Fish silage for feeding livestock

Preparation methodology

Chemical composition

Use for feeding

Conclusions

Bibliography

R. Pérez

The author can be contacted at Departamento de Producciones Complementarias,

Ministerio del Azúcar, Havana, Cuba.

Preserving by-catch (scrap) fish and fish wastes or residues (heads and offal) in the form

of silage and using them as feedstuff for livestock is not a new idea (Cameron, 1962;

Zaitsev et al., 1969; Smith, 1977). The problem lies in the commercial implementation.

Fish silage, unlike fish-meal, does not come in a bag; it is semi-liquid, messy and smelly.

This means that most livestock producers will require prior convincing, sufficient training

and extreme perseverance before it can be successfully incorporated into animal feeding

systems. Indeed, perhaps one of the reasons for the need for this article is that, until now,

fish silage has remained mostly an academic question. Furthermore, while neither

fishermen nor fish processors tend to be livestock producers, and vice versa, the fact

remains that the edible flesh of most types of fish represents only 40 percent of the total

weight, which means that, if not converted into fish-meal, some 60 percent could be used

as a protein feed resource. One country that rapidly adopted the technique for producing

fish silage, particularly for feeding beef cattle, is Cuba. In the beginning, acid silage was

promoted (Alvarez, 1972; MINAG, 1975), but today, for both economic and safety

reasons in the preparation procedure, by-catch and fish wastes are simply preserved in

molasses.

Preparation methodology

The technique for making fish silage is cheap and simple (Windsor and Barlow, 1981). It

can be made from by-catch or fish wastes, which are preferably chopped or ground prior

to the addition of organic or mineral acids or of a carbohydrate source for fermentation.

The presence of mineral or organic acids or the lactic fermentation decreases the pH,

which inhibits the growth of bacteria, and hence enables long-term storage of the raw

material. Fish silage made with organic or mineral acids is commonly referred to as acid

fish silage, while that which requires the addition of a source of carbohydrates and

anaerobic storage conditions is known as fermented or biological fish silage.

1 - Liver-protein utilization values for different protein sources - Valeurs

d'utilisation des protéines dans le foie pour différentes sources de protéines -

Valores de la utilización de las proteínas a nivel hepático de distintas fuentes

Parameter Fish

silage

Fish-

meal

Saccharomyces

yeast

Torula

yeast

Casein

Liver-protein utilization

(%)

4.76a 5.47

a 3.06

b 3.50

b 5.32

a

Source: Alvarez, 1972. ab

Mean in same row without letter in common differ at p<.05.

2 - Variation in pH of fish silage made with different sulphuric acid solutions and

substrates - Variation du pH de l'ensilage de poisson fait avec différentes solutions

d'acide sulfurique et différents substrats - Variación del pH del ensilaje del pescado

con distintas soluciones de ácido sulfúrico y sustratos

Sulphuric acid solution (ml): raw

material (kg)

Fish silage Fish silage mixed 1:1 (v/v) with

final molasses

Start 72

hours

35 ml:by-catch 1.60 3.54 4.97

35 ml:fish wastes 2.00 2.75 5.00

40 ml:by-catch 1.58 3.10 4.69

40 ml:fish wastes 1.70 2.30 4.47

50 ml:by-catch 1.40 2.04 4.28

50 ml:fish wastes 1.50 2.00 4.30

Source: Penedo, Cisneros & Rodríguez, 1986.

In both types of silage, during storage, endogenous, proteolytic enzymes break down the

tissue protein to low molecular weight peptides and amino acids that remain soluble and

stable (Green, Wiseman and Cole, 1983). Apparently, under normal storage conditions,

degradation of the amino acids is not of great importance. In fact, Gildberg and Raa

(1977) showed that, in fish silage stored for up to 220 days, less than 8 percent of amino

nitrogen is released as ammonia. Nevertheless, at temperatures exceeding 30°C,

tryptophan, methionine and histidine tend to decompose (Machin, 1990).

Another way to preserve by-catch and fish wastes is to mix and store them directly in

sugar-cane molasses. A brief description of all three methods follows.

