Citrus pulp as an innovative feed ingredient in ruminant nutrition : a review

Abstract EN

Over the last fifty years, the Egyptian population increased from approximately 34 million in 1969 to more than 101 millions in November, 2019 based on World meters survey of the latest United Nations data (World meters 2019).

As a result of this substantial growth, demand on food supply should have been more than the double.

This means that agricultural scientists must work vigorously to increase food production, both plant and animal, to meet the increased needs of future generations.

In Egypt, there is a serious gap between available and required amounts of animal feed supplies, which have been calculated to be 4.2 million tons of total digestible nutrients (TDN) per year (Shoukry 2019).

The shortage in concentrate feed resources represents a major constraint to animal production in Egypt.

Continued rise in prices of corn grains that are locally produced in Egypt, or that imported from abroad reflected on increasing the price of concentrate feed mixture (CFM) because corn grains represent a high percentage (approximately 50±10%) of the CFM of ruminants.

Egypt's import of corn grains increased from 64000 tons in 1969 to 10 million tons during 2018 / 2019 (USDA 2019), representing approximately 156 fold increase during the last 50 years.

The importation of the yellow corn grains annually depletes a huge amount of foreign currency (estimated about 2 Billion dollar/year in 2018).

A recent study (Shoukry 2019) showed that more than 70 % of poultry and fish nutritional requirement are imported.

Those reasons led the specialists in animal nutrition to search for alternative feedstuffs that may partially or completely replace traditional feed ingredients as a source of energy in animal rations.

Citrus by-products may play an important role in solving this critical issue.

There are many forms of citrus by-products feedstuffs fed to ruminants (Bampidis and Robinson 2006).

The present review will be focused on fresh, silage and dried orange pulp because these are the most available forms of citrus by products in Egypt.

The fresh citrus pulp (FCP) is the raw by-product of citrus juice industry, which includes all contents of the citrus fruit, except the expressed citrus juice (Hutton 1987).

It is palatable for the animals, low price compared to other feed materials that have the same nutritional value and provides good digestible nutrients.

Also, it is rich in vitamin C and antioxidants, which is positively reflected in the health and productivity of the animal.

However, the disadvantages of FCP are bulkiness, spoils quickly and is fly-breeding nuisance if allowed to rot, and provides an unbalanced Ca : P ratio.

Because of its high moisture content (76-87 %), usefulness of citrus pulp can be enhanced by ensiling or drying it and converting it to dry citrus pulp (Bakr 2015).

Ensiling citrus pulp is a good method to make it available for year-round feeding (Fuller, 2004).

The silage has a pleasant odor and is readily acceptable by cattle.

Citrus pulp enhances overall silage quantity and quality (more sugars, more acidic bacteria, lower pH) and reduces the need for acid additives (Crawshaw, 2004).

Fresh citrus pulp silage can be preserved in good condition without an additive (Revuelta Llano et al., 2008).

Moreover, citrus pulp ensiled without additives gives better results in energy conversion efficiency measured by production of volatile fatty acids (Itavo et al., 2000).

The dried citrus pulp is a by-product produced after extraction of the juice from citrus fruits and drying of the residues.

It is classified as an energy concentrate by-product feed.

The DCP was used at different percentages of substitution of grains (corn, barley, and wheat), beet pulp, and sometimes as an antioxidant feed supplementation.