- Compared to growing poultry, exact determination of the relative bioavailability of methionine hydroxy analogue compared to MetAMINO® is constrained by physiological mechanisms in laying hens which often result in overestimation of the relative bioavailability.
- The relative bioavailability of 65 % for methionine hydroxy analogue is applicable in layers and bears no risk in terms of performance depression, as confirmed by three recent feeding experiments performed in Germany, the Czech Republic and Mexico.
- The German trial comprised a current diet with liquid MHA-FA and a diet with MetAMINO® supplemented by 65 % as much (product-based) as in the current treatment. It took place in a commercial unit with about 126,000 hens over a period of 180 days. The study revealed significant savings for the farm management, as well as numerically improved performance with the MetAMINO® treatment.
- The Czech trial comprised an unsupplemented control treatment and two pairs of treatments in a 65:100 replacement manner at two targeted dietary Met+Cys levels. In this case, MetAMINO® replaced MHA-Ca. Supplementation improved performance but there were no differences between the two methionine source treatments.
- The Mexican trial followed a similar design as the previous one but used liquid MHA-FA. As in the previous trial, supplementation improved performance but there were no differences between the two methionine source treatments.
- With respect to all commercial trials, including more the 2 million layers in about 30 trials conducted since 1995, the results of these three experiments exactly confirm the overall outcome.
- The overall conclusion is that MetAMINO® can replace methionine hydroxy analogue in a 65:100 ratio (product-based) without compromising performance but improving profitability when the applied relative bioavailability for the hydroxy analogue product and/or the price ratio between methionine sources is greater than 65 %.
- The outcome of this trial is in line with recent opinion of the European Food Safety Authority (EFSA, 2018) suggesting a bio-efficacy figure of 75 % for MHA-products on molar level which translates into a figure of 67 % on product basis.
Determination of the relative bioavailability of methionine is constrained by physiological mechanisms
In AMINONews® 21 (3) in 2017, the general need for the supply of methionine and cysteine to laying hens was discussed, along with the use – in this context – of various methionine sources to balance the amino acid profile of layer feed in order to meet the methionine+cysteine requirements. The latter part addressed the chemical differences between MetAMINO® (DL-Met) and the hydroxy analogue products of DL-methionine (liquid methionine-hydroxy analog, liquid MHA-FA, methionine-hydroxy analog calcium salt, MHA-Ca), as well as their different relative bioavailabilities. In that article, we placed particular focus on the physiological, and thus methodological, constraints concerning the determination of the relative bioavailability (as well as the relative nutritional value and relative bioefficacy) of methionine sources in laying hens. Of particular interest in this context is the partitioning of dietary methionine and cysteine in the body for various purposes. Laying hens prioritize the maintenance requirements of their vital metabolic functions, as well as keeping egg production (number of eggs, basically reproduction) high, whereas feather growth, body weight gain and egg size are lower in priority. Therefore, a marginal deficiency is not necessarily reflected in egg production because methionine and cysteine will be redirected to this, and used less for feather growth, body weight gain (phase 1) or egg size. In order to explain the background for three recent experiments with laying hens, some aspects of the article in AMINONews® 21 (3) are illustrated by the results of a British trial (Figure 1). The graphs illustrate the bioavailability of liquid MHA-FA relative to DL-methionine for daily egg mass, egg production and egg weight in Lohmann Brown layers. The determined bioavailability of liquid MHA-FA for optimizing egg production was 82 % and was thus close to the maximal value of 88 % (dry matter content), showing that the birds were able to maximize their egg output for a given methionine and cysteine supply status almost irrespective of the methionine source. However, with respect to the egg weight, the response curve for liquid MHA-FA was far below that for DL-methionine, indicating that the priority was to maximize egg output at the expense of egg size. The determined relative bioavailability for egg weight was 53 % – meaning that only 53 % as much DL-methionine as liquid MHA-FA was needed in order to achieve the same egg weight. The daily egg mass, which is the product of egg production and egg weight, finally revealed an intermediate result – a bioavailability of 76 % for liquid MHA-FA. There are in the literature a couple of laying hens studies suggesting similar bioavailability values in the early 70’s for daily egg mass. However, this value still does not represent the recommended value of 65 % which has been established for growing poultry, aquaculture and swine (Lemme et al. 2012; Lemme, A. 2010; Htoo et al. 2012). The European Food Safety Authority recently confirmed a bioavailability of MHA-products of about 65 % relative to DL-methionine (75 % on equimolar level) and attributes this lower efficacy mainly to an increased microbial degradation of MHA products in the gut and a poor utilization of di-, tri- and oligomers of MHA (EFSA, 2018).
