Chemical composition and nutritive value of leaves and stems of tropical weed Chromolaena odorata

Chromolaena odorata (Siam weed) has been classified as a weed plant in West Africa. Data from C. odorata foliage after 4, 6, 8, 10 and 12 weeks of regrowth showed that the leaf fraction had a crude protein content above 194 g kg^–1 dry matter (DM) and an average leaf to stem ratio of 2·1:1. Chemical analysis of the leaf fraction of an 8‐week‐old regrowth indicated a high crude protein content (258 g kg^–1 DM) and a high degradable nitrogen content (60·7 g N kg^–1 digestible organic matter), but low neutral‐detergent fibre (331 g kg^–1 DM), acid‐detergent lignin (53·1 g kg^–1 DM), total extractable phenolic (37·1 g kg^–1 DM), extractable tannin (0·72 absorbance at 550 nm) and extractable condensed tannin (1·4 g kg^–1 DM) contents. In sacco degradability analysis of the 8‐week‐old regrowth leaf sample showed a high 48 h organic matter (935 g kg^–1 DM) and crude protein (953 g kg^–1 DM) degradability. The leaf sample had an organic matter degradability of 670 g kg^–1 DM as estimated by cumulative gas production in vitro after 24 h incubation. There was little or no phenolic‐related antinutritive factors in C. odorata. Additionally, leaf samples had no effect on rumen protozoa activity estimated as the rate of [¹⁴C]leucine Selenomonas ruminantum bacterial protein breakdown. Data from this study suggest that C. odorata leaves are of high nutritive value and might have the potential to be used as a protein supplement to ruminants. There is need for further investigation to test whether C. odorata leaves may have any deleterious effect on the host animal.     

The nutritive value of Prangos ferulacea

This study was conducted to determine the chemical composition and nutritive value of Prangos ferulacea, a plant found in the Mediterranean and Middle‐east regions, where it is used as animal fodder. Samples of mature plants were collected from S.E. Turkey. Metabolizable energy (ME) values were estimated from in vitro gas production measurements and from chemical composition. ME concentrations of the whole plant, leaves and stems were estimated to be 12·2, 11·9 and 12·7 MJ kg^?1 dry matter (DM) respectively, which compares favourably with high‐quality forages commonly used in ruminant feeding. The DM degradability of the whole plant, leaves and stems increased up until 48 h of in situ incubation, 866, 915 and 784 g kg^?1 DM respectively, but changed little between 48 and 72 h. In vitro DM and organic matter digestibility of the whole plant, leaves and stems were 0·769 and 0·806, 0·773 and 0·790, and 0·740 and 0·840 respectively. The results show that P. ferulacea may be regarded as a high‐energy forage, but further research is needed on its intake characteristics and the levels of animal performance that can be achieved from its inclusion in the diet.     

Voluntary intake,digestibility and nitrogen utilization by sheep fed ensiled forage legumes

An experiment was conducted to compare the nutritive value of a range of ensiled forage legumes. Silages were prepared from late second‐cut lotus (Lotus corniculatus), first‐cut sainfoin (Onobrychis viciifolia) and both early and late second‐cut red clover (Trifolium pratense) and lucerne (Medicago sativa). Each experimental silage was offered to six Suffolk‐cross wether lambs, aged 10 months, housed in metabolism crates. Voluntary intakes of dry matter ranged from 71 to 81 g kg^?1 liveweight^0·75 d^?1. Voluntary intakes were similar on the lotus, sainfoin and late‐cut red clover silages, but the voluntary intake on the lotus silage was significantly higher than that on the lucerne silages and early‐cut red clover silage. Digestibility of organic matter in the dry matter was highest for the lotus silage (0·650), and lowest for the sainfoin silage (0·527). Although most of the N in the sainfoin silage appeared to be in an indigestible form, N digestibility was approximately 0·70 for the other legume silages. The highest loss of N in urine, 0·75 of N intake, was recorded for lambs offered the lucerne silage. Differences in N intake, N loss in faeces and N loss in urine led to statistically significant differences in the amount of N retained, with the highest and lowest N balances recorded for the lotus (16 g N d^?1) and sainfoin (?2 g N d^?1) silages respectively. The results confirm that these high protein forages have high intake potential. While low N digestibility appears to limit the nutritional value of sainfoin, further research could formulate feeding strategies that improve the efficiency with which the protein from red clover, lucerne and lotus is utilized.     

