Introduction
In cattle production, the high cost of concentrate feed ingredients has prompted the testing of new unconventional alternatives for inclusion in the diet. One alternative that has been widely tested is supplementation with co-products of the biofuel industry (Cerutti et al., Reference Cerutti, Viegas, Barbosa, Oliveira, Dias, Costa, Nornberg, de Carvalho, Bezerra and Silveira2016), because the biofuel industry has created new options for ruminant production systems by generating meals and cakes as co-products of the oil extraction process (Bezerra et al., Reference Bezerra, Edvan, Oliveira, Silva, Bayao, Pereira and Oliveira2015; Medeiros et al., Reference Medeiros, Bezerra, de Silva, Carneiro, de Morais, Moreira and Pereira Filho2015). These co-products can be low-cost alternatives for animal feeding, replacing conventional ingredients (maize and soybean) without negatively impacting (de Gouvêa et al., Reference de Gouvêa, Oliveira, Leão, Assis, Bezerra, Nascimento Júnior, Trajano and Pereira2015; Santana Filho et al., Reference Santana Filho, Oliveira, Cruz, Leão, Ribeiro, Borja, Silva and Abreu2015; Costa et al., Reference Costa, Oliveira, Silva, Ribeiro, Silva, Leão, Bezerra and Rocha2016), or even increasing, weight gain and improving the quality of meat (Owaimer et al., Reference Owaimer, Kraidees, Al-Saiady, Zahran and Abouheif2004; Shi et al., Reference Shi, Fang, Meng, Wu, Du, Xie, Ren and Zhou2014; Uchockis et al., Reference Uchockis, Švirmickas and Baltrukonienė2014). In particular, palm kernel cake can potentially be used in beef cattle feeding, especially in finishing diets, in which greater proportions of concentrate are used to increase energy intake and the rate of body weight (BW) gain in a short period of time (Santana Filho et al., Reference Santana Filho, Oliveira, Cruz, Leão, Ribeiro, Borja, Silva and Abreu2015; Visoná-Oliveira et al., Reference Visoná-Oliveira, Ferreira, Macedo Junior, Sousa, de Sousa and dos Santos2015; Santos et al., Reference Santos, Alves, Mezzomo, Oliveira, Cutrim, Gomes, Leite and Araújo2016).
Palm kernel cake is a product of the extraction of oil from Elaeis guineensis, which is a perennial palm tree. The diversity of favourable soils and a suitable climate for the cultivation of oil palm increases the availability of its residues throughout the year mainly in arid regions (Gonzaga et al., Reference Gonzaga Neto, Oliveira, de Lima, de Medeiros, Bezerra, Viégas, do Nascimento and Freitas Neto2015; Lima et al., Reference Lima, Oliveira, Garcez Neto, Bagaldo, Abreu, Silva, Carvalho and Bezerra2015; Oliveira et al., Reference Oliveira, Faria, Silva, Bezerra, Carvalho, Pinheiro, Simionato and Leão2015a, Reference Oliveira, Palmieri, Carvalho, Leão, de Abreu, Ribeiro, Pereira, de Carvalho and Bezerra2015b). These residues can potentially be used in animal feed because of the chemical composition of the cakes (Ferreira et al., Reference Ferreira, Oliveira, Balgado, Carvalho, Santos and Oliveira2012; Silva et al., Reference Silva, Oliveira, Ribeiro, Leão, Carvalho, Ferreira, Pinto and Pereira2013; Abubakr et al., Reference Abubakr, Alimon, Yaakub, Abdullah and Ivan2015; Pimentel et al., Reference Pimentel, da Silva, Silva, Schio, Rodrigues and de Oliveira2015). However, the high lipid content (ether extract-EE, 110 g/kg) along with the low-quality fibre content (acid detergent fibre-ADF, 421 g/kg) of palm kernel cake can decrease animal intake and reduce digestibility and performance due to interference with fibre digestion or diet palatability (Sanders et al., Reference Sanders, Calmon, Oliveira, Pinto, Estrela-Lima, Oliveira, Silva and Ribeiro2015; Santana Filho et al., Reference Santana Filho, Oliveira, Cruz, Leão, Ribeiro, Borja, Silva and Abreu2015). In addition, the inclusion of neutral detergent fibre (NDF) at a concentration of approximately 610 g/kg alters the physical mechanisms of intake, and low-quality fibre fills the rumen, thereby reducing the intake capacity and, consequently, the ingestive behaviour of animals (Mertens, Reference Mertens1997; Gonzaga et al., Reference Gonzaga Neto, Oliveira, de Lima, de Medeiros, Bezerra, Viégas, do Nascimento and Freitas Neto2015).
