In vitro modelling of the influence of alternative feeds (Hermetia illucens, Arthrospira platensis) on the resistance of different rainbow trout populations (Oncorhynchus mykiss) against the viral haemorrhagic septicaemia virus and Yersinia ruckeri.

Replacing fishmeal, a finite resource with high market demand, in the diet of carnivorous rainbow trout with proteins from alternative sources may be a challenge for these fish. Therefore, this study investigated whether replacing fishmeal with protein derived from Hermetia illucens or Arthrospira platensis could promote disease susceptibility in local trout populations with different growth performance. This was assessed in vitro by measuring susceptibility to infection with the viral haemorrhagic septicaemia virus (VHSV) or the bacterium Yersinia ruckeri. Analysis of fin tissue explants and primary cell cultures from scales from the three trout populations infected in vitro with VHSV and gill explants infected with Y. ruckeri showed no significant differences in virus replication or bacterial counts. Evaluation of the virucidal or bactericidal effect of skin mucus showed a significant reduction in viral load and bacterial count for all samples with mucus addition, but no significant difference was observed between the experimental groups. This study documents no apparent impairment of innate immune mechanisms in the skin and gills of trout after feeding a diet replacing fishmeal with Arthrospira or Hermetia proteins. This underlines the potential of these alternative protein sources for the further development of sustainable trout aquaculture.

Egg yolk colour in organic production as affected by feeding - Consequences for farmers and consumers.

In organic table egg production, saponified extracts of carotenoids are not allowed to intensify egg yolk colour. Therefore, we investigated the suitability of organically produced marigold flower meal (Tagetes erectus, TE) and spinach (Spinacia oleracea, SO) as carotenoid sources (mixture of 25% TE and 75% SO) to reach values of 9-10 'Roche Yolk Colour Fan' units (RYCF units). Feeding a completely unsupplemented control diet resulted in a yolk colour of 4.7 RYCF units, a total supply of 11.1 g/kg, 14.6 g/kg and 17.5 g/kg of TE and SO as stand-alone carotenoid sources induced a significant increase to 8.0, 8.2 and 8.9 RYCF units. Under 'winter-feeding conditions', i.e. minimal carotenoid supply in the diet, 17.5 g/kg TE and SO resulted in 9.3 ± 0.7 RYCF units. It can be concluded that supplementing TE and SO is suitable to improve the yolk colour in organically produced table eggs.

Optimal in-feed amino acid ratio for laying hens based on deletion method.

A total of 56 Hy-line W-36 hens from 28 to 30 weeks were used on nitrogen balance (NB) trial to estimate daily N maintenance requirements (NMR) and the genetic potential for daily N retention (NRmax T). The treatments consisted of six graded levels of nitrogen in the diets (N1 = 8; N2 = 16; N3 = 24; N4 = 32; N5 = 40; and N6 = 48 g N/kg of feed), formulated using the dilution technique. The regression analyses between nitrogen intake and excretion were performed to fit the exponential function and to determine the NMR = 292 mg/BWkg 0.67 , which was applied for further calculation of NRmax T = 1,883 mg/BWkg 0.67 . A second NB trial was conducted, and a total of 96 Hy-line W-36 hens were used in the same period to estimate the ideal amino acid ratio (IAAR). Twelve treatments with eight replicates and one bird per cage were used. A balanced diet (BD) was formulated to meet the IAAR and the requirement of other nutrients for pullets. The limiting diets were formulated diluting BD with cornstarch and refilled with synthetic AAs and other feed ingredients, except for the AA under study. In each trial, the data of nitrogen intake, excretion, deposition and retention were obtained in a NB trial. The IAAR determined by Goettingen approach was Lys 100, Met+Cys 88, Trp 21, Thr 69, Arg 109, Val 90, Ile 75, Leu 127, Phe+Tir 110, Gly+Ser 73 and His 29%. The IAAR determined by Louvain approach was Lys 100, Met+Cys 88, Trp 21, Thr 69, Arg 104, Val 91, Ile 78, Leu 121, Phe+Tir 119, Gly+Ser 77 and His 29%.

Evaluation of dried distillers' grains with solubles (DDGS) as a protein source for broilers.

Male broiler chicks (n=120) were fed diets containing 0, 5, 10 or 15% dried distillers' grains with solubles (DDGS) from the 12th day up to the end of fattening (day 35). During this period feed intake, weight gain and excreta quality (pH, DM) were tested. A digestibility trial was carried out on four birds from each group on the last five days of the experiment to determine the digestibility of organic matter and CP of the different diets. The protein digestibility was evaluated using three different methods; uric acid correction, alpha-amino-N and amino acid-N. There were no significant effects of increased DDGS levels on feed intake, weight gain, excreta quality or digestibility of CP and organic matter. However, feed conversion showed a tendency to decline at the highest DDGS level (15%). Digestibility of DDGS protein was estimated to be 77%. There was no significant difference between uric acid and alpha-amino-N method, but both methods had a significantly lower CP digestibility than amino acid-N. The present results indicate that DDGS can be used as a protein source in diets for fattening broilers up to 10-15%.