Alpha‐tocopherol and β‐carotene in legume–grass mixtures as influenced by wilting,ensiling and type of silage additive

Effects of wilting, ensiling and type of additive on α‐tocopherol and β‐carotene contents in legume–grass mixtures were examined. Swards of birdsfoot trefoil + timothy (Bft + Ti), red clover + timothy (Rc + Ti) and red clover + meadow fescue (Rc + Mf) were harvested as a first regrowth in August 2005. Forage was wilted to a dry‐matter (DM) content of 273 g kg^?1 and ensiled without additive or with an inoculant or acid. Wilting decreased α‐tocopherol concentration by 30% in the Bft + Ti mixture (P = 0·015). Untreated Bft + Ti silage had higher α‐tocopherol content than red clover silages (56·9 vs. 34·2 mg kg^?1 DM; P = 0·015). The α‐tocopherol concentration of Bft + Ti forages increased during ensiling from 41·1 mg kg^?1 DM in wilted herbage to 56·9, 65·2 and 56·8 mg kg^?1 DM in untreated, inoculated and acid‐treated silage respectively (P = 0·015). The inoculant increased α‐tocopherol content in the red clover silages (50·1 vs. 34·2 mg kg^?1 DM; P = 0·015) compared with untreated red clover silages. Red clover mixtures had lower β‐carotene content than Bft + Ti (32·3 vs. 46·2 mg kg^?1 DM; P = 0·016), averaged over treatments. In conclusion, wilting had small effects but the use of bacterial inoculant as an additive and a Bft + Ti mixture increased α‐tocopherol concentration in the silage.     

In vitro rumen methane output of perennial ryegrass varieties and perennial grass species harvested throughout the growing season

The selection and feeding of perennial ryegrass (Lolium perenne L.) varieties (PRV) or perennial grass species (PGS) may affect enteric methane (CH₄) output because of changes in the fermentation dynamics in the rumen as a result of differences in herbage chemical composition. The objective of this study was to determine the effects of PRV and PGS harvested throughout the growing season on herbage chemical composition, and in vitro rumen fermentation variables and CH₄ output per unit of feed using a batch culture technique. Seven PRV (Experiment 1: Alto, Arrow, Bealey, Dunluce, Greengold, Malone, Tyrella) and six perennial grasses [Experiment 2: perennial ryegrass (Navan), perennial ryegrass (Portstewart), cocksfoot, meadow fescue, tall fescue, timothy; defined as PGS], managed under a simulated grazing regime, were incubated for 24 h with buffered rumen fluid in two separate experiments. The CH₄ output per unit of feed dry‐matter (DM) incubated was not affected (P > 0·05) by PRV (range of mean values across PRV of 23·9–25·3 (SEM 0·41) mL g^?1 DM) or by PGS (25·6–26·6 (SEM 0·37) mL g^?1 DM). The CH₄ output per unit feed DM disappearing during the in vitro rumen incubation was not affected by PRV (33·9–35·1 (SEM 0·70) mL g^?1 DM), and although there was an overall PGS effect (P < 0·05; 37·2–40·3 (SEM 0·71) mL g^?1 DM), none of the paired contrasts between PGS were significant when analysed using Tukey adjusted comparisons. This outcome reflected either small‐scale or a lack of treatment effects on individual herbage chemical composition (e.g. 454–483 g NDF kg^?1 DM, 215–224 g CP kg^?1 DM and 94–122 g water‐soluble carbohydrate (WSC) kg^?1 DM across PRV; 452–506 g NDF kg^?1 DM, 208–243 g CP kg^?1 DM and 73–131 g WSC kg^?1 DM across PGS) and in vitro rumen fermentation variables. Hence, these results provide no encouragement that choices among the grasses examined, produced within the management regimes operated, would reduce enteric CH₄ output per unit of feed in vivo. However, the technique utilized did not take account of animal × PRV or PGS interactions, such as potential differences in intake between animals, that may occur under farm conditions.     

