Crude corn oil as dietary fat source for dogs

Accepted Manuscript Title: Crude corn oil as dietary fat source for dogs Authors: T.T. Sabchuk, D.C. Lima, T.S. Bastos, S.G. Oliveira, A.P. F´elix, A. Maiorka PII: DOI: Reference:

S0377-8401(18)30316-X https://doi.org/10.1016/j.anifeedsci.2018.11.014 ANIFEE 14109

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Received date: Revised date: Accepted date:

6 March 2018 9 October 2018 20 November 2018

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Please cite this article as: Sabchuk TT, Lima DC, Bastos TS, Oliveira SG, F´elix AP, Maiorka A, Crude corn oil as dietary fat source for dogs, Animal Feed Science and Technology (2018), https://doi.org/10.1016/j.anifeedsci.2018.11.014 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Crude corn oil as dietary fat source for dogs

T.T. Sabchuka, D.C. Limaa, T.S. Bastosa, S.G. Oliveiraa, A.P. Félixa, A. Maiorkaa

Department of Animal Science, Federal University of Paraná, Curitiba, PR, Brazil

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*Corresponding author. Tel.: +55 41 3353-6492; fax: + 55 41 3252-4149. E-mail address:[email protected] (S.G. Oliveira).

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Highlights

Digestibility of the corn oil diet was similar with the poultry fat diet.

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The corn oil digestibility was high as the poultry fat digestibility.

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The inclusion of corn oil did not compromise palatability.

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Crude corn oil may be considered adequate fat source for dog foods.

Abstract

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The objective of this study was to evaluate the effects the inclusion of corn oil on the

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coefficients of total tract apparent digestibility (CTTAD) of dietary nutrients and palatability of dog foods, and on the faecal characteristics of dogs. Three experiments were carried out. In

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Experiment 1, the effects of diets with increasing CO concentrations (40, 80, and 120 g/kg) in replacement of poultry offal fat (POF) in the basal diet on the CTTAD of dietary nutrients, dietary metabolizable energy (ME) content and on dogs’ faecal characteristics were analysed in eight adult dogs distributed in a double Latin-square design (4 x 4). Experiment 2 evaluated the CTTAD of the nutrients in diets containing either corn or poultry offal fat used as fat

sources in replacement of 92% of a basal diet containing beef tallow in nine adult dogs applying a randomized experimental design. Experiment 3 compared the palatability of diets containing either corn oil or poultry offal meal and coated or not with a palatant by first choice test and intake ratio (IR) calculation. Dietary CTTAD and ME content, and faecal

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characteristics were not different (P>0.05) among diets with increasing CO concentrations or compared with the diet with POF. No differences (P>0.05) in the CTTAD of acid-hydrolysis

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ether extract (AHEE) were detected between diets containing CO (98.62%) or POF (97.94%). The inclusion of CO in did not influence diet palatability (P>0.05). These results indicate that

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corn oil may be utilized as fat source in dog foods.

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Abbreviations: CTTAD, coefficient of total tract apparent digestibility; CD, control diet; GE, gross energy; ME, metabolizable energy; AHEE, acid-hydrolysis ether extract; NFE, nitrogenfree extract; CF, crude fibre; DM, dry matter; fDM, faecal dry matter; CO, organic matter; CO, corn oil; CDP, diet with poultry offal fat and palatant; CDNP, diet with poultry offal fat and no palatant; COP, diet with corn oil and palatant; CONP, diet with corn oil and no palatant; POF, poultry offal fat; FO, faecal output; BW, body weight; IR, intake ratio.

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1. Introduction

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Keywords: corn co-products, digestibility, dog nutrition, faecal characteristics, palatability.

In animal nutrition, including dog and cat nutrition, there is a great demand for

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feedstuffs that present good manufacturing properties, sufficient availability in the market, and that supply adequate nutrient levels. Therefore, novel ingredients for pet foods should be

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evaluated for their nutrient utilization and possible effects on animals in order to allow their safe and efficient inclusion. This study focuses on corn oil as a possible fat source for dog foods. Fats are included in dog foods to supply energy and fat-soluble vitamins, in addition of

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improving diet palatability and texture (Ahlstrøm et al., 2004). Plant or animal fats, or a combination of both, can be added to dog foods. Their choice depends on several factors, such as their essential fatty acid content, melting point, effect on palatability, susceptibility to oxidation, and market price (Ahlstrøm et al., 2004).

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Corn is the second largest crop produced in Brazil after soybeans (Conab, 2016), and its co-products include gluten, germ, and oil, which represents 3.1 to 5.7% of total corn grain

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weight. Co-products or by-products are secondary products from any primary food product source (AAFCO, 2012). According to Shurson et al. (2015) corn oil has higher stability compared with other oil and fat feed sources due to its high polyunsaturated fatty acid (PUFA)

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content, presenting the following fatty acid profile: linoleic acid (48.02%), oleic acid

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(34.68%), palmitic acid (12.5%), and stearic acid (2.11%).

