Effects of Early Weaning on Performance and Carcass Quality of Nellore Young Bulls.

This study compared early weaning (EW; 150 days) with conventional weaning (CW; 240 days) in Nellore young bulls, evaluating performance, carcass characteristics, and meat quality. A total of 74 non-castrated male calves were divided into two weaning strategies: EW (n = 37) and CW (n = 37). During the growth phase, which lasted 454 ± 14 d for EW calves and 359 ± 16 d for CW calves, animals received a protein-energy supplement at a ratio of 5 g per kg of body weight while grazing Brachiaria brizantha cv. Marandu. The animals were managed for an 87d finishing phase in three collective feedlot pens, with a 3-week adaptation protocol, starting with corn silage to a concentrate ratio of 55:45 and reaching a ratio of 30:70 in the final diet. Body weight, average daily gain (ADG), dry matter intake (DMI), feed efficiency (FE), carcass characteristics, and meat quality were evaluated. The EW group was approximately 44 kg lighter than the CW at the time of conventional weaning (p < 0.001). However, this weight difference did not influence ADG, DMI, and FE in the finishing phase. No significant differences were observed in carcass characteristics such as yield percentage, loin area, subcutaneous fat thickness, and meat quality, except for the weight of primal cuts, which was greater in the CW group (p < 0.001). Thus, although calves weaned early are lighter throughout subsequent production phases than those weaned conventionally, performance, efficiency, carcass yield, and meat quality are not affected.

Growth performance, carcass, and meat quality traits of Tropical Milking criollo bulls fed with two energy-level diets.

The aim of this study was to determine the effect of two energy-level diets on the beef performance of Tropical Milking criollo bulls grouped by weight and age in three periods: initial, middle, and final. Evidence on intensive beef production from Tropical Milking criollo cattle breeds are unknown, and productive alternatives for dairy producers in the hot tropics are needed. Bulls were fed in each period with low (LE, 2.2 Mcal ME/kg DM) and high (HE, 2.9 Mcal ME/kg DM) energy diets and content phase feeding protein of 14.5, 12.0, and 10.3%, respectively. For each period, ten bulls were randomly assigned to diets. In all periods, growth performance for final body weight, average daily gain, feed intake, and feed conversion were all superior in HE (p ≤ 0.05). For the final period, slaughter body, hot and cold carcass weights, and dressing were also superior in HE (p ≤ 0.05); for meat quality traits, differences were observed in muscles Longissimus dorsi, Semimembranosus, Infraspinatus, and Serratus ventralis for pH and tenderness (p ≤ 0.05), although not for diets. For color L*, a*, and b* system, neither diet nor muscle had effect on L* (p > 0.05); however, the diet-muscle interaction was significant for a* (p ≤ 0.05), and only muscle effect was detected for b* (p ≤ 0.05). Tropical Milking bulls responded positively to a high-energy diet, despite not being a beef breed.

Sex and animal behavior on yield and bruises in different beef cuts / Sexo e comportamento animal no rendimento e contusões em diferentes cortes de carcaça de bovinos

The objective of this study was to examine the effects of behavioral differences in cattle on bruising on different cuts and on carcass yield. A total of 4,061 lots of cattle were evaluated, which corresponded to 199,026 carcasses. Animal temperament was classified as calm, anxious, or excited. The following carcass cuts were evaluated: round, rump, shin, thin flank, tenderloin, and rib. Of the total number of slaughtered animals, 68.26% had at least one type of bruise with complete removal of the affected tissue. There was an interaction effect between sex and temperament on the occurrence of bruises on the different cuts and on carcass yield. In castrated males, bruises on the round, rump, shin, and tenderloin cuts did not differ between temperament classes, but the excited males showed more bruises on the thin flank and rib cuts. Among the females, for all cuts, the number of bruises was higher (P<0.05) in those with excited temperament than in the anxious and calm animals, which did not differ (P>0.05). Additionally, carcass yield relative to plant weight decreased (P<0.05), with the calm females exhibiting the highest values, followed by those with anxious and excited temperament. In the castrated males, however, although performance declined, those with anxious and excited temperament did not differ (P>0.05). Females and more reactive animals have more bruises on their carcass.(AU)

O objetivo desta pesquisa foi avaliar os efeitos das diferenças comportamentais dos bovinos e seus reflexos nas contusões nos diferentes cortes e nos valores de rendimento de carcaça. Foram avaliados 4.061 lotes de bovinos, perfazendo 199.026 mil carcaças. O temperamento animal foi classificado em calmo, ansioso e excitado. Foram avaliados os cortes das carcaças divididas em coxa, alcatra, dianteiro e lombo, vazio e costela. Do total de lotes de animais abatidos, 68,26% apresentaram pelo menos um tipo de contusão com remoção completa do tecido afetado. Ocorreu interação entre o sexo e temperamento animal para os diferentes cortes na ocorrência de contusões e no rendimento de carcaça. Nos machos castrados as contusões dos cortes da coxa, alcatra, dianteiro e lombo não diferiram entre as classes de temperamento, tendo os animais agressivos mais contusões nos cortes do vazio e costela. Nas fêmeas em todos os cortes, as quantidades de contusões verificadas foram superiores (P<0,05) para animais com comportamento excitado do que animais ansiosos e calmos, não ocorrendo diferença entre os mesmos (P>0,05). O rendimento de carcaça em relação do peso de frigorífico quanto as classes comportamentais, nas fêmeas foi decrescente (P<0,05) com maiores valores para animais calmos, seguidos dos animais ansiosos e com menores rendimentos para animais com temperamento excitado, enquanto nos machos castrados, embora o rendimento tenha sido decrescente, animais com temperamento ansioso e excitado não diferiram (P>0,05). Carcaças oriundas de fêmeas e de animais com maior reatividade apresentam mais lesões.(AU)

COVID-19 and the beef market in Latin America: An impact assessment by supply and demand.