Acid silage

Acid fish silage is made from by-catch or fish wastes, which are preferably chopped or

ground, placed in non-metallic vats, mixed with an acid solution and stirred several times

daily for three to five days until liquefied (Cervantes, 1979). It can contain from 27

percent (Machin, Young and Crean, 1982) to 35 percent (Domínguez, 1990) dry matter.

The lowered pH prevents bacterial putrefaction, which allows the silage to be stored for

several months. Acids that can be used in this process are the organic acids propionic and

formic (Rattagool, Surachatmrongratane and Wongchinde, 1980; Wiseman, Green and

Cole, 1982; Machin, Young and Crean, 1982), and certain mineral acids, either sulphuric

or hydrochloric (Alvarez, 1972; Machin, 1990).

In Cuba, Alvarez (1972) used a concentrated solution of sulphuric acid and water (1:1

ratio by volume) to determine the optimal proportion of acid solution for preserving fish

wastes. The objective was to compare the nutritive value of the protein in fish waste

silage to those of fish-meal, two types of yeast and a casein (control). For this purpose,

liver-protein utilization values were determined in rats (Table 1). The fish wastes were

not chopped and the quantities of acid solution used were 20,30,40,50,60,70, 80 and 90

ml/kg of raw material. The mixture offish wastes and acid solution was stored in closed

plastic tanks and stirred for three minutes, three times a day, for a period of five days.

The amount of 60 ml of acid solution per 1 kg of fresh fish waste was selected as

optimum. After five days, the pH of the mixture was 1.8, and prior to use it was

neutralized to a pH of 5 by the addition of calcium carbonate. Later, Cervantes (1979)

showed that whole by-catch could also be preserved using the same concentration and

proportion of sulphuric acid solution, 60 ml/1 kg of a 1:1 mixture. If ground fish wastes

were used, however, they could be preserved using half the amount of acid solution, only

30 ml/1 kg.

In 1986, Penedo, Cisneros and Rodríguez compared by-catch to fish wastes as raw

material for fish silage. Three different amounts of commercial sulphuric acid -35, 40 and

50 ml - were added to 700 ml of water. Each solution was subsequently mixed with 1 kg

of either by-catch or fish wastes. After three days, the silage material was combined with

an equal amount (volume) of final molasses (Table 2). It was emphasized that, if the

silage was to be used within three days, the 35 ml solution would be sufficient; if it was

to be kept for 15 days, the 40 ml; and if it was to be stored for one month or more, the 50

ml. The authors stated that by-catch was inferior to fish wastes because it contained more

than 9 percent of extraneous, calcareous matter, mostly in the form of large crustaceans.

The problem was that the acid solution could not easily attack the organic matter within

the shell causing putrefaction and a disagreeable odour. Domínguez (1988) suggested that

one general rule when using other types of acid might be to adjust the pH to below 4.

In Cuba, between 20 000 and 25 000 tonnes of acid fish silage was produced annually

from 1968 to 1990, in seven factories along the coast, set up and run by the Ministry of

Agriculture to provide a protein-rich feed for ruminants. The process used for both by-

catch and fish wastes, or a combination of the two, was based on the use of concentrated

commercial sulphuric acid and not on the use of the previously described acid solution.

This was because of the large size of the operation, easily between 5 and 8 tonnes per

batch. The raw material, which itself contained a considerable amount of water, was

placed in concrete tanks situated in sheds and then completely covered with water (at

least 2.5 cm above the fish line) before the concentrated commercial sulphuric acid was

added. The acid was added at the rate of 8 to 9 percent by weight or 5 percent by volume

(1 litre weighed 1.75 kg), which represented 50 litres or 90 kg of commercial sulphuric

acid per tonne of raw material.

Over a period of three days, the mixture was stirred two or three times a day. If the raw

material happened to contain a significant amount of large pieces or shellfish, they were

removed by hand and/or the number of stirring days was adjusted accordingly. After the

material had liquefied, the oil, which had separated and surfaced, was skimmed off for

use in concentrate rations for calves. The final product, commonly referred to as protein

paste, was neutralized to a pH of 6 by adding calcium hydroxide or carbonate. It was used

in commercial cattle feedlot operations in a ration of 1:1 with final molasses or mixed 1:1

with wheat bran as a feedstuff for calves (MINAG, 1975).

