This study aimed to evaluate the effect of sex on the chemical composition, fatty acid profile, and nutritional indexes of the
Meat from cattle has been associated with the appearance of cardiovascular disease in humans due to its particular fat composition. Changing the fatty acid (FA) profile of beef to achieve a lower proportion of saturated fatty acids (SFAs) is an important way to produce healthier meat for the consumer (Ladeira et al., 2014). According to Scollan et al. (2014), rumen lipolysis and biohydrogenation are processes that act as limiting factors in improving the lipid profile of meat. Beef cattle meat is also composed of biohydrogenation products and unsaturated fatty acids, such as rumenic and vaccenic acids, which can provide numerous benefits to human health (Dilzer and Park, 2012).
Several factors can affect the chemical composition and FA profile of beef cattle meat (Reddy et al., 2015), including nutrition (Prado et al., 2008a), finishing systems (Aricetti et al., 2008; Padre et al., 2006), and sex (Padre et al., 2007). Cafferky et al. (2019) reported that sex could be a factor that contributes to changes in muscle characteristics because it affects muscle growth and fat deposition in the carcass.
Nutrition is considered a factor that can influence meat quality. However, few studies (Prado et al., 2011; Rotta et al., 2009) have evaluated the relationship between the effect of sex and high-grain diets on the meat quality of animals.
High-grain diets improve animal performance and carcass characteristics, thus obtaining herds that are more homogeneous.
Due to the great number of variables, reaching a reasonable conclusion about meat quality using classical analytical methods is very laborious. Hence, a decrease in the number of quality variables used for certain statistical techniques and analysis is required (Destefanis et al., 2000). Principal component analysis (PCA) is a useful device to evaluate the variations among the meat characteristics and can adequately identify the most important directions of variability in a multivariate data matrix, hence allowing results that can be displayed graphically (Mwove et al., 2018).
Our hypothesis was that the fatty acid profile of meat from cattle fed with
high-grain diets would be similar between sexual classes. This study aimed
to evaluate the effect of sex on the chemical composition, fatty acid
profile, and nutritional indexes of the
The experiment was carried out at the Manaus farm located in Itajú do Colônia, BA, Brazil. This study was approved by the Committee of Ethics in Animal Research of the State University of Southwest Bahia (protocol no. 141-2016) and conducted by following the guiding principles of biomedical research with animals of the National Research Council (NRC; 1985).
There were 40 Nellore cattle identified, vaccinated against rabies, dewormed
(2.25 % ivermectin
The animals were kept in a feedlot system for 80 d, preceded by 20 d
of adaptation (adaptation period) and 60 d for data collection (experimental period). During the adaptation period, the animals received
The diet was composed of 85 % whole shelled corn and 15 % protein–vitamin–mineral supplement (monocalcium phosphate, calcium carbonate, soybean hull, soybean meal, calcium sulfate, animal urea, monensin sodium, and a vitamin and mineral premix) and was offered ad libitum, twice daily, at 08:00 and 16:00 LT (local time). The supplied diets were weighed daily and adjusted to allow for 10 % refusals (Table 1).
Ratio of ingredients and chemical composition (%; dry matter, DM, basis) of the diet.
Samples of supplied diets and refusals were collected daily and stored for later analysis. Dry matter (DM method 930.15), crude protein (crude protein Kjeldahl (CP-Kjeldahl) procedure; method 976.05), ether extract (EE method 920.39), and ash (method 942.05) contents were determined according to Association of Official Analytical Chemists methods (AOAC, 1990). Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined according to the Van Soest et al. (1991) method and corrected for ash and protein (NDFap).
The total carbohydrates (TCs) and nonfibrous carbohydrates (NFCs) were
estimated according to Sniffen et al. (1992). The concentration of nonfibrous
carbohydrates was determined by the difference between TCs and NDFap. The
total digestible nutrients estimated (TDNest) was calculated using the
equation described by Cappelle et al. (2001), where TDNest
At the end of the experimental period, the animals were weighed after 16 h of solid fasting. Animals were slaughtered at a commercial slaughterhouse, according to the industrial practices in Brazil. Prior to the slaughtering
procedures, the animals were stunned by electronarcosis. The carcasses were
suspended and bled from the jugular vein and carotid artery before being
skinned and eviscerated. Immediately, the carcasses were identified,
divided, and weighed to determine the hot carcass yield and were then placed
in a cold chamber (4
The chemical composition of the meat was determined following the methods of the AOAC (1990) for DM, CP, and ash.
