Effects of feeding sulfate trace minerals above recommendations on nutrient digestibility, rumen fermentation, lactational performance, and trace mineral excretion in dairy cows

Most trace minerals (TM) are fed above dairy cow requirements in commercial herds but their fate and effects on dairy cows have not been well documented. In this study, we evaluated the effects of feeding short-term sulfate TM above recommendations on apparent total-tract digestibility of nutrients, rumen fermentation characteristics, serum concentrations, milk yield and composition as well as milk, fecal, and urinary TM excretion in mid-lactation dairy cows. Eight multiparous Holstein cows [average body weight: 684 (SD: 29) kg at 82 (SD: 10) days in milk] in a quadruple 2 × 2 crossover design were fed a basal diet, differing in sulfate TM supplement concentrations, to provide either 0.11, 17, and 63 (control; CON) or 0.95, 114, and 123 (high trace minerals; HTM) mg of dietary Co, Mn, and Zn/kg of dry matter, respectively. Each experimental period had a 21-d adaptation to the diet, followed by a 10-d sample collection period. Feed ingredients and total feces and urine were collected during 4 consecutive d and rumen fluid was collected 0, 1, 2, 4, and 6 h relative to feeding. Milk yield was recorded daily and milk samples were collected on 4 consecutive milkings. Ingestion of Co, Mn, and Zn was higher for HTM compared with CON group by 216, 233, and 93%, respectively. Dry matter intake averaged 25.0 (SE = 0.6) kg/d, and apparent total-tract digestibility of major nutrients was similar between treatments. There was no measurable effect of HTM on ruminal pH, major volatile fatty acids, and protozoa counts. Isovalerate molar proportion was 9.4% greater for HTM compared with CON group. Neither milk yield (43.5 kg/d; SE = 0.8) nor milk fat and protein concentrations differed between treatments. Milk urea nitrogen concentration was significantly higher for HTM (11.7 mg/dL) compared with CON group (9.7 mg/dL; SE = 0.7). Fecal excretion of Co, Mn, and Zn increased by 223, 198, and 75%, respectively, for HTM compared with CON group. Urinary excretions of TM were marginal compared with feces, and only urinary Co and Mn were significantly higher for HTM than CON cows as similarly obtained for serum Co and Mn concentrations. Milk TM yields were not modified by treatments. In summary, short-term dietary sulfate TM supply over the recommendation did not improve cow performance but significantly increased fecal TM excretion, which could have impacts on TM accumulation in soils where manure is applied and could potentially result in leaching into nearby watersheds. Further studies are needed to evaluate the impact of high fecal TM excretion on the environment using the One Health approach. Moreover, the impacts of TM oversupply on milk production and cow health should be evaluated by long-term experiments.

Evaluation of Trace Mineral Sources

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

Effect of replacing a portion of inorganic chloride trace minerals with trace mineral amino acid complexes

The objective was to determine whether replacing a portion of inorganic chloride trace minerals and cobalt carbonate in the diet with AA complexes of trace minerals and cobalt glucoheptonate will improve lactating cow performance, feed efficiency, and calf performance. In a clinical trial, 69 Holstein cows entering second lactation and greater were randomly assigned to 1 of 2 treatments, with the total dietary trace mineral concentration the same between treatments, starting 1 wk after dry off (50 to 57 d before expected parturition) until 154 d in milk (DIM): (1) an inorganic chloride trace mineral (ITM) blend consisting of Zn (75 mg/kg), Mn (65 mg/kg), and Cu (10 mg/kg) as hydroxychlorides and Co (1 mg/kg) as carbonate (n = 37) or (2) partial replacement of ITM with AA complexes of Zn (40 mg/kg), Mn (20 mg/kg), and Cu (3.5 mg/kg) and Co glucoheptonate (1 mg/kg; AATM; Availa-Dairy, Zinpro Corp.; n = 32). Dry matter intake (DMI) was recorded daily from enrollment through wk 8, and milk yields were recorded daily from calving through wk 22. Milk composition and body weights (BW) were collected weekly. Serum samples were analyzed for albumin (Alb), cholesterol (Chol), total bilirubin (Bili), aspartate aminotransferase (AST), haptoglobin, β-hydroxybutyrate (BHB), and Ca. A liver health index (LHI) was calculated based on Bili, Chol, and Alb concentrations. A liver functionality index (LFI) was calculated to standardize changes in Alb, Chol, and Bili from 4 to 29 DIM. Greater LHI and LFI indicate better health status. Colostrum was analyzed for IgG and Brix, and calf serum was analyzed for IgG. Calf growth was monitored through 9 wk of age (AATM: n = 12, ITM: n = 10). Data were analyzed using SAS software with mixed effects models and repeated-measures analysis, when applicable. Survival analysis for pregnancy by 154 DIM was analyzed by Cox proportional and Kaplan-Meier hazards models. Disorder incidence was tested with Fisher's exact test. Prepartum DMI as a percent of BW was lower in cows fed AATM and not significant postpartum. Cows fed AATM produced more milk from wk 1 to 8 and from wk 1 to 22. Energy-corrected milk yield and colostrum measures did not significantly differ between treatments. A treatment by time interaction was seen for AST and BHB; cows fed AATM tended to have lower AST concentrations at 28 DIM and lower concentrations in BHB through 29 DIM, though not statistically significant. Cows fed AATM had greater LHI at 4 DIM. Haptoglobin, Ca, LFI, hazard of pregnancy, risk to first service, survival curves, or services per pregnancy did not significantly differ. Calf serum IgG and birth weight did not significantly differ between treatments. Calves from dams fed AATM had greater average daily gain than calves from dams fed ITM. Overall, cows fed AATM during the dry period and early lactation had improved postpartum performance and potential health improvements.

Evaluation of trace elements in forages and their effect on gastrointestinal parasite burden in grazing sheep

This study was designed to evaluate the trace elements (minerals) in forages fed to sheep and their effect on gastrointestinal parasite burdens. The ultimate objective was to determine the correlation between the burden of gastrointestinal (GI) parasites and the level of trace minerals in sheep serum as a result of the forages they grazed on. A total of 384 faecal samples were collected from sheep in each of the districts (Sialkot and Multan) and examined quantitatively using the McMaster technique. Serum collected from them and plants were pre-treated, and spectrophotometry was used to determine the concentration of trace minerals (Mn, Co, Cu, and Zn). The level of these trace elements differed significantly (P < 0.05) in forages from both districts. In the district of Sialkot, the highest concentrations (mg/Kg) of Zn (38.53 ± 0.16) were found in Cichorium intybus, Cu (41.57 ± 0.07) in Cynodon dactylon, Mn (39.61 ± 0.05) in Parthenium hysterophorus, and Co (1.42 ± 0.03) in Coronopus didymus. In the district of Multan, the highest concentrations (mg/Kg) of Zn (39.43 ± 0.46) were found in Cichorium intybus, Cu (25.76 ± 0.36) in Cynodon dactylon, Mn (34.29 ± 0.53) in Launaea nudicaulis, and Co (1.74 ± 0.08) in Brachiaria raptens. The prevalence of GI parasites in sheep populations in district Sialkot was 34%, while in district Multan, it was 32%. In tehsil Sialkot of district Sialkot, Zn and Cu were significantly (P < 0.05) correlated with eggs per gram (EPG) of faeces, while in tehsil Multan City of district Multan, only Cu was significantly (P < 0.05) correlated with EPG. The potential mechanism behind the role of trace minerals in lowering the burdens of GI parasites requires more investigation. It is recommended that plants with high content of trace minerals should be utilized as part of comprehensive preventive and control strategies against GI parasitism in ruminant animals like sheep.

