ABSTRACT: The high moisture content of wet distillers’ grains with solubles (WDGS) has limited its feeding value despite the relatively high nutritive value. The co–ensiling with whole–plant maize, as a complementary feed, was evaluated for growing lambs by formulating diets whose contents were: whole plant maize silage (WPMS) + sunflower oilcake meal (SOM) (control, WPMS + SOM), whole plant maize silage + dried distillers’ grains (WPMS + DDGS), and whole–plant maize (WPM) co–ensiled with WDGS (WPM – WDGS). Rumen fermentation parameters and in situ degradability of the diets were evaluated using three cannulated Merino wethers in a cross over 3 × 3 Latin square design experiment that lasted 39 days. Concurrently, feed intake and growth performance of South Africa Mutton Merino lambs (29.7 ± 3.6 kg) were evaluated over 45 days. The WPMS + DDGS diet had a lower rate of dry matter degradation (p < 0.05) compared to the WPMS + SOM and WPM–WDGS diets. However, the rapidly fermentable fraction, as well as the progressively fermentable fraction of the diet dry matter, was not different (p > 0.05). No differences in rumen volatile fatty acid, ammonia nitrogen concentration nor rumen pH of the wethers as a result of diet differences were observed. Lambs consuming the WDGS–based diet had a lower average daily intake and average daily gain (p < 0.05) compared to lambs consuming the DDGS and WPMS–based diets. However, the feed conversion ratio was not affected by diet differences (p > 0.05). In conclusion, co–ensiling WDGS with whole–plant maize provides the opportunity for the long–term storage and utilization of WDGS in lamb feeding.

ABSTRACT This study evaluated the potential utilisation of African yam bean (AYB) seed as a supplement to Guinea grass on in vitro gas and methane (CH4) production, as well as the effect of processing on AYB nutritive value. In experiment 1, unprocessed AYB meal at 10, 15, 20, and 25% inclusion levels was added to Guinea grass substrate and evaluated for in vitro gas production, CH4, and in vitro organic matter digestibility (IVOMD). In experiment 2, the effect of soaked, boiled, toasted, and fermented AYB meal at 20% inclusion on in vitro fermentation was evaluated. In vitro gas production as well as in vitro organic matter digestibility of Guinea grass increased with AYB supplementation. The associative effect of Guinea grass with AYB showed an increase in gas and CH4 production. At 20% inclusion level, AYB processing methods did not affect the gas production, CH4, and IVOMD of the substrate. Fermentation improved the crude protein, iron, and zinc contents, reduced acid detergent fibre concentration but did not reduce the concentrations of alkaloid, total phenol, saponin, and trypsin inhibitors of AYB. Seed soaking for 48 h reduced the total phenol, tannin, oxalate, and phytate content, while seed boiling reduced the concentrations of alkaloid, total phenol, tannin, and trypsin inhibitors. Compared with the raw AYB, boiling is the most effective processing method to reduce the investigated phytochemicals, followed by soaking, toasting, and fermentation, in that order.

ABSTRACT The aim of the present study was to determine whether sunflower meal (SFM), a highly rumen degradable protein (RDP) source, can be substituted with non-protein nitrogen (NPN, urea) without impacting negatively on intake, digestibility, rumen fermentation and microbial nitrogen (N) synthesis (MNS) in wethers consuming low quality Eragrostis curvula hay. Five wethers were fed ad libitum, low quality hay and supplemented twice-daily in equal proportions, via the rumen cannulae, one of five iso-nitrogenous and iso-energetic supplements in a 5 × 5 Latin square design experiment. The supplements differed in the ratios of rumen degradable N (RDN) supplied by either SFM and/or urea and is presented as percentage of RDN supplied by urea: T0 (100 % SFM, 0 % urea); T15 (85 % SFM, 15 % urea); T30 (70 % SFM, 30 % urea); T45 (55 % SFM, 45 % urea) and T60 (40 % SFM, 60 % urea). Forage intake and total tract dry matter (DM) digestibility did not differ; however, higher forage neutral detergent fiber (NDF) digestibilities were observed in the sheep supplemented with the higher urea-treatments (T45 and T60) compared to T15. Neither rumen pH nor total rumen volatile fatty acid (VFA) concentraions differed. The mean rumen ammonia nitrogen (RAN) concentration of the sheep supplemented with T60 was higher than T30 (9.35 mg dL−1 vs. 7.41 mg dL−1); however, no differences were observed in MNS or efficiency of MNS among treatments. Results suggest that up to 60 % of RDN supplied by SFM can be substituted with urea, without affecting intake, digestibility or MNS in wethers fed a low quality tropical hay.

