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Effects of supplemental zinc source and level on finishing performance, health, and carcass characteristics of beef feedlot steers
Applied Animal Science 35:379–387 https://doi.org/10.15232/aas.2019-01854 © 2019 American Registry of Professional Animal Scientists. All rights reserved.
NUTRITION: Original Research
Effects of supplemental zinc source and level on finishing performance, health, and carcass characteristics of beef feedlot steers J. S. Heldt1* PAS, and M. S. Davis,2 PAS 1 Micronutrients USA LLC, Indianapolis, IN 46231-3350; and 2Bos Technica Research Services, Salina, KS 674018458
ABSTRACT
INTRODUCTION
Objective: Our objective was to compare the effects of supplemental Zn sources and levels on health, growth, and carcass characteristics in finishing steers. Materials and Methods: Crossbred steer calves (n = 1,502; initial BW = 297 ± 5 kg) were housed in 24 pens with 8 pens per treatment in a randomized complete block design. Treatments (100% DM) consisted of the following: (1) control: 10.6 mg/kg of Cu [72.2% Cu sulfate/27.8% Cu AA complex (AAC)], 37.8 mg/kg of Zn (77.6% Zn sulfate/22.4% Zn AAC), and 25.5 mg/kg of Mn (81.6% Mn sulfate/18.4% Mn AAC); (2) combination: 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate/33% Zn methionine), and 20 mg/kg of Mn (75% Mn sulfate/25% Mn hydroxychloride); and (3) hydroxy: 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate/25% Mn hydroxychloride). Results and Discussion: There were no significant differences in DMI, ADG, final BW, F:G, morbidity, or mortality (P ≥ 0.28). Hot carcass weight, DP, and backfat were also unaffected (P ≥ 0.32) by treatment. Increased level of Zn tended (P = 0.13) to increase marbling score. There was a tendency for combination to have a larger LM area (P = 0.14) and lower YG (P = 0.10) compared with hydroxy. Implications and Applications: Steers fed a lower level of Zn sulfate/AAC had similar performance compared with steers fed a higher level of Zn. Zinc hydroxychloride is equally effective as a Zn sulfate/Zn methionine combination when fed at 90 mg/kg.
Supplemental trace mineral (TM) programs for feedlot diets are designed to meet the animals’ nutrient requirements and provide a safety factor to account for any potential antagonists found in the basal feedstuffs or water supply. This can be approached by simply increasing the supplemental amount, altering the TM source, or both. In a 2007 survey of consulting nutritionists, the modes for levels of supplemental Cu, Zn, and Mn were 2 to 3 times greater than the NRC (2000) requirement (Vasconcelos and Galyean, 2007). In a 2016 follow-up survey, 54.6% of consulting nutritionists indicated a preference for a combination of organic and inorganic sources, 45.4% indicated a preference for only organic sources in finishing diets, and the mode for levels was identical to the previous survey (Samuelson et al., 2016). This indicates that consulting nutritionists currently do not follow NRC recommendations and see value in feeding nonsulfate forms of TM to meet their nutritional goals. Inorganic TM sources are generally supplied in the sulfate form. Sulfate trace minerals are a single metal ion associated with a single sulfate ion through an ionic bond. However, a new category of inorganic trace minerals, hydroxy trace minerals, has been developed. Basic Cu chloride, Zn hydroxychloride, and Mn hydroxychloride are crystalline mineral sources formed by covalent bonds between the metal, chloride, and hydroxyl groups (Leisure et al., 2014). Organic trace minerals are molecules where the metal ion is covalently bound to a carbon-containing molecule. The carbon source can be from a carbohydrate, hydrolyzed protein, or a single AA. Many different sources of organic TM, inorganic TM, and subsequent combinations have been studied in feedlot cattle, and results have been variable (Rhoads et al., 2003; Ahola et al., 2005; Berrett et al., 2015; Caldera et al., 2016; Wagner et al., 2016). The variable results indicate the need to further investigate TM supplementation in the feedlot industry to help increase the breadth of knowledge to support one source or combination of sources over the other and to better define optimal levels within the currently used sources. The decision to use different sources and levels of Zn should be
Key words: finishing, zinc, hydroxychloride, organic trace mineral
One of the authors works for Micronutrients USA LLC, Indianapolis, Indiana, which provided funding. The authors declare no conflict of interest. *Corresponding author: jeff.heldt@micro.net
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based on scientific evidence for performance outcomes and economics. Therefore, the objective of this study was to compare the effects of Zn source and level on performance, health, and carcass characteristics in steers fed diets based on steam-flaked corn in a commercial feedlot setting.
MATERIALS AND METHODS Cattle Processing and Allotment Procedures This study was conducted at a commercial facility in a manner consistent with applicable laws and regulations governing the humane care of animals. Steers were observed at least once daily to ensure animals were healthy, and if any abnormality was detected, prompt and adequate treatment was performed by trained and qualified personnel. A total of 1,707 cross-bred steers (initial BW of 297 ± 5 kg) sourced from ranches and livestock auctions in Oklahoma, Texas, and Missouri were used in a randomized complete block designed study conducted at a commercial research facility near Watonga, Oklahoma (Bos Technica Research Services) from October 2017 to May 2018 (days on feed across blocks averaged 204 d). Steers originated from 21 sources and arrived at the research site between October 4 and 14, 2017, where they remained segregated by day of arrival and source until adequate numbers arrived to meet the head-count requirement for one block. Each block consisted of 3 pens randomly assigned to 1 of 3 treatments. Before pen assignment, any animals that were injured, exhibited clinical signs of disease, were bulls, or were exhibiting phenotypic characteristics of Brahman influence were sorted from the pool of steers available for study enrollment and were not included in the study. Within an arrival day and source, steers were assigned randomly no more than 8 head at a time to 1 of 3 pens in a block before initial processing. There was a total of 8 blocks of cattle. The trial was initiated with 1,502 steers that met the trial criteria. Immediately following randomization, steers were taken by pen to a 21.3-m platform scale (Fairbanks, TRBT88, Kansas City, MO) and weighed in one draft. The platform weight served as initial starting weight for each pen, and the scale was balanced between each pen. Initial processing occurred immediately after obtaining pen weights. Each steers was vaccinated against viral (Pyramid 5 + Presponse, Boehringer Ingelheim Vetmedica Inc., St. Joseph, MO) and clostridial (Vision 7, Merck Animal Health, Summit, NJ) diseases and treated for internal parasites with doramectin (Dectomax Injectable Solution, Zoetis Inc., Parsippany, NJ) and fenbendazole (Safe-Guard, Merck Animal Health). Steers were also administered a metaphylaxis dose of tuluthromycin (Draxxin, Zoetis Inc.). Each steer was implanted in the right ear with Revalor-XS (120 mg of trenbolone acetate and 24 mg of estradiol, Merck Animal Health) and not reimplanted before slaughter. A visual tag containing
lot number and an individual identification number was placed in the left ear, providing dual identification. Cattle were housed in 24 nonshaded 21.3 × 73.2 m open dirt pens (71 steers per pen) with individual continuous-flow water tanks (0.12 linear meters per steer) and fence-line feed bunks (0.28 linear meters per steer). Following initial processing, trained pen riders were instructed to observe a 10-d post-metaphylaxis interval for all pens. During this 10-d period, all pens were ridden, but no steers could be pulled for respiratory disease.
Treatments Treatments, expressed on a 100% DM basis, consisted of (1) control (CON): 10.6 mg/kg of Cu [72.2% Cu sulfate and 27.8% Cu AA complex (AAC); Availa Cu, Zinpro Corporation, Eden Prairie, MN], 37.8 mg/kg of Zn (77.6% Zn sulfate and 22.4% Zn AAC; Availa Zn, Zinpro Corporation), and 25.5 mg/kg of Mn (81.6% Mn sulfate and 18.4% Mn AAC; Availa Mn, Zinpro Corporation); (2) combination (COMBO): 10 mg/kg of Cu (100% basic copper chloride; IntelliBond C, Micronutrients USA LLC, Indianapolis, IN), 90 mg/kg of Zn (67% Zn sulfate and 33% Zn methionine; ZINPRO 120, Zinpro Corporation), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride; IntelliBond M, Micronutrients USA LLC); (3) hydroxy trace minerals (HYD): 10 mg/kg of Cu (100% basic copper chloride; IntelliBond C), 90 mg/kg of Zn (100% Zn hydroxychloride; IntelliBond Z, Micronutrients USA LLC), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride; IntelliBond M, Micronutrients USA LLC). Treatment design was based largely on the most recent feedlot nutritionist survey where 81.9% of survey respondents reported that they give zero or only partial credit to basal feedstuffs for TM values, along with 77.3 and 54.6% of respondents who indicated a preference for a combination of TM sources to be used in receiving and finishing diets, respectively (Samuelson et al., 2016). Additionally, this survey reported that the mean added Zn level in receiving and finishing diets was 109 mg/kg and 87.3 mg/kg, respectively (Samuelson et al., 2016). This published information combined with limited large pen field trials evaluating the effectiveness of hydroxychloride sources of TM in finishing diets were all factored in to development of experimental treatments. Furthermore, the authors recognize that the amounts of the different organic sources may be inconsistent with manufacturer recommendations. However, the amounts used in this study are consistent with field observations of current industry practices and personal communications with industry professionals where these products are used. In addition, Co (Co carbonate), I (ethylenediamine dihydroiodide), and Se (sodium selenate) supplemental concentrations were 0.1, 1.4, and 0.14 mg/kg of DM, respectively. Trace mineral treatments were administered through a dry, loose meal premix.
