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For dry-cured meat products from pigs, such as ham or shoulder, a minimum of carcass fatness is required and then heavy market body weights (BW) (120–130 kg) as well as castrated males are needed to increase fat carcass content. Therefore, nutritional strategies as the reduction of dietary protein or Lys content during the growing period are being researched in pigs to increase fatness and then to improve quality of dry-cured products. A total of 160 Duroc × (Landrace × Large White) pigs, 50% barrows and 50% gilts, were used in a trial. During the growing period (73–118 d of age), four feeds were formulated with decreasing levels of crude protein (CP; 21.6, 17.7, 14.7 and 13.5%) to achieve 1.10, 0.91, 0.78 and 0.52% of total Lysine, respectively. From 118 d until slaughter, at 123 kg (183, 181, 178 or 192 d of age, respectively), a common diet was provided (17.7% CP and 0.91% Lysine).
CP restriction affected quadratically all production traits, reducing the average daily gain (P < 0.001) and the feed intake (P < 0.05) and increasing the feed conversion ratio (P < 0.01). During the finisher period, when all experimental animals received a common diet, a compensatory increase of BW gain was observed (P < 0.001). The effect was linear and associated to a higher daily feed intake (P = 0.097) giving finally a linear decrease of feed conversion ratio (P < 0.01). For the overall trial (grower + finisher), the daily gains showed a quadratic reduction (P = 0.05) whereas feed conversion ratio increased linearly (P = 0.001), especially for pigs fed diets with 14.7 and 13.5% CP. Also, barrows ate more and grew faster than gilts (P < 0.001) with no difference in feed conversion ratio. Barrows had fatter carcasses than gilts but intramuscular fat (IMF) proportion was similar for both. Dietary CP restriction promoted wider backfat depth and pork with higher IMF percentage which was more monounsaturated and less polyunsaturated.
It is concluded that crude protein restriction during the grower period improves desirable carcass and meat traits in barrows and gilts intended for dry-cured products.
Suárez-Belloch, J., Latorre, M. A., & Guada, J. A. (2016). The effect of protein restriction during the growing period on carcass, meat and fat quality of heavy barrows and gilts. Meat science, 112, 16-23.