INTRODUCTION: CHANGES IN MODERN TRACE MINERAL SUPPLEMENTATION
Of the 93 naturally occurring elements, most mammalian species must procure approximately 50 from dietary sources in order to maintain a normal healthy state. In addition to the six core elements (carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorus) of which carbohydrates, fats, proteins and nucleic acids are comprised, many other elements are essential to the nutritional requirements of higher animals. Some of these elements are required in relatively large quantities, in excess of 100 mg/day. These are termed ‘macro’. Others are required in much smaller quantities, on the order of a few mg per day. These are termed ‘micro’ or ‘trace’ elements.
Over the past 50 years, continuous efforts have been made to meet the nutritional requirements of animals through the scientific formulation of rations. Traditionally, trace mineral supplementation was achieved by the addition of simple inorganic salts such as copper (II) sulfate and zinc oxide. Research showed however that the bioavailability and hence the performance enhancement achieved by trace metal supplementation was significantly improved if the metal was added in the form of a metal complex or chelate (Ashmead, 1993). The important transition elements in biological processes are the redox catalysts iron (Fe), copper (Cu), cobalt (Co) and molybdenum (Mo). Manganese (Mn) and chromium (Cr) are also important; and zinc (Zn), although strictly not a transition metal, is also usually included and is an important element in a large number of enzymes and biosynthetic reactions. Additionally, mineral requirements have changed.
Most of the research relating to mineral requirements was carried out 30 to 50 years ago and may not apply to modern animals. Not only is the metabolic demand of more prolific pigs higher, but feed utilisation is more efficient than in the past. In the last 15 years feed conversion in fattening pigs has decreased from 3.5 to 2.7. Because of this, mineral intake per kg weight gain has been lowered by about 23%.
Along with finding the optimum form and dietary level of trace minerals for performance and health, recent interest in mineral nutrition has focused on environmental concerns owing to the amounts of manure spread on pasture and cropland associated with intensive rearing. The effects of spreading manure from a pig unit on farmland on accumulation of copper and zinc in cattle were evaluated in Galicia (Lopez et al., 2000). Hepatic copper and zinc concentrations in calves were elevated in areas with high levels of these elements in the soil. The densities of young pigs (piglets and growing-finishing pigs), but not reproductive sows, also influenced copper accumulation in calves. Liver copper levels in calves were significantly and positively related to the density of young pigs in the region. In areas with the highest pig densities, more than 20% of the cattle analysed had hepatic copper concentrations that exceeded the potentially toxic concentration of 150 mg/kg fresh weight. There was no evidence that zinc accumulation in calves was affected by pig density.
The heavy metal contents of farm manures are largely a reflection of their concentrations in the feeds consumed and the efficiency of retention of these nutrients by the animals. Fleming and Mordenti (1991) reported a mean zinc concentration in Belgian pig manures of 919 mg/kg DM. However Menzi and Kessler (1998) generally found 554 to 747 mg Zn/kg DM in Swiss pig manure. Copper concentrations in pig manures were much higher in Belgian manures (574 mg) than in Swiss manures (71 to 119 mg Cu/kg DM). These ranges, like those found in the literature, are extremely broad and clearly dependent to a large extent on the age of the pigs and the quantities of zinc and copper supplements added to the diet.
In order to protect environmental quality and safety, the European Commission is preparing a new directive designed to reduce the mineral loading on farmland. The result will be that maximum mineral levels allowed will be lower than presently used. Although there has not yet been a final decision on allowed levels, they will probably be close to the normal content of feedstuffs with supplementation minimal. These changes will make the introduction of organic trace minerals necessary.