Finally, in a review of the subject, Green, Wiseman and Cole (1983) defended the use of

organic acids, mainly arguing that preservation could be achieved at a higher pH and

therefore the silage would not require neutralization prior to use. It was emphasized that

the wastes should be chopped into pieces of 4 mm in size prior to treatment with an 85

percent solution of formic acid or a 1:1 mixture of formic and propionic acid, included at

3.5 percent (Wiseman, Green and Cole, 1982, and Rattagool, Surachatmrongratane and

Wongchinde, 1980, cited by Green, Wiseman and Cole, 1983).

Fermented silage

The principle of fermented silage is similar to that of acid silage; preservation is the result

of acidity arising from the growth of lactic acid-producing bacteria. By-catch or fish

wastes, preferably chopped or minced, are placed in non-metallic vats and mixed with a

single carbohydrate source, such as cassava, sweet potato or molasses or a mixture of

these, and stored airtight. In order for fermentation to start almost immediately, the

addition of 20 to 30 percent of molasses has been recommended (Domínguez, 1988).

Periodic agitation and temperatures of at least 20°C tend to induce rapid liquefaction of

the raw material (Green, Wiseman and Cole, 1983).

Most of the experiences in the preparation and use of biological fish silage in Latin

America were summarized in the proceedings of the FAO Second Expert Consultation on

Technology of Fish Products (FAO, 1989). Various kinds offish residues and by-catch

have been preserved as silage using several sources of carbohydrates for fermentation by

natural occurrence or inoculated microorganisms. The results of the inclusion offish

silage in the diets of pigs, chickens and beef cattle have demonstrated that it is a valuable

source of protein that can, in most cases, replace fish-meal or other traditional protein

sources.

Some results of feeding fermented silage to pigs are presented in Table 9. The silage was

prepared using a 5 percent lactobacillus culture mixed with 60 percent by-catch, 30

percent ground maize and 5 percent molasses (Tibbetts et al., 1981). Later, Domínguez

(1988) suggested that if the objective was to prepare a complete fish silage ration, using

roots as the principal source of carbohydrates, then the following general formula might

be used (percentage air-dry): roots, 30 to 50 percent; molasses, 10 percent; and fish

wastes, 40 to 60 percent. In Viet Nam, fish silage made from shrimp heads, fresh blood

(abattoir) and molasses in proportions of 5:3:2, respectively, and fermented for a period

of ten days reportedly had a pH of between 4.3 and 4.5 (Table 3) as well as a "pinkish

colour, nice flavour and soft texture" (AHRI, 1993).

Molasses preservation of by-catch and fish wastes

The idea that "whole" fish wastes could be preserved directly in cane molasses was first

proposed during an FAO Expert Consultation in 1986 to promote sugar cane as animal

feed (Pérez, 1988). At that time, it was suggested that the silage could be used as a source

of protein for geese. More recently, trials have shown that, in order to expedite the

ensiling process, the raw material should preferably be chopped or ground prior to mixing

with an equal amount (weight) of molasses (4.5 litres of final molasses weighs 5.5 kg). It

has also been suggested that, although the osmotic pressure of the molasses causes an

initial dehydration of the raw tissue, an acidic fermentation also occurs, which tends to

preserve this material (Domínguez, 1988; IAV, 1994). One recommendation is that, if the

raw material is left whole, it should be completely submerged in molasses. To do this, a

wire net should be stretched over the surface of the mixture so that weights can be placed

on top (Domínguez, 1990; Pérez, 1993). The mixture should be stirred twice daily, over

approximately five to seven days.

