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Use of clinoptilolite in piglet diets as a substitute for Colistine

Abstract The effects of adding 2% of natural zeolite, containing a high percentage of clinoptilolite, to the diet of piglets was evaluated by monitoring growing performance and plasma parameters. The diet was also deprived of Colistine, an antibiotic usually added to piglet diets at subtherapeutic levels to prevent gastrointestinal pathology. Sixty-four piglets, weaned at 7.9 kg live weight, were divided in 2 groups of 32 each. The control group was given commercial piglet feedstuffs; for the treated group, 98% of the same feed, deprived of Colistine, was used, with the addition of 2% of a natural zeolite. The trial lasted 36 days. The piglets fed the control diet exhibited greater weight in the first three weeks, after which the differences were not significant. The average daily weight gain in the first week was higher in the control group (+37%; P<0.01) whereas at the end of the trial no differences were found. The feed intake did not show significant differences between groups and, as a result, the Feed Efficiency at the end of the trial was higher in the control group (532 vs. 491, P< 0.05). The plasmatic nitrogen parameters did not show significant differences between groups. Only in the first three weeks post-weaning the group fed the diet containing Colistine showed better ADG, subsequently it can be eliminated and clinoptilolite could favour growth.


Introduction
The post-weaning period is a critical moment in swine rearing. The removal from the mother and the introduction into new rooms with several animals cause considerably stressful conditions for piglets. Furthermore, the change in diet from liquid to solid feed increases the discomfort of piglets and may induce serious pathologies in digestive apparatus. As a result, serious diarrhoea can occur which represents the most frequent cause of death in piglets before 56 days of age (Beers-Schreuers et al., 1992;Gupta and Iyer, 1984).
Subtherapeutic levels of antibiotics have been postulated to prevent diarrhoea; as side effect they can promote growth of animals and improve feed efficiency. The mechanisms of growth promotion by antibiotics include different aspects: they modify the activity of gastrointestinal mucosa, they regulate the absorption of alimentary constituents, influence the activity of the endocrine system and modify the microflora and their products within the gastrointestinal lumen (Visek, 1978). The antibiotic action on the microflora determines great changes in the concentration and in the metabolism of bacteria in the gastrointestinal tract, causing alterations to the absorption, to the motility and to the glandular activity of digestive apparatus. As a result, the incidence of diarrhoea can be reduced. According to Yen and Pond (1990) subtherapeutic levels of antibiotics reduce the bacterial production of ammonia in the intestinal tract and lower its blood concentration, thus increasing the growth of the animals (Visek, 1978). The addition of natural zeolites is assumed to have a similar effect to that of antibiotics, as clay has a great affinity to ammonia. Many studies have been conducted regarding the use of natural zeolites in pig feeds, because of the positive effects it could have on animal health and metabolism. Positive effects on average daily weight gain and on feed conversion rate were observed by Kondo et al. (1969), Han In et al. (1976, Lee et al. (1970), Vrzgula and Bartko (1984) and Castro and Pastrana (1988); on the contrary Shurson et al. (1984) observed that dietary inclusion of 2.5%, 5% and 7.5% of zeolite caused a proportional reduction in the utilization of protein in piglets. Zeolites have particular chemical-physical properties that determine a strong stability of its structure which is not modified by pH values in the gastrointestinal tract. Zeolites have a great ammonia-binding capacity (Barrer, 1978) and for this reason they also act as detoxicant agents along the gastrointestinal tract (Sardi et al., 2002).
Many authors have observed a large increase of the contents of dry matter of the faeces (Malagutti et al., 1997;Benatti et al., 1994;Monetti et al., 1996) showing positive effects in the prevention of diarrhoea and in the operation of cleaning and removing of manure from piggery.
In this study, the effects of adding 2% of natural zeolite, containing a high percentage of clinoptilolite, in the diet of piglets have been evaluated by observing growing performance parameters and plasma parameters. The diet has been also deprived of Colistine, antibiotic normally added to the diet of piglets at subtherapeutic levels to promote growth.

