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Dietary protein adjustments can reduce environmental impact and economic losses in production systems. However, we lack information regarding nitrogen (N) metabolism and protein requirements for maintenance of crossbred animals such as Red Norte breed, precluding a precise dietary management. The objective was to evaluate the effect of increasing dietary CP levels (9%, 11%, 13%, 15% and 17%) on intake, digestibility and N balance, as well as to estimate the metabolizable protein requirements for maintenance (MPm) of growing Red Norte bulls. Thirty five animals averaging 280 ± 4.0 kg BW were fed during 45 days in a 60 : 40 forage : concentrate ratio diet in which the last 5 days were used for the digestibility trial. Intakes of CP and non-fibrous carbohydrates (NFCs) and feed efficiency linearly increased (P < 0.05) as CP levels increased, while DM, NDF, nitrogen efficiency use and ether extract were not influenced by CP levels (P > 0.05). Digestibilities of DM, organic matter, ether extract, NFC and CP as well as metabolizable energy intake linearly increased (P < 0.05), and true digestibility of CP was not affected (P > 0.05) by treatments. Urinary N and retained N linearly increased (P < 0.05) with the increase in dietary N. The MPm were estimated as 4.46 g/BW0.75 and the efficiency of use of MPm was 0.673. In conclusion, obtained MPm requirements of growing Red Norte bulls are greater than the values reported in literature for Zebu cattle and dietary CP levels of 15% and 17% exhibited great responses for growing Red Norte cattle. However, a cost-benefit evaluation should be done before its use.
The transition from laminar to turbulent flows has challenged the scientific community since the seminal work of Reynolds (Phil. Trans. R. Soc. Lond. A, vol. 174, 1883, pp. 935–982). Recently, experimental and numerical investigations on this matter have demonstrated that the spatio-temporal dynamics that are associated with transitional flows belong to the directed percolation class. In the present work, we explore the analysis of laminar–turbulent transition from the perspective of the recent theoretical development that concerns viscoelastic turbulence, i.e. the drag-reducing turbulent flow obtained from adding polymers to a Newtonian fluid. We found remarkable fingerprints of the variety of states that are present in both types of flows, as captured by a series of features that are known to be present in drag-reducing viscoelastic turbulence. In particular, when compared to a Newtonian fully turbulent flow, the universal nature of these flows includes: (i) the statistical dynamics of the alternation between active and hibernating turbulence; (ii) the weakening of elliptical and hyperbolic structures; (iii) the existence of high and low drag reduction regimes with the same boundary; (iv) the relative enhancement of the streamwise-normal stress; and (v) the slope of the energy spectrum decay with respect to the wavenumber. The maximum drag reduction profile was attained in a Newtonian flow with a Reynolds number near the boundary of the laminar regime and in a hibernating state. It is generally conjectured that, as the Reynolds number increases, the dynamics of the intermittency that characterises transitional flows migrate from a situation where heteroclinic connections between the upper and the lower branches of solutions are more frequent to another where homoclinic orbits around the upper solution become the general rule.
Many school-based interventions for obesity prevention have been proposed with positive changes in behaviour, but with unsatisfactory results on weight change. The objective was to verify the effectiveness of a combined school- and home-based obesity prevention programme on excessive weight gain in adolescents. Teachers delivered the school-based primary prevention programme to fifth- and sixth-graders (nine schools, forty-eight control classes, forty-nine intervention classes), which included encouraging healthy eating habits and physical activity. A subgroup of overweight or obese adolescents also received a home-based secondary prevention programme delivered by community health professionals. Schools were randomised to intervention or control group. Intent-to-treat analysis used mixed models for repeated continuous measures and considered the cluster effect. The main outcomes were changes in BMI and percentage body fat (%body fat) after one school-year of intervention and follow-up. Against our hypothesis, BMI increased more in the intervention group than in the control group (Δ = 0·3 kg/m2; P = 0·05) with a greater decrease in %body fat among boys (Δ = –0·6 %; P = 0·03) in the control group. The intervention group increased physical activity by 12·5 min per week compared with the control group. Female adolescents in the intervention group ate healthier items more frequently than in the control group. The subgroup that received both the school and home interventions had an increase in %body fat than in the control group (Δ = 0·89 %; P = 0·01). In the present study, a behavioural change led to a small increase in physical activity and healthy eating habits but also to an overall increase in food intake.