Thus, based on the chemical composition of palm kernel cake, it is possible to hypothesize that it can be added to the feed of Nellore bulls to improve performance and carcass traits without affecting the ingestive behaviour of the animals. Based on the above considerations, the objective of the current study was to determine the effects of increasing levels of palm kernel cake in a finishing diet on intake, digestibility, performance, ingestive behaviour and carcass characteristics in Nellore bulls.
Materials and methods
Animal care and experimental design
The experiment was conducted at the Experimental Farm of the School of Veterinary Medicine and Animal Science of the Federal University of Bahia located at São Gonçalo dos Campos, State of Bahia, Brazil.
Thirty-two Nellore bulls (420 ± 25.0 kg initial BW and 24 months old) were individually allotted to 32 partially covered pens (2.0 × 4.0 m2) with concrete floors, feed bunks and water cups. The experiment was conducted over an 84-day period that was preceded by 15 days of animal adaptation to the facilities, management and diets. The experimental design was completely randomized, with four dietary treatments with eight replicates each. Four inclusion levels of palm kernel cake constituted the treatments: 0, 70, 140 and 210 g/kg of the total DM content of the diet.
Diets and chemical composition
The total mixed ration (TMR) was composed of 0.35 Tifton-85 grass hay (Cynodon spp.) chopped to a mean length of 5 cm as roughage and 0.65 concentrate compound consisting of ground maize, soybean meal, mineral salt and palm kernel cake at different levels. Palm kernel cake was obtained following mechanical oil extraction (MF Rural®, Salvador, Bahia, Brazil). Then, it was ground and mixed with the other feed ingredients so that the large pieces of cake formed by pressing could be broken and homogenized with the rest of the diet. Palm kernel cake was included with a concomitant decrease of soybean and ground maize. Water was supplied ad libitum. Before the experiment, the feed components were subjected separately to chemical analysis (Tables 1 and 2) with triplicate samples.
Table 1. Chemical composition of ingredients of the experimental diets
DM, dry matter; NDIP, neutral detergent insoluble protein; ADIP, acid detergent insoluble protein.
Table 2. Ingredients and chemical composition of the experimental diets
DM, dry matter; NDIP, neutral detergent insoluble protein; ADIP, acid detergent insoluble protein;
a Mixture of urea and ammonium sulphate (9:1).
b Guaranteed levels (per kg, in active elements): calcium (max.) – 220.00 g and calcium (min.) – 209.00 g; phosphorus – 163.00 g; sulphur – 12.00 g; magnesium – 12.50 g; copper – 3500 mg; cobalt – 310 mg; iron – 1960 mg; iodine – 280 mg; manganese – 3640 mg; selenium – 32 mg; zinc – 9000 mg; and fluorine (max.) – 1630 mg.
c Calculated according to NRC (2001)
The diets were formulated according to the recommendations of the National Research Council (NRC, 2000) and contained 15.8 g/kg of crude protein (CP), for an estimated average daily gain (ADG) of 1200 g/day.
The TMR was weighed daily for the individual recipes and was divided equally into two meals, offered at 09.00 and 16.00 h, to allow a proportion of 0.10 refusals. After a period of 24 h, the refusals were weighed and meals adjusted. Samples of diet ingredients as well as the concentrates and uneaten feed were collected weekly and frozen (−20°) for further chemical analysis (in triplicate).
All samples were dried in a forced-air oven at 55 °C for 72 h. The samples were ground using a Wiley mill with a 1 mm sieve and composited for each 28-day period for each treatment. The samples were stored at ambient temperature until analysis. The DM, CP, ash and EE contents of the diets and feed refusals were determined by standard methods (AOAC, 2000) (930.15, 976.05, 942.05 and 920.39, respectively).
Neutral detergent fibre and ADF were determined according to Van Soest et al. (Reference Van Soest, Robertson and Lewis1991). Correction of the ash and protein contents of the NDF was conducted as recommended by Mertens (Reference Mertens2002), and the non-fibrous carbohydrate content (NFC) of the dietary ingredients was calculated from the difference as follows (Mertens, Reference Mertens1997):
$${\rm NFC}\, = \,100\,- {\rm NDF}\,- \,{\rm CP}\,- {\rm EE}$$Neutral detergent insoluble nitrogen (NDIN) and acid detergent insoluble nitrogen were obtained according to the recommendations of Licitra et al. (Reference Licitra, Hernandez and Van Soest1996).