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Considering its high availability, corn oil could be an alternative to poultry offal fat,

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which is the typical fat source added to dog diets in Brazil, according to the Brazilian Association of Pet Food Manufacturers (ANFALPET, 2011). However, its digestibility,

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palatability, and possible effects on dog health need to be evaluated before it can be safely

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included in dog foods. Moreover, the evaluation of its digestibility would allow determining

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the actual availability of its nutrients and, therefore, to accurately calculate its concentration when formulating diets (Carciofi, 2008). However, to the best of our knowledge, no studies on

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the digestibility of corn oil as a fat source for dog foods were published in literature, only on

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the digestibility of protein sources (Kawauchi et al., 2011; Félix et al., 2013). The objective of this study was to evaluate the digestibility and palatability of diets

containing increasing corn oil concentrations and their effects on the faecal characteristics of adult dogs.

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2.

Materials and methods The experiments were approved by the Committee of Ethics on Animal Use of the

sector of Agrarian Sciences of the Federal University of Paraná, Curitiba, PR, Brazil, under

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protocol n. 037/2014.

2.1. Corn oil processing

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The crude corn oil evaluated in this study was obtained from the company Cargill, which uses a proprietary process for its production. The oil was obtained by mechanical pressing technology, which uses only temperature and pressure for oil extraction, without the

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use of chemical solvents. Briefly, the corn oil is mechanically extracted by double passage of

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raw corn grains through four screw presses. The process consists of passing the corn grain,

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using high pressure and temperature, through a vertical axis with a double screw, which

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surrounding barrel has slots that allows the passage of the oil. The remaining cake is then passed through a horizontal double screw under high pressure and temperature to remove the

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oil remaining in the grain. The collected oil is placed in separation tank, where the solid

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particles (germ fines) are allowed to decant and are rerouted to extractor presses for further

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oil extraction. The remaining oil is then cooled to room temperature to prevent losses caused by heat oxidation, which increases oil acidity. The oil is then stored in 75,000-L stainless-steel

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tanks.

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2.2. Experiment 1: Digestibility of diets containing increasing crude corn oil concentrations and their effects on dogs’ faecal characteristics

2.2.1 Objective The objective of this experiment was to determine the digestibility of diets with

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increasing corn oil concentrations and their effects on the faecal characteristics of dogs.

2.2.2. Diets A complete basal diet was formulated to meet the nutritional requirements of adult

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dogs according to the NRC (2006).After extrusion, the basal diet (at 100-110°C) was dried in a triple-deck dryer, after which it was sprayed with poultry offal oil or corn oil, coated with a

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palatant (chicken liver hydrolysate), and cooled. The four corn oil inclusion concentrations (0, 40, 80, and 120 g/kg) evaluated were added to the diets were added to the diets after extrusion by coating in replacement of poultry offal oil.

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The ingredients and analysed and calculated chemical composition of the experimental

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diets are in Table 1.

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2.2.3. Animals and facilities

Eight adult beagles (four males and four females), with 12.63±0.98 kg body weight

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and 6±0.2 years old, were studied. All dogs were submitted to clinical and physical

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examination and were previously vaccinated and de-wormed. Dogs were individually housed

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in concrete kennels (5-m long x 2-m wide) with shelter.

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2.2.4. Digestibility assay The digestibility assay was performed using the total faecal collection method. Faeces

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were collected for 10 days divided in two periods: five days of adaptation, followed by five days of total faecal collection, according to the recommendations of the Association of American Feed Control Officials (AAFCO, 2003). Dogs were fed twice daily (08:00 and 16:00 h) in sufficient amount to supply their

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metabolizable energy (ME) requirements, according to the following equation (NRC, 2006): ME (MJ/d) = 0.54 ×BW0.75, where BW is body weight. Water was offered ad libitum. Faeces were collected at least twice daily, weighed, identified per period and per dog, and stored in a freezer at -14 °C. At the end of each period, faeces were thawed,

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homogenized, and dried in a forced-ventilation oven at 55°C for 48 hours until constant

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weight.

2.2.5. Faecal parameters

The following faecal parameters were evaluated: total dry matter content (fDM),

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faecal output (g faeces/g DM intake/5 d), faecal score, ammonia content, and pH.

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Faecal score was evaluated always by the same researchers, using the following 1-5

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scale:1 = watery faeces (can be poured from the container); 2 = soft and unshaped stools; 3 =

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soft, shaped, and moist stools; 4 = well-shaped and uniform stools; 5 = well-shaped, hard, and dry stools, as proposed by Carciofi et al. (2009).

