Relationship of phenotypic variation in sorghum to nutritive value of crop residues

Improvements in dry matter digestibility of crop residues contribute to greater productivity of livestock consuming dual-purpose sorghums (Sorghum bicolor L. Moench). Delayed leaf senescence (stay-green), brown-midrib (bmr), leaf disease resistance, and high yield are among sorghum phenotypic traits that could enhance nutritive value of crop residues. The objective was to evaluate nutritive value and hydrocyanic acid potential (HCN-p) of leaf or stem components of crop residues of sorghum lines and hybrids representing differences in phenotypic traits. Four replications of eight or more lines and hybrids made up a randomized complete block design during 2 years in central Texas. Dry matter yield, dry weight loss after extraction in water and incubation in rumen, and fiber concentrations of leaves and stems were measured after grain harvest under field conditions. In addition, HCN-p of axillary branches and mature leaves was quantified. Sample weight loss in water extractions without incubation in rumen was negatively correlated with fiber concentrations, which were measured as the sample weights remaining after extraction in neutral (NDF) and acidic (ADF) detergent solutions. Greater concentrations of water-extractable dry matter and lower concentrations of NDF and ADF were observed for stay-green than for bmr or lines that senesced under drought. Yet, the sum of water-extractable dry matter plus ensuing weight loss during 7 days in rumen, expressed as yield ha⁻¹ of leaf and stem digestible dry matter, was not consistently greater for stay-green than drought-susceptible lines. In addition, the yield of the sum of water-extractable and 7-day rumen losses of stay-green lines was comparable to or less than the bmr line. Under conditions in which leaf senescence varied little, analyses of nutritive value indicated water-extractable dry matter was enhanced and fiber concentrations were reduced in crop residues of stay-green compared to senescent lines.     

Nitrogen in the detergent fibre fractions of temperate legumes and grasses†

Data are few on concentrations of nitrogen (N) in the cell wall and lignocellulose (neutral- and acid-detergent fibre (NDF and ADF), respectively) of herbage. Herbage N can be partitioned into neutral- and acid-detergent soluble and insoluble N to crudely estimate rapidly degradable (N soluble in neutral detergent), slowly degradable (neutral-detergent fibre N (NDFN) minus acid-detergent fibre N (ADFN), herein termed available fibre N (AFN)), and indigestible N (ADFN) in the rumen. Our objective was to examine the effects of herbage species, maturity stage, and plant part on N in the NDF and ADF of lucerne (Medicago sativa L.), red clover (Trifolium pratense L.), timothy (Phleum pratense L.), and smooth bromegrass (Bromus inermis Leyss.). Herbage was harvested at four 2-week intervals during spring of 1984 and 1985. Leaves, stems and total herbage were analysed for total N, and N in NDF and ADF. Concentrations of N in ADF in leaves, stems, and total herbage of lucerne and clover were twice that of grass ADF. This may be due to greater lignin concentrations generally reported in legumes. Concentrations of NDFN in leaves of lucerne, clover, timothy, and bromegrass were 9–8, 26.4, 8.6, and 6.4 g kg^?1 of NDF, respectively, averaged over harvests and years, whereas stem concentrations were 4.2, 4.6, 32, and 2.4 g kg^?1 of NDF, respectively. Leaf concentrations of ADFN in lucerne, clover, timothy, and bromegrass were 4.6, 5.3, 20, and 1.6 g kg^?1 of ADF, respectively, averaged over harvests and years, whereas stem concentrations were 3.4, 33, 14, and 14 g kg-’of ADF, respectively. As a proportion of the total N, NDFN and ADFN increased with plant maturity in leaves, stems, and herbage. In stems, 49% of NDFN was ADFN, whereas in leaves only 21% of the NDFN was ADFN. The larger portion of ADFN in stems probably reflects the larger proportion of lignified xylem and other structural tissues, which have a greater proportion of lignified secondary cell walls, whereas the greater proportion of NDFN in leaves may mirror the greater amount of mesophyll cells with primary cell walls. More than 80% of the total N in leaves, stems, and herbage was in the cell solubles, which may be rapidly ruminally degradable.     

