Scientifically Speaking …
By Matthew Wedzerai
FISH SILAGE ON BROILER PERFORMANCE AND MEAT QUALITY
Fish silage, a potential source of protein in animal feed, is simple to make, economical, and reduces environmental pollution. Three studies looked at how fish silage contributes to better growth performance and meat quality in broilers.
The re-emergence of diseases such as the African Swine Fever is pushing high demand in poultry meat products. This puts pressure on poultry feedstuffs, calling for new feed resources and high utilisation efficiency. On the other hand, the ongoing climatic changes, and food-feed-fuel competition brings uncertainty to the future availability of high cost conventional feed resources such as soybean meal and fishmeal. The feed industry is compelled to research into potential sustainable alternatives.
WHY FISH SILAGE First, it is important to note the inevitably common variations in nutrient composition; this results from the differences in type of fish, by-catch or part of the fish that is processed in the silage. Fish silage is a good source of essential amino acids. Its amino acid composition resembles that of fishmeal, provided it is made from the same type of raw materials. Fish silage also supplies appreciable amounts of minerals. Fish silage uses materials which could otherwise be dumped
offshore and cause environmental pollution. This material which consists of fish waste products like heads and frames, and internal organs is utilised into animal feed, thereby reducing environmental problems. On the other hand, fish silage can be produced where the supply of fish for fishmeal production is low or too expensive (which is usually the case). Fish silage making is a simple process that consists of three
basic steps: grinding, acidifying and storage. The anaerobic storage conditions allow long-term storage in a form which is less susceptible to oxidation and rancidity. In addition, acid ensilage decreases the pH, inhibiting the growth of most pathogenic bacteria.
STUDY 1 Researchers from the University of Nayarit in Mexico conducted research to investigate the nutritional value of fish silage on growth performance and meat quality in broilers (day old to 28 days). A fish silage: soybean meal mixture (1:1 w/w) was used to prepare four diets with different inclusion levels (0%, 10%, 20% and 30%).
PAGE 20 SEPTEMBER/OCTOBER 2020 FEED COMPOUNDER
Growth performance The researchers found a higher body weight gain in chickens fed the fish silage-soybean meal mixture compared to the control diet. The inclusion of fish silage in the diet improved feed conversion in broilers – it was suggested that this may be due to hydrolysed protein during silage fermentation process and the supply of essential amino acids such as histidine, threonine, methionine, glycine, alanine and tyrosine present in fish silage. In this study, the content of these amino acids was even higher in fish silage compared to fishmeal. The feed intake in the fish silage diet was similar to the control diet.
Table 1: FCR (g feed/g gain) of broilers fed different levels of the fish silage: soybean mixture
Diet 7
Control 10% 20% 30%
1.99 1.37 1.65 1.86
Trial period (days) 14
21
2.49 1.93 1.91 1.88
1.94 1.90 1.68 1.77
28
2.33 2.09 2.04 2.29
Meat quality For the three inclusion levels (10%, 20% and 30%), juiciness and tenderness were better, and overall meat quality was better according to the panellists who assessed the meat quality characteristics. The researchers suggested that their present findings could be valuable because the addition of fish silage: soybean mixture up to 30% in the feed did not alter the sensory quality of broiler meat.
STUDY 2 Researchers at the Agricultural University of Norway studied the effects of dietary fish silage and fish fat on growth performance and meat quality of broilers (day old to 35 days). The treatments were a control diet, two test diets with 50 g/kg fish silage and different levels of fish fat (6 or 8 g/kg), and two diets with 100 g/kg fish silage and different levels of fish fat (8 or 10 g/kg). To study meat quality, five treatment groups were used: the control diet, and four test diets each containing 50 g/kg fish silage and different levels of fish fat (2, 9, 17 or 25 g/kg).
Growth performance An inclusion level of up to 100 g/kg diet, corresponding to 21% of the
Table 2: Effect of fish silage (FS) and different levels of fish fat (FF) on growth performance of broilers1
Parameter
Feed intake (g/kg) Weight gain (g) FCR
Control 79.1 1310 2.20
A
Experimental diets B
82.3 1365 2.11
79.8 1346 2.18
C
80.1 1362 2.16
D
82.9 1420 2.11
1 Control=0g/kg FS, 2.8g/kg FF; A=50g/kg FS, 6g/kg FF; B=50g/kg FS, 8g/kg FF; C=100g/kg FS, 8g/kg FF; D=100g/kg FS, 10g/kg FF
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