The nutritional value of browse foliage from the Thorny Kalahari Dune Bush veld of South Africa is not characterized. Most of this browse species is rich in tannin, but still palatable, and is consumed by ruminants during the dry season, as well as having a role to play in mitigating enteric methane emission from ruminants. In this study, the rumen methane mitigation potential of 19 browse species foliage collected from the Thorny Kalahari Dune Bush veld, was analyzed in terms of chemical composition, in vitro fermentation, digestibility and methane production. In vitro gas and methane production and organic matter digestibility (IVOMD) were determined by using rumen fluid collected, strained and anaerobically prepared. A semi-automated system was used to measure gas production (GP) from each browse species by incubating 400 mg samples in a shaking incubator at 39 °C with or without inclusion of 400 mg of polyethylene glycol (PEG). Data for all the parameters collected were statistically analyzed using the SAS (9.0) general linear model (GLM) procedure, and differences between foliage species were determined using Duncan’s multiple-range test. Acacia luederitziiand Monechma incanumshowed the best potential for decreasing methane production by up to 90 % after 48 h of incubation. The secondary components (mainly tannins) of the browse species appeared to have a significant effect on volatile fatty acids (VFA), methane and gas production as judged by the comparison of samples incubated with or without PEG inclusion. The substantial amount of crude protein (CP) content coupled with their anti-methanogenic effect during fermentation would make these browses a potential mitigation option for small scale farmers and pastoralists in sub-Sahara Africa. However, it is also very important that systematic and strategic supplementation in a mixed diet should be looked at as the way forward in terms of best utilization.

In recent decades supplementation of animal feeds with exogenous fibrolytic enzymes has substantially improved digestibility and animal performance. However, information related to associated methane production is limited and inconsistent. This study evaluated the effect of cellulase and xylanase enzymes on in vitro methane production of Eragrostis curvula hay, maize (Zea mays) stover and a total mixed ration (TMR) at seven levels of the two enzymes. Feed samples were incubated for 2, 12, 24 and 48 h in an in vitro batch culture with buffer and rumen fluid, and fibrolytic enzymes. Gas production was measured using a pressure transducer connected to a data tracker, while methane gas was analysed using a gas chromatograph which was calibrated with standard CH4 and CO2. Increases in the level of enzyme application resulted in increases in gas volume, total volatile fatty acid (VFA) production, dry matter (DM) disappearance and associated increases in methane production. The linear increase in percentage and volume of methane production in tandem with increases in level of enzyme application might be due to increased fermentation, and organic matter degradability that resulted in a shift in VFA production towards acetate. Considering the efficiency of DM and neutral detergent fiber degradation and production of associated VFA with levels of enzymes, the use of 1 mg g−1 DM of enzyme can be a good option for the feeds tested. However, they cannot decrease methane production. It will be very important to consider other hydrogen sinks that can capture directly extra H+ produced by the addition of enzyme so that their supplementation could be very efficient and environmentally sound.

