Resumo
The Residual Feed Intake (RFI) is a measure of feed efficiency usually evaluated post-weaning, and according to available evidences in the literature is highly correlated to RFI measured at other ages. The objective of present study was examining the reclassification of RFI in Nellore bulls classified in two post-weaning tests. In post-weaning performance test 127 Nellore males (210 ± 45 days of age) in feedlot collective pens (GrowSafe Systems®) were evaluated. Data of dry matter intake (DMI, 7.23 ± 1.72 kg/day) and mean body weight (BW, 306.72 ± 7.54 kg) were collected during 112 days, and the animals were classified according to RFI. The RFI was estimated as multiple regression error of DMI on average daily gain (ADG) and metabolic weight (BW0.75). Thereafter, a sample of 24 animals (408 ± 45 days old), 12 high (2.34 ± 0.24 kg DM/day) and 12 low RFI animals (-1.48 ± 0.24 kg DM/day) were reclassified after performance post-weaning test in feedlot for 84 days in individual pens. The diet was offered twice daily, contained corn silage (53.6% DM), Urochloa hay (10.0% DM), ground corn (21.8% DM), soybean meal (11.6% DM) and mineral supplement (3.0% DM). The experimental design was completely randomized. Data were analyzed using GLM procedure (SAS Inst., Inc., Cary, NC), fitting a model including the fixed effects of RFI class and the initial weight as linear covariate. Means were
O artigo não apresenta resumo em português.
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The direct determination of carcass composition as experimental routine, despite being the most accurate method, is time consuming, laborious and expensive. Indirect methods have been developed to estimate on quick, simple, economical and reliable ways empty body composition of beef cattle. This study was performed with the objective of developing accurate regression equations to predict carcass composition of Nellore animals using 9-10-11th ribs chemical composition and performance measures as independent variables. Sixty-seven non-castrated Nellore bulls were randomly selected for finishing period in two consecutive years (2008 and 2009) and were finished in individual pens for approximately 100 days, until they reached four millimeters of subcutaneous fat thickness over Longissimus muscle. They were slaughtered at 540 days of average age and body weight at slaughter (BW) and carcass weight (CW) were taken. The 9-10-11th ribs cut was obtained according to Hankins and Howe (1946) and weighted (RW). The carcass composition was obtained after grinding, homogenizing, sampling and analyzing the left side of the carcass. Chemical analysis of 9-10-11th ribs cut and carcass were carried for protein (RP and CP), fat (RF and CF), ashes (RA and CA) and water (RWt and CWt). Stepwise and Mallows Cp options were used in PROC GLMSELECT (SAS Inst., Inc., Cary, NC) to determine significant (
O artigo não apresenta resumo em português.
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This study aimed to evaluate feed intake and behavior during feed efficiency test of Nellore males from different residual feed intake (RFI) classes. Data from 85 Nellore males, with initial average age of 270 ± 23 days and body weight of 239 ± 41 kg were used. The feed efficiency test was performed during 119 days, divided in four periods. The first period (adaptation) had 28 days, and the three subsequent periods had, respectively, 28, 28 and 31 days. Animals were fed ad libitum at GrowSafe System® with 10 feeders, which recorded bunk attendance (BA), frequency of visits (FV) and feed intake (FI) individual data. After test end, RFI was calculated by the difference between observed and predicted feed intake, based on average daily gain and metabolic body weight. Then, animals were classified into low ( mean - 0.5 standard deviation-SD), medium (± 0.5 SD from mean) and high (>mean + 0.5 SD) RFI. Statistical analyzes were performed by PROC MIXED (SAS Inst., Inc., Cary, NC), including in the model effects of test period (1, 2, 3 or 4), RFI classes (low, medium or high) and interaction, being animal age considered as linear covariate. Feeding behavior pattern was not different among the efficiency test periods (P>0.05), however differences were detected among RFI classes inside the periods (P 0.01) (Figure 1). Low RFI animals, when compared to the medium and high RFI
O artigo não apresenta resumo em português.