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Rations Rations were formulated to meet or exceed NRC (2000) requirements, and composition is shown in Table 1. Each pen was provided feed thrice daily using a single-axle truck equipped with a mixer-delivery box (Harsh 430H, Eaton, CO). All rations and water were provided to allow for ad libitum consumption. Feed amounts delivered to each pen were recorded manually by the feed-truck driver and electronically by the feed-truck scale system, and the delivery amount was printed at the time of feeding. Bunks were managed by a clean-bunk system, so the amount of feed provided daily was adjusted so bunks contained little to no orts after 24 h. On occasion, when feed remained in the bunk before the first feeding [e.g., inclement weather (i.e., rain or snow) or at the discretion of the site manager], it was removed, weighed, and sampled for DM using a laboratory convection oven on site. An adjustment of daily intake was made on a DM basis. Total feed intake per pen was calculated on a DM basis as the amount of feed offered minus the weighed-back portion of the feed. Daily feed intake was then calculated as total feed intake divided by total animal days, where total animal days was equal to the number of days each steer was in its home pen from start to finish of the study, totaled for each pen. Steers were adjusted to final finisher ration using a series of step-up rations (Table 1). Ration 2 was fed for 27 to 32 d depending on block, and ration 3 was fed for 14 d for all blocks. During the first 30 d on feed, a portion (1% of BW as fed) of ration 2 was replaced with ration chlortetracycline. The ration chlortetracycline was fed so cattle would receive 1 g of chlortetracycline (Aureomycin 90, Zoetis) per 45.4 kg of BW during the first 5 consecutive days of each of the first 4 wk of the study. During the step-up period, an additional 360 mg of Zn from Zn methionine was added to the ration provided to the CON steers. Steers were adjusted to the finishing diet within 7 wk after arrival. Commencing 30 d before slaughter, ractopamine hydrochloride (Actogain 45, Zoetis Inc.) was fed to supply 300 mg of ractopamine hydrochloride per steer per day. On the day before slaughter, steers were provided 80% of the previous 5-d ADFI (as-fed basis). Lasalocid sodium (Bovatec 90, Zoetis Inc.) was included in ration 2 at a concentration of 33 g/909 kg (DM). Monensin sodium (Rumensin 90, Elanco Animal Health, Greenfield, IN) was included in rations 3 and 4 at a concentration of 33 and 44.4 g/909 kg (DM), respectively. Tylosin phosphate (Tylan 100, Elanco Animal Health) was included in rations 3 and 4 at a rate sufficient to supply 90 mg of tylosin phosphate per steer. Bovatec, Rumensin, Tylan, Actogain, and treatment premixes were hand weighed on analytical platform scales (Model ALC 2100.2, Aculab, Bradford, MA) to the nearest 0.01 g before their addition to the ration. Additives were placed in a flush bowl and mixed with approximately 22.7 L of water for 45 s. Rations were sampled daily and analyzed for DM content, and weekly composites of the daily samples were analyzed for nutrient
content (SDK Laboratory, Hutchinson, KS), 2 wk composites were analyzed for monensin sodium concentrations (Covance Laboratory, Greenfield, IN), and monthly composites were analyzed for mineral content (SDK Laboratory).
Daily Observations Steers were observed daily for abnormal conditions (morbidity, mortality, and adverse reactions) by trained personnel. Animals that required treatment were taken from their pens, treated, and returned to their home pens according to standard feedlot therapy. Animals that either
Table 1. Dry matter ingredient and nutrient composition of study rations with all treatments combined Item
Ration Ration Ration Ration CTC1 2 3 4
Ingredient, % Steam-flaked corn 61.5 63.9 72.2 Chopped alfalfa hay 20.2 25.6 15.8 Sorghum silage — — 1.9 Cane molasses 6.6 5.0 2.6 Choice white grease — 1.3 2.6 Finisher supplement2 — 4.2 4.9 Stress supplement3 11.7 — — Analyzed nutrient composition DM, % as fed 77.15 79.66 75.40 CP, % 14.34 14.37 13.96 NPN, % 1.02 2.21 2.82 Crude fiber, % 7.92 8.61 7.51 Fat, % 3.44 4.30 5.81 Calcium, % 0.58 0.87 0.91 Phosphorous, % 0.31 0.26 0.27 Potassium, % 1.24 1.20 1.00 Sulfur, % 0.15 0.19 0.18 Cobalt, mg/kg 0.48 0.22 Copper, mg/kg 14.30 10.68 Iodine, mg/kg 6.33 5.67 Iron, mg/kg 494.33 494.33 Manganese, mg/kg 41.87 29.77 Molybdenum, mg/kg 0.39 0.44 Selenium, mg/kg 0.38 0.38 Zinc, mg/kg 119.33 86.70
85.9 3.1 1.9 — 2.9 6.2 — 75.56 12.65 2.55 4.48 6.54 0.71 0.27 0.66 0.13 0.23 11.34 8.07 93.86 28.91 0.36 0.33 86.58
Ration CTC (chlortetracycline) was not analyzed for trace minerals due to the relatively short and intermittent duration of feeding for the study. 2 Contained on a DM basis 60.5% CP, 42.8% NPN, 3.9% salt, 9.9% Ca, 0.58% P, 0.45% Mg, 20,355 IU of vitamin A/kg, 2,039 IU of vitamin D/kg, and 20.4 IU of vitamin E/ kg. 3 Contained on a DM basis 27.5% CP, 6.0% NPN, 2.0% Ca, 0.93% P, 0.44% Mg, 100,517 IU of vitamin A/kg, 10,061 IU of vitamin D/kg, 502.5 IU of vitamin E/kg, and 22,164 g of chlortetracycline (Aureomycin, Zoetis, Parsippany, NJ). 1
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died or were euthanized (captive bolt followed by exsanguination) underwent necropsy by a qualified technician to ascertain cause of death.
Live Performance Pen BW of steers were obtained on d 0 and at 197, 198, 201, 202, 206, 207, 208, and 209 d on feed for blocks 4, 5, 2, 1, 7, 8, 6, and 3, respectively. Initial BW was calculated as the pen BW before processing divided by the number of steers placed. Final shrunk BW was calculated as the pen BW before slaughter divided by the number of steers placed on study. Total pen BW gain was calculated as total pen gain divided by total head days.
Carcass Characteristics Steers were slaughtered after an average of 204 d on feed at a commercial processing facility in southwest Kansas on April 5 (blocks 1, 2, 4, and 5) and May 9 (blocks 3, 6, 7, and 8), 2018. Carcass measurements were obtained by trained personnel and included HCW, USDA QG and YG, and marbling scores. Liver abscesses were scored according to the 3-point scale described by Elanco (1974). Measurements of LM area and 12th-rib backfat were also obtained using the Computer Vision System (Research Management Systems Inc., Fort Collins, CO).
Live Performance The CON diet contained an additional 360 mg per head per day of Zn methionine during the step-up period. Additional Zn methionine has been reported to maintain higher DMI and lower body temperature after infectious bovine rhinotracheitis virus challenge (Chirase et al., 1991), and it reduced percent morbid steers in a 28-d receiving program (Galyean et al., 1995) compared with inorganic Zn. Consequently, all rations contained a comparable Zn concentration during this time period. Therefore, interpretation of data must be evaluated within the context of Zn sources and levels that were different during the final 159 d on feed. The effect of Zn source and level on animal performance is presented in Table 3. Initial and final BW, DMI, ADG, and feed conversion were similar across treatments (P ≥ 0.23). Previously published literature evaluating the effect of supplemental Cu, Zn, and Mn from hydroxychloride, sulfate, and sulfate–organic combinations as well as different levels is limited. In agreement with the current study, Wagner et al. (2016) reported no differences
Table 2. Analyzed DM nutrient composition of treatment finisher rations
Statistical Analysis Feedlot performance, health, and carcass characteristics were the primary variables of interest. Pen was the experimental unit. Mixed model procedures (SAS Institute Inc., Cary, NC) were used that included the random effects of block, the fixed effects of treatment, and treatment × block as the error term. Tests of treatment differences were determined using preplanned orthogonal contrasts. Contrasts included CON versus COMBO and HYD (Zn level) and COMBO versus HYD (Zn source). Carcass traits were evaluated as categorical data using PROC GLIMMIX of SAS assuming a binomial distribution.
RESULTS AND DISCUSSION Analyzed Nutrient Concentration The formulated ingredient and nutrient compositions of the study diets are presented in Table 1. The analyzed treatment diet nutrient composition is presented in Table 2. The analyzed concentrations of the Cu, Zn, and Mn were very close to the targeted concentrations, except total Zn for the COMBO and HYD treatments was lower than expected, which cannot be explained and may be due to analytical error. Additionally, daily records maintained by the research site showed actual TM premix usages for the entire study were 100.40, 99.99, and 100.35% of the theoretical usage for CON, COMBO, and HYD, respectively.
Treatment1 Item
CON
COMBO
HYD
DM, % as fed CP, % NPN, % Fat, % Calcium, % Phosphorous, % Potassium, % Sulfur, % Cobalt, mg/kg Copper, mg/kg Iodine, mg/kg Iron, mg/kg Manganese, mg/kg Molybdenum, mg/kg Selenium, mg/kg Zinc, mg/kg
75.59 12.69 2.45 6.27 0.70 0.27 0.66 0.13 <0.20 11.78 7.43 102.52 32.97 <0.30 0.33 61.85
75.57 12.59 2.44 6.31 0.68 0.27 0.67 0.12 <0.20 10.76 8.06 92.23 27.83 <0.30 0.34 98.97
75.56 12.66 2.44 6.27 0.67 0.27 0.65 0.12 <0.20 11.47 9.04 86.83 25.92 <0.30 0.34 98.93
Treatments: CON = 10.6 mg/kg of Cu (72.2% Cu sulfate and 27.8% Cu AA complex), 37.8 mg/kg of Zn (77.6% Zn sulfate and 22.4% Zn AA complex), and 25.5 mg/kg of Mn (81.6% Mn sulfate and 18.4% Mn AA complex); COMBO = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate and 33% Zn methionine), and 20 mg/ kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride); HYD = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride).
