The assessment of protein quality of carp (Cyprinus carpio) diets

Protein quality of carp diets was assessed by five methods: 1. True digestibility, true NPU, BV (as percentage) and PER were determined for approximately iso-energetic diets containing ca.38% protein from 4 different sources. Fish meal gave values of 94.0, 72.5, 77.0, and 1.21 respectively; egg 93.0, 65.4, 70.3, 1.26; Pruteen 68.4, 63.6, 68.40, 1.36; and Casein 91.0, 56.90, 62.5, 1.33. 2. Blood urea were determined and found to be significantly increased with increasing protein concentration in the diet. 3. Ammonia excretion rate was determined; it increased with a decline in protein quality, being greater on groundnut, rapeseed meal, and sunflower diets than on fishmeal, cottonseed meal, and pruteen. 4. Protein sources were incubated in vitro with digestive fluids of fish. Protein digestibilities for fishmeal diets containing 14 and 27% protein were 90.2 and 93.0% respectively; casein (18 and 36%), 91.5 and 93.2%; soybean (10 and 20%), 84.2 and 85.3% ; sunflower (8 and 16%), 64.2 and 66.1%; and fish meal plus soybean meal (ca. 18.2%) 86.5. 5. Plasma free amino acids were individually determined at 0, 6, 24 and 48 h after force-feeding diets containing 15 and 30% protein from six different sources. Total free AA were highest at 24 h for casein and fishmeal, and at 48 h for egg, soybean, rapeseed and sunflower. The 24 h essential amino acid indices (EAAI) for the six diets at 15% protein were, in the same order, 93.0, 100, 100, 86.4, 62.4, and 97.2. At 30% protein, the 24 h EAAI were 78.5, 84.3, 100, and 83.8 for casein, fishmeal, egg, and rapeseed respectively.

Studies on the interrelationship of temperature, stress and immunity in carp (cyprinus carpio L)

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The environmental control of reproduction in the female dace, Leuciscus leuciscus

An investigation was made into the nature and control of the annual reproductive cycle of the dace, Leuciscus leuciscus. It includes 1) a study of the natural reproductive cycle, 2) the use of Carp Pituitary Extract (CPE) to induce final maturation and ovulation in captive fish, 3) the effect of artificial light treatments on ovarian development and 4) the measurement of serum melatonin levels under different photoperiod regimes. Ovarian development was monitored by endocrinological data, notably serum cycles of 17-oestradiol (E2), testosterone (T), and calcium (as an index of vitellogenin), oocyte diameter, the gonadosomatic index and histological studies of the ovary. Under natural conditions, ovarian development can broadly be divided into 4 stages: 1) oogenesis which occurs immediately after spawning; 2) a primary growth phase (previtellogenic growth) prevalent between spawning and June; 3) a secondary growth phase (yolk vesicle plus vitellogenic growth) occurring between June and December and 4) final maturation and ovulation which occurs in mid-March. During the annual ovarian cycle, the sex steroids E2 and T showed two clear elevations. The first occurred initially in April followed by a rise in serum calcium levels. This subsequently initiated the appearance of yolk granules in the oocytes in June. The second rise occurred in September and levels were maintained until December, after which there was a decline in serum E2 levels. It is proposed that in the dace, high serum E2 levels between September and December were required to maintain vitellogenin production and therefore its uptake into the developing oocytes which occurred during this time, albeit at a slower rate than in the summer months. After December, prior to final maturation, whereas serum E2 and calcium levels declined, serum T levels remained elevated. In captivity, final maturation beyond the germinal vesicle migration stage failed to occur suggesting that the stimuli required for these events were absent. However ovulation could be induced by a single injection of CPE, which induced ovulation between 6 and 14 hours after treatment. Endocrine events associated with the artificial induction of spawning included a rise in serum levels of E2, T and the maturation inducing steroid 1720-dihydroxy progesterone. Photoperiodic manipulation demonstrated that whereas short or increasing daylengths were stimulatory to ovarian development, long days delayed development. Changes from long to short and constant short daylengths early in the reproductive cycle advanced maturation (up to 5 months), suggesting that the stimulus for ovarian development and maturation was a short day. However, experiments conducted later in the reproductive cycle demonstrated that only a simulated ambient photoperiod could induce final maturation. It is proposed therefore that under natural conditions the environmental stimulus for ovarian development and final maturation are short and increasing daylengths respectively. Further support that photoperiod is the dominant timing cue in this species was provided by the pattern of serum melatonin levels. Under different photoperiod treatments, serum melatonin, which is believed to be the chemical transducer of photoperiodic information (similar to other photoperiodic species) was elevated for the duration of the dark phase, indicating that the dace at least has the ability to `measure' changes in daylength.