Feeding and Rearing Strategies for Heavy Pigs: Effects on Growth Performance, Feed Efficiency, and Dry-Cured Ham Meat Quality Traits

In Italy, pigs must be slaughtered at 160 ± 16 kg body weight (BW) at 9 months of age for dry-cured ham production (control, C). In Chapter 1, we investigated three alternatives based on different feeding conditions to address the implications of changing the age and weight at slaughter of heavy pigs on carcass and green ham quality traits: 1) allowing pigs to express their growth potential by allowing them to achieve 160 ± 16 kg slaughter weight (SW) at younger slaughter age (SA) (younger Age, YA); 2) allowing pigs to express their growth potential by maximizing their SW at 9 months SA (greater weight, GW); 3) increasing the SA required to achieve 160 ± 16 kg SW (older age, OA). Pigs (336 C21 Goland, 95 kg initial body weight) were slaughtered at 257, 230, 257, and 273 d SA and 172.7, 172.3, 192.9, and 169.3 SW kg for the four treatments, respectively. C pigs had an average daily gain (ADG) of 715 g/d and feed efficiency (FE) of 0.265 (gain to feed). Compared to C, YA pigs had higher ADG (+32%), FE (+7.5%), and better ham adiposity; GW pigs had higher carcass weight (+12%), ADG (+25%), trimmed ham weight (+10.9%), and better ham adiposity. OA treatment affected ADG (−16.4%), FE (−16.6%), and trimmed ham weight (−3.6%). YA and GW could be promising alternatives to C as they improved FE and ham quality traits. In Chapter 2, a total of 159 C21 Goland pigs (gilts and barrows) at 95 ± 9.0 kg BW from three batches were used to investigate the impact of ad libitum feeding on SW, growth performance, feed efficiency, and carcass and green ham characteristics. Diets contained 10 MJ/kg of net energy and 7.4 and 6.0 g/kg of SID-lysine. Slaughter weight classes (SWC) included <165, 165–180, 180–110 and >210 kg BW. In each batch, pigs were sacrificed at 230 or 258 d of age. Left hams were scored for round shape, fat cover thickness, marbling, lean colour, bicolour and veining. Data were analyzed with a model considering SWC, sex and SWC X Sex interactions as fixed factors and the batch as a random factor. The linear, quadratic and cubic effects of SWC were tested, but only linear effects were found. Results showed that pigs with greater SWC had greater average daily gain and feed consumption, with similar feed efficiency and better ham quality traits: greater ham weight, muscularity, and fat covering in correspondence of semimembranosus muscle. Barrows were heavier and produced hams with slightly better characteristics than gilts. The current National Research Council (NRC) nutrient recommendations are based on pigs fed ad libitum up to 140 kg BW. It is unclear whether this applies to pigs weighing more than 140 kg in BW raised under different conditions. This was addressed in Chapter 3 using a mathematical modelling approach based on repeated BW and backfat (BF) measurements to estimate: i, Protein (Pd) and lipid (Ld) depositions; ii) Metabolizable energy (ME); iii) Standardized ileal digestible lysine (SID lysine) requirement, and partitioning the body protein and lipid accretions of 90 and 200 kg BW using 224 Goland C21 heavy pigs when exposed to different rearing conditions. The control pigs (C) received diets limiting ME up to 170 kg in slaughter weight (SW) at 9 months of age (SA); older (OA) pigs had restricted diets limiting ME and SID lysine up to 170 kg in SW at >9 months SA; younger (YA) pigs were fed nonlimited amounts of ME and SID lysine up to 170 kg in SW at <9 months SA; and greater weight (GW) pigs were fed as the YA group, with 9 months SA at >170 kg in SW. We confirmed that the estimated MEm averaged 1.03 MJ/kg0.60. An 11% increase in MEm was observed in OA pigs compared to the controls. Energy restriction had negligible effects on the estimated MEm. The marginal efficiency of SID lysine utilization for Pd averaged 0.725, corresponding to a 9.8 g/100 g Pd SID lysine requirement.