITMPOST on 8 dpi compared to CON. Thoracic ultrasonography scores were lower in ITMPRE at 2 dpi compared to CON (P < 0.05) and ITMPOST (P < 0.1). No treatment effects (P > 0.10) were observed for bacterial detection from bronchoalveolar lavage (BAL) or nasopharyngeal swabs. At 5 dpi, both ITMPRE and ITMPOST showed higher frequencies of γδ T cells and NK cells in BAL compared to CON (P < 0.05). Before infection, leukocytes from ITMPRE steers produced more IL-6 (P < 0.01) in response to stimulation with the TLR agonist, Pam3CSK4. Use of ITM may be an effective strategy for improving disease resistance in feedlot cattle facing health challenges.

Zinc about it - zinc and calf immunity

Micronutrients, such as vitamins and trace minerals, are critical for supporting growth, performance, health and maintaining redox balance. Zinc (Zn), an essential micronutrient, aids the functioning of innate and adaptive immune cells. This scoping review aims to assemble and evaluate the evidence available for the role of Zn within calf immunity. Relevant literature was identified within Web of Science, PubMed, and CABI using search terms specific to the major innate and adaptive immune cell populations. There was no evidence that Zn supplementation altered neutrophil, natural killer cell, or T-cell functions. However, there was limited evidence to support Zn supplementation with reduced monocyte numbers, but there was no evidence to associate the monocytopenia with improvements in monocyte function. There is moderate evidence to suggest that Zn supplementation was beneficial for maintaining epithelial barriers of integumental and mucosal surfaces. The evidence supports supplementation above the current industry recommendations for improving immunoglobulin (Ig) production, with the strongest results being observed for IgG and IgM. Moreover, Zn supplementation was associated with reduced proinflammatory cytokine production, which may reduce inflammation-associated hypophagia and warrants further investigation. Furthermore, Zn reduced the duration of clinical signs in animals facing respiratory disease and diarrhea. However, consensus is needed about the optimal dose, route, and Zn formulation most appropriate for supporting immunity. In conclusion, while the literature supports that Zn could enhance calf immunity, there is insufficient evidence to adequately determine the extent to which Zn impacts innate immune cell and T-cell functions. Determination of the immune cell functions susceptible to modification by Zn supplementation is an important knowledge gap for enhancing the understanding of Zn and calf immunity.

Vitamins and Trace Minerals in Ruminants: Confinement Feedlot

Trace minerals and vitamins are essential for optimizing feedlot cattle growth, health, and carcass characteristics. Understanding factors that influence trace mineral and vitamin absorption and metabolism is important when formulating feedlot cattle diets. Current feedlot industry supplementation practices typically exceed published trace mineral requirements by a factor of 2 to 4. Therefore, the intent of this review is to briefly discuss the functions of trace minerals and vitamins that are typically supplemented in feedlot diets and to examine the impact of dose of trace mineral or vitamin on growth performance, health, and carcass characteristics of feedlot cattle.

Trace Minerals Supplementation with Great Impact on Beef Cattle Immunity and Health

Simple Summary

Supplementation with trace minerals (TM) is a husbandry strategy to improve cattle health. There is solid evidence of the beneficial effects of TM supplementation on the immune system. The concentration of TM in the soil is variable across the USA, with several regions having deficient levels in forages. Therefore, TM supplementation is highly recommended especially in areas where forages do not supply the mineral requirements. Before starting TM supplementation, it is important to evaluate the herd’s mineral profile, and the amount of TM the animals are consuming. Oral free-choice TM may not be sufficient to satisfy the requirements in certain situations, and could lead to TM deficiencies. This is due to a high variability in TM composition and intake, binding to undigested feed particles, reduced absorption, and antagonisms. Single, oral pulse-dose supplementation provides a controlled and homogeneous amount of TM intended to remove such a variation. However, this strategy does not efficiently increase circulating and hepatic TM levels. Parenteral TM supplementation has resulted in a more efficient increase in TM concentration. The strategic supplementation combining injectable TM during critical times of cattle management (e.g., vaccination) in conjunction with oral free-choice supplements has shown significant benefits for the immune response and protection against respiratory disease in beef cattle, reducing morbidity and treatment costs.

