DIFFERENCES IN COMMERCIAL PIGS REPRESENTATIVE OF 1980 AND 2005 GENETIC LINES WHEN REARED ON 1980 AND 2005 REPRESENTATIVE FEEDING PROGRAMS

Many changes occurred in the U.S. swine industry from 1980 to 2005. Integral parts of these industry wide changes were brought about by improvements in genetics and feeding programs. A study was conducted at North Carolina State University in an attempt to quantify both the total change in the pork industry and what portion of this change is attributable to genetic and/or feeding program improvements.

To accomplish this two groups of pigs, genetic samples representative of the 1980 and 2005 commercial industry, were fed feeding programs representative of the same time periods. Pigs representative of the 2005 commercial industry were obtained from a North Carolina commercial producer. Pigs representative of the 1980 swine industry were farrowed from females selected for minimum genetic gain since 1979 bred with semen commercially available around 1980. The 2005 feeding program was based on current industry practices while the 1980 feeding program was based on recommendations from the 1978 Pork Industry Handbook. Pigs from each genetic sample were randomly assigned to one of the feeding programs.

Pigs were on test from weaning (BW = 7 kg) to slaughter (BW = 116 kg). Feet and leg structure/mobility was scored on pigs. Body weights were collected every two weeks and feed disappearance was also collected at this time. Daily gain, feed intake and feed efficiency were calculated. Beginning in week 8 or 10 Backfat depth and loin muscle area at the 10th rib were measured with real-time ultrasound every four weeks and were measured on the carcass 24 hours post mortem. From these data, lean gain and lean efficiency were calculated. Other carcass measures included carcass weight, dressing percent, carcass length, backfat depth (first rib, last rib, last lumbar) and fatty acid composition of subcutaneous adipose tissue. Pork quality measures collected on the loin and ham included; pH (45 minute and 24 hour), L*, a*, b*, National Pork Board marbling score (1-10), firmness score (1-3), wetness score (1-3) and color score (1-6). National Pork Board marbling score, chemical analysis of percent intramuscular fat, 48 hour percent driploss and Warner-Bratzler shear force test were also measured on the loin. A consumer sensory panel and trained flavor and texture descriptive panel were conducted on loin samples.

OVERALL CHANGES FROM 1980 TO 2005 IN KEY ECONOMICALLY IMPORTANT TRAITS

The following graphs represent percentage change due to genetics, feeding program and overall change from 1980 to 2005 in specific growth traits and carcass traits.

The black portion is change due to genetics and the white portion is change due to feeding programs. If both are in the same direction the total bar is the cumulative change; however if not, then the white bar is where the cumulative change is. The * represents trait where a genetic sample by feeding program interaction was observed. This simply means the changes were not additive.

These results show that changes in both genetics and feeding programs from 1980 to 2005 increased lean efficiency, an important trait in regards to overall efficiency in the grow-finish phase of swine production. In regards to genetic effects, improvements in pork quality can coincide with the improvements in lean efficiency. Unfortunately the same cannot be said for changes in feeding program. The improvements due to feeding program resulted in unfavorable effects on important pork quality traits, which then translated into poorer consumer acceptance of the final product.

-Justin Fix and Todd See