The fatty acid profiles were obtained from the
Fresh meat samples were homogenized by grinding them for 10–15 s in a
coffee grinder at room temperature; immediately thereafter, the samples were dried by lyophilization for 5 d. The dried meat samples were uniformed by
grinding them for 10–15 s in a coffee grinder at 16
The tube was incubated in a 55
The fatty acid composition of the FAME sample was determined by capillary GC
on a SPTM-2560, with 100 m
Atherogenicity (AI) and thrombogenicity (TI) indexes (Ulbricht and
Southgate, 1991) and the hypocholesterolemic : hypercholesterolemic (h : H) fatty acid ratio (Santos-Silva et al., 2002) were calculated. Desirable fatty acids (DFAs) were obtained according to Rhee (1992). The activity indexes of the elongase and
The chemical composition and FA profile of
The values of the parameters obtained from the FA profile analysis in cattle fed a whole shelled corn diet produced a multivariate data set and were arranged in a matrix and interpreted using PCA. The analysis was performed using the Statistical Analysis System 9.0 (SAS, 2009) software with a data-centric average.
The sex of the animals did not influence the chemical composition of the
Chemical composition (grams per 100 g of muscle) of
Mean
For the FA composition, the 14 : 0, 15 : 0, and 16 : 0 SFA content was similar between sex groups (
Fatty acid composition (grams per 100 g FAME) of the
Mean
There were differences between sexes (
Total and nutritional quality indexes and desaturase indexes of the
Mean
The principal component analysis showed that 82.63 % of the variation in the results was explained by the first (69.52 %) and second (13.11 %) principal components (PCs; Table 5). These numbers represent the significant contributions of individual FA variables to the total variability explained by the generated PCs. To evaluate the discrimination of the FA profile, the two main components (PC1 and PC2) were plotted (Fig. 1). The score portion for PC1 compared to PC2, with a cumulative contribution of 82.63 %, was the easiest method to view the main trends defined in the different treatment samples.
Principal component analysis (PCA) plots for Nellore beef cattle. PCA plots were generated from the FA profile considering cattle sex, i.e., bulls (M) and heifers (F). PC1 and PC2 represent principal components 1 and 2, respectively.
Principal component (PC), eigenvalues (
Moisture in the
The protein content in muscle is higher in bulls than in heifers (Rotta et al., 2009); however, sex was not observed to affect the protein content of the muscle. Prado et al. (2008a) found a value of 20.41 g/100 g in muscle, similar to the average value of 19.82 g/100 g in muscle obtained in the present experiment.
According to Rotta et al. (2009), sex is a factor that affects ash content. Rotta et al. (2009) found that ash values in the
Despite the differences observed between sexual classes in relation to fat
deposition, these differences vary with the breed of cattle and are more relevant in
The chemical composition of the animals evaluated in the present study was
similar to that of Silva et al. (2021) and Gebremariam (2022) for
Zembayashi et al. (1995) suggested that carcass fat or animal age did not promote the differences in fatty acid composition between sexes; therefore, those differences are related to the ingestive behavior of the animal or to digestive and physiological metabolism. The authors cited that the lipid metabolism in the adipose tissue could be manipulated by the sex hormone status, thus affecting the enzymatic systems influenced by these hormonal changes and promoting differences in the fatty acid composition. The excess energy from ruminant feed is metabolized and stored in the form of adipose tissue, resulting in a higher fat content in the carcass (Chilliard, 1993). The enzymes responsible for FA synthesis and hypertrophy of adipocytes are regulated by the hormone status and the end products of ruminal fermentation, which are determined by the diet composition.