Abstract

Trace minerals (TM) play an important role in cattle immunity, health and performance. Although TM are needed in small quantities, they are fundamental for enzymes involved in antioxidant protection against cellular damage and several pathways of the immune response. Cattle TM status results from the balance between TM dietary intake and their requirements. Free-choice oral TM supplementation is a common practice in beef cattle production systems. However, there is a high variation in TM intake and thus TM status and bioavailability in animals receiving free-choice oral TM supplements. Strategic pulse-dose supplementation during critical points of beef cattle management provides a controlled amount of TM intended to remove such a variation. Adequate TM supplementation should not only satisfy the basal requirements but also provide a source of TM when there is a higher demand of the antioxidant systems or during the development of the immune response. This paper reviews the research-based evidence of the effects of TM supplementation on immunity and its impact on beef cattle health. This review highlights the benefits of a novel approach of strategic administration of injectable trace minerals (Se, Zn, Cu and Mn) during critical episodes of cattle management (e.g., around weaning or at vaccination) in combination with free-choice oral supplementation to maintain adequate TM and oxidative status, enhanced immunity and overall cattle health. This strategy has proven to decrease morbidity, which would positively impact the productivity of the beef cattle systems.

Zinc supplementation strategies in feedlot heifers receiving an extended-release implant or an aggressive re-implant program

Two hundred eight Angus-crossbred heifers (291 ± 23 kg) from four sources were used in a randomized complete block design. The objective of the study was to determine the effects of implant strategy and Zn supplementation on performance, carcass characteristics, muscle fiber diameter, and mineral status of heifers. Heifers were assigned to a 2 × 2 factorial study for 168 d, and factors included Zn and implant (IMP). Heifers were supplemented Zn (mg/kg dry matter [DM]; ZnSO₄) at national (30; NRC) or industry (100; IND) recommendations. Implant strategies (Merck Animal Health, Madison, NJ) included extended-release Revalor-XH on day 0 (REV-XH; 20 mg estradiol + 200 mg trenbolone acetate) containing four uncoated pellets and six coated pellets or the uncoated implant Revalor-200 on day 0 and again on day 91 (REV-200; 20 mg estradiol + 200 mg trenbolone acetate). Heifers were blocked by weight within source to pens of five or six heifers per pen (nine pens per treatment). A corn silage-based diet was fed during the growing period (days 0–55) followed by transition to a corn-based finishing diet. Weights were taken consecutively on days −1/0, 55/56, and 167/168. Liver and muscle from the longissimus thoracis were collected from one heifer per pen on days −5, 14, 105, and 164. Data were analyzed via Mixed Procedure of SAS. Average daily gain (ADG) and liver mineral used Period as the repeated effect. Corresponding to periods of high hormone payout from each implant, days 0–28 and 91–120 ADG were greatest for REV-200, whereas REV-XH numerically peaked during days 56–91 (IMP × Period; P = 0.02). Day 91 IND body weight tended to be heavier (P = 0.06) and day 120 body weight was heavier (P = 0.05) than NRC heifers. No effect of Zn or IMP on final body weight was observed (P ≥ 0.21). Muscle fiber cross-sectional diameter on day 164 was greater (P = 0.05) in IND than NRC. Liver Mn concentrations decreased by day 14 regardless of implant, though days 105 and 164 concentrations were lesser for REV-200 than REV-XH (IMP × Period; P = 0.02). No effects of Zn, IMP, or the interaction were observed for carcass-adjusted gain to feed, days 0–168 DM intake, hot carcass weight, or ribeye area (P ≥ 0.11). The nominal differences in performance between implant strategies suggest that extended-release implants may be an effective implant strategy to replace re-implant programs in heifers, whereas the improved performance of heifers fed IND vs. NRC during times of peak hormone payout suggests a role for Zn in periods of rapid growth.

Nano zinc supplementation in goat (Capra hircus) ration improves immunity, serum zinc profile and IGF-1 hormones without affecting thyroid hormones