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Faecal ammonia content was determined according to Brito et al. (2010). A 5-g sample

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of faeces collected within 15 min of defecation was incubated for 1 h in a 500-mL volumetric

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flask containing 250 mL distilled water, to which three drops of octyl alcohol (1-octanol) and 2 g of magnesium oxide were added. The solution was distilled in a Macro-Kjeldahl apparatus

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(Vapodest 200, Gerhardt, Koenigswinter, Germany), and recovered in a beaker containing 50 mL boric acid. Ammonia was then titrated using 0.1 N sulfuric acid. Faecal ammonia content

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was calculated according to the equation: ammonia-N (g/kg) = N × correction factor × 17 × [(volume of acid in the tested sample – volume of acid in blank sample)/sample weight in grams]. Faecal ammonia content was corrected for faecal DM content (g). Faecal pH was measured in 2.0 g of faeces collected within 15 min after defecation

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and diluted in 20 mL distilled water using a digital pH meter (331, Politeste Instrumentos de Teste Ltda, São Paulo, SP, Brazil).

2.2.6. Chemical analyses

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Corn oil was analysed for acidity index (Method 325/IV), iodine index (Method 329/IV), peroxide index (Method 326/IV), and saponification index (Method 328/IV)

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according to Instituto Adolfo Lutz (2008), and unsaponifiable matter content (Method 35) according to the Brazilian Compendium of Animal Feeding (2009). The results are presented in Table 2. Corn oil fatty acid profile was determined in a capillary gas chromatograph,

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according to the American Oil Chemists’ Society (AOCS, 2004), and it is shown in Table 3.

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Dry faeces and the diets were ground to 1-mm particle size, and analysed for DM at

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105C, crude protein (CP, method 954.01), crude fibre (CF, method 962.10), acid-hydrolysis

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ether extract (AHEE, method 954.02), and ash (Ash, method 942.05) contents, according to the Association of Official Analytical Chemists (AOAC, 1995). Gross energy (GE) content

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was determined in a bomb calorimeter (Parr Instrument Co. model 1261, Moline, IL, USA).

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Original faecal dry matter content was calculated as: dry matter at 55oC (DM55) x dry matter

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at 105oC (DM105)/100.

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2.2.7. Calculations and statistical analyses Based on the laboratory results obtained, the coefficients of total tract apparent

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digestibility (CTTAD, g/kg) of DM, CP, AHEE, GE, and ME content of the experimental diets were calculated as: CTTAD (%) = [(g of nutrient intake – g of nutrient excretion)/g of nutrient intake] x 100 Gross energy content was estimated according to the equation (AAFCO, 2003):

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ME (MJ/g) = {kJ/g GE intake – kJ/g faecal GE - [(g CP intake – g faecal CP) x (1.25 kg/g)]}/g feed intake. The animals were distributed in a 4 x 4 double Latin square design (treatments x periods).

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Data were tested for normality (Shapiro-Wilk test) and for homoscedasticity (Bartlett’s test), and when these assumptions were accepted, data were submitted to analysis of variance

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using the GLM procedure of SAS statistical package (SAS Inst. Inc., Cary, NC). Corn oil concentrations responses were submitted to analysis of regression. A 5% probability level was assumed in all statistical tests. After checking data orthogonality, the following orthogonal

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contrasts were tested:control diet (CD) vs. average of the diets containing corn oil (COG; 40,

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80,and 120 g CO/kg), and control diet (CD) vs. diet with 120 g CO/kg (120CO).Faecal score

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results were submitted to the non-parametric Kruskal-Wallis test at 5% probability level.

2.3. Experiment 2: Corn oil digestibility

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2.3.1. Objective

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The objective of this experiment was to determine the digestibility of corn oil and

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poultry offal fat as fat sources.

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2.3.2 Diets

A control diet (CD) was formulated to meet the dog’s nutritional requirements

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according to the NRC (2006). After extrusion, the CD diet (at 100-110 ° C) was dried in a triple-deck dryer, after which it was sprayed with CO or POF, coated with chicken liver hydrolysate (palatant), and cooled. Three diets were evaluated: control diet (CD), with the inclusion of 80 g/kg beef

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tallow, and two test diets, composed of 92% of the control diet and 8% inclusion of corn oil (CO) or poultry offal fat (POF). The ingredients and the analysed and calculated chemical composition of the

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experimental diets are in Table 4 and 5, respectively.

2.3.3 Animals and facilities

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Nine beagles (five males and four females), with 12.83 ± 0.97 kg BW and 6 ± 0.2 years old, were individually housed in the same facilities described in Experiment 1. All animals were previously submitted to clinical and physical examination, vaccinated, and de-

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wormed.

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2.3.4 Digestibility assay

2.3.5 Chemical analyses

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The same procedures described in Experiment 1 were applied.

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Faecal and diet samples were ground to 1-mm particle size and analysed for DM

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(drying at 105ºC for 12 h), and AHEE (method 954.02) contents, according to the AOAC (1995). Gross energy (GE) was determined in a bomb calorimeter (Parr Instrument Co.,

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model 1261, Moline, IL, USA).Based on chemical analysis results, the coefficients of total tract apparent digestibility (CTTAD) of DM, AHEE, and GE of CO and POF were estimated

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according to the methodology proposed by Matterson et al. (1965), applying the equation: CTTADTI (%) = CTTADBD + [(CTTADDT - CTTADBD)/% replacement on DM basis/100]

Where: CTTADTI = coefficient of total tract apparent digestibility of the nutrient in the test ingredient;

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CTTADBD = coefficient of total tract apparent digestibility of the nutrient in the basal diet; CTTADTD = coefficient of total tract apparent digestibility of the nutrient in the test diet.