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This study was carried out to identify associations among carcass traits and residual feed intake (RFI) in young Nellore males feedlot finished. Data was obtained in four experiments, after the animals had been evaluated in individual pens and classified in low RFI( mean - 0.5 standard deviation), medium RFI (± 0.5 standard deviation from mean) and high RFI (> mean + 0.5 standard deviation). One hundred-sixteen non castrated males from low and high RFI classes, with 369 kg of initial body weight and 439 days of initial age, were used for finishing phase. Animals were distributed in individual pens for 100 days and weighed at the beginning and end of experimental period after 16 hours solids fasting. Animals were slaughtered with a minimum of 4 mm for subcutaneous fat thickness over Longissimus muscle between the 12th and 13th ribs. Slaughter was carried out in experimental slaughter houses following the normal procedures of Federal inspection. After slaughter, carcasses were weighed (hot carcass weight) and transferred to chilling room where they were kept at 2C for 24h. Dressing percentage was calculated as the ratio between hot carcass weight and slaughter body weight. After chilling, carcasses right halves were divided into carcass primary cuts: forequarter, hindquarter and spare ribs, which were also weighed. Data were analyzed using the SAS MIXED procedure (SAS Inst
O artigo não apresenta resumo em português.
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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 forages 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
O artigo não apresenta resumo em português.
Resumo
The direct determination of carcass and empty body composition as experimental routine, despite being the most accurate method, is time consuming, laborious and expensive. Therefore, indirect methods have been developed to estimate on quick, simple, economical and reliable ways for the compositions of carcass and empty body of beef cattle. This study aimed to obtain the correlations among the compositions of 9-10-11th ribs, carcass and empty body for protein, fat, ashes and water contents, expressed in percentage and kilograms, in young Nellore bulls. Sixty-seven non-castrated Nellore bulls were randomly selected for confining period in two consecutive years (2008 and 2009) and were confined in individual pens for approximately 100 days, until they reached a subcutaneous fat thickness of 4 mm over the Longissimus muscle. They were slaughtered at an average age of 540 days and body weight of 398 kg. Chemical analysis of the 9-10-11th ribs, carcass and empty body were carried for protein, fat, ashes and water. The 9-10-11th ribs cut was obtained according to Hankins and Howe (1946). Carcass composition was obtained after grinding, homogenizing, sampling, analyzing and combining edible portions and bones. Empty body composition was obtained after grinding, homogenizing, sampling, analyzing, and combining blood, hide, head + feet, viscera, and carcass. The correlation coefficients
O artigo não apresenta resumo em português.
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This study was conducted to describe the ingestive behavior in Nellore and Bonsmara cattle during the feed efficiency test. The test was performed at the Centro APTA Bovinos de Corte Instituto de Zootecnia, Sertãozinho, São Paulo State. Twenty-three Nellore and 19 Bonsmara calves, aging 276 ± 19.2 and 278 ± 29.2 days and weighing 246 ± 26.7 and 273 ± 30.7 kg, on average, at the beginning of the test, respectively, were used. Animals were randomly located in individual pens, during four periods of 28 days, being the first period a pre-test adjustment period. Calves were fed twice a day, with the same diet. Daily the amount of food offered was adjusted in order to maintain 5 to 10% of refusals. Dry matter intake (DMI) was calculated by the difference between food offered and refusals. Animals were weighed each seven days. Average daily gain (ADG) was obtained by linear regression of weights in days in test. Feed conversion was obtained by the DMI:ADG ratio. Ingestive behavior was measured three times, every 28 days, excluding de pre-test period. Observations lasted 24 hours, with records at intervals of five minutes. The behavioral traits analyzed were: bunk attendance duration (BAD), rumination time (RT) and idle time (IT) expressed in minutes per day. Data were analyzed using the PROC MIXED procedure (SAS 9.3). The model included the fixed effects of period, breed and weight
O artigo não apresenta resumo em português.