The trial was aimed at evaluating probable superiority, if any of nano zinc (NZn) over inorganic zinc (Zn) on immunity, serum minerals and T₃ , T₄ , and IGF-1 hormone profiles in goats. NZn was synthesized by using 0.45 M aqueous solution of Zn nitrate and 0.9 M aqueous solution of sodium hydroxide (average particle size 74 nm). Twenty-four male goats were grouped into four groups as per their body weight and were supplemented with either a basal diet with concentrate and straw at 50:50 ratio (Negative control, NC) alone or supplemented with 50 mg/kg Zn (Control) from inorganic Zn source, that is ZnO (IZn-50), 50 mg/kg Zn from NZn (NZn-50) or 25 mg/kg Zn from NZn (NZn-25). No change was observed in thyroid hormone status on zero and 90th day of experimental feeding, but NZn supplementation improved (p < 0.05) IGF-1 level on 90th day serum samples. Zn supplementation improved the humoral immunity in all the groups irrespective of the source. Similarly, cell-mediated immunity (CMI) measured by skinfold thickness after injecting Con-A, was also improved in Zn supplemented groups than control at 6, 12 and 48 h of incubation. NZn-50 animals showed highest HI (haemagglutination inhibition) titre as well as skin thickness. The CD 4 + (cluster of differentiation in %) was more (p < 0.05) in Zn supplemented groups. NZn-50 showed higher (p < 0.05) CD 8 + count than NC and similar (p > 0.05) to IZn-50 and NZn-25 groups without affecting (p > 0.05) the ratio of CD 4 + , CD 8 + among the treatment groups. Thus, NZn supplementation at 25 mg/kg had similar immunity and serum T₃ , T₄ and IGF-1 profiles compared with IZn at 50 mg/kg dose.

Assessment of Plasma Zinc and Total Leukocyte Count in Calves Experimentally Infected with Mannheimia haemolytica

Mannheimia haemolytica is the main bacterial pathogen isolated in bovine respiratory disease (BRD), a common disease affecting calves before weaning. Previous research has shown that experimental infection with bovine herpesvirus 1, a respiratory virus, decreases plasma zinc (Zn) levels. However, changes in plasma Zn concentrations in calves experimentally infected with M. haemolytica have not been studied thus far. The objective of this study was to evaluate the effect of experimental infection with M. haemolytica on plasma Zn concentration in calves. Total leukocyte count and bovine respiratory disease (BRD) clinical score were also evaluated. We conducted a 6-day trial in 14 male Holstein calves randomly assigned to one of two groups, experimental (EG, n = 8) and control (CG, n = 6). Animals in EG were intrabronchially inoculated with M. haemolytica (6.5 × 10⁶ CFU/mL) on day 0 of the trial. Plasma Zn levels were affected by time, treatment, and time by treatment interaction, being lower in EG compared with CG on days 1, 2, and 3. Differences in total leukocyte count were significant on day 1, observing a tendency on day 3. BRD clinical score differed between groups, being higher in EG throughout the trial. We conclude that experimental M. haemolytica infection reduced plasma Zn concentration in clinically ill calves, suggesting that the clinical condition of animals (healthy/ill) should be considered to better interpret plasma Zn values.

Effects of zinc propionate supplementation on growth performance, skeletal muscle fiber, and receptor characteristics in beef steers

A randomized complete block design experiment with 32 yearling crossbred steers (average body weight [BW] = 442 ± 17.0 kg) fed a steam-flaked corn-based diet was used to evaluate the effects of dietary Zn (KemTRACE Zn propionate 27; Kemin Industries, Inc., Des Moines, IA) supplementation on live growth performance, skeletal muscle fiber, and beta-adrenergic receptor (β-AR) characteristics during the finishing phase. Steers were blocked by BW (n = 4 blocks; 8 steers/block), assigned to pens (n = 4 steers/pen), and randomly assigned to the following treatments: control (CON; 0.0 g/[head (hd) · d] of additional Zn) or additional dietary Zn (ZnP; 1.0 g/[hd · d] additional Zn). The basal diet contained Zn (60 ppm dry matter basis) from ZnSO4; additional Zn was top-dressed at feeding. Ractopamine hydrochloride (RH; Optaflexx: Elanco Animal Health, Greenfield, IN) was included at 300 mg/(hd · d) for the final 28 d of the 111-d feeding period. Longissimus muscle biopsy samples, BW, and blood were obtained on days 0, 42, 79, and 107. Final BW was collected prior to shipping on day 111. Biopsy samples were used for immunohistochemical (IHC), mRNA, and protein analysis. Serum urea nitrogen (SUN) and nonesterified fatty acid (NEFA) concentrations were measured. Steers fed ZnP had a greater average daily gain (P = 0.02) and gain to feed ratio (G:F; P = 0.03) during the RH feeding period compared with CON. There were no differences (P > 0.05) in other growth performance variables, carcass traits, mRNA abundance, or relative protein concentration for fiber type and β-AR. Fiber types I and IIA had no differences in the cross-sectional area; however, the IIX area was greater for CON (P < 0.04) compared with ZnP and increased (P < 0.02) over time. There were no differences between treatments for the β1-AR density (P > 0.05) in skeletal muscle tissue throughout the study. A treatment × day interaction was observed in β2-AR density (P = 0.02) and β3-AR density (P = 0.02) during the RH feeding period, where the abundance of the receptors increased with ZnP but did not change in CON. Compared with CON, ZnP had greater (P < 0.01) mean NEFA concentrations. Mean SUN concentrations did increase by day (P < 0.01). Additional dietary Zn, supplied as Zn propionate, upregulates β2-AR and β3-AR and improves growth performance in feedlot steers during the RH feeding period, likely through a shift of resource utilization from lipogenesis to muscle maintenance and hypertrophy.

