Dietary Supplementation of a Yeast-Whey Preparation for Weaned Piglets

Abstract Weaning is a stressful period for the piglets and the sow. Stress during weaning is related to the change of diet which can affect the physiology of the gastrointestinal tract, as well as the microbial and immunological status of the animals. In the experiment a yeast-whey preparation was used to decrease the transient growth depression related to reduction of feed intake by the piglets. The piglets were assigned to three treatments. In the control group (I) the animals obtained standard feed mixture used routinely at the farm. In the case of piglets from II and III treatment, the yeast-whey preparation was added in the quantity of 4 and 7%, respectively. Application of 7% yeast-whey preparation to the diet significantly increased the body weight of piglets (p<0.05) and in consequence the average daily body weight gain (p<0.01) in comparison with the control group of animals. Additionally, piglets which were fed the yeast-whey preparation diet had a higher feed intake (p<0.05) and better feed conversion ratio (p<0.05) than those fed a diet without the addition of this preparation. No significant differences were stated for most biological parameters (p>0.05), except for the blood urea level, which was significantly lower (p<0.05) in the treatments where the yeast-whey preparation was used. These results indicated that yeast-whey preparation efficiently suppressed post-weaning diarrhea and improved the performance of the animals.


INTRODUCTION
The weaning period is a strong stress factor both for the piglets and the sow. It is associated with many changes in the weaner's body, including its physiological (related to the gastrointestinal tract physiology and microbiota) and psychical status, thus affecting the reduced ability of the organism to immunologically defend itself [1][2]. Physiological changes affect GALT (gut-associated lymphoid tissue) [3], which are manifested by shortening of the intestinal villi and crypt hyperplasia and leads to increased vulnerability to bacterial infections, especially enterotoxic E. coli strains [2,[4][5].
Weaning involves changes in the diet (the transition to solid feeds) and environment (impairment of earlier established hierarchy and escalation of aggressive behavior) [6][7][8]. This procedure results in transient growth depression which is linked to reduced feed intake [9]. Most often weaned piglets consume the fi rst portion of feed after 24 hours, while in 10% this process can last even 48 hours. Most of the animals adapt to the new nutritional and environmental conditions within 1 -2 weeks. However, some individuals show post-weaning wasting syndrome with growth depression. In order to counteract the growth depression and limit the risk of diarrhea, different dietary supplements are used which are alternatives to antibiotic growth promoters [7,[10][11][12]. They include spray dried plasma, preparations from egg yolks, dried bovine colostrum, dried whey or yeasts Saccharomyces cerevisiae and isolated products of their fractionation (β-1,3/1,6-glucans, mannans). Active components used in feed mixtures for weaned piglets mostly aim to support the growth and development of the animals and to boost non-specifi c resistance to negative environmental factors [13][14][15][16].
The aim of the present experiment was to assess production performance and some chosen hematological and biochemical parameters in growing pigs which were fed a complete feed mixture supplemented with different concentrations of a yeast-whey preparation.

MATERIAL AND METHODS
The experiment was conducted on a pig farm in Korzękwice (Poland) and it was integrated with the production cycle at the farm; high zootechnical and veterinary standards were implemented.
The experiment commenced with assigning randomly weaned piglets (Polish Landrace x Polish Large White) to 3 groups (80 animals each) with an initial body weight of ca. 7.5 kg on the 28 th day of life. The nutritional values of the prestarter mixtures are presented in Table 2. Group I comprised control animals fed a standard solid feed mixture used routinely on this farm (without the tested preparation). The prestarter mixtures for group II and III were supplemented with a yeast-whey preparation at a concentration of 4% and 7%, respectively. The yeast-whey preparation was prepared from slurry of dried brewer's yeast (Saccharomyces cerevisiae) and concentrated sweet whey. The nutritional value of the preparation is presented in Table 1. Piglets were fed the prestarter diet up to the end of the experiment (55 days of age), according to the experimental design. Animals consumed the mixture ad libitum from auto-feeders. The weaners had constant access to automatic drinkers with controlled water fl ow adjusted to their needs. The yeast-whey preparation was made from beer yeast cake and sweet whey by specifi c hydrothermal treatment methods. Production technology prevented the occurrence of reactions that can inactivate the action of active substances in the raw material.
Physico-chemical properties of the yeast-whey preparation: Colour -light cream Taste: sweet and sour Physical form: fi nely ground fl our The experiment involved the determination of the growth rate of the piglets and feed intake during rearing, the number of diarrhea cases and losses, as well as their causes. In addition, blood was collected from the jugular vein of six 55-day-old piglets to determine some hematological (hematocrit -Ht, hemoglobin content -Hb, erythrocyte -RBC and leukocyte -WBC) and biochemical parameters (urea -UREA).
All the obtained results were subjected to statistical analysis using a one-way analysis of variance using Stastica 13.1 software package (Statsoft Inc.). Differences between the groups were analyzed with Duncan test.