RESEARCH AT CAPO WITH ORGANIC MINERALS: OVERVIEW
In recent years, a number of studies at the CAPO Institute have involved organic trace mineral supplementation of sow, piglet and grow/finish pig diets. The addition of an organic zinc source to sows reduced weight loss during the lactation period by 12% and shortened the weaning-oestrus interval by 7%. The daily weight gain of the suckling piglets was improved by 8%. In a study of different copper sources, organic copper resulted in the best performance of piglets. Daily weight gain was on average respectively 10 or 14% higher than in the copper sulphate group or the group with no copper addition, and the feed conversion was more efficient.
The addition of Bioplex™ minerals has been evaluated extensively in diets for growing/fattening pigs, both in terms of comparison with inorganic salts and dose response effects. In addition to performance, the effects on carcass quality, blood parameters, liver and muscle mineral content were measured. In almost all cases the performance with Bioplex™ minerals was higher than when inorganic minerals were included. Carcass quality was not significantly affected. The effects on blood, liver and muscle mineral content were variable, but the mineral level in the target tissues of pigs with the normal dietary mineral content reduced by 30% on addition of Bioplex™ minerals was not lowered.
Therefore, the total dietary mineral level can be reduced without any negative effect on the mineral status of the pigs. If the mineral content of target tissues is unaffected by this mineral reduction, we can calculate that mineral excretion will be lowered by more than 70%.
ORGANIC ZINC APPLICATION IN PIG DIETS
Zinc is an essential trace mineral for all animals. Involved in over 200 biochemical reactions in the body, zinc is required for the immune system, for reproduction and for regeneration of keratin. Some functions of zinc are:
• Enzyme systems: Zinc is an essential component of many different enzymes, including dehydrogenases, aldolases, peptidases, phosphatase and proteinases.
• Immunity: The immune system is composed of specific (cellular and humoral system) and nonspecific immune functions (phagocytes and macrophages). Of special importance is the
need for zinc to promote effective function of phagocytic cells.
• Prevention of mastitis: The production and the regeneration of keratin has a direct effect on the integrity of the udder lining and protection of the mammary gland from infection. Keratin is a fibrous protein lining the teat canal that serves as a barrier to invading organisms. Up to 50% of the keratin can be lost during each milking; and the need for its immediate regeneration is obvious. This approximate halving of keratin weights was identified by Bitman et al. (1991) when keratin weight before milking was 3 mg and post milking was 1.5 mg.
ORGANIC ZINC IN PIG STARTER DIETS
Zinc as zinc oxide has been reported by various universities to have a growth promoting effect for the weaned pig (Hill et al., 1996). In order to produce this response, the inclusion level must be quite high (>1000 ppm). Because availability of organic trace minerals is known to be higher, trials have been conducted with the objectives of both confirming the growth-promoting response and evaluating whether a similar response could be achieved using lower dietary levels of zinc from organic sources. A number of studies have shown a clear response to supplementing starter pig diets with zinc oxide on daily weight gain, however equal or better responses have been noted in trials using organic zinc at a lower total diet zinc concentration from either zinc methionine (Ward et al., 1997) or zinc proteinate (Mullan et al., 2002; Table 1).
ORGANIC ZINC FOR LACTATING SOWS
Organic zinc is commonly used in diets fed dairy cattle in many countries in order to reduce somatic cell counts and the incidence of clinical cases of mastitis. Since zinc is extensively involved in tissue integrity and keratin formation (20% of all zinc in the body is in the skin), the synthesis of keratin may be controlled by the amount of bioavailable zinc in the diet. Little is known about a comparative somatic cell count response in sows, however much management attention is focused on the incidence of MMA (mastitis metritis agalactia), also termed PHS (Periparturient Hypogalactia Syndrome). This problem is a complex, multifactorial disease that mostly appears during the first three days postpartum. The symptoms are not always evident, and sometimes there are no signs at all, however milk production is always reduced. Periparturient hypogalactia syndrome is caused by colibacillus and/or Streptococcus. These two bacteria are common in the environment of the lactating sow. In comparison with the udder of the dairy cow, the udder of the sow is even more closely in contact with soiled bedding and manure. As the syndrome names indicate, there is great similarity between mastitis and MMA or PHS.