The impact of COVID-19 on agricultural markets, especially the beef market, represents one of the greatest food security challenges the world is facing in the post-pandemic era and, for this reason, has been widely documented. This study contributes to the literature through a comprehensive impact analysis of the effects of COVID-19 on both the demand and supply of beef in Latin America and thus provides valuable information for two of the most important links of the beef value chain. Robust econometric methods and a graphic analysis were used that give solidity to the investigation. The analysis used a data panel of supply and demand variables between 2018 and 2022 derived from the US Department of Agriculture. The results suggest that the beef market was strongly affected by the pandemic related health emergency, presenting decreases in both consumption and production. These effects are transitory, however, since the analysis of the post-pandemic data revealed that consumption and production return to normal and seem to grow until smoothing out over time.

Feeding strategy during growing phase on the performance and carcass traits in beef bulls finished on the pasture.

The objective of this study was to evaluate the performance, feed intake, carcass traits, and economic aspects of cattle fed different levels of supplementation during the growing phase (mineral supplementation-MS; low protein supplementation-PS, at 0.15% of body weight (BW); and a high protein-energy supplementation-PES at 0.40% of BW) and finished on the pasture with concentrate supplementation at 1.6% of BW. Ninety bulls were distributed in a completely randomized design and allocated into paddocks predominantly composed of Urochloa brizantha cv. Marandu grass. During the finishing phase, cattle were managed in paddocks of Urochloa decumbens grass. The average daily gain (ADG) and total weight gain during the growing phase were not different between animals fed PS (0.670 kg/day; 57.1 kg, respectively) and PES (0.730 kg/day; 62.4 kg, respectively), but both differed significantly from those supplemented with MS (0.540 kg/day; 45.1 kg). There was no difference between groups for average daily gain and total weight gain during the finishing phase (0.600 kg/day; 48.3 kg) and the same response was observed for carcass yield (55.18%, on average). However, bulls fed PES had higher hot carcass weight compared with those supplemented with MS and PS. Protein supplementation (0.15% of BW) and protein-energy supplementation (0.40% of BW) improved beef cattle performance during the growing phase. However, supplementation during the growing phase has a small impact on cattle performance in the finishing phase, although protein-energy supplementation at the growing phase improves the hot carcass weight and carcass traits during the finishing phase.

Evaluation of performance and carcass traits for a five-cohort All Heifer, No Cow beef production system demonstration herd.

The All Heifer, No Cow (AHNC) beef production system is an alternative to conventional cow/calf production that involves insemination of nulliparous heifers with sexed semen to produce female calves that are early weaned at 3 mo of age. Dams are finished on a high-concentrate diet and harvested before reaching 30 mo of age. Objectives of this research were to document reproductive, feedyard, calf, and carcass performance of an AHNC herd; evaluate effects of carcass maturity on carcass quality; and determine if performance of initial cohorts (i.e., cohorts 1 and 2) differed from sustaining cohorts (i.e., cohorts 3-5). A total of 272 heifers were enrolled in the AHNC system via five annual cohorts. The system was initiated with 51 yearling, Angus-based heifers, and a replicate set (n = 56) was started 12 mo after. Heifers in cohorts 3 (n = 53), 4 (n = 56), and 5 (n = 56) were primarily offspring of prior cohorts (i.e., cohort 3 heifers born to cohort 1 females), but some were purchased to maintain inventory. Angus replacement heifers were purchased in cohorts 3 (n = 26), 4 (n = 26), and 5 (n = 28). Mean (±standard deviation) pregnancy rate at 30 d after fixed-time artificial insemination (AI) with sexed semen was 50.8% ± 9.4%, and 140-d pregnancy rate was 93.0% ± 1.5%. With AHNC, 61.0% ± 6.5% of females replaced themselves with a heifer. During finishing, average daily gain (ADG) was 1.9 ± 0.4 kg • d-1 and dry matter intake (DMI) was 14.9 ± 1.9 kg • d-1. Hot carcass weight (HCW) was 367 ± 35 kg. The USDA grading system classified 20.5% of all carcasses (n = 220) as C maturity (A00 = 100, B00 = 200, etc.), 62.4% ± 29.1% of carcasses as USDA Choice. USDA yield grade (YG) was 2.6 ± 0.7. Based on cohorts 1 and 2, there were no differences (P = 0.96) in Warner-Bratzler shear force values between A and B maturity vs. C maturity carcasses. Across all cohorts, there were no differences in USDA YG, marbling score (MA), and lean maturity between A and B maturity vs. C maturity carcasses; there were differences in age (P < 0.001), bone maturity (P < 0.001), and overall maturity (P <0.001). A comparison of initial vs. sustaining cohorts showed that initial cohorts had lower (P < 0.001) DMI, heavier (P < 0.001) HCW, and more advanced (P < 0.05) bone maturity. However, there were no differences for 30- and 140-d pregnancy rates, ADG, USDA YG, and MA between initial and sustaining cohorts. The AHNC beef production system can effectively produce female calves and quality carcasses for harvest.

