Safety And Efficacy Of A Feed Additive Consisting Of 3-nitrooxypropanol (bovaer® 10) For Ruminants For Milk Production And Reproduction (dsm Nutritional Products Ltd)

Abstract

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of Bovaer® 10 as a zootechnical additive for ruminants for milk production and reproduction. Systemic exposure or site of contact toxicity for the active substance 3-nitrooxypropanol (3-NOP), for which genotoxicity has not been fully clarified, in the target species, is unlikely based on ADME data available. Consequently, the FEEDAP Panel concluded that Bovaer® 10 was safe for dairy cows at the maximum recommended level. However, as a margin of safety could not be established, the FEEDAP Panel could not conclude on the safety of the additive for other animal species/categories. The FEEDAP Panel considered that the consumer was exposed to 3-nitrooxypropionic acid (NOPA), which is one of the 3-NOP metabolites. NOPA was not genotoxic based on the studies provided. The FEEDAP Panel concluded that the use of Bovaer® 10 in animal nutrition under the conditions of use proposed was of no concern for consumer safety and for the environment. The FEEDAP Panel concluded that the active substance 3-NOP may be harmful if inhaled. It is irritant (but not corrosive) to skin, irritant to the eyes but it is not a skin sensitiser. As the genotoxicity of 3-NOP is not completely elucidated, the exposure through inhalation of the additive may represent an additional risk for the user. The Panel concluded that the additive has a potential to be efficacious in dairy cows to reduce enteric methane production under the proposed conditions of use. This conclusion was extrapolated to all other ruminants for milk production and reproduction.

Generated Summary

This scientific opinion, adopted by the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP), assesses the safety and efficacy of 3-nitrooxypropanol (Bovaer® 10) as a zootechnical additive for ruminants, specifically for milk production and reproduction. The assessment followed a request from the European Commission. The FEEDAP Panel evaluated various aspects, including the characterization of the additive, its safety for target species (ruminants), consumers, users, and the environment, as well as its efficacy in reducing enteric methane production. The methodology involved reviewing data provided by the applicant, DSM Nutritional Products Ltd, and applying relevant guidance documents and principles. The assessment considered data on the additive’s composition, manufacturing process, stability, and homogeneity, along with the conditions of its proposed use. The primary goal was to determine if Bovaer® 10 met the criteria for safety and efficacy as a feed additive under the proposed conditions of use, as stipulated in Regulation (EC) No 1831/2003. The core of the assessment focused on the active substance, 3-nitrooxypropanol (3-NOP), with investigations into its absorption, distribution, metabolism, and excretion (ADME), residue studies, and toxicological profiles to gauge its potential impacts. Furthermore, the study considered the consumer exposure to NOPA (3-nitrooxypropionic acid), a metabolite of 3-NOP, and its potential effects. The opinion also included environmental safety aspects and efficacy data to understand the overall impact of the additive.

Key Findings & Statistics

• The additive Bovaer® 10 consists of 3-nitrooxypropanol (3-NOP) at 10.5%, propylene glycol at 35.2%, and silicic acid at 54.3%. The minimum content of 3-NOP is specified at 10%.
• The content of 3-NOP in nine batches of the additive had a mean of 10.98%, with a range of 10.32–11.3%.
• The dusting potential of the additive ranged from 330 to 390 mg/m³.
• The average particle diameter of the additive was 290 μm.
• The content of 3-NOP in three industrial batches of the active substance ranged between 99.1% and 99.4% (w/w%).
• The shelf-life study showed an average retention of 95.5% after 18 months at 25°C and 97.3% after 12 months at 30°C.
• In a mineral premixture, the recovery of the active substance (3-NOP) ranged from 98.3% to 98.8% after 6 months at 25°C.
• In a compound feed, the recovery was 74% after 3 months at 25°C, and 89% after pelleting, with 83.3% recovery after pelleting and 3 months of storage.
• The coefficient of variation (CV) for homogeneity ranged from 0.3% to 1.3%.
• The additive is proposed to be used at a minimum recommended level of 60 mg 3-NOP/kg dry matter (DM) and a maximum of 100 mg 3-NOP/kg DM.
• In the first in vivo study, radioactivity recovered in urine in the first 24 h was 17.6% of the dose, with 2.3% in faeces within 48 h.
• The major urinary metabolite was 3-hydroxy-propionic acid (3-HPA), representing 47.5% of the urine radioactivity.
• In a mass balance study, 77.4% of the dose was recovered from volatile traps, and 9.8% and 1.2% in urine and faeces, respectively.
• In the second in vivo study, the mean levels of radioactivity in plasma 48 h after dosing was 7.0 in males and 4.2 µg 3-NOP-eq/mL in females for the low dose, and 51.9 in males and 34.5 µg 3-NOP-eq/mL in females for the high dose.
• The FEEDAP Panel considered that the use of Bovaer® 10 as feed additive does not raise concern for the safety of the consumer regarding genotoxicity, and the health-based guidance value (ADI) of 1 mg 3-NOP/kg bw per day can be derived.
• The maximum HRP (highest reliable percentile) values for NOPA exposure were 0.4542 µg/kg bw per day for infants, 0.4674 µg/kg bw per day for toddlers, 0.5952 µg/kg bw per day for other children, 0.2260 µg/kg bw per day for adolescents, 0.1293 µg/kg bw per day for adults, 0.1162 µg/kg bw per day for elderly, and 0.1266 µg/kg bw per day for very elderly.
• The 2x group had a 4% less DM intake than the control group, and the energy corrected milk yield was increased by 7% in the 2x group compared with the control.
• In the three studies, the addition of 60 mg 3-NOP per kg DM to dairy cow TMR was associated with a significant decrease (by between 20 and 35% compared with the control) in enteric methane emission per day, per kg DM intake (yield) and per kg EC milk yield (intensity).
• The studies showed that methane was decreased by about 20% when 3-NOP was used at 100 mg 3-NOP/kg DMI.
• Feed efficiency was increased in cows fed the 3-NOP diet in study 1.

