Morfometria da carcaça de novilhos mestiços submetidos a diferentes estratégias nutricionais na recria e terminação

The present study aimed to evaluate the effects of different nutritional strategies in growing and finishing phases on the carcass morphometry of 24 crossbred steers, ½ Holstein/Zebu, slaughtered at 15 months of age and 395.0kg live weight. In the growing phase, animals were maintained grazing on Brachiaria brizantha , receiving two levels of energy supplementation in quantities equivalent to 0.5 or 1.0% live weight. Then, animals were finished in feedlot receiving diets composed of 50 or 80% concentrate. The percentage of primary cuts was not influenced by feed levels in the growing and finish phases. The high supplementation level in the growing phase resulted in a higher (p < 0.05) carcass length (134.48 vs . 131.43 cm). The food levels did not influence the conformation of the carcasses, however the highest level in the growing and finishing phases resulted in a higher (p < 0.05) cushion thickness (23.46 vs 21.26 cm). It was found a significant interaction between feeding levels in the different phases for the leg length and arm perimeter with increase of 14.78 and 4.80%, respectively for animals given high energy levels in both phases. The high feeding level in the growing phase was more attractive owing the positive effects on some important measures of carcass, especially in the length.


Introduction
The State of Goiás has the fourth largest herd of dairy cattle in the country (IBGE, 2012) and it is estimated that about 5 million male calves from the dairy herd are born every year, usually of Holstein/Gir crossbred.In most cases, this category represents a problem for the producer, because they need to ingest significant amounts of milk (4 to 6 kg day -1 ) in the beginning of their development.
Many of the 7.5 million male calves from the dairy herds born every year in Brazil (ANUALPEC, 2012) are slaughtered in the first few days of life or sold for irrelevant prices.When these animals remain on the farms, they are generally raised under poor feed, which leads to mortality rates of approximately 20% and results in slow development, affecting carcass production.
The reduction in the slaughter age of beef cattle by using appropriate strategies of feeding in Acta Scientiarum.Animal Sciences Maringá, v. 35, n. 2, p. 187-192, Apr.-June, 2013 the different phases of life results in the improvement of meat quality, particularly in the tenderness (VAZ;RESTLE, 2003), as well as in higher proportion of carcass muscle (MÜLLER; PRIMO, 1986).Besides, the reduction in the slaughter age is related to a production system of technical and biological efficiency based on the composition of weight gain of young animals during the growth phase (RESTLE et al., 1999).In this phase, the body growth occurs as a function of hypertrophy of bones and muscular tissues, which require less energy to develop (BERG; BUTTERFIELD, 1979).According to Rezende et al. (2012), it is possible to improve the meat quality of crossbred dairy steers, mainly the color and the tenderness through feeding strategies.
The development after the onset of the animal growth affects the carcass morphometry.According to Vaz and Restle (2003) and Vaz et al. (2004), animals with lower weight gain, before seven months of age, presented carcass with lower percentage of special hindquarter cut.
This study evaluated the effects of different feeding plans on the carcass morphometry of crossbred dairy cattle according to the levels of energy ingestion during the growing and finishing phases.

