Carcass characteristics and cuts of Santa Inês lambs fed different roughage proportions and fat source

Características da carcaça e dos cortes de cordeiros Santa Inês alimentados com rações com diferentes proporções de volumoso e fontes de gordura

RUMINANTS

Carcass characteristics and cuts of Santa Inês lambs fed different roughage proportions and fat source¹

Características da carcaça e dos cortes de cordeiros Santa Inês alimentados com rações com diferentes proporções de volumoso e fontes de gordura

Iraides Ferreira Furusho Garcia; Amélia Katiane de Almeida; Tharcilla Isabella Rodrigues Costa; Izac Leopoldino Júnior; Julimar do Sacramento Ribeiro; Fernando Antonio de Souza

Departamento de Zootecnia da Universidade Federal dos Vales do Jequitinhonha e Mucuri

ABSTRACT

This work aimed at determining the influence of roughage proportions and fat source of the diet on characteristics of carcass and comercial cuts of lambs. It was used 24 non-castrated Santa Inês male lambs, ad libitum fed diet with two proportions of roughage (30 and 70%) and fat (no fat, protected fat, and soybean) slaughtered at an avarage body weight of 35.4 kg (± 1.5 kg). Animals fed 30% roughage diet showed the highest weights and carcass yields. The percentages of posterior arm and ham were higher in animals fed 30% roughage with no addition of fat source. Total leg length and internal length were higher in animals fed 70% roughage diet while leg width was higher for those fed 30% roughage diet. Addition of fat source in diets with high percentage of concentrate can increase carcass yields. This effect is higher when protected fat is used regarded to whole soybean. Although diets do not have effect on most of these cuts, the effect on the ham confirms the influence of the diet on this noble cuts.

Key Words: nutrition, ovine meat, performance, protected fat, soy bean

RESUMO

Objetivou-se determinar a influência da proporção volumoso e da fonte de gordura da dieta sobre as características de carcaça e os cortes comerciais de cordeiros. Utilizaram-se 24 cordeiros Santa Inês machos não-castrados, recebendo, à vontade, dieta com duas proporções de volumoso (30 e 70%) e de gordura (sem gordura, gordura protegida e grão de soja) e abatidos com peso corporal médio de 35,4 kg (± 1,5 kg). Os animais alimentados com dietas com 30% de volumoso apresentaram os maiores pesos e rendimentos de carcaça. As porcentagens de braço posterior e pernil foram maiores nos animais que receberam a dieta com 30% de volumoso sem adição de fonte de gordura. O comprimento total de perna e o comprimento interno foram maiores nos animais que receberam a dieta com 70% de volumoso, enquanto a largura de perna foi maior naqueles alimentados com a dieta com 30% de volumoso. A adição de fonte de gordura em dietas com alta porcentagem de concentrado pode aumentar os rendimentos de carcaça. Esse efeito é maior quando utilizada gordura protegida em relação ao grão de soja integral. Apesar de as dietas não terem efeito na maioria dos cortes, o efeito sobre o pernil confirma a influência da dieta sobre esse corte nobre.

Palavras-chave: carne ovina, desempenho, gordura protegida, grão de soja, nutrição

Introduction

Nowadays, the main purpose of the Brazilian sheep breeding is meat production. However, the quality of the product is still an obstacle to ovine meat conquers a stable market. The nutritional management of the animal can interfere on the quality of this meat and on other factors such as weight and carcass yield and on retail cuts, which are extremely important factors to measure the capacity of the animal to produce meat (Alves et al., 2003). The carcasses can be marketed as a whole or as cuts. The individualized cuts associated to the product presentation are important in the commercialization because they provide the obtaition of differentiated prices allowing rational use, avoiding waste (Silva Sobrinho & Silva, 2000), and the yield of these cuts is an important index for quality evaluation. The importance of evaluation of the carcass measures is that according to El Karin et al., (1988), when combined with the carcass weight, they satisfactorily predict composition in muscle, fat and bone. According to Garcia et al. (2003), the studies on carcasses have the purpose of evaluating subjective and objective parameters, since they are related with qualitative and quantitative aspects of the same. In this context, the area of loin eye is considered a measure that represents the amount and distribution of the muscular masses (Bonifacino et al., 1979).