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(P ≥ 0.50) in final BW, ADG, DMI, and G:F in yearling steers fed for 173 d when comparing a blend of 75% sulfate and 25% AAC Cu and Zn to 100% hydroxychloride trace minerals at an iso-level or a 40% reduced level. Additionally, Caldera et al. (2016) reported no differences (P ≥ 0.22) in final BW, DMI, ADG, and G:F when comparing an all-sulfate trace mineral program to 100% hydroxychloride trace minerals fed at an iso-level or multiple titrated reduced levels. Berrett et al. (2015) reported similar (P ≥ 0.26) live performance in steers fed no supplemental TM or 10, 30, and 20 mg/kg of Cu, Zn, Mn, respectively, from sulfate sources; 20, 100, and 50 mg/kg from sulfate sources; or 20, 100, and 50 from 66.6% sulfate and 33.4% organic sources (Cu AAC, Zn AAC, and Mn proteinate, respectively). Ahola et al. (2005) reported in a 2-yr study similar (P ≥ 0.75) final BW and ADG in steers and heifers receiving no added TM or added Cu, Zn, and Mn from sulfates or 67% sulfate/33% proteinate to meet NRC requirements. However, added TM tended to increase DMI (P = 0.10), and there was a treatment × year interaction for G:F: added TM increased G:F compared with control (P = 0.01) in yr 1 and the sulfate–organic combination increased G:F compared with sulfates (P = 0.04) in yr 2. Rhoads et al. (2003) also compared Cu, Zn, and Mn sulfates and AAC sources at different levels relative to NRC requirements and reported that source or level did not (P > 0.05) affect final BW or overall ADG or DMI, but AAC fed at 1× NRC had lower (P < 0.05) G:F than higher levels of sulfates but was similar to 1.5× NRC from AAC. Hill et al. (1996) concluded there was no difference (P ≥ 0.21) in live performance of steers receiving no supplemental TM compared with those supplemented with Cu,
Zn, and Mn sulfates or metal-specific AAC (MSAAC), but there was a tendency for MSAAC to reduce DMI (P = 0.08). Recently, Van Bibber-Krueger et al. (2019) showed no differences (P ≥ 0.29) in final BW and ADG in heifers supplemented with 0, 30, 60, or 90 mg/kg of Zn from Zn sulfate (basal diet = 51 mg/kg of Zn). However, increasing Zn concentration tended to decrease (linear effect, P = 0.07) DMI, resulting in a linear (P = 0.03) improvement in feed efficiency. Genther-Schroeder et al. (2018) reported no differences (P ≥ 0.16) in live performance of beef steers comparing no supplemental Zn (30 mg/kg from basal diet) with 60 mg/kg of added Zn sulfate or the 60 mg/kg of Zn sulfate plus an additional 60, 125, or 150 mg/kg of Zn AAC. Additionally, there was no difference (P ≥ 0.16) in live performance to increasing level of Zn AAC. In a similar study, Genther-Schroeder et al. (2016) reported no differences (P ≥ 0.80) during the preractopamine feeding period in final BW, ADG, and G:F between 60 mg/kg of Zn sulfate and 60 mg/kg of Zn sulfate plus 30, 60, or 90 mg/kg of added Zn AAC, but added Zn AAC tended (P = 0.08) to reduce DMI. During the ractopamine feeding period all live performance variables were similar (P ≥ 0.65) between control and Zn supplementation. However, during the final 28 d, increasing Zn AAC linearly increased (P ≤ 0.03) ADG and G:F in steers supplemented with ractopamine but not in those not receiving ractopamine. Montano et al. (2017) reported no differences (P ≥ 0.23) in final BW, ADG, and feed efficiency of Holstein steers when evaluating Zn sulfate (20 mg/kg), Zn betaine (20 mg/kg), a 50:50 combination of Zn sulfate:Zn betaine (20 mg/kg), and Zn sulfate (40 mg/kg). However, there was a linear (P
Table 3. Effects of supplemental Zn source and level on live performance and feed efficiency of feedlot seers Treatment1
Contrast (P =)
Item
CON
COMBO
HYD
SEM
CON vs. COMBO and HYD
COMBO vs. HYD
Pens No. of steers Initial BW, kg Final BW,2 kg DMI, kg ADG, kg Feed conversion
8 568 297.5 559.2 7.9 1.39 5.7
8 568 295.2 555.1 7.9 1.39 5.8
8 571 297.1 564.2 8.0 1.42 5.6
1.15 6.63 0.04 0.024 0.04
0.35 0.97 0.36 0.74 0.91
0.23 0.34 0.74 0.36 0.30
Treatments: CON = 10.6 mg/kg of Cu (72.2% Cu sulfate and 27.8% Cu AA complex), 37.8 mg/kg of Zn (77.6% Zn sulfate and 22.4% Zn AA complex), and 25.5 mg/kg of Mn (81.6% Mn sulfate and 18.4% Mn AA complex); COMBO = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate and 33% Zn methionine), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride); HYD = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride). 2 Final BW was shrunk (applied 4% pencil shrink on actual BW).
1
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= 0.11) and quadratic (P = 0.06) tendency for Zn betaine to decrease DMI. In another Zn study, Malcolm-Callis et al. (2000) reported no differences (P > 0.10) in final BW, overall DMI, ADG, and G:F in steers fed either Zn sulfate, Zn AAC, or Zn polysaccharide complex sources of supplemental Zn and 20, 100, or 200 mg/kg of added Zn from Zn sulfate.
Health Outcomes There were no differences (P ≥ 0.28) in any of the health outcomes: morbidity, mortality, repulls, or treatment days (Table 4). This may be partially explained by the fact that all cattle received very similar TM levels, including zinc for the first 45 d on feed when health issues are expected to be highest. Unfortunately, most feedlot finishing studies evaluating trace mineral programs fail to report health outcomes; therefore, there is limited data for similar comparisons with this study. However, Hilscher et al. (2019) found no differences (P ≥ 0.42) in morbidity, death loss, or foot rot incidence when feeding 19 mg/kg of Cu and 108 mg/kg of Zn from sulfate plus zinc methionine (ZnMet) compared with iso-levels from Cu and Zn hydroxychloride sources in finishing steers. Rhoads et al. (2003) reported a similar result for morbidity, with no differences (P > 0.05) between Cu, Zn, and Mn sulfates fed at 3× or 6× NRC requirements and AAC fed at 1× and 2× NRC requirements in finishing steers. Similarly, Ahola et al. (2005) reported no difference (P > 0.10) in number of cattle treated or re-treated for respiratory disease in a
2-yr study evaluating no added TM or TM from sulfates or a 50:50 sulfate:proteinate combination at NRC requirements. Grotelueschen et al. (2001) reported that feeding free-choice mineral mixes with Cu, Zn, and Mn AAC close to NRC requirements resulted in 49 and 56.9% fewer (P < 0.05) sick incidents in the feedlot compared with no supplemental TM or a sulfate-based mineral at approximately 2× NRC requirements, respectively. However, feedlot mortality was the same (P > 0.05). Galyean et al. (1995) reported that 35 or 70 mg/kg of added Zn from Zn sulfate or ZnMet nor added Cu lysine affected live performance or morbidity in a 28-d receiving period (P > 0.10). However, during the step-up periods to the finishing diet, the percentage of morbid steers was reduced (P < 0.07) by 70 mg/kg of added Zn from Zn sulfate or ZnMet compared with 30 mg/kg from ZnO and 35 mg/kg of ZnMet. Finally in the same study, 161-d finishing-period ADG, feed efficiency, and carcass measurements were unaffected (P > 0.10) by supplemental Zn source or level. Two studies evaluating sulfates, AAC, and hydroxychloride sources fed at the same rates (approximate NRC requirements) reported similar (P ≥ 0.43) morbidity in steers (Ryan et al., 2015) and heifers (Weibert et al., 2017) in receiving/ backgrounding programs.
Carcass Characteristics There were no differences (P ≥ 0.32) in HCW, DP, backfat thickness, or liver abscesses (Table 5). However, HCW distribution was significantly different (P = 0.05) in CON
Table 4. Effects of supplemental Zn source and level on health variables Treatment1 Item
CON
No. of steers 568 No. of steers pulled 164 Morbidity, % 28.5 No. of steers repulled 72 Repull, % 43.7 No. dead 38 Mortality, % 6.5 Total treatment days2 286 Average treatment days3 1.7
Contrast (P =)
COMBO
HYD
CON vs. COMBO vs. HYD SEM COMBO and HYD
568 177 31.2 86 48.6 44 7.5 313 1.7
571 176 30.9 80 45.3 35 6.0 303 1.7
1.25 1.85 2.69 1.03 2.76 0.07
0.28 0.35 0.83 0.43 0.93
0.89 0.40 0.33 0.75 0.46
Treatments: CON = 10.6 mg/kg of Cu (72.2% Cu sulfate and 27.8% Cu AA complex), 37.8 mg/kg of Zn (77.6% Zn sulfate and 22.4% Zn AA complex), and 25.5 mg/kg of Mn (81.6% Mn sulfate and 18.4% Mn AA complex); COMBO = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate and 33% Zn methionine), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride); HYD = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride). 2 Total treatment days = the number of days an antibiotic was administered. 3 Average treatment days = total treatment days divided by number of animals pulled at least one time. 1
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versus COMBO and HYD. The CON had fewer 430.8- to 453.1-kg carcasses (9.40% vs. 11.69 and 14.33%, respectively). The CON also tended to have fewer (P = 0.14) 453.5- to 475.5-kg carcasses compared with COMBO and HYD (4.37% vs. 5.90 and 6.56%, respectively). There was a tendency for HYD to have a higher (P = 0.10) calculated YG and smaller (P = 0.14) LM area compared with COMBO. Marbling score also tended to be lower (P = 0.13) in CON compared with COMBO and HYD. Last, there were no differences (P ≥ 0.16) in USDA QG and YG distribution or percentage dark cutters (Table 6). There are conflicting results within the literature on the effect of TM source and level on carcass responses; studies have shown improvement (Genther-Schroeder et al., 2016; Wagner et al., 2016; Montano et al., 2017), decline (Rhoads et al., 2003; Berrett et al., 2015), or no differences (Hill et al., 1996; Ahola et al., 2005; Caldera et al., 2016) in carcass performance with different supplemental TM programs. Similar to this study, Wagner et al. (2016) reported no differences (P ≥ 0.17) in HCW, DP, backfat thickness, KPH, YG, LM area, marbling score, and liver abscesses when comparing a blend of 75% Cu and Zn sulfate and 25% Cu and Zn AAC to 100% hydroxychloride trace minerals at either an iso-level or a 40% reduced level. However, there was a tendency (P = 0.12) for the hydroxychloride Cu and Zn treatments to improve percentage of choice or greater
carcasses. Caldera et al. (2016) reported no differences (P ≥ 0.19) in HCW, DP, backfat thickness, KPH, YG, LM area, and marbling score when comparing an all sulfate TM program to 100% hydroxychloride TM fed at either an iso-level or multiple reduced levels. Berrett et al. (2015) reported no differences (P ≥ 0.20) in HCW, DP, backfat thickness, KPH, LM area, marbling score, and liver abscesses when comparing no supplemental TM to 2 levels of Cu, Zn, and Mn sulfates or a sulfate–organic combination. They did however report that the QG distribution was affected by TM program; the sulfate–organic program increased the percentage select carcasses (P = 0.02) 50.00 versus 27.7% compared with all sulfates when fed at 20 mg/kg of Cu, 100 mg/kg of Zn, and 50 mg/kg of Mn. In a 2-yr study in finishing steers and heifers, Ahola et al. (2005) reported no affect (P ≥ 0.20) on carcass traits when comparing no supplemental TM to Cu, Zn, and Mn sulfates and sulfate–proteinate combination. Rhoads et al. (2003) reported extremely mixed results for carcass characteristics when evaluating Cu, Zn, and Mn AAC and sulfates at different levels. They found HCW, YG, and KPH were similar (P > 0.05); however, 1.5× NRC from sulfates and AAC had lower (P < 0.05) DP than 1× AAC and 3× sulfate. Sulfates fed at 3× had smaller (P < 0.05) LM area than 1.5× sulfate but similar to both AAC levels. Backfat thickness was less (P < 0.05) in the 1.5× AAC treatment
Table 5. Effects of supplemental Zn source and level on carcass characteristics and liver abscesses of feedlot steers Treatment1
Contrast (P =)
Item
CON
COMBO
HYD
n HCW, kg HCW distribution, % <249.4 kg 430.8 to 453.1 kg 453.5 to 475.7 kg >476.2 kg DP Calculated YG LM area, cm2 (LM area/HCW) × 100 Backfat thickness, cm Marbling score2 Liver abscesses, %
499 397.7 0.00 9.40 4.37 2.94 64.5 2.7 98.8 1.8 1.50 461.6 32.0
496 398.2 0.17 11.69 5.90 2.64 64.5 2.7 100.0 1.8 1.50 470.6 33.6
507 398.6 0.00 14.33 6.56 2.72 64.5 2.8 98.4 1.8 1.55 469.5 29.9
CON vs. COMBO vs. HYD SEM COMBO and HYD 1.81 0.10 1.35 0.98 0.62 0.09 0.05 0.77 0.01 0.025 4.30 3.96
0.78 0.49 0.05 0.14 0.74 0.85 0.65 0.68 0.86 0.38 0.13 0.95
0.83 0.24 0.19 0.64 0.93 0.89 0.10 0.14 0.37 0.32 0.86 0.52
Treatments: CON = 10.6 mg/kg of Cu (72.2% Cu sulfate and 27.8% Cu AA complex), 37.8 mg/kg of Zn (77.6% Zn sulfate and 22.4% Zn AA complex), and 25.5 mg/kg of Mn (81.6% Mn sulfate and 18.4% Mn AA complex); COMBO = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate and 33% Zn methionine), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride); HYD = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride). 2 Marbling score: 300 = Slight0, 400 = Small0, 500 = Modest0.