Material and methods
The experiment was carried out from February to December 2008 at the farm school, Department of Animal Production of the Federal University of Goiás, located in Goiânia, Goiás State, Brazil, with 721-m of elevation, at the latitude 16º 35' South and longitude 49º 17' West.
The study was conducted to evaluate the carcass morphometry of 24 crossbred steers, ½Holstein/Zebu, from dairy cattle.The animals were taken from the same dairy herd.During the growing phase, between six and eleven months of age, the animals were maintained under rotational grazing on Brachiaria brizantha, in 17 plots of 2.4 hectares, changing the rotation when the grazing height was lower than 20 cm.In this phase the animals received two levels of energy supplementation, corresponding to 0.5 and 1.0% live weight.In such phase, the supplement was composed of ground corn grains added with a blend of minerals and formulated according to NRC (1996).After this period, between 11 and 15 months of age, the animals were finished in individual feedlot.They were fed with isonitrogen diets of medium (M) and high (H) energetic density due to the inclusion of concentrate, between 50 and 80%, in the dry matter (DM) of the total diet, resulting in four feeding strategies: Diet with high energy level from growing to finishing phase.
Diet with medium energy level in the growing phase and high energy level in the finishing phase.
Diet with high energy level in the growing phase and medium energy level in the finishing phase.
Diet with medium energy level in both growing and finishing phases.
In feedlot, the animals were previously adapted to the diets (Table 1) and to the facilities before beginning the trial for 14 days and fed daily at 8 a.m. and 5 p.m.The expected slaughter weight of 395 kg was achieved in 84, 105, 126 and 126 days of feedlot for the strategies 1, 2, 3 and 4, respectively.Animals were weighed after fasting for 12 hours, shortly before the shipment of animals to the slaughterhouse, inspected by the Federal Inspection Service (SIF).
The conformation and physiological maturity evaluations of carcasses were carried out according to the methodology described by Müller (1987) through subjective evaluation, following a scale of 18 points, in which a higher value indicates a better conformation.The weight of primary cuts (hindquarter, forequarter and side cut) was taken from the right half of the carcass and the percentage was expressed at the ratio of weight of cold carcass.The hindquarter comprises the posterior region of the carcass, separated from the forequarter by the 5 and 6 th ribs and from the side cut by a distance of approximately 22 cm from the spine.The forequarter includes the neck, shoulder, arm and five ribs.The side cut encompasses the ribs from the 6 th rib, separated for approximately 22 cm from the spine, and abdominal muscles.
The following measures were obtained from the right-half of the carcass: carcass length (using a measuring tape from the cranial border of the middle portion of the first rib to the cranial border of the pubic bone), leg length (from the pubic bone to the tibiotarsal joint), cushion thickness (measured with a caliper, placing one end at the external part of the inner round and the other end on the external part of the leg), and arm length and perimeter (using a measuring tape from the olecranon tuberosity to the distal end of the humerus, involving the muscles that cover the region).
The experimental design was completely randomized in a 2 x 2 factorial arrangement, with two levels of energy supplementation in the growing phase and two levels of concentrate in the diet for the feedlot finishing phase.In the analysis of variance, for all the parameters studied, every animal constituted an experimental unit.The differences between mean values were detected by t-test at 5% probability using the following mathematical model: where: Y ijk = observations on the dependent variable corresponding to the supplementation level in the growing phase of order i and concentrate level in the finishing phase in feedlot of order j and repetition k; μ = average of all observations; a i = effect of supplementation level of order i, being 1 = 0.5% LW and 2 = 1.0%LW; b j = effect of concentrate level in the finishing phase of order j, being 1 = 50% DM and 2 = 80% DM; (a*b) = effect of interaction between the supplementation level in the growing phase of order i and the concentrate level in the finishing phase of order j; E ik = experimental error relative to the observation of supplementation level in the growing phase of order i, concentrate level in the finishing phase of order j and repetition k.The normality of data distribution was tested by Shapiro-Wilk test (SAS, 2002).