Vitamins play an essential role in broiler nutrition. They are fundamental for normal metabolic and physiological process, and their requirements for poultry are not fixed and can be affected by multiple factors. In contrast, mycotoxins are a challenging issue because they hinder performance and the immune system. Vitamin supplementation above minimum requirements would permit improvement in productive potential, health, bone and meat quality in a situation of mycotoxin challenge. The objective of this study was to determine the influence of optimum vitamin nutrition in diets contaminated with aflatoxin in broilers from 1 to 44 days of age. A total of 1800 Cobb 500 male chicks were randomized to 15 sets of eight treatment groups, each containing 15 birds using a 2 × 2 × 2 factorial design (commercial vitamin levels and high vitamin levels, two levels of aflatoxin – 0 and 0.5 ppm with binder levels of 0 and 10 000 mg/kg). The mash diets were corn and soybean meal based, formulated according to commercial practices. Feed intake, weight gain and feed conversion were analyzed for birds from 1 to 44 days of age. To determine carcass characteristics (carcass yield, breast yield and leg yield) and black bone syndrome, two birds were slaughtered from each group at 45 days. Other analyses included breast tenderness, water loss by dripping and malonaldehyde concentrations. The results demonstrated that broilers that were fed high levels of vitamins showed better weight gain, feed conversion, carcass yield and breast yield than broilers that were fed diets with commercial vitamin levels (P < 0.05); also, broilers that were fed diets containing 0.5 ppm aflatoxin had lower weight gain, carcass yield and breast yield (P < 0.05). The use of 10 000 mg/kg of binder improved (P < 0.05) feed conversion throughout the rearing period. We conclude that aflatoxin negatively affects performance and carcass yield; however, feeding optimum vitamin nutrition improved these performance traits.
Intake, digestibility, nitrogen (N) balance, microbial protein synthesis, weight gain, yields of the main commercial cuts and carcass morphometric measurements were evaluated in lambs fed diets containing different levels of chitosan. Sixty Santa Inês crossbred sheep with an average body weight (BW) of 24 ± 2.2 kg were assigned to three treatments (diets containing 0, 136 or 272 mg chitosan/kg BW) in a completely randomized design. There was no effect of chitosan on dry matter (DM) intake. Ingested and retained N showed a quadratic response, with the highest values estimated at the chitosan levels of 142 and 152 mg/kg BW, respectively. Similar to N balance, microbial protein synthesis showed the same quadratic response, in which the level of 136 mg/kg BW resulted in higher synthesis when compared with the other levels. No effect of chitosan was detected on average daily gain, final weight, or carcass variables (hot carcass weight, cold carcass weight, yield of commercial cuts and morphometric measurements of the carcass). Conformation, visceral fat content and fatness of carcasses were also not altered by the use of chitosan. Chitosan improves the digestibility of DM, crude protein and neutral detergent fibre, and increases N balance and microbial protein synthesis but does not change the production performance of feedlot lambs.
An experiment was conducted to evaluate whether dietary reduction and sex class affect nutrient intake, digestibility, purine derivative (PD) excretion and heat tolerance coefficient in lambs. Thirty-five hair lambs (14.5 ± 0.89 kg initial body weight (BW), 2 months old) were used in a completely randomized study with a 3 × 3 factorial arrangement, three sex classes (11 intact males, 12 castrated males and 12 females) and three levels of feeding (ad libitum, 300 and 600 g/kg/dry matter (DM) feed restriction) for 120 days. Intact and castrated males showed higher intakes of DM and neutral detergent fibre corrected for ash and protein (NDFap) than females. At 300 g/kg/DM feed restriction, NDFap digestibility was lower in intact males than in other classes; however, no differences were found between classes when subjected to ad libitum feeding or 600 g/kg/DM. The basal endogenous nitrogen and endogenous urinary losses were highest in intact males. Allantoin, uric acid and PD excretion, as well as PD absorption and microbial protein production were lowest in the animals subjected to 600 g/kg/DM feed restriction. Microbial protein synthesis (MPS) was highest in animals subjected to 600 g/kg/DM feed restriction. The lowest temperatures were observed in animals subjected to 600 g/kg/DM feed restriction. The heat tolerance coefficient was highest in animals subjected to 600 g/kg/DM feed restriction. In conclusion, feed restriction reduced the time spent on feeding and rumination but increased the digestibility of DM. The restriction level of 600 g/kg/DM maximized MPS and infrared thermography indicated an elevated heat tolerance coefficient.
