The objective of the current study was to investigate the possible use of alkenes (unsaturated hydrocarbons) of plant waxes as diet composition markers in sheep. Twenty-four sheep (30 kg live weight) were housed in individual pens (n=16, “pen” sheep) or in metabolism crates (n=8, “crate” sheep) for the total collection of faeces. Once daily, sheep were fed 720 g DM of a two-component diet consisting of a roughage source (chaffed perennial ryegrass) and a high-quality supplement (unpelleted sunflower meal, SFM) in different proportions, 7:1, 6:2, 5:3 and 4:4 (4 pen sheep and 2 crate sheep/treatment). SFM was labelled with a solution of beeswax to provide an alkane/ alkene profile different from the chaff. Diet composition was estimated from C27, C29, C31 and C33 alkene concentrations in diet and faeces (total faeces or rectal grab samples), using the least-squares package ‘EatWhat’. Estimates were conducted with or without correction of faecal alkane concentrations for incomplete faecal recovery, calculated from the alkene intakes and faecal outputs in the crate sheep.

Although the faecal alkene recoveries of alkenes were low, they did not differ between chain lengths for alkenes C27 to C33. Therefore in cage sheep, alkene-based estimates of SFM proportions, with or without faecal recovery correction, did not differ significantly from the proportions fed and were as accurate as earlier alkane-based estimates. In pen sheep, SFM proportions estimated from rectal grab samples were slightly but significantly over-estimated, regardless of whether or not recovery corrections were used. The over-estimates were not related to recovery corrections but to the small differences in concentrations between rectal grab samples from pen sheep and the total faeces from cage sheep. The lack of effect of recovery corrections does not mean they should be excluded from such calculations, as there may be situations in which there is an effect of carbon-chain length on alkene recovery. Use of recovery corrections also permits an estimate of whole-diet digestibility.

The present results indicate that alkenes could be useful additional markers to the alkanes for estimating the proportion of two dietary components in diets offered to sheep.

The objective of this work was to determine the rumen degradation characteristics over the growing season of maize stover in two contrasting zones in the central highlands of Mexico. Twenty four maize plots were selected, three harvest periods P1, P2, and P3 were established in order to evaluate degradation characteristics at different development stages, for ‘criollo’ maize varieties of three grain colours (white, yellow and black) representing different cultivation practices given their different growing cycles. In vitro gas production (GP) incubations were carried out, and cumulative gas volumes were fitted to the Krishnamoorthy, Soller, Steingass and Menke (1991) model. The results indicate that more research is needed to evaluate why maize degradability and fermentation characteristics as exemplified by this work are not greatly affected by time.

An experiment was carried out to evaluate the use of alkanes for estimating diet composition of goats and sheep offered three different dietary treatments. Twelve animals as two groups of 4 crossbred goats (G1, 24 kg live weight; G2, 22 kg) and 4 crossbred sheep (S, 26 kg live weight), were housed in metabolism pens. Animals were offered daily a total of 1 kg DM/100 kg live weight. G1 received 70% ryegrass (Lolium perenne) and 30% gorse (Ulex gallii), G2 received 70% ryegrass and 30% heather (Erica sp.) and S group ate 100% ryegrass. Diet composition was estimated from the alkane concentrations (using all alkanes from C23 to C36 or only odd-chain alkanes C27, C29, C31 and C33) in diet and faeces (with or without correction for incomplete faecal recoveries) using least-squares procedures.

Dietary treatment and animal species significantly affected alkane faecal recoveries, except for C24 and C36. When applying the faecal recovery corrections, there were no significant differences between measured proportions of dietary components and those estimated using all alkanes or odd-chain alkanes. In contrast, the proportions calculated without faecal recovery correction differed significantly (P<0.05) from the actual proportions and over-estimated the amount in the diet of those plant components with higher concentrations of long-chain alkanes (Erica sp. and Lolium perenne). The results indicate that alkanes are useful markers to estimate diet composition, however, it was observed that animal species and diet composition influenced the faecal recovery of alkanes. This suggests that the use of the alkane methodology for estimating the diet selection of grazing animals should be preceded by a calculation of the actual alkane faecal recoveries for each experimental condition.