Worldwide Research Trends for Chelates in Animal Science: A Bibliometric Analysis

The purpose of this study was to look at research trends in the application of CTM in animal nutrition in order to identify current and emerging challenges, as well as to examine the intellectual structure of the subject. The intellectual structure of CTM was examined using keyword and reference analysis. The research community includes all research and review articles published in journals indexed in the Web of Science database during the years 1990-2022. The results showed that the terms zinc, co-occurring 331 times, performance (324 times), and copper 216 (times) were the main and hotspots of research in the field of chelate. The data suggest that the most important keywords during the study period were zinc, copper, pig, bovine, metabolism, and bioavailability. The terms health, muscle, beef, trace elements, and dietary supplements represent emerging topics in CTM, as research began to focus on these areas during the years 2017-2022. The country with the greatest number of published articles was the United States of America. This bibliometric analysis showed that countries are focusing on the effects of CTM on the health and musculature of cattle through dietary supplementation with trace elements. According to the identified hot and emerging topics, this research can serve as a roadmap for a global comprehensive scientific plan and policy.

Effects of different manganese sources on nutrient digestibility, fecal bacterial community, and mineral excretion of weaning dairy calves

Introduction

Mn, which is an essential trace mineral for all animals, has functions in skeletal system development, carbohydrate and lipid metabolism. The aim of this study was to clarify the effects of different manganese (Mn) sources in basal diets on nutrient apparent digestibility, fecal microbes, and mineral elements excretion before and after weaning.

Methods

A total of 15 Holstein heifer calves (6-week-old, 82.71 ± 1.35, mean ± standard error) were randomly designed into three groups (five each): no extra Mn supplemented (CON), 20 mg Mn/kg (dry matter basis) in the form of chelates of lysine and glutamic acid in a mixture of 1:1 (LGM), and 20 mg Mn/kg (dry matter basis) in the form of MnSO₄. All calves were weaned at 8 weeks of age. The experiment lasted for 28 days (14 days before weaning and 14 days after weaning). Dry matter intake (DMI) was recorded daily. The animals were weighed by electronic walk-over, and body size indices were collected using tape on days -14, -1, and 14 of weaning. The feces of calves was collected to measure the apparent digestibility of nutrients (acid insoluble ash was an internal marker) and bacterial community on days -1, 1, 3, 7, and 14 of weaning. Fecal mineral concentration was determined by inductively coupled plasma emission spectroscopy on days -1, 1, 7, and 14 of weaning.

Results

The results showed that, compared with the CON group, adding LGM to diets containing 158.82 mg/kg Mn increased the apparent digestibility (P < 0.05). The Chao 1 and Shannon index of fecal bacteria decreased at day 1 in the LGM and MnSO₄ groups and increased after weaning. The PCoA results indicated that the LGM group was distinctly separate from the CON and MnSO₄ groups during the whole experimental period. Significant differences (P < 0.05) were observed in the relative abundance of two phyla (Proteobacteria and Spirochaetota) and eight genera (Alloprevotella, Prevotellaceae_UCG-001, Clostridia UCG 014, RF39, UCG-010, Pseudomonas, Ralstonia, and Treponema) in three groups. Moreover, the LGM group showed less excretion of Fe, P, and Mn than the MnSO₄ group.

Discussion

In summary, 20 mg Mn/kg diet supplementation improved nutrient digestibility, changed the fecal microbial community, and reduced mineral excretion. Organic Mn supplementation in the diet had more advantages over the sulfate forms in weaning calves.

Feeding reduced levels of trace minerals in proteinate form and selenium-yeast to transition cows: Performance, trace minerals, and antioxidant status, peripheral neutrophil activity, and oocyte quality

An experiment was conducted to evaluate the effects of inorganic trace minerals (TM) and reduced levels of TM by using proteinate forms of Co, Zn, Mn, and Cu, and Se-yeast in diets of transition cows on performance, TM concentrations in colostrum, plasma, and liver, blood metabolites, antioxidant status, peripheral neutrophil activity, and oocyte quality. Thirty-two Holstein cows (22 multiparous and 10 primiparous cows) were enrolled in this study from 30 d before the expected calving date to 56 DIM. Cows were blocked according to body condition score, parity, and previous milk yield and randomly assigned to one of the following treatments: control (CON), with TM (Zn, Cu, Mn, and Co) supplied in form of sulfate and Se as sodium selenite to meet or exceed requirement estimates of the National Research Council; and proteinate trace minerals (PTM), with TM supplied bound with AA and peptides at 50% of CON levels and inorganic Se replaced with Se-yeast at 100% of CON level. Treatments were supplied until 56 DIM. Eight cows were removed from the study because of early calving (n = 3) or health issues (n = 5); thus, data of 24 cows (16 multiparous and 8 primiparous cows) were used in the statistical analysis. No differences between treatments were detected on nutrient intake or digestibility. Total excretion of purine derivatives was decreased when feeding PTM during the prepartum period. Feeding reduced levels of TM in proteinate form resulted in greater yield of milk (27.7 and 30.9 kg/d for CON and PTM, respectively) and protein (0.890 and 0.976 kg/d) between wk 5 and 8 of lactation. No treatment differences were detected for feed efficiency, milk somatic cell count, and milk urea nitrogen. Cows fed PTM had lower milk fat concentration during the 56 d of evaluation (4.08 and 3.74% for CON and PTM, respectively). Selenium concentration was greater in colostrum of cows fed PTM compared with CON (48.5 and 71.3 µg/L for CON and PTM, respectively), whereas Zn, Cu, and Mn concentrations were not different. Cows fed PTM showed lower liver Cu concentration compared with CON (51.4 and 73.8, respectively). Plasma concentrations of Mn and Zn were lower, but plasma Se concentration tended to be higher with PTM treatment. Feeding PTM resulted in greater blood concentrations of urea-N (16.6 and 18.2 mg/dL for CON and PTM, respectively) and β-hydroxybutyrate (0.739 and 0.940 mmol/L). Counts of lymphocytes were higher with PTM but counts of monocytes were lower in complete blood cell count. No differences were observed in serum concentrations of superoxide dismutase and glutathione peroxidase. No differences were detected in phagocytosis and oxidative burst potential of neutrophils after incubation with bacteria. Cows fed PTM had fewer viable oocytes per ovum pick-up in comparison with CON (8.00 and 11.6). Feeding PTM to transition cows may sustain performance without altering neutrophil activity despite some alterations in blood TM concentrations. More studies should be performed to evaluate production and fertility measurements when reducing TM dietary levels by using proteinate forms and Se-yeast with larger number of animals.