Among the SFAs, 16 : 0 was found at the highest concentration in both sexes, with 28.49 % and 26.22 % in bulls and heifers, respectively, followed by stearic acid (18 : 0) at 15.56 % and 12.72 % (Table 3). Few variations between these two FAs have been reported in the literature, even when comparing feedlot and grazing systems, different diets, genetic groups, or sexes (Fernandes et al., 2009; Prado et al., 2011; Maniaci et al., 2020; Krusinski et al., 2022; Schumacher et al., 2022).
According to Cao et al. (2008), palmitoleic (16 : 1
The intake of SFAs is related to an increase in cholesterol and low-density
lipoprotein (LDL) serum levels, which can result in cardiovascular problems
and have negative effects on human health. However, 18 : 1
Higher concentrations of 18 : 2
The 18 : 2
The presence of this FA in ruminant products is a consequence of two
processes, namely partial biohydrogenation of dietary FAs (linoleic and linolenic acids) or endogenous desaturation by the
There is evidence showing that the
According to Reddy et al. (2015), the contents of C18 : 1 (oleic acid) and MUFAs are higher in heifers and C16 : 0 (palmitic acid), C18 : 0 (Stearic acid), and saturated fatty acids (SFAs) are higher in bulls and steers than heifers and cows. This statement corroborates the results obtained in the present study. Furthermore, Silva et al. (2021), Blanco et al. (2020), Sobczuk-Szul et al. (2021), and Nogalski et al. (2018) found similar contents and proportions between sex classes and within the fatty acid profile.
Besides, the
In this study, heifers presented higher desaturase indexes than bulls,
explaining the higher MUFA content in heifers. These results are in accordance with Fernandes et al. (2009), in which the authors indicate that
higher indexes may be related to increased activity of the
The higher PUFA content, as observed in bulls, is explained by the higher activity of desaturase enzyme in bulls than heifers, considering that this enzyme is responsible for the synthesis of PUFA from MUFA in the muscle (Malau-Aduli et al., 2000). This observation is corroborated by the lower MUFA values in bulls, when compared to heifers, supporting the higher PUFA values in each sexual class as a result of desaturation.
Another important characteristic to remember regarding PUFAs is that the
The average AI values were 0.84 and 0.73, and the average TI values were 1.76 and 1.45 for bulls and heifers, respectively. These indexes are related to pro- and anti-atherogenic acids and indicate the potential for stimulating platelet aggregation. The smaller values for AI and TI indicate a higher proportion of anti-atherogenic FAs in fat and, consequently, a greater potential for the prevention of heart disease. The h : H ratio is based on the functional effects of FAs on cholesterol metabolism; however, this ratio also allows for nutritional assessment, considering the beneficial effects of the MUFAs described in this ratio.
We investigated the similarities in the FA profile of cattle meat to better
understand the relationships between variables. The contributions of the
first (69.52 %) and second (13.11 %) principal components represent the significant contributions of individual FA to the total variability. There was a tendency for separation of the samples in accordance with sex in the FA profile of the
Bulls and heifers fed a whole shelled corn diet and finished in a feedlot
system mainly showed differences in the fatty acid profile of the meat, indicating that the fatty acid profile in the current study was more
influenced by gender than by diet. In this sense, uncastrated bulls showed
higher proportions of saturated fatty acids than heifers. However, bulls
have the highest
The original data used in this study are available from the corresponding author upon request.
Conceptualization, design of experiments, data analysis and writing and editing were done by RRS and GGPdC. Design of experiments, data acquisition, data analysis, and writing and editing were done by EOCS. Data acquisition was done by TOJD'AL, GTJ, and GDdC. Data analysis and writing and editing were done by JIS, BMAdCM, and HDRA. All authors contributed to refining the text and approved the version to be submitted.
The contact author has declared that none of the authors has any competing interests.
This study was approved by the Committee of Ethics in Animal Research of the State University of Southwest Bahia (protocol no. 141-2016) and conducted by following the guiding principles of biomedical research with animals of the National Research Council (1985).
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This paper was edited by Steffen Maak and reviewed by two anonymous referees.