Be-Long Corporation’s Blog

Suppliers of feed phosphates announced around Christmas 2007 that supplies of phosphates would be insufficient to meet orders from the animal feed industry. In some cases only 30% of ordered tonnage was supplied.

This had a serious impact upon poultry feed manufacturers and producers, in terms of ability to supply stock with required levels of phosphorus and the cost of phosphorus in the diet. While the initial crisis has subsided, concern over phosphate supply and cost going forward remains.

The shortage is a result of exceptionally high demand for phosphorus-containing fertilisers. Feed phosphates and fertilisers are both produced from a common raw material - phosphoric acid - and extra fertiliser production has resulted in a shortage of it for feed phosphate production.

Higher fertiliser demand has resulted from increased global plantings of cereals and protein crops in response to tight global stocks and subsequent soaring feed prices.

So what are the implications for poultry production? There are two key effects: First, there is the difficulty in meeting the phosphorus requirements of birds and, second, it has increased the cost of feed.

This puts further pressure on feed formulation, as nutritionists look to maximise stocks of feed phosphates, while keeping formulation cost down. Nutritionists will attempt to conserve feed phosphate stocks by reducing levels in feeds and using alternative ingredients.

But these attempts could have implications on production and it is worth considering how best it should be managed.

Reducing levels in feed

Any reduction in phosphorus below recommended levels must be carefully managed. If reducing phosphorus, several factors should be considered.

Broiler starter formulations should be left unchanged. Phosphorus levels are crucial for skeletal development and growth, and any changes in specifications at this time can have serious implications for welfare and performance.

If reducing the phosphorus levels of broiler feeds, then first consider the final withdrawal of feed, and work backwards towards the grower diet. This approach involves least risk of negatively affecting bird welfare and performance. In terms of volume used, the increasing feed intake of broilers during the latter phase of the grow-out cycle will result in a significant reduction in added phosphate use.

When setting a minimum specification level, bear in mind that broilers show deficiency symptoms at levels of available P of 0.29% of total diet (as is). Also take into account other factors that may increase phosphorus requirements, such as disease exposure, toxin levels in feed and susceptibility to rickets.

Any reduction in phosphorus will alter the calcium-to-available-phosphorus ratio. Calcium levels should be adjusted to keep this at 2:1 to maintain good bone health.

It is worth checking the specification levels of other nutrients which affect bone mineralisation calcium, magnesium, manganese and vitamin D3.

Formulating to digestible phosphorus can potentially reduce the volume of mineral phosphate required in the feed while maintaining correct formulation. But if doing this, great care must be taken to ensure that raw material values are amended.

Lastly, breeder formulation specifications should only be considered if absolutely necessary. Low phosphorus levels will compromise eggshell quality, hatchability and progeny viability.

Alternative ingredient strategies

There may be a benefit in using phytase enzymes. But, again, a number of factors should be considered before embarking on their use.

If adding phytase to diets that have previously not included phytase, check with the supplier that the raw material and feed specification values used in ration calculations are correct. Also check correct values have been used for phosphorus, calcium, sodium and other minerals.

Feeds already containing phytase may benefit from an increased dosage of the enzyme, both in terms of phosphate sparing and cost saving. Consult the supplier as to the best way to achieve maximum benefit and ensure the mineral content of the feed is kept in balance.

When using phytase in breeder feeds, it is particularly important that the raw material and specification levels are managed to keep mineral content balanced, particularly the calcium-to-phosphorus ratio.

Alternative sources of mineral phosphates may be available, but the phosphorus and calcium contribution may not be the same as for the more traditional phosphates, both in terms of absolute level and availability. Quality should be consistent, to be certain that the correct level of minerals will be supplied to the birds.

And lastly, watch out for heavy metal contamination in mineral phosphates offered.

Increase in the level of HTRP also reduced the feed intake significantly. As a result of which there was significant improvement in FER as well as PI in broilers with HTRP diets. There was also reduction in the cost of feeding and increase in the net return over feed cost due to incorporation of HTRP. Maximum net return over feed cost was noted in broilers assigned T3 diet. Hence, it was concluded that 80% HTRP can be incorporated instead of DCP in broiler diets economically.