Effect of harvest date on the chemical composition and nutritive value of Cerastium holosteoides

Abstract Cerastium holosteoides is a short‐lived plant often found in small proportions on dry and mesotropic semi‐natural, species‐rich grassland communities. To obtain more information about its nutritive value, two experiments on Arrhenatheretum elatioris grassland were carried out to examine the effect of harvest date on in vitro organic matter digestibility (IVOMD), neutral‐detergent fibre (NDF), acid‐detergent fibre (ADF), acid‐detergent lignin (ADL), estimated net energy for lactation (NEL) and crude protein (CP) concentrations of C. holosteoides, and selection of this plant by dairy cows grazing on semi‐natural grassland. C. holosteoides starts flowering in spring and continuously develops new flowers on new branches throughout the summer. Harvests were made in relation to particular growth stages of Dactylis glomerata present in the sward: (A) tillering; (B) stem elongation; (C) ear emergence; (D) flowering; and (E) ripening. Chemical composition and nutritive value were evaluated in 1998 and 1999. With advancing maturity, IVOMD of C. holosteoides decreased from 0·771 at growth stage A to 0·485 at growth stage E. At the same time, CP concentration decreased from 153 to 69 g kg^?1 dry matter (DM) and estimated NEL concentration from 6·00 to 4·07 MJ kg^?1 DM. With advancing maturity, there was a significant increase in NDF, ADF and ADL concentrations. In the summer harvest season, C. holosteoides contained significantly higher NDF, ADF and ADL concentrations, lower NEL concentration and had a lower IVOMD value than in the spring. Differences between years were also found for IVOMD and for NDF, ADF, ADL and NEL concentrations. In a grazing experiment in the year 1999, at growth stage B, Simmental cows grazed an A. elatioris sward in which the main species was D. glomerata (0·092), and the proportion of C. holosteoides was 0·034. C. holosteoides was, on average, grazed by cows to the same relative extent as other species in the sward.     

Effects of intercropping and fertilizer application on the yield and nutritive value of maize and amaranth forages in Nigeria

Maize and amaranth forages, produced during the wet season, have the potential to bridge the gap in forage supply to ruminants during the dry season in Nigeria. In two growing seasons (2006 and 2007), effects of intercropping and fertilizer application on dry matter (DM) yield and chemical composition of forages, and land use efficiency, were studied in two experiments. The digestibility of sun‐dried or ensiled maize, amaranth or maize–amaranth mixtures was measured using West African dwarf sheep in a third experiment. Maize showed a higher response to fertilizer application than amaranth or maize–amaranth mixtures. With fertilizer application, DM yield varied significantly (P < 0·05) between species and intercropped mixtures. Dry matter yield ranged from 7·1 (amaranth) to 12·6 t ha^?1 (maize) in 2006 and 6·9 (amaranth) to 11·3 t ha^?1 (70:30 maize–amaranth population mixture) in 2007. Crude protein (CP) concentration of whole plants ranged from 99·0 (maize) to 227·0 g kg^?1 DM (amaranth). Dry matter digestibility values of sun‐dried maize, sun‐dried maize:amaranth 50:50 mixture, sun‐dried amaranth, ensiled maize, ensiled maize:amaranth 50:50 mixture and ensiled amaranth were 0·718, 0·607, 0·573, 0·737, 0·553 and 0·526 respectively. Intercropping increased forage yield and land use efficiency compared to amaranth but had no yield advantage over maize. Although DM digestibility of maize was higher than that of amaranth or the maize:amaranth mixture, digestible CP yield ha^?1 was higher with amaranth in the cropping mixture, showing that amaranth could complement maize in systems where CP is the limiting factor to livestock production.     

Characteristics of baled silage made from first and second harvests of wilted and severely wilted forages

First and second harvests of lucerne (Medicago sativa L.), perennial ryegrass (Lolium perenne L.) and a lucerne–perennial ryegrass mixture [80 or 144 g kg^?1 dry matter (DM) of ryegrass] at the first and second harvests were cut and conditioned, wilted to 500 or 700 g DM kg^?1 then baled and stretch‐wrapped for silage on the same dates. Lucerne bales were denser (411 kg m^?3) than bales of perennial ryegrass (331 kg m^?3) (P < 0·05). After an 8‐month storage period, silage made from high DM‐content forage had a higher concentration of neutral‐detergent fibre (NDF) and was less digestible than that made from low DM‐content forage. Daily DM intakes by beef steers, when the silages of the second harvest were fed ad libitum, were 31·2, 31·2 and 22·3 g kg^?1 live weight for lucerne, lucerne–perennial ryegrass mixture and perennial ryegrass silages, respectively (P < 0·01), when the herbage had been wilted to 500 g kg^?1. In vivo digestibility of NDF in the lucerne–perennial ryegrass mixture silage (0·587) was significantly lower than that of perennial ryegrass silage (0·763) but higher than lucerne silage (0·518). Higher intakes of baled lucerne silage tended to offset its lower digestibility values. Lucerne–perennial ryegrass mixture silage had a higher DM and NDF digestibility than lucerne silage, indicating perhaps the presence of associative effects.     

