Jesús Salvador González

Effect of forage to concentrate ratio in the diet on ruminal fermentation and digesta flow kinetics in sheep offered food at a fixed and restricted level of intake.

The effects of four diets differing in their for age: concentrate ratio (80:20, 60:40, 40: 60 and 20:80; g/100 g fresh matter) on rumen characteristics, digestibility and digesta flow kinetics were investigated. Alfalfa hay was used as forage and concentrate was composed of barley, soya-bean meal and maize. Diets were prepared by mixing all ingredients and offered to the animals as complete diets. Eight mature Merino sheep, each fitted with a rumen cannula, were offered 1·055 kg dry matter per day of the corresponding diet over two experimental periods. The daily evolution of ruminai pH, volatile fatty acids (VFA) and ammonia nitrogen (N) concentrations were measured. Digestibility was determined by total faecal collection and Cr and Co were used as markers to estimate digesta passage rates. Microbial nitrogen flow at the duodenum (MNDF) was estimated from the urinary excretion of purine derivatives (PD). The apparent digestibility of organic matter increased ( P P P P > 0·05). Both liquid and solid digesta outflow rates from the rumen decreased quadratically ( P P > 0·05) by changes in the diet. In contrast, the daily urinary excretion of both allantoin and total PD increased quadratically ( P P

Artificial incubation of crayfish eggs ( Pacifastacus leniusculus Dana) from early stages of embryonic development

Abstract Three experiments on artificial incubation of crayfish eggs ( Pacifastacus leniusculus Dana) were carried out under different thermal regimes using a specially designed incubator tested in previous trials. Each treatment included a period of low temperature of different duration. Three flow rates were used in each experiment: 3.0, 1.5 and 0.5 l/min. In all cases the eggs were detached from females at three phases of embryonic development: beginning of gastrulation (mean degree days 230, 18 days after spawning); embryo between closing of the blastopore and appearance of mandibular rudiments (mean degree days 365); and embryo with naupliar appendages (mean degree days 480). The results showed that it is possible to auain acceptable juvenile stage 2 survival rates (58.9%) even though eggs were detached at the earliest embryonic phase (beginning of gastrulation). In the experimental incubator, flow rates could be reduced to 0.5 l/min without decreasing survival. The highest survival to juvenile stage 2 (72.1%) was obtained by delaying egg removal until the appearance of naupliar appendages, and using a thermal treatment of 15.5 ° ± 1 °C preceded by a 3-week period of low temperature (5 ° ± 1 °C) commencing at stripping time.

The effect of method of forage conservation and harvest season on the rumen degradation of forages harvested from permanent mountain meadows

An irrigated permanent mountain meadow (Leon, Spain) was cut twice in 1987, in late June, and again in early September after the summer regrowth. Herbage harvested from each season was preserved by different methods, namely freezing (fresh), ensiling in plastic bags (silage) and sun-curing (hay). Rumen degradation characteristics were determined by the nylon bag technique. Forages harvested in September had a higher crude protein (CP) concentration (153 v. 104 g/kg dry matter (DM)) and a lower cell wall concentration (467 v. 599 g/kg DM) than those from the June cut, resulting in a greater DM potential degradability (0·856 v. 0·751) and a faster degradation rate (0·088 v. 0·057 per h). Method of conservation did not affect the CP concentration of the forages, but had a significant effect on their nitrogen (N) solubility and protein degradability. Hay had the lowest N solubility (0·388) and CP degradability. Ensiling led to an increase in the N solubility (0·668 v. 0·554) compared with the fresh control, resulting in a higher effective degradability of CP estimated for different rates of passage. Forage conservation caused a slight increase in the relative proportion of the cell wall in the total DM (mean neutral-detergent fibre concentrations for fresh forage, hay and silage were 510, 548 and 536 g/kg DM, respectively) presumably due to loss of cell contents. Potential DM degradabilities of fresh forage, hay and silage were similar (0·805, 0·813 and 0·791 respectively). Although hay seemed to be degraded to a greater extent and at a faster rate than the other two types of forages, the rumen degradation characteristics were not consistently affected by the method of conservation to an extent that could have important nutritional implications.

