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The objective of this study was to determine blood lactate concentration during the finishing period and after slaughter and to verify its influence on body weight and meat quality traits of Nellore bulls feedlot finished. Ninety Nellore males were used, with a mean initial body weight of 390 ± 37 kg and age of 24 months. Lactate concentration in the blood was measured by spectrophotometry on days 1 (Lac01), 14 (Lac14), 27 (Lac27) and 69 (Lac69) of the feedlot period and immediately after slaughter (Lac96). Fresh meat samples were collected from the Longissimus thoracis muscle for determination of luminosity (L *), red (a *) and yellow (b *) intensity, shear force and pH of unaged meat and aged for seven days. Lactate concentrations were analyzed by the PROC MIXED of the SAS program, considering in the model the effects of pen and day of blood samples collection. Simple correlations between the studied variables were estimated using the procedure CORR of the program SAS. The lactate was stable during the confinement period, with mean values equal to 4.83 ± 0.30 mMol/L; 5.68 ± 0.29 mMol/L; 5.03 ± 0.29 mMol/L and 4.15 ± 0.31 mMol/L for Lac01, Lac14, Lac21 and Lac69, respectively. The highest mean lactate concentration was obtained on the day of slaughter (Lac96: 10.77 ± 0.27 mMol/L). Significant association was detected between a * and b * color parameters of the unaged meat and the lactate concentration at the day of slaughter (Lac96). There is no association between blood lactate concentration at the day of slaughter and body weight of Nellore animals feedlot finished. Blood lactate concentration on the day of slaughter is associated with the coloring of the meat and is independent of other measures of meat quality in Nellore animals feedlot finished.

The objective of this study was to estimate the heritability of age at first calving (AFC), body condition score at first calving (BCF), body condition score at calving (BCC), weaning weight (WW), yearling weight (W12), weaning weight of calf/weight of cow at calving (RCC) and weaning weight of first calf/weight of cow at first calving (RCCF) ratios, and genetic correlations of AFC, BCF, WW and W12 with RCCF, in a Canchim beef cattle herd. The variance and covariance components were obtained by bayesian inference with single and two-trait analyses. The statistical models included the additive direct and maternal, the permanent environmental and the residual random effects, and the fixed effects of year and month of birth or of calving, age of cow at calving and sex of calf, depending on the trait. The posterior means of heritability, obtained by single-trait analyses, were 0.12 (AFC), 0.36 (BCF), 0.18 (BCC), 0.50 (WW), 0.46 (W12), 0.16 (RCC) and 0.40 (RCCF) indicating that these traits have enough genetic variability to show response to mass selection with the exception of AFC. The genetic correlations of AFC (-0.61), BCF (-0.36), WW (-0.20) and W12 (-0.05) with RCCF suggest that selection to reduce age and body condition score at first calving should improve the productivity trait of females at first calving, while selection for heavier females at young ages would not promote any change in the productivity of dams.

The aim of this study was to evaluate digestibility and feeding behavior of Nellore heifers belonging to different classes of residual feed intake (RFI). Thirty-two heifers ranked high in RFI (0.491± 0.51 kg/d; n=15) and RFI low (- 0.447 ± 0.51 kg/d; n=17) with a mean age of 502 ± 23.61 days and average weight 364 ± 27.96 kg were kept in confinement for 48 days, with formulated diet based on Tifton 85 hay, corn, cottonseed meal and urea, and ratio of forage: concentrate ratio of 45:55%. The parameters analyzed were digestibility, ingestive behavior and their correlation. Animals low RFI showed higher digestibility of dry matter (DMD), neutral detergent fiber (NDF), acid detergent fiber (ADF) and cellulose that high RFI animals (49.14% versus 45.38%, 56.65% versus 49.88%, 49.96% versus 45.08%, 61.61% versus 56.40% for DMD, NDFD, ADFD, CELD, respectively). These results indicate that more efficient animals have better food utilization. No differences were found in the variables of ingestive behavior among classes of RFI. Changes in the RFI can be partly explained by the digestibility of nutrients, which is related to ingestive behavior of animals.

