Protein: The Building-Blocks of the Body

Protein in the Dog’s Diet

Protein is a critical component of canine nutrition and receives significant attention in the industry. It plays a vital role in growth, repair, and reproduction, providing the necessary building blocks for a healthy body. The origin of dietary protein can be either animal or plant-based, each with its own set of advantages and disadvantages. Proteins are complex molecules found in nature that serve various essential biological functions. While dogs can use dietary protein as an energy source, this chapter will delve into the other crucial roles that protein plays, what dogs require, and sustainability concerns surrounding protein in canine nutrition.

The Importance of Protein

Protein plays a crucial role in our dogs' bodies, serving many forms and functions. Collagen, for example, is a fibrous protein that is widely distributed throughout the body, serving as a structural component of hair, nails, skin, ligaments, tendons, and cartilage. Skeletal muscle, on the other hand, is rich in protein, specifically structural and contractile proteins such as actin and myosin, which are essential for supporting muscle movement. Enzymes and hormones are also proteins, and both groups of substances are critical for normal biological functioning. Additionally, various proteins help to maintain tight homeostatic control, ensuring that the body's systems work safely within specific limits. Proteins also act as transporters, facilitating the movement of substances around the body, and the immune system heavily relies on protein to support normal functioning. The diversity of proteins found in the body is a result of differences in their fundamental structure, which has important nutritional implications.

Protein is essential to support reproduction and growth, body structure and function, repair and it provides a dietary energy source.

The Structure of Protein

Proteins are composed of chains of molecules known as amino acids, which are linked together. The size and complexity of proteins vary, with some consisting of only a few amino acids while others are long and complex chains composed of a mixture of amino acids. The nutritional value of proteins can be influenced by differences in their structure. Large and complex proteins are typically poorly digested and not particularly beneficial in terms of nutrition. Processing and cooking techniques can also affect the shape and structure of proteins, further impacting their nutritional value. It is important to note that animals require amino acids in their diet rather than protein itself. Nitrogen, a crucial element found in protein at approximately 16%, must also be supplied through diet. Therefore, dietary protein provides both amino acids and nitrogen, and nutritionists refer to protein requirements to acknowledge that it supplies both components.

Amino Acids – the Building-Blocks of Proteins

In the field of nutrition, it is widely known that there are 22 amino acids present in proteins. These amino acids are categorized as either 'essential' or 'non-essential'. The former must be obtained through the diet, while the latter can be synthesized by the body without the need for dietary intake (please refer to the table for further details). Although dogs are capable of producing taurine on their own, the significance of taurine in canine diets has recently gained attention in the scientific community, and further research is expected to shed light on its role in dog health.

As protein sources differ in their amino acid composition, it is crucial to formulate diets with a careful consideration of the amino acid profile of each ingredient. Certain food ingredients may be deficient in specific amino acids, and thus, a combination of protein sources is often recommended to ensure a well-balanced supply of dietary amino acids. For instance, a diet that utilizes both animal and plant derived proteins can effectively address amino acid limitations.

The essential (must be supplied in the diet) and non-essential amino acids in canine nutrition

Protein Quality and Nutrition

It is crucial to consider protein quality when selecting food for dogs. Poor-quality protein has low nutritional value and is not easily digested or used efficiently by the body. Additionally, diets containing low-quality protein require more food to meet the dog's protein requirements. If protein digestibility is low, it may cause digestive problems such as flatulence and may be excreted in faeces. On the other hand, high-quality protein with increased digestibility reduces the amount of food needed to meet the dog's needs. Processing protein-rich ingredients can affect the quality of the protein, and there is a fine balance between levels of processing. Research shows that light cooking can increase digestibility for some protein ingredients. However, some commercial dog-foods may have high levels of poor-quality protein with low digestibility. It is crucial to provide highly digestible forms of dietary protein to ensure a good source of protein for dogs. While reducing the digestibility of the diet may be beneficial for weight management, meeting the dog's requirement for essential amino acids is necessary. It is important to note that digestibility values are often based on reference table data and estimated values from prior research, and commercial dog-foods rarely provide information on the quality or digestibility of protein ingredients.

The Biological Value (BV) of Proteins

Certain protein sources may have a lower quality due to their structural composition, which in turn can impact the protein's overall biological value (BV). High-quality dietary protein is characterized by a highly digestible nature and an amino acid profile that is comparable to that of the human body. BV is commonly expressed as a percentage, with 100% BV indicating that the protein is easily digestible and provides amino acids in optimal amounts. Animal-derived proteins, such as eggs and milk, typically have some of the highest BV values, exceeding 75%. In contrast, plant proteins tend to have lower BV values, with rice having a BV of approximately 65%, due to their limited amino acid profiles.