These above responses were affected by further factors. In AMINONews® 21 (3) we showed results on total mortality and mortality by cannibalism – the latter often triggered by nutritional shortcomings (Figure 2). Those deficiencies are possibly due to the redirection of methionine and cysteine towards the laying hens’ physiological priorities described above. Development of cannibalism is also discussed in the context of methionine and cysteine deficiency. Interestingly, the patterns on mortality between methionine sources shown in Figure 2 were similar in two independent trials. Moreover, such effects occurred even though the corresponding supplementation levels between methionine sources were already in a 65:100 ratio.
From the above trials and other investigations which had already tested a 65:100 replacement between MetAMINO® and MHA products, a general recommendation was derived that in laying hen feed, MHA products can be replaced by 65 % of the applied amount of DL-methionine without compromising performance.
The recommended relative bioavailability of 65 % for MHA products compared to MetAMINO® was recently challenged in three experiments
Meanwhile, a bachelor’s thesis based on a study at a commercial laying hen farm was written at the University of Applied Sciences in Osnabrück, Germany. Two further laying hen feeding trials with similar experimental design were conducted at the International Poultry Testing Station in Ustrasice, in the Czech Republic, and at the Veterinary Faculty of the National Autonomous University of Mexico. All trials challenged the recommended interchangeability of the methionine sources.
126,000 laying hens were available from ongoing production.
In the German study, two houses with a total of 126,000 ISA Dekalb White hens in commercial operation were available. In these two houses, hens were kept on two floors (31,500 each) with six aviaries per floor. While the eggs could only be recorded per house, it was possible to record feed consumption, live weight and plumage quality per floor (n=2 per treatment). The floors were equipped with 18 feeder lines and 8 nipple drinker lines. The beaks of the hens, which were raised at the same farm, were not trimmed, and were thus intact. In order to avoid differences between treatments other than methionine sources, the hens received the same light, temperature and management during the rearing period.
Hens received feeds supplemented either with liquid MHA-FA or with MetAMINO®. Feeds were produced by the same feed compounder and differed only in the methionine source used. Corn, wheat, barley, sunflower meal, soybean meal and rapeseed meal were the main ingredients. While the liquid MHA-FA represented the current feed in the feed mill and laying hen operation, the MetAMINO® supplemented diet represented the trial feed. The trial, which lasted for 180 days, comprised two feeding phases. The second phase began after about 2/3 of the entire period and was introduced at the same time for both houses and treatments. The feed for phase 1 contained 2,675 kcal/kg or 11.2 MJ/kg metabolizable energy, 17 % crude protein, and 1.30 kg/t liquid MHA-FA. In contrast, the experimental feed contained 0.845 kg/t DL-Met. In phase 2, the crude protein level was lowered to 16 % while the energy and methionine source inclusion were unchanged. During the test period, 61 batches of about 25 metric tons per treatment were produced, meaning a total of 122 batches. Samples were taken from each production and analyzed partly as individual samples and partly as pooled samples. The analysis of the feed samples revealed average lysine levels of 0.84 % and 0.85 % in the phase 1 and phase 2 diets. The methionine+cysteine levels without supplementation were 0.58 % and 0.57 % in the MHA-FA feeds and 0.67 % and 0.64 % in the MetAMINO® feeds. Moreover, analysis confirmed the targeted concentrations of the supplemented methionine sources.
