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RCT·veterinary medicine, toxicology, animal nutrition, agricultural medicine·PMC10177583

Influences of Glyphosate Contaminations and Concentrate Feed on Performance, Blood Parameters, Blood Cell Functionality and DNA Damage Properties in Fattening Bulls

Animals : an Open Access Journal from MDPI · 9 authors, 1 centre

AI SUMMARY

FIDELITY 97%

POPULATION48 German Holstein fattening bulls (initial body weight 392 ± 60.4 kg, age 332 ± 29 days)

INTERVENTIONGlyphosate-contaminated rations (average exposure 128.6–213.7 µg/kg BW/d) combined with either high or low concentrate feed proportions

COMPARISONControl rations (glyphosate exposure 1.3–2.0 µg/kg BW/d) with high or low concentrate feed proportions

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TL;DR

This feeding study on German Holstein bulls found that glyphosate residues in feed at levels reflecting formerly legal agricultural practice in Germany (average 171 µg/kg body weight/day) did not adversely affect animal performance, organ weights, blood parameters, immune cell function, or DNA integrity over a 15-week fattening period. In contrast, the proportion of concentrate feed significantly influenced most measured parameters. All animals remained clinically healthy, and the few statistically significant glyphosate-related effects were weak, inconsistent, and deemed not physiologically relevant.

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**Background:** Glyphosate (GLY) is the active ingredient in widely used non-selective herbicides and is frequently detected in livestock feed, raising concerns about potential toxic effects on animal health. While some studies have examined GLY effects in dairy cows, data on fattening bulls are scarce. This study aimed to investigate whether GLY residues in feed at levels reflecting formerly legal agricultural practice in Germany, combined with different concentrate feed proportions (CFP), affect the health and performance of growing Holstein bulls.

**Methods:** Forty-eight German Holstein bulls (initial BW 392 ± 60.4 kg) were assigned to four groups in a 2 × 2 factorial design: control rations with high CFP (CON_HC), control rations with low CFP (CON_LC), GLY-contaminated rations with high CFP (GLY_HC), and GLY-contaminated rations with low CFP (GLY_LC). Roughage consisted of 79% maize silage and 21% wheat straw. GLY-contaminated feed was produced by treating wheat and peas with Roundup Rekord® pre-harvest. Average daily GLY exposures were 128.6 µg/kg BW/d (GLY_HC), 213.7 µg/kg BW/d (GLY_LC), 1.3 µg/kg BW/d (CON_HC), and 2.0 µg/kg BW/d (CON_LC). Blood samples were collected at weeks 0, 7, and 15 and analyzed for hematological parameters, serum metabolites, antioxidant enzyme activities (SOD, GPx), ferric reducing ability of plasma (FRAP), DNA damage (comet assay), immune cell function (phagocytosis, ROS production, apoptosis, T-cell phenotyping by flow cytometry), and gene expression of DNA repair and apoptosis-related genes.

**Key Results:** GLY exposure did not significantly affect dry matter intake, average daily gain, or feed conversion. DMI and average daily gain were significantly higher in HC vs. LC groups (p_CFP < 0.001), while feed conversion was higher in LC groups (p_CFP < 0.001). Organ weights adjusted to 100 kg BW were mostly unaffected by GLY, except for gall bladder weight which was higher in GLY groups (p_GLY = 0.046). Serum metabolites including glucose, NEFA, BHB, and cholesterol showed significant CFP × time interactions, with GLY effects observed for AST (p_GLY×t = 0.046), BHB (p_GLY×t = 0.007), cholesterol (p_GLY×CFP×t = 0.023), triglycerides (p_GLY×t = 0.039), and total protein (p_GLY×t = 0.018), though all values remained within physiological ranges. Hematological parameters were predominantly influenced by CFP and time; hemoglobin showed a significant GLY × time interaction (p < 0.01). Antioxidant enzyme activities (SOD, GPx) were not affected by GLY. FRAP showed a significant three-way interaction (p_GLY×CFP×t < 0.01). Comet assay revealed higher tail DNA percentage and Olive tail moment in CON_HC compared to GLY_HC (p_GLY×CFP = 0.003 for both), indicating less DNA damage in GLY_HC. Gene expression analysis showed increased mRNA abundances of DNA repair-related genes (HSPA1A, XRCC5, PARP1, TP53) in GLY groups (p < 0.05). Proportions of CD4+ and CD8+ T-cells showed significant GLY × time interactions (p = 0.043 and p = 0.003, respectively), but patterns were inconsistent. Phagocytosis, ROS production, and apoptosis were not adversely affected by GLY. All animals remained clinically inconspicuous throughout the trial.