Protein-energy supplementation frequency on ruminal variables, intake and digestibility in steers receiving low quality hay / Frequência de suplementação proteico-energética sobre as variáveis ruminais, ingestão e digestibilidade em novilhos recebendo feno de baixa qualidade

The aim was evaluated the effect of reduce in protein-energy supplementation frequency on nutrients intake, forage digestibility and degradability, as well as, ruminal pH and ammonia nitrogen (N-NH3) concentration in beef cattle receiving low-quality hay. A 4 x 4 Latin square design were used. Four steers were fed with low-quality hay and subjected to four treatments: no supplementation (control); protein-energy supplementation with 0.82% of body weight (BW) offered three times per week (3WK); 0.49% of BW offered five times a week (5 WK), and 0.35% of BW offered seven times per week (7 WK). The use of protein-energy supplementation increased intake of dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), ether extract (EE), non-fibrous carbohydrates (NFC) and the digestibility coefficients of CP, EE, and NFC. However, no differences in DM and NDF degradation visit the website to get the how were observed between treatments in the evaluated hay. Supplementation did not alter ruminal pH, but the N-NH3 concentration was highest in treatment 7WK. Reduction in protein-energy supplementation frequency of daily to 3WK or 5WK does not negatively affect intake, digestibility and degradability of nutrients in beef cattle receiving low quality hay.

Objetivou-se avaliar o efeito da redução na frequência de suplementação proteico-energética sobre o consumo de nutrientes, degradabilidade e digestibilidade da forragem, assim como o pH e concentração de nitrogênio amoniacal (N-NH3) ruminal em bovinos de corte recebendo feno de baixa qualidade. Foi utilizado o delineamento quadrado latino de 4 x 4. Quatro bovinos foram alimentados com feno de baixa qualidade e submetidos aos seguintes tratamentos: sem suplementação (controle); suplementação com 0,82% do peso corporal (PC), três vezes por semana (3x); 0,49% do PC, cinco vezes por semana (5x); e 0,35% do PC sete vezes por semana (7x). O uso do suplemento proteico-energético aumentou a ingestão de matéria seca (MS), PB (proteína bruta), FDN (Fibra em detergente neutro), EE (extrato etéreo), CNF (carboidratos não fibrosos) e os coeficientes de digestibilidade da PB, EE e CNF. Entretanto, não foram observadas diferenças na degradação da MS e FDN do feno entre os tratamentos. A suplementação não alterou o pH ruminal, mas a concentração de nitrogênio amoniacal (N-NH3) foi maior no tratamento 7x. A redução na frequência de suplementação proteico-energética diária para 3x ou 5x não afetou negativamente o consumo, digestibilidade e degradabilidade dos nutrientes em bovinos de corte recebendo feno de baixa qualidade.

Protein-energy supplementation frequency on ruminal variables, intake and digestibility in steers receiving low quality hay / Frequência de suplementação proteico-energética sobre as variáveis ruminais, ingestão e digestibilidade em novilhos recebendo feno de baixa qualidade

The aim was evaluated the effect of reduce in protein-energy supplementation frequency on nutrients intake, forage digestibility and degradability, as well as, ruminal pH and ammonia nitrogen (N-NH3) concentration in beef cattle receiving low-quality hay. A 4 x 4 Latin square design were used. Four steers were fed with low-quality hay and subjected to four treatments: no supplementation (control); protein-energy supplementation with 0.82% of body weight (BW) offered three times per week (3WK); 0.49% of BW offered five times a week (5 WK), and 0.35% of BW offered seven times per week (7 WK). The use of protein-energy supplementation increased intake of dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), ether extract (EE), non-fibrous carbohydrates (NFC) and the digestibility coefficients of CP, EE, and NFC. However, no differences in DM and NDF degradation visit the website to get the how were observed between treatments in the evaluated hay. Supplementation did not alter ruminal pH, but the N-NH3 concentration was highest in treatment 7WK. Reduction in protein-energy supplementation frequency of daily to 3WK or 5WK does not negatively affect intake, digestibility and degradability of nutrients in beef cattle receiving low quality hay.(AU)

Objetivou-se avaliar o efeito da redução na frequência de suplementação proteico-energética sobre o consumo de nutrientes, degradabilidade e digestibilidade da forragem, assim como o pH e concentração de nitrogênio amoniacal (N-NH3) ruminal em bovinos de corte recebendo feno de baixa qualidade. Foi utilizado o delineamento quadrado latino de 4 x 4. Quatro bovinos foram alimentados com feno de baixa qualidade e submetidos aos seguintes tratamentos: sem suplementação (controle); suplementação com 0,82% do peso corporal (PC), três vezes por semana (3x); 0,49% do PC, cinco vezes por semana (5x); e 0,35% do PC sete vezes por semana (7x). O uso do suplemento proteico-energético aumentou a ingestão de matéria seca (MS), PB (proteína bruta), FDN (Fibra em detergente neutro), EE (extrato etéreo), CNF (carboidratos não fibrosos) e os coeficientes de digestibilidade da PB, EE e CNF. Entretanto, não foram observadas diferenças na degradação da MS e FDN do feno entre os tratamentos. A suplementação não alterou o pH ruminal, mas a concentração de nitrogênio amoniacal (N-NH3) foi maior no tratamento 7x. A redução na frequência de suplementação proteico-energética diária para 3x ou 5x não afetou negativamente o consumo, digestibilidade e degradabilidade dos nutrientes em bovinos de corte recebendo feno de baixa qualidade.(AU)

Genomic surveillance links livestock production with the emergence and spread of multi-drug resistant non-typhoidal Salmonella in Mexico.

