Effects of dietary protein content and feeding level on carcass characteristics and organ weights of Iberian pigs growing between 50 and 100 kg live weight

Abstract

The effects of dietary protein content and level of feeding on carcass characteristics and organ weights were studied in castrated male Iberian pigs growing from 50 to 100 kg live weight (LW). Animals were offered four diets providing 145, 120, 95 and 70 g ideal crude protein (CP) per kg dry matter (DM) and 13·94, 14·29, 14·56 and 14·83 MJ metabolizable energy (ME) per kg DM, respectively. Three levels of feeding were assayed: 0·60, 0·80 and 0·95 of ad libitum intake. The pigs were slaughtered at 100 kg LW. Daily gain in carcass (carcass gain, g/day) and protein deposition (PD, g/day) in this component attained 76·2% and 78·8% of whole-body average daily gain and PD, respectively. Carcass gain improved with each decrease in dietary CP from 145 up to 120 g/kg DM and then levelled off. A small but significant effect of dietary CP on carcass composition was observed, due to an enhanced fat deposition in pigs fed the lowest protein content diet. Mean values of protein, fat, ash and water contents in the carcass were 101·8, 522·7, 27·6 and 353·7 g/kg respectively. PD in the eviscerated carcass was not affected significantly by dietary protein level but tended to reach a maximum value with the diet that provided 95 g CP per kg DM: 55·7 g/day at the highest feeding level assayed. Carcass energy retention (MJ/day) increased significantly (P<0·001) with decreasing dietary protein supply and on increasing level of feeding. Raising feed intake resulted in a significant decrease for carcass and a concomitant increase for viscera, as proportions of empty body weight (P<0·05 andP<0·001, respectively). Proportional weights of shoulder and ham were not affected either by dietary CP content or feeding level. Proportionate weights of dissectable fat in the shoulder and intermuscular and subcutaneous fat in the ham were not affected by CP content of the diet. In contrast, intermuscular fat content of ham was increased by feeding level (P<0·05), likely with implications for the quality of the cured meat product.

Evolution of the fatty acid profile of subcutaneous back-fat adipose tissue in growing Iberian and Landrace × Large White pigs

“…Dietary FA composition and feed intake are also extremely important factors. We have shown (Nieto et al, 2003;Barea et al, 2006) that at 50 and 100 kg BW, the carcass of IB pigs fed at 0.80 3 ad libitum intake diets with CP content ranging from sub-optimal to levels exceeding the requirements, contained 388 and 529 g/kg of fat, on average. Correspondingly, back-fat thickness measured at the last rib was 23.5 and 51 mm.…”

Effects of the dietary protein content and the feeding level on protein and energy metabolism in Iberian pigs growing from 50 to 100 kg body weight

“…A decrease in the energy requirement for maintenance is expected because a considerable increase of lipid deposition takes places in pigs growing between 50 and 100 kg (327 g/kg at 50 kg empty BW (Nieto et al, 2002) and 466 g/kg at 100 kg empty BW). Meanwhile, the contribution of metabolically active body compartments such as gastro-intestinal tract and liver to whole body size may become less (total viscera (g/kg empty BW), 118 g at 50 kg BW (Nieto et al, 2003) v. 98 g at 100 kg BW (Barea et al, 2006)). Noblet et al (1999) and Van Milgen and Noblet (1999) concluded that body muscle and, even more importantly, visceral mass explain a large part in the variation of ME m .…”

“…Animals and experimental design As described in the previous paper (Barea et al, 2006), three groups of purebred castrated male Iberian pigs of Silvela strain were used. They were from the same herd of pigs used in our previous experiment (Nieto et al, 2002).…”

“…During the experiment, the pigs were weighed once per week before feeding and for each animal the daily feed allowance for the following week was adjusted accordingly. Digestibility trials were conducted at approximately 75 kg BW, as described in Barea et al (2006). Apparent energy digestibility [d(E)] and metabolisability [m(E)] were calculated as digestible energy (DE): gross energy (GE) and ME:GE ratios.…”

“…This information, together with corresponding data on carcass quality as the main source of edible products, is relevant for application in the practical feeding of heavier animals prior to their extensive management. At this respect, in a previous paper we have reported that both the protein to energy ratio of the diet and the level of feeding affected carcass quality (Barea et al, 2006). Also, altering the feed intake resulted in significant changes in carcass and viscera as proportions of empty BW.…”