Comparison of laboratory methods for predicting digestibility of hay in sheep

Abstract Eleven sun-cured hays with a crude protein and neutral-detergent fibre content ranging from 57 to 207 and 428 to 744 g/kg DM, respectively, were studied for the relationship between in vivo DM digestibility (DMD) in sheep and estimates from chemical composition (crude protein content and Van Soest fibre analyses), in vitro Tilley and Terry technique, enzymatic (digestion by cellulase, pepsin + cellulase and neutral-detergent + cellulase), and in situ techniques (potential and effective degradabilities). On the basis of the coefficient of determination (R2) and the residual standard deviation (RSD) of the regression of in vivo DMD on the results from the investigated techniques, the neutral-detergent + cellulase method (R2 = 0.979; RSD = 0.993) and the in situ (effective degradability; R2 = 0.968; RSD = 1.21) methods gave the most precise estimate of DMD. While the in situ technique requires fistulated animals and is difficult to standardize, the neutral-detergent + cellulase method is simple and rapid, and standardized cellulases are commercially available, so that this technique could provide a suitable tool for predicting DMD of hay.

Short- to medium-term effects of consumption of quebracho tannins on saliva production and composition in sheep and goats.

Eight Merino sheep (49.4 ± 4.23 kg BW) and 8 Alpine goats (53.2 ± 2.51 kg BW) were used to study the effect of ingestion of quebracho tannins on salivation. Four sheep and 4 goats were individually fed a daily allotment of 20 g DM of alfalfa hay/kg BW (Control). Another 4 sheep and 4 goats were also given 20 g DM of alfalfa hay/kg BW supplemented with 50 g of quebracho/kg DM (Tannin) for a period of 64 d. The saliva secretion from the left parotid gland was collected by insertion of a polyvinyl chloride catheter into the parotid duct and the amount of parotid saliva produced recorded over three 48-h periods on d 1 and 2 (P1), d 31 and 32 (P2), and d 61 and 62 (P3) after the tannin feeding was initiated. The total amount of saliva produced was estimated from rumen water kinetics determined on d 4, d 34, and d 64 of the experiment. Experimental design was completely randomized, with repeated measures on each experimental unit, performing separate analysis for sheep and goats. Parotid saliva production was not affected by the sampling period in either animal species receiving the Control diet. Corresponding values for sheep were 2.04, 2.12, and 2.27 L/d (P = 0.89) and for goats 1.65, 1.79, and 1.86 L/d (P = 0.95). Sheep fed the Tannin diet produced 55, 73, and 107% of the amount of saliva recorded in sheep fed the Control diet on P1, P2, or P3, respectively. Corresponding values in goats were 88, 130, and 134% on P1, P2, or P3, respectively. Estimated total saliva production was not affected (P = 0.50 for sheep and P = 0.97 for goats) by the ingestion of quebracho. There was no difference (P > 0.10) in osmotic pressure, P, Mg, Ca, urea, and protein concentrations in parotid saliva. There were, however, differences in Na and K concentrations in response to the ingestion of quebracho tannins, with Na concentrations increasing (P = 0.05) and K concentrations decreasing (P = 0.04) in sheep saliva and pH increasing (P = 0.05) in goat saliva. In conclusion, the inclusion of quebracho at 50 g/kg DM for 64 d does not appear to alter saliva production in sheep and goats.

Decrease of ruminal methane production in Rusitec fermenters through the addition of plant material from rhubarb (Rheum spp.) and alder buckthorn (Frangula alnus).

Roots of rhubarb (Rheum spp.) and bark of alder buckthorn (Frangula alnus) were tested as feed additives for decreasing ruminal methane production released from anaerobic fermentation of a forage-based diet in a rumen-simulating fermenter (Rusitec). Sixteen fermentation units (vessels) were set up for the experiment lasting 19 d. Treated vessels were supplied with 1g/d of rhubarb or alder buckthorn (4 vessels per plant species); another 4 vessels received 12 microM sodium monensin (positive control), and the remaining 4 vessels were controls (no additive). Upon termination of the experimental period, batch cultures were inoculated with the liquid contents of the vessels for examining in vitro fermentation kinetics of cellulose, starch, barley straw, and the same substrate used in the Rusitec cultures. Monensin induced changes in fermentation in agreement with those reported in the literature, and inocula from those cultures decreased the fermentation rate and total gas produced in the gas kinetics study. Rhubarb decreased methane production, associated with limited changes in the profile of volatile fatty acids throughout the duration of the study, whereas digestibility and total volatile fatty acids production were not affected. Rhubarb inocula did not affect gas production kinetics except for cellulose. Alder buckthorn decreased only methane concentration in fermentation gas, and this effect was not always significant. The use of rhubarb (milled rhizomes of Rheum spp.) in the diets of ruminants may effectively modulate ruminal fermentation by abating methane production, thus potentially involving productive and environmental benefits.