Other Important Findings

• 3-NOP is rapidly metabolized to 3-nitrooxypropionic acid (NOPA) in the presence of NAD+ in vitro.
• In vivo studies in rats showed that 3-NOP is stable in the stomach and is partially metabolised in the intestine.
• 3-NOP is predominantly exhaled as CO2 (about 70%) in rats.
• The metabolite NOPA induced gene mutations in a bacterial reverse mutation assay, while no chromosomal damage was reported in an in vitro MN assay.
• A 2-year carcinogenicity study in rats reported an increase in rare mesenchymal intestinal tumours after 3-NOP treatment.
• 3-NOP is mainly converted by ruminal fermentation into 1,3-propanediol in ruminants.
• NOPA was not found in milk and edible tissues above the LOQ in an ADME study performed in four lactating cows.
• The FEEDAP Panel concludes that potential systemic toxicity of the additive is unlikely in the target species.
• The additive is considered to be efficacious to reduce enteric methane production when given orally at the concentration of 60 mg 3-NOP/kg DM feed (corresponding to 53 mg/kg complete feed, DM 88%) to dairy cows.
• The results of the three efficacy studies showed that 3-NOP can reduce enteric methane production in dairy cows when added to mixed rations at 60 mg/kg DM feed.
• In the tolerance study, although the DM intake in the cows of the 2x group was 4% less than that in the control group, this had no effects on bw change or milk yield.
• The addition of 60 mg 3-NOP per kg DM to dairy cow TMR was associated with a significant decrease in enteric methane emission per day, per kg DM intake (yield) and per kg EC milk yield (intensity).
• Methane production was estimated from spot measurements taken using the GreenFeed® system.
• The results of the three efficacy studies showed that 3-NOP can reduce enteric methane production in dairy cows when added to mixed rations at 60 mg/kg DM feed (corresponding to 53 mg/kg complete feed) without effects on performance.
• The addition of 60 mg 3-NOP per kg DM to dairy cow TMR was associated with a significant decrease in enteric methane emission per day, per kg DM intake (yield) and per kg EC milk yield (intensity). Concurrently, there was an increase in the emission of hydrogen.
• In the tolerance study, although the DM intake in the cows of the 2x group was 4% less than that in the control group, this had no effects on bw change or milk yield.

Limitations Noted in the Document

• The data from the dose-range finding study was not used for assessing consumer exposure to NOPA due to unexpectedly high differences of NOPA concentration between morning and afternoon milking.
• The dose-range finding study showed some weaknesses: only few animals were used, lack of confirmation of the target concentration of additive in the feed linked to a possible tendency of the additive to decrease over the time, and limited ability of the additive to homogeneously distributed in feed.
• The FEEDAP Panel noted that there was no evidence of bone marrow exposure in the micronucleus test.
• The treatment protocol applied for the extended treatment in the extended treatment was not fully compliant with OECD TG 487.
• Given the statistical differences found in some of the endpoints, some uncertainty remains on the tolerance of 3-NOP by dairy cows at the overdose (2x) level.
• The value of the data gathered from literature review is limited.

Conclusion

The EFSA FEEDAP Panel’s comprehensive scientific opinion on Bovaer® 10 (3-nitrooxypropanol) provides valuable insights into its safety and efficacy as a feed additive for dairy cows, focusing on methane reduction and its impact on animal health and consumer safety. The key finding is that Bovaer® 10 is deemed safe for dairy cows at the maximum recommended level of 100 mg 3-NOP/kg DM in feed (corresponding to 88 mg/kg complete feed, DM 88%), with no established margin of safety. This determination hinges on extensive data analysis, including characterization studies, ADME studies in both experimental species and humans, residue studies, and toxicological assessments. Notably, the review highlights the rapid metabolism of 3-NOP, mainly to 3-nitrooxypropionic acid (NOPA), in the rumen, which diminishes the risk of systemic toxicity within the target species. The panel concludes that the use of Bovaer® 10 is not of concern for consumer safety, given the limited presence of NOPA in milk and tissues and its lack of genotoxic activity. The efficacy of Bovaer® 10 in reducing enteric methane emissions in dairy cows is supported by the three long-term studies, where the additive at 60 mg 3-NOP/kg DM significantly reduced methane production. However, due to the limitations and lack of a margin of safety, the FEEDAP Panel was not able to conclude on a safe dietary concentration of Bovaer® 10 for other ruminant species/categories. In terms of safety, the panel acknowledged that 3-NOP is rapidly metabolized, primarily in the rumen, preventing its accumulation in animal tissues. The consumer safety assessment showed that the use of Bovaer® 10 did not raise any concerns regarding genotoxicity or exposure to NOPA in milk and edible tissues. The user’s safety assessment indicated that the additive may be harmful if inhaled, and that the use of the additive under the conditions of use proposed is of no concern for the environment. The study emphasizes the importance of understanding the metabolic pathways and the potential risks associated with feed additives within the context of animal nutrition, emphasizing the need for continuous monitoring. Overall, the FEEDAP opinion suggests that Bovaer® 10 could be an effective tool for reducing methane emissions in dairy cows. The panel highlights the importance of further research and scrutiny of the additive to establish safe levels for other species.

DOI

10.2903/j.efsa.2021.6905