B.J. Wood

Aspects of selection for feed efficiency in meat producing poultry

Over the last five years, the costs of poultry feed ingredients have increased substantially. This has been due to an increased use of corn for ethanol production and a greater overall global feed grain demand. Across the poultry industry this has led to higher production costs and reaffirmed the importance of feed efficiency on profitability. The effect that an increase in feed costs has on profitability is a clear driver for the selection for birds with better feed efficiency. Feed efficiency selection can be achieved using a number of different analytical methods. Selection for feed conversion ratio (FCR) has been used to improve feed efficiency with success but using a ‘ratio’ trait has mathematical limitations because selection pressure tends to be placed on the component traits of FCR in a non-linear manner. Another measure, residual feed intake (RFI) shows moderate to high heritability and does not have the mathematical limitations associated with FCR. RFI has little to no correlation with production traits and this indicates that genetic improvement of RFI within a selection index can be done without the confounding issues inherent with FCR. Improvements in RFI or FCR have a favourable effect on environmental emissions and decreases the environmental impact of poultry production. The current global production of ammonia, CH4, and N2O by the poultry industry is significant, at levels of 2.1, 29.44 and 279 million tonnes CO2eq, respectively. Reductions in emissions can be achieved via improvements in feed efficiency by lowering amounts of manure excreted and decreasing emitted by-products such as ammonia and greenhouse gases (N2O, CO2 and CH4). Consequently, improvements in feed efficiency can not only increase profitability of the poultry industries by lowering production costs but also decrease environmental impact by reducing environmental emissions.

The genetic parameters of feed efficiency and its component traits in the turkey (Meleagris gallopavo)

Residual feed intake (RFI) and feed conversion ratio (FCR) can be incorporated into a breeding program as traits to select for feed efficiency. Alternatively, the direct measures used to calculate RFI and FCR can be analyzed to determine the underlying variation in the traits that impact overall efficiency. These constituent traits can then be appropriately weighted in an index to achieve genetic gain. To investigate feed efficiency in the turkey, feed intake and weight gain were measured on male primary breeder line turkeys housed in individual feeding cages from 15 to 19 weeks of age. The FCR and RFI showed moderate heritability values of 0.16 and 0.21, respectively. Feed intake, body weight, and weight gain were also moderately heritable (0.25, 0.35, and 0.18, respectively). Weight gain was negatively correlated to feed conversion ratio and was not genetically correlated to RFI. Body weight had a small and positive genetic correlation to RFI (0.09) and FCR (0.12). Feed intake was positively genetically correlated to RFI (0.62); however, there was no genetic correlation between feed intake and FCR. These estimates of heritability and the genetic correlations can be used in the development of an index to improve feed efficiency and reduce the cost of production.

Assessment of residual body weight gain and residual intake and body weight gain as feed efficiency traits in the turkey (Meleagris gallopavo)

BackgroundSince feed represents 70% of the total cost in poultry production systems, an animal’s ability to convert feed is an important trait. In this study, residual feed intake (RFI) and residual body weight gain (RG), and their linear combination into residual feed intake and body weight gain (RIG) were studied to estimate their genetic parameters and analyze the potential differences in feed intake between the top ranked birds based on the criteria for each trait.MethodsPhenotypic and genetic analyses were completed on 8340 growing tom turkeys that were measured for feed intake and body weight gain over a four-week period from 16 to 20 weeks of age.ResultsThe heritabilities of RG and RIG were 0.19 ± 0.03 and 0.23 ± 0.03, respectively. Residual body weight gain had moderate genetic correlations with feed intake (−0.41) and body weight gain (0.43). All three linear combinations to form the RIG traits had genetic correlations ranging from −0.62 to −0.52 with feed intake, and slightly weaker, 0.22 to 0.34, with body weight gain. Sorted into three equal groups (low, medium, high) based on RG, the most efficient group (high) gained 0.62 and 1.70 kg more (P < 0.001) body weight than that of the medium and low groups, yet the feed intake for the high group was less (P < 0.05) than that of the medium group (19.52 vs. 19.75 kg). When separated into similar partitions, the high RIG group (most efficient) had both the lowest (P < 0.001) feed intake (18.86 vs. 19.57 and 20.41 kg) and the highest (P < 0.001) body weight gain (7.41 vs. 7.03 and 6.43 kg) relative to the medium and low groups, respectively.ConclusionsThe difference in feed intake between the top ranked birds based on different residual feed efficiency traits may be small when looking at the average individual, however, when extrapolated to the production level, the lower feed intake values could lead to significant savings in feed costs over time.