The local conditions allowed for daily recording of feed consumption per floor (individual recording per aviary was not possible). Since the herd size was also updated daily, it was possible to calculate average feed consumption per hen. It was not possible to record daily the number and weights of eggs per floor. Therefore, the egg output and egg size distribution per house (i.e. per treatment) were calculated over a 2-week interval. Egg size distribution also included counts of cracked and dirty eggs, but no impact of diets on this was observed. This was also the case for mislaid eggs, which were counted every day. Likewise, in the 2-week interval, body weights of 100 hens from each floor were determined by means of a wing scale. Also, plumage was assessed using a 4-level quality classification (see Table 1).
The cumulative results for 180 days are shown in Table 1. The results revealed that the use of 65 parts of MetAMINO® had no disadvantageous effects on performance compared to the use of 100 parts of liquid MHA-FA. In addition, egg size distribution did not differ between treatments (Figure 3). From a biological perspective, the results confirmed the interchangeability of the methionine sources at a quantitative ratio of 65:100. Moreover, there is a tendency towards better performance in the MetAMINO® test variant, which is particularly apparent in the mean laying performance, daily egg mass and feed conversion. From the performance over time, it can be seen that the curves for laying performance, daily egg mass and feed conversion for the two treatments show slight differences starting in the 23rd week (Figure 3). As curves were based on 2-weekly samples, it can be confirmed that the documented production figures are consistent with the overall figures obtained in this commercial operation.
The replacement of liquid MHA-FA with MetAMINO® had significant economic advantages.
Analysis of the profitability suggests savings of EUR 1,380 when extrapolating the experimental results of the 180-day period of each treatment to the entire production facility of 126,000 hens, considering only the price difference between products (see box).
Profitability analysis could also be expanded further. Feed consumption per feed variant was determined multiple times daily and is thus a very robust item of data. Laying performance is based on samples and may thus contain some errors, although the course over time does show a continuous difference. Considering only feed intake differences, additional savings of EUR 9,435 were calculated (see table 2). The difference in laying performance and egg mass would improve profitability for the DL-Met treatments even more through the income side.
In a long-term study in Ustrasice in the Czech Republic, brown layers were used.
Another study was carried out at the International Poultry Testing Station in Ustrasice in the Czech Republic. 1,440 ISA Brown layers of 18 weeks of age were divided into groups of 3 x 10 animals in enriched cages. The trial lasted 32 weeks and five dietary treatments were tested. These included a control group (n=12) that received no methionine supplement and had a methionine+cysteine content of 0.53 %. In two treatment groups (n=9 each), the feed was supplemented with 1.2 or 2.4 kg/t MHA-Ca. Compared to this, in treatment groups 4 and 5 (n=9 each), DL-Met was added to the feed at amounts of 0.78 and 1.56 kg/t, which corresponds to a replacement ratio of 65:100 for the two inclusion levels. While the high dosages were meant to cover the methionine+cysteine requirements, the lower dose was meant to be below requirements, in order to make the test more sensitive. The basic composition of the feed included wheat, maize, soy extract granulate and some wheat bran. The crude protein level was 16.6 % and the metabolizable energy was 2,720 kcal ME/kg or 11.4 MJ ME/kg. The average analyzed lysine and methionine+cysteine levels of the control feeds (five productions) were 0.83 % and 0.53 % respectively. Analyses of five subsequent feed productions confirmed the expected amino acid levels.
Results are shown in Table 3 and in Figure 4. All performance parameters were worse in the control group than in the other groups. Supplemented MHA-Ca and DL-Met improved laying performance, mean egg weight, the resulting daily egg mass and feed conversion. The reduction in feed conversion was also due to reduced feed intake. From this it can be concluded that methionine was basically needed for optimized performance. However, differences between the two methionine+cysteine levels are only very small and can be seen only in the small numerical differences in the daily egg mass and feed conversion. However, examining egg size distribution, a small shift in proportions from S toward L can be seen for the higher supplement level (Figure 2). Basically, the optimal methionine supplement level appeared to be more in the range used in feed in the practical test described at the beginning.