Effect of zinc source and concentration and chromium supplementation on performance and carcass characteristics in feedlot steers1,2,3

Four hundred crossbred steers were used in a randomized complete block design to investigate the effects of supplemental Zn source and concentration, and dietary Cr on performance and carcass characteristics of feedlot steers fed a steam-flaked corn-based finishing diet. Steers were blocked by initial BW within cattle source (3 sources) and randomly assigned within block to 1 of 5 treatments. Before the initiation of the experiment, trace mineral supplement sources were analyzed for Zn and Cr. Zinc and Cr concentrations of the Zn sources were used to balance all dietary treatments to obtain correct Zn and Cr experimental doses. Treatments were the addition of: 1) 90 mg Zn/kg DM from ZnSO4 and 0.25 mg Cr/kg DM from Cr propionate (90ZS+Cr); 2) 30 mg Zn/kg DM from Zn hydroxychloride and 0.25 mg Cr/kg DM from Cr propionate (30ZH+Cr); 3) 90 mg Zn/kg DM from Zn hydroxychloride and 0.25 mg Cr/kg DM from Cr propionate (90ZH+Cr); 4) 60 mg Zn/kg DM from ZnSO4 and 30 mg Zn/kg DM from Zn methionine (90ZSM); and 5) 90 mg Zn/kg DM from Zn hydroxychloride (90ZH). Steers were individually weighed on d-2 and on 2 consecutive days at the end of the experiment. Initial liver biopsies were obtained from all steers at processing. Equal numbers of pen replicates per treatment were slaughtered at a commercial abattoir on day 162, 176, and 211; individual carcass data and final liver samples were collected. Total finishing dietary Zn and Cr concentrations were 118.4, 58.2, 114.2, 123.0, and 108.2 mg Zn/kg DM and 0.740, 0.668, 0.763, 0.767, and 0.461 mg Cr/kg DM, for treatments 1 to 5, respectively. Data were analyzed statistically using preplanned single degree of freedom contrasts. Steers receiving 90ZH+Cr had greater final BW (P < 0.04) and ADG (P < 0.03) when compared with steers receiving 90ZH. Additionally, hot carcass weight was 8.5 kg greater (P < 0.03) for 90ZH+Cr compared with 90ZH supplemented steers. Steers receiving 90ZH+Cr had greater longissimus muscle area when compared with steers receiving 90ZSM. Dry matter intake, G:F, morbidity and mortality, and all other carcass measurements were similar across treatments. These data indicate that under the conditions of this experiment, Zn source and concentration had no impact on live performance, liver Zn and Cu concentrations, and carcass characteristics. Supplemental Cr in diets containing 90 mg of supplemental Zn/kg DM from ZH improved final BW, ADG, and hot carcass weights.

Effects of supplemental zinc sulfate on growth performance, carcass characteristics, and antimicrobial resistance in feedlot heifers

