The use of crop residue in confined cattle feed reduces the water footprint of cattle farming. That was the conclusion from research carried out by Embrapa Southeast Livestock, which assessed how the use of such co-products influences water consumption in beef production. They tested two different diets: a conventional one and one with the full replacement by co-products. The research confirmed that the animal diet impacts water consumption. According to the Embrapa researcher Julio Palhares, the exchange reduced the figure for the total water footprint. While in the conventional diet the footprint was 1,688 liters per kilo of beef, by feeding the animals with co-products it amounted to 1,655 liters, a reduction of about 2%. Besides promoting better water efficiency, the alternative food use maintained animal performance. For the animal scientist Marcela Morelli, who was responsible for the research alongside Palhares, suitable nutritional management is relevant since the diet represents between 60% and 80% of the property's production costs. However, replacing conventional ingredients with crop residue should observe commercial availability, nutritional quality, proximity and supply. Knowing beef's water footprint, according to the Embrapa researcher, enables the identification of critical points in the water use in cattle farming and the proposal of management to give the product higher efficiency. From agricultural waste to cattle feed The search for strategies to increase confined cattle production with economic viability has increased the participation of co-products in animal diets. Studies demonstrate that the use of crop residue maintains weight gains and carcass characteristics. Moreover, it is important to reduce the dependence on products that could be human food, since the bovines are capable of transforming ingredients that are not useful for human diets into products with high nutritional value. Much of the residue generated by agro-industrial activities can be used in the animal diet. However, economic viability depends on supply and the proximity with producing regions. “The co-products are recommended for farmers that can acquire them, considering the nutritional value and economic viability, as well as availability in the region; otherwise it will not be advantageous in productive and economic terms. Further studies to assess the environmental viability of the use of the coproducts are also necessary”, Palhares explains. The inclusion of co-products in Brazilian confinement diets is significant. One can highlight the following co-products that work as substitutes: cotton seeds, citric pulp, and shells or rinds of several products (soybean, peanuts, etc.). Experiment The research was carried out in the confinement section of the Canchim Farm, at Embrapa Southeastern Livestock's headquarters. They divided 52 Nelore males into two groups. The two interventions evaluated were: conventional diet, composed by corn silage, corn concentrate and soybean meal, and a diet with co-products, based on corn silage and a concentrate made of full fat corn germ, citric pulp and peanut shells. During the confinement, the feed was balanced and adjusted to the animals' weight gain requirements according to their stages of adaptation, growth and termination. TO calculate the water footprint, the Water Footprint Network method was used during a confinement cycle of 100 days. The calculation considered the blue, green and gray waters (see picture below) consumed in the production system and at slaughter. Figures The sum of the water green and blue footprints from confinement offered a figure of 1,695 liters per kilo of beef for the conventional diet and 1,545 liters for the alternative one. The green water footprint represented 99,5% of the total amount for the two diets. The formulation with co-products resulted in a positive impact with reduced total water footprint. On the other hand, the blue water footprint was 28,5% higher that the conventional one. By adding the value of water footprint to the process of slaughter, the footprints total 1,802 liters per kilo of beef for the conventional diet, and 1,769 liters for the one with co-products, representing an extra of 6% in the two footprints. Slaughter figures did not differ from one diet to the other, as the process of slaughter for the two groups was the same. When the water footprint at slaughter is added, the green water figures started to represent around 92% for the diets. 33 liters less per kilo of meat The blue water footprint for the conventional group was seven liters per kilo of beef, and for the group with a diet with co-products, nine liters. Thus, to produce one kilogram of product, the animals fed with alternative ingredients consumed two additional liters per kilo of beef than the ones fed with conventional products. Water footprint The water footprint is composed by direct components (water ingested by the cattle) and indirect components (water used in grain production). The green water represents the water consumed in the production of the plant crops and the one contained in such products. The blue water is extracted from surface and underground sources and is used in crop irrigation, the animals' direct consumption, services in the farm, and in animal slaughter and product processing. The gray water is the volume required to assimilate the load of pollutants based on natural concentrations and legal standards. The average consumption of the group with the conventional diet was 19 liters/head/day, and the one with the diet with co-products, 23 liters. “The blue water consumption was higher in the alternative diet because the animals ingested a greater amount of dry matter, with lower water content, which determined higher water consumption at the through”, explains Palhares. According to Marcela, most studies related to the use of co-products in cattle feed evaluate the partial substitution of some conventional ingredient. The co-product diet promoted a reduction in total water footprint of 33 liters per kilo of meat in comparison with the conventional one. “The results demonstrate that it is possible to formulate diets with co-products as full replacements of conventional ingredients and have positive impacts in improving water efficiency while still maintaining animal performance levels. Another positive point is the conversion of a co-product into a noble product, beef”, she underscores. Translation: Mariana Medeiros