During three consecutive years a total of 144 bull records from the Zebu breeds Nellore, Guzerah and Caracu breed, selected for post-weaning weight, finished in feedlot and slaughtered at an average age of 19 months, with three different degrees of maturity, were analyzed. Multivariate procedure (MANOVA) was used to estimate the residual correlations between body measurements and carcass traits. The model fitted the effects of genetic groups, order of slaughter and year of birth. Correlation coefficient between hip height and carcass weight was 0.37, antagonistic to the amount of kidney fat (-0.14). High correlation coefficients were estimated between chest girth and carcass weight (0.77), blade (0.57), and chuck (0.67) and positive correlations were estimated between chest girth and kidney fat (0.38) and carcass fat (0.52). The estimated correlation coefficient between body length and carcass weight was 0.38. Correlation coefficients between dorsal line length, rump length and distance among pin bones and all the meat cuts of commercial interest analyzed ranged from 0.24 to 0.56. In addition to live body weight, chest girth and distances between hip bones can be considered an auxiliary tool for evaluation of carcass traits in Zebu and Caracu bulls. Other body measurements analyzed resulted in low or null relationship to carcass traits.

Studies have shown associations between temperament traits and productivity on cattle industry, some results indicate that animals which adapt easily are less agitated, therefore there will be fewer losses in carcass due to the low incidence of hematomas and higher weight gain. The objective of this study was to associate the average daily gain in Caracu animals, subject to performance test (PT), with reactivity measured by flight speed test. The average daily gain was divided in three classes, considering 0.5 standard deviation below and above the average. The average gain classes 1, 2 and 3 was 1158.55 ± 89.48, 957.14 ± 54.77, 620.88 ± 127.41 g/day, respectively. The flight speed test (FS) measures how long the animal takes to cover a known distance after the release of the squeeze chute. Faster animals were considered more reactive. The study was performed at Centro APTA Bovinos de Corte from Instituto de Zootecnia-Sertãozinho, SP, in which were used 109 flight speed records, of 56 animals, obtained in the beginning and at the end of PT. Data were analyzed using the PROC MIXED (SAS 9.3). The model of analyses included the fixed effects of average daily gain classes (1, 2 and 3) and measures (1 and 2), besides the random-effects of animal and residue. The interaction classes measures, even as age as covariate, were excluded from the initial model, because they didn’t show significance at level of 5%. Significant differences weren’t observed (P>0.05) on reactivity of animals for the various average daily gain classes, evidencing that there was no relationship between performance and temperament in the animals evaluated. As in the present work, others studies performed in Centro APTA Bovinos de Corte, with Nelore animals also didn’t find correlations between average daily gain and the flight speed test. The reactivity in Caracu steers measured in the beginning and at the end of PT was significantly (P

The main factor that affects performance and animal efficiency is the feed intake. This trait is important for diets formulation, animal performance prediction, and planning and controlling yield systems. In addition, estimating digestibility values is essential to determine nutritional value of feed. The objective of this study was to evaluate feed intake and nutrient digestibility of beef cattle. The tests were performed at Centro APTA Bovinos de Corte – Instituto de Zootecnia - Sertãozinho-SP, on 2012 and 2013, with 95 Nellore animals. Forty-seven animals (25 heifers and 22 young bulls) were kept on Marandu grass (Urochloa brizantha) paddocks in the dry season for 46 days. The forage’s NDF content on this period was 56.71% and 14.63% of CP. Forty-eight animals (24 heifers and 24 young bulls) were kept on feedlot system receiving a diet containing corn silage, grass hay, ground corn, soybean meal with a NDF content of 50.18% and a CP content of 13.98% for 70 days. After the feedlot period, the 48 animals that were in the pens were allocated on Marandu grass (Urochloa brizantha) paddocks in the rainy season for 46 days, when the NDF content of the forage was 65.09% and the CP was 9.02%. Data were analyzed using PROC MIXED in SAS 9.2, the mixed model analysis included the fixed effects of sex and diet and the linear effect of covariate weight and the lsmeans were compared by F test, using 5% of significance level. Total dry matter, insoluble NDF, non-fibrous carbohydrate, CP and total TDN intakes were higher for the animals kept on feedlot system (P