Effects of supplemental Zn as Zn sulfate on feedlot performance, carcass traits, and antimicrobial resistance were evaluated using 480 crossbred heifers (BW = 385 kg ± 13.08) in a randomized complete block design. Heifers were blocked by BW and randomly assigned within block to diets with 0, 30, 60, or 90 mg supplemental Zn/kg DM. Heifers were housed in dirt-surfaced pens (20 animals per pen; 6 pens per treatment) equipped with fence-line feed bunks and automatic water fountains. Heifers were fed once daily to ensure ad libitum intake. Plasma was collected on day 0 from five randomly selected heifers per pen and repeated on days 63 and 115 to determine plasma Zn concentrations. Random samples of freshly voided feces were collected from the surface of each pen the day of harvest to determine antibiotic resistance. Heifers were transported on day 144 to a commercial abattoir where hot carcass weight (HCW) and incidence of liver abscesses were recorded at harvest and HCW, dressed yield, ribeye area, 12th rib fat, quality and yield grades were recorded after 36 h of refrigeration. Plasma Zn concentration increased (P = 0.02) linearly in response to increasing concentrations of dietary Zn. Final BW and ADG were unaffected by supplementation (P ≥ 0.29). Quantified levels of resistance to ceftriaxone and tetracycline among fecal Escherichia coli were not impacted (P > 0.05) by dietary zinc concentrations. Increasing Zn concentrations tended to decrease (linear effect, P = 0.07) DMI, resulting in a linear (P = 0.03) and tendency for quadratic (P = 0.12) improvement in feed efficiency with increasing Zn concentration. No differences were detected for HCW, dressed yield, ribeye area, 12th rib fat, percentages of carcasses grading Select or Choice, or yield grade (P > 0.53), but added Zn tended to affect percentage of carcasses that graded Prime, peaking at 60 mg/kg added Zn (quadratic effect, P = 0.07). In vitro fermentations were performed using ruminal fluid cultures containing 0, 30, 60, 90, 120, or 150 mg Zn/kg substrate DM to determine impact of Zn on gas production, VFA concentrations, and in vitro DM disappearance (IVDMD). There were no effects of Zn on in vitro gas production, IVDMD, or most VFA (P > 0.15), but isovalerate decreased linearly in response to added Zn (P = 0.05). Supplementing finishing heifers up to 60 mg Zn/kg diet DM improved feed efficiency compared to other treatments.

Interaction between supplemental zinc oxide and zilpaterol hydrochloride on growth performance, carcass traits, and blood metabolites in feedlot steers

Interactive effects of supplemental Zn and zilpaterol hydrochloride (ZH) were evaluated in feedlot steers ( = 40; 652 kg ± 14 initial BW) to determine their impact on feedlot performance, blood constituents, and carcass traits. The study was conducted as a randomized complete block design with a 2 × 2 factorial treatment arrangement. Steers were blocked by BW and randomly assigned to treatments. Factors consisted of supplemental Zn (60 or 300 mg/kg diet DM) and ZH (0 or 8.33 mg/kg) in the diets. For diets supplemented with 300 mg Zn/kg DM, 60 mg Zn/kg was supplemented as zinc sulfate and 240 mg Zn/kg was supplemented as zinc oxide, and the diet was fed for 24 d. Zilpaterol hydrochloride was fed for 21 d followed by a 3-d withdrawal. Cattle were housed in partially covered individual feeding pens equipped with automatic waterers and fence-line feed bunks and were fed once daily for ad libitum intake. Plasma samples were collected on d 0 and 21 to assess changes in Zn, plasma urea nitrogen (PUN), glucose, and lactate concentrations, and serum samples were collected on d 21 to assess IGF-1 concentration. On d 25, cattle were weighed and transported 450 km to a commercial abattoir for harvest; HCW and incidence of liver abscesses were recorded. Carcass data were collected after 36 h of refrigeration. Data were analyzed as a mixed model with Zn, ZH, and Zn × ZH as fixed effects; block as a random effect; and steer as the experimental unit. No interaction or effects of Zn or ZH were observed for IGF-1 concentration, plasma glucose, or lactate concentrations ( ≥ 0.25). No interaction between Zn and ZH was observed for PUN concentration, but PUN decreased with ZH ( < 0.01). There were no effects of ZH or Zn on ADG, DMI, final BW, feed efficiency, HCW, back fat, KPH, quality grade, or incidence of liver abscesses ( > 0.05). Zinc supplementation tended ( = 0.08) to improve the proportion of carcasses grading USDA Choice. Feeding ZH decreased yield grade ( = 0.05) and tended to increase LM area ( = 0.07). In conclusion, increasing dietary concentrations of Zn does not impact response to ZH, but feeding ZH altered circulating concentrations of PUN.