1
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Nutrition
Table 6. Effects of supplemental Zn source and level on categorical carcass characteristics of feedlot steers Treatment1
Contrast (P =)
Item
CON
COMBO
HYD
SEM
CON vs. COMBO and HYD
COMBO vs. HYD
n QG distribution,2 % Prime Choice Select Standard YG distribution,2 % YG 1 YG 2 YG 3 YG 4 YG 5 Total dark cutters, %
499 1.4 76.6 22.1 0.0 22.1 44.3 26.3 6.6 0.8 0.0
496 2.5 75.8 21.5 0.2 22.2 42.0 28.1 6.7 1.0 0.6
507 2.0 75.0 22.2 0.0 21.9 39.4 29.2 9.1 0.4 0.2
0.56 1.62 1.51 0.10 1.26 2.95 2.18 1.31 0.37 0.22
0.22 0.71 0.90 0.49 0.98 0.34 0.38 0.44 0.82 0.16
0.58 0.99 0.77 0.24 0.87 0.54 0.72 0.21 0.25 0.19
Treatments: CON = 10.6 mg/kg of Cu (72.2% Cu sulfate and 27.8% Cu AA complex), 37.8 mg/kg of Zn (77.6% Zn sulfate and 22.4% Zn AA complex), and 25.5 mg/kg of Mn (81.6% Mn sulfate and 18.4% Mn AA complex); COMBO = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate and 33% Zn methionine), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride); HYD = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride). 2 USDA grades were assigned by USDA graders as reported by the packing plant; distributions represent the percentage of carcasses assigned a given grade.
1
compared with 1× AAC and 3× sulfate but similar to 1.5× sulfate. Finally, marbling score in 1× AAC was lower (P < 0.05) than 1.5× AAC but similar to both sulfate levels. Similarly, Hill et al. (1996) reported no differences (P ≥ 0.20) in carcass traits between unsupplemented steers and steers receiving Cu, Zn, and Mn MSAAC and sulfates, but there was a tendency for control steers to have less KPH (P = 0.06) than TM fed steers and for sulfates to increase backfat thickness (P = 0.14) and YG (P = 0.13) compared with MSAAC. Multiple Zn source and level studies have yielded quite variable results. Recently, Van Bibber-Krueger et al. (2019) reported no differences (P > 0.53) in carcass characteristics with increasing supplemental Zn from Zn sulfate at 0, 30, 60, or 90 mg/kg, but there was a tendency for a quadratic effect (P = 0.07) on carcasses that graded prime, which peaked at 60 mg/kg of Zn. GentherSchroeder et al. (2018) also reported similar (P ≥ 0.18) carcass traits between no supplemental Zn, 60 mg/kg of Zn sulfate, or 60 mg/kg of Zn sulfate plus 60, 120, or 150 mg/kg of Zn AAC except all added Zn treatments had a lower (P = 0.03) marbling score compared with no added Zn. In a similarly designed trial, Genther-Schroeder et al. (2016) reported similar (P ≥ 0.65) carcass results when feeding 60 mg/kg of Zn sulfate and 60 mg/kg of Zn sulfate plus 30, 60, 90 mg/kg of Zn AAC except added Zn
AAC decreased backfat thickness (P = 0.04) and tended to increase LM area (P = 0.14), therefore decreasing YG (P = 0.04). Montano et al. (2017) also reported mostly similar (P ≥ 0.35) carcass traits in Holstein steers when comparing Zn sulfate, Zn betaine, and Zn sulfate/Zn betaine combination except there was tendency for 40 mg/ kg of Zn sulfate to increase DP (P = 0.14) and decrease KPH (P = 0.13). Malcolm-Callis et al. (2000) reported no difference (P > 0.10) in HCW, DP, LM area, KPH, and marbling score in steers fed Zn sulfate at 20, 100, and 200 mg/kg, but there was a quadratic (P < 0.05) effect of Zn level on backfat thickness and YG.
APPLICATIONS Under the conditions of this experiment, all supplemental treatments, regardless of source or level, appeared to have effectively met the Zn requirements for feedlot steers, resulting in no differences between treatments. The lack of performance, health, and carcass differences provide additional evidence that supplemental Zn fed in excess of NASEM (2016) requirements may not be warranted and may be supplemented at lower concentrations than those reported by feedlot nutritionists (Samuelson et al., 2016) without adversely affecting live or carcass performance. Additionally, if higher levels of supplemental Zn are to be
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fed, supplemental TM costs become an important factor in determining which TM program to use because of the lack of performance differences noted between sources.
Hilscher, F. H., S. B. Laudert, J. S. Heldt, R. J. Cooper, B. D. Dicke, D. J. Jordon, T. L. Scott, and G. E. Erickson. 2019. Effect of copper and zinc source on finishing performance and incidence of foot rot in feedlot steers. Prof. Anim. Sci. 35:94–100.
ACKNOWLEDGMENTS
Leisure, N. J., C. C. Jackson, M. Huang, T. B. Moore, and F. A. Stewart. 2014. Micronutrient supplement. Heritage Technologies LLC, assignee. US Pat. No. 8,802,180 B2.
Funding was provided by Micronutrients USA LLC (Indianapolis, IN).
LITERATURE CITED
Malcolm-Callis, K. J., G. C. Duff, S. A. Gunter, E. B. Kegley, and D. A. Vermeire. 2000. Effects of supplemental zinc concentration and source on performance, carcass characteristics, and serum values in finishing beef steers. J. Anim. Sci. 78:2801–2808. https://doi.org/10 .2527/2000.78112801x.
Ahola, J. K., L. R. Sharpe, K. L. Dorton, P. D. Burns, T. L. Stanton, and T. E. Engle. 2005. Effects of lifetime copper, zinc, and manganese supplementation and source on performance, mineral status, immunity, and carcass characteristics of feedlot cattle. Prof. Anim. Sci. 21:305–317. https://doi.org/10.2527/jas.2014-8661.
Montano, M. F., A. Plascencia, J. Salinas-Chavira, N. Torrentera, and R. A. Zinn. 2017. Influence of level and form of supplemental zinc on feedlot growth performance and carcass characteristics of calf-fed Holstein steers. Prof. Anim. Sci. 33:651–658. https://doi.org/10.15232/ pas.2017-01640.
Berrett, C. J., J. J. Wagner, K. L. Neuhold, E. Caldera, K. S. Sellins, and T. E. Engle. 2015. Comparison of National Research Council standards and industry trace mineral supplementation strategies for yearling feedlot steers. Prof. Anim. Sci. 31:237–247. https://doi.org/ 10.15232/pas.2014-01345.
NASEM. (National Academies of Sciences, Engineering, and Medicine). 2016. Nutrient Requirements of Beef Cattle. 8th rev. ed. Natl. Acad. Press, Washington, DC.
Caldera, E., J. J. Wagner, K. Sellins, S. B. Laudert, J. W. Spears, S. L. Archibeque, and T. E. Engle. 2016. Effects of supplemental zinc, copper, and manganese concentration and source on performance and carcass characteristics of feedlot steers. Prof. Anim. Sci. 33:63–72. https://doi.org/10.15232/pas.2016-01531. Chirase, N. K., D. P. Hutcheson, and G. B. Thompson. 1991. Feed intake, rectal temperature, and serum mineral concentrations of feedlot cattle fed zinc oxide or zinc methionine and challenged with infectious bovine rhinotracheitis virus. J. Anim. Sci. 69:4137–4145. https://doi .org/10.2527/1991.69104137x. Elanco. 1974. Tylan Premix for Beef Cattle. Technical B Manual. Elanco, Indianapolis, IN. Galyean, M. L., K. J. Malcolm-Callis, S. A. Gunter, and R. A. Berrie. 1995. Effects of zinc source and level of added copper lysine in the receiving diet on performance by growing and finishing cattle. Prof. Anim. Sci. 11:139–148. https://doi.org/10.15232/S1080 -7446(15)32578-X. Genther-Schroeder, O. N., M. E. Branine, and S. L. Hansen. 2016. The effects of increasing supplementation of zinc-amino acid complex on growth performance, carcass characteristics, and inflammatory response of beef cattle fed ractopamine hydrochloride. J. Anim. Sci. 94:3389–3398. https://doi.org/10.2527/jas.2015-0209. Genther-Schroeder, O. N., M. E. Branine, and S. L. Hansen. 2018. Effects of increasing supplemental dietary Zn concentration on growth performance and carcass characteristics in finishing steers fed ractopamine hydrochloride. J. Anim. Sci. 96:1903–1913. https://doi.org/10 .1093/jas/sky094. Grotelueschen, D. M., A. Wohlers, C. Dewey, I. G. Rush, W. E. Braselton, D. Hamar, A. B. Johnson, and J. H. Pollreisz. 2001. Effect of pasture trace mineral supplementation on liver mineral levels and feedlot morbidity and mortality. Bov. Pract. 35:73–84. Hill, W. J., D. S. Secrist, F. N. Owens, C. A. Strasia, D. R. Gill, M. Basalan, and A. B. Johnson. 1996. Effects of trace mineral supplements on performance of feedlot steers. Okla. State Univ. Anim. Sci. Res. Rep. P-951. Okla. State Univ., Stillwater.