Moringa oleifera seeds are currently being used as a livestock feed across tropical regions of the world due to its availability and palatability. However, limited knowledge exists on the effects of the raw seeds on ruminant metabolism. As such, the rumen stimulation technique was used to evaluate the effects of substituting increasing concentrations of ground Moringa seeds (0, 100, 200 and 400 g/kg concentrate dry matter (DM)) in the diet on rumen fermentation and methane production. Two identical, Rusitec apparatuses, each with eight fermenters were used with the first 8 days used for adaptation and days 9 to 16 used for measurements. Fermenters were fed a total mixed ration with Urochloa brizantha as the forage. Disappearance of DM, CP, NDF and ADF linearly decreased (P<0.01) with increasing concentrations of Moringa seeds in the diet. Total volatile fatty acid production and the acetate to propionate ratio were also linearly decreased (P<0.01). However, only the 400 g/kg (concentrate DM basis) treatment differed (P<0.01) from the control. Methane production (%), total microbial incorporation of 15N and total production of microbial N linearly decreased (P<0.01) as the inclusion of Moringa seeds increased. Though the inclusion of Moringa seeds in the diet decreased CH4 production, this arose from an unfavourable decrease in diet digestibility and rumen fermentation parameters.
Minerals are limiting factors in animal production, and the knowledge of mineral requirements for livestock is crucial to the success of a commercial enterprise. Hair sheep may have different mineral requirements than those presents by the international committees. A study was carried to evaluate the net calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na), potassium (K), zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) requirements for the growth and maintenance of Brazilian Somali lambs. A total of 48 hair lambs (13.5±1.8 kg) aged 60±15 days were allocated to individual pens. Eight animals were slaughtered at the beginning of the experiment to serve as a reference group to estimate initial empty BW (EBW) and initial body composition. The remaining lambs (n=40) were assigned to a completely randomized design with eight replications in five levels of metabolizable energy (ME; 4.93, 8.65, 9.41, 10.12 and 11.24 MJ/kg DM). When the lambs of a given treatment reached an average BW of 28 kg, they were slaughtered. Initial body composition was used to calculate the retention of minerals. Mineral body composition was fit using a logarithmic equation in the form of a nonlinear model. The maintenance requirements were estimated from regressions of mineral retention in the empty body on mineral intake. The body mineral concentration decreased in lambs with a BW ranging from 15 to 30 kg. The net mineral requirements (100 g/day of average daily gain (ADG)) decreased from 0.52 to 0.51 g for Ca, 0.28 to 0.23 g for P, 0.02 to 0.02 g for Mg, 0.09 to 0.08 g for Na, 0.11 to 0.09 g for K, 1.30 to 1.08 mg for Zn, 3.77 to 3.22 mg for Fe, 0.08 to 0.06 mg for Mn and 0.09 to 0.08 mg for Cu when BW increased from 15 to 30 kg. The daily net requirements for maintenance per kilogram of BW were 30.13 mg of Ca, 27.58 mg of P, 1.26 mg of Mg, 4.12 mg of Na, 8.11 mg of K, 0.133 mg of Zn, 0.271 mg of Fe, 0.002 mg of Mn and 0.014 mg of Cu. The results of this study indicate that the net mineral requirements for weight gain and maintenance in Brazilian Somali lambs are different than the values that are commonly recommended by the main evaluation systems for feed and nutritional requirements for sheep. These results for the nutritional requirements of minerals may help to optimize mineral supply for hair sheep.