An experiment was conducted to investigate the influence of stage of growth at harvest on fermentative characteristics of Panicum maximum silage. The treatments were three different growth stages (early vegetative, boot and full bloom stage) that were ensiled directly or wilted prior to ensiling. Directly ensiled and wilted forage material were mixed prior to ensiling with molasses at 12 and 8 kg/ton dry matter, respectively. Thereafter, each treatment was ensiled in 12 one litre glass jars (bottles). From each treatment, samples of the silage were taken from three bottles at 0, 7, 21 and 120 d post-ensiling for analysis of fermentative characteristics. Growth stage in directly cut silage had no effect on silage pH between days 0 and 21. In contrast, within the wilted groups, a lower pH was observed at day 7 when the plants were harvested at the boot stage than at an early vegetative or full bloom stage. In both directly cut as well as prior wilted silage, a higher lactic acid concentration was recorded on day 7 in the boot stage silage compared to the full bloom stage silage, but on day 21 the boot stage had a lower lactic acid concentration than that of the full bloom stage silage. Growth stage had no effect on the acetic acid concentration on day 7. However, on days 21 and 120 the full bloom stage had a higher acetic acid concentration when the material was directly ensiled. In contrast, in prior wilted silage a higher acetic acid concentration was found in the early vegetative stage silage than in the full bloom stage silage at 120 days post-ensiling. Total nitrogen was lower in the full bloom stage silage than in the early vegetative and boot stage silages. A higher level of ammonia nitrogen was recorded at days 7 and 21 for the early vegetative stage silage as compared to the boot stage silage. A similar trend was revealed in the prior wilted groups between days 0 and 21. Harvesting at the boot growth stage consistently resulted in a good fermentation process with desirable fermentation end products (low pH and higher lactic acid concentration) up to a period of 21 days, but when compared at 120 days post-ensiling the differences between boot and bloom stages were not clearly observed in terms of fermentative attributes, probably due to the confounding effect of undesirable fermentation by entrobacteria or yeast.

Atriplex species/cultivars [Atriplex nummularia, A. canescens (Santa Rita) and A. canescens (Field Reserve 1)] were compared in terms of chemical composition and in vitro digestibility. The plant material was sampled at different seasons (autumn and winter) and from different sites (Hatfield in the Gauteng Province and Mier and Lovedale, both in the Northern Cape Province) and were analysed for crude protein (CP), neutral detergent fibre (NDF) and in vitro digestibility (IVOMD). The CP and IVOMD of the leaves were higher than the stem for the Atriplex species. Leaf percentage for the autumn samples was not affected by species at Hatfield and Mier, but A. canescens (Field Reserve 1) had lower leaf percentage at Lovedale as well as for winter samples at Hatfield. At Lovedale, however, A. nummularia had the highest leaf : stem ratio compared to A. canescens (Santa Rita) and A. canescens (Field Reserve 1). Atriplex nummularia had a higher CP concentration than A. canescens (Field Reserve 1) and A. canescens (Santa Rita) at both Mier and Lovedale, but species/cultivar had no effect on CP concentration at Hatfield. Autumn samples had a higher CP concentration than winter samples at both Mier and Lovedale, but season had no effect on the N concentration at Hatfield. Atriplex nummularia had a lower NDF and higher IVOMD concentration compared to A. canescens (Santa Rita) and A. canescens (Field Reserve 1). Autumn samples were less fibrous and more digestible than winter samples. Atriplex nummularia seems to be better in terms of its nutritive value compared to A. canescens (Santa Rita) and A. canescens (Field Reserve 1), with better quality forage in autumn than winter.