NRC. 2000. Nutrient Requirements of Beef Cattle. 7th rev. ed. Natl. Acad. Press, Washington, DC. Rhoads, A. R., T. L. Stanton, T. E. Engle, and C. V. Kimberling. 2003. Effects of concentration and source of trace minerals on performance, immunity, mineral and lipid metabolism, and carcass characteristics of beef steers. Prof. Anim. Sci. 19:150–158. https://doi.org/ 10.15232/S1080-7446(15)31394-2. Ryan, A. W., E. B. Kegley, J. Hawley, J. G. Powell, J. A. Hornsby, J. L. Reynolds, and S. B. Laudert. 2015. Supplemental trace minerals (zinc, copper, and manganese) as sulfates, organic amino acid complexes, or hydroxy trace mineral sources for shipping stressed calves. Prof. Anim. Sci. 31:333–341. https://doi.org/10.15232/pas .2014-01383. Samuelson, K. L., M. E. Hubbert, M. L. Galyean, and C. A. Löest. 2016. Nutritional recommendations of feedlot consulting nutritionists: The 2015 New Mexico State and Texas Tech University survey. J. Anim. Sci. 94:2648–2663. https://doi.org/10.2527/jas.2016-0282. Van Bibber-Krueger, C. L., C. I. Vahl, S. K. Narayanan, R. G. Amachawadi, E. A. Taylor, H. M. Scott, and J. S. Drouillard. 2019. Effects of supplemental zinc sulfate on growth performance, carcass characteristics, and antimicrobial resistance in feedlot heifers. J. Anim. Sci. 97:424–436. https://doi.org/10.1093/jas/sky411. Vasconcelos, J. T., and M. L. Galyean. 2007. Nutritional recommendations of feedlot consulting nutritionists: The 2007 Texas Tech University survey. J. Anim. Sci. 85:2772–2781. https://doi.org/10.2527/ jas.2007-0261. Wagner, J. J., T. E. Engle, E. Caldera, K. L. Neuhold, D. R. Woerner, J. W. Spears, J. S. Heldt, and S. B. Laudert. 2016. The effects of zinc hydroxychloride and basic copper chloride on growth performance, carcass characteristics, and liver zinc and copper status at slaughter in yearling feedlot steers. Prof. Anim. Sci. 32:570–579. https://doi.org/ 10.15232/pas.2015-01480. Weibert, C. S., W. R. Hollenbeck, S. B. Laudert, J. D. Kubick, and D. A. Blasi. 2017. Evaluation of trace mineral sources on newly arrived stocker cattle. Pages 60–62 in Proc. Cattlemen’s Day 2017. Kansas State Univ., Manhattan.
NUTRITION: Original Research
Effects of supplemental zinc source and level on finishing performance, health, and carcass characteristics of beef feedlot steers J. S. Heldt1* PAS, and M. S. Davis,2 PAS 1 Micronutrients USA LLC, Indianapolis, IN 46231-3350; and 2Bos Technica Research Services, Salina, KS 674018458
ABSTRACT
INTRODUCTION
Objective: Our objective was to compare the effects of supplemental Zn sources and levels on health, growth, and carcass characteristics in finishing steers. Materials and Methods: Crossbred steer calves (n = 1,502; initial BW = 297 ± 5 kg) were housed in 24 pens with 8 pens per treatment in a randomized complete block design. Treatments (100% DM) consisted of the following: (1) control: 10.6 mg/kg of Cu [72.2% Cu sulfate/27.8% Cu AA complex (AAC)], 37.8 mg/kg of Zn (77.6% Zn sulfate/22.4% Zn AAC), and 25.5 mg/kg of Mn (81.6% Mn sulfate/18.4% Mn AAC); (2) combination: 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate/33% Zn methionine), and 20 mg/kg of Mn (75% Mn sulfate/25% Mn hydroxychloride); and (3) hydroxy: 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate/25% Mn hydroxychloride). Results and Discussion: There were no significant differences in DMI, ADG, final BW, F:G, morbidity, or mortality (P ≥ 0.28). Hot carcass weight, DP, and backfat were also unaffected (P ≥ 0.32) by treatment. Increased level of Zn tended (P = 0.13) to increase marbling score. There was a tendency for combination to have a larger LM area (P = 0.14) and lower YG (P = 0.10) compared with hydroxy. Implications and Applications: Steers fed a lower level of Zn sulfate/AAC had similar performance compared with steers fed a higher level of Zn. Zinc hydroxychloride is equally effective as a Zn sulfate/Zn methionine combination when fed at 90 mg/kg.
Supplemental trace mineral (TM) programs for feedlot diets are designed to meet the animals’ nutrient requirements and provide a safety factor to account for any potential antagonists found in the basal feedstuffs or water supply. This can be approached by simply increasing the supplemental amount, altering the TM source, or both. In a 2007 survey of consulting nutritionists, the modes for levels of supplemental Cu, Zn, and Mn were 2 to 3 times greater than the NRC (2000) requirement (Vasconcelos and Galyean, 2007). In a 2016 follow-up survey, 54.6% of consulting nutritionists indicated a preference for a combination of organic and inorganic sources, 45.4% indicated a preference for only organic sources in finishing diets, and the mode for levels was identical to the previous survey (Samuelson et al., 2016). This indicates that consulting nutritionists currently do not follow NRC recommendations and see value in feeding nonsulfate forms of TM to meet their nutritional goals. Inorganic TM sources are generally supplied in the sulfate form. Sulfate trace minerals are a single metal ion associated with a single sulfate ion through an ionic bond. However, a new category of inorganic trace minerals, hydroxy trace minerals, has been developed. Basic Cu chloride, Zn hydroxychloride, and Mn hydroxychloride are crystalline mineral sources formed by covalent bonds between the metal, chloride, and hydroxyl groups (Leisure et al., 2014). Organic trace minerals are molecules where the metal ion is covalently bound to a carbon-containing molecule. The carbon source can be from a carbohydrate, hydrolyzed protein, or a single AA. Many different sources of organic TM, inorganic TM, and subsequent combinations have been studied in feedlot cattle, and results have been variable (Rhoads et al., 2003; Ahola et al., 2005; Berrett et al., 2015; Caldera et al., 2016; Wagner et al., 2016). The variable results indicate the need to further investigate TM supplementation in the feedlot industry to help increase the breadth of knowledge to support one source or combination of sources over the other and to better define optimal levels within the currently used sources. The decision to use different sources and levels of Zn should be
Key words: finishing, zinc, hydroxychloride, organic trace mineral
One of the authors works for Micronutrients USA LLC, Indianapolis, Indiana, which provided funding. The authors declare no conflict of interest. *Corresponding author: jeff.heldt@micro.net
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based on scientific evidence for performance outcomes and economics. Therefore, the objective of this study was to compare the effects of Zn source and level on performance, health, and carcass characteristics in steers fed diets based on steam-flaked corn in a commercial feedlot setting.
MATERIALS AND METHODS Cattle Processing and Allotment Procedures This study was conducted at a commercial facility in a manner consistent with applicable laws and regulations governing the humane care of animals. Steers were observed at least once daily to ensure animals were healthy, and if any abnormality was detected, prompt and adequate treatment was performed by trained and qualified personnel. A total of 1,707 cross-bred steers (initial BW of 297 ± 5 kg) sourced from ranches and livestock auctions in Oklahoma, Texas, and Missouri were used in a randomized complete block designed study conducted at a commercial research facility near Watonga, Oklahoma (Bos Technica Research Services) from October 2017 to May 2018 (days on feed across blocks averaged 204 d). Steers originated from 21 sources and arrived at the research site between October 4 and 14, 2017, where they remained segregated by day of arrival and source until adequate numbers arrived to meet the head-count requirement for one block. Each block consisted of 3 pens randomly assigned to 1 of 3 treatments. Before pen assignment, any animals that were injured, exhibited clinical signs of disease, were bulls, or were exhibiting phenotypic characteristics of Brahman influence were sorted from the pool of steers available for study enrollment and were not included in the study. Within an arrival day and source, steers were assigned randomly no more than 8 head at a time to 1 of 3 pens in a block before initial processing. There was a total of 8 blocks of cattle. The trial was initiated with 1,502 steers that met the trial criteria. Immediately following randomization, steers were taken by pen to a 21.3-m platform scale (Fairbanks, TRBT88, Kansas City, MO) and weighed in one draft. The platform weight served as initial starting weight for each pen, and the scale was balanced between each pen. Initial processing occurred immediately after obtaining pen weights. Each steers was vaccinated against viral (Pyramid 5 + Presponse, Boehringer Ingelheim Vetmedica Inc., St. Joseph, MO) and clostridial (Vision 7, Merck Animal Health, Summit, NJ) diseases and treated for internal parasites with doramectin (Dectomax Injectable Solution, Zoetis Inc., Parsippany, NJ) and fenbendazole (Safe-Guard, Merck Animal Health). Steers were also administered a metaphylaxis dose of tuluthromycin (Draxxin, Zoetis Inc.). Each steer was implanted in the right ear with Revalor-XS (120 mg of trenbolone acetate and 24 mg of estradiol, Merck Animal Health) and not reimplanted before slaughter. A visual tag containing
lot number and an individual identification number was placed in the left ear, providing dual identification. Cattle were housed in 24 nonshaded 21.3 × 73.2 m open dirt pens (71 steers per pen) with individual continuous-flow water tanks (0.12 linear meters per steer) and fence-line feed bunks (0.28 linear meters per steer). Following initial processing, trained pen riders were instructed to observe a 10-d post-metaphylaxis interval for all pens. During this 10-d period, all pens were ridden, but no steers could be pulled for respiratory disease.
