Management and nutritional strategies to improve growth performance and carcass merit in white pigs

Resumen

The main objective of this PhD Thesis was to study the influence of the body weight (BW) and uniformity at weaning, and the net energy (NE) content of the diet, gender, and sire line on growth performance during the fattening phase and carcass and meat quality in heavy pigs. Three experiments (Exp.) were conducted. In Exp. 1, the influence of pen uniformity at weaning [7.5 ± 0.6 kg vs. 7.5 ± 1.2 kg (BW ± standard deviation; SD)] and sex [castrated male (CM) vs. castrated female (CF)] on growth performance during the nursery (7.5 to 27.3 kg BW) and the fattening (27.1 to 130.5 kg BW) phases, and on carcass and meat quality slaughter at 130.5 kg was studied. During the nursery phase, pigs from the more uniform pens were less efficient than pigs from the less uniform pens (P = 0.05). Also, CM had greater feed intake (ADFI; P < 0.05), and average daily gain (ADG; P < 0.001) and were more efficient (P < 0.001) than CF. During the fattening phase, initial pen uniformity did not affect pig performance but CM tended (P = 0.08) to have higher ADFI and worse feed efficiency than CF. Trimmed primal cut yield tended to be higher for pigs of the more uniform groups and for CM than for CF (P = 0.09). It is concluded that regrouping of pigs at weaning, according to uniformity of BW, had no effects on growth performance or carcass quality at slaughter. Castrated females might be an alternative to barrows for the production of carcasses destined to the dry-cured industry. In Exp. 2, 540 crossbred pigs with an initial BW of 28.5 kg were used to investigate the effects of NE content of the diet (2.29, 2.33, 2.37, 2.41, and 2.45 Mcal/kg) on growth performance and carcass and meat quality traits of gilts, boars, and immunocastrated males (IMC). An increase in dietary energy increased NE intake (P < 0.05) and improved feed conversion ratio (FCR) linearly (P < 0.001). The IMC pigs showed greater ADFI and ADG than gilts and boars (P ≤ 0.001). Backfat (BF) depth increased (P < 0.05) and chilled and trimmed ham yield decreased (P < 0.01), as the dietary NE increased. Backfat depth was greater for gilts and IMC than for boars (P < 0.05). Also, gilts had greater carcass and loin yields than boars and IMC (P < 0.001). Diets with the higher NE contents were more appropriate for the production of heavy pigs than diets with lower the NE content. However, the economic interest of this practice needs further assessment, because it will depend on the relative cost among ingredient that vary with the region and year considered. In Exp. 3, the effects of NE content of isoproteic diets on growth performance and carcass and meat quality traits were studied in crossbreds from Landrace x Large White females and two Pietrain sire lines (PIC L62 vs. German Pietrain). Feed intake decreased (P < 0.001) and feed efficiency improved linearly (P < 0.001) as the NE content of the diet increased. Crossbreds from PIC L62 had greater ADFI and ADG (P < 0.001) but were less efficient (P < 0.01) than crossbreds from German Pietrain. German Pietrain crossbreds were leaner (P < 0.001) and had more shoulder yield (P < 0.01) and less fat at Gluteus medius muscle (P < 0.001) than carcasses from PIC L62 crossbreds. In summary, an increase in the NE concentration of the diet improved feed efficiency but did not affect ADG. Crossbreeds from PIC L62 sires grew faster and had fatter carcasses than crossbreds from German Pietrain.