Injurious pecking in domestic turkeys: development, causes, and potential solutions

Injurious pecking is a serious concern for commercial turkey production and welfare. The behaviour is thought to represent re-directed ground foraging, but the development and causes are poorly understood with little supporting literature. In the initial development of the behaviour, early lighting regimes and social facilitation may play contributing roles. Other factors such as the availability of foraging material, diet composition, stocking densities, and group dynamics may also affect levels of injurious pecking. Given that commercial turkeys are group-housed, alternative breeding techniques, like group selection based on social effects, might successfully reduce moralities from pecking without detracting selection pressure from economic traits. However, to better suit their behavioural needs, any genetic attempts to adapt turkeys to perform less injurious pecking should be done in combination with environmental and dietary improvements.

Factors affecting breast meat yield in turkeys

There is a global demand for turkey products and a high value attributed to breast meat from these birds. Breast meat can be considered the most important component of the carcass and consequently it is important to investigate factors that influence breast meat yield (BMY). The BMY trait is influenced by both genetics and the environment at all stages from pre-hatch until the end of the commercial growing period. Additive genetic effects appear to be the primary contributor to BMY, as there is minimal evidence for heterosis or maternal inheritance. The genetic potential for BMY is affected by sex, strain, and selection pressure within a pure line and this affects both muscle morphology and yield. For a turkey to fulfil its full genetic potential for BMY, optimal husbandry and management is required. Nutrition is an important component of production efficiency, although turkeys may be able to tolerate a reduction in dietary protein levels without a negative response in BMY, provided that the levels of all other nutrients are sufficient to meet metabolic needs. Housing conditions, such as barn temperature and lighting, also influence production efficiency. Cooler temperatures increase both weight gain and BMY, relative to a warmer rearing environment. Further, a light cycling programme with a daily set light and dark schedule is associated with higher BMY values compared to frequently alternating light and dark periods throughout the day in an intermittent lighting regime. Due to the influence of both genetics and the environment on BMY, maximisation of yield requires optimum management by all segments of the turkey production industry from the primary breeder through to the commercial grower.

The investigation of ultrasound technology to measure breast muscle depth as a correlated trait to breast meat yield in turkey (Meleagris gallopavo)

Ultrasound measurements of muscle depth were analyzed to determine if these traits could be used to increase the rate of genetic gain in breast meat yield (BMY). Two measurements of breast depth, one taken horizontally across both breast lobes and one parallel to the keel, were captured using ultrasound. Heritabilities of muscle depth traits ranged from 0.35 to 0.70. These values were greater than heritabilities of conformation scores, which ranged from 0.25 to 0.47 within sex and line. The ultrasound traits also showed strong genetic correlations to BMY, ranging from 0.43 to 0.75, indicating that selection, using ultrasound depth as a correlated information source, could result in improved BMY. Including each ultrasound trait in a linear regression model predicting BMY increased the proportion of variation explained by the models by 0.08 to 0.17, relative to using conformation score as the only in vivo estimate. Based on results from a simulated turkey breeding program with selection pressure only on BMY, the ultrasound measures could increase the accuracy of a selection index for BMY by 0.02 to 0.16. As a result, ultrasound technology has the potential to improve the rate of genetic gain in BMY in a breeding program.

