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Table 2. The effect of supplemental zinc on 21 day post-wean pig performance with or without superdosing phytase (extracted from Walk et al., 2013, 2014b, 2014c, 2015; internal study, 2014.)


Average daily gain,


Supplementary zinc (mg/kg)1 0


1750-2500 2500-3500


Supplementary zinc (mg/kg)1 0


1750-2500 2500-3500


Relative improvement compared to pigs fed diets without zinc and phytase supplementation 0 FTU/kg phytase 100%


112.4% 116.6%


Feed conversion ratio,


Relative improvement compared to pigs fed diet without zinc and phytase supplementation 0 FTU/kg phytase 100% 94.9% 92.4%


2,500 FTU/kg phytase2 96.3% 88.7% 90.2%


Phytase used was Quantum Blue 5G (AB Vista, UK) and included from weaning to day 21 post-weaning with no nutrient matrix associated with the phytase.


1Supplementary zinc levels relate to the addition of ZnO above the base level already included in all diets (100-150 mg/kg). 2


This has been achieved by a 9% reduction in POMs for 3.1 kg/t ZnO, a 6% increase in POMs with 2 kg/t or 1.55 kg/t and a 3% increase in sales with 0 kg/t ZnO. This background work supports a potential alternative proposal


that may allow for medicinal use of ZnO to be maintained while also meeting the needs of EU Member States to reduce zinc intake to meet any environmental considerations. This alternative proposal is 1500 mg/kg zinc from wean to 14 days, 120 mg/kg until 30 kg (30 mg/kg reduction from current practice), and 100 mg/kg from 30 kg to slaughter (20 mg/kg reduction from current practice) which gives an estimated 23% zinc intake reduction from the current program today. This would achieve the same target as set out by the CVMP in their December 9th


proposal while still allowing for effective medicinal ZnO to be used from wean to day 14.


Is it proven? How can this reduction in zinc be achieved through superdosing phytase without negatively affecting performance? Research over the last four years has looked at this potential issue of reduced zinc levels and one key finding of that research is the impact that phytase can have on zinc utilization at pharmacological and at feed levels. It has been established through the published literature that


phytate has the potential to bind zinc at a pH 4 to 6 reducing the effectiveness of ZnO in the diet. A novel approach to zinc reduction is now open to EU Member States through the destruction of phytate with high levels or superdosing levels of phytase without negatively affecting performance. This application has been well studied and shows that typically in the presence of superdosing phytase the level of zinc from ZnO can be reduced from 2500 mg/kg to 1750 mg/kg without having a negative effect on performance as measured by gain and FCR (Table 2). Furthermore the data has shown that superdosing phytase lowers the level of post-wean diarrhoea which is attributed to


the increased effectiveness of ZnO due to the lower levels of dietary phytate attained with the use of superdosing phytase.


Reductions in dietary zinc levels? The effect of dietary phytate on zinc utilisation in the animal may also play a role in setting dietary zinc levels. With phytase (e.g. 500 FTU/kg) being included in 90% of all feeds manufactured, the extra release of zinc associated with the use of phytase could be taken into account when deciding zinc levels in these diets. For example research showed that the use of a microbial phytase at a standard 500 FTU/kg in pigs can release native zinc from plant feedstuffs of between 11 and 34 mg/kg depending on dietary phytate concentration. Hence the reduction in dietary zinc both in late nursery and finisher in the presence of phytase may be achievable without a negative effect on performance and warrants further investigation as part of an overall wean to finisher proposal to reduce zinc intake per pig while maintaining medicinal levels post-weaning at 1500 mg/kg.


Big opportunity This research has opened up the opportunity of maintaining or improving post-weaning pig performance while lowering pharmacological levels of dietary ZnO to 1500 mg/kg. Indeed this concept has already been exploited by a number of veterinary surgeons working with swine companies that are looking at the prudent and responsible use of ZnO in starter diets as outlined earlier. Increasingly feed companies and veterinarians are working together to balance the key role that medicinal levels of ZnO has in terms of growth performance and health with the ability to lower Zn levels with phytase superdosing to mitigate environmental concerns. Is this a potential solution whereby pig health and welfare can be


maintained, environmental concerns are met, and all parties involved meet their target goals? We think so.


2,500 FTU/kg phytase2 110.1% 130.0% 120.7%


PAGE 44 MARCH/APRIL 2017 FEED COMPOUNDER


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