Effects of a stay-green trait on the concentrations and stability of fatty acids in perennial ryegrass

Abstract Three experiments were conducted to evaluate the effect of a stay‐green trait in perennial ryegrass (Lolium perenne) on concentrations of fatty acids as well as their susceptibility to peroxidation during wilting and to biohydrogenation by rumen bacteria. Fatty acid concentrations were recorded in stay‐green and corresponding normal perennial ryegrass selection lines over eight cuts during 1998. There was a progressive increase in total fatty acid concentrations [from 20·8 to 34·6 g kg^?1 dry matter (DM)] and the proportion of fatty acids as α‐linolenic acid (from 0·62 to 0·70 g g^?1) from early to late season. A second study compared fatty acid concentrations in stay‐green and normal herbage that was wilted for up to 48 h. There was a loss of 0·2–0·3 g g^?1 fatty acids during 48 h of wilting and a small reduction in the rate of loss of α‐linolenic acid in stay‐green perennial ryegrass compared with normal herbage (0·223 vs. 0·290 g g^?1 lost after 48 h). Stay‐green and normal perennial ryegrasses were offered to grazing lambs in a third study. Higher concentrations of trans‐vaccenic acid and conjugated linoleic acid in plasma from lambs offered less mature grass in the pre‐experimental period than during the experiment are considered to reflect a greater supply of precursor (linoleic acid). There were higher concentrations of conjugated linoleic (0·0070 vs. 0·0039 g l^?1) and linoleic (0·092 vs. 0·070 g l^?1) acids, without an increase in trans‐vaccenic acid, in plasma from lambs grazing stay‐green perennial ryegrass than normal perennial ryegrass. This suggests that the stay‐green trait affected the rate of degradation of fatty acids in the rumen. These results demonstrate the potential for obtaining proportionately large differences in fatty acid profiles of ruminant products by altering grassland management.     

Effects of Lactobacillus buchneri as a silage inoculant or probiotic on in vitro organic matter digestibility,gas production and volatile fatty acids of low dry‐matter whole‐crop maize silage

Our objective was to investigate Lactobacillus buchneri as a silage inoculant or probiotic on in vitro ruminal measurements of low dry‐matter whole‐crop maize silage. In vitro gas production was conducted using untreated (without inoculant) and inoculated (treated with L. buchneri CNCM I‐4323 at 1 × 10⁵ cfu g^?1 of fresh forage) maize silages (wet‐ground) incubated with three different ruminal inocula, in a 2 × 3 factorial arrangement. Ruminal fluids were collected from wethers consuming (i) untreated maize silage (RF‐U); (ii) inoculated maize silage (RF‐I); and (iii) untreated maize silage with a daily dose of L. buchneri CNCM I‐4323 administered directly into the rumen (1 × 10⁷ cfu g^?1 of supplied silage [LB‐probiotic]). Gas production was consistently higher when inoculated silage was used as the substrate of fermentation, compared to the untreated silage. When untreated silage was used as substrate, the total volatile fatty acid concentration was higher using RF‐I and LB‐probiotic inocula, compared to the RF‐U inoculum, at 9 hr and at 48 hr of fermentation. It is concluded that L. buchneri should be used as a silage inoculant rather than as a probiotic because it alters fermentation within the silo thereby improving silage quality and enabling some benefits for ruminal fermentation.     

Diet selection of dry and lactating beef cows grazing extensive pastures in late autumn

The diet selection, made by twelve dry and twelve lactating spring‐calving Salers beef cows at the end of the grazing season on an extensively grazed natural mountain pasture in central France, was compared. Sward structure, selection bites, daily grazing time and digestibility of the diet were measured in mid‐October (P₁) and mid‐November (P₂). Live weights were measured twice monthly throughout the experiment. Daily milk production was assessed in the week before the grazing behaviour measurements. Lactating cows grazed more selectively than dry cows: they took more bites on green patches (0·20 vs. 0·13 of total bites, P < 0·01; Jacob's selectivity index: 0·13 vs. ?0·25, P < 0·001), which is consistent with the higher overall nitrogen concentration in faeces (18·1 vs. 17·3 g kg^?1 DM, P < 0·05). Lactating cows tended to slightly increase their daily grazing time compared with dry cows (on average 9·9 vs. 9·5 h, P = 0·07) and grazed faster in mid‐November (74 vs. 69 bites min^?1, P < 0·05). The lactating cows lost more live weight (?24 vs. ?12 kg cow^?1, P < 0·05) between P₁ and P₂. A positive correlation was found between consumption of green patches by lactating cows and their daily milk production in P₂ (r = 0·574, P = 0·05), whereas no correlation occurred between individual milk production and liveweight loss. Dry cows were less selective, which supports management practices that promote the use of cows with low requirements on extensively grazed pastures in late season.     

