Effect of Spanish sweet yacca residue pellet as a replacement for corn on growth performance, nutrient digestibility and haematological profiles in growing pigs

One of the potential alternative feedstuffs is Spanish sweet yacca (SSY, commonly named cassava, Manihot esculenta), an economic energy source in the animal feed industry. However, all SSY organs except seeds contain cyanogenicglucoside (i.e. linamarin and lotaustralin). Spanish sweet yacca should thus be processed in order to reduce cyanogenic potential and phytate content and to preserve their nutritive quality (Salami and Odunsi 2003). The aim of this study was to determine the viability of processed a SSY (i.e. residue pellet) as an alternative to corn. The hypothesis tested in this experiment was that SSY residue pellet replacing corn in growing pigs diet would not cause marked changes in the growth performance.

A total of 84 [(Yorkshire × Duroc) × Landrace] growing pigs (BW of 25.1 ± 2.01 kg, 42-day trial) were allotted to three dietary treatments: CON, Corn-SBM diet; SSY20, replacing corn with 20% SSY; SSY40, replacing corn with 40% SSY. Diets were isonitrogenous and isoenergetic with 178 g/kg crude protein and 13.81 MJ/kg digestible energy, respectively. The experiment consisted of seven replications per treatment and four pigs (two gilts and two borrows) per pen. For the 6-week growth assay, the individual pig weights and feed intake were recorded at d 21 and 42 for the determination of average daily gain (ADG), average daily feed intake (ADFI) and gain : feed (G : F) ratio. The red blood cells (RBC), white blood cells (WBC) and lymphocyte counts of whole blood samples were determined using an automatic blood analyser (ADVIA 120, Bayer, Tarrytown, NY, USA) on d 0, 2, 4, 6 and 42. All pigs were fed diets mixed with 0.2% chromium oxide to calculate the coefficient of total tract apparent digestibility (CTTAD) of DM, nitrogen (N), and gross energy (GE). All data were statistically analysed using the MIXED procedure (SAS^®; USA) as a randomised complete block design. Orthogonal polynomial contrasts were used to assess the linear and quadratic effects of increasing dietary concentrations of supplemental SSY.

No significant differences were observed on growth performance among treatments in the whole experiment, while WBC concentration linearly decreased (P = 0.028, Table 1) on d 4. No significant differences were observed on CTTAD (DM, N and GE) among treatments in the whole experiment. Processed yacca meal could be included in the diets of growing pigs up to level of 30% to reduce feed costs without any detrimental effect on performance (Irekhore et al. 2006), or up to 60% (total replacement of maize) when maize cost is high (Bawa and Damisa 2007). Enyenihi et al. (2009) reported that a diet with yacca led to lower WBC concentrations in laying hens. The observed WBC counts in this study falls within the normal range and therefore it can be concluded that SSY can be used at a level of around 40%, replacing corn in growing pigs diet, without negative effecting growth performance.

Table 1.  Effects of feeding different SSY levels on growth performance in growing pigs