In Morocco, a mixture (50:50 w/w) of molasses and drained ground fish wastes, left

uncovered and stirred daily, required a period often days to produce a stable final product

with a pH of 4.5. The fish silage was then formed into blocks in order to have solid

feeding material for sheep, goats, horses and camels. The procedure involved adding a 1

percent supplement of minerals and vitamins and about 20 percent ground straw. The

blocks of approximately 7 to 8 kg were dried in the sun for two to four days. One further

recommendation was to use about 5 percent cement during preparation of the blocks

(IAV, 1994).

3 - Fermentation of shrimp-head silage: variation in pH with timea - Fermentation

de l'ensilage de têtes de crevettes: variation du pH dans le temps - Fermentación de

ensilaje de cabezas de camarón: variación del pH con el tiempo

Week 1 Week 2 Week 3

Shrimp heads and molassesb 4.70 6.80 5.10

Fresh blood and molassesb 6.70 4.00 3.80

Shrimp heads, blood and molasses (5:3:2)c 4.50 4.30 4.40

Source: AHRI, 1993. a Remained low or increased its acidity after 21 days.

b Ratio not reported.

c Percentage air-dry proportion.

Shrimp head-molasses silage in Viet Nam - Ensilage de têtes de crevettes-mélasse au

Viet Nam - Ensilaje de cabezas de camarón y melaza en Viet Nam

Fish silage being made - Préparation de l'ensilage de poisson - Ensilaje de pescado en

fase de elaboración

By-catch fish from shrimp fishing - Captures accessoires de poisson provenant de la

pêche à la crevette - Pesca acompañante del camarón - Photo/foto: M. Ottati

Pigs feeding on diets containing fish silage - Ration pour porcs contenant de l'ensilage

de poisson - Cerdos alimentándose con ensilaje de pescado - Photo/foto: H. Lupin

4 - The bacteriostatic effect of sugar-cane B molasses on Escherichia coli and

Salmonella thyphimurium - Effet bactériostatique de la mélasse B de canne à sucre

sur Escherichia coli et Salmonella thyphimurium - Efecto bacteriostático de la

melaza B de la caña de azúcar sobre Escherichia coli y Salmonella thyphimurium

Temperature Storage (days)

0 3 7

(colony-forming units/g)

E. coli 20°C 1.2 x 106 - -

30°C 1.1 x 106 2.3 x 10

2 -

S. thyphimurium 20°C 3.3 x 106 - -

30°C 3.5 x 106 2.6 x 10

2 -

Source: Martínez (in press).

In addition to final molasses being used to preserve raw fish tissue as protein paste for

formulating livestock rations, both by-catch and fish wastes (chopped or ground)

preserved directly in sugar-cane B molasses in a proportion of 2:1 by weight (air-dry

basis) of molasses to raw material offers an interesting option for preserving fish wastes

as well as for generating a complete liquid ration of between 8 and 10 percent crude

protein in dry matter for fattening pigs. In this regard, Martínez (in press) showed the

bacteriostatic effect of B molasses on Escherichia coli and Salmonella thyphimurium

(Table 4).

Chemical composition

The data in Table 5 refer to the chemical composition of different types of fish silage.

Surprisingly, these data do not support the general hypothesis that silage made from by-

catch is superior to that produced from fish wastes. One reason for this may be the

average size of the individual pieces of raw material. By-catch refers to fish that are

"caught incidentally and cannot be sold for human consumption", while fish wastes refer

to the "remaining heads, skin, bone and viscera obtained from commercial fish

processors" (Green, Wise and Cole, 1983). In addition to fish silage, as such, Meinke

(1974) reported the chemical composition of fresh by-catch obtained from the Gulf of

Mexico as (percentage air-dry): crude protein, 14.4 to 20.8 percent; oil, 1.2 to 14.5

percent; ash, 3.2 to 8.8 percent; and moisture, 67.3 to 81.5 percent.

The amino acid composition offish silage is presented in Table 6. Lysine, threonine and

sulphur containing amino acids are present in high levels, as they are in fish-meal.

Consequently, fish silage would appear to be an excellent protein supplement for non-

conventional livestock feeding systems.

