The impact of dietary supplementation with guava (Psidium guajava L.) agroindustrial waste on growth performance and meat quality of lambs
Introduction
The efforts to improve the production of sheep meat should be encouraged toward the slaughter of young animals and fulfil the standards of international market (Montossi et al., 2013). The main characteristic of this market is its increasingly demanding nature in terms of product quality in the last years. However, the costs associated with feeding livestock become critical because feed prices have steadily increased during the last decade (Whitney & Smith, 2015). In this regard, low-cost feed ingredients based on agroindustrial by-products are potential alternatives that can reduce the cost of mixed feed, but the effects of these ingredients on animal performance and final products need to be further considered (Whitney & Smith, 2015). Worldwide, millions of tons of waste from agroindustrial activities are generated. The world fruit production reached 865.7 million tons in 2017, wherein, the three major producers, China, India, and Brazil, produced approximately 394.2 million tons of fruits in 2017 (FAO, 2019). Moreover, several agroindustrial by-products can be considered as functional feedstuffs because of their content of bioactive phytochemicals such as unsaturated fatty acids, sterols, tocopherols, carotenes, terpenes, polyphenols and others (Kalogeropoulos, Chiou, Pyriochou, Peristeraki, & Karathanos, 2012).
Guava (Psidium guajava L.) is considered as a relevant perennial fruit crop in subtropical and tropical countries. The main countries producing guava are India, China, Thailand, Pakistan, Mexico, Indonesia, and Brazil (Rajan & Hudedamani, 2019). Particularly for Brazil, its processing generates a waste (guava agroindustrial waste, GAW) composed of peel, seed and pulp and, which stands out as one of main by-products of the agroindustry and cause environment impact if inappropriately discarded in land fields (Chang, Tan, Lok, Pakianathan, & Supramaniam, 2014). Regarding GAW composition, it contains crude protein (39.5 g/kg dry matter), ether extract (16.3 g/kg dry matter), neutral detergent fiber (761.8 g/kg dry matter), acid detergent fiber (453.2 g/kg) and ash (10.0 g/kg dry matter) (Oliveira et al., 2018). Moreover, the lipid fraction of guava agroindustrial waste is predominantly composed of unsaturated fatty acids, especially linoleic acid (77.35% of all fatty acids) (Uchôa-Thomaz et al., 2014).
Additionally, GAW is rich in polyphenols, such as tannins (2–4%) which have a great antioxidant activity and may provide beneficial effects on protein metabolism in ruminants (Costa et al., 2018; Khalifa, Barakat, El-Mansy, & Soliman, 2016). GAW also contains vitamin C and carotenoids (Batista, Lima, Alves, & Façanha, 2018) that are present in the seeds of this fruit (Khalifa et al., 2016). The antioxidant properties of polyphenols have been extensively studied (Lorenzo et al., 2018; Pateiro et al., 2018).
In this regard, polyphenols added to the food of ruminant animals are subjected to the effect of chewing, rumen bacteria, and microbial gut metabolism before being absorbed in the small intestine, metabolized in the liver, and finally deposed in the tissues (Vasta & Luciano, 2011). Once polyphenols are ingested, these compounds (such as polymeric or glycosides compounds) can be hydrolyzed, depolymerized or converted into more hydrophilic conjugates in the intestine and liver depending on their structural characteristics (Kalantar, 2018; Vasta & Luciano, 2011). It is worth mentioning that the deposition of polyphenols in the muscle of small ruminants was reported in previous studies. The incorporation of quebracho (Schinopsis lorentzii) extract (rich on tannins) in the diet of lambs improved the total phenolic content of longissimus dorsi up to 1.31 tannic acid equivalents/g of muscle (Luciano et al., 2011). A similar outcome was obtained from the dietary supplementation of lambs with rosemary polyphenols extract (Jordán, Castillo, Bañón, Martínez-Conesa, & Sotomayor, 2014). The authors found 0.2 and 0.6 mg carnosol/kg in M. deltoideus and M. abdominis, respectively. Polyphenols in tissues can affect cell metabolism through regulation of gene expression and interactions with receptors, enzymes and other proteins (Kim, Quon, & Kim, 2014). Alternatively, polyphenols can be added to meat to improve the shelf-life due to delay in lipid oxidation and the preservation of colour during the storage time (Branciari et al., 2015). Colour plays an important role in the quality of meat and stands out as the main appreciation factor at the time of purchase (Costa et al., 2011).