Effects of sources and concentrations of zinc on growth performance, nutrient digestibility, and fur quality of growing-furring female mink (Mustela vison)

A completely randomized 3 × 3 + 1 factorial experiment was conducted to evaluate the effects of sources and concentrations of Zn on growth performance, nutrient digestibility, serum biochemical endpoints, and fur quality in growing-furring female black mink. One hundred fifty healthy 15-wk-old female mink were randomly allocated to 10 dietary treatments ( = 15/group) for a 60-d trial. Animals in the control group were fed a basal diet, which consisted of mainly corn, soybean oil, meat and bone meal, and fish meal, with no Zn supplementation. Mink in the other 9 treatments were fed the basal diet supplemented with Zn from either zinc sulfate (ZnSO), zinc glycinate (ZnGly), or Zn pectin oligosaccharides (ZnPOS) at concentrations of either 100, 300, or 900 mg Zn/kg DM. The results showed that mink in the ZnPOS groups had higher ADG than those in the ZnSO groups (main effect, < 0.05). The addition of Zn reduced the G:F ( < 0.05). In addition, CP and crude fat digestibility were linearly increased with Zn supplementation ( < 0.05) and N retention tended to increase with Zn addition ( = 0.08). Dietary Zn supplementation increased the concentration of serum albumin and activity of alkaline phosphatase ( < 0.05). There was a linear effect of dietary Zn on the concentration of tibia Zn and pancreatic Zn ( < 0.05). For fur quality characteristics, the fur density and hair color of mink were improved by dietary Zn concentration ( < 0.05). Compared with ZnSO (100%), relative bioavailability values of ZnGly were 115 and 118%, based on tibia and pancreatic Zn, respectively, and relative bioavailability values of ZnPOS were 152 and 142%, respectively. In conclusion, this study demonstrates that Zn supplementation can promote growth and increase nutrient digestibility and fur quality and that ZnPOS is more bioavailable than ZnSO and ZnGly in growing-furring female mink.

Interactive effects of supplemental Zn sulfate and ractopamine hydrochloride on growth performance, carcass traits, and plasma urea nitrogen in feedlot heifers

Interactive effects of supplemental Zn and ractopamine hydrochloride (RH) were evaluated using 156 crossbred heifers (initial BW = 527 kg ± 6.61; gross BW × 0.96) to determine the impact on feedlot performance, plasma urea nitrogen (PUN), and carcass characteristics. The study was conducted as a randomized complete block design with a 2 × 2 factorial arrangement of treatments. Factors consisted of 1) 30 or 100 mg supplemental Zn/kg diet DM (30Zn or 100Zn) as Zn sulfate and 2) 0 or 200 mg RH/heifer daily. Heifers were blocked by BW and assigned randomly within block to treatments for a 43-d trial. Heifers were housed in partially covered feeding pens (3 heifers/pen; 13 pens/treatment) and provided ad libitum access to feed. Ractopamine hydrochloride was fed for 42 d and removed from the diet until cattle were harvested on d 43. Zinc treatments were fed until harvest. Plasma samples were collected on d 0 and 36 to assess changes in plasma Zn and PUN. On d 43, heifers were weighed, then transported to a commercial abattoir where HCW and incidence of liver abscesses were recorded. Carcass data were collected after 32 h of refrigeration. No Zn × RH interactions were observed for plasma Zn or PUN ( ≥ 0.58); however, there was a tendency for a RH × day interaction for PUN ( = 0.08). Supplementing 100Zn resulted in increased plasma Zn ( = 0.02) compared to 30Zn. No RH × Zn interactions were observed for feedlot performance ( ≥ 0.24). Final BW and ADG increased with RH supplementation ( ≤ 0.02), but DMI was not affected ( = 0.63); thus, feed efficiency improved ( < 0.01) when heifers were fed RH. Supplementing 100Zn tended to reduce ADG ( = 0.07) but did not affect other measures of feedlot performance ( ≥ 0.12). Zinc × RH interactions were observed for LM area and yield grade ( ≤ 0.01); LM area decreased and yield grade increased when heifers were supplemented 100Zn with no RH compared to other treatments. A tendency for a Zn × RH interaction was observed for dressed yield ( = 0.08), but no other interactions or effects of Zn were detected for carcass traits ( ≥ 0.11). Supplementing RH increased HCW ( = 0.03) but did not affect other carcass traits ( ≥ 0.13). In conclusion, supplemental Zn had little impact on feedlot performance or PUN concentration but may alter muscle and fat deposition when fed in conjunction with RH.