The technique of ultrasound is a noninvasive method performed in vivo. The technology has been used to measure carcass traits as longissimus muscle area (LMA), subcutaneous fat and marbling. It allows accurate data measures with no animal slaughter and a greater number of animals evaluated in a period, resulting in economic benefit. Some technicians recommend the use of the relation between longissimus muscle height and width as a better indicator trait of retail beef yield than LMA itself. The purpose of this study was to calculate the ratio between longissimus muscle height and width (RATIO) in order to estimate the simple correlation between RATIO, obtained in vivo, and dressing percentage (DP%), retail beef yield expressed in kg (YIELD_kg) and percentage of retail beef yield (YIELD_%), obtained after slaughter. A total of 116 Nellore bulls born between 2006 and 2009, with an average age and weight of 18 ± 1.10 months and 437 ± 60 kg at slaughter, which were raised and finished at Centro APTA Bovinos de Corte, Sertãozinho, São Paulo, Brazil, were used. Among 116 animals, 33 were slaughtered in 2008, 34 in 2009, 25 in 2010 and 24 in 2011. Before slaughter images were obtained by ultrasound between the 12th and 13th ribs, transversely over the longissimus muscle with immobilized animals in containment chamber, using the ultrasound machine Pie Medical 401347 - Aquila (Esaote Europe BV), 18 cm linear probe of 3.5 MHz. On that occasion, the animals were weighed (fasted live weight). Subsequently longissimus muscle height, width and area were measured using the Echo Image Viewer 1.0. Carcasses were weighed before and after the chilling period. DP% was calculated as the ratio between fasted live weight and hot carcass weight. The sum of the retailed meat cuts weights corresponded to the retail beef yield and was expressed as kilograms (YIELD_kg) and as percentage of cold carcass weight (YIELD %). Simple correlations were estimated using PROC CORR, SAS (SAS Inst., Inc., Cary, NC). The average of longissimus muscle height, width, LMA, RATIO, DP%, YIELD_kg, and YIELD_% were: 60.9±9.02 mm, 132±10.1 mm, 67.4±8.78 cm2, 0.46±0.07 mm/mm, 61.0±1.54%, 174±23.4 kg and 66.3±2.07%, respectively. The simple correlation between RATIO and DP%, YIELD_kg, and YIELD_% were low and not significant. These correlations were much lower than the correlations between LMA and YIELD_kg, and YIELD_%. Based on the correlation coefficients estimated, it would be better to use LMA instead of RATIO in order to predict retail beef yield. The RATIO is not a good indicator of retail beef yield in young Nellore bulls.

The objective of this study was to estimate heritability of carcass muscle index (MI) in yearling (MIy) and post-yearling (MIp) Nellore cattle. MI is the measure of longissimus muscle area (LMA) expressed in relation to body weight (MI=100×LMA/BW), being an indicative of animal muscularity. The records of LMA, obtained by ultrasound, and body weight (BW) were from the three Nellore herds reared at Centro APTA Bovinos de Corte, Instituto de Zootecnia, Sertãozinho-SP, born between 1999 to 2011, excepting 1998, 2000 and 2003. The measures were collected when the animals were on average 372 ± 26 days (yearling) and 562 ± 33 days (post-yearling) of age. The animals are progeny of 163 bulls and relationship matrix included 3436 animals. Variance components were estimated by REML in two single-trait analyses. The model included the fixed effects of contemporary group (herd-year-sex, i=1, …, 48), month of birth (j=1, …, 3) and dam age (linear and quadratic effects) and animal age at measurement (linear effect), and random effects of animal and residual. The average of LMA and BW were: 48.4 ± 10.7 cm² and 287±59 kg; 50.5 ± 9.2 cm² and 339 ± 64 kg, respectively for yearling and post-yearling. Despite the differences between yearling and post-yearling LMA and BW (plus 2.2 cm ² and 52 kg at post-yearling than yearling), the same was not observed for MI. BW has increased from yearling to post-yearling, LMA has not increased proportionally, and MIps was smaller than MIy. The heritability estimates for IMy and IMp were medium to high magnitude indicating that part of the variation in these traits are attributable to genes of additive effects. In previous studies, the heritability of LMA at yearling was also higher than heritability of LMA at post-yearling, however, heritability of yearling weight was lower than heritability of post-yearling weight. More studies are required to estimate genetic correlations of MIy and MIp and weight and percentage of retail product of carcass before indicating them as selection criteria to increase muscularity in Nellore cattle.

