Early life is a critical period in which environmental factors such as nutrition can permanently influence the physiology of organisms later in life. We call this process ‘metabolic programming’ or more recently ‘imprinting’. What can it do for beef cattle?
Metabolic programming refers to the finding that nutrition and management during pregnancy of an animal (or human), and in the neonatal stages, can affect a range of different bodily functions. Some fascinating studies have been done in bees to illustrate how environmental factors can affect outcomes in nature.
Honey bee colonies include thousands of non-reproductive female workers, a few hundred haploid males (called drones) and a single reproductive individual, the queen. Although identical in genetic sequence, in fact they are genetic clones, queen bees and worker bees are entirely different in terms of their behavior, physiology, and appearance. So, how can two clones become different? While all bee larvae are fed royal jelly for the first three days of life, for the queen bees, the key external factor kicks in on day four, when they continue their ingestion of that royal jelly, at a feed rate 10 times higher than worker bees, all the way through their lifespan! While the queens eat large quantities of royal jelly, the worker bees eat a diet of nectar and pollen, in much smaller quantities than the queens do. This one critical difference determines lifespan (queens live to be two or three years old compared to worker bees who are lucky to live two or three months) and size (queen bees are twice the size of worker bees). Bees are indeed an amazing example of how environmental conditions can impact outcomes, to a far greater degree than genetic determinants.
Another well-studied example of ‘programming’ or ‘imprinting’ is presented by individuals who were prenatally exposed to famine during the Dutch hunger winter in 1944-1945. A bitterly cold period and a German food embargo limited rations such that people, including pregnant women, in the Western part of the Netherlands, received as little as 400-800 calories per day. These circumstances created a quasi-experimental, although tragic, human experiment with a well-defined period of severe malnutrition, which allowed epidemiologists to study long-term effects in this population. Individuals exposed to the famine in specific times of gestation have been compared with those born in the same city or region, but before or after the famine, as well as to individuals in the unexposed north and south of the country. Results showed that exposure to famine during pregnancy is associated with an increased risk of obesity, dyslipidemia, type 2 diabetes and schizophrenia of the children born from these women.
The examples from the honey bees and the people suffering from malnutrition in the war highlight the potential of perinatal environmental conditions to modulate epigenetic changes of the genotype. Investigating this principle in production animals can be economically relevant to agricultural producers. Studies have been done in all sorts of animals including rats, sheep and cattle. In dairy calves, studies have shown permanent physiological adaptations arising from early life nutritional interventions such as neonatal colostrum intake. The Trouw Nutrition LifeStart programme is a good example that is focusing on metabolic programming in dairy cattle to increase calf growth, health and - on the longer term milk production, mammary development and reaching a younger breeding age.
For beef farmers specifically, metabolic programming could be very interesting to help them increase meat quality and marbling. This is because the fetal stage is crucial for skeletal muscle development. The number of individual muscle cells (myocytes), or muscle fibers, is established before birth; after that, muscle fiber size can increase (hypertrophy), but no new muscle fibers can be added and muscle growth is therefore limited. Marbling (i.e. intramuscular fat) is crucial for meat palatability, and fetal life is a major stage for generation of intramuscular adipocytes (fat cells), which provides the sites for intramuscular fat accumulation or marbling formation during fattening. Furthermore, development of vital organs has higher priority in nutrient portioning than skeletal muscle, which makes the muscular tissue more susceptible to variations of maternal nutrition during pregnancy.
In other words, a decrease in nutrient availability to the dam during gestation can result in a reduced number of muscle fibers through fetal programming, reducing muscle mass and impacting animal performance4. This was also confirmed by Du et al (2010) saying that nutrient deficiency from early to mid-gestation in ruminant animals reduces muscle fiber number and muscle mass, negatively affecting the growth performance of offspring. However, the effectiveness of nutritional management on altering marbling is easier in the fetal stage when compared to the neonatal stage, early weaning stage, weaning and older stages.
It has recently become clear that nutrition and management strategies during a calf’s life can have long-lasting effects in terms of health and productivity. Metabolic programming is an exciting new era for beef production and can positively affect muscle development and marbling, hence enabling the industry to optimise beef performance and profitability.