BILL E. KUNKLE INTERDISCIPLINARY BEEF SYMPOSIUM: Impact of mineral and vitamin status on beef cattle immune function and health

The importance of optimal mineral and vitamin nutrition on improving immune function and health has been recognized in the preceding decades. In the southeast, beef cattle are raised predominantly on forages that may be limiting in nutrients for optimal health, especially trace minerals such as Cu, Zn, and Se. Clinical deficiencies of these nutrients produce classic symptoms that are common to several nutrient deficiencies (e.g., slow growth and unthrifty appearance); however, subclinical deficiencies are more widespread and more difficult to detect, yet may result in broader economic losses. Dietary mineral concentrations often considered adequate for maximum growth, reproductive performance, or optimal immune function have been found to be insufficient at times of physiological stress (weaning, transport, comingling, etc.), when feed intake is reduced. The impacts of these deficiencies on beef cattle health are not apparent until calves have been subjected to these stressors. Health problems that are exacerbated by mineral or vitamin deficiencies include bovine respiratory disease, footrot, retained placenta, metritis, and mastitis. Many micronutrients have antioxidant properties through being components of enzymes and proteins that benefit animal health. In dairy cattle, high levels of supplemental Zn are generally associated with reduced somatic cell counts and improved foot health, possibly reflecting the importance of Zn in maintaining effective epithelial barriers. Neutrophils isolated from ruminants deficient in Cu or Se have reduced ability to kill ingested bacteria in vitro. Supplemental vitamin E, in its role as an intracellular antioxidant has been shown to decrease morbidity in stressed calves. There is more understanding of the important biological role that these nutrients play in the functioning of the complex and multifaceted immune system. However, there is still much to be learned about determining the micronutrient status of herds (and hence when supplementation will be beneficial), requirements for different genetic and environmental conditions, understanding the bioavailability of these nutrients from feedstuffs and forages, quantifying the bioavailability of different supplemental sources of these nutrients, and identifying the impact of dietary antagonists on these nutrients.

Effects of zilpaterol hydrochloride and zinc methionine on growth performance and carcass characteristics of beef bulls

Rodríguez-Gaxiola, M. A., Domínguez-Vara, I. A., Barajas-Cruz, R., Mariezcurrema-Berasain, M. A., Bórquez-Gastelum, J. L. and Cervantes-Pacheco, B. J. 2015. Effects of zilpaterol hydrochloride and zinc methionine on growth performance and carcass characteristics of beef bulls. Can. J. Anim. Sci. 95: 609–615. Sixty beef bulls with a body weight (BW) of 314.7±16.2 kg were used to evaluate the effects of zilpaterol hydrochloride (ZH) and zinc methionine (ZM) on growth performance and carcass characteristics. The experimental design was a randomized complete block, with a factorial 2×2 arrangement of treatments (ZH: 0 and 0.15 mg kg−1 BW; ZM: 0 and 80 mg kg−1 dry matter). The ZH increased (P<0.05) the final BW, average daily gain, feed conversion, carcass yield and longissimus dorsi area. Bulls fed ZH plus ZM had less (P<0.01) backfat thickness and intramuscular fat (IMF) compared with those fed ZH or ZM alone. The ZH increased (P<0.02) the meat crude protein content and cooking loss. It is therefore concluded that ZH increases growth performance, carcass yield, longissimus dorsi area, and meat crude protein. The interaction of ZM and ZH did not present additional advantages. The reason for the reduction in backfat thickness and IMF by ZH plus ZM is unclear, and implies that our knowledge of β-agonistic adrenergic substances and their interactions with minerals is incomplete.

Effect of zinc source on performance, zinc status, immune response, and rumen fermentation of lactating cows