The dietary digestible energy (DE) was converted to metabolizable energy (ME) using an efficiency of 0.82 (NRC, 2000). In the diet it was estimated to be 4.409 Mcal/kg of total digestible nutrients (TDN, according to Weiss, Reference Weiss1999).
Intake, digestibility and performance
Dry matter intake was measured daily for each animal throughout the experimental period as the difference between the amount of feed supplied and refusals. Dry matter and nutrient intake were estimated as the difference between the total content of each nutrient in the supplied feed and the total content of each nutrient in the refusals.
The digestibility assay was performed between days 60 and 64 of the experimental period, based on collections of the total refusals and partial faeces collections during this period. For the collection of faeces, appropriate canvas bags were attached to the animals using nylon strips to reduce inconvenience to the young bulls. After an acclimation period of 4 days to allow adaptation of the bulls to the canvas bags, two daily faecal collections (11.00 and 17.00 h) were conducted for 8 consecutive days. The faeces and refusals were dried in a forced-air oven at 55 °C for 72 h. Then, the refusal samples were ground to a 1-mm size in a Wiley knife mill (Tecnal, Piracicaba City, São Paulo State, Brazil), while the faecal samples were sieved at a size of 3 mm, stored in labelled plastic jars with lids and subsequently subjected to analysis.
Faecal production was estimated using indigestible NDF (iNDF) in situ as an internal indicator. For this purpose, triplicate samples (800 mg) of feed, faeces and refusal were placed in polypropylene polymer bags (non-woven) incubated in young, rumen-fistulated bulls for 240 h (Casali et al., Reference Casali, Detmann, Valadares Filho, Pereira, Henriques, de Freitas and Paulino2008). Thereafter, the residues of incubation were removed, washed until the water became transparent and dried in a forced-ventilation enclosure at 55 °C for 72 h. After drying, the samples were analysed for NDF content according to the methodology of Van Soest et al. (Reference Van Soest, Robertson and Lewis1991). To estimate faecal production (kg DM/d), the total amount of the indicator ingested was divided by the indicator concentration in the faeces.
The digestibility coefficients (DCs) of DM, CP, EE, NDF and NFC were calculated using the following equation:
$${\rm DC}\, = \,\displaystyle{{\hbox{kg of the portion ingested} - \hbox{kg of the portion excreted}} \over {\hbox{kg of the portion ingested}}}$$The animals were weighed at the beginning and end of the experiment, after a 16-h solid-food fast. The ADG was computed as the difference between the final and initial BW of each animal divided by the total days of the experiment. The gain : feed ratio (kg/kg) was obtained by dividing ADG by dry matter intake (DMI).
Ingestive behaviour
Individual observations of the animals were conducted every 28 days for 24 h (beginning at 09.00 h, after the diet was offered) in intervals of 5 min to evaluate time spent eating, ruminating and idling in min/day according to the method of Johnson and Combs (Reference Johnson and Combs1991). Data on each animal's behavioural activities were recorded by two trained observers, who were positioned to interfere as little as possible with the animals’ behaviour. Observers took turns every 3 h, and night-time observations were conducted with artificial lighting. The time and number of chews for each ruminal bolus per animal were recorded (total chewing time min/day). In addition, the eating (ER) and rumination rates (RR) based on DM (g DM/h) and NDF (g NDF/h) were calculated as described previously (Burger et al., Reference Burger, Pereira, Queiroz, Silva, Valadares Filho, Cecon and Casali2000). The results for the feeding behaviour parameters were obtained using the following equations:
$${\rm ER}_{{\rm DM}} = \displaystyle{{{\rm DMI}} \over {{\rm FT}}}$$
$${\rm RR}_{{\rm DM}} = \displaystyle{{{\rm DMI}} \over {{\rm RT}}}$$
$${\rm FR}_{{\rm NDF}} = \displaystyle{{{\rm NDFI}} \over {{\rm RT}}}$$where ERDM = eating rates of DM (g DM ingested/h); FT = feed time (h/d); RRDM = rumination rate of DM (g of ruminated DM/h); RT = rumination time; FRNDF = frequency of rumination of NDF (g of ruminated DM/h); NDFI = neutral detergent fibre indigestible; RT = rumination time (h/d).