Meta-analysis of the effects of sulfate versus hydroxy trace mineral source on nutrient digestibility in dairy and beef cattle

Trace mineral (TM) source can potentially alter nutrient digestibility through effects on microbial populations. A meta-analysis was conducted to determine whether sulfate versus hydroxy (IntelliBond) sources of supplemental Cu, Zn, and Mn had any effect on dry matter intake (DMI), dry matter digestibility, and neutral detergent fiber (NDF) digestibility. All available cattle studies (8 studies, 12 comparisons) were used to estimate the effect size (hydroxy mean - sulfate mean). Factors included in the analysis were method of digestibility analysis (total collection, marker-based, or 24 h in situ), study design (randomized design or Latin square), beef (n = 5) versus dairy (n = 7) cattle, and days on treatment; these factors were retained when P < 0.05. Dry matter digestibility was increased by hydroxy TM in beef (1.64 ± 0.35 units) but not in dairy models (0.16 ± 0.13 units) relative to sulfate TM. The NDF digestibility increased significantly with hydroxy versus sulfate TM, but digestibility assessment method influenced this response. Studies using total collection or undigested NDF as a flow marker showed a significant increase (2.68 ± 0.40 units and 1.08 ± 0.31 units, respectively) in NDF digestibility for hydroxy versus sulfate TM; but studies utilizing 24-h in situ incubation did not detect any change (-0.03 ± 0.23 units). These observations may reveal differences in precision of measurement or may indicate mineral effects beyond the rumen; total collection is considered the gold standard method. Hydroxy TM did not affect DMI per animal or per unit of body weight relative to sulfate TM. In conclusion, feeding hydroxy versus sulfate TM does not appear to affect DMI but, depending on type of cattle and method of measurement, can increase dry matter digestibility and NDF digestibility, which may be explained by differences in solubility of the TM sources in rumen, differentially affecting fermentation.

Comparison of coated and uncoated trace elements on growth performance, apparent digestibility, intestinal development and microbial diversity in growing sheep

The suitable supplement pattern affects the digestion and absorption of trace minerals by ruminants. This study aimed to compare the effects of coated and uncoated trace elements on growth performance, apparent digestibility, intestinal development and microbial diversity in growing sheep. Thirty 4-month-old male Yunnan semi-fine wool sheep were randomly assigned to three treatments (n = 10) and fed with following diets: basal diet without adding exogenous trace elements (CON), basal diet plus 400 mg/kg coated trace elements (CTE, the rumen passage rate was 65.87%) and basal diet plus an equal amount of trace elements in uncoated form (UTE). Compared with the CON group, the average daily weight gain and apparent digestibility of crude protein were higher (P < 0.05) in the CTE and UTE groups, while there was no difference between the CTE and UTE groups. The serum levels of selenium, iodine and cobalt were higher (P < 0.05) in the CTE and UTE groups than those in the CON group, the serum levels of selenium and cobalt were higher (P < 0.05) in the CTE group than those in the UTE group. Compared with the CON and UTE groups, the villus height and the ratio of villus height to crypt depth in duodenum and ileum were higher (P < 0.05) in the CTE groups. The addition of trace minerals in diet upregulated most of the relative gene expression of Ocludin, Claudin-1, Claudin-2, ZO-1, and ZO-2 in the duodenum and jejunum and metal ion transporters (FPN1 and ZNT4) in small intestine. The relative abundance of the genera Christensenellaceae R-7 group, Ruminococcus 1, Lachnospiraceae NK3A20 group, and Ruminococcaceae in ileum, and Ruminococcaceae UCG-014 and Lactobacillus in colon was higher in the CTE group that in the CON group. These results indicated that dietary trace mineral addition improved the growth performance and intestinal development, and altered the structure of intestinal bacteria in growing sheep. Compared to uncoated form, offering trace mineral elements to sheep in coated form had a higher absorption efficiency, however, had little effect on improving growth performance of growing sheep.

Effect of zinc source (zinc sulfate or zinc hydroxychloride) on relative abundance of fecal Treponema spp. in lactating dairy cows

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Cows (n = 24) were fed typical lactating diets that only differed in zinc source inclusion.

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Fecal samples collected from cows were extracted for prokaryotic 16S gene DNA.

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Feeding zinc hydroxychloride decreased the Treponema spp. recovered from fecal samples compared with cows fed zinc sulfate.

Previous research revealed a potential effect of dietary trace mineral source on both ruminal and fecal microbiota. However, the effect of Zn source, specifically, has not previously been considered. Based on reported postruminal solubility, we hypothesized that Zn hydroxychloride would decrease Treponema spp. fecal excretion relative to cows fed Zn sulfate. To test this hypothesis, lactating Holstein cows (n = 24; 685 ± 9 kg of body weight; 159 ± 8 d in milk; parity 3 ± 0.2) were randomly assigned to 1 of 2 dietary treatments: control (75 mg/kg Zn from ZnSO₄) or Zn hydroxychloride (HYD; 75 mg/kg IntelliBond Z; Micronutrients USA LLC). Single fecal grab samples were collected on d 1 before dietary treatments and on d 27 after dietary treatments were applied. Fecal microbial DNA was extracted and sequenced to establish taxonomy using a universal primer for the 16S rRNA gene. Supplementation of HYD decreased the relative abundance of Treponema 2 by 3-fold (14.7% vs. 4.9%). Poor sequencing resolution at the species level limited inference of Treponema spp. toward management or gut health implications of HYD supplementation. However, the inclusion of pathogenic species among Treponema spp. indicates a potential implication of HYD feeding to reduce environmental exposure of the dairy cow to Treponema spp.

Effect of Antioxidant Supplementation on Milk Yield and Quality in Italian Mediterranean Lactating Buffaloes

Buffaloes are raised mainly to obtain milk that is nutritionally very rich. The technological characteristics of buffalo milk are optimal for processing into cheese, and it is mainly used to produce mozzarella cheese. Under stressful conditions, buffaloes, like other animals, produce milk qualitatively poorly. The stressors that can affect the quality of production are, in addition to other factors, deficiencies in nutrients such as vitamins, antioxidants, and minerals. In this study, we evaluated the effect of antioxidant supplementation on the quality of buffalo milk. Sixty-six buffaloes were enrolled and subdivided into two balanced groups of 33 each. The ZnSe group received 0.2 kg/head/day of Bufalo Plus® containing antioxidants and barley meal, CaCO3 and MgCO3 mix; the control group was supplemented with 0.2 kg/head/day of barley meal, CaCO3 and MgCO3 mix. The two groups were fed ad libitum with a total mixed ration (TMR). The amount of diet distributed was recorded daily, and the residue in the trough manger was recorded three times per week. TMR samples were taken every two weeks for each group. Daily milk yield was recorded twice a week. Milk samples were collected every four weeks and analysed for chemical and technological properties. Furthermore, milk total antioxidant capacity was determined. The results obtained showed that the antioxidant supplement had no effect on feed intake, feeding behaviour, and feed efficiency. The treatment positively influenced milk production while it did not affect the chemical characteristics of the milk. In addition, the supplement of antioxidants improved the milk clotting properties (MCP). The supplement did not affect the antioxidant activity of the milk.