Compositional variation amongst sorghum hybrids: Effect of kafirin concentration on metabolizable energy

Kafirins are stored proteins that negatively affect the nutritional quality of sorghum grain. Kafirin concentration and other chemical characteristics were determined in 12 sorghum hybrids and varied significantly, from 58% (HB1) to 42% (HB12) as percent total protein. Kafirin concentration correlated negatively with crude protein (CP) (−0.49), with acid detergent fiber (−0.40), apparent metabolizable energy (−0.61), and true metabolizable energy corrected for N (−0.63). HB12 was the hybrid with the lowest content of kafirins, amylose and tannins, and the highest content of apparent metabolizable energy. No differences were observed in the concentration of starch, but differences were found in apparent metabolizable energy (3325–2944 kcal kg⁻¹) probably due to a greater availability of starch, related to differences in kafirin concentration.     

Optimization for enzyme-retting of flax with pectate lyase

Flax (Linum usitatissimum L.) is an important commercial crop that supplies both linseed and bast fibers for multiple applications. Retting, which is a microbial process, separates industrially useful bast fibers from non-fiber stem tissues. While several methods (i.e., water- and dew-retting) are used to ret flax, more recently enzymes have been evaluated to replace methods used currently. Alkaline pectate lyase (PL) from the commercial product BioPrep 3000 and ethylenediaminetetraacetic acid (EDTA) from Mayoquest 200 as a calcium chelator were used in various formulations to ret flax stems. Retted stems were then mechanically cleaned through the USDA Flax Fiber Pilot Plant and passed through the Shirley Analyzer. The PL and chelator effectively retted flax from both fiber flax and linseed stems, and the use of enzyme plus chelator retted flax stems better than either component alone. Fiber yield and strength were greater than retting with a mixed-enzyme product that contained cellulases. Retting with PL and chelator was optimized based on fine-fiber yield, remaining shive content, and fiber properties. PL at levels of about 2% of the commercial product for 1 h at 55 °C followed by treatment with 18 mM EDTA for 23–24 h at 55 °C provided the best fibers based on these criteria. Yield and fiber properties determined by these tests were not improved with PL levels of 5% of the commercial product.     

优质青贮玉米自交系筛选与评价

以448份玉米自交系为材料,对玉米全株的品质含量指标蛋白、淀粉、中性洗涤纤维(NDF)及酸性洗涤纤维(ADF)进行评价,筛选高蛋白/淀粉、低纤维的青贮玉米自交系。结果表明,在所有供试材料中,蛋白含量变化不大,淀粉含量与纤维(NDF、ADF)含量极显著负相关。以淀粉、NDF和ADF品质含量为指标,通过聚类分析,筛选出7份高淀粉(47.50%~51.20%)、低纤维(ADF为9.08%~12.93%,NDF为26.67%~31.07%)含量的青贮玉米自交系,分别为P124-3、P125-12、P128-1、P132、13634-3、12099-2和12906-1。     

6种千斤拔不同生育期的营养价值分析

测定了腺毛千斤拔、宽叶千斤拔、海南千斤拔、球穗千斤拔、大叶千斤拔Ⅰ、大叶千斤拔Ⅱ的粗蛋白质（CP）、酸性洗涤纤维（ADF）、中性洗涤纤维（NDF）、粗脂肪（EE）、粗灰分（Ash）含量,以探讨其养分含量随生育期的变化动态。结果表明,各种养分含量随生育期的推移而变化,其变化趋势因千斤拔种类而异,但峰值多出现在开花期和结荚期。6种叶片的CP平均含量为18.55％,ADF为38.66％,NDF为47.10％,EE为3.75％,Ash为5.35％。总体来看,千斤拔叶片具有较高的营养价值,其营养价值的高低和生长发育有关。     

Absorption of color additives and settling volume in water of blue-green alga,ishikurage (Nostoc commune)

The properties of ishikurage (Nostoc commune) and other algae were compared. Ishikurage and suizenji nori (Aphanothece sacrum) absorbed much more amaranth than others. They have a high settling volume (SV) in water. The high SV of ishikurage is attributable to its neutral detergent fiber (NDF). The acid detergent fiber (ADF) from the alga had a high amaranth absorption. However the absorption by the ADF did not explain the absorption by ishikurage.The results suggest that ishikurage may have a nutritional significance as a source of dietary fiber.     