However, due I to high demand and scarce availability, its cost is steeply increasing. Therefore, to reduce the cost of mineral mixture, it has become imperative to use alternate and economical phosphorus supplements.

One of the alternates is rock phosphate (RP), which is available in plenty at much lower cost. But on account of high level of fluorine in it10, its use is limited. To reduce the fluorine content of rock phosphate usually it is heat-treated. The heat-treated rock phosphate (HTRP) also contains fluorine but at much lower level than RP.

Therefore, present study was planned to see the utilization of heat-treated rock phosphate instead of DCP in broilers.

All the diets were same except the change in phosphorus supplement. Mineral mixture as reported in the Iiterature⁶ was used @ 3% in control diet. Diet I had only DCP as phosphorus supplement. Whereas, in other diets, DCP was replaced using HTRP @ 60, 80 and 100% (T2, T3, and T4). The fluorine content of HTRP was only 1.81 %. Each diet was randomly allotted to three replicates of 8 chicks each.

The experiment was conducted for a period of 6 weeks. During the experiment, weekly body weight, feed intake and left over feed was recorded and weight gain and feed efficiency ratio (FER) was calculated. Feed samples were analyzed for proximate constituents¹. While calcium and phosphorus contents were estimated by titrimetric method⁹. The energy content of the samples was estimated using titrimetric method⁵.

The performance of birds was measured in terms of weight gain, feed intake, feed efficiency ratio, performance index and economics of feeding. The performance index (PI) was calculated as detailed by Bird². The data obtained during the study were analysed⁷ and significance between the treatments were tested using Duncan’s multiple range test⁴.

The PI was maximum and significantly (P
During 4-6 weeks (Table 2), increase in the level of HTRP also increased the weight gain significantly. But complete replacement of DCP reduced it significantly (P<0.05). Feed intake was maximum and significantly higher in broilers assigned T1 diet. But inclusion of HTRP led to significant reduction in it.

Minimum feed intake was noted in broilers assigned T4 diet. FER improved significantly (P<0.05) with increase in the level of HTRP. Maximum and significantly higher FER was observed in broilers assigned T4 diet. While, it was minimum and significantly lower in those allotted T1 diet. The PI was maximum and significantly higher in groups assigned T3 diet and was significantly lower in those allotted control diet.
Table 2. Performance of broilers on MM containing HTRP instead of DCP (4-6 weeks)

Studies revealed that inclusion of HTRP instead of DCP increased the weight gains of broilers significantly, however, it was true only up to inclusion of 80% HTRP. Complete replacement of DCP led to significant (P<0.05)- reduction in it. Thus, minimum weight was gained by the broilers assigned T4 diet.

As it was heat treated rock phosphate, it has low levels of fluorine (1.81%) and probably phosphorus was more available hence it improved the weight gain of broilers. The amount of fluorine ranged from 79.5 ppm in D2, 106.0 ppm in D3 and 132.5 ppm in D4. While the maximum and safe dietary level of fluorine in broilers is 300 ppm⁸. Thus, in all the groups fluorine level was within the tolerable limit.

Feed intake reduced due to inclusion of HTRP. It was minimum and significantly lower in broilers assigned T4 diet. As a result of it, FER improved significantly in HTRP groups but among these groups, differences were not significant (P>0.05). As like FER, PI also improved significantly due to use of HTRP. On account of higher weight gain and lower feed intake besides lower cost of HTRP, replacement of DCP led to significant reduction in the feeding cost of broilers.

However, among HTRP groups (T2, T3 and T 4) differences were non significant. The net return over feed cost also increased due to use of HTRP. It was higher and statistically similar in groups assigned T2 and T3 diets containing 60% and 80% HTRP instead of DCP. Hence, it was concluded that up to 80%, HTRP can be used instead of DCP in the mineral mixture of broilers economically.
Table 3: Performance of broilers on MM containing HTRP instead of DCP (0- 6week).

