ISSUE FOCUS 32 FEED & ADDITIVE MAGAZINE March 2022 COPPER IN RUMINANTS: FROM ESSENTIAL TO TOXIC “Copper (Cu) bioavailability for ruminants is mainly determined by sulfur, molybdenum and iron levels in the diet. Thus, complete forage analyses are essential to fine tune the quantity of Cu needed to meet the animal requirements, without forgetting drinking water which can be a significant source of iron and sulfur for the animal.” COPPER: ESSENTIAL FOR RUMINANTS It has long been recognized that copper (Cu) is an essential trace element in ruminants. As it is required in many key enzymes, any sub-clinical deficiency will impair animal health, fertility and production performance. Cu requirements and maximum Cu level authorized in the European Union are presented in Figure 1. For bovine, the requirements are around 10 mg/kg DM with higher values for dairy cows in the close-up period and in the first weeks after parturition. Following the 8th revised edition of the Nutrient Requirement of Dairy Cattle (NASEM 2021) little change is observed in requirements in Cu for average lactating cows (11 mg/kg DM). However, for dry cows, requirements increased 40% (17 mg/ kg DM) while for high producing cows, requirements decreased 45% (9 mg/kg DM). Higher values are recommended for caprine (up to 25 mg/kg DM) but lower for ovine (up to 10 mg/ kg DM) which are highly sensitive to excess Cu. A genetic variation observed in Cu absorption can also influence Cu requirements. Literature mentions in particular higher requirements in Scottish Blackface than in Texel sheeps and in Jersey than in Holstein Friesians cows. LIMITATIONS OF REQUIREMENTS SYSTEM With the most recent research on dairy cattle mineral nutrition, guidelines are becoming more and more accurate in defining dietary requirements. Still, some limitations in the system do exist. Those requirements systems do not take into account rumen effect, ‘non absorbed’ effects or antagonistic effect. That’s why adjustments need to be done despite the high precision of the latest data. Because of the small margin between Cu deficiency and Cu toxicity and because the high susceptibility of Cu to bind antagonists in the rumen, Cu is a good example of an element to adjust closely in ruminants. Valérie Kromm Product Manager Animine
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