Four feeds widely used in ruminant nutrition (corn silage, alfalfa hay, corn grain and soybean meal) and nine diets prepared in the laboratory by thorough mixing of these four feeds in different ratios, were analysed for: chemical composition according to the Weende and Van Soest schemes. Starch content, as well as total gas production and dry matter degradability after 8, 24 and 48 hours of incubation were measured. The same parameters were calculated for the nine diets from the measurements made on each of the four components (i.e. estimated values). For the chemical determinations, the differences between the analytical results (real values) and the corresponding estimated values varied little and did not reach statistical significance. However, statistically significant differences (P<0.05) between real and estimated values appeared for gas production at 24 hours (48.07 vs. 44.13 ml/200mg DM) and for DM degradability after 8 hours of incubation (32.35 vs. 30.56 %). The differences in the gas production measurements were removed when Diet 1 was excluded.

Sugar cane and maize silage samples were evaluated by the semi automated in vitro gas production technique. The associations between gas production and dry matter degradation (DMD) were analysed and high coefficients of determination were obtained for all the substrates. The results showed that particles losses could be influencing the DMD, including errors mostly when obtained before 6 hours of incubation. The gas alone could better predict the lag phase than the DMD before 6 hours of incubation.

The diet of cattle grazing in the Sanyati communal area, Zimbabwe was determined using plant particle identification from faeces from intact animals, and faeces and oesophageal extrusa from fistulated animals. A total of 130 plant genus, species and types were identified. The twenty most frequently occurring species in the samples comprised between 76 and 90% of the identifiable diet. The most frequent grass species were more than half of the identified diet in the dry season while they were half or less of the identified diet in the wet season. There were more plant species identified in the wet season than in the dry season. Significant differences were found when comparing the plant species identified in faeces to those in oesophageal extrusa from fistulated animals. This may be due to incomplete recovery of ingesta in the bags, or to the loss of identifiable particles in the faeces when compared to oesophageal extrusa because of digestibility. More research is needed to validate the use of oesophageal extrusa for diet botanical determination.

Two grazing trials were carried out to compare the grazing selectivity of oesophageal fistulated and intact steers, and to measure short term grazing behaviour and daily intake of steers in pastures (six pasture types) based on Brachiaria humidicola and Arachis pintoi. During the rainy season, the composition of the pasture affected the proportion of legume in the diet selected by the two groups of steers. The property of the pasture best related to legume selected by the intact steers was the legume mass in the forage available. The proportion selected by the fistulated steers was best related to the proportion of legumes in the pasture. The legume proportion selected by the two groups of steers was related to the bulk density of legumes in the forage, but the type of relationship varied between the groups. The relationship for the fistulated steers was linear, and that for the intact steers was exponential with an asymptote. During the dry season the relationships for the fistulated animals were similar to those observed during the rainy season, but the proportion of legume in the diet of the intact animals was not affected by attributes of the pasture. The pattern of intake in the short term was not affected by the height or amount of forage available during the rainy season, but during the dry season the weight per bite, and short-term intake was related to the height and amount of forage available. Daily herbage intake was not related to short-term intake.

The results of the first experiment confirmed that the selection of legumes by grazing steers can vary considerably between intact and fistulated steers. Furthermore it was suggested that the difference resulted partially from the different reactions of the two groups of experimental animals to changes in the attributes of the pasture. The second experiment showed that the daily intake of forage is not necessarily related to intake behaviour in the short term.

The sampling of forage from distinct sites in the pasture and which are then dried and ground separately as replicates for the in sacco technique, is the best procedure for studies of forage evaluation. It permits the evaluation of the true error (variation between blocks of plants) and not the variation between replicates obtained from only one sample of forage dried, ground and then divided between distinct nylon bags (which causes an underestimation of error). Consequently it is possible with only one ruminant to define an experimental design which is simpler, but capable of offering better precision.

In the traditional silvo–pastoral system, Alentejano pigs are fattened with acorns and pasture. Although this production system (“Montanheira”) has been characterised, there is a lack of knowledge on intake and digestibility of the diet, mainly due to the absence of tested methodologies in pigs. The n–alkane technique, extensively used in ruminants to estimate diet intake and digestibilitiy, has had less use in pigs. The objective of this experiment was to validate the n–alkane technique in Alentejano pigs. Faecal recoveries of natural and dosed n-alkanes, the diurnal variation of faecal n–alkane concentration, and the time span required to reach a steady state excretion of dosed alkanes were determined. Eight male Alentejano pigs (54.4±9.8 kg LW) were randomly allocated to two groups and placed in metabolic cages. They were fed 0.7 kg of pasture and 0.7kg of ground acorns daily as two meals. Pigs in Group-1 were given once daily artificial C32 (40mg/d) and C36 (40 mg/d) and those in Group-2 the same alkanes as two daily doses of 20 mg. Steady state excretion of both alkanes was reached 3 days after first dosing. Although no difference (P>0.05) was observed between treatments, the coefficient of variation of feacal alkane concentration when dosed twice daily was generally lower than when dosed once daily. Mean faecal recoveries of n–alkanes increased with increasing carbon-chain length (C25 to C36) from 38 to 69%, but were not significantly different from C29, C32, C33 and C36 (mean 0.694 SEM 0.067). Faecal nalkanes in samples collected every four hours for three days showed no diurnal variation in patterns of excretion apart from a higher concentration of C32 4 hours after dosing once daily. However variation between animals was lower when artificial alkanes were dosed twice daily than when once daily. The results indicate that the n–alkane techique may be used to estimate intake and digestibility under “Montanheira”, although further validation work needs to be done.