“We are at the end of the era of unlimited cheap supplies of agricultural raw materials and much of future thinking on driving innovation is how we deal with that,” said Mr De Greef.

“One is increasing substitution. People outside the feed world probably have no idea about how good the feed industry is at accessing oils, energy or amino acids, and mixing and matching them to achieve the lowest price.”

Feed additive manufacturers also have no reason to fear the growing use of biofuels by-products in animal feed because most plants are deficient in the same substances and meat producers will still need to supplement their animals’ diets in the same way they do now. The two will co-exist, he said simply.

“I think there will be a renewed attention to substitution. There will certainly be new opportunities provided by fuel crops because there will be a protein fraction in those.  The ability of the feed industry and its labs to further increase substitution possibilities will be probably the most effective way to address that issue.

Even the further expansion of by-products from the next wave of biofuels is unlikely to pose a threat to the feed additive industry, said the EuropaBio Secretary General.

“There will be more substitution as by-products from second generation biofuels come on-line but there will also be an increasing place for specific additives. So even in a world where you have a broader range of protein sources available, my guess is that, by itself, this will not stop or reduce the use of lysine or methionine because virtually all crop sources are deficient in the same amino acids.”

Mr De Greef is also sceptical that the development of lysine or methionine-rich crops such as maize can pose any serious threat to those who produce these materials by fermentation.

Measure of P utilisation.

No element is ever completely absorbed and utilised. A fraction is inevitably lost in the normal digestive and metabolic processes. Different research techniques are used to determine as close as possible, the part that the animal will be able to utilise. From these methods an array of terminology is used to quantify the “utilisation” or “bioavailability” of phosphorus (includes “bio-availability; apparent digestibility; true digestibility; retention” and others). “Bioavailability” and “digestibility” are most often used. These terminologies are often used out of context as suggested by the researchers and should not be confused with one another.

Definitions

Bioavailability. That proportion of a nutrient that can be absorbed and/or utilised by the animal to meet its net requirements. Or that proportion of a mineral that is retained in the body

Apparent digestibility. The amount of Phosphorus ingested minus the amount voided in the faeces, including endogenous losses.

Earlier trials were mainly carried out on chicks using bone parameters (tibia ash percentage or toe ash percentage to reflect relative biological value (RBV). This seems to be the most appropriate technique to determine bioavalability because of the fact that more than 80% of the phosphorus is transferred to the skeleton (Zwart, 1999). The phosphorus level in the feed must however be below the phosphorus requirement of the animal (Potter et al., 1995).

Although this technique seems ideal, it is worth noting that these P bioavailability studies do not measure true bioavailability but generally compare P sources on a relative basis (as shown in Table 1). The performance of test phosphates is compared to that of a reference standard phosphate (Waldroup, 1999). The RBV can be 100% or greater, depending on the reference phosphorus source.

Often, in plant feed sources, available P is defined as “total P” minus “phytate P” because it is assumed that phytate P is not digestible and non-phytate P is fully digested. In most feed tables this concept is used to determine the value of P to the animal. It is however clearly demonstrated by Van der Klis and Versteegh (1996), that the absorbability of P from plant feedstuffs is higher than “total P” minus “phytate P” while the absorbability of non-phytate P varies from 55 to 92%. Many feed tables consider inorganic phosphates as a non-phytate source and thus completely available to the animal, however, that is not the case. This illustrates the necessity for the evaluation of the P absorbability from all feedstuffs (inorganic, plant and animal origin)

Apparent tract digestibility of P is also frequently determined (Tables 2 and 3). Dellaert et al. (1990) concluded that the apparent total tract digestibility of P is the most efficient criterion to evaluate the nutritional value of various feed phosphates in pigs, compensating for potential confounding factors. The main factors are the endogenous P portion present in the faeces and the P content of the urine fraction. Compensation for these fractions (true digestibility) is considered to be a very good reflection of P bioavailability. These effects can be minimised by keeping the P content of the experimental diets below the recommended P requirement of the animals (Jongbloed et al., 1999). This can be verified if the results from urine analysis showed values below or near to the detection limit (<25 mg/L). In balanced diets the concentration of P in the urine of piglets fed above the P requirement oscillates between 150 and 400 mg/L (Mulder and Jongbloed, 1985). In poultry an adequate ileal sampling method is available for chyme sampling (Van der Klis, 1993). This implicates that the urinary P excretion does not interfere with the analyses at ileal level.