In study of more efficient animals for food utilization, it is of great importance to know differences between genders. There are differences between male and female cattle in growing and body composition, mainly those related to the action of sex hormones. This study aimed to evaluate the sex effect on feed efficiency traits in young Nellore animals. Individual feed intake data from eight tests, performed from 2005 to 2012 at Centro APTA Bovinos de Corte-Instituto de Zootecnia-Sertãozinho-SP were utilized. The tests began after weaning, when the animals had, on average, 286 days of age and 229 kg of body weight. The tests duration ranged from 56 to 112 days, depending on the year. Traits analyzed were final body weight (FBW), dry matter intake (DMI), average daily gain (ADG), feed conversion ratio (FCR), feed efficiency ratio (FER), residual feed intake (RFI) and Kleiber ratio (KR). Data were analyzed using the MIXED procedure of SAS. The model included the fixed effect age at the test beginning as linear covariate and the random effects: sex, facilities and year. Least square means were calculated and compared by t test. Males had greater FBW than females, what was expected, due to the action of male hormones which benefits the muscle deposition. Greater means of ADG and DMI were also detected for males, when compared to females, because heavier animals have higher gains and consume food according to their body sizes. Among all the feed efficiency measures studied, significant differences between males and females were detected in FCR and KR. Analyzing FCR, females used more food than males for 1 kg of body weight gain, being less efficient. The same was found when KR was analyzed, having males higher KR and being more efficient. No significant differences were detected between males and females for FER and RFI. Young Nellore females are less efficient than males in this growth stage, because of the differences in growth curves due to the sex hormones action.

Several studies have reported relationship between eating behavior and performance in feedlot cattle. The evaluation of behavior traits demands high degree of work and trained manpower, therefore, in recent years has been used an automated feed intake measurement system (GrowSafe System ®), that identify and record individual feeding patterns. The aim of this study was to evaluate the relationship between feeding behavior traits and average daily gain in Nellore calves undergoing feed efficiency test. Date from 85 Nelore males was recorded during the feed efficiency test performed in 2012, at Centro APTA Bovinos de Corte, Instituto de Zootecnia, São Paulo State. Were analyzed the behavioral traits: time at feeder (TF), head down duration (HD), representing the time when the animal is actually eating, frequency of visits (FV) and feed rate (FR) calculated as the amount of dry matter (DM) consumed by time at feeder (g.min-1). The ADG was calculated by linear regression of individual weights on days in test. ADG classes were obtained considering the average ADG and standard deviation (SD) being: high ADG (>mean + 1.0 SD), medium ADG (± 1.0 SD from the mean) and low ADG (0.05) among ADG classes for FV, indicating that these traits are not related to each other. These results shows that the ADG is related to the agility in eat food and not to the time spent in the bunk or to the number of visits in a range of 24 hours.

Several studies have reported differences between male and female cattle in growing and body composition. The differences occur mainly by hormonal factors, however, there is little information about the relationship between sex and feed efficiency traits in beef cattle. The residual feeding intake (RFI) is a feed efficiency measurement and has been an alternative to improve the profit in beef production system. It is defined as the difference between dry matter intake observed and estimated by regression in function of weight gain and metabolic body weight. More efficient animals have the intake observed smaller than the predicted (low RFI), unlike the less efficient ones have the intake bigger than predicted (high RFI). This study aimed to evaluate the sex effect (male and female) on growing and feeding efficiency traits in young Nellore bulls selected for post weaning weight. Data from males and females Nellore animals obtained during RFI evaluation tests were utilized. The tests were performed at Centro APTA Bovinos de Corte – Instituto de Zootecnia - Sertãozinho-SP, between 2005 and 2011. The tests duration ranged from 56 to 112 days, with the adaption period raging from 28 to 56 days, depending of the year. At the tests beginning the animals had, on average, 286 ± 42 days of age. The traits analyzed were initial body weight (IBW), final body weight (FBW), average daily gain (ADG), dry matter intake (DMI) and RFI. Data were analyzed using de GLM procedure of the SAS program. The model of analyses included the fixed effects of contemporary group (year and selection line), sex (male and female) and age at the beginning of test as linear covariate. Means of growing traits were different between sex (Table 1), being males heavier than females at the begging (35.28%) and at the end (29.17%) of the test . Males gained 29% more weight than females. Considering DMI, males consumed 21% more food than females. These results showed that males had greater feed conversion, 6.70 kg DM kg-1 gain X 7.82 kg DM kg-1 gain. However, no significant differences were detected on RFI between the sex, showing an independent relationship between RFI and sex in beef cattle. Growth traits and feed intake were influenced by sex, however the efficiency of feed utilization, defined as RFI was not influenced by sex in young cattle Nellore.

The reactivity is an important behavioral trait that is directly linked to the economic characteristics of beef. Less reactive animals have better performance and efficiency, thus, this study aimed to evaluate the influence of reactivity in the animals´ classification for residual feed intake (RFI). The study was conducted at Centro APTA Bovinos de Corte – Instituto de Zootecnia -Sertãozinho/SP. Sixty males belonging to the Traditional Nelore herd were classified into high (> mean + 0.5 SD, n = 21), medium (±0.5 SD from mean, n = 20) and low RFI (