In a trial with lactating sows we investigated effects of added organic zinc on the occurrence of MMA (PHA) and on performance of sows and suckling piglets. This experiment was conducted at a commercial farm in Belgium with 102 sows. All sows received a commercial lactation diet. Sows were divided into two groups based on parity with one group given an added 200 mg zinc from zinc methionine. The suckling piglets received a prestarter diet from day 8 to weaning (day 30). The addition of extra zinc methionine to the lactating sow diet had a positive influence on piglet health status. Faecal consistency (indication of diarrhoea occurrence) was significantly improved during the first 12 days after birth with higher faecal scores noted in piglets from treated sows (Table 2). While diarrhoea was noted in 23% of the control litters, incidence was reduced to 3% of litters from sows given the added organic zinc.
Blood samples were taken from a very small percentage of suckling piglets. Though variability was high, blood zinc levels in piglets from sows given zinc methionine was nearly twice the level of the controls. From these data we can conclude that a zinc methionine supplement for the lactating sow resulted in higher zinc status in the nursing piglet. Litter size of the sows given zinc methionine was 6% lower than those in the control group. This is not a result of treatment, because the treatment began 10 to 14 days before farrowing. There was no difference in birth weight, and the number of stillbirths in litters from sows given zinc methionine was reduced by 40%. This response, as well as the 8% improvement in piglet daily gain, is partially explained by the lower litter size.
After weaning, a small group of piglets (130) were followed through the nursery stage (7 kg to 26 kg). During this period the piglets from the zinc methionine-supplemented sows grew 3% faster than piglets from the control sows. These results indicate that piglets with a higher weaning weight and the same weaning age have improved performance. Sow metabolism was also influenced by zinc methionine supplementation. Sows given the supplement lost less weight during lactation (2 kg less), which was associated with a shorter weaningoestrus period (0.5 days).
ORGANIC ZINC FOR FATTENING PIGS
The first aim of this study was to assess the influence of full replacement of inorganic zinc by Bioplex Zn in the growing phase and finishing phases. A second goal was to investigate whether dietary mineral levels could be reduced to 30% of ‘normal levels’ when using Bioplexes while maintaining normal performance. The trial was conducted under practical conditions using 120 pigs. Six test diets were formulated (Table 3). Two diets included ‘normal’ levels of all trace minerals with one containing Zn in BioplexTM form and the other in inorganic form. These ‘normal’ levels of trace minerals were based on requirements and consisted of 120 ppm Zn, 130 ppm Fe, 60 ppm Mn and 20 ppm Cu. These levels are very close to practical diets in Belgium, apart from copper, which is typically added at 175 ppm in the grower diets (20-50 kg) and 35 ppm in the finishing diets (50-110 kg). Two additional diets contained twice the normal level of Zn (240 ppm) in either inorganic or BioplexTM form.
A third pair of diets were formulated to contain only 30% of the normal trace mineral levels described above. One diet contained all trace minerals in BioplexTM form and the other contained only Zn in BioplexTM form. The non-pelleted feeds were administered to the growing pigs ad libitum. The pigs (Hypor sow x Piétrain boar) were purchased from a breeder farm in West Vlaanderen. Pigs (average weight 23.7 ± 4.0 kg) were de-wormed using injectable levamisole hydrochloride and azoperone and numbered individually with ear tags. Piglets were assigned to pens and treatments based on body weight for the 16 week experiment. Piglets were vaccinated against Aujeski’s disease during week 2 with a booster injection given 3 weeks after the first vaccination. Animals were individually weighed at the start of the trial, at the end of the grower period (phase 1) and at the end of the fattening period (approximately 3 days before slaughter). The slaughter weight was calculated by extrapolation from the growth rate during the final period. Daily weight gains were calculated for each period. The daily feed intake was calculated as an average for the pen. If an animal was removed from a pen, feed intake values were corrected by means of the animal-days technique. Feed conversion efficiency was calculated using pen averages for intake and weight gain. Pigs were slaughtered when body weights between 100 and 110 kg were reached. Prior to slaughter, blood samples were drawn from 30 pigs for determination of blood mineral status.