Modeling chickpea growth and development: Nitrogen accumulation and use

Quantitative information regarding nitrogen (N) accumulation and its distribution to leaves, stems and grains under varying environmental and growth conditions are limited for chickpea (Cicer arietinum L.). The information is required for the development of crop growth models and also for assessment of the contribution of chickpea to N balances in cropping systems. Accordingly, these processes were quantified in chickpea under different environmental and growth conditions (still without water or N deficit) using four field experiments and 1325 N measurements. N concentration ([N]) in green leaves was 50 mg g⁻¹ up to beginning of seed growth, and then it declined linearly to 30 mg g⁻¹ at the end of seed growth phase. [N] in senesced leaves was 12 mg g⁻¹. Stem [N] decreased from 30 mg g⁻¹ early in the season to 8 mg g⁻¹ in senesced stems at maturity. Pod [N] was constant (35 mg g⁻¹), but grain [N] decreased from 60 mg g⁻¹ early in seed growth to 43 mg g⁻¹ at maturity. Total N accumulation ranged between 9 and 30 g m⁻². N accumulation was closely linked to biomass accumulation until maturity. N accumulation efficiency (N accumulation relative to biomass accumulation) was 0.033 g g⁻¹ where total biomass was <218 g m⁻² and during early growth period, but it decreased to 0.0176 g g⁻¹ during the later growth period when total biomass was >218 g m⁻². During vegetative growth (up to first-pod), 58% of N was partitioned to leaves and 42% to stems. Depending on growth conditions, 37–72% of leaf N and 12–56% of stem N was remobilized to the grains. The parameter estimates and functions obtained in this study can be used in chickpea simulation models to simulate N accumulation and distribution.     

Effect of chloride in irrigation water and form of nitrogen fertilizer on Virginia (flue-cured) tobacco

One of the main sources of considerable amounts of chloride to soils is irrigation water. The responses of tobacco (Nicotiana tabacum L.) to chloride are varied and inconsistent depending on the tobacco type, variety and methods of fertilization, cultivation and harvesting used. In this work, the impact of the interaction between four chloride levels (10, 20, 40, 80 mg L⁻¹) in irrigation water and three nitrogen fertilizer forms (NO₃–N 100%, NH₄–N 100% and NO₃–N 50%:NH₄–N 50%) on growth, agronomic and chemical characteristics of Virginia tobacco was evaluated over 2 years (1999, 2000) in an outdoor pot experiment. The results showed that the adverse influence of chloride in irrigation water on plant height and number of leaves per plant was already substantial above 40 mg L⁻¹, within 30 days after transplanting. In this period, visual toxicity symptoms of chloride appeared on the lower leaves of plants treated with ammonium nitrogen. In addition, the effect of chloride on flowering time, chlorophyll content of leaves, aboveground fresh weight of plant, total cured product yield and chemical characteristics, depended on the form of nitrogen, with nitrate nitrogen restricting the detrimental effects of chloride in irrigation water up to 40 mg L⁻¹. The reduced yield of cured product at 80 mg L⁻¹ was the result of the adverse effects of chloride on the leaves of the middle and upper stalk position. Leaf chloride concentration was highest in the upper leaves and increased linearly with the increase of chloride level in irrigation water at each leaf position on the stalk and this increase was more rapid as ammonium nitrogen percentage was increased. Chloride increased the concentration of reducing sugars in cured leaves at each leaf position, in all nitrogen forms and nicotine mainly in plants treated with nitrate nitrogen. The changes in total nitrogen and ash content are considered as minimal. We conclude that the optimum chloride level in irrigation water is below 20 mg L⁻¹, whereas the level of 40 mg L⁻¹ in combination with nitrate nitrogen fertilizers can be considered as the upper threshold to avoid adverse effects on Virginia tobacco.     