Apparent digestibility is a valuable measurement of the potential of the P in feedstuffs, with the precondition that the P content of the experimental diets is below the recommended P requirement of the animals. This is most likely the most practical way to express the value of the P component in a feedstuff.

How do these techniques reflect on inorganic phosphorus sources?

Over the years, many studies on the utilisation of inorganic feed phosphate supplements by animals were done. These studies showed distinct differences in utilisation between different generic sources as well as within broadly defined sources of the same description. In spite of these results, related research where inorganic phosphates were used (phytase enzyme work, digestible requirement determinations, etc.), differences in the utilisation of different inorganic P sources are seldom accounted for. In many of these studies dicalcium phosphate (DCP) sources are used without a description of the source itself (i.e. hydrated or anhydrated or to the digestibility of it). It is postulated that much of the variation between studies of the same kind can be partly attributed to these factors. The dilemma, that the Nutritionist is confronted with, is to assign the correct available/digestible value of a P source in order to formulate on.

Results of a trial reported by Waibel et al. (1984) show the determination of bioavailability by tibia ash relative to a mono-dicalcium phosphate (MDCP) reference source (Table 1). Two noteworthy conclusions from the data are:

Relative available values is a handy way of ranking feed phosphates in order to determine nutritive value relative to a reference source (in this case, MDCP). As shown these values are dependent on the reference source used. It is therefore possible to obtain values greater than 100 % and difficult if not impossible to compare results of different studies with each other. Variation in bioavailability within sources with the same generic description can be enormous. This is emphasised by the 32; 31 and 18-percentage units difference respectively between the lowest and highest values for MDCP, DCP and defluorinate phosphoate (DFP) in Table 1. To use average bioavailability values for generic described products without knowledge about the specific product can lead to large errors. Although it shows on average that there is about a 5% difference in bioavailability between a MDCP and a DCP source, this could be misleading if accepted as a generic difference.

Results on trials where apparent digestibility (reflected as bioavailability) of feed phosphates were determined are shown in Tables 2 and 3. The work reported by Van der Klis & Versteeg (1996), shows the same ranking as with the relative bioavailable values shown in Table 1 for MDCP and DCP. However, these values are lower than the values in Table 1 due to the quantitative way it was measured. Digestibility values determined by this method could help the Nutritionist to give a practical value to the different sources. Part of the variation as shown in Table 1, where feed sources were described as MDCP, DCP or DFP, can be explained from the values in Table 2. The difference between an anhydrous DCP and hydrous DCP resulted in a 22-percentage unit difference in available P. It is also postulated that part of the variation in the MDCP figures can be because of the same phenomena.

To categorise inorganic feed phosphates within a generic group more accurately, a number of factors can be monitored within reason. These differences (type of product) are mainly dependent on the chemical reaction and the factors influencing this reaction. The dynamics of these reactions dictate that all end products are chemical mixtures of different phosphates. That means that any conventional inorganic feed phosphate is a mixture of different compounds (i.e. a commercial mono-calciumphosphate (MCP) source will always contain some DCP as well).