A high content of polyunsaturated fatty acids deposited in meat is beneficial to human health by reducing the risks of cardiovascular diseases (Andrade, Sobral, Ares, & Deliza, 2016). This benefit can be obtained by feeding meat animals sources rich in polyunsaturated fatty acids such as vegetable and marine oils and oilseeds (Raes, De Smet, & Demeyer, 2004). Regarding the physiological process of fatty acid digestion and absorption, after passing through the digestion on rumen, where a significant proportion of polyunsaturated fatty acids are converted into mono- and saturated fatty acids (biohydrogenation), the remaining polyunsaturated fatty acids are absorbed in the small intestine, delivered to animal tissues and deposited in the form of triglycerides. Consequently, the composition of intramuscular fat can be improved by diet (Raes et al., 2004; Wood et al., 2008). However, the increase in polyunsaturated fatty acids in meat can reduce oxidative stability and increase its susceptibility to oxidation (Marques, Valente, & Rosa, 2009), affecting the colour and flavour and reducing its shelf life (Vasta & Luciano, 2011).
Previous studies have reported that dried GAW can be used in sheep diets at a 20% level without any adverse effects the lamb's growth, feed conversion, digestibility, carcass traits and some blood variables (Hassan, Abdel-Fattah, Farid, & Kamel, 2016). According to Costa et al. (2018), the inclusion of GAW by up to 30% decreased cholesterol concentration and increased hormones triiodothyronine (T3) and thyroxine (T4) concentrations, improving the lipid metabolism of Santa Inês sheep (Nidda et al., 2013). However, Costa et al. (2019) found that the substitution of corn by GAW promoted a reduction in the intake of total digestible nutrients (energy), average daily gain, final weight, carcass weight and yield, and feed efficiency of animals. From an economical point of view, the addition of GW to the diet reduced the feed costs, which represent a valuable factor in animal production (Hassan et al., 2016). In this regard, GAW can be used as feed ingredient for ruminants which are able to utilize inexpensive by-products to meet their requirements for maintenance, growth and production (Silva et al., 2016).
Although benefits were reported regarding the use of GAW in the diet of small ruminants, there are still no studies on the influence of GAW on lamb meat quality traits, especially on its organoleptic characteristics. Therefore, the objective of this study was to evaluate the growth performance, physic-chemical and sensory characteristics of meat obtained from lambs fed with increasing levels of GAW in their diet.
Section snippets
Animals, diets and sampling
This study was conducted at the Federal University in Paraíba State (UFPB) - Bananeiras Campus (III). The city is located within the Brazilian semiarid region (coordinates 6° 46′ S, and 35° 38′ W, 617 m above sea level). Forty non-castrated male animals of the Santa Inês breed were used, with average age of 120 days and average initial weight of 21.33 ± 2.62 kg. Lambs were housed individually in slated floor pens (1.5 m2). Lambs were assigned to dietary treatments (8 lambs/treatment) in a
Growth performance and carcass characteristics
Initial body weight and dry matter intake were not influenced by diet (P > .05) (Table 3). No treatment differences were found for final weight, daily weight gain or feed conversion ratio, but contrasts (control versus GAW treatments) indicated GAW increased both final weight and daily weight gain, and decreased the feed conversion ratio (P < .001). Such results were unexpected given there was a decline in metabolizable energy content with increasing levels of GAW, which associated with the
Conclusion
The guava agroindustrial waste can be included in the diets of sheep in a proportion of up to 30% without compromising the physicochemical and sensory characteristics of the meat. Further investigation is also warranted to explore the effects of feeding GAW on the fatty acids profile and mineral composition of meat of fattening lambs in order to complement the results obtained in this study.
Declaration of Competing Interest
The authors declare no conflict of interest.
Acknowledgments
The authors would like to thank CAPES (Coordination for Improvement of Higher Level Personnel) for financing the project and the Federal University of Paraíba - Brazil (UFPB). Paulo E. S. Munekata acknowledges postdoctoral fellowship support from the Ministry of Economy and Competitiveness (MINECO, Spain) “Juan de la Cierva” program (FJCI-2016-29486). Thanks to GAIN (Axencia Galega de Innovación) for supporting this research (grant number IN607A2019/01). José M. Lorenzo, Roberto Germano and
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