The in vitro gas production technique was used to observe the fermentation characteristics of three feedstuffs (barley, dried alfalfa meal, and dried beet pulp). Inocculum was provided from the caecal contents of suckling rabbits (23, 26, 31 and 35d old) which had access to their dams’ food. Mean OM degradation increased progressively with the age of the rabbits (P<0.01) from 67.4 to 70.8% with inocculum from 23 and 35d kits, and gas production from 302 to 357 ml/g OM incubated (P<0.01). It was confirmed that the in vitro gas production technique is a valid tool for the study the development of caecal microbial activity in rabbits.

The in situ technique (NB) was compared to the in vitro gas production technique (Gas) in terms of ability to estimate the dry matter degradation (DMD) using high soluble substrates (maize grains) and low soluble substrates (four tropical forages). The experiments (in situ and in vitro) were carried out at the same time using the same cow for both techniques and DMD was estimated at 6, 12, 24, 48 & 96 h. The results showed that DMD from Gas were lower than NB DMD and the correlation for the maize group were lower than those of the grass group which indicated that Gas technique, closed system, has potential to analyse highly soluble substrates, probably, overcoming the particle losses effect demonstrated by the in situ technique.

The aim of the present paper was to study the fermentation characteristics and kinetics of the carbohydrate fractions of fresh, ensiled and hay of oats (Avena sativa) using the Cornell Net Carbohydrate and Protein System (CNCPS) and the in vitro gas production technique (GPT). The whole forage and its NDF and EIR (ethanol insoluble residue) fractions were incubated in order to estimate the fermentation kinetics of carbohydrate fractions (A, B1 and B2) with the curve subtraction method. The carbohydrates fermentation kinetics estimated with the GPT agree with the three CNCPS carbohydrate fractions and explain some modification due to forage preservation methods. For all forages, the fermentation rate of the three CNCPS carbohydrate fractions showed the same ranking A > B1 > B2. Fermentation rate value (RM: 0.163, 0.057, 0.032 h-1 A, B1, B2 fraction for fresh oats; 0.106, 0.032, 0.016 h-1 for A, B1, B2 fractions of ensiled oats; 0.165, 0.051, 0.022 h-1 A, B1, B2 fraction for oats hay) could be used as kd in the CNCPS.

The objective of this study was to compare five methods of forage preservation (ice, dry ice, liquid-N, drying in newspaper, and sundried) on the concentration of the n-alkane C31 in Medicago sativa cv Puebla 76 (lucerne/alfalfa), Trifolium repens latum (white clover), Lolium perenne (perennial ryegrass), Pennisetum clandestinum (kikuyu grass) and Dactylis glomerata (orchardgrass/cocksfoot). The sampled forages in ice and dry ice were kept in hermetically sealed plastic bags in a plastic cooler. The deep frozen samples were put into small plastic bags and submerged in liquid-N. The samples dried in newspaper were placed between sheets of newspaper, and put into hermetically sealed plastic bags. All these samples were taken to the laboratory and freeze-dried approximately 24 h later. The sun-dried samples were taken to the laboratory in newspaper and sun-dried for 48 h. The forage samples were ground and worked on in triplicate, extracted by the Soxhlet method (C34 n-alkane was used as standard and n-heptane as solvent), saponified, separated, purified and injected into a gas chromatograph. The data were analysed for variance as a randomised factorial (n=74). The comparison between means was by the Boneferroni test (P<0.05). The interaction between forage and method of conservation was significant P<0.0001). There were no differences between methods of conservation for white clover (mean 26mg C31/kg DM) or orchardgrass/cocksfoot (mean 31 mgC31/ kgDM). In comparison with liquid-N, (261 mgC31/kgDM), the other methods reduced the concentration of n-alkane in kikuyu grass by 27-35%. Sun and newspaper dried samples increased the concentration of C31 in alfalfa/lucerne by 6 and 15% respectively in comparison with freezing with liquid-N (291 mgC31/kgDM), while that frozen on ice reduced C31 by about 8%. This method, however, increased the ryegrass n-alkane by 12% in relation to liquid-N (169 mgC31/kgDM), but sun drying reduced it by about 40%. It is concluded that drying in liquid-N is the most reliable method for the conservation of samples for n-alkane analysis.