Effects of replacing inorganic salts of trace minerals with organic trace minerals in pre- and postpartum diets on feeding behavior, rumen fermentation, and performance of dairy cows

Our objectives were to evaluate the effects of complete replacement of supplementary inorganic salts of trace minerals (STM) by organic trace minerals (OTM) in both pre- and postpartum diets on feeding behavior, ruminal fermentation, rumination activity, energy metabolism, and lactation performance in dairy cows. Pregnant cows and heifers (n = 273) were blocked by parity and body condition score and randomly assigned to either STM or OTM diets at 45 ± 3 d before their expected calving date. Both groups received the same diet, except for the source of trace minerals (TM). The STM group was supplemented with Co, Cu, Mn, and Zn sulfates and Na selenite, whereas the OTM group was supplemented with Co, Cu, Mn, and Zn proteinates and selenized yeast. Treatments continued until 156 days in milk and pre- and postpartum diets were formulated to meet 100% of recommended levels of each TM in both treatments, taking into consideration both basal and supplemental levels. Automatic feed bins were used to assign treatments to individual cows and to measure feed intake and feeding behavior. Rumination activity was monitored by sensors attached to a collar from wk -3 to 3 relative to calving. Blood metabolites were evaluated on d -21, -10, -3, 0, 3, 7, 10, 14, 23, and 65 relative to calving. Ruminal fluid samples were collected using an ororuminal sampling device on d -21, 23, and 65 relative to calving, for measurement of ruminal pH and concentration of volatile fatty acids. Cows were milked twice a day and milk components were measured monthly. Cows supplemented with OTM tended to have longer daily feeding time (188 vs. 197 min/d), and greater dry matter intake (DMI; 12.9 vs. 13.3 kg), and had a more positive energy balance (3.6 vs. 4.2 Mcal/d) and shorter rumination time per kg of dry matter (DM; 40.1 vs. 37.5 min/kg of DM) than cows supplemented with STM during the prepartum period. In the postpartum period, OTM increased DMI in multiparous cows (24.1 vs. 24.7 kg/d) but not in primiparous cows (19.1 vs. 18.7 kg/d). The difference in DMI of multiparous cows was more evident in the first 5 wk of lactation, when it averaged 1 kg/d. Milk yield was not affected by treatment in multiparous cows (44.1 vs. 44.2 kg/d); however, primiparous cows supplemented with OTM had lesser yields than primiparous cows supplemented with STM (31.9 vs. 29.8 kg/d). Cows supplemented with OTM had a greater percentage of protein in milk (3.11 vs. 3.17%), reduced concentration of nonesterified fatty acids in serum (0.45 vs. 0.40 mmol/L), and rumination activity (30.1 vs. 27.8 min/kg of DM) than cows supplemented with STM. At the end of the transition period, cows supplemented with OTM had reduced molar proportion of acetate, reduced pH, and tended to have a greater concentration of total volatile fatty acids in ruminal fluid. In conclusion, complete replacement of STM by OTM caused modest changes in rumen fermentation, feeding behavior, energy metabolism, and performance of dairy cows, improving postpartum DMI in multiparous cows and reducing circulating levels of nonesterified fatty acids. The pre-absorptive effects of TM source and the parity specific responses on performance warrant further research.

Effect of zinc sources and experimental conditions on zinc balance in growing wethers

Three experiments were conducted with growing wethers to evaluate apparent excretion and retention of Zn from various sources. In experiments 1 and 2, Zn-ethylene diamine (ZE), Zn hydroxychloride (ZHYD), Zn-lysine/glutamate (ZAA), and Zn-glycinate (ZG) were used and ZnSO₄ (ZS), ZHYD, ZAA, and ZG were used in experiment 3. In experiment 1, eight wethers were used in a replicated 4 × 4 Latin square design. In experiments 2 and 3, 40 wethers were used in a randomized block design. In experiment 1, each period (total four periods) consisted of 14-d diet adaptation and 4 d of total collection of feces and urine. In experiments 2 and 3, wethers received a basal diet for 14 d and received experimental diets for 9 d (diet adaptation), followed by 4 d of total collection of feces and urine. Total collection was conducted in wooden metabolic cages. All data were analyzed using the MIXED procedure of SAS as a Latin square design for experiment 1 and a completed randomized block design for experiments 2 and 3. In all experiments, dry matter intake did not differ among treatments except that it tended to be different in experiment 2. In experiment 1, no difference in Zn excretion (88%) and retention (11%) as proportion of Zn intake was observed among Zn sources. In experiment 2, total tract digestibility of crude protein was greater (P < 0.01) for ZAA than ZE and ZG (82.0% vs. 79.1% and 77.8%, respectively) and greater (P < 0.01) for ZHYD than ZG (80.2% vs. 77.8%). However, total tract digestibility of neutral detergent fiber was low (on average 16%) for all treatments with no difference among treatments in experiment 2. Apparent excretion and retention of Zn as proportion of Zn intake did not differ among treatments, and Zn retention (~1.4% of Zn intake) was very low for all treatments. In experiment 3, ZHYD and ZAA had greater retention of Zn (17.8% vs. 1.5%; P = 0.01) than ZG. Fecal Zn excretion was greater (97.3% vs. 81.2%; P = 0.01) for ZG vs. ZHYD and ZAA, and Zn retention for ZG was only 1.5% of Zn intake. In conclusion, potential increases in Zn absorption and retention were observed for ZHYD and ZAA compared with ZS and ZG in experiment 3 and these differences were not found in experiments 1 and 2. Experiment 1 used a Latin square design and experiment 2 used a diet containing largely undigestible fiber. These experimental conditions may have affected Zn metabolism in wethers. Inconsistent results on Zn balance for ZG among the experiments warrant further studies regarding its bioavailability.

Trace mineral source impacts rumen trace mineral metabolism and fiber digestion in steers fed a medium-quality grass hay diet

Twelve Angus steers (BW 452.8 ± 6.1 kg) fitted with ruminal cannulae were used to determine the impact of trace mineral (TM) source on digestibility, ruminal volatile fatty acid (VFA) composition, ruminal soluble concentrations of Cu, Zn, and Mn, and relative binding strength of trace minerals located in the rumen insoluble digesta fraction. Steers were fed a medium-quality grass hay diet (DM basis: 10.8% CP, 63.1% neutral detergent fiber [NDF], 6.9 mg Cu/kg, 65.5 mg Mn/kg, and 39.4 mg Zn/kg) supplemented with protein for 21 d. Treatments consisted of either sulfate (STM) or hydroxy (HTM) sources (n = 6 steers/treatment) to provide 20, 40, and 60 mg supplemental Cu, Mn, and Zn/kg DM, respectively. Following a 21-d adaptation period, total fecal output was collected for 5 d. Dry matter (P < 0.07) and CP (P < 0.06) digestibility tended to be reduced, and NDF (P < 0.04) and acid detergent fiber (ADF) (P < 0.05) digestibility were reduced in STM- vs. HTM-supplemented steers. On day 6, ruminal fluid was collected at 0, 2, and 4 h post-feeding and analyzed for VFA. There were no treatment x time interactions for VFA. Steers receiving HTM had less (P < 0.02) molar proportions of butyric acid and greater (P < 0.05) total VFA concentrations than STM-supplemented steers. Steers were then fed the same diet without supplemental Cu, Zn, or Mn for 14 d. On day 15 steers received a pulse dose of 20 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either STM or HTM (n = 6 steers/treatment). Ruminal samples were obtained at 2-h intervals starting at -4 and ending at 24 h relative to dosing. There was a treatment x time interaction (P < 0.03) for ruminal soluble Cu, Mn, and Zn concentrations. Ruminal soluble mineral concentrations were greater (P < 0.05) for Cu at 4, 6, 8, 10, 12, and 14 h; for Mn at 4 and 6 h; and for Zn at 4, 6, and 8 h post-dosing in STM compared with HTM-supplemented steers. Copper concentrations were greater (P < 0.05) at 12 and 24 h and Zn concentrations in ruminal solid digesta were greater at 24 h in HTM-supplemented steers. Upon dialysis against Tris-EDTA, the percent Zn released from digesta was greater (P < 0.05) at 12 h (P < 0.03) and 24 h (P < 0.05), and the percent Cu released was greater (P < 0.02) at 24 h post-dosing in HTM steers when compared with STM-supplemented steers. Results indicate that Cu and Zn from HTM have low solubility in the rumen and appear to be less tightly bound to ruminal solid digesta than Cu and Zn from STM. The lower ruminal soluble concentrations of Cu and Zn in steers given HTM were associated with greater fiber digestibility.

