ABSTRACT

The objective of this study was to determine the effect of the dietary inclusion of lipid-based diets (whole cottonseed and protected fat) on the pH, meat color and fat, tenderness and cooking yield in Longissimus thoracis muscle of cattle feedlot. Were used 39 Nellore cattle uncastrated with average initial body weight of 494.1 ± 10.1 kg and 36 months of age were housed for 63 days in pens with thirteen animals each. A completely randomized design with three treatments and thirteen replications was used. The treatments evaluated were: Feed with 2.50% whole cottonseed (control diet); feed with 11.50% whole cottonseed; and feed with 3.13% whole cottonseed added of protected lipid (PL), all on a dry matter basis. No differences were found for pH 24 h post mortem, meat color and fat, tenderness or cooking yield. The values of shear force of meat the animals presented differences (P <0.05), and the animals fed with 11.50% of cottonseed had greater value than those fed 2.50% on the diet, in relation to dry matter. The study came to the conclusion that the protected lipid does not influence the qualitative characteristics of meat and the amount of 11.50% of cottonseed in the cattle diet does not contribute to the improvement of texture and tenderness of the meat.

Key words: Color, cooking yield, shear force, whole cottonseed.

The study was carried out in the Chapéu de Couro Farm, located in the city of Aguaí/SP, Brazil, at 22°04′00″ South, 47°09′03″ West, average altitude of 615 m above sea level. The region is characterized by a hot and humid seasons from October to March, followed by a cold and dry season from May to September. The climate of the region is Cwa in the Köppen classification (mesothermal, with hot and humid summers and dry winters).

 

Animal management and treatment

 

A group of 39 uncastrated, Nellore animals raised in Brachiaria humidicola pastures was used in the study. Mean age of the animals was 36 months and initial mean live weight was 494.1 ± 10.1. Animals were identified and dewormed with Ivermectin 1% before the beginning of the trial. Then, animals were randomly assigned to one of three treatments, based on dry matter: feed with 2.50% CS (control diet), feed with 11.50% CS, and feed with 3.13%% CS added of 1.77% protected lipid (PL). Animals were confined for 63 days (experimental period) in collective pens of 247 m² (19 m² per animal). The confinement facility was made up of three pens with sand floors, with 13 animals per pen. Feeders and drinkers in these pens were provided with roofs and animals had free access to them. Feeders were made of concrete, and the length available per animal was 0.70 m.

 

A 10-day period was used for the adaptation to the diet and management prior experimental period, in which concentrate was gradually added to the feed, until a 50:50 forage:concentrate ratio was reached. The experimental diets were formulated in the CNCPS software 4.0 (CNCPS, 2000) for uncastrated finishing cattle to provide weight gains of 1.4 kg/animal/day. Forage:concentrate ratio was 50:50 on a  dry  matter basis. All the concentrate ingredients and forage were weighted in order to prepare the experimental diets, using electronic weighing scale kg. Sugar cane chopped was used as forage, and concentrate was made up of urea, cracked corn kernels, citrus pulp, cotton meal, CS and/or PL. The PL used in this study was made from soybean vegetable oil and had fatty acid calcium salts in its composition. Animals were fed twice a day at 8 am and 4 pm, in a total mix diet, with about 5% leftovers that were weighted in the morning for diet adjustment. Nutritional composition of the diets is shown in Table 1.

 

 

Procedures for data collection

 

After thawing, composite samples of a 21-day period were obtained. Samples of feed and forage were weighted and pre-dried at 60°C for 72 h. Then, they were weighted again in a mill with 1-mm sieves, and stored in plastic bags. Samples of the experimental diets were sugar cane and concentrate which were collected every seven days, placed in plastic bags and stored in at -4°C for subsequent measurements.