Multi-drug resistant (MDR) non-typhoidal Salmonella (NTS) is increasingly common worldwide. While food animals are thought to contribute to the growing antimicrobial resistance (AMR) problem, limited data is documenting this relationship, especially in low and middle-income countries (LMIC). Herein, we aimed to assess the role of non-clinical NTS of bovine origin as reservoirs of AMR genes of human clinical significance. We evaluated the phenotypic and genotypic AMR profiles in a set of 44 bovine-associated NTS. For comparative purposes, we also included genotypic AMR data of additional isolates from Mexico (n = 1,067) that are publicly available. The most frequent AMR phenotypes in our isolates involved tetracycline (40/44), trimethoprim-sulfamethoxazole (26/44), chloramphenicol (19/44), ampicillin (18/44), streptomycin (16/44), and carbenicillin (13/44), while nearly 70% of the strains were MDR. These phenotypes were correlated with a widespread distribution of AMR genes (i.e. tetA, aadA, dfrA12, dfrA17, sul1, sul2, bla-TEM-1, blaCARB-2) against multiple antibiotic classes, with some of them contributed by plasmids and/or class-1 integrons. We observed different AMR genotypes for betalactams and tetracycline resistance, providing evidence of convergent evolution and adaptive AMR. The probability of MDR genotype occurrence was higher in meat-associated isolates than in those from other sources (odds ratio 11.2, 95% confidence interval 4.5-27.9, P < 0.0001). The study shows that beef cattle are a significant source of MDR NTS in Mexico, highlighting the role of animal production on the emergence and spread of MDR Salmonella in LMIC.

The phenotypic relationship between residual intake and gain and other feed efficiency traits in Nellore cattle.

This study aimed to compare feed efficiency measures of Nellore beef cattle on different residual intake and gain (RIG) classes. We used data from 610 animals weighing on average 236.33 kg and average of 283 days of age from feedlot performance tests carried out between 2005 and 2012. Animals were grouped based on RIG into three different classes: high RIG (> mean + 0.5 standard deviation (SD), most efficient; n = 193), medium RIG (mean ± 0.5 SD; n = 235), and low RIG (< mean - 0.5 SD, least efficient; n = 182). Residual feed intake (RFI), residual gain (RG), feed conversion ratio (FCR), feed efficiency (FE), relative growth rate (RGR), and Kleiber ratio (KR) of animals in each RIG class were compared by Tukey test at 1% of probability. Phenotypic correlations between variables were evaluated as well. Animals on high RIG class showed lower dry matter intake (P < 0.01) and higher average daily gain (P < 0.01) than low RIG animals. Consequently, high RIG animals had lower FCR (P < 0.01) and higher FE (P < 0.01) than those animals in low RIG class. The most efficient animals based on RIG were also the most efficient animals based on RG and RFI. RIG was negatively correlated to dry matter intake (P < 0.01) and FCR (P < 0.01), and a positive correlation was found between RIG and FE (P < 0.01). Therefore, RIG appears to be a good parameter to select animals with reduced dry matter intake and high productive performance.

Influences of nitrogen fertilization and energy supplementation for growth perfomance of beef cattle on Alexander grass.

This study evaluated the influences of nitrogen fertilizer and energy supplementation cattle on the growth performance of beef cattle. This study was conducted at the Federal University of Technology of Paraná, Dois Vizinhos through continuous grazing on 6.3 ha, divided into nine paddocks. The treatments were: Alexander grass +100 kg ha-1 of N (N100); Alexander grass + 100 kg ha-1 of N + 0.5 kg per 100 kg of weight live supplementation of wheat bran (N100S); and Alexander grass +200 kg ha-1 of N (N200), with an average herbage allowance of 10% for all treatments. Crossbred and non-castrated steers with an average weight of 276 ± 41 kg were used for 107 days. The crude protein from entire plant differed (P < 0.05) between treatments, with the greater value (14.8%) occurring in the N200, and the lesser value (13.3%) occurring in the N100S. The herbage accumulation rate was greater (P < 0.05) in the N200 (55.7  DM ha-1 d-1) than that in the N100S and N100 (40.0 and 39.7 kg DM ha-1 d-1, respectively). The N100S produced greater (P < 0.05) average daily weight gains (0.815 kg animal day-1) than did the N200 (0.685 kg animal day-1) and N100 treatments (0.727 kg animal day-1).

Land-use strategies to balance livestock production, biodiversity conservation and carbon storage in Yucatán, Mexico.

Balancing the production of food, particularly meat, with preserving biodiversity and maintaining ecosystem services is a major societal challenge. Research into the contrasting strategies of land sparing and land sharing has suggested that land sparing-combining high-yield agriculture with the protection or restoration of natural habitats on nonfarmed land-will have lower environmental impacts than other strategies. Ecosystems with long histories of habitat disturbance, however, could be resilient to low-yield agriculture and thus fare better under land sharing. Using a wider suite of species (birds, dung beetles and trees) and a wider range of livestock-production systems than previous studies, we investigated the probable impacts of different land-use strategies on biodiversity and aboveground carbon stocks in the Yucatán Peninsula, Mexico-a region with a long history of habitat disturbance. By modelling the production of multiple products from interdependent land uses, we found that land sparing would allow larger estimated populations of most species and larger carbon stocks to persist than would land sharing or any intermediate strategy. This result held across all agricultural production targets despite the history of disturbance and despite species richness in low- and medium-yielding agriculture being not much lower than that in natural habitats. This highlights the importance, in evaluating the biodiversity impacts of land use, of measuring population densities of individual species, rather than simple species richness. The benefits of land sparing for both biodiversity and carbon storage suggest that safeguarding natural habitats for biodiversity protection and carbon storage alongside promoting areas of high-yield cattle production would be desirable. However, delivering such landscapes will probably require the explicit linkage of livestock yield increases with habitat protection or restoration, as well as a deeper understanding of the long-term sustainability of yields, and research into how other societal outcomes vary across land-use strategies.

