Effect of replacing barley by increasing levels of olive cake in the diet of finishing pigs: Growth performances, digestibility, carcass, meat and fat quality

The effect of the solid by-product from the olive oil industry (olive cake) on digestibility, growth performances, and carcass, meat and fat characteristics was studied in sixty Duroc×(Landrace×Large White) gilts, of 69.5 ± 5.02 kg of body weight and 126 ± 3 days of age. Increasing levels of olive cake (0, 50, 100 and 150 g/kg of feed) were included in the diet by replacing the same proportion of barley. Five pens with three pigs per treatment were assayed, considering the pen as replicate. The trial lasted 35 days, and animals were slaughtered with 96.7 ± 7.45 kg of body weight. Daily feed intake increased (P=0.04) and daily gain tended to increase (P=0.06), both quadratically, with olive cake inclusion reaching the maximum values at 100 g olive cake/kg. The daily apparent digestible energy intake also increased quadratically (P=0.04) on increasing dietary olive cake content. The feed conversion ratio was not affected by diet. Also, the apparent organic matter digestibility tended to decrease quadratically (P=0.06) and energy digestibility decreased linearly (P<0.04) as the level of dietary olive cake level increased. The experimental treatment had scarce effects on carcass and meat characteristics; however, the inclusion of olive cake increased quadratically (P=0.04) carcass weight and decreased linearly (P=0.02) fat depth measured at Gluteus medius muscle. The experimental treatment did not modify the total polyunsaturated fatty acids proportion of subcutaneous fat but increasing levels of olive cake promoted a linear reduction (P=0.01) of total saturated fatty acid proportion and a linear increase (P=0.02) of total monounsaturated fatty acid percentage, especially that of C18:1 (P=0.01). We can conclude that olive cake might be included up to 100 g/kg in finishing pig diets improving some aspects of growth performances and carcass quality and also providing a healthier fatty acid profile in fat tissues.