The aim of this study was to compare two tropical grass species, Panicum maximum and Digitaria eriantha, in terms of silage fermentation attributes and certain rumen fermentation characteristics of silage made either at the boot or full bloom stages of growth. A lower silage pH was recorded for the D. eriantha than for the P. maximum silage. Neither species nor maturity stage had a significant effect on silage ammonia nitrogen, or lactic, acetic and butyric acid concentrations. For P. maximum silage total N was higher at full bloom than at the boot stage. D. eriantha had a higher total nitrogen content than P. maximum silage at the boot stage. Rumen pH was lower in sheep fed D. eriantha than P. maximum silage. In P. maximum fed sheep, a higher rumen NH3-N concentration was recorded when silage from the full bloom stage was fed compared to silage from the boot stage. In sheep fed D. eriantha silage, higher concentrations of acetic, propionic, butyric and total volatile fatty acids in the rumen were recorded from full bloom than from the boot stage. Neither species nor stage of maturity had significantly influenced the acetic : propionic acid ratio. The results suggested no significant difference between the species, but the full bloom stage showed a higher nutritive value and better preservation compared to the boot stage silage in both D. eriantha and P. maximum silage.

Silages made from directly cut or wilted Digitaria eriantha treated with or without molasses were evaluated to determine fermentative characteristics. The grass was harvested at the boot stage of growth and the material was ensiled in 1 kg mini-silos. Treatments were arranged in a factorial design of two moisture levels (directly cut or wilted) and two molasses addition (with or without molasses). Each treatment was ensiled in 12 separate bottles. The pH of molasses added silage declined faster than the pH of silage without molasses. The pH of unwilted silages continued to decline up to day 120 post ensiling compared to wilted treatments. Lactic acid concentration was higher for molasses added silage than those made without molasses at all ensiling times, and also higher for directly cut silage than those wilted prior to ensiling. In direct cut silages, acetic acid concentration was lower for molasses added silage than those made without molasses at all ensiling times. In both silages, with or without molasses, the acetic acid concentrations were significantly higher for unwilted silage than silage wilted prior to ensiling. The ammonia nitrogen (NH3-N) as percentage of total nitrogen (N) was higher in unwilted silage than prior wilted silage without molasses, while in the presence of molasses the effect of wilting on NH3-N as percentage of total N was not significant.

This study was undertaken to determine the degradation characteristics and in vitro gas production kinetics of drought tolerant shrubs (Cassia sturtii, Atriplex nummularia and three Atriplex canescens cultivars, viz. Santa Rita, Field Reserve 1 and Rincon) growing under South African conditions (Hatfield in the Gauteng Province and Mier and Lovedale, both in the Northern Cape Province). Edible forage was incubated for 72 h to record in sacco neutral detergent fibre (NDF) degradability parameters and in vitro gas production. No significant difference was found between locations in terms of the NDF degradation parameters, except the NDF effective degradation (ED). However, the species differed in terms of the slowly degradable NDF fraction (NDF b-value) and rate of the degradation of NDF (NDF c-vlaue) in the Hatfield samples. Species differed significantly in terms of NDF ED value for samples collected at Mier. Species also differed in the rate of gas production (c) the volume of effective gas produced (EGP) and the potential extent of gas production (b) values. Atriplex nummalaria was ranked better than A. canescens (Field Reserve 1) in terms of NDF ED-value in Mier and NDF b-value in Hatfield, though the latter had shown higher c-values for samples collected in Hatfield. A similar trend was recorded in the gas production study, where A. canescens (Field Reserve 1) ranked least in terms of effective gas production and the potential extent of gas production compared to the other Atriplex species and C. sturtii. This indicates a lower feeding value of this cultivar as a ruminant feed compared to other Atriplex cultivars and C. sturtii.