Prevalence and concentration of Escherichia coli O157 in different seasons and cattle types processed in North America: A systematic review and meta-analysis of published research.

Systematic review (SR) and meta-analyses (MA) methodologies were used to identify, critically evaluate and synthesize prevalence and concentration estimates for Escherichia coli O157 contamination along the beef production chain, and to illustrate differences based on cattle types and seasonality in North America from the scientific peer-reviewed literature. Four electronic databases were searched to identify relevant articles. Two independent reviewers performed all SR steps. Random effects MA models were used to estimate the pooled prevalence and concentration of E. coli O157 in feces, hides and carcasses of cattle processed in North America, including their seasonal estimates. The potential sources of between studies heterogeneity were identified using meta-regression and sub-group analysis. Results indicated differences in the fecal prevalence of E. coli O157 among cattle types: 10.68% (95% CI: 9.17-12.28%) in fed beef, 4.65% (95% CI: 3.37-6.10%) in adult beef, and 1.79% (95% CI: 1.20-2.48%) in adult dairy. Fed beef fecal prevalence was 10.65% (95% CI: 8.93-12.49%) during summer and 9.17% (95% CI: 5.24-13.98%) during the winter months. For adult beef, the fecal prevalence was 7.86% (95% CI: 5.43-10.66%) during summer, and 4.21% (95% CI: 1.95-7.13%) during winter. Among adult dairy, the fecal prevalence was 2.27% (95% CI: 1.5-3.18%) during summer, and 0.36% (95% CI: 0.09-0.74%) during winter. There was a significantly higher percentage of hides with E. coli O157 concentration ≥ 40 CFU/100 cm(2) on hides of fed beef sampled at the processing plant (23.81%; 95% CI: 14.79-34.15%) compared to those sampled at the feedlot (1.74%; 95% CI: 0.53-3.44%). Prevalence of E. coli O157 on carcass surfaces differed by season only at the post-evisceration stage, but decreased considerably through the subsequent processing stages. Country, study setting, detection method, hide swab area, and study design were identified as significant sources of heterogeneity among studies reporting prevalence of E. coli O157 along the beef production chain. The pooled prevalence and concentration estimates from this study provide a sound and reliable microbiological basis for risk assessment modeling of E. coli O157 and other pathogens in the food chain.

Growth and reproductive performance of beef heifers weaned at different ages / Desenvolvimento e desempenho reprodutivo de novilhas de corte submetidas a diferentes idades de desmame

The objective of the experiment was to evaluate the growth until twenty-eight months of age and the reproductive performance during the first mating at twenty- five months of beef females from two breeding systems, straightbreds (Charolais C and Nellore N) and crossbreds (1/2 CN, ½ NC), submitted to two ages of weaning: T3 weaning at three months; T7 weaning at seven months. After the weaning management heifers were kept only on pasture. The data collected were weights taken at three, four, seven, twelve, eighteen, twenty-four and twenty-eight months of age, average daily weight gain (ADG) between the different ages, body conditions at twenty-four and twenty-eight months, pelvic area and pregnancy rate. No significant interaction was observed for, the variables studied, between age at weaning and breeding system. ADG was lower for T3 calves from three to seven months (296 vs 434 g) and higher from seven to twelve months (541 vs 417 g), afterward no significant difference was observed between the two treatments. The only significant difference for weight was at seven months, when T7 calves showed higher weight (144 vs 128 kg). Weights at twenty-four months were 333 and 331 kg, respectively, for T3 and T7. Crossbred females showed higher weight gain from three to eighteen months and were heavier at twelve (11.73%), eighteen (17.10%), twenty-four (14.89%) and twenty-eight

O experimento teve como objetivo avaliar o desenvolvimento até os vinte e oito meses de idade e o desempenho reprodutivo no primeiro acasalamento aos vinte e cinco meses de fêmeas de dois sistemas de acasalamento, puras (Charolês C e Nelore N) e cruzadas (½ CN, ½ NC) submetidas a duas idades de desmame, sendo T3 desmame aos três meses de idade e T7 desmame aos sete meses de idade. Após o manejo do desmame, as fêmeas foram mantidas exclusivamente em condições de pastagem. Os dados avaliados foram os pesos ao nascer, aos três, sete, doze, dezoito, vinte e quatro e vinte e oito meses de idade, os ganhos de peso médios diários (GMD) entre as diferentes idades e a condição corporal aos vinte e quatro e vinte e oito meses de idade, área pélvica e percentagem de prenhez. Não houve interação significativa entre sistema de acasalamento e idade de desmame, para as variáveis estudadas. O GMD das fêmeas do T3 foi inferior dos três aos sete meses (296 contra 434 g), e superior dos sete aos doze meses (541 contra 417 g). Nas demais fases não houve diferença no GMD. A única diferença para peso mostrou-se aos sete meses, sendo superior para os animais do T7 (144 contra 128 kg). Os pesos aos vinte e quatro meses foram de 333 e 331 kg, respectivamente, para T3 e T7. As fêmeas cruzadas apresentaram maior ganho de peso dos três aos dezoito meses de idade e apresentando-se mais pesadas aos

GROWTH AND REPRODUCTIVE PERFORMANCE OF BEEF HEIFERS WEANED AT DIFFERENT AGES / DESENVOLVIMENTO E DESEMPENHO REPRODUTIVO DE NOVILHAS DE CORTE SUBMETIDAS A DIFERENTES IDADES DE DESMAME

