BackgroundFeed intake plays an important economic role in beef cattle, and is related with feed efficiency, weight gain and carcass traits. However, the phenotypes collected for dry matter intake and feed efficiency are scarce when compared with other measures such as weight gain and carcass traits. The use of genomic information can improve the power of inference of studies on these measures, identifying genomic regions that affect these phenotypes. This work performed the genome-wide association study (GWAS) for dry matter intake (DMI) and residual feed intake (RFI) of 720 Nellore cattle (Bos taurus indicus).ResultsIn general, no genomic region extremely associated with both phenotypic traits was observed, as expected for the variables that have their regulation controlled by many genes. Three SNPs surpassed the threshold for the Bonferroni multiple test for DMI and two SNPs for RFI. These markers are located on chromosomes 4, 8, 14 and 21 in regions near genes regulating appetite and ion transport and close to important QTL as previously reported to RFI and DMI, thus corroborating the literature that points these two processes as important in the physiological regulation of intake and feed efficiency.ConclusionsThis study showed the first GWAS of DMI to identify genomic regions associated with feed intake and efficiency in Nellore cattle. Some genes and QTLs previously described for DMI and RFI, in other subspecies (Bos taurus taurus), that influences these phenotypes are confirmed in this study.
RESUMO -Este trabalho foi realizado, no verão de 2002, com o objetivo de avaliar a influência de alguns recursos de climatização na produção de leite e na termorregulação dos animais. Foram utilizadas 10 primíparas e 17 multíparas em lactação, distribuídas em instalação controle (ICO), instalação com nebulizador associado a ventiladores (ICL) e instalação com tela de sombreamento (IT). A produção de leite e o consumo individual foram medidos diariamente para cada animal. A temperatura retal foi medida três vezes ao dia, em três animais de cada instalação; a temperatura de superfície da pele, três vezes ao dia em todos os animais; e a freqüência respiratória, duas vezes ao dia em todos os animais. Os dados climáticos de cada instalação foram registrados e posteriormente calculados os índices de temperatura e umidade (ITU) e de globo negro e umidade (ITGU). Foram selecionados e analisados 26 dias com entalpia elevada. O ITU entre 75 e 76, apesar de considerado estressante por diversas fontes da literatura, não foi associado à condição de estresse pelos animais. As multíparas da instalação climatizada apresentaram freqüência respiratória e temperatura de pele significativamente menor em relação às multíparas das demais instalações. As primíparas apresentaram freqüências respiratórias e temperaturas retais mais altas que as multíparas, nos horários mais quentes do dia. A maior produção de leite das multíparas foi observada no tratamento com tela.Palavras-chave: estresse térmico, produção de leite, sistema de nebulização, temperatura retal, termorregulação Physiologic and Performance Responses of Holstein Cows in Milking under Different EnvironmentsABSTRACT -This work was carried out during the summer of 2002 to evaluate the influence of some cooling systems on the milk yield and animal thermoregulation. Ten heifers and seventeen milking cows were assigned to the control housing (ICO), mist & fan housing (ICL) and shade cloth (80%) (IT). The milk yield and the individual intake were daily measured for each animal. The rectal temperature was measured three times a day with three animals from each treatment. The skin surface temperature was collected three times a day for all the animals and the respiratory frequency two times a day for all the animals. The climatic data of each housing were registered to calculate the temperature humidity index (ITU) and the black globe humidity index (ITGU). Twenty six days of high enthalpy were selected and analyzed. The study showed that temperature humidity index from 75 to 76 was not associated with stress conditions for the animals, although many researches propose this situation as stressing. The milking cows in the mist & fan treatment showed respiratory frequency and skin surface temperature significantly lower than the cows in the other treatments. The heifers presented respiratory frequency and rectal temperature higher than the cows in all the registration times. The higher milk yield of the cows was observed in the shade cloth treatment.Key Words: heat stress, milk produc...
This study was conducted to evaluate the effects of flint corn processing method (CPM) and level of NDF from roughage (rNDF) on performance, carcass characteristics, and starch utilization by finishing Nellore-based cattle fed high-concentrate, flint corn-based diets. In this study, 112 Nellore type bulls (initial BW 384.07 ± 29.53 kg and 24-36 mo of age) were individually fed using Calan gates or individual pens. The animals were used in a randomized complete block design in a 2 × 4 factorial arrangement with 2 CPM, high-moisture flint corn (HMC) or finely ground dry flint corn (FGC), with 1 of 4 levels of rNDF, 3, 8, 13, and 18% (DM basis), using sugarcane silage (SS) as roughage. Bulls were adapted to the finishing diet over a 21-d period and fed for a total of 81 d. Fecal starch (FS) concentration was determined on d 46 and 74 of the feeding period. There was a quadratic effect of rNDF on final BW (P < 0.01) and ADG (P = 0.01). Optimal concentrations of rNDF were estimated using the first derivative of second order polynomials, indicating that final BW and ADG were maximized with 13.3 and 13.0% rNDF, respectively. An interaction was observed between CPM and rNDF (P = 0.05) for DMI, with peak DMI occurring at 11.3 and 13.7% rNDF with FGC and HMC, respectively. Cattle fed HMC had 13.9% greater G:F (P < 0.01) compared with those fed FGC (0.172 vs. 0.151, respectively). There were quadratic effects of rNDF on HCW (P = 0.04) and ME intake (P < 0.01); heaviest carcass weights were estimated, in both cases, to be achieved with 12.8% rNDF. A quadratic effect of rNDF for renal, pelvic, and inguinal fat weight (P = 0.04) was observed, with a peak estimated to occur at 12.6% rNDF. An interaction between CPM and rNDF also was observed for FS (P < 0.05). Bulls fed FGC with 3% rNDF had greater FS content, and FS linearly decreased as concentration of rNDF increased. For bulls fed HMC, FS was 3.0% of DM and was unaffected by rNDF in the diet. Lower FS from bulls fed HMC suggests that availability of starch from flint corn was greater than that of FGC. For Nellore-based cattle fed a flint corn-based diet containing SS and 8% whole lint cottonseed, performance was optimized with 12.8% rNDF. In the absence of cottonseed addition to diets, optimal performance would be expected with about 14.5% rNDF.
Fresh meat quality is greatly determined through biochemical changes occurring in the muscle during its conversion to meat. These changes are key to imparting a unique set of characteristics on fresh meat, including its appearance, ability to retain moisture, and texture. Skeletal muscle is an extremely heterogeneous tissue composed of different types of fibers that have distinct contractile and metabolic properties. Fiber type composition determines the overall biochemical and functional properties of the muscle tissue and, subsequently, its quality as fresh meat. Therefore, changing muscle fiber profile in living animals through genetic selection or environmental factors has the potential to modulate fresh meat quality. We provide an overview of the biochemical processes responsible for the development of meat quality attributes and an overall understanding of the strong relationship between muscle fiber profile and meat quality in different meat species. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 9 is February 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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