A review of the use of fish silage for pigs shows that the energy and nitrogen in fish

silage are highly digestible (Table 7). In fact, Whittemore and Taylor (1976) reported that

the digestible energy and nitrogen were higher in diets containing fish silage than in those

using fish-meal.

Use for feeding

The following information shows how fish silage can be used for feeding both non-

ruminants and ruminants.

Pigs

The data in Table 8 show the results of using by-catch and fish-waste acid silage

preserved with 60 and 30 ml/kg of sulphuric acid solution, respectively, as substitutes for

the crude protein in fish-meal for growing/finishing pigs fed on a diet based on processed

swill and molasses (Cervantes, 1979). At the highest level of protein substitution (100

percent), 12.3 percent of silage replaced 9.3 percent of fish-meal in terms of total dietary

dry matter. Performance was significantly lower when 100 percent of the fish-meal was

replaced by silage, and this was attributed to the palatability of the ration, which

significantly affected feed intake. More recently, it has been shown that high levels of

final molasses can affect overall pig performance, which perhaps also contributed to the

relatively poor results in this experiment (Figueroa and Ly, 1990). In addition to normal

carcass-quality measurements, various organoleptic evaluations were performed: odour,

taste, juiciness and texture. It appeared that treatment had no effect on these parameters

and it was concluded that fish silage could be used to provide up to 50 percent of the

protein supplied by fish-meal in this type of feeding system.

5 - Chemical composition of different substrates used in fish silage - Composition

chimique de divers substrats utilisés dans l'ensilage de poisson - Composición

química de distintos sustratos utilizados en el ensilaje de pescado

Substrate Origin/type Crude

protein

Oil Ash Source

(percentage dry

matter)

By-catch Thailand 58.1 4.2 30.0 Rattagool, Surachatmrongratane

& Wongchinde (1980)*

United Kingdom 66.5 16.6 11.7 Green, Wiseman & Cole (1983)

Cuba 52.6 10.4 11.9 Cervantes (1979)

69.1 15.3 10.8 Tatterton & Windsor (1974)*

Fish

wastes

Herring 48.3 28.2 12.5 Whittemore & Taylor (1976)*

Whitefish 71.1 2.4 19.9 Tatterton & Windsor (1974)*

Tuna 69.9 12.2 10.5 Disney et al. (1978)*

Cod 68.1 2.1 19.0 Green, Wiseman & Cole (1983)

Various 67.7 14.2 4.2 Alvarez(1972)

Various 38.9 4.4 9.9 Cervantes (1979)

Mixture Cuba/by-catch and

fish wastes

37.0-70.2 6.1-

12.3

4.0-

11.1

Penedo, Cisneros & Rodríguez

(1986)

* Cited by Green, Wiseman & Cole, 1983.

6 - Amino acid composition of fish silage - Teneur en acides aminés de l'ensilage de

poisson - Composición de aminoácidos del ensilaje de pescado

Amino acid Smith & Adamson (1976) Whittemore & Taylor (1976)

(percentage)

Arginine 3.70 5.10

Histidine 1.20 1.70

Isoleucine 1.90 2.80

Leucine 3.70 5.20

Lysine* 4.20 6.20

Methionine* 0.80 1.80

Cystine* 0.30 0.80

Phenyalinine 2.40 3.50

Tyrosine 1.10 1.60

Threonine 2.20 3.0

Tryptophan - -

Valine 2.40 3.30

* Lysine, methionine and cystine: 5.8, 2.7 and 1.0 g/kg, respectively; in leftover liquid

(6% dry matter) portion these same values were reported as 3.3, 1.3 and 0.6. respectively

(Department of Animal Nutrition, University of Rostock, Germany, cited by Penedo,

Cisneros & Rodríguez, 1986).

7 - Nutritive value of fish silage for pigs - Valeur nutritive de l'ensilage de poisson

pour les porcs - Valor nutritivo del ensilaje de pescado para los cerdos

Type Digestible

energy

(MJ/kg DM)

Metabolizable

energy

(MJ/kg DM)

Crude

protein

(% DM)

Nitrogen

digestibility

(% total N)

By-cateha

- mackerel 23.4 22.6 52.1 92

- whiting 17.5 16.5 74.1 84

De-oiled, herring

offalb

17.9 - 67.5 91

Source: aGreen, Wiseman & Cole, 1983;

bWhittemore & Taylor, 1976.