Slaughter and carcass assessment
At the end of the 84-day feeding trial, all animals were slaughtered (after a 16-h fast). The hot carcass weight (HCW) and hot carcass yield (kg total carcass weight/kg final BW) were determined directly after slaughter. The other carcass characteristics evaluated were as follows: subcutaneous fat thickness over the 12th rib and longissimus muscle areaLMA (obtained after chilling for 24 h at 2 °C). The carcass conformation and subjective scores of meat marbling, texture and colour (Müller, Reference Müller1987) were also evaluated.
Statistical analyses
The experimental design was completely randomized, with four treatments and eight replicates per treatment. The following statistical model was used:
$$Y_{{\rm ij}}\, = \mu \, + {\rm} si\, + {\rm} e_{{\rm ij}}$$where Y ij = observed value; μ = overall mean; si = effect of palm kernel cake levels; and e ij = effect of experimental error.
The data were subjected to analysis of variance through the PROC GLM command of the SAS statistical package (SAS version, 9.1, 2003), and the means were subjected to regression analysis through the PROC REG command of the SAS® (9.1) statistical package (SAS University Edition). The initial weight was considered as a covariate in the statistical model. Significance was declared when P ⩽ 0.05 and trends were discussed at 0.05 < P < 0.10.
Results
Dry matter (P = 0.001), CP (P = 0.002) and NFC (P < 0.001) intake decreased linearly, and EE (P = 0.001) intake increased linearly, whereas NDF (P = 0.015) intake exhibited a quadratic increase (Regression equation y = −3E-05x2 + 0.0081x + 2.173 and determination coefficient R 2 = 0.86) with maximum inclusion of 140 g/kg palm kernel cake in the bulls’ diet (Table 3). The apparent total tract digestibility of DM (P = 0.054) and CP (P = 0.083) tended to be reduced linearly with increasing inclusion levels of palm kernel cake. In contrast, EE digestibility (P < 0.001) was associated positively with the level of palm kernel cake in the diet. Increasing the levels of palm kernel cake in the diets resulted in a linear decrease in ADG (P = 0.020) and final BW (P = 0.014) (Table 4) and a trend for the gain : feed ratio to decrease quadratically in the Nellore bulls.
Table 3. Feed intake and apparent digestibility coefficient of Nellore bulls fed different levels of palm kernel cake originating from biodiesel production
DM, dry matter; DMI, dry matter intake; SEM, standard error of mean
*Significant at ⩽0.05; P = 0.05–0.10 is a trend.
Table 4. Performance data of bulls fed different levels of palm kernel cake originating from biodiesel production
DM, dry matter; SEM, standard error of the mean; BW, body weight; ADG, average daily gain
*Significant at ⩽0.05; P = 0.05–0.10 is a trend.
There was no effect of palm kernel cake inclusion on the time spent (min/day) eating (P = 0.761) or idling (P = 0.108), or the total chewing time (P = 0.109) (Table 5) of Nellore bulls. There was a trend towards a linear decrease in the time spent (min/day) on rumination (P = 0.060) with palm kernel cake inclusion. There was a linear decrease (P = 0.011) of the DM eating rate (g DM ingested/h) and DM rumination rate (P < 0.001; g DM ruminated/h) with the inclusion of palm kernel cake in the bulls’ diet. However, there were no differences in NDF rumination (P = 0.114) and eating (P = 0.124) rate (g NDF/h) with the inclusion of palm kernel cake.
Table 5. Ingestive behaviour data of bulls fed different levels of palm kernel cake originating from biodiesel production
DM, dry matter; SEM, standard error of the mean
a Idling time includes all other activities that are not eating or rumination
b Total chewing time includes eating and rumination activities
*Significant at ⩽0.05. P = 0.05–0.10 is a trend.
The hot carcass yield was not influenced (P = 0.337) by the inclusion level of palm kernel cake, but the carcass weight (P = 0.042) decreased linearly (Table 6). Subcutaneous fat thickness (P = 0.722), LMA (P = 0.249), colour index (P = 0.305), texture (P = 0.216) and marbling (P = 0.525) did not differ among the bulls fed the evaluated diets.
Table 6. Carcass traits and quality attributes of the longissimus dorsi muscle of Nellore bulls fed different levels of palm kernel cake originating from biodiesel production
DM, dry matter; SEM, standard error of the mean; SFT, subcutaneous fat thickness; LMA, longissimus muscle area
a Scale of assessments for colour, texture and marbling according to Müller (Reference Müller1987): ranging from 1 to 5 to colour and texture and from 1 to 18 for marbling (colour = 1: dark, 3: slightly dark red and 5: red; texture = 1: very thick, 3: slightly thick and 5: very fine; marbling = 1: trace minus, 5: light, 8: small, 11: medium, 14: moderate, 17: abundant).
