Second in a three part series. Dr. Jacquie Jacob shares her research on how to effectively use heritage breeds for small-scale meat production operations.
As discussed in Part 1 of this three part series, we ran a study at the University of Kentucky poultry research farm comparing three heritage breeds (Black Australorp, Barred Plymouth Rock and Rhode Island Reds) to the commercial-type meat chicken (known as a “broiler”) raised either completely indoors or finished in outdoor pens on alfalfa pastures.
Three heritage breeds used for broiler flocks: Rhode Island Reds, Black Australorps, Barred Plymouth Rocks. Photos by Stephen Patton, University of Kentucky.
Weighing the Carcass
At the end of the growth study, two male and two female chickens were randomly selected from each replicate of the eight different groups. They were processed, allowed to chill, weighed, and cutup for parts. The carcass weight was recorded for each fully processed chicken. Commercially this is referred to as the WOG weight – weight without giblets (heart, liver, gizzard). This weight is then expressed as a present of live weight to determine yield. When we ran the statistics, we found that the commercial strain had the highest percent WOG yield (averaging 75.2%), with the yield being higher for those raised on the floor (76.1%) compared to those finished on pasture (74.4%). Chickens of all three heritage breeds had similar WOG yield, averaging 63.7% which was considerably lower than the yield of the commercial strain. There were no differences between those raised indoors and those finished on pasture.
Breast Meat
The most valuable part of a chicken carcass is the breast. The commercial strains had twice the breast yield as a percent of live weight than the heritage chickens (25.6% versus 12.5%). The high breast yield is from the Cornish breed used in the original crosses, plus generations of genetic selection for increased growth rate and breast yield. Those chickens finished on pasture had slightly higher breast yields than those raised indoors (16.1 versus 15.4%, respectively).
While the commercial strain had larger breast size, they had slightly lower leg yield (40.8%) compared to the heritage breeds (45.6%). For the Barred Plymouth Rocks only, those finished on pasture had higher leg yield compared to those raised entirely indoors (46.1 versus 43.7%, respectively). The commercial chickens also had lower wing yield (10.1%) than the heritage breeds (averaging 13.9%). In addition, those chickens finished on pasture had lower wing yields (12.7%) than those raised indoors (13.2%).
Comparing cross-sections of a commercial chicken (left) and a Rhode Island Red (right). Photo by Stephen Patton, University of Kentucky.
We sent breast and thigh meat samples to an outside laboratory for nutrient analyses. The meat samples were analyzed for moisture, protein, fat, saturated fatty acid, polyunsaturated fatty acid, and monounsaturated fatty acid contents. For the thigh samples only, cholesterol content was also determined.
Compared with Commercial Chickens
While the commercial-type chickens had larger breasts, the meat had significantly lower percent protein (21.6%) compared to the heritage breeds (23.4%). There were no significant differences in total fat among the four types of chickens. Fats are made up of fatty acids, which are basically long strings of carbon atoms. If there are only single bonds between the carbons, they are referred to as saturated fatty acids. If they have a double bond or two, they are referred to as unsaturated fatty acids. If they have a single double bond, they are mono-unsaturated and if they have many double-bonds they are referred to as poly-unsaturated. Published research has indicated that dietary polyunsaturated fatty acids are the best for our health. There were no significant differences in the levels of saturated and polyunsaturated fatty acids between the commercial-type chickens and the heritage breeds. The levels of monounsaturated fatty acids, however, were higher in the commercial strains (0.41%) than the heritage breeds (0.26%).
Benefits of Finishing on Pasture
There was an effect of finishing the chickens on pasture on nutrient content, with those finished on pasture having higher protein (23.2%) compared to those raised indoors (22.6%). Finishing on pasture also resulted in lower saturated (0.17 versus 0.41%) and polyunsaturated (0.16 versus 0.35%) fatty acids. This is contrary to the claims that meat from chickens raised on pasture is higher in polyunsaturated fatty acids than those raised indoors.
For the thigh meat, protein content was again lower for the commercial strain (17.4%) compared to the heritage breeds (18.7%). For total fat content, there were differences among the breeds. While the commercial chickens had the highest thigh fat content (8.4%), the Rhode Island Reds had the lowest (5.4%) with the Black Australorps (6.5%) and Barred Plymouth Rocks (7.5%) being in between these two extremes. There was no effect of breed on the levels of the different types of fatty acids. Finishing chickens on pasture, however, resulted in higher protein but lower total fat levels. As a result of the lower total fat content, the levels of mono-unsaturated and poly-unsaturated fatty acids were also lower in thigh meat from chickens finished on pasture compared to those raised indoors. The level of thigh cholesterol content of the commercial-type chicken, however, was higher for those raised on pastures.
