No abstract

The apparent and true amino acid availability values for corn, wheat middlings, rice bran, rice mill feed, soybean meal, peanut meal, cottonseed meal, meat and bone meal, and two different samples of menhaden fish meal were determined in adult channel catfish. Although there was reasonable agreement between protein digestibility values and average amino acid availability values, individual amino acid availabilities were variable within and among the various feed ingredients tested. Therefore, we recommended that amino acid availability values should be used for more accurate catfish feed formulation. In addition, it appears that the use of true amino acid availability values should be used for feed ingredients of relatively low protein content.

Apparent digestible protein and energy coefficients for corn, cottonseed meal, menhaden fish meal, meat and bone meal, peanut meal, rice bran, rice mill feed, soybean meal and wheat were determined in test diets processed in pelleted and extruded forms in adult channel catfish (Ictalurus punctatus). Test diets were fed ad libitum to fish and fecal samples were collected by the dissection technique. The digestibility value of each ingredient was determined by comparison of the digestibilities of a reference diet and a test diet containing a 70:30 mixture of the reference diet and the test ingredient. In general, the digestibility values determined by this method are higher than previously reported values based on single-source diets which were Cottonseed meal 5-01-621 4320 65-+4(3) 80-+5(3) Fish, menhaden meal 5-02-009 4416 95-+3(3) 92-+6(2) Meat and bone meal 5-00-388 3850 70-+2(3) 76-+7(3) Peanut meal 5-03-650 4431 68-+3(3) 76-+6(2) Rice bran 4-03-928 4232 53-+5(3) 50-+4(3) Rice mill feed ----38-+3(3) c 14-+4(3) Soybean meal 5-04-612 4185 73-+ 1(3) 72 -+3(3) Wheat, grain 4-05-268 3803 49-+6(3) 63-+5(3) aExpressed as kcal/kg on an as-fed basis (NRC 1977).

Two experiments were conducted to reevaluate the dietary phosphorus requirement of fingerling channel catfish. Basal diets containing either casein with supplemental inorganic phosphorus and 0.5% total calcium or egg albumin with supplemental inorganic phosphorus and 0.75% total calcium yielded similar requirement data. Eleven-week growth, feed efficiency, serum phosphorus, bone ash, bone calcium and bon phosphorus data indicate that 0.33% apparent available dietary phosphorus is adequate for maximum growth and bone mineralization. Based on these data and previous findings, we would suggest a value of 0.4% apparent available phosphorus be used in formulating catfish feeds. The apparent availability of phosphorus from soybean meal, as determined by the chromic oxide indicator method, was 29% for channel catfish.

Purified diets containing equivalent amounts of glucose, maltose, fructose, sucrose, corn starch and dextrin were fed to fingerling channel catfish (Icatalurus punctatus) to compare the growth responses to these various carbohydrates. The best growth response was achieved with dextrin and the next best with corn starch. Fish grew at the same rate when glucose, maltose or sucrose was the only dietary carbohydrate source. Dietary fructose resulted in the lowest growth rate. Feed efficiency and percent retained energy values followed the same pattern as growth rates. These data suggest that the catfish is apparently unable to utilize dietary mono- and disaccharides as energy sources. Oral carbohydrate tolerance tests using glucose, maltose, fructose, sucrose and dextrin were conducted with larger channel catfish. Oral glucose and maltose resulted in a persistent hyperglycemia indicative of a diabetic-like status. Fructose appeared to be poorly absorbed from the intestinal tract and did not appear to be converted to glucose. Oral administration of sucrose was followed by a gradual increase in plasma glucose, with no detectable fructose being absorbed until the 6-h period. Oral dextrin resulted in less than a two-fold increase in plasma glucose, which remained constant from 2 to 4 h after administration and then declined. These observations are consistent with the hypothesis that certain fishes, including the channel catfish, resemble diabetic animals by having insufficient insulin for maximum carbohydrate utilization.