Feed Efficiency

What is feed efficiency?

An often used and easy definition of feed efficiency is body weight gain per unit of feed consumed and the inverse of the commonly used feed conversion ratio (FCR). Feed efficiency is also closely linked with energy metabolism, but due to a number of internal and external factors the correlation with dietary energy concentration is low. It is important to understand feed efficiency as it drives the economic reality of farms, the competitiveness of different animal protein producing industries and the pressure on resources worldwide.

Feed efficiency in broilers

Broiler production is considered feed efficient if compared to other livestock. Feed efficiency is simply expressed as feed conversion ratio (FCR), which represents the ratio between feed intake and body weight. Current commercial broiler chicken strains have an impressive feed efficiency potential which helps the sector being more sustainable and environment friendly.

Feed efficiency in swine

Feed efficiency is generally expressed as the unit of feed consumed per unit of body weight gain. A slight modification is the use of carcass gain instead of body weight gain. Carcass gain is important as it has a direct economic impact as pigs are being sold/paid for on a carcass weight basis. Carcass gain is easily measured at the end of the feeding process when animals are slaughtered, but less easily at the start. It is often estimated and therefore incorrect. Feed efficiency can also be expressed on the basis of energy consumed rather than feed consumed. There is a weakness however in the inaccuracy of estimating the energy content of the feed and the energy taken up by the animal. Feed efficiency can also be expressed in financial terms because the goal of swine production is the use of feed resources most efficiently and effectively.

Feed efficiency in dairy cows

Feed efficiency in dairy cows is based on the relative ability to turn feed into milk. In other words it is the amount of milk produced per amount of dry matter consumed. It is therefore sometimes called dry matter intake efficiency. When calculating feed efficiency it is important to have access to reliable and accurate dry matter intake data. Weighing the feed that was fed should be complemented with weighing the refused feed. Dry matter of feeds and feed components should also be closely monitored as these vary in time. The nutritional content of milk is also of interest when calculating feed efficiency. Energy-Corrected Milk (ECM) is calculated and based on the fat and protein level in the milk. This last parameter allows standardization and comparison between breeds or farms.

Feed efficiency in fish

Feed conversion ratio (FCR) is an effective way for aquacultural producers to measure feed efficiency in their systems. Several factors such as species and production system will cause FCR variation. Values for farmed fish are in general lower than those seen for land-based animals. These low values (e.g. 1.0) can be confusing as they seem to indicate that almost no waste is generated from feeding. When taking into account the moisture level of feed (+/- 10%) and live fish (+/- 75%) it becomes clear that waste is indeed generated. It is therefore interesting to look at the protein efficiency (P.E.). This parameter is calculated by multiplying FCR by the ratio of crude protein percentage in feed to that in the cultured species. Other performance indicators related to feed efficiency are also worthwhile investigating. The viscerosomatic index (VSI), for example, is the ratio of the weight of fish viscera and the animal weight. Viscera are not as valued as fillets and a substantial increase in the mass of viscera is therefore not desirable.

Feed efficiency and Excential Energy Plus

Feed represents up to 70% of the total cost of animal production in modern capital-intensive systems. Within feed, energy is the major cost component in diets for high-performing animals. Energy is the critical dietary constituent that supports maintenance, as well as tissue growth. Knowledge of energy metabolism is essential for understanding feed efficiency. Due to their high energy density, fats and oils are important energy sources in feed formulation. Improving the energy efficiency of these raw materials is of interest from an economic point of view. Nutritional emulsifiers can be used to improve fat digestibility and, thus, improve energy efficiency, which will result in lower feed costs and contribute to more economical and sustainable animal production.

Energy Plus mode of action

An emulsifier is a molecule with a water-soluble (hydrophilic) part and a fat-soluble (lipophilic) part. The combination of these two components in one molecule gives it the unique property that the emulsifier can dissolve both in fat and in water and can aid in mixing these two fractions. In the animal, fat digestion occurs in a few steps. Initially, large fat globules are emulsified in the watery environment of the gut. Normally, fat and water do not mix, and therefore, bile salts assist in this mixing process as natural emulsifiers. Smaller fat droplets are formed and increase the contact surface for the lipase enzyme. This enzyme, produced by the pancreas, breaks down fat. The next step is the formation of micelles. Micelles are water-soluble aggregates of lipid molecules containing both polar and non-polar groups. When micelles come into contact with the micro-villous membrane, they are disrupted, and the fatty acids are absorbed by the lipophilic cell membrane. Bile salts and monoglycerides aid as natural emulsifiers in the formation of micelles. Nevertheless, the capacity of these natural emulsifiers can be a limiting factor for fat digestion. Exogenous nutritional emulsifiers can therefore assist in improving fat digestibility and energy efficiency. Their positive effect will be more pronounced at higher levels of added fat. Even with highly digestible fats (e.g. soybean oil) there is a significant effect.

Effects of emulsifiers on digestibility

Nutritional emulsifiers are known for their effect on energy digestibility, especially in poultry. Increased fat digestion is of main focus, but the digestibility of other nutrients (e.g. crude protein) is also of interest. Several faecal metabolic studies by Orffa provide insight into these effects. Diets in these studies were formulated based on maize, soybean meal, wheat, meat and bone meal in varying concentrations. The oils added included vegetable oils (e.g. soybean oil, mixed vegetable fatty acids) and animal fats (e.g. poultry fat). After an adaptation period, faeces were collected at the end of the metabolic period for a number of consecutive days and analysed. The results show that adding a nutritional emulsifier increases energy, crude fat, dry matter and crude protein digestibility on average by 76 kcal/kg (AMEn), 2.81%, 1.41% and 1.68%, respectively. It is important to note that the increase in energy digestibility depends on the crude fat percentage in the diet.

Improving feed efficiency & saving costs with nutritional emulsifiers

Based on this understanding of energy digestion using nutri­tional emulsifiers, it is possible to implement this strategy in commercial feeds. By supplementing a nutritional emulsifier and implementing its matrix value (e.g. AMEn = 200,000 kcal/ kg) in feed formulation software it is possible to produce en­ergy- reduced and cheaper diets without impacting perfor­mance. Given increasing raw material costs, the effect of the nutritional emulsifier provides an opportunity to reduce the negative impact on feed prices. The return on investment (in energy-reduced diets) ranges from 3:1 to 7:1, depending on the animal species. In addition to the application in energy-reduced diets there is also the possibility to supply a nutri­tional emulsifier on top in the feed. This will result in heavier animals needing less feed. Significant improvements in body weight (BW) and feed conversion ratio (FCR) can be seen. These results also imply improved sustainability. Using less fat in the feed, in energy-reduced diets, and less feed, when supplied on top, results in more sustainable production.

Improving digestibility = saving feed cost and improve performance

A first observation is that a nutritional emulsifier can be used to improve energy, dry matter, crude fat and crude protein di­gestibility, as shown in several faecal metabolic studies (and confirmed in energy-reduced validation tests). A second ob­servation is that based on these improvements in digestibili­ty, the nutritional emulsifier is able to save feed costs and im­prove performance. A third observation is that nutritional emulsifiers contribute to more sustainable feeds.

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