Effect of formic acid and a bacterial inoculant on the amino acid composition of grass silage and on animal performance

An Italian ryegrass and hybrid ryegrass sward was harvested on 11 May 1994. The mean dry‐matter (DM) content of the herbage was 197 g kg^–1 fresh matter (FM), and mean nitrogen and water‐soluble carbohydrate contents were 20 and 272 g kg^–1 DM respectively. Approximately 72% of total nitrogen (TN) was in the form of protein‐nitrogen. The herbage was treated with either no additive, formic acid (3·3 l t^–1) (Add‐F, BP) or inoculant (2·3 l t^–1) (Live‐system, Genus) and ensiled in 100 t silos. Changes in effluent composition with time showed that silage fermentation and protein breakdown were delayed by treatment with formic acid. Formic acid and inoculant treatments also inhibited amino acid catabolism during ensilage. All silages were well fermented at opening with pH values < 4·0 and ammonia‐N concentrations of ≤ 50 g kg^–1 TN after 120 d ensilage. Treatment had an effect on protein breakdown as measured by free amino acid concentration, with values of 21·5, 18·2 and 13·2 mol kg^–1 N at opening (191 d) for untreated, formic acid‐treated and inoculated silages respectively. Amino acid catabolism occurred to the greatest extent in untreated silages with significant decreases in glutamic acid, lysine and arginine, and increases in gamma amino butyric acid and ornithine. The silages were offered ad libitum without concentrate supplementation to thirty‐six Charolais beef steers for a period of 69 d (mean live weight 401 kg). Silage dry‐matter intakes and liveweight gains were significantly (P < 0·05) higher on the treated silages. Silage dry‐matter intakes were 7·42, 8·41 and 8·23 kg d^–1 (s.e.d. 0·27) with liveweight gains of 0·66, 0·94 and 0·89 kg d^–1 (s.e.d. 0·058) for untreated, formic acid‐treated and inoculated silage‐fed cattle respectively. In conclusion, additives increased the intake of silage and liveweight gain by the beef steers, and it is suggested that this may be caused in part by the amino acid balance in these silages.     

Nutritive value of barley/kale bi-crop silage for lactating dairy cows

Six mid‐lactation multiparous Holstein–Friesian dairy cows were used to examine the potential of a fermented whole‐crop barley (Hordeum vulgare)/kale (Brassica oleracea) bi‐crop as a feed compared with a first‐cut perennial ryegrass silage. The barley/kale bi‐crop was grown as a strip intercrop, and was harvested and ensiled as an intimate mixture [0·80 barley and 0·20 kale on a dry‐matter (DM) basis]. Animals were offered ad libitum access to one of three experimental diets in a duplicated Latin Square design experiment: (i) Bi‐crop (the barley/kale bi‐crop); (ii) Grass (the grass silage); and (iii) Mix (a 1:1 fresh mixture of Bi‐crop and Grass). All animals also received a standard dairy concentrate at a rate of 4 kg d^?1 in equal portions at each of two milkings. The Bi‐crop and Grass silages contained 346 and 293 g DM kg^?1, 108 and 168 g crude protein kg^?1 DM, 268 and 36 g starch kg^?1 DM, and had pH values of 3·87 and 3·80 respectively. Animals offered the two bi‐crop silage‐containing diets consumed more forage DM than those offered grass silage (14·6, 14·9 and 12·6 kg DM d^?1 for Bi‐crop, Mix and Grass respectively; s.e.d. 0·45, P < 0·01) and yielded more milk (24·0, 23·9, 22·6 kg d^?1 for Bi‐crop, Mix and Grass respectively; s.e.d. 0·26, P < 0·01). However, differences in the partitioning of dietary nitrogen towards milk protein and away from excretion in urine suggest a more efficient (rumen) utilization of feed protein by animals offered diets containing the bi‐crop silage. It is concluded that, despite having a low crude protein concentration, barley/kale bi‐crop silage offers excellent potential as a feed for lactating dairy cows.     