Total-tract digestibility and milk productivity of dairy cows as affected by trace mineral sources

The chemical characteristics associated with different sources of Cu, Zn, and Mn such as sulfate, hydroxychloride, or organic chelate may affect the interaction between the metals and other components present within the gut of a ruminant (i.e., microorganisms and nutrients). The present study aimed to evaluate the effect of different supplemental trace mineral strategies on apparent total-tract digestibility, rumen fermentation, and dairy productivity. Using 52 Holstein cows in a replicated 4 × 4 Latin square design with periods of 21 d, 4 treatments differing in their sources of Cu, Zn, and Mn were tested: sulfate form, hydroxychloride form, a mix of sulfate and organic chelate forms (70 and 30%, respectively), and a mix of hydroxychloride and organic chelate forms (70 and 30%, respectively). Treatments were formulated to provide 15, 40, and 20 mg of supplemental Cu, Zn, and Mn, respectively, per kilogram of dry matter. This level of supplementation, together with the basal level present in forages and feed ingredients, resulted in a total average supply of 19, 79, and 84 mg of Cu, Zn, and Mn, respectively, per kilogram of dry matter. Cows had ad libitum access to a total mixed ration, which provided 15.3% of crude protein, 21.7% of starch, and 35.3% of neutral detergent fiber (NDF). Data were summarized by period with trace minerals and period as fixed effects and the repeated cow as random effect using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). Apparent total-tract NDF and crude protein digestibility was reduced (-0.8% and -1.0%, respectively) when organic chelate trace minerals were fed, whereas apparent total-tract NDF digestibility was improved (+0.8%) when sulfate trace minerals were replaced by hydroxychloride trace minerals. Cows supplemented with the hydroxychloride source had lower ruminal butyric acid concentration compared with cows fed sulfate trace minerals (13.3 vs. 14.6%). In addition, fat- and protein-corrected milk and milk fat yields were improved (+1.0 kg/d and +51 g/d, respectively) in multiparous cows when trace minerals were supplemented as hydroxychloride compared with sulfate. These effects were not observed in primiparous cows. These results confirm that trace mineral sources affect apparent total-tract digestibility and indicate that milk productivity may also be affected.

Evaluation of source of corn silage and trace minerals on rumen characteristics and passage rate of Holstein cows

The effects of source of corn silage and trace mineral on rumen fermentation, turnover, and particle passage rates were evaluated with 8 ruminally cannulated Holstein cows averaging 83 (standard error = 5) days in milk in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments and 28-d periods. The diets consisted (dry basis) of 55% conventional (CON) or brown midrib-3 (BM3) corn silage, 2% chopped wheat straw, and 43% grain mix with either sulfate (STM) or hydroxy (HTM) source of Cu, Zn, and Mn trace minerals. The targeted supplemental amount of Cu, Zn, and Mn was 194, 1,657, and 687 mg/d, respectively. The dietary treatments were (1) CON-STM, (2) CON-HTM, (3) BM3-STM, and (4) BM3-HTM. Dietary nutrient composition of BM3 diets averaged 32.1% amylase neutral detergent fiber on an organic matter basis (aNDFom) and 6.9% undigested neutral detergent fiber at 240 h of in vitro fermentation (uNDF240om; % of dry matter), and CON diets averaged 36.2% aNDFom and 8.6% uNDF240om (% of dry matter). Data were summarized by period and analyzed as a replicated Latin square design with fixed model effects for corn silage, trace mineral, corn silage and trace mineral interaction, period within replicated square, and replicated square using the MIXED procedure of SAS (version 9.4, SAS Institute Inc., Cary, NC). Cow within replicate was a random effect. Daily mean, standard deviation, minimum, and maximum for rumen pH were unaffected by corn silage or trace mineral source. Cows fed the CON diets had greater rumen acetate percentage than cows fed the BM3 diets (65.7 vs. 64.7 molar %). In contrast, cows fed the BM3 diets had greater rumen propionate percentage than cows fed the CON diets (21.4 vs. 20.4 molar %). Total volatile fatty acid concentration was lower for cows fed STM versus HTM in BM3 diets, but not for the cows fed the CON diets. Cows fed the BM3 diets had faster turnover rate and shorter turnover time for uNDF240om than cows fed the CON diets (3.12 vs. 2.86%/h and 33.3 vs. 36.5 h, respectively). Cows fed the BM3 diets had a faster passage rate of small and medium corn silage neutral detergent fiber particles than cows fed the CON diets (5.73 vs. 5.37%/h and 4.74 vs. 4.31%/h, respectively). We observed a corn silage by source of trace mineral interaction on organic matter and uNDF240om rumen pool size and organic matter turnover. Overall, source of corn silage had a pronounced influence on rumen dynamics presumably related to greater in vitro neutral detergent fiber digestibility and lower uNDF240om content of BM3 corn silage that allowed for faster turnover of indigestible neutral detergent fiber and greater passage rate of corn silage particles. In contrast, the source of trace mineral had much less significant effects on rumen fermentation, turnover, and particle passage rates. Corn silage-based diets intended to enhance rumen fiber fermentation, turnover, and passage are more affected by source and digestibility of neutral detergent fiber than source of dietary trace minerals.

Copper sulfate and sodium selenite lipid-microencapsulation modifies ruminal microbial fermentation in a dual-flow continuous-culture system