The objective of the experiment was to evaluate the growth until twenty-eight months of age and the reproductive performance during the first mating at twenty- five months of beef females from two breeding systems, straightbreds (Charolais C and Nellore N) and crossbreds (1/2 CN, ½ NC), submitted to two ages of weaning: T3 weaning at three months; T7 weaning at seven months. After the weaning management heifers were kept only on pasture. The data collected were weights taken at three, four, seven, twelve, eighteen, twenty-four and twenty-eight months of age, average daily weight gain (ADG) between the different ages, body conditions at twenty-four and twenty-eight months, pelvic area and pregnancy rate. No significant interaction was observed for, the variables studied, between age at weaning and breeding system. ADG was lower for T3 calves from three to seven months (296 vs 434 g) and higher from seven to twelve months (541 vs 417 g), afterward no significant difference was observed between the two treatments. The only significant difference for weight was at seven months, when T7 calves showed higher weight (144 vs 128 kg). Weights at twenty-four months were 333 and 331 kg, respectively, for T3 and T7. Crossbred females showed higher weight gain from three to eighteen months and were heavier at twelve (11.73%), eighteen (17.10%), twenty-four (14.89%) and twenty-eight 

O experimento teve como objetivo avaliar o desenvolvimento até os vinte e oito meses de idade e o desempenho reprodutivo no primeiro acasalamento aos vinte e cinco meses de fêmeas de dois sistemas de acasalamento, puras (Charolês C e Nelore N) e cruzadas (½ CN, ½ NC) submetidas a duas idades de desmame, sendo T3 desmame aos três meses de idade e T7 desmame aos sete meses de idade. Após o manejo do desmame, as fêmeas foram mantidas exclusivamente em condições de pastagem. Os dados avaliados foram os pesos ao nascer, aos três, sete, doze, dezoito, vinte e quatro e vinte e oito meses de idade, os ganhos de peso médios diários (GMD) entre as diferentes idades e a condição corporal aos vinte e quatro e vinte e oito meses de idade, área pélvica e percentagem de prenhez. Não houve interação significativa entre sistema de acasalamento e idade de desmame, para as variáveis estudadas. O GMD das fêmeas do T3 foi inferior dos três aos sete meses (296 contra 434 g), e superior dos sete aos doze meses (541 contra 417 g). Nas demais fases não houve diferença no GMD. A única diferença para peso mostrou-se aos sete meses, sendo superior para os animais do T7 (144 contra 128 kg). Os pesos aos vinte e quatro meses foram de 333 e 331 kg, respectivamente, para T3 e T7. As fêmeas cruzadas apresentaram maior ganho de peso dos três aos dezoito meses de idade e apresentando-se mais pesadas aos

Study of polymorphic systems in Nelore cattle (Bos taurus indicus L.) associated with beef production. I. Hemoglobins: Weights and gain from birth to second parturition / Estudo de sistemas polimórficos em bovinos da raça Nelore (Bos taurus indicus L.) associados à produção de carne. I. Hemoglobinas: Pesos e ganho de peso, do nascimento ao segundo parto

A sample of 114 females, from the herds of the Zertaozinho"s Experiment Station (SP), maintained on range conditions, was used to observe the Castle-Hardy-Weingberg equilibrium for hemoglobin polymorphism. Another objective was to verify a possible relationship with growth traits like birth (PN), weaning (PD) and yearling weight (P18), gain from birth to weaning (GPND) and also 1st parturition (PAP1) and 2nd parturition (PAP2) weights. Statistical analyses were performed by least square means for unbalanced subclass numbers and the chi-square test was utilized to check the Castle-Hardy-Weinberg equilibrium. Adjusted means and standard errors for PN, PD, P18, PAP1, PAP2 and GPND were respectively: AA = 28,66 ± 1,39 kg; AB = 27,05 ± 1,27 kg; BB = 30,35 ± 2,82 kg; AA = 165,74 ± 6,11 kg; AB = 162,13 ± 5,62 kg; BB = 171,90 ± 12,42 kg; AA = 258,45 ± 6,74 kg; AB = 258,43 ± 6,20 kg; BB = 295,85 ± 13,71 kg; AA = 367,42 ± 9,71 kg; AB - 373,47 ± 8,97 kg; BB = 431,24 ± 19,77 kg; AA = 405,83 ± 17,85 kg; AB = 411,83 ± 16,38 kg; BB = 451,84 ± 34,37 kg; AA = 0,69 ± 0,02 kg; AB = 0,65 ± 0,02kg; BB = 0,75 ± 0,05 kg. The hemoglobin type influenced significantly the yearling weight and 1st parturition, and the highest means were for Hb-BB hemoglobin type. The phenotypic frequencies for the hemoglobin types were in equilibrium of Castle-Hardy-Weinberg.