The value of malt distillers' grains ensiled with molassed sugar beet pellets as a feed for dairy cows

In one experiment twenty‐four Holstein Friesian cows, average 43 d post‐partum, were used in a changeover design experiment to evaluate the replacement of a cereal‐based concentrate supplement (C) by an ensiled mixture (MGBP) of malt distillers’ grains and molassed sugar beet pellets. The cows were offered grass silage ad libitum [dry matter (DM) content 170 g kg^?1, crude protein (CP) concentration 160 g kg DM^?1, metabolizable energy (ME) concentration 10·9 MJ kg DM^?1] and either C or MGBP at one of three levels (3, 6, 9 kg DM d^?1). The composition of C and MGBP were DM content: 853 and 296 g kg^?1, CP concentration: 202 and 187 g kg DM^?1, ME concentration: 12·6 and 10·8 MJ kg DM^?1 respectively. The cows ate all the C supplement but the intakes of MGBP were 2·7, 4·9 and 6·4 kg DM d^?1 for the 3, 6 and 9 kg DM d^?1 levels of MGBP respectively. Total DM intakes (kg d^?1) were 12·5, 15·6, 18·2 for treatments 3‐C, 6‐C and 9‐C and 13·1, 14·4 and 15·9 (s.e., 0·90) for treatments 3‐MGBP, 6‐MGBP and 9‐MGBP respectively. Milk yields (kg d^?1) for treatments 3‐C, 6‐C and 9‐C were 19·9, 23·2 and 24·2, respectively, and for treatments 3‐MGBP, 6‐MGBP and 9‐MGBP were, 20·3, 21·3 and 23·0 respectively (s.e., 1·05). Milk fat contents (g kg^?1) for treatments 3‐C, 6‐C and 9‐C were 42·8, 42·3, 43·5 respectively and for treatments 3‐MGBP, 6‐MGBP and 9‐MGBP were 39·5, 38·7 and 38·2 (s.e, 1·86), respectively, and milk protein contents (g kg^?1) for treatments 3‐C, 6‐C and 9‐C were 30·5, 30·6, 31·8, respectively, and for 3‐MGBP, 6‐MGBP and 9‐MGBP were 30·0, 30·8 and 31·2 (s.e., 0·66) respectively. Milk yield and milk protein contents were significantly higher for the higher levels of supplementary feeding but there was no difference between the types of supplement. The milk fat contents were significantly lower on the MGBP than C supplements. In a second experiment fifteen Holstein Friesian cows, average 126 d post‐partum, were used in a changeover experiment to evaluate the replacement of all (treatment M) or half (treatment MS) of the grass silage (S) in their diet by a mixture of MGBP and straw. All cows received 5·1 kg DM d^?1 of concentrate feed. Forage DM intakes were 8·3, 11·2 and 14·2 kg DM d^?1 for the S, MS and M treatments respectively. Milk yields (kg d^?1) for S, MS and M treatments were 17·0, 19·4 and 20·0 (s.e., 0·56) respectively. Corresponding contents of milk fat and protein (g kg^?1) were 42·0, 41·4, 38·6 (s.e., 0·37) and 33·8, 34·1, 34·2 (s.e., 0·42). Ensiled mixtures of malt distillers’ grains and molassed sugar beet pellets can be used to replace some of the conventional concentrates or grass silage for dairy cows giving moderate yields without a loss of production.     

Determination of nutritive value of forages in south Texas using an in vitro gas production technique

The objectives of this study were to use the in vitro gas production (IVGP) technique to evaluate the pattern and parameters of anaerobic fermentation of forages from south Texas pastures throughout the year to (i) obtain empirical relationships between the IVGP technique fermentation parameters and chemical composition of the forages and (ii) develop equations to compute total digestible nutrients (TDN). During four consecutive years (2006–2009), forage samples were collected monthly (n = 39) at the King Ranch, TX, and chemical analyses and IVGP were obtained. For 2006, 2007, 2008 and 2009, the average lag times, h, were 6·47 ± 0·54, 7·75 ± 0·65, 7·49 ± 2·01 and 5·44 ± 1·46, and the average ratio of millilitre of gas per milligram of dry matter was 0·41 ± 0·11, 0·34 ± 0·09, 0·34 ± 0·07 and 0·26 ± 0·10 respectively. There was a moderate negative correlation (r = ?0·53) between lignin and neutral detergent fibre (NDF) and a moderate positive correlation (r = 0·58) between crude protein and NDF digestibility. The predicted fractional passage rate (kp) by the large ruminant nutrition system model using the level 2 solution was on average 0·0366 h^?1. The average computed TDN assuming a kp of 0·04 h^?1 was 55·9%. We concluded the IVGP technique may be used to predict TDN values of warm‐season forages.     