The animals were slaughtered at the ‘Comeco’ facility of Covavee in Meer and were classified according to the SKG II system. Muscle samples were obtained from the same 30 pigs from which blood samples had been obtained. Carcasses were individually identified; and results were calculated and provided by Covavee. Pigs given the diet containing BioplexTM Zn at 120 ppm (normal) or the diet with all organic minerals at 30% of normal values gained 5.9% faster over the entire growing period than pigs given normal levels of Zn in inorganic form (Table 4). Daily feed intake and efficiency were not statistically different, but pigs given Bioplex™ Zn at normal Zn levels tended to consume more feed. Carcass quality parameters were unaffected by treatment (Table 5). Blood and muscle zinc content were unaffected by diet zinc level or form. This was also found by Mullan et al. (2002).
Based on whole carcass mineral content data of Mahan and Shields (1998), during the growing-finishing period a pig retains approximately 1400 mg of zinc. From the feed analysis in the current experiment, total zinc consumption of the pigs from the low organic, normal, double and 30% inorganic levels was respectively 8.9, 28.2, 58.8 and 8.7 gram. The total zinc intake from the inorganic normal zinc level was 28.2 g. This suggests that zinc excretion is linearly related to total zinc intake. Regarding the inorganic zinc group and taking into account the total feed intake (feed conversion x 85 kg body weight gain), the zinc excretion was reduced to 27-30% when using Bioplex™ Zn at 30% of normal dietary Zn content.
Copper is a unique trace mineral in that it acts as a growth promoter in growing-finishing pigs when included at high dietary concentrations. The improvement in growth rate from feeding 250 ppm of copper (as CuSO4) to weanling pigs also is well documented. The response seems to be additive to that obtained from feeding antibiotics. The most common source of copper used in feeds for growth promotion in pigs is the sulfate salt. The oxide and sulfide salts of copper are ineffective as growth promoters. Studies in which chelated copper has been added to pig diets or in which copper and a chelating agent have been added separately have shown that they are no more effective than CuSO4 in improving pig performance. Intravenously injected copper was shown to stimulate the growth of weanling pigs, which suggests a systemic mode of action that could at least complement the antimicrobial hypothesis proposed in the past. Injected copper has also been shown to stimulate the secretion of neuropeptide Y, which is a known feed intake stimulant for pigs. The feed intake capacity of pigs and piglets plays a very important role in the growth process. In most piglets and in those with high lean meat content (Pietrain), voluntary feed consumption is a limiting factor for growth.
Copper has a wide variety of systemic functions, many of which could be related to growth. Copper is also a part of the haemoglobin synthesis, so the importance of copper for normal growth, production and reproductive performance has been established. A relationship between copper and immune function has been shown by decreased resistance to infection in copper deficient animals (Jones and Suttle, 1983).
A study by Harmon et al. (1994) demonstrated that inadequate copper status is possible in the absence of copper supplementation in heifer diets and is likely a common occurrence in some dairy herds. The data suggest that inadequate copper status may result in increased mastitis infection prevalence at calving and an increase in clinical severity following challenge, perhaps accompanied by increasd SCC, compared with that observed in cows with an adequate copper status.
ORGANIC COPPER FOR WEANED PIGLETS
The majority of research has shown growth performance benefits from copper supplementation of weanling swine diets (Cromwell et al., 1989). Some research has shown that lower levels of copper as copper lysine may be as efficacious as higher levels of copper sulfate (Coffey et al., 1994). Other research does not show a benefit from copper lysine (Apgar et al., 1995) or chelated copper (Stansbury et al., 1990). The differences in response from the different research studies could be due to a variety of factors, such as source of organic copper, environment, health status, trace mineral status, level of mineral antagonists, (Zn, Fe, Ca, etc.) and other dietary factors (e.g., phytate). It is also important to note that these trials were conducted under different conditions and in different countries.