 

The samples were analyzed for Proximate Analysis according to AOAC (1990) and NDFom and ADFom (excluding ash) according to procedures of Van Soest et al., 1991), and lignin by the sulphuric acid method Lignin (sa), after a sequential neutral-acid detergent extraction (Van Soest et al., 1991). In the NDF analyses, thermostable α-amylase was used without sodium sulfite (Mertens, 2002). Non-fiber carbohydrates (NFC) in the ingredients of the diets were determined by the following equation, according to Sniffen et al. (1992), NFC = 100 - (%NDFcp + %CP + %EE + %MM). Due to the presence of urea in the diets, NFC in them were calculated as indicated by Hall (2000): NFC = 100 - [(%CP - %CP from urea + %urea) + %NDFcp + %EE + %Ash]. Estimated metabolizable energy (ME) in Mcal/kg of DM was determined according to the NRC (1996) recommendations, considering that 1 kg of total digestible nutrients (TDN) contains 4.409 Mcal of digestible energy (DE), using 0.82 as the conversion factor to transform DE in ME. Analyses of the feed samples were carried out in the Food Analysis Laboratory at the Animal Nutrition and Improvement Department of Faculdade de Medicina Veterinária e Zootecnia at Universidade Estadual Paulista, Botucatu campus. Results of these analyses are shown in Tables 2 and 3.

 

 

 

Slaughter procedures and sample preparations

 

After 63 days of the study, animals were weighted for the last time after a 14-h solid food fasting. Mean final live weight was 577.01 kg ± 11.34. Soon after being weighted, animals were taken to a slaughterhouse (FRIGONOBRE, in the city of Torrinha, state of São Paulo), 166 km from the study site, in solid food fasting until the moment they were slaughtered. Animals were slaughtered according to the regular flow of the industry.

 

After slaughter, carcasses were identified and divided into two halves that were kept in a cold chamber for 24 h at 2°C. Using pH meter was determined post-mortem pH in Longissimus thoracis muscle between the 12^th and 13^th rib of the left half carcass. After, part of each animal was removed, and divided in three samples (steaks). Steaks were 2.5 cm thick and were identified and stored individually in plastic bags under vacuum. Samples were frozen in a freezer at -18°C at Universidade Estadual Paulista, Faculdade de Ciências Agronômicas, Botucatu campus, at the Animal Products Technology Laboratory.

 

Chemical analysis of the meat and fat color

 

Samples  of  Longissimus thoracis  muscle  of   each   animal   were thawed in refrigerator, then removed from the packaging and exposed to the air for 30 min to allow oxygenation surface. The color of the meat was determined by the Minolta colorimeter CR-410 and the color of the subcutaneous fat, using the optional Milnolta CR-400 second Honikel (1998). The parameters evaluated were L*, a* and b* the CIELab system, where  L*  is  brightness,  a* represents intensity of red and b* intensity of yellow.

 

Cooking yield and shear force (aged beef)

 

The  samples  were  weighed  in  the  balance  semi-analytical   and submitted to cooking on a grid until they reach the automatic internal temperature of 71°C, as measured by a digital thermometer in the geometric centre of the sample. The evaluation of proceeds in cooking was made by the difference between the weights of the samples before and after cooking according to the methodology of Honikel (1998). The same samples cooked were refrigerated by 12 h the 4°C, and then cut into cylinders 1.10 Øcm with the support of a drill press avoiding fats and nerves. Shear force was calculated in these samples cut into cylinders through the Brookfield texture CT3 Texture Analyzer 25 k equipped with a set of blade Warner-Bratzler according to the methodology of Savell et al. (2015).

 

Statistical procedures and model evaluation

 

A completely random design with 3 treatments and 13 repetitions was used, according to the Υij = μ + Ti + eij model, where: Yij is the value observed in the j^th experimental unit (animal) that received the i^th treatment; μ is the overall mean; Ti is the fixed effect of the i^th treatment^; eij is the experimental error related to the experimental unit. Data were analyzed by means of the Generalized Linear Models Procedures (GLM). The averages were adjusted by the method of least squares (Least Squares Means). Statistical analyses were performed using the SAS program (2002), and means were compared using Tukey test at a 5% significance level.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The characteristics the meat and subcutaneous fat the Nellore cattle was shown in Table 4. No differences in pH 24 h after slaughter were observed in the meat of Nellore cattle fed different sources of fat (Table 4), and mean value for this variable was 5.59. Difference was not observed (P > 0.05) to cooking yield of muscle Longissimus thoracis the Nellore cattle fed lipid sources. However, for the shear force differences (P < 0.05) were founded. For diet control the lowest value found 5.10 (kg) while for the treatment with 11.50% CS the great value found was 6.30 (kg). It may be observed  in  Table  4,  for Brightness L*, intensity the red a*, intensity of yellow b* that there were no differences (P>0.05) between the treatments for characteristics the meat or fat.

 

 

 

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