This study evaluated the effects of diet containing taro flour on hormone levels and the seminiferous tubules morphology of rats. After weaning, the male rats were divided into two groups (n=12 each): control group (CG) treated with control diet and taro group (TG), fed with 25% taro flour for 90 days. Food, caloric intake, mass and body length were evaluated at experiment end. Testis followed the standard histological processing. Immunostaining was performed using an anti-vimentin antibody to identify Sertoli cells. In histomorphometry, total diameter, total area, epithelial height, luminal height and luminal area were analyzed. The testosterone levels were performed using the radioimmunoassay method. Group TG presented (P<0.05): increase in mass, body length, testicular weight, histomorphometric parameters and hormonal levels. Food intake, calorie and Sertoli cells not presented statistical differences. The taro promoted increase in the testicles parameters and hormones.
The olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is a key-pest in the main olives producing areas worldwide, and displays distinct preference to different olive cultivars. The present work intended to study oviposition preference towards three Portuguese cultivars (Cobrançosa, Madural, and Verdeal Transmontana) at different maturation indexes. Multiple oviposition bioassays (multiple-choice and no-choice) were conducted to assess cultivar preference. No-choice bioassays were conducted to assess the influence of different maturation indexes (MI 2; MI 3, and MI 4) in single cultivars. The longevity of olive fly adults according to the cultivar in which its larvae developed was also evaluated through survival assays.
Cultivar and maturation are crucial aspects in olive fly preference. Field and laboratory assays revealed a preference towards cv. Verdeal Transmontana olives and a lower susceptibility to cv. Cobrançosa olives. A higher preference was observed for olives at MI 2 and MI 3. The slower maturation process in cv. Verdeal Transmontana (still green while the other cultivars are reddish or at black stage) seems to have an attractive effect on olive fly females, thus increasing its infestation levels. Olive fly adults from both sexes live longer if emerged from pupae developed from cv. Verdeal Transmontana fruits and live less if emerged from cv. Cobrançosa. Therefore, olive cultivar and maturation process are crucial aspects in olive fly preference, also influencing the longevity of adults.
The present study aimed to (i) assess the appetitive drives evoked by the visual cues of ultra-processed food and drink products and (ii) investigate whether text warnings reduce appetitive drives and consumers’ reported intentions to eat or drink ultra-processed products.
In Study I, a well-established psychometric tool was applied to estimate the appetitive drives associated with ultra-processed products using sixty-four image representations. Sixteen product types with four exemplars of a given product were included. Pictures from the International Affective Picture System (IAPS) served as controls. The two exemplars of each product type rated as more appetitive were selected for investigation in the second study. Study II assessed the impact of textual warnings on the appetitive drive towards these thirty-two exemplars. Each participant was exposed to two picture exemplars of the same product type preceded by a text warning or a control text. After viewing each displayed picture, the participants reported their emotional reactions and their intention to consume the product.
Controlled classroom experiments
Undergraduate students (Study I: n 215, 135 women; Study II: n 98, 52 women).
In Study I, the pictures of ultra-processed products prompted an appetitive motivation associated with the products’ nutritional content. In Study II, text warnings were effective in reducing the intention to consume and the appetitive drive evoked by ultra-processed products.
This research provides initial evidence favouring the use of text warnings as a public policy tool to curb the powerful influence of highly appetitive ultra-processed food cues.
The physical processes driving the chemical evolution of galaxies in the last ~ 11Gyr cannot be understood without directly probing the dust-obscured phase of star-forming galaxies and active galactic nuclei. This phase, hidden to optical tracers, represents the bulk of the star formation and black hole accretion activity in galaxies at 1 < z < 3. Spectroscopic observations with a cryogenic infrared observatory like SPICA, will be sensitive enough to peer through the dust-obscured regions of galaxies and access the rest-frame mid- to far-infrared range in galaxies at high-z. This wavelength range contains a unique suite of spectral lines and dust features that serve as proxies for the abundances of heavy elements and the dust composition, providing tracers with a feeble response to both extinction and temperature. In this work, we investigate how SPICA observations could be exploited to understand key aspects in the chemical evolution of galaxies: the assembly of nearby galaxies based on the spatial distribution of heavy element abundances, the global content of metals in galaxies reaching the knee of the luminosity function up to z ~ 3, and the dust composition of galaxies at high-z. Possible synergies with facilities available in the late 2020s are also discussed.