DM = dry matter.

8 - Substitution of protein in fish-meal for acid fish silage in dietsa

based on

processed swill and molasses for growing/finishing pigs - Remplacement des

protéines de la farine de poisson par de l'ensilage acide de poisson dans les rations à

base d'eaux grasses traitées et de mélasse pour les porcs en croissance/finition -

Sustitución de las proteínas de la harina de pescado por ensilaje de pescado ácido en

la alimentación de cerdos en crecimiento y engorde a base de desperdicios y melaza

Substitution of

crude protein of

fish-meal

(%)

Feed

intake

(kg

DM/day)

Average

daily gain

(g)

Dry-matter

feed conversion

By-catch, whole:

preserved with 60 ml/kg

sulphuric acid solutionb

0 2.5 530 4.70

25 2.4 480 5.00

50 2.4 480 5.00

100 1.9 330 5.80

Fish wastes, ground:

preserved with 30 ml/kg

sulphuric acid solutionc

0 2.1 540 4.10

25 2.1 550 4.00

50 2.1 540 4.00

100 1.9 440 4.40

Source: Cervantes, 1979. aBasal diet (% DM): processed swill, 47%; final molasses, 44%; and fish-meal, 9%. The

crude protein in DM of swill and silage was, respectively, 22% and 57%. b30 to 90 kg.

c25 to 80 kg.

DM = dry matter.

9 - Use of fermented or acid silage for growing/finishing pigs - Utilisation d'ensilage

fermenté ou acide pour les porcs en croissance/finition - Uso de ensilaje fermentado

o ácido para cerdos en crecimiento y engorde

Origin Percentage dry

matter

Average

daily gain

(g)

Dry-matter feed

conversion

Source

By-catch

fermented silagea

0 730 3.13 Tibbetts et al.

(1981)

5 730 3.37

6 740 3.51

9 680 3.80

By-catch acid

silageb

0 519 4.05 Machin, Young &

Crean (1982)

5 603 3.74

10 615 3.61

15 615 3.41

a Fermented silage: lactobaccilus culture, 5%; by-catch, 60%; ground maize, 30%; and

molasses, 5%; liveweight 27 to 95 kg. b 25 to 80 kg.

The data in Table 9 are somewhat contradictory. In the first experiment, the use of more

than 6 percent fermented silage affected growth and feed efficiency (Tibbetts et al.,

1981). In the second trial, performance generally improved when increasing amounts of

by-catch acid silage were used in diets based on 60 percent sorghum grain (Machin,

Young and Crean, 1982). These observations tend to support the conclusion drawn by

Green, Wiseman and Cole (1983) with reference to the cause of discrepancy among

researchers. These authors recognized the "diversity with respect to both the type of fish

tissue and the silage method employed" and emphasized that feed-conversion efficiency

of pigs fed fish silage is very likely related to the balance of essential amino acids in the

silage, which is dependent on the type of fish used. They referred to experiments in

which lysine and other essential amino acids were adequate and in which fish silage diets

produced better feed conversions than soybean meal diets.

More recently in Viet Nam, the nutritional value of fermented silage made from shrimp

heads, blood and molasses was compared with that of fish-meal in 17 percent crude-

protein rations for growing pigs. The silage and fish-meal had similar protein contents,

46.2 and 45.8 percent, respectively. The objective was to study the effect of replacing

fish-meal (10 percent dry-matter basis of the diet) with silage (Table 10). The main factor

responsible for the reduction in growth was assumed to be the reduction in feed intake,

possibly caused by the lower palatability of the diet. It was concluded that, on a dry-

matter basis, silage could replace 75 percent of the fish-meal and that other protein-

containing materials, such as small fish, crabs, silkworms and animal offal, might be

similarly processed for use as animal feed. In this regard, the author has used final

molasses to preserve land crabs, livestock offal and earthworms, all destined for feeding

pigs. Finally, the use of fish silage in growing/finishing rations sometimes results in the

pork having an "off flavour. However, this can be easily controlled by reducing or

removing the silage from the ration 20 days prior to slaughter.