Storage of small bale silage and haylage – influence of storage period on fermentation variables and microbial composition

An experiment investigating changes in fermentation variables and microbial composition during storage of small‐bale silage and haylage was performed. Haylage was defined as silage with a dry‐matter (DM) content exceeding 500 g kg^?1. Grass was wilted to three different DM contents, and baled into silage (350 g DM kg^?1), haylage with a low DM content (550 g kg^?1) and haylage with high DM content (700 g kg^?1) in small rectangular‐shaped bales (0·80 m × 0·48 m × 0·36 m) that were individually wrapped. Bales were stored for short (2 months) or long (14 months) periods before opening and sampling. Silage had higher concentrations of fermentation products and a lower pH than either of the two haylage types. In general, long‐term storage influenced all fermentation variables except concentrations of butyric acid and succinic acid, and yeast counts were higher after 14 months than 2 months of storage. However, silage changed in more fermentation variables during storage than the two haylage types. Although differences between short‐ and long‐term stored silage were found, linear correlations between short‐ and long‐term stored bales were present for all chemical variables. Pearson's correlation coefficients were highest for lactic acid, followed by pH.     

Application of long‐chain alcohols as diet‐composition markers in sheep fed on grass–white clover and heather–gorse plant species

Utilization of long‐chain alcohols (LCOH) as diet‐composition markers in sheep consuming six diets composed of improved pasture species (Lolium perenne and Trifolium repens) with heather–gorse components (Erica spp., Calluna vulgaris and Ulex gallii) was evaluated. Twenty‐four adult cross‐bred sheep were housed in individual stalls. Diet composition was estimated from LCOH concentrations, combined or not with alkanes and long‐chain fatty acid (LCFA) data using least‐squares procedures. Prior to calculations, faecal concentrations were corrected using mean treatment (faecal recovery 1, FR1) recoveries and mean recoveries across diets (FR2). Estimates were compared with those obtained without faecal correction (FR0) and known values. Large differences between plant species and plant parts were found in LCOH patterns and total LCOH concentrations. LCOH provided complementary information to that given by alkanes and LCFA. Even‐chain LCOH comprised the largest fraction, representing on average 0·894 of total concentrations. Faecal recovery was incomplete and tended to increase with carbon‐chain length (CCL) in a curvilinear manner (FR = ?7·872 + 0·580 × CCL ? 0·010 × CCL²; P < 0·001; r² = 0·752). Diet composition influenced (P < 0·001) LCOH recovery, although variability within (CV of 9·0%) and between (CV of 13·3%) diets was low. Accuracy of estimates was influenced (P < 0·001) by faecal‐correction method and markers used, and the best estimate was obtained combining LCOH and alkanes. Improvement in estimate accuracy can be achieved if suitable correction of LCOH faecal concentrations is performed prior to calculations. Results indicated that LCOH showed lower dependence than alkanes and LCFA on the use of accurate faecal‐correction data.     

A comparison of two grassland-based systems for autumn-calving dairy cows of high genetic merit

A full lactation study compared the performance of autumn‐calving dairy cows of high genetic merit under two contrasting systems of milk production: high forage (HF) and high concentrate (HC). During the winter, animals on system HF were offered a silage with a high feeding value characteristics, supplemented with 5·5 kg of concentrate [crude protein content of 280 g kg^?1 dry matter (DM)] through an out‐of‐parlour feeding system. From 14 March, these animals were given increasing access to grazing, achieving 24‐h turnout on 15 April. Thereafter, until day 305 of lactation, these animals were offered a large daily herbage allowance (23·0 kg grass DM cow^?1, measured above a height of 4·0 cm), supplemented with 0·5 kg d^?1 of a ‘high‐magnesium’ concentrate. During the winter, animals on system HC were offered a silage of medium feeding value, mixed with ≈14·0 kg of concentrate d^?1 (crude protein content of 202 g kg^?1 DM) in the form of a complete diet. These animals commenced grazing on 9 April, achieving 24‐h turnout on 18 April. From 18 April until 9 June, daily herbage allowances and concentrate feed levels were 17·0 kg DM and 5·0 kg respectively; thereafter, and until day 305 of lactation, these daily allowances were reduced to 15·0 kg of herbage DM and 4·0 kg of concentrate. Animal performance during the first 305 days of lactation for systems HF and HC, respectively, were as follows: total concentrate DM inputs, 842 and 2456 kg; total silage DM intakes, 2205 and 1527 kg; total grass DM intakes, 3019 and 2044 kg; total feed DM intake, 6061 and 6032 kg and total milk output, 7854 and 8640 kg. Total milk output per cow with system HF was 786 kg lower than for system HC, despite similar total DM intakes, suggesting a greater total nutrient requirement with the former to support a given milk production. However, the study confirms that relatively similar levels of animal performance can be achieved from systems based on very different sources of nutrient supply.     