Registros de 114 fêmeas da raça Nelore, criadas a pasto, pertencentes à Estação Experimental de Zootecnia de Sertãozinho, SP, filhas de 27 touros, foram analisadas com o objetivo de estudar as frequências observadas para tipos de hemoglobina, verificando-se o estado de equilíbrio de Castle-Hardy-Weinberg e procurando-se associar esses tipo de polimórficos com os pesos ao nascer (PN), ao desmame (PD), aos 18 meses de idade (P18, ao 1º parto (PAP1), ao 2º parto (PAP2) e o ganho de peso do nascimento aos 210 dias de idade (GPND). As análises estatísticas foram realizadas pelo método dos quadrados mínimos, com frequências desiguais das subclasses. Para verificar se as frequências estavam em equilíbrio de Castle-Hardy-Weinberg, utilizou-se o teste qui-quadradoo. As médias ajustadas ± erros padrões para PN, PD, P18, PAP1, PAP2 e GPND, por tipos hemoglobínicos, foram, respectivamente: AA = 28,66 ± 1,39 kg; AB = 27,05 ± 1,27 kg; BB = 30,35 ± 2,82 kg; AA = 165,74 ± 6,11 kg; AB = 162,13 ± 5,62 kg; BB = 171,90 ± 12,42 kg; AA = 258,45 ± 6,74 kg; AB = 258,43 ± 6,20 kg; BB = 295,85 ± 13,71 kg; AA = 367,42 ± 9,71 kg; AB - 373,47 ± 8,97 kg; BB = 431,24 ± 19,77 kg; AA = 405,83 ± 17,85 kg; AB = 411,83 ± 16,38 kg; BB = 451,84 ± 34,37 kg; AA = 0,69 ± 0,02 kg; AB = 0,65 ± 0,02kg; BB = 0,75 ± 0,05 kg. O tipo hemoglobínico influenciou significativamente o peso aos 18 meses de idade e o peso ao primei

Study of polymorphic systems in Nelore cattle (Bos taurus indicus L.) associated with beef production. I. Hemoglobins: Weights and gain from birth to second parturition / Estudo de sistemas polimórficos em bovinos da raça Nelore (Bos taurus indicus L.) associados à produção de carne. I. Hemoglobinas: Pesos e ganho de peso, do nascimento ao segundo parto

A sample of 114 females, from the herds of the Zertaozinho"s Experiment Station (SP), maintained on range conditions, was used to observe the Castle-Hardy-Weingberg equilibrium for hemoglobin polymorphism. Another objective was to verify a possible relationship with growth traits like birth (PN), weaning (PD) and yearling weight (P18), gain from birth to weaning (GPND) and also 1st parturition (PAP1) and 2nd parturition (PAP2) weights. Statistical analyses were performed by least square means for unbalanced subclass numbers and the chi-square test was utilized to check the Castle-Hardy-Weinberg equilibrium. Adjusted means and standard errors for PN, PD, P18, PAP1, PAP2 and GPND were respectively: AA = 28,66 ± 1,39 kg; AB = 27,05 ± 1,27 kg; BB = 30,35 ± 2,82 kg; AA = 165,74 ± 6,11 kg; AB = 162,13 ± 5,62 kg; BB = 171,90 ± 12,42 kg; AA = 258,45 ± 6,74 kg; AB = 258,43 ± 6,20 kg; BB = 295,85 ± 13,71 kg; AA = 367,42 ± 9,71 kg; AB - 373,47 ± 8,97 kg; BB = 431,24 ± 19,77 kg; AA = 405,83 ± 17,85 kg; AB = 411,83 ± 16,38 kg; BB = 451,84 ± 34,37 kg; AA = 0,69 ± 0,02 kg; AB = 0,65 ± 0,02kg; BB = 0,75 ± 0,05 kg. The hemoglobin type influenced significantly the yearling weight and 1st parturition, and the highest means were for Hb-BB hemoglobin type. The phenotypic frequencies for the hemoglobin types were in equilibrium of Castle-Hardy-Weinberg.

Registros de 114 fêmeas da raça Nelore, criadas a pasto, pertencentes à Estação Experimental de Zootecnia de Sertãozinho, SP, filhas de 27 touros, foram analisadas com o objetivo de estudar as frequências observadas para tipos de hemoglobina, verificando-se o estado de equilíbrio de Castle-Hardy-Weinberg e procurando-se associar esses tipo de polimórficos com os pesos ao nascer (PN), ao desmame (PD), aos 18 meses de idade (P18, ao 1º parto (PAP1), ao 2º parto (PAP2) e o ganho de peso do nascimento aos 210 dias de idade (GPND). As análises estatísticas foram realizadas pelo método dos quadrados mínimos, com frequências desiguais das subclasses. Para verificar se as frequências estavam em equilíbrio de Castle-Hardy-Weinberg, utilizou-se o teste qui-quadradoo. As médias ajustadas ± erros padrões para PN, PD, P18, PAP1, PAP2 e GPND, por tipos hemoglobínicos, foram, respectivamente: AA = 28,66 ± 1,39 kg; AB = 27,05 ± 1,27 kg; BB = 30,35 ± 2,82 kg; AA = 165,74 ± 6,11 kg; AB = 162,13 ± 5,62 kg; BB = 171,90 ± 12,42 kg; AA = 258,45 ± 6,74 kg; AB = 258,43 ± 6,20 kg; BB = 295,85 ± 13,71 kg; AA = 367,42 ± 9,71 kg; AB - 373,47 ± 8,97 kg; BB = 431,24 ± 19,77 kg; AA = 405,83 ± 17,85 kg; AB = 411,83 ± 16,38 kg; BB = 451,84 ± 34,37 kg; AA = 0,69 ± 0,02 kg; AB = 0,65 ± 0,02kg; BB = 0,75 ± 0,05 kg. O tipo hemoglobínico influenciou significativamente o peso aos 18 meses de idade e o peso ao primei

Qualitative and productive aspects of Napier grass postures either fertilized with nitrogen or mixed with tropical legumes to estimate beef production / Avaliação agronômica e qualitativa de pastos de capim elefante napier (pennisetum purpureum schum) fertilizados com nitrogênio ou consorciados com leguminosas tropicais para a produção de carne