*Significant at ⩽0.05. P = 0.05–0.10 is a trend.
Discussion
The observed decrease in DMI could be explained by the increases in ADF (570 g/kg) and ADL (550 g/kg) contents of the diets: a tendency for decreases in the digestibility of DM (associated with increased ADF concentration) and CP was also found. These changes could have influenced protein and energy availability in animals fed palm kernel cake (Gonzaga et al., Reference Gonzaga Neto, Oliveira, de Lima, de Medeiros, Bezerra, Viégas, do Nascimento and Freitas Neto2015; Oliveira et al., Reference Oliveira, Faria, Silva, Bezerra, Carvalho, Pinheiro, Simionato and Leão2015a). In addition, with the concurrent decreases in NFC intake and contents in the diets, along with an increase in EE intake, it is possible that there was a reduction of energy available in the rumen for microbial protein synthesis, since fat is not a source of energy used by microorganisms (Visoná-Oliveira et al., Reference Visoná-Oliveira, Ferreira, Macedo Junior, Sousa, de Sousa and dos Santos2015). This situation could occur under substitution of feeds that are rich in non-structural carbohydrates with co-products rich in ADF and ADL, thereby reducing nitrogen retention by rumen microorganisms for microbial protein synthesis.
The apparent total tract digestibility of DM and CP tended to be reduced (both by 9%) with increasing levels of palm kernel cake, while EE digestibility increased (by 18%). The greater digestibility of EE and lower DM digestibility can be explained by the increase in EE intake. The increases in the content of neutral detergent insoluble protein and especially acid detergent insoluble protein caused a decrease in the CP digestibility of the diets, compromising weight gain.
The greater EE intake observed was a result of the increased palm oil lipids provided by palm kernel cake inclusion (3.2–6.1 g/kg in the composition of the diets with and without palm kernel cake, respectively). It is important to emphasize that the EE levels in the diets were below 8 g/kg, which is considered the maximum level of lipids (NRC, 2000) to avoid a reduction in DMI. Thus, the inclusion of lipids, such as those present in palm kernel cake, does not supply energy to the rumen, as there is no lipid fermentation in the rumen. Furthermore, the animal can still use lipids as an energy source, and meat and milk quality can be improved, which is an additional benefit of using diets with oil and cakes for ruminants (Abubakr et al., Reference Abubakr, Alimon, Yaakub, Abdullah and Ivan2015; Santana Filho et al., Reference Santana Filho, Oliveira, Cruz, Leão, Ribeiro, Borja, Silva and Abreu2015). When there is an increase in EE intake, coating of fibre generally occurs, causing a reduction in NDF digestibility (Oliveira et al., Reference Oliveira, Faria, Silva, Bezerra, Carvalho, Pinheiro, Simionato and Leão2015a), which was not observed in the current study. In addition, the unsaturated fatty acids present in oil cake exert toxic effects directly on ruminal microorganisms, in addition to reducing the availability of cations by combining them with fatty acids, thereby decreasing degradability (Palmquist, Reference Palmquist1991). According to Van Soest (Reference Van Soest1994), one of the factors that may affect digestibility is the degree of grinding, due to the faster rate of passage of digesta through the digestive tract. The fact that palm kernel cake was offered in ground form may have compensated for the oil-induced effects on fibre digestibility, with the final outcome being no effect on NDF digestibility. Regarding ingestive behavioural characteristics, the absence of an effect on eating, rumination and idling time (min/day) is an indicator that the fibre present in palm kernel cake in the format supplied had no impact.
There was a decrease in eating and rumination rates, which was associated with the reduction of DMI caused by increases in the ADF and ADL contents of the diets, which stimulated rumination activity (Huhtanen et al., Reference Huhtanen, Detmann and Krizsan2016); however, these conditions limited intake due to a longer retention time of feed in the rumen (Van Soest, Reference Van Soest1994), as observed in other studies involving palm kernel cake (Pimentel et al., Reference Pimentel, da Silva, Silva, Schio, Rodrigues and de Oliveira2015; Santos et al., Reference Santos, Alves, Mezzomo, Oliveira, Cutrim, Gomes, Leite and Araújo2016).