In vitro rumen incubation systems are widely used to determine substrate degradation and the amount of fermentation products like gases, short chain fatty acids and the microbial biomass produced. Here we compare the influence of the amount of inoculum used for preparing the incubation medium on short chain fatty acid production and composition. Treatments were 10% and 30% (v/v) of filtered rumen fluid used for inoculation. In a series of experiments it was demonstrated that the two treatments did not alter the gas production or the amount of substrate truly degraded. However, SCFA production (especially acetate) was significantly reduced when only 10% of inoculum were used for incubation. We propose that acetate was taken up by rumen microorganisms as a precursor for growth, although it cannot be excluded that an altered microbial composition contributed to the observed differences.

To test the applicability of faecal NIRS to real conditions, an experimental approach was undertaken across several representative dairy farms (N = 30) located ‘La Réunion’ island. From an ongoing survey, this approach consists to characterize the nutritional value of all feeds (grazed fresh forage, hay, silages and supplementary feeds) offered to the lactating herds, and to predict ingested diet from faecal NIRS models previously developed on a large experimental sheep faeces reference data-base.

The methodological objective was to evaluate if such a spectral database could be a useful reference to estimate dairy cow total dry matter intake and diet quality, and so predict the grazed grass intake with reasonable accuracy. According to preliminary results, the NIRS estimated total intake varied between 13.7 and 19 kg DM/day and in vivo organic matter digestibility ranged from 51.7 to 74.8 % with an averaged value of 66 %. The estimated grass intake varied between 0 to nearly 10 kg DM/d. On a spectral basis, dairy cows faeces were quite different from the sheep faeces reference database, with an averaged standardised distance (H) upper of 3.0 (H = 9.1; Hmin = 2.08 – Hmax = 19.22) but predicted intake appeared valid. Indeed, according to the feeding value of diets and lactating cow requirements, the NIRS predicted total intakes were well correlated to the level of milk production. Moreover, for four particular situations, the fresh grass was cut, distributed at the trough and total intake really measured. The correlation between predicted and measured values was high with R2 = 0.94 and standard error of regression = 0.469 kg DM/d. These initial results appear quite encouraging, although the methodology is still exploratory and needs to be validated across a larger set of data. As a low cost and rapid prediction technique, NIRS appears to be a potential methodology that could find many useful developments in the improvement of the knowledge of forage use in tropical conditions.

The microbial fermentation of the tropical leguminous browses Acacia cornigera (ACA), Albisia lebbekoides (ALB), Enterolobium cyclocarpum (ENT) and Leucaena leucocephala (LEU) was estimated in vitro as the final production of gas. ACA gave the greatest final (asymptotic) gas volume (D; 179 ml/g DM) and fractional rate constant (0.070). Although ENT showed the greatest rate constant (0.87), reaching half its maximum gas production in 7.8 h, it produced less gas than ACA by 9 h incubation, and did not differ from LEU by 24 h ALB gave the lowest gas production. In another trial the negative effect of tannins was estimated over 48 h as ameliorated by the addition of PEG. The effect was variable between species, the greatest being with ALB (Restriction of 0.60-0.68 of the potential gas volume due to the presence of tannins) and increasing slowly, reaching its’ maximum at 12 or 24 h with ACA (0.33) or LEU (0.16). There was no response to the addition of PEG with ENT indicating that other secondary compounds distinct from the condensed tannins were affecting microbial utilisation.

An equation predicting organic matter digestibility (OMD) of the diet from faecal crude protein content (FCP) was established by Lukas (2002) with data from cows fed various diets based on roughage of temperate origin. The suitability of this equation to predict OMD of tropical roughages was tested with data from grazing and stall-fed cattle, sheep and goats. The correlation between measured OMD and that estimated from the average FCP of a group of animals consuming the same diet was r=0.91, and the deviation between estimated and measured values averaged 6%. Poor estimates were obtained for feeds with high biological tannin activity. Using the equation provides an easy assessment of OMD of tropical roughages that do not contain biologically traceable amounts of anti-nutrients.