**Clinical Implications:** This study provides evidence that glyphosate residues in feed at levels reflecting formerly legal agricultural practice in Germany do not compromise the health or performance of fattening bulls over a 15-week period. The few statistically significant GLY effects were weak, inconsistent, and of questionable physiological relevance, particularly when compared to the marked and consistent effects of concentrate feed proportion. These findings align with previous studies in dairy cows and suggest that regulatory restrictions on GLY use implemented in Germany may have been conservative with respect to cattle health. However, the authors note that lifetime exposure studies would be needed to fully exclude any long-term effects. The study is limited by its relatively short duration (15 weeks), moderate sample size (12 animals per group), and the fact that it represents exposure conditions prior to stricter GLY restrictions.

PICO

PPOPULATION

48 German Holstein fattening bulls (initial body weight 392 ± 60.4 kg, age 332 ± 29 days)

IINTERVENTION

Glyphosate-contaminated rations (average exposure 128.6–213.7 µg/kg BW/d) combined with either high or low concentrate feed proportions

OOUTCOME

Performance (dry matter intake, average daily gain, feed conversion), blood parameters (hematology, serum metabolites, antioxidant enzymes), immune cell function (phagocytosis, ROS production, apoptosis, T-cell phenotyping), DNA damage (comet assay), and gene expression (DNA repair and apoptosis-related genes)

STUDY TYPE

RCT

SPECIALTY

veterinary medicine

SUMMARISED BY

AI pipeline

FIDELITY CHECK

97% · A

ORIGINAL PAPER

PMC10177583

Influences of Glyphosate Contaminations and Concentrate Feed on Performance, Blood Parameters, Blood Cell Functionality and DNA Damage Properties in Fattening Bulls

Animals : an Open Access Journal from MDPI

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ABSTRACT

Simple Summary Residues of herbicidal active substances such as glyphosate in ruminant feed lead to oral exposure in animals. Consequently, the possible toxic influences of glyphosate on the health of ruminants are of concern. While some studies have analyzed the effects of glyphosate residues on dairy cows, studies with fattening bulls are scarce. Therefore, the present feeding study on German Holstein bulls was conducted within a real-life in vivo scenario that could occur in Germany before restrictions on glyphosate usage are enacted and might still be realistic in other countries. As well as feeding diets with or without glyphosate residues for several weeks, different concentrate proportions were employed to analyze the putative influences of varying energy and nutrient supplies and consequently different ruminal milieus on potential glyphosate effects. Glyphosate exposure did not adversely affect animals’ performances or other health-related characteristics upon the tested conditions. The observed putative effects of glyphosate on selected blood parameters were rather weak and not consistent. In contrast, concentrate feed and time markedly influenced most of the experimental parameters. In summary, upon the formerly realistic exposure conditions in Germany, all animals remained clinically inconspicuous throughout the trial. Abstract Glyphosate (GLY), the active substance in non-selective herbicides, is often found in ruminant feed. The present feeding study aimed to investigate the effects of GLY-contaminated rations and different concentrate feed proportions (CFP) on the health of fattening German Holstein bulls. Bulls were grouped by low (LC) or high (HC) CFP with (GLY LC , GLY HC ) or without GLY-contaminations (CON LC , CON HC ) in their rations. Intakes (dry matter, water) and body weight were documented continuously lasting over an average range from 392.2 ± 60.4 kg to 541.2 ± 67.4 kg (mean ± SD). Blood samples collected at the trial’s beginning, and after 7 and 15 weeks, were analyzed for hematological and clinical-chemical traits, functional properties of leukocytes, redox parameters and DNA damage. The average GLY exposures of 128.6 (GLY HC ), 213.7 (GLY LC ), 1.3 (CON HC ) and 2.0 µg/kg body weight/d (CON LC ) did not lead to GLY effects for most of the assessed parameters relating to animal health and performance. CFP and time displayed marked influences on most of the experimental parameters such as higher dry matter intake and average daily gain in HC compared with the LC groups. GLY effects were rather weak. However, the observed interactive effects between GLY and CFP and/or time occurring in an inconsistent manner are likely not reproducible. Finally, all animals remained clinically inconspicuous, which brings into question the physiological relevance of putative GLY effects.

CITATION EXPORT

Ann-Katrin Heymann, Karina Schnabel, Fabian Billenkamp et al.. Influences of Glyphosate Contaminations and Concentrate Feed on Performance, Blood Parameters, Blood Cell Functionality and DNA Damage Properties in Fattening Bulls. Animals : an Open Access Journal from MDPI. (2023). https://doi.org/10.3390/ani13091499

AUTHORS

9 · 1 CENTRES

Ann-Katrin Heymann, Karina Schnabel, Fabian Billenkamp, Susanne Bühler, Jana Frahm, Susanne Kersten, Ulrich Meyer, Dirk von Soosten, Sven Dänicke

Institute of Animal Nutrition, Friedrich-Loeffler-Institut (FLI), Federal Research Institute for Animal Health, 38116 Braunschweig, Germany; [email protected] (A.-K.H.); [email protected] (K.S.); [email protected] (S.B.); [email protected] (J.F.); [email protected] (S.K.); [email protected] (U.M.); [email protected] (D.v.S.); [email protected] (S.D.)

EDITOR / REVIEWER

Cristina Castillo Rodríguez