Two single-nucleotide polymorphisms (SNPs) (rs4281084 and rs12155594) within the neuregulin-1 (NRG1) gene have been associated with psychosis transition. However, the neurobiological changes associated with these SNPs remain unclear. We aimed to determine what relationship these two SNPs have on lateral ventricular volume and white matter integrity, as abnormalities in these brain structures are some of the most consistent in schizophrenia.
Structural (n = 370) and diffusion (n = 465) magnetic resonance imaging data were obtained from affected and unaffected individuals predominantly of European descent. The SNPs rs4281084, rs12155594, and their combined allelic load were examined for their effects on lateral ventricular volume, fractional anisotropy (FA) as well as axial (AD) and radial (RD) diffusivity. Additional exploratory analyses assessed NRG1 effects on gray matter volume, cortical thickness, and surface area throughout the brain.
Individuals with a schizophrenia age of onset ⩽25 and a combined allelic load ⩾3 NRG1 risk alleles had significantly larger right (up to 50%, padj = 0.01) and left (up to 45%, padj = 0.05) lateral ventricle volumes compared with those with allelic loads of less than three. Furthermore, carriers of three or more risk alleles, regardless of age of onset and case status, had significantly reduced FA and elevated RD but stable AD in the frontal cortex compared with those carrying fewer than three risk alleles.
Our findings build on a growing body of research supporting the functional importance of genetic variation within the NRG1 gene and complement previous findings implicating the rs4281084 and rs12155594 SNPs as markers for psychosis transition.
The objective of this study was to evaluate the effects of the energy restriction of gestation of adult ewes from day 45 to day 115 on lamb live performance parameters, carcass and meat traits. In experiment I, dietary energy was restricted at 70% of the metabolizable energy (ME) requirements, after which ewes were re-fed ad libitum until lambing. In experiment II, dietary energy was restricted at 60% of the ME requirements, and ewes were re-fed to ME requirements until lambing. All ewes grazed together from the end of the restriction periods to weaning. Lambs were weaned and lot fed until slaughter. Feed intake, weight gain and feed efficiency were recorded, and body fat thickness and ribeye area (REA) were measured in the longissimus thoracis muscle. After slaughter, carcass weight and yield, fat depth, carcass and leg length, and frenched rack and leg weights and yields were determined. Muscle fiber type composition, Warner-Bratzler shear force, pH and color were determined in the longissimus lumborum muscle. In experiment I, energy restriction followed by ad libitum feeding affected lamb birth weight (P<0.05); however, no effects (P>0.05) were observed on later BW, REA, BF or carcass traits. Lambs born to non-restricted-fed ewes had higher (P<0.05) weight and yield of the frenched rack cut and their meat tended (P=0.11) to be tender compared with that of lambs from restricted ewes. The percentage of oxidative muscle fibers was lower for lambs born to non-restricted ewes (P<0.05); however, no effects of ewe treatment were observed on other muscle fiber types. For experiment II, energy restriction followed by ME requirements feeding, affected (P<0.01) pre-weaning live weight gain, weaning and final weights. Lambs from restricted ewes had higher (P<0.05) feed intake as % of leg weight and a trend to be less efficient (P=0.16) than lambs from unrestricted dams. Ribeye area and BF were not influenced by treatment. Treatment significantly affected slaughter weight, but had no effects on carcass yield and traits or on meat traits. The results obtained in both experiments indicate submitting ewes to energy restriction during gestation affects the performance of their progeny but the final outcome would depend on the ewe’s re-feeding level during late gestation and the capacity of the offspring to compensate the in utero restriction after birth.
