Genetics

Background 2048 views update:Mar 9, 2016

Innovatively assessing performance in layers

Detailed management and assessment of the male broiler breeder is an essential factor in producing a uniform bird with optimum performance from the rearing stage through to depletion. The males form half of the breeding value of a flock and are therefore just as important as the females. Close observation and evaluation, preferably on a daily basis, will help identify potential issues within the flock or recognise problems in males that may impair future fertility.

By Vanessa Kretzschmar-McCluskey and Michael Longley; Global Technical Transfer Managers, Aviagen

Observation and awareness of male condition is important throughout the life of the flock.  Achieving the optimum physical condition, maintaining it, and ensuring that it does not deteriorate are key to performance. The information provided in this article will emphasise methods of effectively managing broiler breeder males based on body composition and condition and highlight a novel approach used to provide an objective evidence base for the condition scoring scale.

In the past, there was a belief that as long as the nutritional specifications set by the parent stock company were being followed, little emphasis should be placed on concrete values associated with the body condition scoring scale. However, over time, producers have begun to realise that physically evaluating the birds is equally as important as following nutritional guidelines. While the idea of condition scoring (a traditional form of assessing farm animal performance) is not new in itself, there are new technologies which can be applied to gain a fresh perspective into what characterises a good quality male. In the latest edition of the Parent Stock Handbook, researchers and technical advisors at Aviagen have used Computed Tomography (CT) X-ray equipment to provide a "behind the scenes" view of male body composition and thereby confirm the relationship between the recommended condition scoring method and a bird's body shape and condition.

The traditional method
Body condition, also known as fleshing, can be used in conjunction with body weight to quantitatively measure the performance of a flock. Aviagen recommends that a scale of 1 to 3 is used to appraise fleshing (the amount and shape of the breast). A score of 1 denotes an under-fleshed bird; a score of 2 indicates an ideally fleshed bird, while a score of 3 represents over-fleshing. Breast shape and fleshing should be monitored on a weekly basis and all birds being weighed should be evaluated. Since the assessment of body condition score can vary between individuals, it is generally best practice to have the same person score the males each week.

The procedure for assessing condition can be properly followed by holding the bird by both legs and running the hand over the keel bone. The prominence of the keel, and the volume, shape and firmness of the breast is observed. In the example used in image 1, a 26-week old male considered to be ideally fleshed (a condition score of 2) is being evaluated. In this case, the keel bone should be easily felt, but not prominent and the breast muscle should be firm and rounded, filling both sides of the keel. Scores should be recorded and the average score determined per week. By plotting the average scores, trends can be seen and monitored over time.

An unconventional approach
Since the traditional method of body condition scoring is moderately subjective, it is important to explore new and alternative approaches to help alleviate the dependency on one person to accurately identify the correct grade on a weekly basis. This is where the use of Computed Tomography (CT) X-ray technology, also known as Computer Axial Tomography, or CAT scan (a two-dimensional image of a slice or section of a three-dimensional object) came into play. Birds considered to be a condition score 1, 2 or 3 were selected at several different ages during the life of a flock. 

Parent stock handbook
The selection of model birds for each category was done by using the visual guidelines stated in the Parent Stock Handbook and substantiated by the teste / vasdeferens condition of the males. Primarily used in human medicine as a way of producing internal images of the body, a CT scanner emits multiple beams through an object to create a much more detailed image than can be created by x-ray alone. Inside the CT scanner is an x-ray detector, which can see hundreds of different levels of density.  Because of this, it can distinguish tissues of different densities (muscle, fat and bone) to provide a detailed image of body composition and shape. Image 2 shows an example of a CT scanner used to evaluate bird body condition.

Due to the use of this tool in an inventive way, it is possible to gain insight into the inner workings of the broiler breeder male. By following the nutritional guidelines outlined in the Parent Stock Handbook, it is possible to get an idea of what should be occurring physiologically within the bird at a particular age. Using the CT scanner we can then illustrate the condition scoring scale in a way never seen before.

The computer generated images of the males sent for scan allows us to grasp and appreciate how the actual ratios of muscle:fat:bone differ between condition scores. In this way we can provide the manager with a clearer understanding of what birds should look and feel like at different condition scores, improving and promoting the assessment of male condition. While the concept of condition scoring will always be subjective to a degree, illustrating the condition scoring system in this way helps to reinforce the justification and objectivity for assigning a particular score to a bird.

Increase objective scoring
Managing male broiler breeders can be a daunting task. By applying a human device to the world of poultry to help producers better visualise the condition scoring system, we have tried to increase the objectivity of condition scoring. Regular monitoring and recording of flock condition over time will provide a comprehensive and thorough data set, which can be used to support management decisions and help recognise and solve problems. It is not enough to simply weigh males to determine if they are too heavy or thin, a comprehensive physical assessment of male condition must also occur. The data obtained must be recorded and monitored and trends assessed over time.

However, body weight and body condition are only one part of a combination of physical assessments that should be used for managing males and male ratios within a flock. Correct observation of visual cues, such as posture, feet and leg health (straight legs with no bent toes or footpad abrasions), beak shape, colour around the comb, wattles and eye area (which should be an intense red colour), vent condition (the vent should be red in colour, moist and showing some signs of feather loss) and feathering (active males should show partial feather loss around the thighs, shoulders, breast and tail), are also necessary if managers are to get a good idea of birds that may or may not be contributing to the fertility of the flock. When condition scoring is used in conjunction with, body weight measurements, and visual assessments of the birds, a total management package for males is created.

Well balanced flock
Body condition or fleshing is a good indicator of bird condition and is particularly useful for males. Birds that are over- or under-fleshed are likely to have problems with fertility, resulting in the loss of good, quality hatching eggs. In the past, body weight has been viewed as the primary guide to determining whether birds were meeting their full potential. 

However, there is clear evidence that body weight alone will not give the complete picture of male potential, and should not be used as a stand-alone method for driving management decisions. It is both possible and probable that within a flock there will be males of the same body weight, which have entirely different body composition. The one bird is shorter and fatter, while the other is taller and leaner.

Due to these variations, and the need for different management styles as a result of them, it is necessary to look at all characteristics of the bird including uniformity, target body weights and ultimately fertile hatching eggs are to be achieved. By working closely with allied industry professionals, researchers, geneticists, and customers, innovative options for the betterment of global poultry production can and should be investigated. Fresh perspectives on management must be developed and shared with those who need it the most: our technical managers and customers. This new advice be presented in a way that is technically and scientifically accurate, but easily understood from a production viewpoint. Following the principles outlined in the Parent Stock Handbook, it is possible to apply best management practices and accomplish the goal of a well-balanced flock.

Using body weight and condition to manage a flock

It is important that as well as body condition, body weight, along with uniformity,  are taken into consideration when deciding upon feeding management adjustments to a flock.  By utilising the proper strategies, it is possible to make well-informed decisions concerning modifications to feed or production plans.  Table 1, taken from the Parent Stock Handbook, outlines how the use of condition scores in conjunction with body weights can be used to determine the best fit management strategy for males.
By determining whether or not the sample group of males is on target for body weight and by assessing their condition score, decisions about feed increases tailored to fit a specific situation (such as giving recommended feeding increases, additional feed increases or maintaining the current feeding pattern to correspond to increases in body weight) can be made more accurately.







Photo

  • Innovatively assessing performance in layers

    Modern CT scan technology is used to evaluate bird body condition.

  • Innovatively assessing performance in layers

Vanessa Kretzschmar-McCluskey and Michael Longley

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