Ducks

In Viet Nam, two groups of Kaki Campbell ducklings were first exposed to (partially fed)

crushed shrimp-head silage at ten days of age (Table 3). Subsequently, from 21 to 70

days, either 50 or 75 percent of the protein supplement in the diet was replaced by

shrimp-head silage. Growth performance is presented in Table 11. It was concluded that

the silage material could replace 75 percent of the fish/ soybean meal protein supplement.

Although information is not yet available, the author is currently involved in a duck

project related to freshwater aquaculture in Cuba, where the primary objective is to

improve the quality of the ecosystem using the proven means of duck excreta

(Woynarovich, 1976). The proposed duck feeding system is based on a restricted amount

of 18 percent concentrate ration up to 21 days of age, followed by a low-protein, liquid

fattening diet - a mixture of two parts B molasses to one part ground fish wastes by

weight (air-dry basis).

Ruminants

Beef cattle. In Cuba, acid silage material was promoted as a substitute for fish-meal in

cattle feedlot rations based on restricted amounts of protein supplement and forage and

free-choice molasses-urea (Preston, 1969). The practice was to substitute 1 kg of silage

for 0.25 kg of fish-meal in order to provide 162 g of crude protein. The animals were also

fed free-choice molasses/3 percent urea and fresh forage at the rate of 3 kg/100 kg

liveweight, or had daily access to pasture for four hours. Daily liveweight gains for

animals between 150 and 375 kg under commercial feedlot systems ranged from 0.6 to

0.8 kg (V. Rodríguez, personal communication).

10 - Replacement of fish-meal with shrimp heads, blood and molasses silage in diet*

for pigs - Remplacement de la farine de poisson par de l'ensilage composé de têtes

de crevettes, de sang et de mélasse pour l'alimentation de porcs - Sustitución de la

harina de pescado por ensilaje de cabezas de camarón, sangre y melaza para la dieta

de los cerdos

Fish-meal

(100%)

Fish-meal:silage

(50:50)

Silage

(100%)

(percentage dry matter)

Initial liveweight (kg) 13.9 15.2 14.5

Final liveweight (kg) 72.8 76.0 73.0

DM feed consumption (kg/day) 1.95 1.89 1.74

Average daily gain (g) 491 523 487

DM feed conversion 3.97 3.61 3.57

Source: AHRI, 1993.

*Basal diet (% DM): ground maize, 58%; rice grain, 20%; fried soybeans, 5%; soybean

meal, 5%; fish-meal, 10%; minerals and vitamins, 2%.

DM = dry matter.

11 - Growth performance of Kaki Campbell ducks fed shrimp-head silagea in place

of protein supplementb - Performances de croissance de canards Kaki Campbell

recevant un ensilage de têtes de crevettes en remplacement d'un complément

protéique - Resultados del crecimiento de patos Kaki Campbell alimentados con

ensilaje de cabezas de camarón en sustitución del suplemento de proteínas

Age

(days)

Control

(g)

50% protein supplement replaced

by silage

(g)

75% protein supplement replaced

by silage

(g)

21 314 312 311

35 - 668 738

56 1 206 1 191 1 238

70 1 400 1 410 1 413

Source: AHRI, 1993. 1See Table 3.

2Mixture of fish-meal and soybean meal.

At present, acid fish silage has been replaced by by-catch or fish wastes preserved in final

molasses. During the shrimp season, the trawlers often bring in between 8 and 12 tonnes

of by-catch each day. After removing the larger crustaceans and fish by hand, the smaller

and more homogenous material is simply mixed with molasses. If the average size of the

by-catch is larger than normal, the material is chopped before being mixed with molasses.

In either case, it is usually fed within seven to ten days.

