THE commercial turkey breeding sector has been successful at improving traits important for commercial turkey production, such as bodyweight and breast meat yield, according to a research report by Dr. Michael Lilburn of The Ohio State University.
However, he said, the continual selection for economic traits may have negative correlated effects on reproductive efficiency.
In a recently completed study funded by the U.S. Poultry & Egg Assn. (USPOULTRY) and the USPOULTRY Foundation, Lilburn studied controlling the bodyweight of turkey breeder hens without feed restriction.
The turkey industry has used artificial insemination to maintain high levels of fertility, Lilburn pointed out, but no simple management tool has yet been identified for optimizing production efficiency in commercial turkey breeder hens.
It is accepted that controlling the bodyweight of turkey hens during rearing is essential for optimizing egg production, but physical feed restriction of hens — like what is done for broiler breeders — is not an accepted option, Lilburn explained. Thus, there is a need to conduct studies with the objective of controlling bodyweight in replacement hens via ad libitum, controlled feeding of low-nutrient-dense diets.
For the study, Lilburn created different bodyweight groups during rearing via dietary manipulation, which was followed by individual weighing of hens at 24 weeks and allocating them into replicate pens of heavy, medium and light bodyweight hens, which were designed to bracket the target bodyweights recommended by the primary breeder, Hybrid.
In addition to hen-day egg production and egg weight determinations, a sample of hens from each treatment was euthanized for carcass, reproductive organ and selected skeletal measurements at one week and three weeks post-photostimulation (30 weeks and 32 weeks of age, respectively), Lilburn noted.
The dietary rearing treatments resulted in hens that weighed 24.45 lb. and 23.0 lb. at 24 weeks, 26.6 lb. and 25.6 lb. at 30 weeks and 24.8 lb. and 24.1 lb. at 42 weeks. The heavy, medium and light hens weighed 27.6, 26.3 and 24.3 lb. at 30 weeks and 25.6, 24.6 and 23.0 lb. at 42 weeks.
After the onset of hen-day egg production, the light treatment hens had significantly better hen-day egg production than either the medium or heavy hens, Lilburn reported. The heavy hens had approximately a 2 g improvement in egg weight at 4, 8 and 10 weeks of egg production compared with the light hens, he noted, adding that the medium-weight hens were intermediate.
At 30 weeks of age, hens in the heavy, medium and light bodyweight groups had corresponding differences in carcass weight, but there were no significant effects on shank length, follicle number or reproductive tract weight, Lilburn reported. At 32 weeks, there were also no bodyweight treatment effects on follicle number or reproductive tract weight, but there was a progressive decrease in femur, tibia and shank length in the sampled hens as bodyweight declined, he added.
Total carcass lipid (as a percent of dry matter) increased from 42% to 51% between 30 and 32 weeks of age, but there were no significant differences between bodyweight groups, Lilburn reported. The greatest increase in carcass lipid occurred in the light bodyweight group (41.7% to 53.5%), and this resulted in a marginal age-by-bodyweight interaction (P < 0.087).
Across all three bodyweight groups, there was a significant decline in bodyweight between 30 and 42 weeks of age.
Lilburn concluded that the lower plane of nutrient intake during rearing significantly reduced bodyweight at 24 and 30 weeks. Carcass lipid increased between 30 and 32 weeks, particularly in the lightweight hens. At 32 weeks, there was a decline in femur, tibia and shank length with each decrease in bodyweight among the heavy, medium and light groups, and this may have reduced maintenance energy needs and allowed for increased carcass lipid deposition, he said.
Enriched colony cages
USPOULTRY and the USPOULTRY Foundation also announced the completion of a funded research project at Michigan State University that examined the stocking density of enriched colony cages for laying hens.
Drs. Darrin Karcher and Maja Makagon at Michigan State University studied the impact of stocking density on egg production and the well-being of laying hens in enriched colony cages and found minimal differences in measures of production and well-being at the various studied stocking densities during the period of 17-69 weeks of age.
Karcher and Makagon noted that enriched colony cages are becoming more popular for laying hens. As the commercial laying hen industry begins to phase out conventional cages and move toward alternative housing systems, research studies need to generate data that can provide guidance on management practices relative to the housing system, they said.
Their overarching objective was to investigate laying hen space allocation in enriched colony systems, with a long-term goal of providing a better understanding of how production and well-being are intertwined to aid producers in making sound decisions and to provide information to address issues raised by consumers.
