Fat distribution in swine as influenced by liveweight, breed, sex and ration

The effects of liveweight, breed group, sex and plane of nutrition were studied in 23 Duroc × Yorkshire, 42 Hampshire × Yorkshire and 27 Yorkshire × Yorkshire barrows and gilts fed either a low or high energy ration [2757 kcal digestible energy (DE)/kg and 15.3% protein, or 3652 kcal DE/kg and 19.9% protein]. They were slaughtered at 68, 91 or 114 kg liveweight. Nine barrows and 8 gilts of the same breed groups were slaughtered at 23 kg liveweight to determine carcass composition at the start of the experiment. Half-carcasses were divided at the 11th and 12th ribs and dissected into individual muscles, depot fats and bones. Fatty tissue was separated into subcutaneous, intermuscular and body cavity types of depot fat. As liveweight increased from 23 to 114 kg, a differentiation among depot types occurred. Fat distribution in 23-kg pigs was made up of 78% subcutaneous, 18% intermuscular and 4% body cavity fat. At 114 kg liveweight, subcutaneous fat was 84%, intermuscular fat 13% and body cavity fat 2.3%. Within each depot type, differential deposition between front and hind quarters was most noticeable between 23 and 68 kg liveweight. During this period, more of the intermuscular and body cavity fat was deposited in the front quarter, while a greater proportion of the subcutaneous fat was deposited in the hind quarter. Breed, sex and ration did not influence the percentage relationship among depot fat types but did within types. Thus, the fatter carcasses (produced by Duroc × Yorkshire pigs, barrows and high-energy-fed pigs) had a greater proportion of their intermuscular fat in the hind quarter than did the leaner carcasses (from Hampshire × Yorkshire and Yorkshire × Yorkshire pigs, gilts and pigs fed the low energy ration).