Buffalo (Bubalus bubalis) is an important livestock species in many tropical and subtropical regions. In recent decades, the interest in buffalo’s milk have expanded and intensive buffalo farms start to emerge. However, breeding programs and population genetics information for this species is scarce or inexistent. The present study aims to test the suitability of the commercial high-density single nucleotide polymorphisms (SNP) genotyping panel, the Illumina BovineHD BeadChip, to estimate population genetics parameters, pedigree control and identification of common variants in major production candidate genes. From a total of 777 962 SNPs included in the panel, 20 479 were polymorphic in water buffalo at a call rate of 86% and an average expected heterozygosity (HE) of 0.306. From these, 357 were mapped within or around the flanking regions of several major candidate genes. A principal components analysis identified three different clusters, each representing pure swamp buffalo type, pure river buffalo type and admixed river buffalo. The hybrids between swamp and river buffalo were clearly identified as an intermediary cluster. The suitability of these SNPs data set for parentage and identity testing demonstrated that the combination of just 30 to 50 SNPs were enough to attain high probabilities of parentage exclusion (0.9999) in both types and identity (2.3×10−5 and 2.0×10−7) for river and swamp buffalo, respectively. Our analysis confirms the suitability of the BovineHD BeadChip to assess population structure, hybridization and identity of the water buffalo populations.
In this study, we isolate and analyse a new set of microsatellite loci for Cattleya walkeriana. Twenty-two primer pairs were screened for C. walkeriana (n = 32) and assessed for their transferability to Cattleya loddigesii (n = 12) and Cattleya nobilior (n = 06). All loci amplified for C. walkeriana; however, for C. loddigesii and C. nobilior, four and five primers, respectively, did not present amplification. The polymorphic loci presented between 2 and 13 alleles per locus for both C. walkeriana and C. loddigesii, with respective averages of 5.1 and 4.2. For C. nobilior, we found between two and five alleles per locus, with an average of 2.6. For C. walkeriana, observed heterozygosity varied from 0.100 to 0.966, whereas expected heterozygosity ranged from 0.097 to 0.900. The observed and expected heterozygosity for C. loddigesii and C. nobilior were also estimated. We found no significant linkage disequilibrium between any pair of loci, and evidence of null alleles at four loci (Cw16, Cw24, Cw30 and Cw31) for C. walkeriana. The combined power to exclude the first parent and combined non-exclusion probability of identity were 0.999 and 2.3 × 10−20, respectively. These new loci can be used in studies of germplasm resources, and assessments of genotypic and genetic diversity and population structure, thus improving the accuracy of such analyses and their applicability in the conservation and protection of these endangered species.
The polymer coil–stretch mechanism in turbulent drag reducing flows is analysed using direct numerical simulations of viscoelastic finitely extensible nonlinear elastic fluids with the Peterlin approximation. The study is carried out taking into account low and high drag reduction regimes. The polymer stretching and the alignment between the conformation tensor and other relevant entities are investigated using statistical and tensor analysis. The significant alignment between the former and the velocity fluctuations product tensor indicates that the initial polymer stretching due to the mean shear is increased by the flow stress fluctuations, providing a supplementary polymer extension. In addition, interactions between the turbulence and the polymer are evaluated from an instantaneous turbulent energy exchange perspective by considering streamwise work fluctuating terms in elliptical and hyperbolic flow regions separately. Near the wall, polymers not only release energy to the streaks, but also to the elliptical (or vortical) and hyperbolic (or extensional) structures. However, polymers can also be dragged around near-wall vortices, passing through hyperbolic regions and experiencing a significant straining within both these turbulent structures and storing their energy. Hence, polymers weaken elliptical and hyperbolic structures leading to a tendency toward relaminarization of the flow. Polymer release of energy occurs primarily in the streamwise direction, which is in agreement with the enhanced streamwise velocity fluctuation observed in drag reducing flows. A detailed polymer coil–stretch mechanism is provided.
Ureaplasma urealyticum and U. parvum have been associated with genital infections. The purpose of this study was to detect the presence of ureaplasmas and other sexually transmitted infections in sexually active women from Brazil and relate these data to demographic and sexual health, and cytokines IL-6 and IL-1β. Samples of cervical swab of 302 women were examined at the Family Health Units in Vitória da Conquista. The frequency of detection by conventional PCR was 76·2% for Mollicutes. In qPCR, the frequency found was 16·6% for U. urealyticum and 60·6% U. parvum and the bacterial load of these microorganisms was not significantly associated with signs and symptoms of genital infection. The frequency found for Trichomonas vaginalis, Neisseria gonorrhoeae, Gardnerella vaginalis and Chlamydia trachomatis was 3·0%, 21·5%, 42·4% and 1·7%, respectively. Higher levels of IL-1β were associated with control women colonized by U. urealyticum and U. parvum. Increased levels of IL-6 were associated with women who exhibited U. parvum. Sexually active women, with more than one sexual partner in the last 3 months, living in a rural area were associated with increased odds of certain U. parvum serovar infection.
