Evaluating pectoralis muscle development and bone health using non-invasive methods

• Fractures: often resulting from collision with housing equipment, such as perches, leading to partial or large fractures with bone displacement. They are strongly associated with pain and a drop in egg production.
• Deviations: tend to develop gradually as a result of constant pressure on the keel bone due to extended perching behaviour and/or osteoporosis.

Figure 1 - Examples of keel bone deviation and keel bone fracture (^©Lallemand).

Ensuring good skeletal development and managing Ca metabolism during the laying period are thus crucial to sustain both hen welfare and economic performance.

Furthermore, muscle development and protein retention are key in maintaining the persistency of the laying curve. Pectoralis muscle development and keel bone integrity are therefore key predictors of laying performance and persistency.

• Lallemand developed a set of complementary methods based on both ultrasonography and cost-effective, easy-to-use tools to investigate pectoralis muscle development and keel bone integrity in non-invasive ways.

This new approach allows to objectively demonstrate the benefits of a probiotic, Pediococcus acidilactici CNCM I-4622 (BACTOCELL), on these parameters while supporting welfare.

The use of this probiotic dedicated to monogastric animals has been extensively documented for the last 25 years, with more than 100 scientific publications. This lactic acid bacteria was specifically selected for its ability to exclusively produce high levels of L-lactic acid (a source of energy for the birds).

ASSESSING PECTORALIS MUSCLE DEVELOPMENT

Pectoralis muscle palpation is generally recommended by genetic guidelines to predict good laying curve persistency: the better the pectoralis muscle scoring, the more the layer will be able to sustain high egg production.

Although easy, hand palpation is highly subjective and operator dependent, based on their expertise and training level. A standardized protocol using an ultrasonography device was developed to record pectoralis muscle thickness of birds, directly on farm (Figures 2 and 3).

Figure 2. Application of ultrasonography device on top of the keel bone, perpendicular to the (major and minor) pectoralis muscle, to precisely measure its thickness, and to assess keel bone integrity and morphology by sliding the device along the length of the bone to get a complete picture (^©Lallemand).

Figure 3. Pectoralis muscle thickness in a well-muscled hen (left: thicker) and in a poorly muscular hen (right: thinner) obtained by ultrasonography. The keel bone is barely detected by palpation in well-muscled hens (left) whereas it is protruding in poorly muscular hens (right) (^©Lallemand).

However, some limits have been highlighted relating to the use of the ultrasonography device. Alternative and complementary methodologies have thus been investigated by Lallemand to predict pectoralis muscle thickness of both pullets and layers based on easy-to-collect field data. A prediction equation was established using the following indicators:

• live body weight, in grams;
• fleshing evaluation (angle between keel bone and breast muscle), in degrees;
• metatarsus length, in millimeters;
• tibia diameter, in millimeters.

These non-invasive methods can be used to validate the beneficial effect of Pediococcus acidilactici CNCM I-4622 (BACTOCELL) on muscle development. Consistent results showing a significant increase of pectoralis muscle thickness were observed when supplementing different poultry species (pullets, layers, broilers) with BACTOCELL over different periods of time (Table 1).

Table 1 - Improvement of pectoralis muscle development following BACTOCELL supplementation in different poultry trials.

ASSESSING KEEL BONE INTEGRITY

Hand palpation can display a poor diagnostic accuracy in detecting keel bone fractures, meaning invasive methods, like necropsy, must be applied in conjunction for reliable assessment.

A standardized protocol using ultrasonography was developed by Lallemand to assess keel bone integrity by investigating deviations and/or fractures presence and severity, directly on farm (Figure 4). Ultrasonography appears to be thus a valuable complementary tool which can also be confirmed by X-ray observation.

Figure 4. Keel bone fractures: light (a), severe (b and c) and a bone callus in the early stages of formation (d) observed with ultrasonography (^©Lallemand).

As highlighted by different academic and field trials, laying hens supplemented with BACTOCELL did display a significant reduction of keel bone deviation or fracture. In a recent large scale trial, layers supplemented with BACTOCELL showed fewer keel bone deviations (10% vs 20% in control group) and keel bone fractures (40% vs 55% in control group) at the late stage of the laying cycle.

Moreover, more intact keel bones were observed in the BACTOCELL group (50% vs 15% in control group). Some laying hens presented both keel bone deviation and fracture (10%), but all of them were in the control group. When some keel bone deviations and/or fractures were observed, their severity was reduced in the probiotic-supplemented group (Figure 5).

These recent data support previous observations of greater bone resistance and more efficient mineralization process (Ca, P, osteocalcin and calcitriol blood concentrations) associated with improved keel bone morphology and integrity in hens supplemented with BACTOCELL.

Figure 5. Evolution of keel bone integrity in layers supplemented with BACTOCELL throughout the laying cycle (field trial in a commercial farm of 40,000 hens, 2024).

Using non-invasive methods to evaluate pectoralis muscle development and bone mineralization can prevent invasive measurements involving the death of birds, especially in the current context of extending hen life cycles for economic, societal and environmental concerns.

Both ultrasonography and new cost-effective methods based on easy-to-measure indicators can be considered as valuable diagnostic tools to predict laying performance and egg quality while supporting animal welfare.

These methods can be included in protocols routinely used to objectively demonstrate the benefits of the probiotic Pediococcus acidilactici CNCM I-4622 (BACTOCELL) on body composition, muscle and bone development, proving BACTOCELL to be a valuable nutritional strategy to safeguard laying performance and egg quality (Figure 6).