44 JUNE 2015 • WORLD AQUACULTURE • WWW.WAS.ORG of SDP, proteins are subject to less heat damage and denaturing compared to traditional rendering processes (Luzier et al. 1995). SDP has an excellent amino acid profile and nearly 99 percent digestibility (Bureau et al. 1999). SDP proteins are commonly used in diets for pigs, calves, and poultry, mainly for improved production parameters during stressful events. When included in pig diets, SDP results in an improvement of feed intake, animal growth and feed efficiency (Torrallardona et al. 2010). More than 25 percent improvement of growth rate during the first two weeks post-weaning has been documented in pigs fed diets containing SDP (Van Dijk et al. 2001; Torrallardona 2010). SDP has also been recommended in animal diets as a source of immunological support due to their immune modulatory components, including immunoglobulins, bioactive peptides and growth factors (Perez-Bosque et al. 2006, Campbell et al. 2010, Gao et al. 2011). This effect can be partially attributed to the high digestibility of SDP but also to its known effects on improvement of the immune status of pigs when under stressful conditions, such as weaning stress or other environmental and production stressors. Similar results have been documented for calves and poultry that were provided diets containing SDP, particularly when experiencing stressful events. Although the benefits of including SDP in diets for land animals are well known, there is limited literature on the effects of dietary SDP inclusion in aquatic feeds (Johnson and Summerfelt 2000). The objective of this article is to review studies conducted using SDP in aquatic animal diets and the benefits that the aquaculture industry can expect from the use of this functional protein ingredient in aquafeeds. The studies reviewed are those describing the effect of nutrition provided by SDP in aquatic animal diets on performance parameters and immune measurements. Improved Size Distribution of Salmon with SDP A study was designed to evaluate the inclusion of SDP derived from porcine blood (AP820P, APC Europe, SA) as a feed ingredient in commercial feeds for Atlantic salmon Salmo salar parr and its effect on growth performance, feed utilization, organization and functionality of the digestive system and hematological parameters (Gisbert et al. 2013). SDP was incorporated into diets at increasing levels (0, 3, 6 and 9 percent). It was dispersed in olive oil and then sprayed on commercial salmon feed. The diets were isolipidic (31 percent), although they did not have similar levels of dietary protein (ranging from 43.3 percent CP in the 0 percent SDP diet to 50.1 percent CP in the 9 percent SDP diet). This variation in protein content of diets did not confound results of this study because the dietary protein levels tested were greater than those generally recommended for this species at this developmental stage (Bendiksen et al. 2003). Salmon parr (45 g initial weight) were fed for 86 days at 13.0 C. Each 450-L tank was stocked with 100 fish and equipped with an automatic feeder to feed fish continuously for 2 min during four feeding periods per day at a feed ration of 0.9 percent of biomass. At day 87, fish were transferred to seawater (35 g/L salinity) and water temperature was increased to 16 C for 15 d to evaluate their smoltification capacity. At the end of the trial, the mean weight of salmon fed different diets was similar (92.8-98.5 g), regardless of the SDP level incorporated in the feed. However, the size distribution of individual body weight was significantly affected by diet. Size heterogeneity is a common feature in salmonid farming that affects the overall performance of the rearing process. Due to the hierarchy that is established in the salmon population, there is a group of dominant fish that does not allow smaller (subordinate) fish to feed normally. Therefore, under conditions promoting hierarchy formation, the largest fish at the beginning are expected to get the largest share of feed, grow the fastest and have the greatest weight at the end of the production cycle, and therefore establish a wide size distribution between fish. Under experimental conditions, salmon fed the 6 percent SDP diet had the most homogeneous distribution in body weight among the tested diets. Thus, fish fed the 6 percent SDP diet had a greater proportion of fish within the mode of the population (81-120 g) and a lower proportion of fish belonging to smaller (40-80 g) or larger (121-170 g) size classes in comparison to the control group (Fig. 1). The same trend was observed when data were expressed in standard length or using the Fulton’s condition factor. The FIGURE 2. Dry matter and protein digestibility (A) and survival (B) in rainbow trout fed for 84 days with different levels of SDP (0, 3 and 6 percent) added before extrusion (IN) or coated on pellets after extrusion (OUT).
RkJQdWJsaXNoZXIy MjExNDY=