Unravelling the relationship between a seasonal environment and the dynamics of forage growth in grazed swards

It is well reported in the scientific literature that pastures can have similar net forage accumulation when managed with contrasting structures. However, we hypothesized that the dynamics of forage accumulation in grazed swards is linked to seasonal-environmental conditions. Marandu palisadegrass (Brachiaria brizantha [Hochst. ex A. Rich.] was used as the forage species model. The experimental treatments were four grazing heights (10, 20, 30 and 40 cm) allocated to experimental units according to a randomized complete block design with four replicates and evaluated throughout four contrasting environmental seasons (summer, autumn, winter–early spring and late spring). Under rainy and warm periods, greater net forage accumulation was observed in pastures maintained taller; on the contrary, during the mild and dry periods, net forage accumulation rate reduced as grazing height increased. Such patterns of responses were related to compensations between tiller population density and tissues flows during summer and late spring and the reduced capacity of taller canopies to compensate lower population with greater growth rates during autumn and winter–early spring. Grazed swards changed their patterns of forage growth as they transitioned from favourable to more abiotic stressful conditions, suggesting that seasonal adjustments in grazing intensities are necessary in order to maximize forage production.     

Mineral requirements of hair sheep in tropical climates

In this study, we evaluated the requirements of calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na) and potassium (K) for sheep hair growth. Experimental diets contained different levels of metabolizable energy [ME; 0.96, 1.28, 1.72, 2.18 and 2.62 Mcal/kg of dry matter, (DM), corresponding to 4.23, 5.64, 7.58, 9.61 and 11.55 MJ/kg DM]. The lambs' hair (n = 48) at 2 months of age presented an average body weight (BW) of 12.05 ± 1.81 kg. At the beginning of the experiment, eight animals were slaughtered as a reference group to estimate the initial empty body weight and body composition. Net mineral requirements (g/day) ranged from 0.73 to 0.71 g of Ca, 0.51 to 0.49 g of P, 0.026 to 0.026 g of Mg, 0.16 to 0.19 g of Na and 0.15 to 0.13 g of K for animals with a BW ranging from 15 to 30 kg and a daily gain of 100 g. The results of this study indicate that the net macromineral requirements for weight gain in Morada Nova lambs are different from the values commonly recommended by the Agricultural and Food Research Council.     

Natural Stable Isotopes for Determination of Gastrointestinal Transit Time in Fish

This study evaluated the application of stable isotopes of carbon as an alternative and more accurate method to determine gastrointestinal transit time (GTT) in fish by comparing it to the inert marker method. The stable isotope method detects alterations of the normal carbon flow in a biological system by analyzing naturally occurring isotopes of carbon, contrary to studies based on conventional techniques that apply external markers to the diet to determine GTT through visual observation of the color change in feces. Therefore, 320 pacu, Piaractus mesopotamicus juveniles were reared in 32 tanks under two different temperatures (25 and 29 C). The pacu juveniles received two different diets, one based on ingredients derived from C₃ photosynthetic cycle plants and the other based on C₄ plant ingredients, both containing titanium oxide (TiO₂) as a marker. After 40 d, the isotopic signature of the diets was changed, and the marker was replaced by chromic oxide (Cr₂O₃). In the isotopic technique, the feces were analyzed to determine the exchange in the isotopic ratio of carbon δ¹³C. Both methods found that GTT was faster (nearly 6 h) in fish at 29 C when using the C₄/C₃ feeding strategy and slower in fish at 25 C using the C₃/C₄ strategy (15 h by inert marker and 18 h by the isotopic method). In conclusion, GTT determination in pacu juveniles using the stable isotope technique exhibits the same accuracy obtained with the inert marker method at temperatures suitable (nearly 29 C) for the metabolism of these animals.     

Microbial activity in the gut of piglets: II. Effect of fibre source and enzyme supplementation

Twenty four Duroc × Landrace male piglets, aged 21 days, were assigned to 1 of 4 experimental diets. Diets 1 and 2 contained 150 g kg^− 1 wheat bran and diets 3 and 4 contained 90 g kg^− 1 maize cobs as the major fibre source. All diets contained 480 g kg^− 1 wheat and 200 g kg^− 1 soybean meal. Diets 2 and 4 were supplemented with the following enzyme complex: 800 U/kg cellulase, 1800 U/kg glucanase and 2600 U/kg xylanase.

The replacement of wheat bran by maize cobs increased the acetic (P < 0.05) and decreased the butyric acid production (P < 0.05) in the cecum. Piglets fed diets with maize cobs had lower (P < 0.05) levels of butyric acid in the colon than those fed wheat bran.

The xylanolytic, pectinolytic and cellulolytic enzyme activities were higher (P < 0.05) in the cecum and colon of piglets fed the wheat bran based diets. The supplementation of the diet with the enzyme complex did not significantly affect the levels of short chain fatty acids formed in the small intestine and there was a non significant increase of the levels of acetic, propionic and butyric acids in the cecum and colon of piglets (P < 0.10). No interactions were present between fibre sources and enzyme addition.