The remainder of chickens from the study were sent to a USDA-inspected facility for commercial processing. These chickens were used for additional carcass quality tests. We looked at cooking loss for the breast and thigh meat from sampled chickens. Cooking loss refers to the change in the weight of the meat when cooking. The weight loss can be due to moisture and/or fat loss.
Variations Among Heritage Breeds
For breast meat, the percent cooking losses was highest for the Rhode Island Red chickens (13.4%) with no difference between those raised indoors and those finished on pasture. Conversely, the breast meat had lower cooking loss from chickens finished on pasture versus those raised indoors for the Black Plymouth Rocks (9.9 versus 11.5%) and Black Australorps (9.9 versus 11.8%). For the commercial chickens, overall percent cooking loss was 12.3% with no differences between those raised indoors and those finished on pasture.
For thigh meat, cooking loss was the highest for the commercial strains. In addition, cooking loss was higher for those commercial chickens raised on the floor (20.6%) compared to those finished on pasture (15.4%). There was no significant effect of production system on the cooking loss from the meat of the heritage breeds. The overall cooking loss was highest for the Barred Plymouth Rocks (12.3%) and least for the Rhode Island (9.87%) The cooking loss from the thigh meat from the Black Australorps was intermediate between the two extremes at 10.6%.
The cooking loss values obtained for both the breast and thigh meat were considerably lower than those reported by the USDA in 2012 for commercially-produced chicken meat. They reported a 28% loss from breast meat and a 31% loss from thigh meat. This may be due to the injection of commercial chicken products with marinating liquids, which was not done in this study.
Goals for Small Producers
The goal for small-scale producers is to develop a better tasting chicken. We ran a taste test with the breast meat samples from the study. The participants had no prior training and were asked about tenderness, juiciness, off flavors, chicken flavor and acceptability from the samples provided. For tenderness, juiciness, chicken flavor and overall acceptability, the participants assessed the samples on a six-point scale. For tenderness the scale when from extremely tender (6) to extremely tough (1). For juiciness the scale was from extremely juicy (6) to extremely dry (1). Chicken flavor scale was from extremely intense (6) to extremely bland (1) and acceptability from extremely acceptable (6) to extremely unacceptable (1). For the off flavor, the scale was from 1 (not detectable) to 4 (extremely detectable). So, for tenderness, juiciness, and overall acceptability, the higher the number the better. For off flavor, the lower numbers are better. For chicken flavor, the best intensity will depend on the previous experience of the participant since those that are used to bland chicken may be averse to extremely intense chicken flavor.
Tender and Juicy
There was no effect of the different study parameters on the tenderness reported by the participants. For juiciness, there were several factors interacting and it was very difficult to pull apart the different components, but overall the juiciness ratings ran from 2.97 for the breast meat from Rhode Island Red males raised indoors and the commercial broiler males finished outside, to 4.53 for the Black Australorp females raised indoors. Off flavors were highest for the Australorps at a rating of 2.28 versus an average of 1.88 for all the other breeds. Off flavors were also detected more in chickens finished on pasture (2.12) than those raised indoors (1.83). Chicken flavor was found to be slightly more intense for the female chickens (3.66) versus the males (3.28). There was no effect of breed, management system, or the gender of the chicken on the acceptability of the breast meat. The overall rating was 3.72.
Shelf-Life
Another factor of poultry meat quality is shelf-life. This is typically measured as T-Bars, which is short for 2-Thirobarbituric Acid Reactive Substances. The higher the T-Bar value, the more rancid the meat. The results suggested that there were no differences between the breeds, but pasture-finished chickens have lower breast meat peroxidation during seven days of retail display which may transfer into increased shelf life of the meat.
Smaller Birds, Big Flavor
While heritage chickens may provide small-scale chicken meat producers with an alternative to the commercial-type chickens, the possible increased flavor of the older chickens may not be acceptable to everyone. The producers need to target a niche of consumers interested in the more flavorful chicken that are willing to pay the premium price needed to cover the higher costs of production.
Dr. Jacquie Jacob is a poultry extension associate at the University of Kentucky and works with all types of poultry production from backyard flocks to large commercial operations. She also works with youth poultry programs. She previously worked with extension programs in Florida and Minnesota.
Jacquie received her B.S. in poultry management from the University of British Columbia (UBC) in Vancouver, Canada. After completing her degree, she spent four and a half years working on a poultry project in Mozambique, Africa. She received her master’s and doctorate from UBC in monogastric nutrition. Although her doctorate is from UBC, Jacquie completed her Ph.D. research at the University of Nairobi in Kenya looking at alternative ingredients for poultry feeds.
Jacquie has worked with poultry Extension programs in Florida, Minnesota, and currently in Kentucky.
1 Comment
Good study but the end game was not pretty. You callled real chicken flavor off flavors. I find it ironic that you want to promote the heritage but put an article putting down the real flavos of chickens.