Open pasture,silvopasture and sward herbage maturity effects on nutritive value and fermentation characteristics of cool‐season pasture

In Appalachian USA, silvopasture offers promise of increased farm productivity. A synchronized, temporal understanding of open pasture (OP) and silvopasture (SP) nutritive characteristics is essential for grazing system development. We examined pasture‐type nutritive‐value relationships when herbage was harvested based on morphological maturity rather than calendar date. Neutral detergent fibre and acid detergent fibre (ADF and NDF) content were greater in silvopasture, while organic matter (OM) was lower (P < 0·05). Digestibility of SP herbage dry matter (DM) and OM tended (P = 0·10) to be lower (418 vs. 471 and 437 vs. 491 g kg^?1 respectively). Neutral detergent fibre digestibility was greater (P < 0·05) for OP than SP forage (538 vs. 480 g kg^?1), and ADF tended to be greater (P = 0·10; 551 vs. 501). Open‐pasture forage fermentation effluent exhibited slightly higher microbial richness and Shannon diversity than SP. However, overall community composition of both bacteria and archaea did not differ between pasture types or sampling times. Pasture types show proximate analyses differences generally favourable to OP, although both have similar overall nutritive value. In addition, the SP sward exhibited a 4‐ to 6‐days delay in reaching equivalent maturity. Conversion of farm woodlots to SP would increase overall herbage production and improve pasture management flexibility.     

Evaluation of morphological and production characteristics and nutritive value of 47 lucerne cultivars/lines in temperate Australia

ABSTRACT

Forty-seven lucerne varieties/lines were examined to quantify their morphological, production characteristics, and nutritive values in southeastern Australia. The experiment was established in 2015 with a randomized complete block design and four replications. The morphological and production characteristics were measured from January to October 2017, and nutritive values were measured in February 2017. The results showed that the cultivars differed significantly (P < 0.01) in morphological, production characteristics, and nutritive values. Total herbage yield was highest for Haymaster 7 (14,186 kg/ha) and lowest for Qingshui (5927 kg/ha). Plant height was highest for Cropper 9.5 (31.4 cm) and lowest for Qingshui (14.5 cm). SF 714QL had the greatest branch number (44.7 branches/15 cm row segment). AV1001 had longest leaf (2.3 cm) and greatest leaf area (16.68 cm²/10 leaves) whereas Force 10 and SARDI 10 SERIES 2 had widest leaves (1.3 cm). AV1005 had the highest leaf-to-stem ratio (5.64). Crude protein (CP) content was highest for SARDI 10 SERIES 2 (15.1%) and lowest for SF 714QL (8.0%). AV12 was highest in crude fat (4.5%). Neutral detergent fiber (NDF) content was lowest in Stamina 5 (33.5%). Acid detergent fiber (ADF) content was lowest in Gannong 4 (29.3%). Relative feed value (RFV) was highest in Force 11 (193.0%). Calcium (Ca) content was highest for Titan 5 (1.8%). Phosphorous content was highest for AV1 and Gannong 6 (0.1%). Overall, Cropper 9.5, SARDI 10 SERIES 2, Haymaster 9, Titan 9, SF 714QL, Kaituna, Haymaster 7, AV1001, AV1002, and WL925HQ performed well based on their comprehensive scores.     

刈割高度对多花黑麦草新品种产量和品质的影响

为探讨不同刈割高度对多花黑麦草新品种饲草产量和品质的影响,以2个多花黑麦草新品种为对象,采用5个刈割高度分别测定2个品种的鲜、干草产量、粗蛋白、可溶性碳水化合物(WSC)、中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)和干物质体外可消化率(IVDMD)。结果表明:在65 cm时刈割,所获得的鲜、干草产量最高;随着刈割高度的增加,2个黑麦草品种的粗蛋白和可溶性碳水化合物含量呈抛物线趋势变化,在刈割高度为55 cm时达到最高值;中性和酸性洗涤纤维含量则随着刈割高度的增大逐渐增加;干物质体外消化率亦呈现抛物线的趋势,在刈割高度为65 cm时达到最高。2个品种的表现规律一致。     

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.     