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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 Eu
O artigo não apresenta resumo em português.
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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 ( mean - 1.0 SD). Data were analyzed using the PROC MIXED procedure (SAS 9.3). The model included animal and residue as random effects and the fixed effects of ADG class (1, 2 and 3) and age at the middle of t
O artigo não apresenta resumo em português.
Resumo
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 ( mean - 1.0 SD). Data were analyzed using the PROC MIXED procedure (SAS 9.3). The model included animal and residue as random effects and the fixed effects of ADG class (1, 2 and 3) and age at the middle of t
O artigo não apresenta resumo em português.
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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
O artigo não apresenta resumo em português.
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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 didnt show sig
ês.
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The residual feed intake (RFI) is a parameter used in the identification of animals with respect to more efficient feed utilization. However, physiological basis are still unknown, however, the interrelationships between nutrition an immunity of the animal can contribute to the investigation of biological phenomena relevant to the RFI, since the defense system to oxidative effects caused by free radicals, is formed by acid polyunsaturated fatty acids, water soluble substances and enzymes, which derive mainly from the use of nutrients in the diet. The objective of this study was to evaluate the immunological parameters of Nellore heifers classified according to RFI. It were evaluated 176 heifers (born between 2008 and 2010), Traditional Nellore herd from Instituto de Zootecnia - Sertãozinho/SP, forming three groups of evaluation, submitted to test post weaning feed efficiency and classified into high (> mean + 0.5 SD, n= 55), medium (± 0.5 SD, n= 65) and low RFI ( mean 0.5 SD, n= 56). The diet was formulated based on Brachiaria decumbens hay, corn, cottonseed meal and mineral mixture (45:55, forage: concentrate). The weight of the animals were performed in fasting blood samples collected by venipuncture vein, using tubes of 10 ml type vacuntainer with EDTA anticoagulant. In the clinical laboratory, we measured the values of leukocytes (LEU); Targeted (SEG) and lymphocyt
O artigo não apresenta resumo em português.
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Residual feed intake (RFI) is a feed efficiency trait defined as the difference between actual feed intake and the one predicted on the basis of requirements for production and maintenance of body weight. Evidence exists of a positive correlation between RFI and fat thickness in Bos taurus, suggesting that low RFI cattle (feed efficient ones) are leaner. The objective of this study was to access the relationship between fat thickness and RFI by partial correlation including all animals (n=603, 300 bulls and 303 heifers), and by means comparison including only animals divergently classified by RFI (low RFI, n=192 and high RFI, n=186). The animals were born from 2004 to 2010, and were performance tested after weaning for 56 to 112 days, depending of test year and sex. The average age and body weight at the beginning of performance test were 286±42 days and 225±51kg. At the end of performance test images of backfat thickness (BF) were obtained by ultrasound (Pie Medical-Aquila-3.5 MHz linear probe) between the 12th and 13th ribs, transversely over the longissimus muscle. Images of rump fat thickness (RF) were obtained at the junction of the gluteus medius and biceps femoris muscles between the hook and pin bones. The images were saved and subsequently analyzed using Echo Image Viewer 1.0. For partial correlations (MANOVA, SAS 9.3), the model included fixed effect of contemporary g
O artigo não apresenta resumo em português.
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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 gai
O artigo não apresenta resumo em português.
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The cattle production is a sector of agricultural activity that has impact on global warming due to enteric fermentation from digestive process that releases methane (CH4), with energy loss of food and consequent inefficiency of system. Residual feed intake (RFI) is a feed efficiency trait defined as the difference between actual feed intake and the one predicted on the basis of requirements for body weight production and maintenance. There are evidences that more efficient cattle (low RFI) have lower methane daily emissions than less efficient cattle (high RFI). This study aimed to evaluate the pattern of CH4 daily emission and its relationship with RFI obtained during the CH4 collection in Nelore previously evaluated for this trait. A sample of 23 from 62 young bulls, previously classified into low RFI72 and high RFI72 in the 72-days performance test (RFI72), were evaluated. After the 72-days test, the individual feed intake was recorded for a further 45 days. Another RFI was obtained from the last 32 days (RFI32), and the animals were classified into two RFI32 classes: below zero (low RFI32) and above zero (high RFI32). CH4 daily emissions of each animal were collected during the last 7 days of this period, being preceded by 7 days for adaptation of animals to the collection apparatus. The sulfur hexafluoride (SF6) tracer technique was used for estimating enteric methane emi
O artigo não apresenta resumo em português.
