Research at Virginia Tech confirmed several heritage turkey varieties are more disease-resistant than commercial turkey strains. Findings also included how heritage turkeys are better suited for pasture production than their commercial broad-breasted counterparts. Read Part I for details on the pasture portion of the study.
Black turkey toms
Disease Resistance
Virginia Tech researchers assessed the immune function of five varieties of heritage turkeys, the Black, Bourbon Red, Narragansett, Royal Palm, and Slate. They compared results to a commercial strain of broad-breasted white turkeys. Results confirmed heritage turkeys had more robust immune responses.
At three time points, the commercial turkeys had lower packed cell volume and total protein than the standard-bred varieties. Packed cell volume measures red blood cells, which carry oxygen to the body’s cells. Total protein measures globulins and albumin, critical to immune response.
Black Slate turkey
Immune function was evaluated by measuring the number of lymphocytes, a specific type of white blood cell involved in responding to bacteria and viruses. They also measured how responsive the lymphocytes were to stimulation in the laboratory. While no differences in lymphocyte recovery were observed between varieties, lymphocyte proliferation was lower in the commercial variety than in standard-bred varieties of turkeys. Lymphocyte proliferation is indicative of immune function.
Heritage turkey varieties had significantly higher survivability when directly exposed to disease in the laboratory. Challenged by two diseases – Hemorrhagic Enteritis Virus and E. coli – all commercial birds died within three days after infection with E. coli. In contrast, most standard-bred turkeys survived past three days of bacterial infection, and none of the Black, Slate, or Bourbon Red turkeys died. Study results support the scientific theory that selection for an increased growth rate is negatively correlated with immune function.
Heritage turkey varieties have more vigorous immune systems, and should therefore be more tolerant of the variable conditions of pasture production. These active foragers also offer greater tolerance to stressors. They can mate naturally and can brood their own eggs and raise their own poults. Combined with the results of pasture production research as detailed in Part I, these exciting findings confirm the value of the genetic variability embodied in heritage turkeys.
The history of the beloved turkey as an American culinary centerpiece predates the founding of the United States. Its history traces to domestication began 2,000 years ago by the Aztec and Mayan peoples. Indigenous to both North and South America, only 1,335 domesticated heritage breeding birds were found in the US in 1997. While numbers have grown over the past 25 years, challenges such as marketing, breeding, and attracting younger growers remain. The Livestock Conservancy counts eight heritage turkey varieties on our Conservation Priority List.
Portions of this blog first appeared in How to Raise Heritage Turkeys on Pasture. An updated edition of this popular resource will be available later this fall thanks to a generous gift from McMurray Hatchery.
Turkey group