Layers held in conventional cages under Mexican production and feeding conditions
A third experiment with a similar setup to the previous trial was conducted in Mexico. The trial, conducted at the Veterinary Faculty of the National Autonomous University of Mexico, used 420 Bovans White layers of 37 weeks of age. They were held in conventional cages and fed sorghum and soybean meal-based diets in isocaloric treatments (2,720 kcal ME/kg or 11.40 MJ ME/kg). Feed analyses confirmed contents of 15 % crude protein, 0.73 % lysine and 0.46 % methionine+cysteine for the basal diet. Five treatments with 7 replicates of 12 birds per replicate were included. A control group with no methionine inclusion, two treatments with suboptimal (50 %) levels of supplemented methionine product (1.125 kg/mt liquid MHA-FA and 0.73 kg/mt of DL-Met) and two additional treatments, which aimed for optimal digestible methionine+cysteine levels, with inclusion levels of 2.25 kg/mt liquid MHA-FA or 1.46 kg/mt of DL-Met were used. Dosages of methionine sources at both levels were in a ratio of 100:65.
The performance parameters after 12 weeks are displayed in Table 4 and Figure 5 and showed a significantly lower performance of the control group, as expected. Whereas increasing the dosage of methionine sources gradually and significantly increased performance, there were no differences between methionine sources in corresponding treatments. Likewise, as observed in the Czech Republic, it can be concluded that supplemented methionine was essentially required for optimized performance. However, egg mass and feed conversion ratio in particular indicated that a suboptimal dietary methionine+cysteine supply would have a detrimental impact on layer performance. Compared to the trial from the Czech Republic, Met+Cys content was 0.54 % (0.46 %+0.083 % DL-Met) in this treatment, similar to the level of the unsupplemented control treatment of the Czech trial, although we have to mention that the protein level per se was lower, and that hens started at higher age in the Mexican case. Also, this trial confirms the interchangeability of the methionine sources at a quantitative ratio of 100:65.
When comparing the corresponding groups treated with MHA-Ca (Czech Republic) or liquid MHA-FA (Mexico) and MetAMINO®, it can be confirmed that the quantitative replacement ratio of 65:100 (DL-Met: MHA-Product) did not have any negative effects on laying hen performance. It can even be concluded that MHA-Ca would not be competitive above a price of 1,625 euros/t compared to DL-Met at 2,500 euros/t.
The results from the recent feeding studies show with impressive consistently that supplying laying hens with adequate dosages of a methionine source is necessary to optimize performance. Indeed, the results confirm that irrespective of the methodological constraints for the determination of the relative bioavailability of Met-sources due to physiological mechanisms, the relative bioavailability of 65 %, as recommended for growing poultry, swine and cultured aqua species by Lemme et al. (2012), Lemme, A. (2010) and Htoo et al. (2012), is applicable to laying hens as well. Also, the most recent scientific opinion of the European Food Safety Authority on efficacy of methionine hydroxy analogue products confirmed a relative bioavailability of about 65 % on a product basis (equimolar 75 %; EFSA 2018). Therefore, the methionine-hydroxy analogue products (liquid MHA-FA; MHA-Ca) are interchangeable with MetAMINO® at a quantitative ratio of 100:65 without compromising the performance of the layers. The outcomes of the three trials presented fit exactly into the summary of all studies which represents the performances of more than 2.2 million laying hens (Figure 6). Remarkable for all these trials is the fact that not only was the reported performance between treatments identical for all criteria, but also that the variation between results was very low. Variation coefficients of 1.44 %, 1.62 % and 2.49 % indicate that in not one single trial did MetAMINO® fail to achieve the same performance as MHA in birds treated at a replacement ratio of 65:100. However, and this underpins the findings of the recent trials, there is always the potential for cost savings provided that the price ratio between MetAMINO® and MHA-products is greater than 65 %.