Undesirable interactions between trace mineral elements and ruminal contents may occur during digestion when mineral salts are supplemented. Antimicrobial effects of copper sulfate (CuSO₄) may affect ruminal digestibility of nutrients when fed as a source of copper (Cu), while sodium selenite (Na₂SeO₃) may be reduced in the rumen to less available forms of selenium (Se). Our objective was to evaluate if protection of CuSO₄ and Na₂SeO₃ by lipid-microencapsulation would induce changes on ruminal microbial fermentation. We used 8 fermentors in a dual-flow continuous-culture system in a 4 × 4 duplicated Latin square with a 2 × 2 factorial arrangement of treatments. Factors were CuSO₄ protection (unprotected and protected by lipid-microencapsulation) and Na₂SeO₃ protection (unprotected and protected by lipid-microencapsulation). Treatments consisted of supplementation with 15 mg/kg of Cu and 0.3 mg/kg of Se from either unprotected or protected (lipid-microencapsulated) sources, as follows: (1) Control (unprotected CuSO₄ + unprotected Na₂SeO₃); (2) Cu-P (protected CuSO₄ + unprotected Na₂SeO₃); (3) Se-P (unprotected CuSO₄ + protected Na₂SeO₃); (4) (Cu+Se)-P (protected CuSO₄ + protected Na₂SeO₃). All diets had the same nutrient composition and fermentors were fed 106 g of dry matter/d. Each experimental period was 10 d (7 d of adaptation and 3 d for sample collections). Daily pooled samples of effluents were analyzed for pH, NH₃-N, nutrient digestibility, and flows (g/d) of total N, NH₃-N, nonammonia N (NAN), bacterial N, dietary N, and bacterial efficiency. Kinetics of volatile fatty acids was analyzed in samples collected daily at 0, 1, 2, 4, 6, and 8 h after feeding. Main effects of Cu protection, Se protection, and their interaction were tested for all response variables. Kinetics data were analyzed as repeated measures. Protection of Cu decreased acetate molar proportion, increased butyrate proportion, and tended to decrease acetate:propionate ratio in samples of kinetics, but did not modify nutrient digestibility. Protection of Se tended to decrease NH₃-N concentration, NH₃-N flow, and CP digestibility; and to increase flows of nonammonia N and dietary N. Our results indicate that protection of CuSO₄ may increase butyrate concentration at expenses of acetate, while protection of Na₂SeO₃ tended to reduce ruminal degradation of N. Further research is needed to determine the effects of lipid-microencapsulation on intestinal absorption, tissue distribution of Cu and Se, and animal performance.

Chlorella vulgaris microalgae and/or copper supplementation enhanced feed intake, nutrient digestibility, ruminal fermentation, blood metabolites and lactational performance of Boer goat

The associative effects of Chlorella vulgaris microalgae and copper (Cu) supplementation on feed utilisation and lactational performance in goats were evaluated. Thirty-two lactating Boer goats (34.8 ± 1.7 kg body weight) were used to evaluate the supplementation of C. vulgaris microalgae at 10 g/day (AL treatment), 9 mg of Cu/kg diet (CU treatment) or a mixture of both AL and CU treatments (ALCU treatment) on feed intake, nutrient digestibility, ruminal fermentation, blood metabolites and lactation performance of Boer goat milk yield and composition. Treatments did not affect feed intake; however, AL, ALCU and CU treatments increased (p < .001) nutrient digestibility. Treatment effect on ruminal pH, ammonia-N or propionate was marginal, but AL and ALCU treatments increased (p < .01) acetate, acetate/propionate ratio and total volatile fatty acids. Treatments increased (p < .001) serum glucose and Cu concentrations. Additionally, ALCU and AL treatments increased (p < .001) daily milk yield, energy corrected milk production, concentrations of ash, energy content, fat, lactose, solids not fat, total solids and milk (feed) efficiency. Conversely, the CU treatment decreased (p < .001) the concentration of all milk components, without affecting milk (feed) efficiency. Additionally, AL and ALCU treatments decreased (p < .05) the concentrations of saturated fatty acids by 2.4% and 4%, respectively, but increased (p < .05) the concentrations of total unsaturated fatty acids (UFAs) by 5.4% and 9.8%, respectively, mono-UFA by 5.2% and 9.8%, respectively, and conjugated linoleic acid concentrations by 9.3% and 7.4% respectively. In conclusion, supplementation of the diet of lactating Boer goats with C. vulgaris microalgae with or without copper enhanced nutrient digestibility, ruminal fermentation, milk production, milk efficiency and milk nutritive value. Copper supplementation had minimal effects; therefore, its use as a supplement in the presence of C. vulgaris microalgae to the diet of lactating Boer goats is recommended.

Beginning to offer drinking water at birth increases the species richness and the abundance of Faecalibacterium and Bifidobacterium in the gut of preweaned dairy calves

We previously demonstrated that dairy calves having access to drinking water since birth (W0) achieved greater body weight, fiber digestibility, and feed efficiency than those that first received drinking water at 17 d of age (W17). Since gut microbiota composition could be linked to growth and development of animals, the objective of this study was to examine the effect of offering drinking water to newborn calves on composition of bacteria in the gut using a fecal microbiota analysis. Fresh feces were collected directly from the rectum of calves in W0 (n = 14) and W17 (n = 15) at 2, 6, and 10 wk of age. All of the calves were fed pasteurized waste milk, weaned at 7 wk of age, and offered tap water according to the treatment. The DNA was sequenced using 16S rRNA gene-amplicon sequencing on an Illumina MiSeq system (Illumina Inc., San Diego, CA). The sequences were clustered into operational taxonomic units (OTU) with a 99% similarity threshold. Treatment effects on α-diversity indices and relative abundance of the 10 most abundant genera were analyzed using GLIMMIX procedure of SAS (SAS Institute Inc., Cary, NC). Statistical significance (q-value) of treatment effects on the 50 most abundant OTU was determined with a false discovery rate analysis. At 2 wk of age, W0 had a greater number of observed OTU (5,908 vs. 4,698) and species richness (Chao 1 index) than W17. The number of OTU and richness indices increased from wk 2 to 6, but the increment of W17 was greater than that of W0. The Shannon and inverse-Simpson indices increased linearly with age, but no difference was observed between W0 and W17 at any time point. The Firmicutes to Bacteroidetes ratios were also similar at every time point but decreased markedly when calves were weaned. The relative abundance of genera Faecalibacterium and Bacteroides was greater in W0 than W17 at 2 wk of age. The genus Faecalibacterium continued to be more abundant in W0 than W17 at 6 wk of age but had similar abundance 3 wk after weaning (10 wk of age). The abundance of Faecalibacterium at wk 6 was positively correlated with apparent total-tract digestibility of acid detergent fiber at 10 wk of age. Calves receiving water since birth had greater abundance of OTU related to Faecalibacterium prausnitzii, and Bifidobacterium breve at 6 wk of age (q < 0.085). These species are known to improve growth in preweaned calves. The abundance of none of the genera and OTU was different between W0 at W17 at 10 wk of age (q > 0.100). Overall, beginning to offer drinking water at birth has a potential to modulate gut microbiota composition and thereby positively affect performance of young dairy heifer calves (≤10 wk of age).

Evaluation of source of corn silage and trace minerals on lactational performance and total-tract nutrient digestibility in Holstein cows