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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 ( mean - 0.5 SD, n = 19) . The animals had, on average, 256 kg and 264 days, respectively, for weight and age. They were housed in individual pens for 112 days, being 28 for adaptation to facilities and diet and 84 days for data collection. The diet was composed by Brachiaria hay, corn, cottonseed meal and mineral supplement and was offered to the animals twice a day, with ad libitum access to diet and water. The RFI was calculated as the difference between observed and predicted intake by a multiple regression equation, which considers the average daily gain and metabolic body weight. To measure the temperament, blood samples were collected from the animals´ jugular vein and analyzed to quantify serum levels of cortisol. The composite score (CS) was done by a trained observer, giving scores from 1 to 5 for the general movement of
O artigo não apresenta resumo em português.
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Data from nine studies were compiled to evaluate the effects of selection for postweaning weight on some carcass characteristics in experimental herds of selected Nellore (NeS), control Nellore (NeC), Caracu (CaS), Guzerah (GuS) and Gir (GiS) breeds from Instituto de Zootecnia genetic selection program. After the feeding performance test (168 days after weaning), samples of bulls (n=490) from the progeny groups born between 1992 and 2000 were selected for finishing period and slaughtered. Treatments were different across studies. Meta-analysis was conducted with a random coefficients model in which herd was considered a fixed effect and treatments within year and progeny groups as random effects. Slaughter, empty body, hot carcass and cold carcass weights were higher for NeS and CaS, intermediate for GuS and lower for NeC e GiS. CaS bulls had higher proportions of forequarter and spare ribs and lower proportion of hindquarter than the other groups. No significant differences were found for percentage of edible portion among the genetic groups. Selection for postweaning weight in Nellore increased carcass, hindquarter, forequarter, and spare ribs weights without altering dressing percentage, carcass quarter, and hindquarter prime meat cuts proportions.
Dados de nove estudos foram compilados com o objetivo de avaliar os efeitos da seleção para peso pós-desmame em algumas características de carcaça de rebanhos experimentais Nelore Seleção (NeS), Nelore Controle (NeC), Caracu (CaS), Guzerá (GuS) e Gir (GiS) do programa de melhoramento genético do Instituto de Zootecnia. Após a Prova de Ganho de Peso (168 dias pós-desmame), amostras de machos (n=490) de progênies nascidas entre 1992 e 2000 foram selecionadas para o período de terminação e posterior abate. Em cada estudo os animais foram submetidos a diferentes tratamentos de terminação. Foi conduzida meta-análise com modelo de coeficientes aleatórios, onde rebanho foi considerado efeito fixo e tratamentos dentro de ano e progênie foram considerados efeitos aleatórios. Os pesos de abate, do corpo vazio, da carcaça quente e da meia carcaça direita resfriada foram maiores para NeS e CaS, intermediários para GuS e menores para NeC e GiS. O CaS apresentou maiores proporções de dianteiro e ponta-de-agulha e menor proporção de traseiro que os outros grupos genéticos estudados. Não foram encontradas diferenças significativas entre as porcentagens de porção comestível das carcaças dos grupos genéticos estudados. A seleção para peso pós-desmame aumentou os pesos de carcaça, traseiro, dianteiro e ponta-de-agulha no Nelore sem alterar o rendimento de carcaça, as proporções dos quartos da car
Resumo
Sperm traits of 243 young bulls from Caracu (n=62), Gir (n=23), Guzerá (n=59) and Nellore (n=99) breeds, with 20-25 months of age, from the Breeding Program of Estação Experimental de Zootecnia de Sertãozinho, were analyzed. On the day of breeding soundness evaluation animals were weighed, the scrotal circumference was measured and the semen was collected by electroejaculation. The sperm motility, vigor and morphology were assessed and the animals were classified according to the andrological classification by points (CAP). No difference was observed among breeds for any seminal trait evaluated, although Nelore presented lower scrotal circumference average than the other breeds. When the animals were classified by body weight, it was observed that the heavier animals presented greater scrotal circumference, better seminal characteristics and, consequently, greater percentage of these animals were considered sexually mature comparing with the other body weight groups. It was concluded that the animals selected for post-weaning and reared on pasture from the taurine adapted breed Caracu and from the zebu breeds Gir, Guzerá and Nelore have proved able to reproduction at 23.2, 23.4, 22.7 and 22.8 months, respectively, corresponding to age which reached an average weight of 452, 422, 470 and 467 kg respectively.
