Ríos-Lugardo, Andrea Paola

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    Rendimiento productivo, características de la canal y cortes y calidad de carne de corderos alimentados con dietas isonitrogenadas con dos niveles de nutrientes digeribles totales
    (2020-05-29) Ríos-Lugardo, Andrea Paola; Rodríguez-Carías, Abner A.; College of Agricultural Sciences; Fernández Van Cleve, John; Rivera-Serrano, Aixa; Department of Animal Science; Comas-Pagán, Myrna
    The effect of feeding total isonitrogenate rations with 2 percentage levels of total digestible nutrients on dry matter consumption (CVMS), daily (GPD), and total weight gain (GPT) and feed conversion (CA) of growing native lambs were evaluated. The effect of diets on carcass yield, main cuts, minor cuts, and meat quality was evaluated after slaughter. The study was carried out in three phases located in groups of 3 lambs in 3 pens per diet with 18 native lambs: 1) productive performance, 2) carcass and cut yields, and 3) meat quality evaluation. The productive performance was evaluated using a completely randomized design with 2 treatments and 3 repetitions, using the pen as an experimental unit. Diets that satisfy protein requirements (13.3% CP) with 66% and 73.33% of NDT were used, for D1 and D2, respectively. The diets were offered for 6 weeks in lambs with an initial weight range of 18.18 kg - 23.18 kg. D1 consisted of 40% grass hay and 60% commercial concentrate. D2 had a 66:34 ratio of alfalfa hay and chopped corn. Both diets were offered at 4% of the live weight of the animal on a dry basis (CVPD). The effect of these diets on CVMS, GPD, GPT, and CA was evaluated. During the productive performance test, heat stress was evaluated using as reference the temperature-humidity index (THI) and the physiological parameters of the lambs, respiratory rate (RR), cardiac rate (RC) and, rectal temperature (RT). After 40 days of feeding, the lambs were slaughtered at an average live weight of 25 kg. For phases 2 and 3 of this study, the same statistical analysis was used but using the individual lamb as an experimental unit. During the slaughter process, the hot carcass weight, cold carcass weight, and hot carcass performance and cold carcass performance were evaluated. From each carcass were obtained weights and yields of the primary cuts (neck, ribs, and front leg, ribs, back leg, and loin) and retail (shoulder chop, French chop, loin chop, ribs, back leg, “fricasé”, and shanks). For the determination of meat quality, pH, color, water holding capacity, tenderness, and nutrient content were evaluated using the Longissimus dorsi muscle. The productive performance was carried out under conditions of heat stress with THI greater than 72 and physiological parameters of an average heart rate of 97.01 beats per minute and an average respiratory rate of 56.54 breaths per minute greater than the optimum considered for sheep in their thermal comfort zone. Both diets satisfied the animal's protein requirement (13.3% CP), although the protein content of D2 was 1.55% higher than D1. The CDPV was higher (P<0.01) in lambs fed with D2 (3.77%) than D1 (3.35%). Feed (g/d) consumed, offered, and rejected was similar for both experimental diets. In both diets, the established GPD of 100 g/d was achieved (D1= 104.44 g and D2 = 106.33 g). The weight of hot (PCC) and cold (PCF) and the performance of hot (RCC) and cold (RCF) carcass of lambs were similar between treatments. The PCC and PCF for D1 were 9.47 kg and 9.35 kg, respectively, while D2 obtained values of 9.74 kg and 9.47 kg for PCC and PCF. The RCC was (D1= 37.53% and D2= 38.87%) and in the RCF values were obtained (D1= 37.03% and D2= 37.67%). No effect of diets was observed on the length of the front and rear quarters. The neck yield was higher (P<0.01) in animals fed with D1 than with D2, but the other primary cuts were similar in weight and yield. The weight of the 7 retail cuts was also similar between treatments, but the yield of “fricasé” was greater (P<0.03) in lambs fed D1, (9.35%) than D2 (8.26%). Feeding with different levels of NDT had not an effect on the nutritional components of the meat, water holding capacity, tenderness, loin eye width, and fat layer. Although the pH was higher (P<0.01) in the carcass of the lambs that were fed with D2 than in D1 in both cases, the value is in the optimum range. In summary, feeding growing lambs up to 25 kg on average with diets that satisfy protein requirements and 2 percentage levels of NDT greater than the requirement (53%), under conditions of thermal stress, did not affect their productive performance, carcass and meat yield, and meat quality parameters.