Material and methods
Sixty-four Large White x Landrance piglets, half castrated males and half females, from 8 litters, weaned at mean live weight of 7.9 kg, were divided in 2 groups of 32 animals each and housed in pens which held 8 animals. The piglets were homogeneously chosen with respect to sex and weight.
The control group was given commercial piglet feedstuffs (Control diet). For the treated group, 98% of the same feed was used with the addition of 2% of a natural zeolite containing a high percentage of clinoptilolite (Zeolite diet). The main chemical and mineralogical properties of the zeolite used are displayed in Table 1. Furthermore, the treated group was totally deprived of Colistine, an antibiotic present in the control diet for 120 mg/kg. The diets were provided ad libitum and the animals had free access to drinking water. The composition of the diets is shown in Table 2 and the analytical characteristics of the diets in Table  3. The chemical analysis of feedstuffs was carried out in accordance with the recommendations of the Italian Association for Animal Production (ASPA, 1980). The piglets were individually weighed at the beginning of the trial and once a week for the following 5 weeks. The trial lasted a total of 36 days. Data were recorded weekly regarding Live Body Weight (BW) and Average Daily Weight Gain (ADG), along with collection of blood samples. On the same 8 animals from every group, blood samples were collected in test tubes containing EDTA 2 hours after feeding. Blood samples were centrifuged (3000 rpm x 10 min.) and plasma stored at -20°C. Plasma parameters (uric acid, urea, creatinine, total protein) were determined using enzymatic spectrophotometer assays (Biochemia Boehringer, Italia) while αamino-nitrogen was determined using the Goodwin method. The Feed Intake (FI) of each pen was recorded at the end of the trial to calculate the Feed Efficiency (FE).

Statistical analysis
where µ was the general average, α was the effect of the diet, β was the correction factor for the covariate, x was the average of the observations, x was the effect of the pen and γ was the error. A statistical model without the effect of the pen and without correction factor for the covariate was employed for plasma parameters, Feed Efficiency and Feed Intake.

Results and discussion
All piglets were in good health before and throughout the trial. Firm faeces were observed throughout the study with no occurrence of diarrhoea. No significant differences between the groups were observed as attributable to pen effect. The Live Body Weights of piglets are reported in Table 4. The piglets were weighed every week and significant differences were observed in the first 3 weeks; the piglets fed the control diet showed greater weight: 9503g vs. 8653g (P<0.01) after 7 days, 12767g vs. 11686g (P<0.01) after 14 days and 16884g vs. 15420g (P<0.01) after 21 days. At the end of the trial, the differences were not statistically significant. The Average Daily Weight Gain is shown in Table 5. The ADG showed the same trend that BW did. The higher values were observed in the control group during the whole experimental period, although the differences were not significant in the last 2 weeks. The overall ADG was 508 g/d  for the control group and 466 g/d for the treated group fed a diet without Colistine. It stands to reason that Colistine is efficient until the third week; in the first week especially the ADG of the treated group is lower (-37%), whereas in the following weeks the differences reduce. The lower ADG also depends on the lower energy and protein content of the diet with the addition of 2% of zeolite, which is an inert material. In fact, the amount of energy for the maintenance of animals is unvaried, while the amount of energy available for growth is much lower than 2 % in the diet with zeolite added. The lower energy and the absence of antibiotics reduced the ADG, even though no enteritic syndrome with diarrhoea was observed and no veterinary treatments were necessary. The Feed Intake of the animals did not show significant differences between groups and, as a result of the lower ADG of the treated group, the FE at the end of the trial was higher in the control group (532 vs. 491, P< 0.05). The decrease in ADG and FE confirms the conclusions of Poulsen and Oksbjierg (1995) who suggested that the animals were unable to compensate for the energy diluting effect of zeolite by increasing the feed intake. The plasma parameters reported in Table 6, are consistent with previous studies on piglets of the same age (Bassaganya-Riera et al. 2001, Parisini et al. 1989. No significant differences were found, but piglets fed the diet containing zeolite showed a tendency toward a lower content of urea (P<0.09) and creatinine (P<0.11), probably because of the absorption of excess ammonium by zeolite in the gastrointestinal tract, which causes a reduction of plasmatic urea.

Conclusions
The piglets fed the diet with the clinoptilolite and without Colistine showed a decrease in ADG and an increase in FE. The differences were higher in the first week and reduced in the following weeks, so the effect of Colistine cannot be disregarded during first 7 days post-weaning. Subsequently Colistine can be excluded from the diet and zeolite may have positive effects on animal health and metabolism by possibly absorbing ammonia in the gastrointestinal tract.
The addition of clinoptilolite to the diet of piglets in the amount of 2% of total feed is not sufficient to determine significant differences in plasma parameters concerning nitrogen metabolism.
The paper must be attributed equally to the authors.