Inclusion of alfalfa improves nutritive value and in vitro digestibility of various straw–grass mixed silages in Tibet

To enlarge the feed resources and enhance the utilization efficiency of straws as ruminant feed in Tibet, four kinds of local crop straws with tall fescue (Festuca arundinacea Schreb.) based on the ratio of 40/60 (fresh weight) were ensiled with four levels (0, 10%, 20% and 30% of fresh weight) of alfalfa (Medicago sativa L.), respectively. The laboratory silos (1L) were opened after 45 days of ensiling, and the fermentation characteristics, nutritive value and in vitro digestibility of the mixed silages were analysed. The silages including alfalfa had significantly (p < 0.05) or numerically (p > 0.05) higher lactic acid and crude protein contents, lactic acid bacteria counts, in vitro digestibility of dry matter, neutral detergent fibre (NDF) and acid detergent fibre (ADF), and lower NDF and ADF contents than controls. The results suggest that inclusion of alfalfa to mixtures of straws and tall fescue had favourable effects on fermentation quality and obviously improved the nutritive value and in vitro digestibility of mixed silages. This effect was most evident when the inclusion proportion of alfalfa was 30% in oat straw mixed silage.     

Effect of growth regulators on yield and fiber quality in ramie (Boemheria nivea (L.) Gaud.), China grass

The effects of two mixtures of four plant growth regulators (choline chloride, gibberellin (GA₃), benzyladenine (6-BA) and NaHSO₃) at 20:9:5:800 mg kg⁻¹ (H1) and 20:42:43:2350 mg kg⁻¹ (H3) (active ingredients), respectively, were investigated on yield and fiber quality in ramie (Boehmeria nivea (L.) Gaud.). The mixtures were sprayed over the canopy at two growth stages (10 and 20 days after the previous cut) of field-grown ramie. The treatments increased raw fiber yield by 13–18%, and improved fiber fineness by 57–349 m g⁻¹, increased number of leaves per plant, and also improved all yield components. Treatment H1 resulted in a denser distribution, smaller diameters and greater quantity of fiber cells in stem cross-section. Physiological responses included improving leaf water status, increasing net photosynthetic rate, and decreasing electrolyte exosmosis rate.     

Effects of varying nitrogen doses on yield,yield components and artemisinin content of Artemisia annua L.

Artemisia annua L. is an aromatic-antibacterial herb that destroys malarial parasites, lowers fevers and checks bleeding, and of which the secondary compound of interest is artemisinin. The objective of the present study was to determine yield, yield components and artemisinin content of A. annua L. grown under four nitrogen applications (0, 40, 80 and 120 kg ha⁻¹) in the Çukurova region of Turkey in 2004 and 2005. Field trials were conducted at Çukurova University, Agricultural Faculty Field Crops Department. In the study, plant height, number of branches, fresh herbage yield, dry herbage yield, fresh leaf yield, dry leaf yield, essential oil content and artemisinin content (by high performance liquid chromatography, HPLC) were examined. By analysis of variance, nitrogen doses had no any statistical effect on the traits investigated except for artemisinin content. Artemisinin content of the dried leaves were significantly affected by nitrogen applications, which varied from 6.32 to 27.50 mg 100 g⁻¹. Contents were from 120 and 80 kg ha⁻¹ nitrogen for the years of 2004 and 2005, respectively.     

Proximal sensing of the seasonal variability of pasture nutritive value using multispectral radiometry

The nutritive value of pasture is an important determinant of the performance of grazing livestock. Proximal sensing of in situ pasture is a potential technique for rapid prediction of nutritive value. In this study, multispectral radiometry was used to obtain pasture spectral reflectance during different seasons (autumn, spring and summer) in 2009–2010 from commercial farms throughout New Zealand. The analytical data set (n = 420) was analysed to develop season‐specific and combined models for predicting pasture nutritive‐value parameters. The predicted parameters included crude protein (CP), acid detergent fibre (ADF), neutral detergent fibre (NDF), ash, lignin, lipid, metabolizable energy (ME) and organic matter digestibility (OMD) using a partial least squares regression analysis. The calibration models were tested by internal and external validation. The results suggested that the global models can predict the pasture nutritive value parameters (CP, ADF, NDF, lignin, ME and OMD) with moderate accuracy (0·64 ≤ r² ≤ 0·70) while ash and lipid are poorly predicted (0·33 ≤ r² ≤ 0·40). However, the season‐specific models improved the prediction accuracy, in autumn (0·73 ≤ r² ≤ 0·83) for CP, ADF, NDF and lignin; in spring (0·61 ≤ r² ≤ 0·78) for CP and ash; in summer (0·77 ≤ r² ≤ 0·80) for CP and ash, indicating a seasonal impact on spectral response.     