Two experiments were conducted to examine the effect of zinc (Zn) source on the performance, Zn status, immune response, and rumen fermentation of lactating cows to find the most available Zn source for dairy production. In Experiment 1, a total of 30 multiparous Holstein cows were randomly allocated by body weight and milk yield to one of five treatments in a completely randomized design. Cows were fed a total mixed ration (TMR) with no Zn addition (containing 37.60 mg Zn/kg TMR by analysis), and the basal TMR supplemented with 40 mg Zn/kg TMR from either Zn sulfate or one of three organic Zn chelates with weak (Zn-AA W), moderate (Zn-Pro M), or strong (Zn-Pro S) chelation strengths, respectively for 55 days. In Experiment 2, the in vitro rumen fermentation method was used in a completely randomized design involving a 4 × 3 factorial arrangement of treatments. The four Zn sources were the same as those used in Experiment 1, and the three supplemental Zn levels in the rumen fluid were 0, 10, and 20 μg/mL, respectively. The feed intake, milk composition, and somatic cell count (SCC) were unaffected (P > 0.05) by treatments. However, the milk yield was increased (P < 0.05) by addition of Zn from both the Zn-AA W and Zn-Pro S. Plasma Zn level at the end of the experiment was increased (P < 0.05) by addition of Zn from all three organic sources. Serum antibody titers on day 21 after vaccination with foot and mouth disease (FMD) vaccine were increased (P < 0.05) by both supplemental Zn-AA W and Zn-Pro S. The organic Zn sources with different chelation strengths supplemented at the added Zn level of 10 μg/mL were more effective (P < 0.05) in improving the rumen fermentation than Zn sulfate, with the most effective being Zn-AA W. In conclusion, Zn source had no influence on the feed intake, milk composition, and SCC; however, both the Zn-AA W and Zn-Pro S were more effective than Zn-Pro M and Zn sulfate in enhancing the rumen fermentation, Zn status, and humoral immune response as well as improving milk yield of lactating cows. The improved milk production might be attributed to the improved rumen fermentation, Zn status, and immune function.

Assessment of reference values for copper and zinc in blood serum of first and second lactating dairy cows

The influence of different copper and zinc contents in rations on blood serum concentrations in dependence on feeding (Groups A and B) and lactation (Lactation 1 and 2) was tested in a feeding trial with 60 German Holstein cows. All animals received a diet based on maize and grass silage ad libitum. 30 cows received a concentrate supplemented with copper and zinc as recommended (Group A), whereas the other 30 animals were offered a concentrate with roughly double the amount of copper and zinc (Group B). Blood samples were taken several times during the lactation to analyse serum concentrations of copper and zinc. Copper serum concentration was influenced neither by the different feeding (11.7 μmol/L in Group A and 12.3 μmol/L in Group B) nor by the lactation (12.0 μmol/L in Lactation 1 and 12.1 μmol/L in Lactation 2). Zinc serum concentration was significantly influenced as well as by feeding (14.1 μmol/L in Group B and 12.5 μmol/L in Group A) and lactation (14.2 μmol/L in the second lactation and 12.8 μmol/L for first lactating cows). For an exact diagnosis of trace element supply, blood serum is a not qualified indicator; other sources (feedstuffs, liver, hair) must also be investigated.

Effect of dose and source of supplemental zinc on immune response and oxidative enzymes in lambs

An experiment of 150 days was conducted on 42 male Nellore lambs (28.3 +/- 0.64 kg) to determine the effect of zinc (Zn) supplementation (0,15, 30 and 45 ppm) in diet from inorganic (ZnSO(4)) and organic (Zn proteinate) sources on immune response and antioxidant enzyme activities by allotting them randomly to 7 groups in completely randomized design. The basal diet (BD) contained 29.28 ppm Zn. The humoral immune response assessed at 75 d against B. abortus was higher (P<0.01) with 15 or 30 ppm Zn supplementation from organic source. The dose and source had no effect on titres against chicken RBC antigen. The cell mediated immune response assessed as delayed type hypersensitivity (DTH) response against phytohaemagglutinin-P and in vitro lymphocyte proliferative response against concanavalin A at 150 d was higher (P<0.05) at 15 ppm Zn supplementation compared to BD fed lambs. Supplementation of 45 ppm Zn had no positive effect on immune response. The DTH response and antibody titres against B.abortus were higher (P< 0.05) on Zn proteinate compared to ZnSO(4) at 15 ppm Zn supplementation. The lipid peroxidase activity was lower (P < 0.01), while the RBC superoxide dismutase and catalase activities were higher (P < 0.01) in lambs at 15 ppm Zn supplementation compared to BD diet fed lambs, assessed at 75 d of feeding. Serum globulin concentration and alkaline phosphatase (ALP) activity (75 d of experiment) was higher in Zn supplemented lambs. The ALP activity increased (P < 0.01) with increase in Zn supplementation and being higher when supplementation was from Zn proteinate compared to ZnSO(4). The study indicated that 15 ppm zinc supplementation was required for obtaining higher immune response in lambs when fed a basal diet containing 29.28 ppm Zn and supplementation as Zn proteinate had higher antioxidant enzyme activities and immune response compared to ZnSO(4).