This study was undertaken to determine the influence of three grazing pressures [high (HGP), medium (MGP) and low (LGP), corresponding to 30, 50 and 75 g available DM/kg BW/day, respectively] on the quality of herbage consumed by lambs grazing Lolium perenne and Dactylis glomerata pastures in spring. Feed samples collected via oesophageal fistulae at the start and end of a six-week grazing period were analyzed for nitrogen (N), ash, neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL) concentrations, and in vitro digestibility of organic matter (IVDOM). In general, the quality of diets selected by lambs grazing both L. perenne and D. glomerata pastures was lower at the end than at the start of the grazing period. For both pastures the N concentration of herbage consumed by lambs in the HGP treatment was lower than for that in the LGP treatment. For L. perenne HGP resulted in the selection of a diet with higher fibre (NDF and ADF) concentrations and consequently lower IVDOM than in the LGP treatment. In the D. glomerata pasture, higher ADF and lower IVDOM were recorded in the MGP treatment compared to the other treatments. On the D. glomerata pasture the ADL concentration of the selected forage was lower in the HGP than in the MGP or LGP treatments. Forage selected on the L. perenne pasture had generally lower N, ash, ADF and ADL concentrations than those selected from the D. glomerata pasture. However, the IVDOM of the selected L. perenne was higher than that of selected D. glomerata.

This study was undertaken to determine the influence of three grazing pressures [high (HGP), medium (MGP) and low (LGP), corresponding to 30, 50 and 75 g available DM/kg BW/day, respectively] on the performance of lambs grazing Lolium perenne and Dactylis glomerata pastures in spring. Feed intakes and average daily live weight gains (ADG in g/day) were determined for each group. In general intakes of both L. perenne and D. glomerata pastures were higher at the end of the study than at the onset. Grazing pressure had no effect on the intake of L. perenne, but on the D. glomerata pasture, HGP resulted in a decreased intake by the lambs compared to the LGP treatment. For both pasture species the ADG of the lambs were lower on the HGP compared to the MGP treatment, though intake and ADG of the lambs were higher when grazing L. perenne compared to D. glomerata.

The aim of this study was to investigate the effect of two carbohydrate sources, barley and maize, on the ruminal fermentation of Atriplex nummularia cv. De Kock fed to sheep. Barley was used as a source of rapid fermentable carbohydrates while maize was used as a moderately fermentable source. Ten rumen cannulated Merino wethers were fed different increments of ground maize and barley supplements (0%, 15%, 30%, and 45% of the ration dry matter to a basal diet of A. nummularia over four different periods. Supplementation of A. nummularia with energy tended to increase ruminal fermentation. Rumen ammonia nitrogen (NH3-N) decreased at the 30% level of supplementation, though an increase in rumen NH3-N concentration was observed for maize at the 45% level. This decrease might have been due to an improvement in microbial protein synthesis. Total rumen volatile fatty acids increased with increasing levels of both barley and maize supplementation. Evidence of the increase in volatile fatty acid production was supported by a decrease in ruminal pH values, with the barley at 45% level of supplementation yielding the lowest rumen pH values. Supplementing sheep with barely and maize at 30% level increased fermentation in the rumen of sheep fed on A. nummularia and enhanced utilisation of degradable protein available in the rumen.

The voluntary intake and in vivo digestibility of forage from Indigofera species, Medicago sativa (lucerne) and Leucaena leucocephala (Leucaena) were determined using South African Mutton Merino sheep with the aim to assess the potential nutritive value of Indigofera compared to the other two species. Both lucerne and Leucaena had higher crude protein (CP) and lower neutral detergent fibre (NDF) concentrations than Indigofera. However, the apparent dry matter digestibility (DMD%) coefficients for Leucaena were lower than either Indigofera or lucerne. The forage species also differed in terms of NDF digestibility, dry matter intake (DMI) and CP intake (g/head/d), but not in terms of neutral detergent fibre intake (NDFI). The difference between Indigofera species and Leucaena forage in terms of DM intake per unit of metabolic body weight (g/W0.75/day) and digestible organic matter intake (DOMI) was not significant, but forage DMI per unit metabolic body weight (g/W0.75/day) of both Indigofera species and Leucaena was significantly lower than DMI of lucerne. In this specific study, lack of differences between Indigofera species and Leucaena in terms of DOMI and digestible NDFI indicates that Indigofera forage would likely support similar weight gains in ruminants as those of Leucaena, but lower than those of lucerne forage.