The Practical Impact of Protein Structure in the Dog’s Diet

To ensure optimal nutrition for your canine companion, it is recommended to provide a diet that is rich in highly digestible protein sources. It is important to select protein ingredients that provide all the necessary amino acids, which may require a combination of protein sources. Animal-derived protein sources such as egg, dairy, and skeletal muscle (meat) are considered high-quality, although it should be noted that some dogs may experience issues with egg and dairy ingredients. Plant proteins such as soya, rice, and corn can also be beneficial, but they are limited in some essential amino acids and cannot be used in isolation. When selecting protein sources, it is crucial to choose those with a good biological value (BV) and avoid those that have been extensively or over-processed, as this can negatively impact their nutritional value and require a higher amount to meet your dog's requirements.

The Protein Requirements of Our Dogs

Dogs require a consistent supply of protein to maintain their bodily functions. This is particularly important for growing dogs, who require additional protein to support their development, as well as pregnant and lactating bitches who need protein to produce nutritious milk for their puppies. Active, working, and sporting dogs may require higher levels of dietary protein to support their increased muscle mass and overall physical demands. Additionally, older dogs and those recovering from injury or illness may benefit from increased dietary protein. It is evident that protein plays a crucial role in maintaining the health, structure, and function of our canine companions.

Protein is essential to support the overall health of our dogs, including growth, development and activity.

How Much Dietary Protein Does a Dog Need?

Dogs require protein to support their biological functions and aid in digestion. For healthy adult dogs at maintenance, a minimum protein content of 18 per cent (18g/100g food DMB) is recommended. This percentage increases to 25 per cent (25g/100g food DMB) for young puppies (14 weeks old and younger) and pregnant/lactating bitches. If the diet of a pregnant/lactating bitch is low in carbohydrates, then up to double the recommended amount may be necessary to ensure the health of the dam and her puppies. Young dogs older than 14 weeks require a minimum of 20 per cent protein. It is important to note that these are minimum recommended amounts, assuming that the dietary protein has a minimum digestibility of 80 per cent and contains sufficient levels of essential amino acids.

Protein Deficiency

Protein deficiency in dogs is a rare occurrence, typically only observed in cases of extreme starvation or neglect. Dogs experiencing protein deficiency exhibit symptoms such as being underweight, having poor body condition, skin and coat condition, and increased susceptibility to infections. It is important to note that even if a diet otherwise provides sufficient protein, if it is not provided in a digestible form, it can limit a dog's ability to utilize it. Additionally, in cases where a dog's physiological needs, such as pregnancy or performance, exceed the amounts supplied in the diet, the success and survival of offspring and performance output could be affected. Situations where individual amino acids might be limited, such as restricted ingredient use, can lead to deficiency symptoms for specific amino acids, particularly the essential ones. While most well-formulated diets supply more protein than is needed, it is crucial to be aware of the risks of protein and amino acid deficiency.

Protein Excess

It is important to note that when dogs are provided with excess dietary protein, they have a high level of efficiency in metabolizing and excreting it. However, it is essential to be aware that excess protein may be converted to glycogen or fat, which can have an impact on a dog's weight management. Unlike excess dietary fat or carbohydrate, excess protein in the form of amino acids is not typically stored in the body and is excreted as urea in urine. The strong odor of urine and its ability to damage lawns and plants are generally caused by the compounds produced during protein processing in the body. Studies have shown that the amount of dog urine excreted in areas frequently visited by dog walkers negatively impacts plant life at the side of paths.

A characteristic of dog urine is that it ‘burns’ grass – a result of excreted waste products.

It is important to note that healthy dogs typically have no issues managing the removal of excess protein and its breakdown products. However, certain health conditions can limit this process, and it may be necessary to manage dietary protein levels to support normal function. Dogs with kidney (renal) failure often require this type of management. While it was once believed that high-protein diets caused kidney disease in dogs, we now know that dogs with kidney issues often benefit from diets that supply quality, digestible protein to support impaired kidney function. It is important to restrict levels of dietary protein only when dogs have significantly impaired kidney function and under professional guidance.