According to Bendahan (2008), the management in feedlot is the best in order to reach larger productivity, and factors as rate of completion, food conversion, quality of the available animals, price and quality of food, consuming market of quality meat should be taken into account for the producer achieves a better economic return in the activity. The inclusion or not of fat sources in diet can commit the animal performance, because polyunsaturated fatty acids of long free chain are potentially poisonous to rumen microorganisms, damaging mainly the diets with high fiber proportions (Gibb et al., 2005). The objective of the present work was to evaluate carcass characteristics and retail cuts of Santa Inês lambs, fed in feedlots with diets containing or not different fat sources, whole soybean and protected fat.

Material and Methods

The experiment was carried out in Fazenda Experimental do Moura, Curvelo-MG, Setor de Ovinos of the Departamento de Zootecnia, of Universidade Federal dos Vales do Jequitinhonha e Mucuri. It was evaluated 24 Santa-Inês male lambs, weaned at 10 kg of average body weight. After weaning, they were kept in groups in feedlots until reaching 15 kg of body weight at an average age of 121 days (±13.06 days), when they were sent to the individual feedlot and randomly distributed to each one of the treatments. The following experimental diets were given once a day ad libitum: two roughage: concentrated proportions (70:30 and 30:70%, respectively). Tifton hay (Cynodom sp) was used as roughage, and the concentrate with or without inclusion of fat source consisted of ground whole soybean or protected fat - calcium soaps (Table 1). The presented food and leftovers were daily weighed, fixing 20% of leftovers. From the beginning of the confinement, the lambs were weighed weekly for monitoring body weight gain until they reached slaughter weight (35.4 kg).

The diets presented an average of 15.11% for crude protein, and 2,399.11 kcal/kg of dry matter for metabolizable energy, calculated according to NRC (1985) for lambs with weight gains of 295 g/day.

The animals were slaughtered after aproximately 14 hours of fasting of solids. They were eviscerated and later, the carcass were weighed and taken for cooling in a cold storage chamber (from 2 to 4ºC) for 24 hours, when it was removed and the weight of cold carcass was taken. The weight of hot and cold carcass was used in relation to slaughter weight to calculate their yield. It was also calculated the real yield obtained from the empty weight of each animal, in other words, heavy digestive contents discounted after evisceration.

After the carcass removal from the cold storage chamber, the following carcass measures were taken according to Fisher & Boer (1994): total length (distance from the base of the tail to the base of the neck); subcutaneous fat (taken from the 12^th to the 13^th rib); croup width (maximum width between the trochanters of both femurs); croup perimeter (perimeter of this area, referenced by the trochanters of both femurs). Next, the carcass was longitudinally divided into two equal parts. Internal length (maximum distance between previous board of the ischium-pubic symphysis and previous board of the 1^st rib), leg length (distance between fibula and previous board of tarsal metatarsal articulation), and thorax depth (maximum width between breastbone and back) were measured in the left half carcarss according to Fisher & Boer (1994). The area of longissimus dorsi (loin eye) muscle was measured through transparent standard form squared (1 cm²/cell), adapted from Cunha et al. (2001) and thickness of subcutaneous fat was measured in the cut made between the 12^th and 13^th ribs.

After the removal of the tail, kidneys and perirenal and cavity fats, the left half carcass was subdivided into the following retail cuts: leg, loin, shoulder, chop, rib/belly, previous arm, subsequent arm and neck, as described by Furusho-Garcia et al. (2004), and they were weighed for calculation of proportions (% in relation to cold carcass weight).

The data were analyzed in SAS program (SAS, 1991). The experimental design was entirely randomized in a 2 × 3 factorial outline (two roughage: concentrated proportions and three fat sources), with four repetitions for diet. The averages were compared by Tukey's test at 5% of significance.

Results and Discussion

The animals fed 30% of roughage diet presented greater weights and yields of hot and cold carcass when compared to individuals fed larger roughage proportion, a result that was already provided once diets with larger concentrate proportion usually make available more metabolizable energy which provides larger muscular mass growth and adipose tissue that compose the carcass (Table 2).

However, there was no effect (P>0.05) of roughage proportion under the real yield of cold carcass, what can be explained by a significant difference in weight and proportion (in relation to slaughter weight) of digesting content among animals consuming different diets, in which those that consumed diets with 70% of roughage presented content weight of 6.80 kg (19.22%) compared to 5.02 kg (14.17%) of those that consumed diets with 30% of roughage.

For both of hot and cold carcass weights, their yield and slaughtered weight showed inherence to addition of fat source in the diets of Santa Inês lambs corroborating with the results found by Urano et al. (2006), who working with Santa Inês ovines fed different levels of soybean (0, 7, 14, 21%) did not find differences among diets for hot and cold carcass yield, whose observed averages were 48.9 and 47.7%, respectively.