We evaluated the effects of source of corn silage and trace minerals on lactational performance and total-tract digestibility (TTD) of nutrients in 16 Holstein cows averaging 82 (standard error = 3) days in milk in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments with 28-d periods. The diets consisted [dry matter (DM) basis] of 55% conventional (CON) or brown midrib-3 (BM3) corn silage, 2% chopped wheat straw, and 43% grain mix with either sulfate (STM) or hydroxy (HTM) sources of copper, manganese, and zinc trace minerals. The targeted supplemental concentrations of copper, zinc, and manganese were 194, 1,657, and 687 mg/d, respectively. The dietary treatments were CON-STM, CON-HTM, BM3-STM, and BM3-HTM. The dietary nutrient composition of the BM3 diets averaged 32.1% amylase neutral detergent fiber on an organic matter basis (aNDFom) and 6.9% undigested neutral detergent fiber at 240 h (uNDF240om; % of DM), and CON diets averaged 36.2% aNDFom and 8.6% uNDF240om (% of DM). The average supplemental concentrations of copper, zinc, and manganese for the STM diets were 10, 41, and 64 mg/kg, respectively, and the average supplemental concentrations of copper, zinc, and manganese for the HTM diets were 10, 40, and 62 mg/kg, respectively. The average total dietary concentrations of copper, zinc, and manganese for the STM diets were 17, 104, and 60 mg/kg, respectively, and the average total dietary concentrations of copper, zinc, and manganese for the HTM diets were 17, 91, and 66 mg/kg, respectively. Data were summarized by period and analyzed as a replicated Latin square design with fixed model effects for corn silage, trace minerals, corn silage × trace mineral interaction, period within replicated square, and replicated square using the MIXED procedure of SAS. Cow within replicated square was a random effect. Cows fed the BM3 diets had greater dry matter intake (DMI) and milk yield (28.1 and 47.0 kg/d) than cows fed the CON diets (27.5 and 44.7 kg/d). We found no significant interaction between corn silage and trace minerals for DMI and milk yield. Cows fed the HTM diets (28.1 kg/d) had a greater DMI than cows fed the STM diets (27.5 kg/d). Cows fed the BM3 diets had greater TTD of DM and OM (72.8 and 74.1% of DM) than cows fed the CON diets (71.1 and 72.3% of DM). Cows fed the HTM diets had a tendency for greater TTD of aNDFom than cows fed the STM diets (56.8 vs. 54.9% of DM). Cows fed the CON diets ruminated longer during the day than cows fed the BM3 diets (524 vs. 496 min/d). Corn silage with greater NDF digestibility and lower uNDF240om enhanced DMI, milk yield, and TTD of DM and OM, and hydroxy trace minerals improved DMI and tended to improve TTD of aNDFom. The source of corn silage and trace minerals should be taken into consideration when formulating diets for high-producing dairy cows.

Colostrum and milk performance, and blood immunity indices and minerals of Holstein cows receiving organic Mn, Zn and Cu sources

Effects of supplementing the basal diets with Mn, Zn and Cu, as sulphate, glycine or methionine salts, on colostrum and milk performance, some blood immunity indices and blood minerals of pre- and post-partum Holstein cows were accessed. Forty cows in different groups received: 1) a diet without supplementary Mn, Zn and Cu (control), 2) a diet containing Mn, Zn and Cu sulphates, 3) a diet containing Mn, Zn and Cu glycine, or 4) a diet containing Mn, Zn and Cu methionine with 10 cows per group from d 60 before calving (dry period) to d 100 of lactation. Dry matter intake (DMI), dry matter digestibility (DMD), colostrum and milk performance, milk somatic cell count (SCC), blood and milk total antioxidant capacity (TAC), immunoglobulin M (IgM) and immunoglobulin A (IgA), and blood Mn, Zn and Cu were determined. Dietary supplementation with Mn, Zn and Cu as methionine, glycine or sulphate salts had positive effects on DMD, DMI, colostrum and milk performance, milk SCC, and blood Mn and Zn. Addition of Mn, Zn and Cu in diets could increase (P < 0.05) blood and milk TAC and blood IgA and IgM in the cows and their new-born calves. There were no differences in DMI, DMD, colostrum and milk yields, milk SCC, blood Mn (except d 50 postpartum), Zn and Cu and TAC (except d 50 postpartum) among the organic and inorganic minerals-supplemented groups (P > 0.05), however, the blood concentrations of IgA (except d 1 postpartum) and IgM in the cows supplemented with organic Mn, Zn and Cu were higher (P < 0.05) than those in the cows receiving the sulphate sources of minerals. Overall, dietary supplementation of Mn, Zn and Cu as methionine, glycine or sulphate salts can improve colostrum and milk performance, blood Zn and Mn and immunity indices in Holstein cows and their new-born calves. Moreover, the organic sources of Mn, Zn and Cu have advantage over the sulphate forms in terms of the blood immunoglobulins.

Trace mineral source influences ruminal distribution of copper and zinc and their binding strength to ruminal digesta1,2,3

Eight crossbred steers (BW 719.0 ± 65.0 kg) with ruminal and duodenal cannulae were used to examine the effect of trace mineral (TM) source on digestibility; ruminal and duodenal solubility of Cu, Zn, and Mn; and in vitro release of Cu, Zn, and Mn from the solid fraction of ruminal digesta. Experiment 1 determined the effect of TM source on DM and NDF digestibility in steers fed a corn silage and steam-flaked corn-based diet. Treatments consisted of 10 mg Cu, 20 mg Mn, and 30 mg Zn/kg DM from either sulfate TM (STM) or hydroxy TM (HTM) sources. Following a 14-d adaptation period, total fecal output was collected for 5 d. Dry matter digestibility was not affected by treatment, but NDF digestibility tended (P < 0.09) to be greater in HTM vs. STM supplemented steers. In Exp. 2, steers were fed a diet without supplemental Cu, Zn, or Mn for 19 d. Steers were then administrated a pulse dose of STM or HTM (2× the National Research Council requirements for Cu, Mn, and Zn) via the rumen fistula. Ruminal and duodenal samples were obtained at 2-h intervals starting at -4 and ending at 24 h relative to dosing. Ruminal soluble Cu and Zn concentrations were affected by treatment, time, and treatment × time. Soluble concentrations and percent soluble Cu and Zn in ruminal digesta increased (P < 0.05) above 0-h values for 10 h following dosing with STM, but not HTM. Concentrations of Cu and Zn in ruminal solid digesta were also affected by treatment, time, and treatment × time. Steers dosed with STM had greater (P < 0.05) solid digesta Cu concentrations at 2 and 4 h but lesser (P < 0.05) concentrations from 6 to 20 h post-dosing than those receiving HTM. Ruminal solid digesta Zn concentrations were greater (P < 0.05) in HTM vs. STM-dosed steers from 6 through 24 h post-dosing. Distribution of Mn in ruminal digesta was affected by TM source, but to a lesser extent than Zn and Cu. Duodenal soluble TM concentrations were variable and not affected by treatment. Binding strength of TM to ruminal solid digesta was estimated at 0, 6, and 12 h post-dosing using dialysis against chelating agents. The percentage of Cu and Zn released from ruminal solid digesta by dialysis against Tris-EDTA was greater (P < 0.05) at 12 h post-dosing from steers receiving HTM vs. STM. Results indicate that Cu and Zn from HTM have low solubility in the rumen and appear to be less tightly bound to ruminal solid digesta than Cu and Zn from STM.

