Double Muscling in Cattle: Genes, Husbandry, Carcasses and Meat

Abstract

Simple SummarySelection for an increased meatiness in beef cattle has resulted in double-muscled (DM) animals, owing to the inactivation of the myostatin gene. These animals are characterized by an excellent conformation and an extremely high carcass yield, coinciding with a reduced organ mass. As a consequence, voluntary feed intake is reduced, but feed efficiency is considerably improved, although maintenance requirements are not clearly reduced. DM animals are more susceptible to respiratory disease, stress and dystocia, requiring extra attention for accommodation and welfare. Carcasses of DM animals are very lean, and intramuscular fat content is low. The fatty acid profile is different when compared with non-DM animals, containing less saturated fatty acids. Collagen content of the meat is lower, so that meat from double-muscled animals is mostly more tender. However, meat tenderness, color and juiciness are not always improved. A different metabolism as a consequence of faster glycolytic myofibers can be partly responsible for this phenomenon. DM animals are interesting for the producer and butcher, and beneficial for the consumer, if an appropriate nutrition and accommodation, and adequate slaughter conditions are taken into account.AbstractMolecular biology has enabled the identification of the mechanisms whereby inactive myostatin increases skeletal muscle growth in double-muscled (DM) animals. Myostatin is a secreted growth differentiation factor belonging to the transforming growth factor-β superfamily. Mutations make the myostatin gene inactive, resulting in muscle hypertrophy. The relationship between the different characteristics of DM cattle are defined with possible consequences for livestock husbandry. The extremely high carcass yield of DM animals coincides with a reduction in the size of most vital organs. As a consequence, DM animals may be more susceptible to respiratory disease, urolithiasis, lameness, nutritional stress, heat stress and dystocia, resulting in a lower robustness. Their feed intake capacity is reduced, necessitating a diet with a greater nutrient density. The modified myofiber type is responsible for a lower capillary density, and it induces a more glycolytic metabolism. There are associated changes for the living animal and post-mortem metabolism alterations, requiring appropriate slaughter conditions to maintain a high meat quality. Intramuscular fat content is low, and it is characterized by more unsaturated fatty acids, providing healthier meat for the consumer. It may not always be easy to find a balance between the different disciplines underlying the livestock husbandry of DM animals to realize a good performance and health and meat quality.

Effect of supplementation on the performance of grazing Belgian Blue double-muscled heifers

“…Cabrera Estrada et al (2004) showed that voluntary DM intake of dairy cows increases as the internal water content of roughages decreases. This phenomenon may even be more important in double-muscled animals because of their reduced feed intake capacity (Fiems, 2012). Furthermore, we found that dietary DM content is one of the most important feed characteristics influencing intake of growing double-muscled bulls (Fiems et al, 2002a).…”

“…We previously reported a BW loss during the last months of gestation in BBDM heifers (Fiems and De Brabander, 2009), which can be a consequence of an insufficient feed intake because of the competition for abdominal space. This phenomenon may be more important in double-muscled than in normal-muscled animals because of the reduced organ size of double-muscled animals (Fiems, 2012).…”

“…Especially male calves are predisposed for the development of urolithiasis. Double-muscled animals are even more susceptible because of their reduced weight of the kidneys, the reduced number of urinary tubes and the reduced diameter of the Bowman's capsules (Fiems, 2012).…”

Importance of dam BW change and calf birth weight in double-muscled Belgian Blue cattle and its relationship with parity and calving interval

“…The tendency for increased CI due to a higher BWb/BWpp ratio may be provoked by increased competition for space within the abdomen between the pregnant uterus and the digestive organs (Forbes, 1987). This competition may be more pronounced in doublemuscled than in normal-muscled cows, because of their reduced organ size and feed intake capacity on the one hand, and a higher calf BWb on the other (Fiems, 2012). The importance of BWb/BWpp ratio should not be exaggerated because only a low number of observations were in the classes with a low (n = 20) or a high ratio (n = 9), resulting in an increased CI.…”

“…Reasons for the reduced reproductive performance are related to the double-muscling phenomenon (Fiems, 2012). A fetomaternal disproportion is typical for these animals, resulting in an increased frequency of dystocia (Eriksson et al, 2004).…”