Significant differences were not observed (P>0.05) for carcass length, leg length, croup width, croup circumference and subcutaneous fat regardless to the addition of fat source and roughage proportions adopted in this study.

Considering the total leg length and internal length, it was observed that the group of animals that received diet containing 30% of roughage presented lower values for these measures, the ones which were not influenced by the addition of fat source. When the leg width was evaluated, it was observed that its measure (10.17 cm) was higher for lambs fed 30% roughage compared with animals that received 70% of hay (9.40 cm). These results provide an indicative that carcass of lambs that receive smaller roughage proportion in diet present larger compactness of the leg, provided by the largest energy intake of diets composed by ingredients with better advantages, mainly in rumen, favoring higher muscular mass growth concerning to bone tissue.

The loin eye area presented significant interaction (P<0.05) between the fat source and roughage proportion of diet, and there was no significant difference in diets without addition of independent fat source of roughage proportion. When fat was added into the diet, it was verified that the protected fat provided larger loin eye area (2463 mm²) in diet with smaller roughage:concentrated relationship whereas the addition of soybean as fat source increased loin eye area in the diet with 70% of roughage. That result could be explained by some interaction between the diet ingredients after the addition of different fat sources. The inclusion of fat source in diet with smaller roughage:concentrate relationship increases its energy content more, providing animal tissue development. However, for diets with greater roughage:concentrate relationship, despite of elevating the energy density, the fat reduces the forage digestibility, which did not happen when soybean was used. However, when evaluating the average results for loin eye area obtained by ultrasound scanning before slaughter, it was observed that there were no differences among diets.

Table 3

When evaluating the neck weight of animals that did not receive fat source, it was larger (P<0.05) for higher roughage proportion, with no differences in the percentage of this cut. With the use of protected fat, much weight as neck percentage in relation to cold carcass was larger in 30% roughage diets. The results indicate that this cut is markedly influenced by nutritional management maybe because this cut presents high fat proportion, a tissue that is easily affected by the nutrients.

The results showed that the rib/belly was influenced (P<0.05) by the addition of fat source in diet, but not by the roughage proportion, and the use of protected fat promoted larger weight and cut percentage when compared to animals that received soybean as fat source.

For the ham, which is a noble cut, the weight was smaller in lambs that received diets containing larger roughage tenor, while the addition of fat source did not influence this cut. However, the percentage of this cut in relation to cold carcass presented interaction between fat source and roughage proportion, and, in diets without fat source, the ham weight was larger for 30% of roughage. There was no variation (P>0.05) between the relationship roughage:concentrated when fat source was used, regardless to the source. For animals that received larger proportions of concentrate and did not receive fat sources, they presented a higher ham proportion. The results are in disagreement with Yamamoto et al. (2004) who evaluated the inclusion of fat sources (soybean oil, canola and linseed) in rations for Santa Inês purebreed lambs and Santa Inês x Dorset crossbreed, slaughtered at 30 kg of body weight, at an average age of 150 days, and differences were not observed for leg yield.

For the shoulder, carré, loin and anterior arm, there was no influence of diets on their weights and proportions. These results corroborate with Urano et al. (2006) who evaluated the performance and carcass characteristics of confined lambs fed soybeans in growing levels (0, 7, 14, 21%) and did not find difference among diets in the yield of retail cuts of Santa Inês lambs; and with Yamamoto et al. (2004) who did not observe difference in the yield of loin and shoulder.

Although the weights of cuts differed according to the diet (Table 5), in many cases yield did not differ significantly. This tendency can be explained by the law of harmony anatomical described by Boccard & Dumont (1960), because in agreement with these authors, carcasses with similar weights and amounts of fat means that all body areas are in similar proportions, whatever the genotype frame is.

Conclusions

The yield and carcass weights of Santa Inês lamb reared in feedlot decreases when the roughage proportion goes from 30 to 70%, but the same ones are not affected by the use of protected fat or whole soybean as fat source. The leg, a noble cut, present in higher proportion in carcass of lambs that are fed diets without fat source and with larger concentrate proportion.

Received October 31, 2008 and accepted September 8, 2009.

Corresponding author: [e-mail]

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1

Financiado pela FAPEMIG (Fundação de Amparo a Pesquisa do Estado de Minas Gerais).

Publication Dates

• Publication in this collection
  31 Aug 2010
• Date of issue
  June 2010

History

• Accepted
  08 Sept 2009
• Received
  31 Oct 2008