Английский язык: Сборник текстов и упражнений для студентов специальностей "Промышленное рыболовство". Дьякова Н.П. - 60 стр.

Once a diet has been formulated and the ingredients have been mixed together in the
proper proportions, the material is usually made into a pellet. Pellets are made by ex-
posing the material to high pressure in a pellet mill or extruder. Pellet mills may use
steam to help bind the ingredients together. Extruders use supplemental heat and ex-
tended exposure to high pressure to make pellets. Pressure pellet mills and extruders
pass the feed mixture through a small aperture which leads to a product which, is not
cut to short lengths, would be much like spaghetti strands. The diameter of the pellets
varies, but is typically 0.2 to 0.24 inches ( 5 to 6 mm). A knife cuts off the strands as
they exit the pelleting equipment. Feeds produced by pressure pelleting are more
dense than water; thus, they sink. During the extrusion process, on the other hand, the
high heat used causes changes within the ingredients so that starches expand when
the pellets leave the machine and come into contact with air. This rapid expansion of
the material traps air within the pellets, which float when placed in water. Because of
the higher temperatures and other factors, extruded pellets are more expensive than
pressure pellets. Advantages of floating pellets are that the aquaculturist can see that
the fish eat feed. By watching the fish eat, the producer can control the amount of
feed offered and thereby avoid overfeeding. This can save money. If the fish develop
a disease, the aquaculturist may be able to identify the problem by observing changes
in the behavior or appearance of the fish and can treat the problem before it progress
very far. Floating feeds should not be used on all aquaculture species. Shrimp, for ex-
ample, feed on the bottom and will not swim to the surface for pellets. However nu-
trients will be quickly lost from sinking pellets which may dissolve in a few minutes
(floating pellets may take 24 hours or more to disintegrate), so valuable sources of
nutrition can be lost if the animals do not consume the feed quickly. Also, bacterial
and fungal growth on feed particles that are not quickly consumed can lead to disease
or toxicity problems.

                                      Vocabulary

       to rely on                               полагаться на
       nourishment                              питание
       to feed on                               питаться
       food chain                               пищевой симбиоз (совместное
                                                проживание организмов с обоюдной
                                                пользой друг для друга)
      macrophyte                                макрофит
      invertebrate (s)                          беспозвоночные
      to meet requirements                      отвечать требованиям
      crustacean                                ракообразные
      cholesterol                               холестерол
      to determine                              устанавливать, определять
      diet                                      пища
      with respect to                           в отношении, что касается

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