The experiment was carried out in the east of Yucatán, in pastures of B. brizantha. It was of three months duration during the end of the rainy season. Four rumen cannulated cows with an average weight of 442 kg were used at all of three stocking rates: Low (2LU/ha), Medium (4LU/ha) and High (6LU/ha), to evaluate the effect of an empty rumen on the rate of biting, which was measured as the time taken to take 20 uninterrupted bites on ten occasions. The measurements were made on two sequential days at 09.00 h, the first under normal conditions, the second with an empty rumen. There was no effect (P<0.050 of rumen emptying on the rate of biting which was 24 bites per minute when the animals were normal, and 25 bites a minute when the rumen was empty. On the other hand, there was a reduction of 8% in the rate of biting for the animals at the high stocking rate compared with the low and medium stocking rates. The finding that bite rate was not affected by an empty the rumen is evidence which gives confidence in the use of cannulated animals as collectors of representative samples of forage under grazing conditions.

An in vitro gas production technique was used to evaluate a fat protection method (Ca-soap). The Ca-soaps were prepared by incorporation of oil into a slaked lime solution which had been prepared immediately before. The proportions employed were 10:1 (oil:slaked lime). A feed sample of 0.5g was incubated in a N-rich medium, using 6 ml ruminal liquor and 54 ml medium. A factorial design 2x3 (2 inoculum sources from cows fed with and without Ca-soap x 3 diets) was employed. Diets were A) Control: 70% grass (Pennisetum purpureum var. Taiwan), 30% sorghum grain; B) Soybean lecithin: 70% grass, 20% sorghum, 10% Lecithin; and, C) Ca-soap: 70% grass, 20% sorghum 10% Ca-soap (made from lecithin). Total gas production, DM and OM in vitro digestibility were measured. A 10% reduction (approximately) (P<0.05) on IVDMD and IVOMD with the oil diet was found, but no differences were found (P>0.05) between Control and Ca-soap diets. No effect was found due to inoculum source (P>0.05). Compared with the Control diet, the total gas production was reduced (P<0.05) in the oil diet and was intermediate in Ca-soap diet (P>0.05). It was concluded that Ca-soap diets are a source of rumen inert fat for both the in vitro incubation and the animals fed with this supplement. Ca-soap had no effect on IVDMD and IVOMD. In vitro gas production techniques can be useful tools to evaluate dietary fats at ruminal level.

A 3 x 3 Latin square design was conducted with 3 trotters (mean weight 510 kg) fed concentrates supplemented with 5.0 kg wrap bale grass silage (WS), 7.0 kg mixed hay (H) or 6.0 kg barley straw (BS) daily. Amounts of concentrates were adjusted to cover maintenance energy requirements together with forage. Concentrates, WS, H and BS had 86, 80, 86, and 87% DM with 350, 560, 610 and 740 g NDF/kg DM, and 190, 350, 390 and 490 g ADF/kg DM, respectively. Forages and concentrates were fed twice daily, but during the 4 experimental days, the horses had access to one quarter of the daily forage ration for 60 minutes at 9 am, 11 am, 1 pm and 3 pm. Forages not eaten within each of the four meals were recorded and fed again at 4 pm. Eating behaviour was observed and jaw moments (JM) recorded from 7 am to 4 pm by measuring pressure oscillations (PO) in a tube filled with water positioned around the mouth. Effective time spent chewing (ECT) and the numbers of jaw movements (JM) were identified from the manual observations and JM with exclusion of small pauses without mastication. The number of JM, the effective chewing rate and the ECT values per kg forage DM, forage NDF and forage ADF differed significantly (P<0.01) between forages and between forages and concentrates (P<0.01). The mean ECT values ranged from 50±4.7 minutes per kg WS dry matter to 100±4.7 minutes per kg BS dry matter, and from 90± 6 minutes per kg WS NDF to 135±6 minutes per kg BS NDF. The highest chewing rate (1.45±0.06 Hz) was found during concentrate meals and the lowest during BS meals (1.20±0.05 Hz). The horses spent more time eating (min/kg NDF) forages compared with values reported from cattle eating forages, whereas the total ECT values of 90 to 135 minutes chewing time per kg NDF in horses range from 60 to 90% of the time dairy cows to spent masticating during eating plus ruminating.