Resumo: Foram submetidos a avaliação andrológica 243 touros jovens das raças Caracu (n=62), Gir (n=23), Guzerá (n=59) e Nelore (n=99), com idade entre 20 e 25 meses, participantes do Projeto de Seleção das Raças Zebuínas e Caracu, da Estação Experimental de Zootecnia de Sertãozinho. No dia da avaliação andrológica os animais foram pesados, o perímetro escrotal foi aferido e o sêmen foi coletado por meio de eletroejaculador. Foram avaliados motilidade, vigor e morfologia espermática e, posteriormente, os animais foram classificados segundo o sistema de classificação andrológica por pontos (CAP). Não foram observadas diferenças entre raças para as características seminais avaliadas, embora touros jovens Nelore tenham apresentado menor média de perímetro escrotal que as demais raças. Quando os animais foram classificados por classes de peso corporal, foi observado que os animais mais pesados apresentaram maior perímetro escrotal, melhores características seminais e, consequentemente, maior porcentagem deles foram considerados aptos a reprodução, comparativamente às demais classes de peso. Concluiu-se que os animais da raça taurina adaptada Caracu e das raças zebuínas Gir, Guzerá e Nelore, selecionados para peso pós-desmama e criados em pastagem, apresentaram-se aptos a reprodução aos 23,2, 23,4, 22,7 e 22,8 meses, respectivamente, correspondendo às idades em que atingiram peso méd
Resumo
The Residual Feed Intake (RFI) is a measure of feed efficiency usually evaluated post-weaning, and according to available evidences in the literature is highly correlated to RFI measured at other ages. The objective of present study was examining the reclassification of RFI in Nellore bulls classified in two post-weaning tests. In post-weaning performance test 127 Nellore males (210 ± 45 days of age) in feedlot collective pens (GrowSafe Systems®) were evaluated. Data of dry matter intake (DMI, 7.23 ± 1.72 kg/day) and mean body weight (BW, 306.72 ± 7.54 kg) were collected during 112 days, and the animals were classified according to RFI. The RFI was estimated as multiple regression error of DMI on average daily gain (ADG) and metabolic weight (BW0.75). Thereafter, a sample of 24 animals (408 ± 45 days old), 12 high (2.34 ± 0.24 kg DM/day) and 12 low RFI animals (-1.48 ± 0.24 kg DM/day) were reclassified after performance post-weaning test in feedlot for 84 days in individual pens. The diet was offered twice daily, contained corn silage (53.6% DM), Urochloa hay (10.0% DM), ground corn (21.8% DM), soybean meal (11.6% DM) and mineral supplement (3.0% DM). The experimental design was completely randomized. Data were analyzed using GLM procedure (SAS Inst., Inc., Cary, NC), fitting a model including the fixed effects of RFI class and the initial weight as linear covariate. Means were
O artigo não apresenta resumo em português.