Genotype × environment interaction as it relates to egg production in turkeys (Meleagris gallopavo)

Genotype x environment (GxE) interactions can reduce the accuracy of a model to predict the performance of an animal and have an undesirable influence if not accounted for when estimating breeding values. Consequently, identification of these GxE is necessary when considering a turkey breeding program. Reranking based on the genetic prediction of turkey egg production, fertility, and hatchability in different seasons was indicative of a potential GxE interaction. Quantification of the GxE interactions was based on the genetic correlation estimated when traits were expressed in different seasons. Egg production was expressed as the percentage of days with an egg produced; fertility represented the proportion of hatched eggs that contained a fertile embryo; and hatchability was defined as the percentage of fertile eggs that produced a live bird. Variance components and heritability for egg production, fertility, and hatchability were estimated using ASReml. The heritability (h(2)) of egg production was calculated to be 0.32 for both lines with the phenotypic and genetic variance, 141.3 and 45.58 (percent days with egg produced)(2) and 118.3 and 38.35 (percent days with egg produced)(2) for female and male lines, respectively. The h(2) estimates for fertility were 0.08 in both lines with and of 293.3%(2) and 24.03%(2), and 576.9%(2) and 48.43%(2) for female and male lines, respectively. The hatchability h(2), and estimates were 0.09, 267.1%(2), and 24.44%(2), respectively, for the female line and 0.15, 582.2%(2), and 90.01%(2) for the male line, respectively. Based on an animal model, the variance components were used to calculate estimated breeding values for each trait. The annual fluctuation in estimated breeding values resulted in the need to evaluate egg number, fertility, and hatchability as 2 traits, summer and winter lay. The correlation between the 2 traits was less than unity (female line: r(egg production) = 0.76, r(fertility) = -0.20, r(hatchability) = 0.75 and male line: r(egg production) = 0.86, r(fertility) = 0.19, r(hatchability) = 0.68) suggesting a GxE interaction, and animals will significantly rerank in genetic predictions for these reproductive phenotypes in different seasons of lay. Egg production, fertility, and hatchability in turkeys could be considered as 2 distinct traits in an animal model based on season of lay.

An analysis of beak shape variation in two ages of domestic turkeys ( Meleagris gallopavo ) using landmark-based geometric morphometrics

The objective of this study was to assess beak shape variation in domestic turkeys (Meleagris gallopavo) and determine the effects of age, sex, and beak size on beak shape variation using geometric morphometrics. Dorsal and right lateral images were taken of 2442 turkeys at 6 and 18.5 weeks of age. Landmarks were digitized in tpsDig in three analyses of the dorsal upper mandible, lateral upper mandible, and lateral lower mandible shape of each turkey at both ages. The coordinate data were then subjected to a principal components analysis (PCA), multivariate regression, and a canonical variates analysis (CVA) with a Procrustes ANOVA in MorphoJ. For the dorsal images, three principal components (PCs) showed beak shape variation ranged from long, narrow, and pointed to short, wide, and blunt upper mandibles at both ages (6 weeks: 95.36%, 18.5 weeks: 92.21%). Three PCs showed the lateral upper mandible shape variation ranged from long, wide beaks with long, curved beak tips to short, narrow beaks with short, pointed beak tips at both ages (6 weeks: 94.91%, 18.5 weeks: 94.33%). Three PCs also explained 97.80% (6 weeks) and 97.11% (18.5 weeks) of the lateral lower mandible shape variation ranging from wide and round to narrow and thin lower mandibles with superior/inferior beak tip shifts. Beak size accounted for varying proportions of the beak shape variation (0.96–54.76%; P < 0.0001) in the three analyses of each age group. For all the analyses, the CVA showed sexual dimorphism in beak shape (P < 0.0001) with female upper mandibles appearing wider and blunter dorsally with long, curved beak tips laterally. Whereas male turkey upper mandibles had a narrow, pointed dorsal appearance and short, pointed beak tips laterally. Future applications of beak shape variability could have a genetic and welfare value by incorporating beak shape variation to select for specific turkey beak phenotypes as an alternative to beak treatment.