Evaluating chemical indices of guayule rubber content: Guayulins A and B

Guayule (Parthenium argentatum Gray) is now a commercial crop for the production of high-quality, hypoallergenic natural rubber latex. Because guayule is relatively resistant to both insect and disease pests, its cultivation requires little chemical input. It has been postulated that guayule's chemical defense system is based on terpene derivatives such as guayulins A and B. The goals of this research were to: (1) describe the distribution of guayulins A and B throughout the plant, (2) determine whether guayulins can be used as a predictor of rubber content/yield (is guayulin content related to rubber content), and (3) determine whether the guayulin content/distribution has been changed through plant breeding.Two plants each of three different lines (11591, AZ-1, and AZ-3) and two ages (1 and 2 years old) were harvested at the soil line in the fall of 2002 and spring of 2003. Plants were separated into eight parts: brown leaves, green leaves, stem tips, stems less than 5 mm in diameter, stems between 5 and 10 mm, stems greater than 10 mm, green stems, and flower parts. Samples were analyzed for guayulins A and B and rubber content.Guayulins A and B and rubber were found in all plant parts, but were most prevalent in stems larger than 10 mm in diameter, and were significantly correlated with each other in these stems. Guayulin A was found in greater concentrations than guayulin B. There were no significant differences between plant ages for rubber, or guayulin content at the time of harvest, or guayulins for harvest season. Rubber percent was higher in spring, which agrees with numerous other investigations.Guayulin A in the stems is correlated with the total rubber in the plant, suggesting it as a potential selection tool. However, rubber in the same plant parts has a higher correlation with total plant rubber and remains a better and easier selection criterion than guayulin A.The extent to which guayulin contents differed between older, relatively unimproved lines and newer improved lines was evaluated. Variety 11591 had a higher concentration of guayulin A than guayulin B, so that the ratio of A to B was much higher than in the two improved lines (AZ-1 and AZ-3). It appears that the ratio of guayulin A to guayulin B has been changed in the two newer selections, but it is unclear whether this will affect pest resistance.     

Yield and nutritive value of timothy as affected by temperature,photoperiod and time of harvest

Scenarios of global climate change forecast an increase in air temperature of 3°C over the next 100 years in eastern Canada. Growth and nutritive value of cool‐season grasses are known to be affected by air temperature. It is also believed that grasses grown at high latitude have a greater nutritive value. The objectives of this study were to assess the effect of four combinations of day/night temperature and photoperiod (15 h–17/5°C; 15 h–22/10°C; 15 h–28/15°C; and 17 h‐17/5°C) on dry‐matter (DM) yield, in vitro true DM digestibility (IVTD), in vitro digestibility of neutral‐detergent fibre (NDF), and concentrations of NDF, acid‐detergent fibre (ADF), lignin, minerals and non‐structural carbohydrates (NSC) in timothy grown under controlled conditions. Furthermore, herbage was harvested in the morning and in the afternoon to assess the impact of the time of harvest. The dietary cation–anion difference [DCAD = (K⁺ + Na⁺) ? (Cl^? + 0·6 S^2?)] and the grass tetany index [GT index = K⁺/(Ca²⁺ + Mg²⁺)] were also calculated. Higher temperature regimes significantly decreased IVTD and digestibility of NDF but had a limited effect on concentrations of NDF, ADF and lignin. DM yield of herbage was less and the concentration of NSC was greater in timothy grown under a temperature regime of 28/15°C than the 17/5°C and 22/10°C regimes; this effect is mainly explained by a response to temperature stress. Values of DCAD and the GT index of herbage were also lower under the 28/15°C than the 17/5°C and 22/10°C regimes as a result of a decreased plant K concentration. Under the 17/5°C regime, an increase in 2 h of photoperiod resulted in increased DM yield, decreased concentrations of K, Ca, Mg, Cl and N, and an increased starch concentration; IVTD or digestibility of NDF were not affected, although lignin concentration was reduced. Harvesting timothy in the afternoon rather than in the morning resulted in higher NSC, mainly sucrose, concentrations, and decreased ADF and NDF concentrations. The forecasted increase in air temperature in eastern Canada over the next 100 years will result in lower yields and nutritive value of timothy.