A serological survey of Brucella spp., Salmonella spp., Toxoplasma gondii and Trichinella spp. in Iberian fattening pigs reared in free-range systems.

Zoonotic agents such as Brucella spp., Salmonella spp., Toxoplasma gondii and Trichinella spp., all considered high-risk zoonotic pathogens by the European Food Safety Agency (EFSA), may cause no symptoms of infection in free-range pigs yet still have a significant public health impact. A serological survey was therefore performed to determine the history of occurrence of these pathogens in such pigs in southern Spain. A total of 709 serum samples were collected at abattoir from pigs from 79 farms and analysed for specific antibodies against the above pathogens using commercially available ELISA kits. Encysted Trichinella spp. larvae were also sought following the artificial digestion method of diaphragm pillar muscle. The results showed Salmonella spp. to be widely distributed among the sampled herds [73.42%, 95% confidence interval (CI95 ) 65.6-81.78] and Toxoplasma gondii to be present in over half (58.23%, CI95 47.33-69.07). The seroprevalence of Brucella spp. was very low (3.8%, CI95 0.18-7.42), and antibodies against Trichinella spp. were not detected. No encysted Trichinella spp. larvae were microscopically detected.

Growth of body components and carcass composition of Iberian pigs of 10 to 150 kg body weight as affected by the level of feeding and dietary protein concentration.

A total of 211 growing-finishing Iberian (IB) pigs from 4 separate and independent sets of trials were slaughtered at several stages of growth from 10 to 150 kg BW to determine growth and development of chemical and physical components of the cold eviscerated carcass (CC; without head, feet, and tail). Within each set of trials, a factorial arrangement of treatments, involving several concentrations of ideal protein in the diets as 1 factor and 2 or 3 levels of feed intake as the other, was used. The main objective of the present study was to provide information on the relative growth of physical and chemical components of the CC of IB pigs, which differed because of the dietary treatment imposed, involving a wide range of protein-to-energy ratios and feeding levels. Allometric relationships (P < 0.001) were established between the weight of a chemical component in the CC and empty BW or CC weight. Irrespective of the adequacy of the dietary protein-to-energy ratio, the growth coefficient for CC weight relative to empty BW was >1 (P < 0.001), whereas those for protein, water, and ash relative to empty BW or CC weight were <1 (P < 0.001). In contrast, relative growth coefficients >1 (P < 0.001) were obtained for fat mass and total energy, reflecting the increase in fat relative content that occurs with increasing weight. Multiple-regression equations (P < 0.001) were developed using a stepwise procedure, which estimates the chemical (g/kg) or energy (MJ/kg) composition of CC as a function of empty BW, dietary protein-to-energy ratio, and feeding level, expressed as a multiple of the ME required for maintenance. It is concluded that even if the pattern of developmental growth for the IB pig may show some similarities (increased fat content or decreased proportional weight of some primal cuts with BW or age) with that observed for pigs of different genetic background, relevant differences were detected. They are related to a much smaller relative size of the IB pig lean tissues and cuts, their slower rates of growth, and the increased total body fat, with marked changes in its distribution among depots. Consequently, relationships obtained for lean or conventional genotypes are not applicable to the IB pig.

Response analysis of the Iberian pig growing from birth to 150 kg body weight to changes in protein and energy supply.

A total of 251 growing-finishing Iberian (IB) pigs, 32 of which were suckling piglets, were used in 5 separate sets of trials. The comparative slaughter procedure was used to determine nutrient and energy retention at several stages of growth from birth to 150 kg BW. A factorial arrangement was used within each set of trials, involving several concentrations of ideal protein in the diets as 1 factor and 2 or 3 levels of feed intake as the other. The main objective of these studies was to derive the optimal protein-to-energy ratio in the diet to allow for the expression of maximum protein deposition rates. The effect of feed restriction on growth performance, protein deposition, and fat deposition was also assessed. According to allometric equations, empty BW (EBW) was related to whole body components or total chemical constituents of empty body mass (P < 0.001). For pigs receiving solid feed, highly statistically significant multiple regression equations were constructed, which derived nutrient (g/kg) or energy (MJ/kg) composition as a function of EBW, dietary protein-to-energy ratio, and level of feeding (P < 0.001). In pigs offered adequate protein-to-energy diets, ADG at each stage of production was predicted as a function of the average BW and feeding level (P < 0.001). It was observed that the estimates of ME required for maintenance and net efficiency of utilization of ME for growth change were within rather narrow ranges throughout the growth stages studied. Preferred values (413 kJ/kg BW(0.75) × d(-1) and 0.593 for ME(m) and k(g), respectively) were obtained by regressing total energy retention (kJ/kg BW(0.75) × d(-1)) against ME intake (kJ/kg BW(0.75) × d(-1)). A multiple-regression approach revealed that in the IB pig, ME costs for protein deposition and fat deposition reach 60 and 62 kJ/g, which is considerably greater than in conventional or lean pig genotypes. In the IB pig, the maximum daily rate of protein deposition (PD(max), g) seemed to follow a linear-plateau shape with a breaking point at 32.5 kg BW, beyond which PD(max) remained at an average rate of 75 g × d(-1). The marginal efficiency of body protein deposition was estimated at each growth stage. In pigs fed on optimal or suboptimal protein-to-energy diets, the relationship between PD and ME intake declined, following a curvilinear pattern with increasing BW; thus, implying relative increases in lipid gain as BW increased.

Effects of herbage ingestion upon ileal digestibility of amino acids in heavy Iberian pigs fed on an acorn-based diet.

We conducted two experiments with heavy Iberian pigs to determine the ileal digestibility of amino acids (AA) in acorns and freshly cut herbage, and the effects of adding fresh herbage upon the supply of ileal digestible AA when pigs were fed on holm-oak acorns. In Experiment 1, carried out in cannulated pigs of 107 kg bodyweight (BW), daily intake of acorns reached 44.9 g DM/kg(0.75) BW. Arg, His and Thr showed the lowest apparent ileal digestibility (AID) values, whereas Met, the branched-chain AA and Phe had the highest coefficients. The AID of total EAA was 0.716 but only 0.222 for NEAA. Most of the digestive and absorptive processes of acorn protein occurred before the hindgut. Acorn provides (per kg DM) 2.27 g apparent ileal digestible Lys and 22.7 g apparent total digestible AA. Standardized ileal digestibility (SID) values for EAA, NEAA and total AA were 0.924 ± 0.020, 0.784 ± 0.041 and 0.860 ± 0.029. In Experiment 2 fresh herbage was given to six cannulated Iberian pigs of 140 kg either as a single feed (13.7 g DM/kg(0.75) BW) or as a supplement to acorns (28.4 g DM/kg(0.75) BW). When only freshly cut forage was offered the AID of the EAA, NEAA and total AA was close to 0.65 and supplied (per kg DM ingested) 5.61 g AID Lys and 91.7 g digestible AA. Standardized ileal values were 0.744 ± 0.023, 0.912 ± 0.038 and 0.831 ± 0.030 respectively. The addition of fresh forage to the acorns led to a significant decrease in AID of AA in acorn due to digesta transfer to the hindgut: His (p < 0.01), Met (p < 0.001), Phe (p = 0.092), Thr (p < 0.05) and Val (p < 0.05), but Arg, Lys and the branched-chain AA remained unaffected. The main contribution of herbage to AA nutrition of the grazing Iberian pig relies mainly on increasing the supply of digestible AA for pig tissues.