2.3.6 Statistical analysis

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Data were analysed according to a completely randomized experimental design, with two periods, totalling three treatments with six replicates of one dog each. Data were tested

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for normality (Shapiro-Wilk test) and for homoscedasticity (Bartlett’s test), and when these assumptions were accepted, data were submitted to analysis of variance using the GLM procedure of SAS statistical package (SAS Inst. Inc., Cary, NC). Means were compared by

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Student’s t-test at 5% probability level.

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2.4 Experiment 3: Palatability trial

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2.4.1. Objective

The objective of this experiment was to evaluate the palatability of the diets containing

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POF and CO, which were coated or not with a palatant.

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2.4.3 Animals and facilities

Fifteen adult beagles (eight males and seven females, with12.1 ± 1.3 kg LW and 6 ±

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0.2 years of age), were evaluated. Dogs were individually housed in concrete kennels (5-m

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long x 2-m wide) with shelter.

2.4.3. Experimental diets The composition of the control diet (CD) diet was identical as the CD formulated in Experiment 1. After extrusion and drying, kibbles were sprayed of 120g corn oil or poultry

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offal fat per kg, and coated or not with poultry liver hydrolysate as palatant (3% of the total diet).

2.4.4. Palatability trial

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Diet palatability was determined based on food preference and first choice test results. The diets with and with no palatant were pairwise compared, according to Griffin (2003). The

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two diets to be compared were offered for three consecutive days in two different bowls once daily (08:00 h) for 30 min or until one of the diets was completely consumed. Food offer and food residues in the bowls were weighed to calculate food preference. Food preference was

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calculated as the intake ratio (IR) between the two diets, according to the equation:

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IR (%) = [g of diet A or B intake/g of total food offered (A + B)] x 100.

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The first bowl to which the dog approached when the two test foods were

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simultaneously offered was recorded as first choice. The position of the bowls was changed

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daily to prevent any bowl position bias.

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2.4.5. Experimental design and statistical analyses A completely randomized experimental design, totalling 45 replicates per test (15 dogs

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x 3 days) was adopted. Data were first analysed for normality (Shapiro-Wilk test) and homoscedasticity (Bartlett’s test).When these assumptions were satisfied, IR results were

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analysed by the Student’s t-test, and first choice results were analysed by the Chi-square test, both at 5% probability level, using SAS statistical software (SAS Inst. Inc., Cary, NC).

3. Results

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3.1 Experiment 1: Digestibility assay and faecal characteristics Dietary corn oil concentrations did not influence the CTTAD of DM, CP, AHEE, GE or dietary ME content (P>0.05, Table 6) or faecal characteristics (P>0.05, Table 7). In addition, no digestibility or faecal parameter differences were observed when the CD was

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contrasted with the group of diets containing corn oil (COG) or with the 120CO diet (P>0.05,

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Tables 6 and 7).

3.2 Experiment 2: Corn oil and poultry offal fat digestibility

Corn oil and poultry offal fat presented similar CTTAD of DM, AHEE, and GE, as

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well as similar ME content (P>0.05, Table 8). No differences in DM intake (g/d) were

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observed among treatments (P>0.05, Table 9). The faecal characteristics (Table 9) faecal score

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(FS), pH, and ammonia-N (NH3) and dry matter (fDM) contents were not influenced by the

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experimental diets (P>0.05). However, higher faecal output (FO) was obtained with the control diet (containing beef tallow) compared with the corn oil and poultry offal fat diets

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(P<0.05), as shown in Table 9.

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3.3. Experiment 3: Diet palatability

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First choice and intake ratio were not influenced by dietary fat source (POF or CO) or

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by the inclusion or not of the palatant (P> 0.05, Table 10).

4. Discussion Corn oil is typically extracted from the germ (about 85%) by wet process using a combination of pressing and a chemical solvent. The solvent is removed at the end of the process by evaporation, and subsequently recovered and reused (Corn oil, 2006). The crude

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oil obtained is then refined for human consumption. In this study, the evaluated corn oil was extracted only by pressing, with no utilization of solvents, and was not refined. Oil refinement includes steps to neutralize free fatty acids and remove phosphatides, waxes, and pigments (Corn oil, 2006). The evaluated corn oil was not refined, presenting dark

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yellow colour and typical corn odour, characteristics that are not acceptable for human consumption. The oil included in the experimental diets was not submitted to any heat

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processing, which may cause darkening of its colour and the presence of precipitates (Corn oil, 2006). However, it was well accepted by the dogs in this study, as shown by the palatability test results.

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No studies were found in the literature evaluating corn oil as the main source of fat in

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dog foods. Because corn oil is highly available in Brazil, the evaluation of the effects of its

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inclusion on the digestibility and palatability of dog foods may allow its utilization by the dog

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food industry.