The linear decreases in final BW (50 g/kg) and ADG (230 g/kg) with increased inclusion of palm kernel cake were a result of the reduction of the intake of DM (200 g/kg) and CP (250 g/kg) and a tendency for decreases in DM (100 g/kg) and CP (100 g/kg) digestibility. As a result, there was a lower supply of analytical fractions, such as DM and CP, which interferes with performance. As observed above, the energy availability in the form of NFC decreased with increasing palm kernel cake levels in the experimental diets, which was reflected in ADG. When the cake was substituted for a portion of maize in the diet, there was a decrease in the rapidly fermentable carbohydrate content of the diets, whereas the estimated ME and DE concentrations in the diets were not altered. In fact, these values were almost equivalent to those of the control diet, which contained greater amounts of NFC. It is possible to infer that palm kernel cake was an ingredient that, when included as a lipid source, maintained the energy levels of the diets, though not at high enough levels to compensate for the energy lost through the reduction on DM intake and digestibility; therefore, both ME and metabolizable protein were limited compared with the control diet (Ferreira et al., Reference Ferreira, Oliveira, Balgado, Carvalho, Santos and Oliveira2012).
The addition of co-products to feedlot rations has been used to improve animal performance and, consequently, reduce the time to slaughter and increase the efficiency of the production system (Abubakr et al., Reference Abubakr, Alimon, Yaakub, Abdullah and Ivan2015). However, many factors intrinsic to the use and quality of co-products in ruminant animal diets interfere with intake regulation in addition to the digestibility of these alternative sources (Van Soest, Reference Van Soest1994). Greater inclusion of palm kernel cake (140 or 210 g/kg) was reflected in lower gains (1.05 and 1.06, respectively), possibly because the cake protein exhibits less availability of amino acids in the rumen and no availability of amino acids in the intestine. The cake contains a significant amount of protein in the form of ADIP, which reduces the availability of amino acids in the rumen for intestinal absorption and influences the animals’ performance (Van Soest, Reference Van Soest1994).
The decrease in intake by animals with higher palm kernel cake inclusion reduced HCW by approximately 15 kg. For each 10 g increase in the inclusion level of palm kernel cake, there was a 272 g decrease in carcass weight. The decrease in HCW with the inclusion of palm kernel cake is relevant from a market point of view, where prices are sometimes negotiated based on this parameter, and a decreased HCW can therefore result in lower profit margins for the producer.
Regarding qualitative carcass characteristics, even though carcass weight decreased in animals consuming diets with a greater proportion of palm kernel cake, subcutaneous fat thickness and the LMA were not affected, indicating similar development of the studied animals.
Colour, texture and marbling characteristics did not differ with the inclusion of palm kernel cake. The average colour score recorded in the present study was 3.65, which corresponded to ‘slightly dark red’ according to the classification proposed by Müller (Reference Müller1987), and this colour is generally well accepted by the consumer. The texture of the LMA received an average score of 4.00 points, corresponding to a fine texture, indicating that the meat surface granulation presented features that classify it as a good quality product. The meat of the bulls used in the present study exhibited marbling scores ranging from slightly low to low according to the scale proposed by Müller (Reference Müller1987).
In conclusion, the use of palm kernel cake above 70 g/kg in finishing cattle diets is not recommended because a longer finishing period will be needed for the bulls to reach their target slaughter weight, or a market for lighter carcasses will have to be found. However, qualitative carcass attributes were not affected by the use of palm kernel cake. In the decision to use palm kernel cake above 70 g/kg, producers should take into consideration the profitability arising from the inclusion of palm kernel cake, which is used to reduce the amounts of expensive ingredients in diets (maize and soybean), as well as the possible need to maintain, rather than gain animal weight. The strategic use of palm kernel cake associated with other feed concentrates can be helpful for obtaining animals with similar carcass quality. However, the use of palm kernel cake as an ingredient will depend on the harvest period, during which there is a reduction in the cost of purchasing palm kernel cake.
Author ORCIDs
Ronaldo L. Oliveira, 0000-0001-5887-4753
Financial support
This research was supported by the National Council for Scientific and Technological Development (CNPq), by the Coordination and Improvement of Higher Level or Educational Personnel (CAPES), by the Bahia State Research Support Foundation (FAPESB), and by the Federal University of São Francisco Valley.
Conflict of interest
None.
Ethical standards
All animal use procedures followed the guidelines recommended by the Animal Care and Use Committee of the institution (Protocol 17/2014).
