Cowpea (Vigna unguiculata [L.] Walp.) Seeds as an Alternative Protein Source in Finishing Pig Diets: Effects on Growth Performance, Blood Biochemistry, Meat Quality, and Muscle Fatty Acid Profile

This experimental trial assessed raw cowpea seed (CPS; Vigna unguiculata [L.] Walp.) inclusion effects in finishing pigs’ diet on growth performance, blood chemistry, meat quality, and fatty acid profile (FAs). A number of 54 crossbred male pigs ([♀F1 Topigs Large White × Norsvin Landrace] × ♂ Duroc) with an initial average body weight of 60.3 ± 3.20 kg (mean ± SD calculated across individual pigs) were divided into three groups of 18 pigs each comprising six pens of three pigs per treatment. The control group (CON) was fed a standardized SBM-based complete feed. In the experimental groups, the SBM was replaced with increasing levels of cowpea seeds (100 and 200 g/kg: CPS10 and CPS20 groups). Iso-nitrogenous and iso-caloric diets were designed with comparable levels of total lysine, sulphury amino acids (methionine + cysteine), calcium, and phosphorus. At the end of the experiment (49-day finishing period), all pigs were slaughtered. To evaluate physicochemical traits and the fatty acid profile, samples of the Longissimus dorsi (LD) muscle were collected. Incorporating CPS into pig diets produced no significant effects on growth performance (final BW, ADG, ADFI, FCR) or carcass characteristics. Overall, CPS inclusion did not affect blood biochemical indices or most meat quality parameters; however, a 20% CPS level decreased fat content, and both CPS treatments reduced the pH at 24 h post mortem, without affecting meat color or drip loss. Chewiness and resilience were lower in CPS10 group compared to CON group. Finally, the inclusion of CPS into the pigs’ diet ensured (p = 0.032) higher relative proportions of n-3 PUFAs within total muscle FAMEs, in the LD muscle, including, in particular, α-linolenic acid (p = 0.043), docosapentaenoic acid (p = 0.047), and docosahexaenoic acid (p = 0.044), which allowed for an increase in the hypo-/hypercholesterolemia ratio (p = 0.044) and a reduction in the n-6/n-3 PUFAs ratio (p = 0.037) compared with the CON group. In conclusion, raw Aura 26 cowpea seeds could partially replace soybean meal in fattening pig diets without adversely affecting productive performance while favorably altering the relative fatty acid composition of LD muscle lipids.