Effect of forage to concentrate ratio in complete diets offered to sheep on voluntary food intake and some digestive parameters.

Twelve mature ewes were used to study the effect of forage: concentrate ratio in complete diets on voluntary intake and some digestive characteristics. Diets consisted of four combinations of chopped lucerne hay and a concentrate (390 g cracked barley grains, 440 g cracked maize grains and 170 g soya-bean meal per kg of concentrate) in the following proportions (fresh matter basis): 0·8:0·2 (C20), 0·6:0·4 (C40), 0·4:0·6 (C60) and 0·2:0·8 (C80). Diets were offered over two 42-day periods and, in each of them, three sheep received one of the four diets, with the restriction that no animal received the same diet in both periods. Chromium Ill-mordanted fibre was used as a marker to estimate passage rate of digest a and microbial nitrogen supply (MNS) was estimated from the urinary excretion of purine derivatives. The increase in the proportion of concentrate affected linearly ( P P P P > 0·05) by the proportion of concentrate in the diet. Both particulate passage rate from the rumen and through the caecum and proximal colon decreased linearly ( P P > 0·05) by the diet, whereas its efficiency (g/kg digestible OM intake) tended ( P

Duration of egg storage at different temperatures in the astacid crayfish Pacifastacus leniusculus: critical embryonic phase

Abstract The critical phase that would limit duration of egg storage in the astacid crayfish Pacifastacus leniusculus was investigated. Weekly monitoring was conducted during an 84-day period of storage at three different constant temperatures (15.5±1, 10.5±1.5 and 4±0.5 °C). After artificial incubation, stage 2 juveniles were only obtained from the lowest storage temperature, the sole treatment in which eggs did not reach the critical embryonic stage by the end of the storage. This limiting stage occurs at phase XII (embryo with pulsating heart) when embryogenesis of stored eggs ceased and phase XIII (eyed stage) was not reached. Eggs were also stored at a constant refrigeration temperature (4±0.5 °C) for periods ranging from 84 to 126 days. Mean survival rates to juvenile stage 2 were acceptable (approximately 50%) and different batches of juveniles were obtained over a 3-month period, depending on the duration of storage. The combined use of storage and artificial incubation techniques could have important applications to the development of astacid crayfish culture.

Prediction of aspects of neutral detergent fibre digestion of forages by chemical composition and near infrared reflectance spectroscopy

Sixty-two herbage samples, harvested in natural meadows located in the mountains of Leon (north-west Spain), and characterised by a diverse botanical composition and different stages of maturity of the plants, were used to evaluate the ability of chemical composition and near infrared (NIR) spectroscopy to predict in vitro digestibility and in sacco degradability of the neutral detergent fibre (NDF) fraction. In vitro digestibility was performed as described by the Goering and Van Soest procedure. Three dry Holstein-Friesian cows fitted with a rumen cannula were used to incubate the herbage samples. A Bran+Luebbe InfraAlyzer 500 spectrophotometer was used to obtain the NIR spectra corresponding to the 62 original herbage samples. Prediction equations for the estimation of in vitro digestibility and in sacco degradability parameters of the NDF fraction were generated using NIR spectra or chemical data as independent variables. The results showed that the in vitro digestibility and kinetic parameters of degradation of the NDF fraction could not be predicted accurately, probably as a consequence of the errors corresponding to the reference methods. In contrast, these errors did not greatly affect the extent of disappearance of the NDF fraction at later times, so the accuracy of prediction of these parameters was higher, especially when NIR spectra were used as independent variables. This is probably due to the close relationship that the parameters showed with the chemical data, since this kind of information, together with some physical characteristics of the samples, is included in the NIR spectra.

Storage and Transport of Embryonated Eggs of the Signal Crayfish Pacifastacus leniusculus

Abstract We evaluated storage of embryonated eggs of the signal crayfish Pacifastacus leniusculus in polystyrene boxes for 1, 3, 6, 28, and 56 d at two temperatures, 12 ± 1°C and 4 ± 0.5°C. For periods up to 4 weeks, survival at the end of storage for both temperatures exceeded 95%, and survival to stage-2 juvenile (after first molt) exceeded 63%. Following 8 weeks of storage, survival to stage-1 and stage-2 juveniles was significantly reduced. These experiments have shown the feasibility of egg storage for up to 4 weeks. In addition, 6-h transport (300 km) of embryonated eggs followed by up to 2 d of storage did not have a negative effect on egg viability.