INCLUSION OF OLIVE CAKE IN FATTENING PIG FEEDS: EFFECTS ON AMMONIA AND METHANE EMISSIONS

FERRER, P.¹, CERISUELO, A.², GARCÍA-REBOLLAR, P. ³, DE BLAS, C. ³, ESTELLÉS, F.¹, CALVET, S.¹

1 Universitat Politècnica de València, Institute of Animal Science and Technique. Camino de Vera s.n. 46022 Valencia, Spain

2 Centro de Investigación y Tecnología Animal, Instituto Valenciano de Investigaciones Agrarias, Pol. La Esperanza 100, 12400 Segorbe,Castellón, Spain

3 Departamento de Producción Agraria, Universidad Politécnica de Madrid, E.T.S. Ingenieros Agrónomos de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain

ABSTRACT: Agro-industrial by-products used in animal feed constitute an interesting alternative to improve the sustainability of swine production. With this aim, a study of the inclusion of crude olive cake in diets for growing pigs, and its effects on slurry composition and, ammonia (NH₃) and methane (CH₄) emission was performed using 30 pigs of 76.1 ± 4.2 kg live weight. Five diets were formulated: a basal diet and four experimental diets including two levels (10% and 20%) of crude olive cake (COC) and partially defatted olive cake (PDOC).

Total faeces and urine produced were collected for slurry chemical analysis and for the determination of in vitro NH₃ and CH₄ potential emission using metabolic cages. Results showed that substituting a conventional feed by 10 and 20% of olive cake reduced ammonium content and pH in the slurry and therefore the associated NH3 emission.

However, the potential CH4 emission expressed per L of slurry and day were higher in those animals fed the olive cake diets.

Keywords: olive cake, Slurry, Swine, NH3, CH4.

INTRODUCTION: Nutritional management is acknowledged as a key strategy to mitigate gaseous emissions. In this regard, the use of agro-industrial by-products in animal feed can have a positive environmental impact because of enhanced nutrient recycling, thus increasing the profitability and sustainability of the livestock sector (Kasapidou et al., 2015).

Benefits may arise from the reduction of environmental costs linked with the replacement of raw materials, but the corresponding changes in slurry properties and their emissions must be evaluated.

Olive cake is among the most important agro-industrial by-products in Mediterranean areas such as Southern and East Spain. It is highly available throughout most of the year and can be dehydrated, which increases its interest in monogastric species such as pigs. With respect to the composition and nutritional value, it depends from the oil extraction intensity. Its use can be nutritionally acceptable to pigs and is expected to be beneficial in terms of digestive physiology. However, there is lack of knowledge on slurry composition and gaseous emission associated with the inclusion of olive cake in animal feed.

In this context, an experiment was conducted to determine the nutritional value of two types of olive cake which varied in the extraction degree: crude (COC) and partially defatted (PDOC), focussing on the effects of its inclusion on slurry composition and ammonia (NH3) and methane (CH4) emissions.

1. MATERIAL AND METHODS: Five diets were tested, considering one basal diet, two diets substituting 10 and 20% of the mass by COC, and two diets substituting 10 and 20% by

Mitigation strategies

PDOC, respectively. Thirty fattening pigs of 76.1±4.2 kg initial body weight were used in the experiment (6 animals per treatment). After an adaptation period of 14 days, feed intake was recorded and urine and faeces produced were collected in metabolism cages during 4 days for a digestibility assay. Finally, faeces and urine were collected for 3 days to generate reconstituted slurry for the gas emission assay. Representative samples were taken for chemical analysis. Biochemical methane potential (B₀) and NH₃ emissions were quantified in vitro according to Angelidaki et al. (2009) and Antezana et al. (2016), respectively. Data was analysed in a one-factor analysis of variance as a completely randomized design with type of diet as main effect by using PROC GLM of SAS (2008). The effects of diet were analysed as a factorial arrangement by using orthogonal contrasts with source and level of inclusion of OP as main factors.

2. RESULTS AND DISCUSSION: Table 1 shows the effects of including different levels of COC and PDOC in the diet on slurry (faeces + urine) excretion, initial characteristics and derived NH3 emissions and B0.

Slurry excretion and composition parameters changed with the inclusion of olive cake.

Slurries from animals fed olive cake diets showed higher excretion rates, dry matter (DM) and organic matter (OM) contents. On the contrary, lower pH values and nitrogen content were found with the inclusion of COC and PDOC, with a linear effect of olive cake inclusion level (p<0.05) in all the parameters studied. No statistical differences were found in B0 values of slurries obtained from different diets expressed in mL of CH4 per g of OM. However, as OM in slurries increased with the inclusion of olive cake, higher CH4 emissions were estimated (p<0.05) with the inclusion of olive cake when expressed in L of CH4 per animal and day. NH3 emissions decreased significantly with increasing proportions of olive cake in the feed. Total ammonium nitrogen (TAN) of slurry decreased with COC and PDOC inclusion.

A significant reduction of urine and slurry pH was also detected with increasing inclusion levels of olive cake. The inclusion of both olive cakes at 20% reduced slurry pH by one unit in the COC treatment and 0.8 units in the PDOC treatment. The fibre content of olive cake may probably originate these differences. Effects on TAN and pH were the major forces to reduce NH3 emissions expressed per L of slurry, as evidenced by multiple regression (R² = 0.86).

Table 1. Effects of including different levels of crude olive cake (COC) and partially defatted olive cake (PDOC) in the diet on slurry (faeces + urine) excretion, initial characteristics and derived NH₃ emissions and biochemical

methane potential (B0).

110_COC = 100g/kg crude olive cake; 20_COC = 200g/kg crude olive cake; 10_PDOC = 100g/kg partially defatted olive cake; 20_PDOC = 200g/kg partially defatted olive cake.

a,b,c,d Different letters in the same row indicate averages statistically different (P < 0.05).

2Standard error of means (n = 6).

3. CONCLUSION: In summary, substituting a conventional feed by 10 and 20% of olive cake reduced ammonium content and pH in the slurry and therefore the associated NH3

emissions, being an interesting option in order to abate ammonia emissions from pig production.

Acknowledgements. This research was supported by the Spanish Ministry of Economy and Competitiveness (research project AGL2014-56653-C3-2-R).

REFERENCES:

Angelidaki I., Alves M., Bolzonella D., Borzacconi L., Campos J. L., Guwy a. J., Van Lier J. B., 2009. Defining the biomethane potential (BMP) of solid organic wastes and energy crops:

A proposed protocol for batch assays. Water Sci Technol., 59, 927–934.

Antezana W., Ferrer P., Cambra-López M., Estellés F., Calvet, S., 2016. Ammonia Emission Quantification from Pig Slurry Using Acid Wet Traps: Evaluation and Optimization of Measurement Frequency. Water Air Soil Poll., 227, 277.

Kasapidou, E. Sossidou, E., Mitlianga, P., 2015. Fruit and Vegetable Co-Products as Functional Feed Ingredients in Farm Animal Nutrition for Improved Product Quality. Agriculture, 5, 1020–1034.

SAS Institute, 2008. SAS/STAT® User’s guide SAS Institute Inc., Cary, NC

Mitigation strategies

ACHIEVING A GREATER REDUCTION OF AIRBORNE EMISSIONS FROM SWINE BUILDINGS BY