The results of Experiment 1 show that the evaluated CO concentrations did not reduce

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nutrient digestibility or dietary ME content in comparison with the control diet, which

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included poultry offal fat, wich is a typical fat source included dog foods (ANFALPET, 2011).

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In a study with rats, Apgar et al. (1986) determined higher digestibility of corn oil compared with cocoa butter, rich in saturated fatty acids, and observed that nutrient digestibility

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coefficients increased as a function of increasing dietary contents of both fat sources. This effect may be explained by the hyperbolic increase of the apparent digestibility of the fat as

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food intake increases (Kendall, 1984). Romsos et al. (1976) determined higher energy digestibility when lard completely replaced corn starch as energy source in dog foods. However, that effect was not detected in the present study because the diets fed in Experiment 1 contained the same fat concentrations, independently of its source.

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To the best of our knowledge, there are no studies published in the literature evaluating corn oil as the main source of fat in dog foods. We retrieved reports on the inclusion of corn oil in diet of horses (Resende Junior et al., 2004), lactating cows (Elliott et al., 1993), finishing cattle (Vander Pol et al. 2009), and newly-weaned pigs (Cera et al., 1989). The

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effects of the dietary inclusion of corn oil, conjugated linoleic acid (CLA), and beef tallow on the distribution of fatty acids in pig carcasses were evaluated by King et al. (2004). Studies on

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the dietary inclusion of corn oil in layer diets, aiming at increasing egg weight, were also found (Harms et al., 2000; Bonhsack et al. 2002; Merkel et al., 2002; Antar et al., 2004). Many studies evaluating dietary inclusion of CO emphasize the high linoleic acid and

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unsaturated fatty acid contents of corn oil. Marx et al. (2015) obtained higher fat digestibility

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in adult dog foods containing soybean oil relative to beef tallow, and suggested that the lower

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digestibility of beef tallow is due to its almost tenfold concentration of stearic acid (33.90%)

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compared with soybean oil (3.97%), as stearic acid is poorly absorbed by the enterocytes. According to Ricketts and Brannon (1994), the volume of lipids in the gastrointestinal tract

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and their fatty acid profile regulate the activity of pancreatic lipase and, therefore, influence

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lipid digestibility. In an experiment with cats, Pontieri (2008) determined higher digestibility

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of polyunsaturated fatty acids compared with monounsaturated and saturated fatty acids, and observed that the long-chain polyunsaturated eicosadienoic and arachidonic fatty acids

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presented 100% apparent digestibility. Although the digestibility of individual fatty acids was not evaluated in the present study, no dietary digestibility differences between corn oil and

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poultry offal fat were observed (Experiment 1), possibly because the latter, despite being of animal origin, contains high concentrations of unsaturated fatty acids. In the present study, in addition of the digestibility of the diets containing CO, the digestibility corn oil itself was evaluated. Most studies published in the literature evaluating

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feedstuffs report only the digestibility of diets and provide little information on the actual nutrient availability in individual ingredients, which would allow better utilization of these feedstuffs in feed formulation (Carciofi, 2008). Moreover, most of studies on dog food digestibility evaluate protein sources (Kawauchi et al., 2011; Félix et al., 2013).

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In general, dogs and cats present excellent fat digestion (Case et al., 2011, Marx et al.2015), as observed in the present study, where high and not statistically different CTTAD

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values of AHEE were determined for corn oil and poultry offal fat (0.987 and 0.960 g/kg, respectively). The experimental diets contained 15-16% AHEE concentrations, whereas AAFCO (2004) recommendations are 8% for growing dogs and 5% for adult dogs in foods

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containing 3500 kcal ME/kg, on dry matter basis. According to Kendall (1984), dogs are very

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tolerant to high concentrations of dietary fat (5 to 66% of diet), but most commercial dry dog

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foods contain only 5 to 13%, on DM basis (Case et al., 2011). Although the experimental diets

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contained higher fat concentrations than those recommended by AAFCO (2004), the dogs’ fat absorption capacity was not exceeded, as shown by the absence of diarrhoea and the normal

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faecal scores determined in all dogs evaluated. Otherwise, dogs would produce fatty and soft

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stools, referred as steatorrhea (Case et al., 2011). Faber et al.(2011) also obtained normal

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faecal scores in dogs fed diets with 20% fat inclusion levels on “as-is” basis. In the study by Biourge and Fontaine (2004), the faecal scores of dogs with exocrine pancreatic insufficiency

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improved when a diet with 19% fat and a source of high digestibility protein was fed. In experiment 2, the control diet (with beef tallow as fat source) resulted in higher

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faecal output compared with those including poultry offal fat or corn oil, as a result of the lower digestibility of beef tallow. Considering that the corn oil evaluated in the present study was not refined, the possible presence of free fatty acids, phosphatides, mucilage, pigments, and pesticides, could

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have also influenced food acceptability by the dogs, however no palatability differences were observed. Moreover, although Rainbird et al. (1988) stated that dogs may prefer foods containing animal fats because of their better taste and higher palatability, no food intake differences between the diets containing CO or POF and coated or not with the palatant were

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detected, indicating that unrefined corn oil is well accepted by dogs. In conclusion, dog foods containing corn oil present similar digestibility as those

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containing poultry offal fat. Crude corn oil is highly digestible and well accepted by dogs. At the dietary inclusion concentrations evaluated, corn oil does not affect the faecal characteristics of adult dogs. These results indicate that corn oil can be utilized as fat source in

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dog foods.