An experiment was carried to evaluate the energy and protein requirements for the growth and maintenance of lambs of different sex classes. In all, 38 hair lambs (13.0±1.49 kg initial BW and 2 months old) were allocated in a factorial design with diet restriction levels (ad libitum, 30% and 60% feed restriction) and sex classes (castrated and non-castrated males). Four animals from each sex class were slaughtered at the beginning of the trial as a reference group to estimate the initial empty BW and body composition. The remaining lambs were weighed weekly to calculate BW gain (BWG), and when the animals fed ad libitum reached an average BW of 30 kg, all of the experimental animals were slaughtered. Before slaughter, fasted BW (FBW) was determined after 18 h without feed and water. Feed restriction induced reductions in body fat and energy concentration, whereas water restriction showed the opposite effect, and the protein concentration was not affected. The increase in BW promoted increases in body fat and energy content, and these increases were greater in castrated lambs, whereas the protein content was similar between classes tending to stabilize. The net energy required for gain (NEg) and the net protein required for gain (NPg) were not affected by sex class; therefore, an equation was generated for the combined results of both castrated and non-castrated lambs. The NEg varied from 1.13 to 2.01 MJ/day for lambs with BW of 15 and 30 kg and BWG of 200 g. The NPg varied from 24.57 to 16.33 g/day for lambs with BW of 15 and 30 kg and BWG of 200 g. The metabolizable energy efficiency for gain (kg) was 0.37, and the metabolizable protein efficiency for gain (kpg) was 0.28. The net energy required for maintenance (NEm) and the net requirement of protein for maintenance (NPm) did not differ between castrated and non-castrated lambs, with values of 0.241 MJ/kg FBW0.75 per day and 1.30 g/kg FBW0.75 per day, respectively. The metabolizable energy efficiency for maintenance (km) was 0.60, and the efficiency of metabolizable protein use for maintenance (kpm) was 0.57. Nutritional requirements for growth and maintenance did not differ between castrated and non-castrated lambs. This study emphasizes the importance of updating the tables of international committees and of including data obtained from studies with sheep breeds raised in tropical conditions, with the purpose of improving the productive efficiency of the animals
Plants’ ability to rebuild their tiller population is affected by weather changes and management strategies. The hypothesis of the present study was that frequency and severity of defoliation alter Mulato grass (Brachiaria ruziziensis × Brachiaria brizantha cv. Marandu) sward development, and the proportion of aerial and basal tillers, interfering with sward stability. The objective was to evaluate aerial, basal and total tiller population density and changes in tillering dynamics. Treatments corresponded to strategies of rotational grazing characterized by combinations between two pre-grazing (95% and maximum canopy light interception during regrowth; LI95% and LIMax) and two post-grazing conditions (15 and 20 cm stubble height). The experimental period comprised four seasons of the year: summer 2008 (February–March 2008); autumn–early spring (April to mid-November 2008); late spring (mid-November–December 2008); and summer 2009 (January–March 2009). Density of aerial tillers decreased from summer 2008 to late spring. Tiller death decreased from summer 2008 to autumn–early spring. Aerial and total tiller death increased from late spring to summer 2009, mainly for the LI95% treatment. No differences were observed in the tiller population stability index of aerial tillers for LI treatments or post-grazing heights. The balance between tiller appearance and death for basal tillers remained relatively stable from summer 2008 to late spring. For aerial tillers the balance decreased to negative values from summer 2008 to autumn–early spring for both LI treatments. For total tiller population, the balance decreased to negative values from summer 2008 to autumn–early spring. Results indicated a strong seasonal effect on Mulato grass tillering and growth. Tillering dynamics were affected primarily by grazing frequency, which changed the relative importance of basal and aerial tillers. The results suggested that basal tillering was the predominant perennation pathway.