Effects of including olive cake in the diet on performance and rumen function of beef cattle

Abstract

Beef meat in many Mediterranean countries is produced by feeding the animals with high proportions of concentrates and barley straw. In these conditions, feeding costs are high and compromise the profitability of feedlots. Mediterranean countries are also major producers of olive oil, and the processing of this product generates a large quantity of co-products with a high environmental impact. No data appear available in the literature about the effects of including olive by-products in the diet of beef cattle on animal performance. A pen-feeding study was carried out during two growing phases: from 100 to 250 kg (12 weeks), and from 250 to 450 kg (18 weeks). During the first phase 120 steers (mostly Friesian, with an average age of 129 ± 1.1 days) were distributed in six groups of 20 animals each. Two groups were assigned to one of each of the following treatments: a control compound feed based on barley, control with 10% dry matter (DM) substituted by second-extraction pitted and dehydrated olive cake, and control with 20% DM substituted by olive cake. Compound feeds of this first phase were formulated to contain 16–17% crude protein, and were offered ad libitum to the animals. Barley straw was offered as a roughage source. Animals were weighed every 3 weeks, and a digestibility trial was carried out in the middle of the period with four animals per treatment. During the second phase, compound feeds were formulated to contain 14.5–15% crude protein. Rumen fermentation was studied using six steers and the feeds employed in the second growing phase, following a crossover design with two periods. Concentrates were offered once daily allowing at least 10% refusals. Barley straw was also offered as a source of roughage. For each period of the crossover, 15 days were allowed for adaptation to the experimental diets. Samples of rumen liquid were taken at 0 (just before), 4 and 8 h after feeding. The pH, and concentrations of ammonia and volatile fatty acids were determined. Inclusion of up to 20% second-extraction pitted and dehydrated olive cake (DM basis) in the diet did not affect performance of beef steers for the whole growth period. Inclusion of those ingredients in the diet of these animals might be advisable depending on their market price.