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Ahlstrøm, Ø., Krogdahl, A., Vhile, S.G., Skrede, A., 2004. Fatty acid composition in commercial dog foods. J. Nutr. 134, 2145-2147.

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Antar, R.S., Harms, R.H., Shivazad, M., Faria, D.E., Russell, G.B., 2004. Performance of commercial laying hens when six percent corn oil is added to the diet at various ages

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Apgar, J.L., Shively, C.A., Tarka, A.M., 1986. Digestibility of cocoa butter and corn oil and their influence on fatty acid distribution in rats. Am. Inst. Nutr. 117, 660-665.

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Biourge, V.C., Fontaine, J., 2004. Exocrine pancreatic insufficiency and adverse reaction to food in dogs: A positive response to a high-fat, soy isolate hydrolysate-based diet. J.

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Nutr. 134, 2166-2168.

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Bohnsack, C.R., Harms, R.H., Merkel, W.D., Russell, G.B., 2002. Performance of commercial layers when fed dietswith four levels of corn oil or poultry fat. J. Appl. Poult. Res. 11, 68-76.

Brito, C.B.M., Félix, A.P., Jesus, R.M., França, M.I., Oliveira, S.G., Krabbe, E.L., Maiorka, A., 2010. Digestibility and palatability of dog foods containing different moisture levels, and the inclusion of a mould inhibitor. Anim. Feed Sci. Technol. 159, 150-155.

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Carciofi, A.C., 2008. Fontes de proteína e carboidratos para cães e gatos. 2008. R. Bras. Zootec. 37, 28-41. Carciofi, A.C., Oliveira, L., Valério, A., Borges, L.L., Carvalho, F., Brunetto, M.A., Vasconcellos, R.S., 2009. Comparison of micronized whole soybeans to common protein sources in dry dog and cat diets. Anim. Feed Sci. Technol. 151, 251–260.

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Case, L.P., Carey, D.P., Hirakawa, D.A., Daristotle, L., 2000. Canine and Feline Nutrition: A Resource for Companion Animal Professionals, 2nd ed. Mosby, St. Louis.

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Félix, A.P., Zanatta, C.P., Brito, C.B.M., Oliveira, S.G., Maiorka, A., 2013. Digestibility and metabolizable energy of raw soybeans manufactured with different processing

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Anim. Physiol. Anim. Nutr. 77, 207-213. Gunstone, F.D., 1986. Fatty acid structure. The Lipid Handbook. F. D. Gunstone, J. L. Harwood, and F. B. Padley, ed. Chapman and Hall Ltd., New York, 1-23. Harms, R. H., G. B. Russell, and D. R. Sloan. 2000. Performanceof four strains of commercial layers with major changes indietary energy. J. Appl. Poult. Res. 9:535–541.

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Kawauchi, I.M., Sakomura, N.K., Vasconcellos, R.S., de-Oliveira, L.D., Gomes, M.O.S., Loureiro, B.A., Carciofi, A.C., 2011. Digestibility and metabolizable energy of maize gluten feed for dogs as measured by two different techniques. Anim. Feed Sci. Technol.

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diets for adult dogs. Arch. Anim. Nutr. 69, 297-309. Matterson, L.D., Potter, L.M., Stutz, M., 1965. The Metabolizable Energy of Feed Ingredients

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sobre a digestibilidade dos nutrientes. Ar. Bras. Med. Vet. Zootec. 56, 69-73. Ricketts J, Brannon PM., 1994. Amount and type of dietary fat regulate pancreatic lipase expression in rats. J Nutr. 124, 1166-1171. Romsos, D.R., Belo, P.S., Bennink, M.R., Bergen, W.G., Leveille, A., 1976. Effects of dietary carbohydrate, fat and protein on growth, body composition and blood metabolite levels

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in the dog. J. Nut. 106, 1452-1464. Shurson, G.C., Kerr, B.J., Hanson, A.R., 2015. Evaluating the quality of feed fats and oils and their effects on pig growth performance. J Anim Sci Biotechnol. 6, 1-10.

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Vander Pol, K.J., Luebbe, M.K., Crawford, G.I., Erickson, G.E., Klopfenstein, T.J., 2009. Performance and digestibility characteristics of finishing diets containing distillers’ grains, composites of corn processing coproducts, or supplemental corn oil. J. Anim.

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Sci. 87, 639-652p.