ORGANIC COPPER FOR LACTATING SOWS
Daily feed intake is not only limited by age, but also by high temperatures. Indeed, in nursing units the ambient temperature is too high for maximal feed intake by the sow. If extra organic copper can improve daily feed intake of lactating sows, then we can expect increased milk production. Higher milk yield will reflect in a faster growth rate of suckling piglets and improved sow condition (reduced weaning-oestrus period).
ORGANIC COPPER FOR FATTENING PIGS
The first aim of this study was to assess the influence of full replacement of inorganic copper by Bioplex™ Cu in the growing phase and finishing phases. The hypothesis of this experiment was that the supplementation of diets with Bioplex™ Cu would have a beneficial effect on the performance of growing finishing pigs relative to inorganic copper. A second aim of this experiment was to investigate whether normal dietary mineral levels could be reduced by 30% using Bioplexes while maintaining normal performance. The experiment was carried out in the same way as the experiment with Bioplex™ Zn described above. There were a total of 120 pigs in the 16 week experiment with equal numbers allocated to each treatment. The starting weight of the pigs was the same for all the treatments (23.7 ± 4.0 kg). Copper levels of the test diets are listed in Table 6. As in the zinc supplementation experiment, the diet containing all organic mineral forms was associated with the faster growth rate (Table 7).
In comparison with the control feed (normal copper content in inorganic form), daily weight gain was improved by 5.9%. In comparison with the feed containing twice the normal copper level in inorganic form, daily weight gain was only with 1.9% higher. Adding twice the normal level of copper in inorganic form improved weight gain by 39%. Notably, the total copper content in the ‘normal level’ diet was much lower than the typical copper content of commercial pig feeds. In grower diets 175 ppm total Cu is typically added while in commercial finisher feeds 20 ppm Cu is added.
As noted in other studies, the daily feed intake was higher in the Bioplex™ group. Comparing normal copper contents, the voluntary feed intake was about 5.7 % higher than in the inorganic copper group. Feed conversion was not improved by the Bioplex™ addition. There was a trend toward higher feed conversion. The slaughter measurements were not affected by the treatment, however backfat thickness was slightly higher in the organic mineral group (Table 8).
Data from Mahan and Shields (1998) shows the mineral content of a whole pig. During the growingfinishing period a pig retains ~80 mg Cu. From the feed analysis, the total copper consumption of pigs from the low (30%), normal, 2X normal and 30% all-organic diets was respectively 1.45, 4.85, 10.00 and 1.46 g. The total copper intake in pigs given normal diet Cu (inorganic) was 4.73 gram. This suggests that total copper excretion is linearly related to total copper intake. In comparison to pigs given the normal (inorganic) dietary level of Cu and taking into account the total feed intake (feed conversion x 85 kg gain), Cu excretion was respectively reduced to 37.8% and 37.5% in pigs given 30% of the normal diet Cu in BioplexTM form and the 30% all-BioplexTM diet. Calculated excretion was not reduced for pigs given normal dietary Cu levels in BioplexTM form, and excretion of pigs given 2X normal diet Cu as BioplexTM was 272% higher.
During recent years, research has proven that additional trace minerals are essential for optimising pig production. In this context, many trials have proven that using highly bioavailable forms of the trace minerals has a positive influence on performance and health status of the pigs. Through better availability, organic minerals can replace inorganic sources at a lower level while performance is maintained or enhanced. This fact holds excellent potential for reducing environmental impact of pig production by reducing mineral excretion. These data indicated that the best performance results were seen if all four minerals, zinc, copper, iron and manganese, were reduced to 30% of normal levels and added in Bioplex™ form.
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