Treatments Treatments, expressed on a 100% DM basis, consisted of (1) control (CON): 10.6 mg/kg of Cu [72.2% Cu sulfate and 27.8% Cu AA complex (AAC); Availa Cu, Zinpro Corporation, Eden Prairie, MN], 37.8 mg/kg of Zn (77.6% Zn sulfate and 22.4% Zn AAC; Availa Zn, Zinpro Corporation), and 25.5 mg/kg of Mn (81.6% Mn sulfate and 18.4% Mn AAC; Availa Mn, Zinpro Corporation); (2) combination (COMBO): 10 mg/kg of Cu (100% basic copper chloride; IntelliBond C, Micronutrients USA LLC, Indianapolis, IN), 90 mg/kg of Zn (67% Zn sulfate and 33% Zn methionine; ZINPRO 120, Zinpro Corporation), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride; IntelliBond M, Micronutrients USA LLC); (3) hydroxy trace minerals (HYD): 10 mg/kg of Cu (100% basic copper chloride; IntelliBond C), 90 mg/kg of Zn (100% Zn hydroxychloride; IntelliBond Z, Micronutrients USA LLC), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride; IntelliBond M, Micronutrients USA LLC). Treatment design was based largely on the most recent feedlot nutritionist survey where 81.9% of survey respondents reported that they give zero or only partial credit to basal feedstuffs for TM values, along with 77.3 and 54.6% of respondents who indicated a preference for a combination of TM sources to be used in receiving and finishing diets, respectively (Samuelson et al., 2016). Additionally, this survey reported that the mean added Zn level in receiving and finishing diets was 109 mg/kg and 87.3 mg/kg, respectively (Samuelson et al., 2016). This published information combined with limited large pen field trials evaluating the effectiveness of hydroxychloride sources of TM in finishing diets were all factored in to development of experimental treatments. Furthermore, the authors recognize that the amounts of the different organic sources may be inconsistent with manufacturer recommendations. However, the amounts used in this study are consistent with field observations of current industry practices and personal communications with industry professionals where these products are used. In addition, Co (Co carbonate), I (ethylenediamine dihydroiodide), and Se (sodium selenate) supplemental concentrations were 0.1, 1.4, and 0.14 mg/kg of DM, respectively. Trace mineral treatments were administered through a dry, loose meal premix.
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Rations Rations were formulated to meet or exceed NRC (2000) requirements, and composition is shown in Table 1. Each pen was provided feed thrice daily using a single-axle truck equipped with a mixer-delivery box (Harsh 430H, Eaton, CO). All rations and water were provided to allow for ad libitum consumption. Feed amounts delivered to each pen were recorded manually by the feed-truck driver and electronically by the feed-truck scale system, and the delivery amount was printed at the time of feeding. Bunks were managed by a clean-bunk system, so the amount of feed provided daily was adjusted so bunks contained little to no orts after 24 h. On occasion, when feed remained in the bunk before the first feeding [e.g., inclement weather (i.e., rain or snow) or at the discretion of the site manager], it was removed, weighed, and sampled for DM using a laboratory convection oven on site. An adjustment of daily intake was made on a DM basis. Total feed intake per pen was calculated on a DM basis as the amount of feed offered minus the weighed-back portion of the feed. Daily feed intake was then calculated as total feed intake divided by total animal days, where total animal days was equal to the number of days each steer was in its home pen from start to finish of the study, totaled for each pen. Steers were adjusted to final finisher ration using a series of step-up rations (Table 1). Ration 2 was fed for 27 to 32 d depending on block, and ration 3 was fed for 14 d for all blocks. During the first 30 d on feed, a portion (1% of BW as fed) of ration 2 was replaced with ration chlortetracycline. The ration chlortetracycline was fed so cattle would receive 1 g of chlortetracycline (Aureomycin 90, Zoetis) per 45.4 kg of BW during the first 5 consecutive days of each of the first 4 wk of the study. During the step-up period, an additional 360 mg of Zn from Zn methionine was added to the ration provided to the CON steers. Steers were adjusted to the finishing diet within 7 wk after arrival. Commencing 30 d before slaughter, ractopamine hydrochloride (Actogain 45, Zoetis Inc.) was fed to supply 300 mg of ractopamine hydrochloride per steer per day. On the day before slaughter, steers were provided 80% of the previous 5-d ADFI (as-fed basis). Lasalocid sodium (Bovatec 90, Zoetis Inc.) was included in ration 2 at a concentration of 33 g/909 kg (DM). Monensin sodium (Rumensin 90, Elanco Animal Health, Greenfield, IN) was included in rations 3 and 4 at a concentration of 33 and 44.4 g/909 kg (DM), respectively. Tylosin phosphate (Tylan 100, Elanco Animal Health) was included in rations 3 and 4 at a rate sufficient to supply 90 mg of tylosin phosphate per steer. Bovatec, Rumensin, Tylan, Actogain, and treatment premixes were hand weighed on analytical platform scales (Model ALC 2100.2, Aculab, Bradford, MA) to the nearest 0.01 g before their addition to the ration. Additives were placed in a flush bowl and mixed with approximately 22.7 L of water for 45 s. Rations were sampled daily and analyzed for DM content, and weekly composites of the daily samples were analyzed for nutrient
content (SDK Laboratory, Hutchinson, KS), 2 wk composites were analyzed for monensin sodium concentrations (Covance Laboratory, Greenfield, IN), and monthly composites were analyzed for mineral content (SDK Laboratory).
Daily Observations Steers were observed daily for abnormal conditions (morbidity, mortality, and adverse reactions) by trained personnel. Animals that required treatment were taken from their pens, treated, and returned to their home pens according to standard feedlot therapy. Animals that either
Table 1. Dry matter ingredient and nutrient composition of study rations with all treatments combined Item
Ration Ration Ration Ration CTC1 2 3 4
Ingredient, % Steam-flaked corn 61.5 63.9 72.2 Chopped alfalfa hay 20.2 25.6 15.8 Sorghum silage — — 1.9 Cane molasses 6.6 5.0 2.6 Choice white grease — 1.3 2.6 Finisher supplement2 — 4.2 4.9 Stress supplement3 11.7 — — Analyzed nutrient composition DM, % as fed 77.15 79.66 75.40 CP, % 14.34 14.37 13.96 NPN, % 1.02 2.21 2.82 Crude fiber, % 7.92 8.61 7.51 Fat, % 3.44 4.30 5.81 Calcium, % 0.58 0.87 0.91 Phosphorous, % 0.31 0.26 0.27 Potassium, % 1.24 1.20 1.00 Sulfur, % 0.15 0.19 0.18 Cobalt, mg/kg 0.48 0.22 Copper, mg/kg 14.30 10.68 Iodine, mg/kg 6.33 5.67 Iron, mg/kg 494.33 494.33 Manganese, mg/kg 41.87 29.77 Molybdenum, mg/kg 0.39 0.44 Selenium, mg/kg 0.38 0.38 Zinc, mg/kg 119.33 86.70
85.9 3.1 1.9 — 2.9 6.2 — 75.56 12.65 2.55 4.48 6.54 0.71 0.27 0.66 0.13 0.23 11.34 8.07 93.86 28.91 0.36 0.33 86.58
Ration CTC (chlortetracycline) was not analyzed for trace minerals due to the relatively short and intermittent duration of feeding for the study. 2 Contained on a DM basis 60.5% CP, 42.8% NPN, 3.9% salt, 9.9% Ca, 0.58% P, 0.45% Mg, 20,355 IU of vitamin A/kg, 2,039 IU of vitamin D/kg, and 20.4 IU of vitamin E/ kg. 3 Contained on a DM basis 27.5% CP, 6.0% NPN, 2.0% Ca, 0.93% P, 0.44% Mg, 100,517 IU of vitamin A/kg, 10,061 IU of vitamin D/kg, 502.5 IU of vitamin E/kg, and 22,164 g of chlortetracycline (Aureomycin, Zoetis, Parsippany, NJ). 1
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died or were euthanized (captive bolt followed by exsanguination) underwent necropsy by a qualified technician to ascertain cause of death.
Live Performance Pen BW of steers were obtained on d 0 and at 197, 198, 201, 202, 206, 207, 208, and 209 d on feed for blocks 4, 5, 2, 1, 7, 8, 6, and 3, respectively. Initial BW was calculated as the pen BW before processing divided by the number of steers placed. Final shrunk BW was calculated as the pen BW before slaughter divided by the number of steers placed on study. Total pen BW gain was calculated as total pen gain divided by total head days.
Carcass Characteristics Steers were slaughtered after an average of 204 d on feed at a commercial processing facility in southwest Kansas on April 5 (blocks 1, 2, 4, and 5) and May 9 (blocks 3, 6, 7, and 8), 2018. Carcass measurements were obtained by trained personnel and included HCW, USDA QG and YG, and marbling scores. Liver abscesses were scored according to the 3-point scale described by Elanco (1974). Measurements of LM area and 12th-rib backfat were also obtained using the Computer Vision System (Research Management Systems Inc., Fort Collins, CO).
Live Performance The CON diet contained an additional 360 mg per head per day of Zn methionine during the step-up period. Additional Zn methionine has been reported to maintain higher DMI and lower body temperature after infectious bovine rhinotracheitis virus challenge (Chirase et al., 1991), and it reduced percent morbid steers in a 28-d receiving program (Galyean et al., 1995) compared with inorganic Zn. Consequently, all rations contained a comparable Zn concentration during this time period. Therefore, interpretation of data must be evaluated within the context of Zn sources and levels that were different during the final 159 d on feed. The effect of Zn source and level on animal performance is presented in Table 3. Initial and final BW, DMI, ADG, and feed conversion were similar across treatments (P ≥ 0.23). Previously published literature evaluating the effect of supplemental Cu, Zn, and Mn from hydroxychloride, sulfate, and sulfate–organic combinations as well as different levels is limited. In agreement with the current study, Wagner et al. (2016) reported no differences
Table 2. Analyzed DM nutrient composition of treatment finisher rations
Statistical Analysis Feedlot performance, health, and carcass characteristics were the primary variables of interest. Pen was the experimental unit. Mixed model procedures (SAS Institute Inc., Cary, NC) were used that included the random effects of block, the fixed effects of treatment, and treatment × block as the error term. Tests of treatment differences were determined using preplanned orthogonal contrasts. Contrasts included CON versus COMBO and HYD (Zn level) and COMBO versus HYD (Zn source). Carcass traits were evaluated as categorical data using PROC GLIMMIX of SAS assuming a binomial distribution.
RESULTS AND DISCUSSION Analyzed Nutrient Concentration The formulated ingredient and nutrient compositions of the study diets are presented in Table 1. The analyzed treatment diet nutrient composition is presented in Table 2. The analyzed concentrations of the Cu, Zn, and Mn were very close to the targeted concentrations, except total Zn for the COMBO and HYD treatments was lower than expected, which cannot be explained and may be due to analytical error. Additionally, daily records maintained by the research site showed actual TM premix usages for the entire study were 100.40, 99.99, and 100.35% of the theoretical usage for CON, COMBO, and HYD, respectively.