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15.1

185.5 909.8 161.5 36.8 97.2 31.0 13.9

189.3 909.4 162.3 29.3 97.0 32.6 14.2

187.2 911.8 159.2 32.2 94.9 32.7 13.5

14.9

14.6

15.0

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*

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Calculated chemical composition Metabolizable energy (MJ/kg)f

189.0 911.9 154.5 28.8 98.6 33.1 14.0

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Analysed chemical composition Crude protein Dry matter Acid-hydrolysis ether extract Crude fibre Ashes Calcium Phosphorus

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Table 1 Ingredients and chemical analysed composition (g/kg) of the experimental diets (Exp. 1). Item CDa Corn oil inclusion concentrations 40 g/kgb 80 g/kgc 120 g/kgd Ingredients (g/kg, as fed) Corn 424.75 424.75 424.75 424.75 Meat and bone meal 120.00 120.00 120.00 120.00 Wheat middlings 50.0 50.0 50.0 50.0 Corn germ meal 50.0 50.0 50.0 50.0 Soybean meal 150.0 150.0 150.0 150.0 Poultry offal fat* 120.0 80.0 40.0 Corn oil* 40.0 80.0 120.0 Linseed 45.25 45.25 45.25 45.25 Sodium chloride 5.0 5.0 5.0 5.0 BHT 0.5 0.5 0.5 0.5 Calcium propionate 1.50 1.50 1.50 1.50 Palatant 30.0 30.0 30.0 30.0 Vit-Min premixe 30.0 30.0 30.0 30.0

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Corn oil and poultry offal fat were added by coating after extrusion. a CD: 120 g/kg poultry offal fat; b 40 CO: 40 g/kg corn oil + 80 g/kg poultry offal fat; c 80 CO: 80 g/kg corn oil + 40 g/kg poultry offal fat; d 120 CO: 120 g/kg corn oil; e Supplemented per kg diet: Vitamin A - 16,900 IU, Vitamin D3 - 2,340 IU, Vitamin E - 104 mg/kg, Vitamin K 1.3 mg/kg, Vitamin B1 - 3.9 mg/kg, Vitamin B2 - 6.5 mg/kg, pantothenic acid - 19.5 mg/kg, niacin - 32.5 mg/kg, choline - 1.150.7 mg/kg, zinc - 156 mg/kg, iron - 104 mg/kg, copper - 13 mg/kg, iodine - 2.6 mg/kg, manganese - 45.5 mg/kg, selenium - 0.26 mg/kg, and antioxidants - 240 mg/kg. f Metabolizable energy: ME (MJ/kg) = (0.01465 x CP + 0.03558 x AHEE + 0.01465 x NFE) (Case et al., 2000).

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Table 2 Crude corn oil analyses Parameters - unit Acid value, mg KOH/g Iodine value, cgiodine/g Peroxide value, mEq/kg Saponification value, mg KOH/g Unsaponifiable matter, g/100 g

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Results 3.0 116.0 1.79 164.0 0.86

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Table 3 Fatty acid profile of corn oil, as a % of total fatty acids, and gross energy value, in kcal/kg. Fatty acids % of total fatty acids Crude corn oil <0.01

C8:0 (caprilic acid)

<0.01

C10:0 (capric acid)

<0.01

C12:0 (lauric acid)

<0.01

C14:0 (myristic acid)

<0.01

C16:0 (palmitic acid)

12.5

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C6:0 (caproic acid)

C16:1 (palmitoleic acid)

<0.01

C17:0 (margaric acid)

<0.01

C17:1 (heptadecenoic acid)

<0.01

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C18:0 (stearic acid)

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C18:1 (oleic acid)

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C18:2 (linoleic acid)

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C18:3 (linoleic acid) C20:0 (arachidonic acid)

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C20:1 (eicosenoic acid)

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34.68 48.02 <0.01 <0.01 <0.01 82.7

Total Saturated Fatty Acids

15.17

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Total Unsaturated Fatty Acids

39.62

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Gross energy(MJ/kg)

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Table 4 Ingredients of the control diet(Exp. 2). Ingredients (g/kg, as fed) Corn Meat and bone meal Wheat midds Soybean meal Beef tallow (BT) Linseed Sodium chloride BHT Calcium propionate Palatant Vit-Min premixa

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Control diet 487.60 172.40 50.00 150.0 80.0 20.0 5.0 0.5 1.50 30.0 30.0

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Supplemented per kg diet: Vitamin A - 16,900 IU, Vitamin D3 - 2,340 IU, Vitamin E - 104 mg/kg, Vitamin K 1.3 mg/kg, Vitamin B1 - 3.9 mg/kg, Vitamin B2 - 6.5 mg/kg, pantothenicacid - 19.5 mg/kg, niacin - 32.5 mg/kg, choline - 1.150.7 mg/kg, zinc - 156 mg/kg, iron - 104 mg/kg, copper - 13 mg/kg, iodine - 2.6 mg/kg, manganese - 45.5 mg/kg, selenium - 0.26 mg/kg, andantioxidants - 240 mg/kg.