Influence of dietary zinc concentration and supplemental zinc source on nutrient digestibility, zinc absorption, and retention in sheep

The objective of this study was to assess whether supplemental Zn source or concentration would affect ruminant Zn retention and nutrient digestibility. Thirty-six weaned crossbred Polypay wethers, were sorted by BW to 3 periods and stagger started on a common diet (22 mg Zn/kg DM) for a 52-d depletion period. Day 52 BW was used to assign Zn treatments (3 lambs/treatment/period): no supplemental Zn (CON), or supplemental Zn (40 mg Zn/d) from Zn sulfate (ING; Zinc Nacional, Monterrey, SA, Mexico), Zn methionine (ORG; Zinpro 120; Zinpro, Eden Prairie, MN), or Zn hydroxychloride (HYD; IntelliBond Z; Micronutrients USA LLC, Indianapolis, IN). On day 53 (day 1 of Zn treatments), lambs were moved to metabolism crates for 10 d of adaptation and 5 d of total fecal and urine collection. Blood for plasma Zn analysis was collected on day 52 and day 68. Data were analyzed as a randomized complete design with fixed effects of treatment, period and the interaction, which was significant (P ≥ 0.19) for day 68 plasma Zn but was removed for all other variables. Contrast statements were used to separate treatment means: CON vs. ZINC (ING, ORG, HYD), ING vs. HYD, and ORG vs. HYD. Day 52 plasma Zn concentrations were similar when CON was compared with ZINC (P = 0.84), and when ING and ORG were compared with HYD (P ≥ 0.19). Dry matter and neutral detergent fiber digestibility were lesser in ORG compared with HYD (P = 0.05) and organic matter and acid detergent fiber digestibility tended (P ≤ 0.08) to be lesser in ORG compared with HYD. Intake and fecal excretion of Zn was lesser, while apparent absorption of Zn was greater, in CON compared with ZINC (P ≤ 0.001). Zinc retained as a percent of Zn intake was greater in CON compared with ZINC (P = 0.001). Zinc retained (mg/d) was similar in CON compared with ZINC (P = 0.58) and when ING or ORG were compared with HYD (P ≥ 0.83). There was a treatment × period interaction for day 68 plasma Zn where treatments did not differ for periods 1 and 3 but ORG lambs had increased plasma Zn in period 2 compared with other treatments (P = 0.02). Lambs receiving no supplemental Zn had increased apparent absorption, suggesting Zn absorption may be upregulated in these lambs. Similarities in Zn retention across treatments suggests Zn requirements of these lambs were met regardless of supplementation concentration or source. Nutrient digestibility was improved in HYD lambs compared with ORG, and further work is needed to clarify the influence of supplemental Zn source on nutrient digestion.

The influence of supplemental zinc and dietary fiber concentration on mineral retention of beef steers

The objective was to determine if zinc (Zn) retention improved with supplemental Zn above recommended concentrations with increasing dietary fiber concentration. Angus steers (n = 32; 309 ± 4.2 kg body weight [BW]) with GeneMax gain scores of 3, 4, or 5 were utilized in a 2 × 2 factorial arrangement (8 steers per treatment). Steers were stagger started (four blocks of eight steers) and stratified by BW within growing diets to one of two Zn strategies (ZNTRT), no supplemental Zn (analyzed 36 mg Zn/kg dry matter [DM]; CON) or supranutritional Zn (CON + 60 mg Zn/kg DM as ZnSO4 + 60 mg Zn/kg DM as Zn-amino acid complex; SUPZN). Dietary fiber strategies (FIBER) were formulated to target two fiber supplementation rates representing high fiber (HF; ~35% neutral detergent fiber [NDF]) or low fiber (LF; ~25% NDF). Within block, steers received HF for 60 d; then pens were randomly assigned to LF or HF for finishing. Steers fed LF were transitioned for 15 d; on day 75, steers were moved to metabolism crates and adapted for 10 d, followed by 5 d of total fecal and urine collection. Retention of Zn, Mn, Fe, Cu, and N were calculated. The model for analysis of metabolism data included the fixed effects of ZNTRT, FIBER, block, and the interaction of ZNTRT × FIBER, with the three-way interaction of ZNTRT × FIBER × block as random. Steer was the experimental unit (n = 8 per treatment combination). Zinc did not affect initial 60-d performance (P ≥ 0.62). DM and organic matter digestibility were lesser (P = 0.02) and N digestibility tended to be lesser (P = 0.07) in CON vs. SUPZN. Intake and digestibility of NDF and acid detergent fiber were greater (P ≤ 0.01) in HF vs. LF. Digestibility and retention of N as a percentage of intake were greater (P ≤ 0.04) whereas N retention as grams per day tended to be greater in HF vs. LF (P = 0.06). Apparent absorption of Zn tended to be greater (P = 0.06) in CON vs. SUPZN. A ZNTRT × FIBER effect was identified for Zn retention (milligrams per day; P = 0.01) where within SUPZN Zn retention was greater in HF vs. LF (P < 0.01). Apparent absorption and retention of Zn were greater (% of intake; P ≤ 0.02) in HF vs. LF. Apparent absorption of Cu, Fe, and Mn was unaffected by ZNTRT or FIBER (P ≥ 0.24). Increasing dietary Zn increased Zn retained regardless of changes in coefficient of absorption. In addition, dietary fiber content may impact trace mineral and N metabolism by steers, potentially due to increased release of these nutrients from feed as fiber digestibility increases. It appears dietary Zn concentrations and diet composition influence trace mineral absorption in beef steers.

Evaluation of creatinine as a urine marker and factors affecting urinary excretion of magnesium by dairy cows

Nutrient balance studies require measuring urine volume, and urinary excretion can be used to assess Mg bioavailability. A less laborious method than total collection of urine could make balance studies more feasible and expand the utility of using urinary Mg as an index of bioavailability, but the method needs to be accurate and sensitive. Sampling interval can affect accuracy because excretion must be at steady state. Two experiments were conducted to (1) determine whether urinary creatinine could be used to accurately estimate urinary output of nutrients markedly excreted via urine (N, K, Na, S, and Mg; experiment 1) and (2) determine the appropriate sampling schedule to evaluate Mg excretion after abrupt diet changes (experiment 2). Experiment 1 was originally designed to evaluate the interaction of monensin [0 vs. 14 mg of monensin/kg of dry matter (DM)] and Mg source (MgO vs. MgSO₄; total diet Mg: 0.36% of DM) under antagonism from increased dietary K (2.11% of DM) on urinary Mg excretion. Experiment 2 evaluated the interaction of Mg concentration (basal vs. supplemental MgO; total diet Mg: 0.20 vs. 0.42% of DM) and K (basal vs. supplemental K₂CO₃; total diet K: 1.60 vs. 2.57% of DM) on urinary Mg excretion over time. Using 4-d composite samples from total collection of urine (n = 34 cow-periods), the average daily excretion of creatinine was similar to previous estimates (29.0 ± 1.16 mg of creatinine/kg of body weight) but was variable among cows (root mean squared error = 2,980 mg/d; 14% of mean). Treatment-average estimated excretion of urine and urinary N, K, Na, S, and Mg were similar to actual values; however, differences between actual and estimated values could be substantial for individual cows. Using the mean creatinine excretion per kilogram of body weight for all cows to estimate urine eliminates the lack of fit variance resulting in artificially low within-treatment variation for estimated urine volume. The standard error of the mean for estimated urine volume was 23% less (1.93 vs. 2.51) than that for actual urine production. This inflated the type I error rate, and, consequently, statistical inferences on N and K excretion differed when urine output was estimated rather than measured. The standard error of the mean for excretion of Mg calculated with actual or estimated urine production were almost identical (0.92 vs. 0.97); however, similar standard error of the mean was likely caused by differences in the covariance of urinary Mg concentration with estimated or actual urine output. Based on spot sampling (experiment 2), urinary Mg reached steady state by 2 d following an increase in dietary K regardless of Mg level, whereas excretion of urinary Mg following an increase in dietary Mg continued to increase through 7 d. Estimating nutrient excretion with urinary creatinine and body weight on average is accurate, but variance is likely underestimated. Knowing the time course of urinary Mg excretion will improve the value of using urinary Mg concentration to assess diet adequacy or Mg bioavailability.