RESULTS
The nutritional value of the prestarter mixture (Table 2) conformed to the standards defi ned by nutritional recommendations [17]. The production performance indices of the piglets obtained during the experiment are presented in Table 3. On the day of weaning, the body weight (BW) of the piglets differed only slightly between the groups and ranged from 7.2 kg to 7.7 kg. The mean body weight of the piglets from group II and III was insignifi cantly higher than in the control group.
At 55 days of life, the body weight of the piglets from group II and III was higher, while the piglets from the control group at that time weighted less by 1 kg and 2 kg, respectively. The obtained results indicate that diet supplementation of 7% yeastwhey preparation induced the most benefi cial effect on the growth rate of the animals during rearing (p<0.05). Group II and III piglets also showed signifi cantly higher weight gains, by 15% and 26% respectively, compared with group I (control). The piglets showed a greater preference for the prestarter mixtures supplemented with the yeast-whey preparation compared to group I (control). Feed conversion per 1 kg of body weight gain measured 1.89 kg/kg in the control group, whereas it was signifi cantly lower (p<0.05) in groups II and III (1.74 kg/kg and 1.66 kg/kg, respectively).
The losses and culling rate of the piglets during rearing averaged 9% in the control group and fl uctuated from 1% to 2% in groups receiving the test preparation. The highest number of diarrhea cases was noted in the control group (16 piglets during the whole experiment). In contrast, no diarrhea cases were observed in the experimental groups. The obtained production data (including body weight and losses during rearing) indicate a benefi cial effect of the yeast-whey preparation on the production performance of piglets and weaners.
Hematological parameters remained within the physiological range confi rming the good health status of the animals [18] ( Table 4). In our experiment, we did not notice statistically signifi cant (p>0.05) differences in RBC measurements (Ht, Hb, RBC).
Plasma urea content was reduced in animals fed the mixture with the yeast-whey preparation; it is a benefi cial reaction of the body to the supplement under the study. The signifi cantly reduced (p<0.05) urea level (noted in the groups receiving the yeastwhey preparation in the diet) can be indicative of better protein utilization probably due to lactoglobulins contained in the preparation.

DISCUSSION
After the withdrawal of antibiotic growth promoters from animal feeds (in 2006), studies were launched to search for bioactive substances limiting the negative impact of the so-called immune gap (occurring after the separation of piglets from the saw) and supporting digestion (mostly during transition from milk to solid feed). They include spray dried plasma, yeast preparations containing beta-glucans and mannans composing the yeast cell wall or active substances of milk occurring in the colostrum or whey [6,[19][20]. All of them show multidirectional effects beginning with the mobilization of the immune system in piglets (e.g. by binding pathogenic bacteria as in the case of mannans). Therefore, they show a similar activity profi le as antibiotic growth promoters, but do not increase the drug resistance of pathogenic bacterial strains [16,21]. Mukhopadhya et al. [22] emphasized also that milk hydrolysates, depending on the source and chemical composition, have antimicrobial and antiinfl ammatory properties. Additionally, Cross and Gil [23] confi rmed in their review paper that it was possible to transfer active substances present in cow's milk to other animal species.
The present study was based on a combination of components of bacterial cell wall (mannans and beta-glucans) and whey-derived active substances. The yeast-whey preparation increased the body weight of piglets compared with piglets from the control group, resulting in a more than 10% rise in daily body weight gains obtained in group II receiving dietary supplementation with the 4% yeast-whey preparation. On the other hand, the addition of 7% preparation to the diet increased weight gain by 26%. Evidence to confi rm this hypothesis was also provided by the studies of Pluske et al. [2] and Le Huëron-Luron et al. [24], demonstrating a benefi cial effect of cow colostrum supplemented at 40 -100 g/kg of the diet on body weight gains and feed intake during weaning. In particular, a direct stimulation of the intestines by dietary components was one of the factors exerting a positive effect on these results [3]. Active substances isolated from yeast cell walls, i.e. mannans and beta 3/1-6-glucans also continue to be of great interest [25][26][27]. The obtained results of the research indicate benefi cial outcomes after application of these preparations, including a faster growth rate of piglets and reduced risk of post-weaning diarrhea [28][29]. In the present study, apart from the increased daily body weight gains, the piglets from the groups receiving dietary supplementation with the test preparation showed a greater preference for the feed, whereas incorporation of the preparation in the diet at the level of 7% improved feed conversion per kg of weight gain by 230 g compared with piglets from the control group.
An immunomodulating action was also observed for milk whey both in ruminants and monogastric animals. Cross and Gil [23] reported, based on in vivo studies that cow's milk proteins infl uenced lymphocyte action and antibody response in other animal species. In the present study, the addition of the yeast-whey preparation to the diet reduced the culling rate from 9% in the control group to 2% in piglets fed the test preparation. It was also refl ected by the level of the observed incidence of diarrhea.
No cases of diarrhea were noted in piglets receiving the yeast-whey preparation, while in the control group 16 piglets with diarrhea were noted. However, the hematological studies did not confi rm a greater frequency of infl ammation in the control animals, while haptoglobin level remained at a similar level in all groups of piglets.
The impulse to undertake this type of research was a small number of previous articles regarding the use of dried yeast-whey preparations in piglet nutrition. The main advantage of this type of preparation is the combination of the benefi cial effects of both of these ingredients in the period from weaning piglets on the 28 th to the 55 th day of their life. Dried brewer's yeast has a benefi cial effect on the reduction of the number of pathogenic bacteria in the gastrointestinal tract of piglets due to the presence of mannan-oligosaccharides in the cell wall. However, the use of dried whey, as a by-product of the dairy industry, in combination with dried brewer's yeast resulted in a more effi cient use of feed proteins confi rmed by the lower level of urea in the blood of piglets receiving this supplement in the diet.

CONCLUSIONS
Dietary supplementation of the yeast-whey preparation at the level of 4% and 7% improved the growth rate and feed conversion in piglets (including proteins, as was evidenced by signifi cantly reduced plasma urea concentration). The addition of the test preparation also effi ciently suppressed post-weaning diarrhea.

Authors' contributions
AST coordinated experiment performances and has been involved in manuscript writing. TH performed the statistical analysis and participated in manuscript writing. MK performed the chemical analysis and participated in manuscript writing. BF conceived and designed the study, coordinated experiment performance and has been involved in manuscript writing. All authors read and approved the fi nal manuscript.