DCP

Control over the production process (temperature, control of the chemical reaction, etc.) determines the differences in DCP composition. Too high temperatures (uncontrolled reaction) can result in the evaporation of the water of crystallisation to form an anhydrate product. As shown in Table 2 this can have a detrimental effect on digestibility/bioavailability. Ways for the Nutritionist to determine if a product is an anhydrate product is first to look at the P value. The loss of water of crystallisation would “concentrate” the product to result in elevated P values. Typically, a dihydrate DCP would contain about 18% P, while an anhydrate DCP can contain up to 20% P. Another way is to do a moisture analysis. A dihydrate would loose more moisture when dried at temperatures exceeding 100oC than an anhydrate product. A third method would be to analyse the product by X-ray defraction (Kemme et al., 2001), which will distinguish between the different chemical properties of the source. The most accurate, however, would be if a manufacturer can provide digestibility (bioavailability) figures for their specific product tested in vivo at a reputable institution employing sound techniques.

MCP/MDCP

Mono-calcium phosphate and mono-dicalcium phosphate products are a chemical mixture of MCP and DCP. Products are classified as a MCP if the P derived from the MCP fraction constitutes more than 80% of the product with DCP making up the rest. In South Africa no purely classified MCP is currently available on the market. The data in Table 3 shows however, that certain locally produced phosphate products can compete favourably with the best in the world.

As for DCP, MDCP can differ substantially in composition and bioavailability as shown in Table 1. The MCP to DCP ratio can vary from lower than 50% P from MCP up to 80% P from MCP. The differences in bioavailability between MCP and DCP for pigs (Table 3) of about 12 percentage units shows that the characteristics of a MDCP is crucial to assign a realistic value to the product. The specific MDCP (local produced product) referred to in Table 3 has a known ratio of P from MCP of 75% and P from DCP of 25%. This is most probably the reason that bioavailable values do not differ significantly (P < 0.05) from the MCP described samples (80% P or higher from MCP). The lower bioavailability value obtained for the USA produced MDCP is most likely because of a different ratio of MCP to DCP in the product. As for DCP, a MDCP can be produced as an anhydrated product (di- and monohydrated product for the DCP and MCP fractions).

To be practical, two procedures could be followed to determine the MCP to DCP ratio in a MDCP source.

The P in a pure MCP is fully water soluble (100%) and the P in a pure DCP is insoluble (0%) in water (CEFIC 1999). By the determination of the water soluble P in a product (or as provided by a manufacturer), the ratio of MCP to DCP can be determined. I.e. water-soluble P content of 75% would indicate a product of which 75 % of the P content is derived from MCP and 25% derived from DCP.

As the DCP component in a MDCP raises, so would the total Ca content (DCP is higher in Ca than MCP - typical 24% versus 16%). A Ca to P ratio of about 0.8 could indicate a product of which 70% plus of the P is obtained from MCP, while a ratio of higher than 0.9 Ca to P could indicate a product of which about 50% of the P is obtained from MCP. These ratios can help the Nutritionist to characterise the type of product in question and adapt availability values accordingly.

As for DCP, the most accurate determinant would be when a manufacturer can provide bioavailability figures for their specific product tested in vivo at a reputable institution employing sound techniques.

General remarks

The Nutritionist must be fully aware of the pitfalls in the quest to determine and quantify the nutritional value of the phosphorus in feed sources. Several methods are used to test the digestibility of phosphorus sources. The test results are expressed either as digestibility or as relative bioavailability (expressed as relative biological value (RBV)). These should not be confused with one another. The digestibility is given as a digestibility coefficient < 100% that can be used when calculating dietary digestible P. Relative bioavailability obtained from performance parameters (toe ash and other response parameters) ranks feedstuffs relative to a reference source, which makes it difficult to use it in quantitative terms. The RBV can be 100% or greater, depending on the reference phosphorus source.

Available P in plant feed sources, defined as “total P” minus “phytate P” could lead to the under or over estimation of a feedstuffs potential since not all non-phytate P sources are equally available. It must also be remembered that P from animal origin and inorganic P sources are not part of such a system and need to be evaluated differently.

Apparent digestibility is a valuable measurement of the potential of the P in feedstuffs, but with the precondition that the P content of the experimental diets is below the recommended P requirement of the animals. This is most likely the most practical way to express the value of the P component in a feedstuff.