In Napier grass (Pennisetum purpureum Schum) experimental pastures fertilized with four levels of Nitrogen; 0,50, 100 and 150kg/ha and used for beef gain,measures of acessible green dry matter, stand height and hand-plucking samples were taken at 28 days intervals at the same time of animals weighing days. O N pastures were mixed with tropical legumes (centrosema pubescens Benthe, Macroptilium atropurpureum D.C. cv. Siratro e Galactia striata Jacq.). Proximate analysis and in vivo dry matter digestibilities were performed to evaluate forage quality. Among several measures or calculated values, the conclusions were: 1- Acessible Green Dry Matter was significantly affected by Nitrogen level (P 0.01); 2- Stocking rate expressed in kg of liveweight/ha was affected by Acessible Green Dry Matter (R2 = 0.626); 3- Percentage of Crude Protein in hand-plucking samples was not affected either by nitrogen level or by season of the year (the average was 14.5% ± 1.85); 4- Acessible Green Dry Matter/100 kg LW averaged 5.8 kg throughout the experimental periods; 5- Napier grass gave gains above 0.50 ka/day when the pastures height varied between 0.50 to 10m. Combining some of those parameters we could prepare a guide for managing Napier grass pastures for beef production.

Em pastos experimentais de capim elefante Napier (Pennisetum purpureum Schum), fertilizados com níveis crescentes de N (0, 50,100 e 150 kg/ha) para medir produção de carne. foram efetuadas medidas agronômicas e qualitativas, durante dois anos, na tentativa de estabelecer parâmetros comparativos com essa produção. Os pastos com nível de 0 de N eram consorciados com leguminosas tropicais centrosema pubescens Benthe, Macroptilium atropurpureum D.C. cv. Siratro e Galactia striata Jacq.. A cada 28 dias, em coincidência com a pesagem dos animais, ou a cada mudança de piquete eram efetuadas as seguintes medidas: corte com tesoura de área sorteada, para estimar a Matéria Verde Seca Acessível (MVSA), amostra seletiva de toda área pastada, com a mão, para avaliar a qualidade, altura média do pasto por ocasião do corte. A qualidade foi avaliada através de análise aproximada e da digestibilidade in vitro. Da combinação de dados quantitativos e qualitativos, foram obtidos diversos parâmetros que pudessem indicar relações de causa e efeito entre pasto e produção animal. Entre eles destacam-se os seguintes: 1- A MVSA, foi afetada de forma significativa (P 0,01) pelos níveis de N; 2- A lotação expressa em kg de peso vivo/ha foi afetada pela produção de MVSA (R2 = 0,626); 3-A % de Proteína Bruta das Amostras coletadas à mão, não variou de forma significativa entre tratamentos ou entre esta

Qualitative and productive aspects of Napier grass postures either fertilized with nitrogen or mixed with tropical legumes to estimate beef production / Avaliação agronômica e qualitativa de pastos de capim elefante napier (pennisetum purpureum schum) fertilizados com nitrogênio ou consorciados com leguminosas tropicais para a produção de carne

In Napier grass (Pennisetum purpureum Schum) experimental pastures fertilized with four levels of Nitrogen; 0,50, 100 and 150kg/ha and used for beef gain,measures of acessible green dry matter, stand height and hand-plucking samples were taken at 28 days intervals at the same time of animals weighing days. O N pastures were mixed with tropical legumes (centrosema pubescens Benthe, Macroptilium atropurpureum D.C. cv. Siratro e Galactia striata Jacq.). Proximate analysis and in vivo dry matter digestibilities were performed to evaluate forage quality. Among several measures or calculated values, the conclusions were: 1- Acessible Green Dry Matter was significantly affected by Nitrogen level (P 0.01); 2- Stocking rate expressed in kg of liveweight/ha was affected by Acessible Green Dry Matter (R2 = 0.626); 3- Percentage of Crude Protein in hand-plucking samples was not affected either by nitrogen level or by season of the year (the average was 14.5% ± 1.85); 4- Acessible Green Dry Matter/100 kg LW averaged 5.8 kg throughout the experimental periods; 5- Napier grass gave gains above 0.50 ka/day when the pastures height varied between 0.50 to 10m. Combining some of those parameters we could prepare a guide for managing Napier grass pastures for beef production.

Em pastos experimentais de capim elefante Napier (Pennisetum purpureum Schum), fertilizados com níveis crescentes de N (0, 50,100 e 150 kg/ha) para medir produção de carne. foram efetuadas medidas agronômicas e qualitativas, durante dois anos, na tentativa de estabelecer parâmetros comparativos com essa produção. Os pastos com nível de 0 de N eram consorciados com leguminosas tropicais centrosema pubescens Benthe, Macroptilium atropurpureum D.C. cv. Siratro e Galactia striata Jacq.. A cada 28 dias, em coincidência com a pesagem dos animais, ou a cada mudança de piquete eram efetuadas as seguintes medidas: corte com tesoura de área sorteada, para estimar a Matéria Verde Seca Acessível (MVSA), amostra seletiva de toda área pastada, com a mão, para avaliar a qualidade, altura média do pasto por ocasião do corte. A qualidade foi avaliada através de análise aproximada e da digestibilidade in vitro. Da combinação de dados quantitativos e qualitativos, foram obtidos diversos parâmetros que pudessem indicar relações de causa e efeito entre pasto e produção animal. Entre eles destacam-se os seguintes: 1- A MVSA, foi afetada de forma significativa (P 0,01) pelos níveis de N; 2- A lotação expressa em kg de peso vivo/ha foi afetada pela produção de MVSA (R2 = 0,626); 3-A % de Proteína Bruta das Amostras coletadas à mão, não variou de forma significativa entre tratamentos ou entre esta