The results suggest that the enzyme supplementation of the diet did not bring significant benefits to the animals and that when maize cobs replaces wheat bran in diets it negatively affects butyric acid production and fibre-degrading enzyme activity in the hindgut of piglets.     

Potential use of visible and near-infrared spectroscopy for pine species discrimination by examination of needles

The correct identification of pine species is necessary for proper application of wood in forest?based industries, since the quality of each species’ wood depends on factors intrinsic to the material. The aim of this study was to evaluate the potential use of near?infrared and visible spectroscopy in the discrimination of pine species planted in southern Brazil. Needles of Pinus clausa, P. glabra, P. kesiya, P. oocarpa, P. palustris, P. pseudostrobus, P. rigida, P. roxburghii and P. serotina were collected from experimental plantations located in the region of Rio Negro, Paraná, Brazil. The needles were dried and milled for analysis. The evaluation was performed with a spectral range of 400–750?nm (visible) and 1 000–2 500?nm (near?infrared). Analysis using the visible spectra resulted in two principal components explaining 95% of the variation between the needle samples. In the near?infrared analysis, it was possible to discriminate between all nine pine species studied using only two principal components, where the first explained 99% of the variation between species. Spectroscopy based on needles can be used for pine species discrimination, using the original data without mathematical treatment, in southern Brazil.     

Carbon dynamics in small tropical catchments under preserved forest and cacao agroforestry systems

Agroforestry Systems - Inland waters such as streams that receive carbon from terrestrial landscapes usually have a net heterotrophic metabolism and emit significant amounts of CO2 to the...     

The effect of arginine vasotocin on courtship behaviour in a blenniid fish with alternative reproductive tactics

In a sex?role reversed population of the peacock blenny, Salaria pavo, two alternative male types are present: (a) older and larger nest?holder males that defend nests in which females come to spawn, and (b) younger and smaller sneaker males that mimic female?courtship behaviour and nuptial colouration in order to try to sneak fertilizations during spawning episodes. In this study the effects of exogenous administration of arginine vasotocin (AVT, 3 μg/g body weight) on the behaviour of nest-holder males, sneakers and females was tested. AVT induced the expression of female courtship behaviour in sneakers and female nuptial colouration in sneakers and in females, but failed to promote the expression of male courtship behaviour in both male types.     

Prevalence and risk factors associated with goat gastrointestinal helminthiasis in the Sertão region of Paraíba State,Brazil

Gastrointestinal helminthiasis represents an obstacle to goat raising, causing severe damage to herds such as growth retardation, weight loss, and even death. In this study, we aimed to determine the prevalence and risk factors associated to goat gastrointestinal helminthiasis in the Sertão region of Paraíba State, Brazil. A total of 256 goats from 54 farms were systematically sampled. Blood and fecal samples were collected from each animal for egg per gram (EPG), larval culture, and packed cell volume (PCV) analyses. We found that 79.3 % of the goats investigated were parasitized with gastrointestinal helminths. Significant correlation (p?=?0.004) was observed between the EPG and PCV of the animals studied, and it was observed that the EPG increases as the PCV decreases. In the larval culture, the most prevalent helminth was Haemonchus sp. (83.2 %). Age and sex were significant variables (p?≤?0.20) for the development of gastrointestinal helminths: 86.8 % of animals over 36 months of age and 81.7 % of females were infected. The variable type of animal exploitation was also significant, with 90.3 % (p?≤?0.20) of the animals presenting double suitability (milk and meat). The Sertão region of Paraíba State presents high prevalence of gastrointestinal helminthiasis in goats, and age and type of animal exploitation are the most relevant risk factors to the development of these parasites.     

Effect of Leptin on In Vivo Goat Embryo Production

The aim of this study was to evaluate the effect of leptin administration during superovulation on in vivo goat embryo production. Ten mature does were superovulated with 133 mg follicle‐stimulating hormone (FSH) i.m. in six descending doses at 12‐h intervals. The goats received 4.8 μg/kg human recombinant leptin s.c. (leptin group, n = 5) or phosphate‐buffered saline (PBS) (control group, n = 5) with the first and second FSH doses. The does were mated and subjected to embryo collection by transcervical technique 6 days later. The total number of cells per embryo and the number of cells with fragmented DNA were assessed in selected blastocysts by combining Hoechst 33342 and terminal dUTP nick‐end labelling (TUNEL) staining. Plasma concentrations of oestradiol (E₂) and progesterone (P₄) were determined by electrochemiluminescence from the day of FSH treatment, on the day of superovulatory oestrus and on the day before embryo collection. Compared with the control group, the does that received leptin had a higher number of transferable embryos (p < 0.005), fewer embryos classified as degenerated (p < 0.001) and fewer TUNEL‐positive cells/blastocyst (p < 0.001). The number of transferable embryos was positively correlated with E₂ concentrations on day of oestrus (r = 0.562; p < 0.01) and P₄ concentrations on the day of embryo collection (r = 0.912; p < 0.001). We concluded that in vivo leptin administration during FSH treatment improved embryo quality and affected ovarian steroidogenesis in superovulated goats.