Growth, Efficiency and Carcass Composition of Three Frame Sizes of Hogs Slaughtered at Fat Constant or Weight Constant Endpoints

Abstract

A total of 193 Hampshire sired crossbred barrows were allotted in a completely randomized design to three frame size groups (small, medium and large). Birth weight and forearm length were the criteria used in the allotment procedure. Hogs were slaughtered either at a fat constant endpoint (2.54 cm) or weight constant endpoint (110 kg). Growth and carcass composition were determined.

In the first of three experiments, pigs were penned by frame. Hogs were slaughtered at an estimated fat endpoint of 2.54 cm measured at the 10th-11th rib interface. No differences (P $>$.05) were observed for days on test or feed efficiency. The 10th rib fat measurement was the same (P $>$.05) among frame groups.

Prediction equations were developed following complete physical separation and chemical analysis of the carcasses. Percent ham lean (PHL) was the best single estimate of percent carcass lean and accounted for 87.6 to 94.9% of the variation in estimating percent carcass lean (PCL).

One hundred fifteen crossbred barrows were individually penned in the second experiment. A randomly selected group of 15 pigs were slaughtered at the beginning of the experiment and subjected to complete physical separation and chemical analysis. Carcass measurements were not different (P $>$.05).

The remaining barrows were slaughtered as they reached 2.54 cm measured at the 10th rib. Feed efficiency was the same (P $>$.05) for all experimental animals. Carcass composition and estimated PCL were not different (P $>$.05) among frame groups. Large frame hogs produced more (P $$.05) age. Experimental animals were individually penned and removed for slaughter as they reached 110 kg live weight. Feed efficiency was the poorest (P $$.05) among frame groups. Estimated PCL increased (P $<$.05) with increasing frame size. Hogs marketed at the same weight differed (P $<$.05) in carcass composition as indicated by the estimated PCL.