Animal Feed Science and Technology 96 1/2 1 13 Amsterdam, Netherlands: Elsevier Science B.V..

A three-step in vitro procedure was developed by Calsamiglia and Stern [J. Anim. Sci. 73 (1995) 1459] to estimate intestinal protein digestion after 16 h incubation in the rumen. The objective of our work was to modify this procedure to give an accurate estimation of N digestibility without the use of surgically modified animals by replacing the rumen incubation step by an in vitro protease enzyme incubation, and the use of small nylon bags for samples instead of the time-consuming filtration step. The results were compared with those from mobile nylon bag studies or ADIN determinations. In addition, the effect of heat treatment of grains and soyabean on protein digestibility was investigated. Briefly, samples were weighed into small nylon bags, sealed, and a maximum of 30 bags were placed in a 2.4 1 bottle containing borate-phosphate buffer at 39 degrees C. After 1 h, protease solution (protease type xiv, Streptomyces griseus) was added. After 4 h, the bags were removed and rinsed thoroughly. Half of the bags were dried at 50-55 degrees C for 48 h and the dry weight was recorded. The rest of the bags were incubated for 1 h in pepsin solution, then NaOH and pancreatin solutions were added and the bags were incubated for 24 h at 39 degrees C. Bags were rinsed thoroughly and dried at 50-55 degrees C for 48 h. The dry weight of the bags was recorded and the bag residue and the original feeds were analysed for N. Samples were barley, oats, wheat and soybeans, heat-treated for various times, and were obtained from other trials for which mobile bag digestibility values were determined with or without 16 h rumen incubation. Mobile bag digestibility values without rumen incubation ranged from 77 to 97%. Regression analysis of the relationship of N digestibility (mobile bag) and N digestibility (in vitro) for all grain samples resulted in a highly significant relationship (r2=0.95, P<0.0001). When soyabean samples were included in the analysis, the r2 was only 0.02. Residual trypsin inhibitor activity of some of the samples interfered with mobile bag digestibility (no rumen incubation), while there was no interference of trypsin inhibitor with the in vitro digestibility determinations, demonstrating a benefit of the proposed method. There was also no interference for mobile bag digestibility when the samples were first incubated in the rumen for 16 h. This in vitro procedure closely simulated the physiological conditions in the animal allowing a prediction of intestinal N digestibility without the use of surgically modified animals. The method was sensitive to heat damage of the samples and could be used to rapidly evaluate the nutritional value of grain and soyabean feedstuffs for ruminants.

Phytase and sodium diformate supplementation in a plant-based diet improves protein and mineral utilization in rainbow trout (Oncorhynchus mykiss)

A basal isonitrogenous and isoenergetic plant-based diet (Control) was supplemented with either 10 g kg−1 sodium diformate (NaDF), 4000 FTU kg−1 phytase (Phy) or a combination of both additives (NaDF + Phy). Three hundred juvenile rainbow trout with an average weight of 120 g were randomly distributed into 12 fibreglass tanks (300 L). After 65 days of trial, fish fed diets containing phytase, NaDF or the combination of both additives showed a higher growth rate (P < 0.05) compared to fish fed Control diet. NaDF increased feed intake (P = 0.032), while phytase inclusion resulted in a better feed conversion ratio (P < 0.0001) and a higher N retention efficiency (P = 0.02) compared with the Control. Apparent digestibility of P, Ca, Mg and Zn was improved by the use of phytase (P < 0.005) as well as P, Ca and Mg retention efficiency in fish (P < 0.0001). Using 4000 FTU kg−1 phytase in plant-based diets resulted in a 13% and 50% reduction in N and P loadings, respectively. The use of NaDF in combination with phytase in a plant-based diet for rainbow trout resulted in a higher weight gain than that when NaDF was used alone.Fil: Morales, Gabriel Alejandro. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Denstadli, V.. Norwegian University of Life Sciences; NoruegaFil: Collins, S. A.. Norwegian University of Life Sciences; NoruegaFil: Mydland, L. T.. Norwegian University of Life Sciences; NoruegaFil: Moyano, F. J.. Universidad de Almería; EspañaFil: Øverland, M.. Norwegian University of Life Sciences; Norueg

Histology and growth performance in rainbow trout (Oncorhynchus mykiss) in response to increasing dietary concentration of sparteine, a common alkaloid in lupins

This study evaluated the effects of sparteine, a lupin alkaloid, on growth and organ histology in rainbow trout. Eight diets with increasing concentrations of sparteine (0, 50, 100, 250, 500, 1000, 2500 and 5000 mg kg-1) were fed to triplicate groups of 61-g fish for 62 days. Survival was not affected by the dietary treatments. Weight gain, feed conversion efficiency and feed intake decreased in a quadratic manner for sparteine levels above 100 mg kg-1. No effects were observed at inclusion levels =100 mg kg-1. Whole-body lipid and dry matter was depleted in a quadratic manner, while protein and ash were not affected. No tissue alteration attributable to sparteine alkaloid intake was found in liver, kidney, spleen or mid and distal intestines. At sparteine levels above 1000 mg kg-1 of diet, the weight of the intestines and the liver relative to body weight decreased, whereas the weight of the spleen increased. These effects were likely associated with low feed intake and starvation. These results indicate that dietary sparteine alkaloid primarily reduced palatability, but did not impair the health of the fish. The level of sparteine should be kept below 100 mg kg-1 in trout diets to ensure rapid growth