Karcher and Makagon said the specific objectives for this grant were to: (1) evaluate the performance of a single strain of laying hens at different stocking densities in enriched colony cages, and (2) assess the impacts of different stocking densities on laying hen well-being using measures of health, stress and behavior.
From 17 to 69 weeks of age, W-36 laying hens were housed in enriched colony cages at 464 sq. cm, 580 sq. cm, 651 sq. cm, 748 sq. cm, 799 sq. cm and 929 sq. cm. Production measures collected included egg production, bodyweight, egg weight and feed disappearance.
According to Karcher and Makagon, hen-day egg production was similar across the various densities. Hens with greater than 748 sq. cm of space per hen had slightly higher production compared to hens with less space allowance, they reported. Egg production declined over time, with all treatments ending at around 79% of peak lay, with the exception of the 929 sq. cm treatment, which ended at around 82%.
Egg weights, feed consumption and bodyweights were similar across all treatments, the researchers said.
The other aspect of the trial was to evaluate the health, stress and behavior of the birds using the European Union Welfare Quality (WQ) Assessment Protocol for Poultry, Karcher and Makagon said, noting that the avoidance distance test, which assesses the hen's response to humans, was not practical as the hens interacted with farm staff daily during egg collection and were, therefore, habituated to the presence of people.
The fear response of the hens was only assessed using the novel object test. The hen's responses to the novel object, a colorful rod, did not differ by density, Karcher and Makagon noted.
According to the WQ protocol, hen health can be assessed through observation of hens with labored breathing/sneezing and visual examination of feces to identify enteric infections. Based on these procedures, the researchers reported that hen health was deemed not to be an issue, and this was confirmed by an avian pathologist who conducted necropsies of mortality.
Due to lower-than-expected numbers of pullets at placement, it was not possible to sacrifice pullets, and the adrenal weights of the pullets — an indicator of stress — were not evaluated.
The WQ measures of comb abnormality, comb wound, keel deformation or fracture, skin lesions, toe damage, foot condition and plumage damage were assessed bimonthly in 10% of each enriched colony population. Keel deformation or fracture increased over time and was similar among all treatments over time (20-30%), Karcher and Makagon reported.
The plumage damage was assessed on seven different areas of the hen. All areas became worse with time (increased feather loss or feather breakage), and the areas of the head, abdomen and back were affected by density, with the proportion of hens having worse plumage quality at a space allotment of 464 sq. cm, the researchers noted.
Karcher and Makagon concluded that further research should additionally focus on finding the density between 651 sq. cm and 748 sq. cm at which improvements to feathering occur.
USPOULTRY is an all-feather organization representing the complete spectrum of the poultry industry. Its mission is to progressively serve member companies through research, education, communication and technical assistance.
Researchers at Scotland's Rural College (SRUC) have found that feeding herbs to growing chickens can increase their growth rate.
A nutrition experiment carried out by researchers from SRUC's Avian Research Centre in Ayrshire revealed that a mix of essential oils, including lemon, thyme and sage, improves the bird's growth rate, which means more breast meat for consumers.
While the essential oils don't affect the flavor of the bird's meat, the researchers believe that they increase the amount of digestive enzymes in the chickens' gut that help them absorb more nutrients and gain weight.
Previous research showed that essential oils can offer a promising alternative to antibiotics due to their antibacterial, antifungal and antiviral properties, yet there have been few studies suggesting that they promote growth. However, this particular mix of essential oils (basil, caraway, laurel, lemon, oregano, sage, tea and thyme) shows that some do have the potential to increase weight gain, the SRUC announcement added.
Farina Khattak, an SRUC researcher who led the study, said, "One of the key benefits we found with the herbal mix was a much improved feed-to-gain ratio. This refers to the amount chickens eat and then how much weight they put on. With the herbal supplement, the birds could eat the same amount of food yet gain more weight, which could mean increased profits for producers."
The study compared the typical feed used by commercial poultry companies to one supplemented with the herbal mix and found that the latter resulted in chickens that grew faster and had an increased amount of breast meat.
The birds were grown from one day of age until they were 42 days old, mimicking commercial rearing conditions. Birds fed the herbal mix-supplemented diets were 6.6% heavier than those fed the control diet and had substantially bigger portions of breast meat — 7-10% heavier than the control birds.
The herbal mix (Tecnaroma Herbal Mix PL) used in this study was developed by the Italian feed company Tecnessenze.