Dairy cattle. In most tropical and subtropical countries, the quality of pastures and forage

tends to deteriorate during the dry winter months. This is reflected by lower levels of

digestibility and available crude protein and generally results in a seasonal milk-yield

reduction. The data in Table 12 show how the addition of 1 kg of fish silage to the daily

diet of milk cows during the winter months, December through February, maintained

milk production at a level comparable to that obtained during the wet season.

Camels. In Morocco, fish silage blocks have been used to feed camels. The basal ration

used per 100 kg of liveweight was 1.5 kg of barley and 0.5 kg of straw. When 0.5 kg of

fish silage blocks was used to substitute an equal amount of barley for camels fed the

basal ration, dry-matter digestibility and growth performance improved by 2 and 17

percent, respectively (IAV, 1994).

Sheep. Fish silage has been used successfully in rations for sheep in Morocco (IAV,

1994) and in Cuba (Penedo, Cisneros and Sosa, 1988). The data in Table 13 show how

growth performance was improved by more than 24 percent when 200 g of molasses fish

silage blocks and 300 g of barley replaced 500 g of commercial ration (dry-matter basis)

in rations for fattening sheep. Carcass evaluations were performed, and fish silage had no

effect on meat flavour or taste. When the same type of silage replaced barley in diets for

ewes prior to weaning, there was an improvement in digestibility and a reduction in feed

conversion.

In Cuba, 70 percent sun-dried filter-pressed mud from the sugar mills has been mixed

with 30 percent fish silage to produce a dry, filter-pressed mud/fish silage protein

supplement (FPM/FSPS) for use in concentrate rations for fattening sheep. The

composition (percentage dry matter) of the concentrate was: FPM/FSPS, 20 percent;

bagasse pith/molasses/urea, 20 percent; sun-dried filter mud, 10 percent; final molasses, 5

percent; raw sugar, 38.45 percent; urea, 3.05 percent; mineral mixture, 2 percent; calcium

sulphate, 1 percent; and salt, 0.5 percent. The feeding system comprised seven hours of

poor pasture a day, free-choice, poor-quality hay and 2 kg of the concentrate. The authors

reported that a total of 30 five-month-old sheep, of an average initial weight of 22.3 kg,

gained 136 g/day during a 62-day trial using this feeding system (Penedo, Cisneros and

Sosa, 1988).

Conclusions

It has been shown that by-catch or fish wastes, whole, chopped or ground, preserved in

molasses or as fermented or acid silage, in the form of a paste or block, can replace more

conventional sources of protein for pigs, ducks, sheep, cows, beef cattle and even camels!

The technology for the preparation offish silage exists. Its commercial application will

depend on extension to producers and on its opportunity cost versus that of other

conventional protein sources, as well as on the existence of other means of processing to

meet environmental regulations.

12 - Use of acid fish silage to maintain milk production in the dry winter season in

the subtropics - Utilisation d'ensilage acide de poisson pour maintenir la production

laitière pendant la saison hivernale sèche en régions subtropicales - Uso de ensilaje

de pescado ácido para mantener la producción de leche en la temporada seca de

invierno en las regiones subtropicales

206 Holsteins 157 Holstein x zebus

(litres/day)

Without fish silage July 1975 11.8 -

August 1975 12.4 -

September 1975 11.3 7.9

With fish silage, 1 kg/day December 1975 11.1 6.1

January 1976 11.2 6.6

February 1976 11.2 6.8

Source: Pérez (unpublished).

13 - Performance of sheep fed fish silage blocks* over 60 days - Performances de

moutons recevant des blocs d'ensilage de poisson pendant 60 jours - Rendimiento de

ovejas alimentadas con bloques de ensilaje de pescado durante 60 días

Control diet

(g)

Sunflower meal

(g)

Fish silage blocks

(g)

Fish silage blocks - - 200

Sunflower meal - 200 -

Commercial ration (15% crude protein) 500 - -

Barley - 300 300

Dry-matter feed intake (g/day) 810 810 810

Average daily gain (g) 78 98 97

Source: IAV (in press).

*In addition to the above, all sheep received daily 300 g (dry matter) of straw and 10 g of

a vitamin/mineral supplement.

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