Changes in the physiology and feed quality of cocksfoot (Dactylis glomerata L.) during regrowth

Abstract A glasshouse study was undertaken to determine the physiological and morphological changes in cocksfoot (Dactylis glomerata L.) during regrowth after defoliation. Individual plants were arranged in a mini‐sward in a randomized complete block design. Treatments involved harvesting each time one new leaf had expanded (one‐leaf stage), up to the six‐leaf stage, with the plants separated into leaf, stubble (tiller bases) and roots. Stubble and root water‐soluble carbohydrate (WSC), stubble and leaf dry matter (DM), tiller number per plant and leaf quality (crude protein (CP), estimated metabolizable energy (ME) and mineral content) were measured to develop optimal defoliation management of cocksfoot‐based pastures. WSC concentration in stubble and roots was highest at the five‐ and six‐leaf stages. Mean WSC concentration (g kg^?1 DM) was greater in stubble than roots (32·7 ± 5·9 vs. 9·4 ± 1·5 respectively). There was a strong positive linear relationship between plant WSC concentration and leaf DM, root DM and tillers per plant after defoliation (Adj R² = 0·72, 0·88 and 0·95 respectively). Root DM plant^?1 and tiller DM tiller^?1 decreased immediately following defoliation and remained low until the three‐leaf stage, then increased from the four‐leaf stage. Tillers per plant remained stable until the four‐leaf stage, after which they increased (from 9·9 ± 0·5 to 15·7 ± 1·0 tillers plant^?1). Estimated metabolizable energy concentration (MJ kg^?1 DM) was significantly lower at the six‐leaf stage (11·01 ± 0·06) than at any previous leaf regrowth stage, whereas CP concentration (g kg^?1 DM) decreased with regrowth to the six‐leaf stage. Both the levels of ME and CP concentrations were indicative of a high quality forage throughout regrowth (11·37 ± 0·04 and 279 ± 8·0 for ME and CP respectively). Results from this study give a basis for determining appropriate criteria for grazing cocksfoot‐based pastures. The optimal defoliation interval for cocksfoot appears to be between the four‐ and five‐leaf stages of regrowth. Delaying defoliation to the four‐leaf stage allows time for replenishment of WSC reserves, resumption of root growth and an increase in tillering, and is before herbage is lost and quality falls due to onset of leaf senescence.     

Effect of feed space allowance and period of access to food on dairy cow performance

Two experiments were conducted to examine the ‘long‐term’ effect of feed space allowance and period of access to feed on dairy cow performance. In Experiment 1, three horizontal feed space allowances (20, 40 and 60 cm cow^?1) were examined over a 127‐d period (14 cows per treatment). In Experiment 2, 48 dairy cows were used in a continuous design (10‐week duration) 2 × 2 factorial design experiment comprising two horizontal feed space allowances (15 and 40 cm cow^?1), and two periods of access to feed (unrestricted and restricted). With the former, uneaten feed was removed at 08·00 h, while feeding took place at 09·00 h. With the latter, uneaten feed was removed at 06·00 h, while feeding was delayed until 12·00 h. Mean total dry‐matter (DM) intakes were 19·0, 18·7 and 19·3 kg cow^?1 d^?1 with the 20, 40 and 60 cm cow^?1 treatments in Experiment 1, and 18·1 and 18·2 kg cow^?1 d^?1 with the ‘restricted feeding time’ treatments, and 17·8 and 18·1 kg d^?1 with the ‘unrestricted feeding time’ treatments (15 and 40 cm respectively) in Experiment 2. None of milk yield, milk composition, or end‐of‐study live weight or condition score were significantly affected by treatment in either experiment (P > 0·05), while fat + protein yield was reduced with the 15‐cm treatment in Experiment 2 (P < 0·05). When access to feed was restricted by space or time constraints, cows modified their time budgets and increased their rates of intake.