Treatment1 Item
CON
COMBO
HYD
DM, % as fed CP, % NPN, % Fat, % Calcium, % Phosphorous, % Potassium, % Sulfur, % Cobalt, mg/kg Copper, mg/kg Iodine, mg/kg Iron, mg/kg Manganese, mg/kg Molybdenum, mg/kg Selenium, mg/kg Zinc, mg/kg
75.59 12.69 2.45 6.27 0.70 0.27 0.66 0.13 <0.20 11.78 7.43 102.52 32.97 <0.30 0.33 61.85
75.57 12.59 2.44 6.31 0.68 0.27 0.67 0.12 <0.20 10.76 8.06 92.23 27.83 <0.30 0.34 98.97
75.56 12.66 2.44 6.27 0.67 0.27 0.65 0.12 <0.20 11.47 9.04 86.83 25.92 <0.30 0.34 98.93
Treatments: CON = 10.6 mg/kg of Cu (72.2% Cu sulfate and 27.8% Cu AA complex), 37.8 mg/kg of Zn (77.6% Zn sulfate and 22.4% Zn AA complex), and 25.5 mg/kg of Mn (81.6% Mn sulfate and 18.4% Mn AA complex); COMBO = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate and 33% Zn methionine), and 20 mg/ kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride); HYD = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride).
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Heldt and Davis: Zinc source and level on finishing performance
(P ≥ 0.50) in final BW, ADG, DMI, and G:F in yearling steers fed for 173 d when comparing a blend of 75% sulfate and 25% AAC Cu and Zn to 100% hydroxychloride trace minerals at an iso-level or a 40% reduced level. Additionally, Caldera et al. (2016) reported no differences (P ≥ 0.22) in final BW, DMI, ADG, and G:F when comparing an all-sulfate trace mineral program to 100% hydroxychloride trace minerals fed at an iso-level or multiple titrated reduced levels. Berrett et al. (2015) reported similar (P ≥ 0.26) live performance in steers fed no supplemental TM or 10, 30, and 20 mg/kg of Cu, Zn, Mn, respectively, from sulfate sources; 20, 100, and 50 mg/kg from sulfate sources; or 20, 100, and 50 from 66.6% sulfate and 33.4% organic sources (Cu AAC, Zn AAC, and Mn proteinate, respectively). Ahola et al. (2005) reported in a 2-yr study similar (P ≥ 0.75) final BW and ADG in steers and heifers receiving no added TM or added Cu, Zn, and Mn from sulfates or 67% sulfate/33% proteinate to meet NRC requirements. However, added TM tended to increase DMI (P = 0.10), and there was a treatment × year interaction for G:F: added TM increased G:F compared with control (P = 0.01) in yr 1 and the sulfate–organic combination increased G:F compared with sulfates (P = 0.04) in yr 2. Rhoads et al. (2003) also compared Cu, Zn, and Mn sulfates and AAC sources at different levels relative to NRC requirements and reported that source or level did not (P > 0.05) affect final BW or overall ADG or DMI, but AAC fed at 1× NRC had lower (P < 0.05) G:F than higher levels of sulfates but was similar to 1.5× NRC from AAC. Hill et al. (1996) concluded there was no difference (P ≥ 0.21) in live performance of steers receiving no supplemental TM compared with those supplemented with Cu,
Zn, and Mn sulfates or metal-specific AAC (MSAAC), but there was a tendency for MSAAC to reduce DMI (P = 0.08). Recently, Van Bibber-Krueger et al. (2019) showed no differences (P ≥ 0.29) in final BW and ADG in heifers supplemented with 0, 30, 60, or 90 mg/kg of Zn from Zn sulfate (basal diet = 51 mg/kg of Zn). However, increasing Zn concentration tended to decrease (linear effect, P = 0.07) DMI, resulting in a linear (P = 0.03) improvement in feed efficiency. Genther-Schroeder et al. (2018) reported no differences (P ≥ 0.16) in live performance of beef steers comparing no supplemental Zn (30 mg/kg from basal diet) with 60 mg/kg of added Zn sulfate or the 60 mg/kg of Zn sulfate plus an additional 60, 125, or 150 mg/kg of Zn AAC. Additionally, there was no difference (P ≥ 0.16) in live performance to increasing level of Zn AAC. In a similar study, Genther-Schroeder et al. (2016) reported no differences (P ≥ 0.80) during the preractopamine feeding period in final BW, ADG, and G:F between 60 mg/kg of Zn sulfate and 60 mg/kg of Zn sulfate plus 30, 60, or 90 mg/kg of added Zn AAC, but added Zn AAC tended (P = 0.08) to reduce DMI. During the ractopamine feeding period all live performance variables were similar (P ≥ 0.65) between control and Zn supplementation. However, during the final 28 d, increasing Zn AAC linearly increased (P ≤ 0.03) ADG and G:F in steers supplemented with ractopamine but not in those not receiving ractopamine. Montano et al. (2017) reported no differences (P ≥ 0.23) in final BW, ADG, and feed efficiency of Holstein steers when evaluating Zn sulfate (20 mg/kg), Zn betaine (20 mg/kg), a 50:50 combination of Zn sulfate:Zn betaine (20 mg/kg), and Zn sulfate (40 mg/kg). However, there was a linear (P
Table 3. Effects of supplemental Zn source and level on live performance and feed efficiency of feedlot seers Treatment1
Contrast (P =)
Item
CON
COMBO
HYD
SEM
CON vs. COMBO and HYD
COMBO vs. HYD
Pens No. of steers Initial BW, kg Final BW,2 kg DMI, kg ADG, kg Feed conversion
8 568 297.5 559.2 7.9 1.39 5.7
8 568 295.2 555.1 7.9 1.39 5.8
8 571 297.1 564.2 8.0 1.42 5.6
1.15 6.63 0.04 0.024 0.04
0.35 0.97 0.36 0.74 0.91
0.23 0.34 0.74 0.36 0.30
Treatments: CON = 10.6 mg/kg of Cu (72.2% Cu sulfate and 27.8% Cu AA complex), 37.8 mg/kg of Zn (77.6% Zn sulfate and 22.4% Zn AA complex), and 25.5 mg/kg of Mn (81.6% Mn sulfate and 18.4% Mn AA complex); COMBO = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate and 33% Zn methionine), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride); HYD = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride). 2 Final BW was shrunk (applied 4% pencil shrink on actual BW).
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= 0.11) and quadratic (P = 0.06) tendency for Zn betaine to decrease DMI. In another Zn study, Malcolm-Callis et al. (2000) reported no differences (P > 0.10) in final BW, overall DMI, ADG, and G:F in steers fed either Zn sulfate, Zn AAC, or Zn polysaccharide complex sources of supplemental Zn and 20, 100, or 200 mg/kg of added Zn from Zn sulfate.
Health Outcomes There were no differences (P ≥ 0.28) in any of the health outcomes: morbidity, mortality, repulls, or treatment days (Table 4). This may be partially explained by the fact that all cattle received very similar TM levels, including zinc for the first 45 d on feed when health issues are expected to be highest. Unfortunately, most feedlot finishing studies evaluating trace mineral programs fail to report health outcomes; therefore, there is limited data for similar comparisons with this study. However, Hilscher et al. (2019) found no differences (P ≥ 0.42) in morbidity, death loss, or foot rot incidence when feeding 19 mg/kg of Cu and 108 mg/kg of Zn from sulfate plus zinc methionine (ZnMet) compared with iso-levels from Cu and Zn hydroxychloride sources in finishing steers. Rhoads et al. (2003) reported a similar result for morbidity, with no differences (P > 0.05) between Cu, Zn, and Mn sulfates fed at 3× or 6× NRC requirements and AAC fed at 1× and 2× NRC requirements in finishing steers. Similarly, Ahola et al. (2005) reported no difference (P > 0.10) in number of cattle treated or re-treated for respiratory disease in a
2-yr study evaluating no added TM or TM from sulfates or a 50:50 sulfate:proteinate combination at NRC requirements. Grotelueschen et al. (2001) reported that feeding free-choice mineral mixes with Cu, Zn, and Mn AAC close to NRC requirements resulted in 49 and 56.9% fewer (P < 0.05) sick incidents in the feedlot compared with no supplemental TM or a sulfate-based mineral at approximately 2× NRC requirements, respectively. However, feedlot mortality was the same (P > 0.05). Galyean et al. (1995) reported that 35 or 70 mg/kg of added Zn from Zn sulfate or ZnMet nor added Cu lysine affected live performance or morbidity in a 28-d receiving period (P > 0.10). However, during the step-up periods to the finishing diet, the percentage of morbid steers was reduced (P < 0.07) by 70 mg/kg of added Zn from Zn sulfate or ZnMet compared with 30 mg/kg from ZnO and 35 mg/kg of ZnMet. Finally in the same study, 161-d finishing-period ADG, feed efficiency, and carcass measurements were unaffected (P > 0.10) by supplemental Zn source or level. Two studies evaluating sulfates, AAC, and hydroxychloride sources fed at the same rates (approximate NRC requirements) reported similar (P ≥ 0.43) morbidity in steers (Ryan et al., 2015) and heifers (Weibert et al., 2017) in receiving/ backgrounding programs.