Results and discussion
The percentage of forequarter and hindquarter relative to the weight of cold carcass was not affected (p > 0.05) by the effects studied with averages ranging from 38.85 to 38.33% and from 48.16 to 47.68%, respectively, showing that the animals presented a proportional growth rate in the different feeding strategies.The interaction (p < 0.05) was verified between the nutritional levels in the different phases for the side cut percentage.The animals that previously received supplementation in the growing phase equivalent to 1% LW, combined with 50% of concentrate in the diet in the feedlot finishing phase, presented higher percentage of side cut (p < 0.05) compared with animals given high nutritional level in both phases (Table 2).Means followed by different letters for each characteristic are significantly different by t-test (p < 0.05).Kabeya et al. (2002) studied crossbred steers; Holstein/Zebu crossbred, subjected to different feeding plans, and verified higher yields for hindquarter and similar yields for forequarter and side cut.These authors did not observe effect of the feeding level on the proportion of primary cuts, and they observed mean values of 39.30, 60.90 and 13.36 kg for forequarter, hindquarter and side cut, respectively.However, it is remarkable that the animals were slaughtered with the mean weight of 440 kg, higher than the weight for the present study.Ferreira et al. (2000) examined Simenthal/Nellore steers with concentrate levels of 25.0, 37.5, 50.0, 62.5 and 75.0%, observing similarity between primary cuts of carcasses as a function of the concentrate level in the diet.
Similar percentages of primary cuts were found by Alves et al. (2004) studying the carcass characteristics of Zebu cattle and Holstein/Zebu crossbred in the growing and finishing phases with average yields of 38.89, 48.35 and 12.75 for forequarter, hindquarter and side cut, respectively.
The results obtained in the present study are in line with Berg and Butterfield (1979) who stated that, under normal conditions, the animals tend to show balance between the forequarter and hindquarter; thus, the animals that present higher weight in the posterior quarter of the body also present higher weight in the anterior quarter, whereas side cut shows a greater variability.
The physiological maturity (PM) was not affected by the studied effects (Table 3).The values ranged from 13.5 to 14.0 points, which was expected considering the similar slaughter age (15 months).According to this methodology of evaluation (MÜLLER, 1987), the lowest values for a scale of 1-15 points indicate a more advanced physiological maturity.The animals given medium level of supplementation in the growing phase were slaughtered 31 days after other animals, which did not result in significant differences for the evaluation.
According to Shahin and Berg (1985), the cattle can be classified as: small animals or at early physiological maturity, medium or at intermediate physiological maturity and large size or at late physiological maturity.This classification considers the maturity and the body weight and is related to the body development, and the sexual and physiological maturity.Thus, according to maturity, the classification is not related to the weight gain rate, but to a genetic group of mean weight in which the process begins.The score of carcass conformation (Table 3) varied from 9.8 to 10.8 points, and the nutritional levels in the different phases had no effect (p > 0.05) on this parameter.According to Müller (1987), the subjective evaluation of conformation estimates the muscular expression level of carcass.Carcasses with better conformation are preferred by slaughterhouses, due to their association with a greater muscular hypertrophy and a higher yield of meat when deboning carcasses (SANTOS et al., 2008).Rodrigues et al. (2008) evaluated the carcass conformation of crossbred steers, Holstein/Zebu, through the same methodology, and verified the lack of effect of diet energy levels on this parameter.Brondani et al. (2004) studied the quantitative aspects for the carcasses of cattle fed with different energy levels in feedlot finishing, and found that animals given the highest energy level had better carcass conformation (10.8 vs. 10.5 points).The authors also showed that this variable is associated with the amount of muscle in the carcass (r = 0.89, p < 0.0033) and the arm perimeter (r = 0.92, p < 0.0011).Similar values were also described by Costa et al. (2002), recording 10.3 points for animals of similar age, fed with 44% concentrate.
Caplis et al. ( 2005) investigated the effects of the concentrate level on the carcass characteristics of steers, registering an increase in the conformation with the concentrate level and linear and quadratic effects were significant.The authors explained the results based on the concomitant increase in the live weight at slaughter, increasing the concentrate level.Costa et al. (2002) found positive correlations between the slaughter weight and the conformation.Such a correlation did not occur in the present study because all the animals were slaughtered with similar weight.
The cushion thickness (CT) was influenced separately by the level of supplementation in the growing phase and by the level of concentrate in the finishing phase (Table 4).Animals given high nutritional levels in both phases showed higher CT (p < 0.05) (23.5 vs 21.0 in the growing and 23.8 vs 21.3 in the finishing).Significant interaction (p < 0.05) between the nutritional levels in the different phases was found for the arm perimeter (AP).Animals given high nutritional levels in the growing phase associated with higher concentrate level in the finishing (HH) presented higher AP (36.0 cm) than the other treatments.
The carcass length (CL) was affected (p < 0.05) by the level of supplementation in the growing phase (Table 4).
Higher level in the growing period produced greater length of carcass (CL) (134.5 vs 131.4 cm).Caplis et al. (2005) studying the effects of the concentrate level on carcass characteristics of steers, and found that the carcass length tended to linearly increase (p < 0.07) with increased concentrate level.Significant interaction (p < 0.05) between the nutritional levels in the different phases was found for the leg length (LL).Animals given medium supplementation level in the growing phase and high concentrate level in the finishing phase presented smaller leg length (p < 0.05).In the study of Caplis et al. (2005), the leg length and width were not significantly affected by the concentrate level; but, both leg circumference and thickness increased with increased concentrate level, with linear and quadratic effects being significant for both.According to Restle et al. (1999), the linear objective measures such as CL are related to the bone growth of the animal, which occurs more intensely during the first months of age, and in the present study occurred during the supplementation on the pasture.The perimeter measures are associated with the muscle development which occurs in all phases of the animal life to achieve maturity.Thus, probably higher availability of net energy for growth coming from the higher supplementation level in the growing period and/or of concentrate in the finishing period favored the bone and the muscle development, resulting in greater CL and LL as well as CT.By studying the physical development of crossbred steers on the pasture, at different levels of supplementation, Rezende et al. (2011) found higher body growth for animals fed diets of higher energy density.In a study, Santos et al. (2008) associated lower muscular development for two-years-old steers with lower growth in the growing phase, which occurred before the feedlot finishing phase.

Conclusion
The high supplementation level in the growing phase of dairy crossbred cattle is technically attractive due to positive effects on some important carcass characteristics, producing higher carcass length.The high level of concentrate in the finishing phase produced higher cushion thickness and arm perimeter.
According to the results, it is possible to significantly improve the quantitative characteristics of carcass of dairy crossbred steers through adequate feeding strategies.

Table 1 .
Chemical composition and percentage of ingredients on dry matter basis of experimental diets during the feedlot finishing phase.

Table 2 .
Mean values and standard error for yield of primary cuts according to the level of supplementation in the growing phase and according to the level of concentrate in the finishing phase.

Table 3 .
Mean values and standard error of conformation, physiological maturity according to the supplementation level in the growing phase and to the concentrate level in the finishing phase.

Table 4 .
Mean values and standard error of carcass and objective measures according to the supplementation level in the growing phase and to the concentrate level in the finishing phase.
A,BMean values followed by different letters are significantly different by t-test (p < 0.05).