While excess dietary protein may not pose a significant concern for the health and wellbeing of our dogs, it is important to consider wider environmental sustainability concerns. This includes the environmental impacts of urea and other nitrogenous waste products that are damaging to the environment. Additionally, the bulk of feed and food costs are linked to their protein content, with animal-derived protein being particularly expensive. As such, feeding excess protein is both environmentally and financially costly.

Protein and Sustainability

Environmental sustainability is a critical concern, and the impact of our dogs' diets on the environment cannot be overlooked. The production of animal-derived protein for human and animal consumption has significant negative environmental consequences. As such, there is a growing need to reduce the demand for animal-derived products and limit the environmental challenges that result. This applies equally to the food we provide our dogs.

Animal-derived protein requires significant resources, including energy, water, and land, to produce. While it is often of high quality and nutritional value, the increasing demand for this type of protein is creating serious environmental challenges. The use of "human or food grade" material as dog food is also creating direct competition for protein entering the human food chain.

Commercial dog food has traditionally used by-products from human food production, such as offal and meat and bone meal, which is a form of sustainability as these by-products would otherwise be waste. These by-products are often not desirable for human consumption, making them valuable for feeding our dogs.

The issue of sustainability extends beyond our dogs' diets, with a global interest in exploring alternative sources of dietary protein for all species. The dog food industry is also shifting towards more sustainable options, with ingredients and products becoming available that are considered favorable steps towards improving sustainability.

Protein Alternatives for Dog Diets

Plant-Based Diets for Dogs

Plant-derived protein is a viable option that is already widely incorporated into many dog diets. It boasts high quality and digestibility, and is a more sustainable alternative to animal protein. It is important to consider the origin of the plant source, as certain protein-producing plants are grown abroad and require transportation, while others are cultivated in areas that have been reclaimed from protected habitats. In terms of nutrition, not all plant proteins offer the necessary amino acids, requiring careful formulation. Additionally, plant products necessitate varying degrees of processing to optimize nutrient availability and mitigate the impact of anti-nutritional factors. However, many plant ingredients offer a wealth of beneficial nutrients, including antioxidants and fiber, and can contribute to better health outcomes for our dogs. Despite a preference for animal-derived ingredients, many dogs will actively seek out and consume plants. Furthermore, plant proteins are a cost-effective option for supplying key nutrients in a diet. Overall, incorporating plant-derived ingredients and protein sources into our dogs’ diets can yield a range of environmental, financial, nutritional, and potentially health-related benefits.

Dogs often self-select plant material, including fruit and vegetables.

Can Dogs be Vegetarian or Vegan?

Many pet caregivers are considering flexitarian, vegetarian, or vegan diets for their dogs due to various reasons such as personal lifestyle choices, environmental concerns, or dietary intolerances. While it is possible to provide a nutritionally balanced vegan or vegetarian diet for dogs, it requires professional guidance and supplementation in most cases. Fortunately, there are now commercially available diets that cater to this evolving need in canine nutrition, although careful consideration should be given to their formulation. Unlike domestic cats, dogs can thrive on diets with little to no animal ingredients. However, the topic of whether dogs would choose a vegetarian or vegan diet is beyond the scope of this book.

Insect-Based Dog Food

Insects offer a sustainable and viable source of protein for animal diets. It is worth noting that wild canids frequently consume insects as part of their regular diet, and their nutritional composition is highly favourable. The production of insects on a commercial scale for animal diets is associated with sustainability benefits over conventional animal-production systems. Insects provide a high-quality and easily digestible protein source, with an excellent profile of constituent amino acids. Proper processing of insects can minimize the impact of their tough external 'skeletons' and other components that would otherwise limit their usefulness as ingredients. Research indicates that insect meals and flours are well-received by dogs and can serve as useful and sustainable ingredients in dog food and treats. Insect ingredients may also be beneficial for dogs with allergies and intolerances to more traditional ingredients. It is likely that insects, such as the black soldier fly, will increasingly become mainstream ingredient options for both commercially produced and home-prepared dog food.

Insects as a protein source are gaining interest in the animal nutrition world, including as dog-food ingredients.

Summary

• Protein provides the building blocks for a dog’s body structure and function.
• Dogs can use protein as a source of energy, but excess protein is excreted and not stored.
• The nutritional value of protein depends on its quality, digestibility, and amino acid composition.
• Active, reproducing, and growing dogs may benefit from diets high in quality, digestible protein.
• Alternative sources of dietary protein are attracting increased interest to meet sustainability, financial, and health needs.