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Table 5 Analysed chemical composition (g/kg) and calculated ME content of the experimental diets (Exp. 2). CD1 CD+CO2 CD+POF3 Crude protein 202.6 205.3 210.9 Dry matter 907.3 911.4 909.39 Acid-hydrolysis ether extract 99.08 163.3 164.02 Crude fibre 25.6 24.3 26.30 Ashes 95.7 95.4 95.3 Calcium 33.1 31.0 32.6 Phosphorus 14.0 13.9 14.2 Calculated chemical composition ME (MJ/kg)b 13.5 14.8 15.0 1

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Control diet, containing 80 g/kg of beef tallow. Control diet + 80 g/kg of corn oil. 3 Control diet + 80 g/kg of poultry offal. b Metabolizable energy: ME (MJ/kg) = (0.01465 x CP + 0.03558 x AHEE + 0.01465 x NFE) (Case et al., 2000).

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Table 6 Coefficients of total tract apparent digestibility (CTTAD, g/kg) of the dietary nutrients, and ME content of the experimental diets (Exp. 1). CD 40OM 80OM 120OM SEMf P value CTTAD 0.800 0.808 0.977 0.842 15.68

0.804 0.816 0.979 0.837 15.58

0.782 0.793 0.972 0.822 15.32

0.792 0.800 0.966 0.835 15.55

0.004 0.004 0.002 0.004 0.098

1control

diet, containing 120g poultry offal fat/kg g poultry offal fat and 40 g corn oil/kg 340 g poultry offal fat and 80 g corn oil/kg 4120 g corn oil/kg a Dry matter. b Crude protein. cEther extract in acid hydrolysis dGross energy e Metabolizable energy fStandard error of the mean. g Control diet vs. all diets with corn oil (40, 80, and 120 g CO/kg) (P <0.05); h Control diet vs. 120CO (P<0.05);

0.921 0.968 0.901 0.766 0.859

0.943 0.927 0.510 0.955 0.976

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CD vs. 12COh

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DMa CPb AHEEc GEd MEe(MJ/kg)

CD vs.COGg

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Table 7 Faecal characteristics of dogs fed the experimental diets (Exp. 1). CD1 40CO2 80CO3 120CO4 SEMd 3.4 6.79 0.501 40.103 0.269

3.3 7.05 0.481 39.801 0.262

3.3 6.82 0.535 39.017 0.293

3.3 6.92 0.482 39.458 0.279

0.072 0.001 0.331 0.004

1 Control

diet, containing 120g poultry offal fat/kg g poultry offal fat and 40 g corn oil/kg 3 40 g poultry offal fat and 80 g corn oil/kg 4 120 g corn oil/kg a Ammonia nitrogen (g/kg). b Dry matter. c Fecal output (g fecal DM/5 d). d Standard error of the mean. e Control diet vs all diets with corn oil (40, 80, and 120 g CO/kg) (P <0.05); f Control diet vs. 120CO (P<0.05).

CD x120COf

0.881 1.00 0.861 0.852

0.948 0.986 0.928 0.886

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2 80

CD x COGe

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Score pH NH3a DMb FOc

P value

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Table 8 Coefficients of total tract apparent digestibility (CTTAD, g/kg) of dietary nutrients and ME content of corn oil and poultry offal fat (Exp. 2). Corn oil Poultry offal fat P1 SEM2 Item CTTAD DM3 0.987 0.960 0.202 0.006 4 CTTAD AHEE 0.986 0.979 0.112 0.022 CTTAD GE5 0.997 0.986 0.092 0.033 6 ME (MJ/kg) 38.08 37.93 1.127 1.454 Means were compared by Student’s t-test (P>0.05). Standard error of the mean. 3 Dry matter 4 Acid-hydrolysis ether extract 5 Gross energy 6 Metabolizable energy

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Table 9 Faecal characteristics of dogs fed diets containing beef tallow (control diet, CD), corn oil (CO), or poultry offal fat (POF) (Exp. 2). Control diet CO POF P SEM5 Item DMI1 236.06 227.3 228.5 0.602 3.66 2 Faecal score 3.0 3.0 3.3 0.735 fDM3 0.393 0.399 0.408 0.634 0.006 FO4 0.214b 0.186a 0.188a 0.044 0.005 a,b

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Means followed by different letters in the same row are statistically different by the test of Tukey (P<0.05). matter intake (g/d). 2 Medians compared by the Kruskal-Wallis test. 3 Faecal dry matter content (g/kg) 4 Fecal output (g faecal DM/5 d). 5 Standard error of the mean.

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1 Dry

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Table 10 Number of first visits to the bowl with diet A (n) and intake ratio (IR, mean ± standard error) of dogs fed the experimental diets (Exp. 3). Diet A vs. B na IR diet A b Control diet without palatant vs.corn oil diet without palatant 22 0.53 ± 0.06 Control diet with palatant vs.corn oil diet with palatant 19 0.52 ± 0.06

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Numbers of visits to the bowl were not different by the Chi-square test, and IR were not different by the Student’s t-test (P>0.05). a Number of visits to the bowl with diet B is calculated as 45-n. b IR: [g of diet A or B intake/g of total food offer (A + B)] x 100.

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