Effect of litter size and birth weight on growth, carcass and pork quality, and their relationship to postmortem proteolysis

¹ Agroscope Liebefeld-Posieux, Research Station ALP, 1725 Posieux, Switzerland; ETH Zurich, Institute of Animal Science, 8092 Zurich, Switzerland
² ETH Zurich, Institute of Animal Science, 8092 Zurich, Switzerland
³ Agroscope Liebefeld-Posieux, Research Station ALP, 1725 Posieux, Switzerland

^* To whom correspondence should be addressed. E-mail: giuseppe.bee{at}alp.admin.ch.

	Abstract

The objective of the study was to test the hypothesis that birth weight (BtW) influences growth, carcass characteristics, meat quality, and postmortem (pm) proteolysis differently when pigs originate from small (S) or large (L) litters. Swiss Large White barrows (60) used in this study originated from 20 litters with either less than 10 (S) or more than 14 (L) piglets born per litter. Within each of the S and L litters, three barrows were selected at birth: the lightest (L-BtW), the heaviest (H-BtW), and the one with a BtW nearest to the average BtW of the litter (M-BtW). The BW and total feed intake of the individually penned pigs were determined weekly. At slaughter, carcass characteristics were assessed. Meat quality traits were determined in the LM and dark portion of semitendinosus muscle (STD). Titin, nebulin, desmin, and integrin proteolysis was evaluated by SDS-PAGE and Western blot techniques, and µ- and m-calpain activities were monitored using casein zymography. Litter size affected BtW of L-BtW and M-BtW but not of H-BtW barrows (BtW x litter size interaction; P = 0.07). From weaning to slaughter, L-BtW barrows grew slower (P < 0.01), ingested less feed (P < 0.01), and were less efficient (P < 0.01) than H-BtW and M-BtW barrows. The carcass yields were higher (P < 0.01) and livers and kidneys were lighter (P 0.01) in L-BtW compared to H-BtW barrows. Regardless of BtW, barrows from S litters had higher percentages of shoulder (P = 0.02) and lower percentages of omental fat (P = 0.06) than barrows from L litters. Compared to the LM of H-BtW barrows the LM of L-BtW barrows was redder (P < 0.01). The STD of M-BtW barrows was more (P < 0.01) tender than that of L-BtW and H-BtW barrows. The extent of titin and nebulin proteolysis at 24 and 72 h pm was greater (P 0.07) in the LM of H-BtW than in L-BtW barrows. At 72 h pm integrin of the LM had been less (P = 0.08) degraded in barrows originating from S than from L litters. These results confirm the known effect of BtW on growth performance, while its impact on carcass characteristic and meat quality traits could only be partially demonstrated. Although litter size affected average BtW of the L-BtW and M-BtW barrows, its impact on growth performance, carcass characteristics and meat quality were minor. The almost complete absence of significant BtW x litter size interaction indicates that litter size affects swine growth, carcass and meat quality through its inverse relationship with BtW.

Key Words: birth weight, litter size, meat quality, proteolysis, pig