THE EFFECT OF FISH MEAL IN THE NUTRITION OF WEANED PIGLETS

: The effects of the use of fish meal in the nutrition of weaning piglets were observed. The trial included 80 weaned piglets of the same genotype (Large White x Danish Landrace) distributed in two feeding treatments. In the first period of the experiment, animals were fed during 10 feeding days, with a pre-starter mixture containing 21.1/20.8% of the crude protein. The second period lasted for 25 days and piglets were fed with mixture containing also 21.0/21.1% of the crude protein. And in the final period of the experiment, which lasted 22 feeding days, the meals were formulated to contain 19.5/19.9% of the crude protein. The control group was fed with standard farm mixtures, while the trial group were fed with mixtures containing 4/3/2% of fish meal. The obtained results showed that the use of fish meal resulted in better average daily gain and feed conversion in starter period (27-51 day).


Introduction
Fish meal is a biproduct of animal origin and is a source of high-quality protein for animal feed. Currently, fish meal is manufactured from species that are caught in commercial fishing and not adequate for human consumption. Inclusion of high-quality protein sources (fish meal) is important for pig diets to manage digestive disturbances in the weaning period.
According to the decision of the EU Commission 9/2001, all the mixtures which contain fish meal can only be produced in feed mills which don't produce or process any other feeds for ruminants or if they are specialized for this purpose. And also they need proper licence from authorised institutions (Sardi et al., 2005). This decision has led to some negative marketing in regard of using animal proteins in livestock feed, which led to further research of the possibility to excluding fish meal from mixtures for pigs and implementing some substitutes.
The weaning period is always stressor to young pigs that typically results in lower feed intake and a decrease in bodyweight for several days immediately after weaning (Hötzel et al., 2011). With a loss of bodyweight, an ileal environment is favorable for the colonization of bacteria resulting in post-weaning diarrhea syndrome (Tsiloyiannis et al., 2001). It is important in the immediate postweaning period to include high-quality ingredients such as fish meal in diets (DeRouchey et al., 2010), which are proven to increase feed intake and growth performance (Berrocoso et al., 2012).
There is increased concern about overfishing of wild capture fisheries, and as of 2011, 28.8% of the world's fish species were overfished (FAO, 2012). This over-harvest has included species used for fish meal production and when coupled with increasing global demand for fish meal has led to an unsustainable situation (Olsen and Hasan, 2012). Soybean meal is the mostly used protein source in pig diets, but it has it's limitations in young pig diets due to anti-nutritional factors, which influences post-weaning diarrhea syndrome (Friesen et al., 1993). Also, it is important to find alternative high-quality protein sources that are more economically efficient and contain minimal anti nutritional factors.
A common practice that inclusion of high quality protein ingredients in piglet diets is the result of their immature and defective digestive system, which can minimize the side effects on digestive function and growth rate in the period of weaning (Che et al., 2012;Sinn et al, 2016).
Fish meal has similar nutritive characteristics like some other alternatives to fish meal, like the plant feed -Ekofish meal used in the nutrition of weaned piglets (Adamović et al., 2006), sows and piglets (Živković et al., 2007a).
Objective of this paper was to investigate the effects of use ultrapure, high protein feed fish meal in diets for weaned piglets.

Material and Methods
The trial included 80 piglets of the same genotype (Large White x Danish Landrace) distributed in two feeding treatments (Table 1). Immediately after the piglets were weaned, groups of 10 piglets were formed on the basis of uniform initial weight, taking into account that in each group the sex ratio is the same. There were 4 repetitions per treatment. All piglets were placed in solid wall boxes, with lattice floor, each containing 10 feeding places. Average initial weight of piglets was 7.64 kg. All piglets came from 8 different mothers, and same father. There were three feeding mixtures for the whole trial period (Table 1.) In the first period of the experiment, animals were fed during 10 feeding days, with a prestarter mixture containing 21.1/20.8% of the crude protein. The second period lasted for 25 days and piglets were fed with mixture containing also 21.0/21.1% of the crude protein. And in the final period of the experiment, which lasted 22 feeding days, the meals were formulated to contain 19.5/19.9% of the crude protein.
The first group of piglets, control, was fed with standard farm mixture and the other group of piglets with mixtures containing fish meal (Table 2). Food and water were ad libitum.    During the starter and grower period, the following production indicators were monitored: body weight, average daily gain, average daily food consumption and feed conversion. The data obtained were processed using the software package "STATISTICA" (Stat Soft Inc, 2012). ANOVA was used while the Tukey test served to determine the statistical significance of the differences between individual means values.

Results and Discussion
Production performances (Table 3.) were shown that during the whole trial period, it was found that there were no significant differences in average feed intake, daily gain and feed conversion. Statistical significance was noted in ADG and FCR during starter period, trial group had better average daily gain (15.64%) and feed conversion (13.63%). In the grower period only statistical difference were noted for ADG where control, group had better ADG for 9.37%. Durring whole trial period there were no mortalities. Some researchers have concluded that piglets fed with products based on soybean proteins can progress almost equally to piglets fed with the fish meal (Min et al., 2003;Sardi et al., 2005). Soybean meal are a very good substitute to fish meal (Ebert et al., 2005a) and because of arginine could be even better than whey protein (Ebert et al., 2005b), but they are pretty inferior compared to casein (Junghans et al., 2004).
Adding lecithin and enzyme to diets based on soybean meal could not reach the same level of feed utilization as the one based on fish meal (Kovčin et al., 2005). According to Sardi et al. (2005) fish meal used in weaned piglet diets can be replaced by almost same amounts of vegetable protein. Some newer studies (Chia et al., 2019) even include insect meal as alternative to fish meal. Živković et al. (2007b), have shown that use of plant based fish meals could be as efficiant as fish meal, and beneficial for suckling and weaned piglets. Jeong and Kim (2015) found no differences on growth performance, in weaned pigs when other products replaced half of the fish meal in diets. Fish meal from different sources can have different effect growth performance (Cho et al., 2012). Jones et al.(2015) concluded that adding 3% fish meal to diet improved ADG, and adding 6% improved both ADG and FCR.
Fish meal is widely used in weaned piglet diets as a highly digestible protein with excellent amino-acid profile and very high level of vitamins and minerals (Sun et al. 2009).

Acknowledgement
The results of the research presented in this paper were financed by the Ministry of Education, Science and Technological Development of the Republic of Serbia, on the basis of the Agreement on the realization and financing of scientific research work of SRO in 2021 no. 451-03-9/2021-14/200022.