Carcass Characteristics There were no differences (P ≥ 0.32) in HCW, DP, backfat thickness, or liver abscesses (Table 5). However, HCW distribution was significantly different (P = 0.05) in CON
Table 4. Effects of supplemental Zn source and level on health variables Treatment1 Item
CON
No. of steers 568 No. of steers pulled 164 Morbidity, % 28.5 No. of steers repulled 72 Repull, % 43.7 No. dead 38 Mortality, % 6.5 Total treatment days2 286 Average treatment days3 1.7
Contrast (P =)
COMBO
HYD
CON vs. COMBO vs. HYD SEM COMBO and HYD
568 177 31.2 86 48.6 44 7.5 313 1.7
571 176 30.9 80 45.3 35 6.0 303 1.7
1.25 1.85 2.69 1.03 2.76 0.07
0.28 0.35 0.83 0.43 0.93
0.89 0.40 0.33 0.75 0.46
Treatments: CON = 10.6 mg/kg of Cu (72.2% Cu sulfate and 27.8% Cu AA complex), 37.8 mg/kg of Zn (77.6% Zn sulfate and 22.4% Zn AA complex), and 25.5 mg/kg of Mn (81.6% Mn sulfate and 18.4% Mn AA complex); COMBO = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate and 33% Zn methionine), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride); HYD = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride). 2 Total treatment days = the number of days an antibiotic was administered. 3 Average treatment days = total treatment days divided by number of animals pulled at least one time. 1
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Heldt and Davis: Zinc source and level on finishing performance
versus COMBO and HYD. The CON had fewer 430.8- to 453.1-kg carcasses (9.40% vs. 11.69 and 14.33%, respectively). The CON also tended to have fewer (P = 0.14) 453.5- to 475.5-kg carcasses compared with COMBO and HYD (4.37% vs. 5.90 and 6.56%, respectively). There was a tendency for HYD to have a higher (P = 0.10) calculated YG and smaller (P = 0.14) LM area compared with COMBO. Marbling score also tended to be lower (P = 0.13) in CON compared with COMBO and HYD. Last, there were no differences (P ≥ 0.16) in USDA QG and YG distribution or percentage dark cutters (Table 6). There are conflicting results within the literature on the effect of TM source and level on carcass responses; studies have shown improvement (Genther-Schroeder et al., 2016; Wagner et al., 2016; Montano et al., 2017), decline (Rhoads et al., 2003; Berrett et al., 2015), or no differences (Hill et al., 1996; Ahola et al., 2005; Caldera et al., 2016) in carcass performance with different supplemental TM programs. Similar to this study, Wagner et al. (2016) reported no differences (P ≥ 0.17) in HCW, DP, backfat thickness, KPH, YG, LM area, marbling score, and liver abscesses when comparing a blend of 75% Cu and Zn sulfate and 25% Cu and Zn AAC to 100% hydroxychloride trace minerals at either an iso-level or a 40% reduced level. However, there was a tendency (P = 0.12) for the hydroxychloride Cu and Zn treatments to improve percentage of choice or greater
carcasses. Caldera et al. (2016) reported no differences (P ≥ 0.19) in HCW, DP, backfat thickness, KPH, YG, LM area, and marbling score when comparing an all sulfate TM program to 100% hydroxychloride TM fed at either an iso-level or multiple reduced levels. Berrett et al. (2015) reported no differences (P ≥ 0.20) in HCW, DP, backfat thickness, KPH, LM area, marbling score, and liver abscesses when comparing no supplemental TM to 2 levels of Cu, Zn, and Mn sulfates or a sulfate–organic combination. They did however report that the QG distribution was affected by TM program; the sulfate–organic program increased the percentage select carcasses (P = 0.02) 50.00 versus 27.7% compared with all sulfates when fed at 20 mg/kg of Cu, 100 mg/kg of Zn, and 50 mg/kg of Mn. In a 2-yr study in finishing steers and heifers, Ahola et al. (2005) reported no affect (P ≥ 0.20) on carcass traits when comparing no supplemental TM to Cu, Zn, and Mn sulfates and sulfate–proteinate combination. Rhoads et al. (2003) reported extremely mixed results for carcass characteristics when evaluating Cu, Zn, and Mn AAC and sulfates at different levels. They found HCW, YG, and KPH were similar (P > 0.05); however, 1.5× NRC from sulfates and AAC had lower (P < 0.05) DP than 1× AAC and 3× sulfate. Sulfates fed at 3× had smaller (P < 0.05) LM area than 1.5× sulfate but similar to both AAC levels. Backfat thickness was less (P < 0.05) in the 1.5× AAC treatment
Table 5. Effects of supplemental Zn source and level on carcass characteristics and liver abscesses of feedlot steers Treatment1
Contrast (P =)
Item
CON
COMBO
HYD
n HCW, kg HCW distribution, % <249.4 kg 430.8 to 453.1 kg 453.5 to 475.7 kg >476.2 kg DP Calculated YG LM area, cm2 (LM area/HCW) × 100 Backfat thickness, cm Marbling score2 Liver abscesses, %
499 397.7 0.00 9.40 4.37 2.94 64.5 2.7 98.8 1.8 1.50 461.6 32.0
496 398.2 0.17 11.69 5.90 2.64 64.5 2.7 100.0 1.8 1.50 470.6 33.6
507 398.6 0.00 14.33 6.56 2.72 64.5 2.8 98.4 1.8 1.55 469.5 29.9
CON vs. COMBO vs. HYD SEM COMBO and HYD 1.81 0.10 1.35 0.98 0.62 0.09 0.05 0.77 0.01 0.025 4.30 3.96
0.78 0.49 0.05 0.14 0.74 0.85 0.65 0.68 0.86 0.38 0.13 0.95
0.83 0.24 0.19 0.64 0.93 0.89 0.10 0.14 0.37 0.32 0.86 0.52
Treatments: CON = 10.6 mg/kg of Cu (72.2% Cu sulfate and 27.8% Cu AA complex), 37.8 mg/kg of Zn (77.6% Zn sulfate and 22.4% Zn AA complex), and 25.5 mg/kg of Mn (81.6% Mn sulfate and 18.4% Mn AA complex); COMBO = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate and 33% Zn methionine), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride); HYD = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride). 2 Marbling score: 300 = Slight0, 400 = Small0, 500 = Modest0.
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Nutrition
Table 6. Effects of supplemental Zn source and level on categorical carcass characteristics of feedlot steers Treatment1
Contrast (P =)
Item
CON
COMBO
HYD
SEM
CON vs. COMBO and HYD
COMBO vs. HYD
n QG distribution,2 % Prime Choice Select Standard YG distribution,2 % YG 1 YG 2 YG 3 YG 4 YG 5 Total dark cutters, %
499 1.4 76.6 22.1 0.0 22.1 44.3 26.3 6.6 0.8 0.0
496 2.5 75.8 21.5 0.2 22.2 42.0 28.1 6.7 1.0 0.6
507 2.0 75.0 22.2 0.0 21.9 39.4 29.2 9.1 0.4 0.2
0.56 1.62 1.51 0.10 1.26 2.95 2.18 1.31 0.37 0.22
0.22 0.71 0.90 0.49 0.98 0.34 0.38 0.44 0.82 0.16
0.58 0.99 0.77 0.24 0.87 0.54 0.72 0.21 0.25 0.19
Treatments: CON = 10.6 mg/kg of Cu (72.2% Cu sulfate and 27.8% Cu AA complex), 37.8 mg/kg of Zn (77.6% Zn sulfate and 22.4% Zn AA complex), and 25.5 mg/kg of Mn (81.6% Mn sulfate and 18.4% Mn AA complex); COMBO = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (67% Zn sulfate and 33% Zn methionine), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride); HYD = 10 mg/kg of Cu (100% basic copper chloride), 90 mg/kg of Zn (100% Zn hydroxychloride), and 20 mg/kg of Mn (75% Mn sulfate and 25% Mn hydroxychloride). 2 USDA grades were assigned by USDA graders as reported by the packing plant; distributions represent the percentage of carcasses assigned a given grade.
1
compared with 1× AAC and 3× sulfate but similar to 1.5× sulfate. Finally, marbling score in 1× AAC was lower (P < 0.05) than 1.5× AAC but similar to both sulfate levels. Similarly, Hill et al. (1996) reported no differences (P ≥ 0.20) in carcass traits between unsupplemented steers and steers receiving Cu, Zn, and Mn MSAAC and sulfates, but there was a tendency for control steers to have less KPH (P = 0.06) than TM fed steers and for sulfates to increase backfat thickness (P = 0.14) and YG (P = 0.13) compared with MSAAC. Multiple Zn source and level studies have yielded quite variable results. Recently, Van Bibber-Krueger et al. (2019) reported no differences (P > 0.53) in carcass characteristics with increasing supplemental Zn from Zn sulfate at 0, 30, 60, or 90 mg/kg, but there was a tendency for a quadratic effect (P = 0.07) on carcasses that graded prime, which peaked at 60 mg/kg of Zn. GentherSchroeder et al. (2018) also reported similar (P ≥ 0.18) carcass traits between no supplemental Zn, 60 mg/kg of Zn sulfate, or 60 mg/kg of Zn sulfate plus 60, 120, or 150 mg/kg of Zn AAC except all added Zn treatments had a lower (P = 0.03) marbling score compared with no added Zn. In a similarly designed trial, Genther-Schroeder et al. (2016) reported similar (P ≥ 0.65) carcass results when feeding 60 mg/kg of Zn sulfate and 60 mg/kg of Zn sulfate plus 30, 60, 90 mg/kg of Zn AAC except added Zn
AAC decreased backfat thickness (P = 0.04) and tended to increase LM area (P = 0.14), therefore decreasing YG (P = 0.04). Montano et al. (2017) also reported mostly similar (P ≥ 0.35) carcass traits in Holstein steers when comparing Zn sulfate, Zn betaine, and Zn sulfate/Zn betaine combination except there was tendency for 40 mg/ kg of Zn sulfate to increase DP (P = 0.14) and decrease KPH (P = 0.13). Malcolm-Callis et al. (2000) reported no difference (P > 0.10) in HCW, DP, LM area, KPH, and marbling score in steers fed Zn sulfate at 20, 100, and 200 mg/kg, but there was a quadratic (P < 0.05) effect of Zn level on backfat thickness and YG.
APPLICATIONS Under the conditions of this experiment, all supplemental treatments, regardless of source or level, appeared to have effectively met the Zn requirements for feedlot steers, resulting in no differences between treatments. The lack of performance, health, and carcass differences provide additional evidence that supplemental Zn fed in excess of NASEM (2016) requirements may not be warranted and may be supplemented at lower concentrations than those reported by feedlot nutritionists (Samuelson et al., 2016) without adversely affecting live or carcass performance. Additionally, if higher levels of supplemental Zn are to be
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fed, supplemental TM costs become an important factor in determining which TM program to use because of the lack of performance differences noted between sources.
Hilscher, F. H., S. B. Laudert, J. S. Heldt, R. J. Cooper, B. D. Dicke, D. J. Jordon, T. L. Scott, and G. E. Erickson. 2019. Effect of copper and zinc source on finishing performance and incidence of foot rot in feedlot steers. Prof. Anim. Sci. 35:94–100.
ACKNOWLEDGMENTS
Leisure, N. J., C. C. Jackson, M. Huang, T. B. Moore, and F. A. Stewart. 2014. Micronutrient supplement. Heritage Technologies LLC, assignee. US Pat. No. 8,802,180 B2.
Funding was provided by Micronutrients USA LLC (Indianapolis, IN).
LITERATURE CITED
Malcolm-Callis, K. J., G. C. Duff, S. A. Gunter, E. B. Kegley, and D. A. Vermeire. 2000. Effects of supplemental zinc concentration and source on performance, carcass characteristics, and serum values in finishing beef steers. J. Anim. Sci. 78:2801–2808. https://doi.org/10 .2527/2000.78112801x.
Ahola, J. K., L. R. Sharpe, K. L. Dorton, P. D. Burns, T. L. Stanton, and T. E. Engle. 2005. Effects of lifetime copper, zinc, and manganese supplementation and source on performance, mineral status, immunity, and carcass characteristics of feedlot cattle. Prof. Anim. Sci. 21:305–317. https://doi.org/10.2527/jas.2014-8661.
Montano, M. F., A. Plascencia, J. Salinas-Chavira, N. Torrentera, and R. A. Zinn. 2017. Influence of level and form of supplemental zinc on feedlot growth performance and carcass characteristics of calf-fed Holstein steers. Prof. Anim. Sci. 33:651–658. https://doi.org/10.15232/ pas.2017-01640.
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