62 research outputs found
Morphology and nutritive value of perennial ryegrass cultivars at different phenological stages
No full textEight perennial ryegrass cultivars (representing the variations in ploidy, heading date and water-soluble carbohydrates concentration) were investigated for morphology and nutritive value at three phenological stages: pre-heading vegetative, reproductive and post-flowering vegetative stages. Chemical compositions and digestibility of morphological components (lamina, pseudostem and reproductive stem) from each perennial ryegrass cultivar were analysed in a split-plot design. At the vegetative stages, perennial ryegrass cultivars differed significantly in the proportions of lamina and pseudostem. Tetraploid cultivars, Base and Bealey, always had the greatest lamina proportion (51.8% and 53.2% at the pre-heading and post-flowering vegetative stages respectively). At the reproductive stage, the emergence of seed heads diminished the differences in morphology among cultivars. Perennial ryegrass cultivars also had distinct nutritive value throughout three phenological stages. The high-sugar cultivar, AberMagic, had high WSC concentrations (276, 227 and 90 g/kg DM at the pre-heading vegetative, reproductive and post-flowering vegetative stages respectively); the intermediate-heading cultivars, Kamo and Commando, generally had a lower organic matter digestibility in dry matter than the late-heading cultivars at the pre-heading vegetative (70.7% vs. 74.4%) and reproductive stage (63.9% vs. 68.2%). However, although the morphological components were different in nutritive value consistently, the differences in morphology did not account for the variation in nutritive value among perennial ryegrass cultivars
Effect of grazing management on herbage protein concentration, milk production and nitrogen excretion of dairy cows in mid‐lactation
No full textThe objective of this experiment was to use diurnal and temporal changes in herbage composition to create two pasture diets with contrasting ratios of water-soluble carbohydrate (WSC) and crude protein (CP) and compare milk production and nitrogen-use efficiency (NUE) of dairy cows. A grazing experiment using thirty-six mid-lactation Friesian x Jersey cows was conducted in late spring in Canterbury, New Zealand. Cows were offered mixed perennial ryegrass and white clover pastures either in the morning after a short 19-day regrowth interval (SR AM) or in the afternoon after a long 35-day regrowth interval (LR PM). Pasture treatments resulted in lower pasture mass and greater herbage CP concentration (187 vs. 171gkg-1 DM) in the SR AM compared with the LR PM but did not affect WSC (169gkg-1 DM) or the ratio of WSC/CP (1·0gg-1). Cows had similar apparent DM (17·5kg DM cow-1d-1) and N (501gNcow-1d-1) intake for both treatments. Compared with SR AM cows, LR PM cows had lower milk (18·5 vs. 21·2kgcow-1d-1), milk protein (0·69 vs. 0·81kg cow-1d-1) and milk solids (1·72 and 1·89kgcow-1d-1) yield. Urinary N concentration was increased in SR AM, but estimated N excretion and NUE for milk were similar for both treatments. Further studies are required to determine the effect of feeding times on diurnal variation in urine volume and N concentration under grazing to predict urination events with highest leaching risk
Grazing preference of Merino sheep for naturalized annual clover species relative to commonly sown clover species
No full textSelective grazing of white clover (Trifolium repens) over grass species in temperate pastures results in reduced clover abundance and availability over time. Within sheep- and cattle-grazed dryland (<800 mm annual rainfall) hill and high country areas of New Zealand, naturalized unsown annual clover species show greater persistence and abundance over sown clovers. With a view to understanding legume abundance in these areas, Merino sheep grazing preference was investigated for pure swards of naturalized species Trifolium dubium, T. glomeratum, T. arvense and T. striatum and commonly sown species T. repens and T. subterraneum. The Chesson–Manly preference index was used to explore the hypothesis that grazing preference differs between these species and changes as plants mature. Herbage offtake was quantified at vegetative (mid–late spring; November) and reproductive (early summer; December) stages of plant maturity. Significant preference distinctions between species (P < 0·05) occurred in December, with relative preference ranging from 0·248 for T. repens to 0·065 for T. dubium. Reduced relative preference for naturalized species was related to decreasing nutritive value from spring to summer, reflecting increased stem and flower sward content. Relative preference was negatively related to increasing acid detergent fibre and neutral detergent fibre and positively related to greater crude protein and dry-matter digestibility. Naturalized annual clover species of lower grazing preference at reproductive maturity will benefit pasture sustainability via herbage and seed production and associated nitrogen-fixation inputs
Measuring excreta patch distribution in grazed pasture through low‐cost image analysis
No full textNutrient losses from grazed pasture are an important non-point source of water pollution. The distribution of animal urine patches on pasture is an important factor in determining nitrate losses and influencing pasture growth, nutritive value and pasture acceptability to livestock, as a high amount of nitrogen (N) is deposited onto a small area of soil under a urine patch. Urine distribution may be recorded during or post-grazing. Measurements during grazing have been automated, but post-grazing measurement currently relies on manual observations that are time consuming and cannot be subsequently verified. To automate post-grazing measurements, aerial photographs were taken of grazed pasture approximately 14 d post-grazing using a standard digital camera. Pasture response areas were successfully identified by analysing the hue of the images using readily available software, yielding comparable results to manual counts. The majority of dung patches did not produce observable pasture responses, with only 14% of the visible response areas being associated with dung, so although this method cannot distinguish between urine and dung response areas, it is primarily influenced by urine. Provided photographs are taken in full sunlight with a high-quality camera, excreta patch numbers, areas and spatial distribution can be measured with a high degree of precision. Furthermore, the method is relatively inexpensive and applicable to a wide range of situations. A permanent photographic record of the pasture is also established, which allows verification of the analysis in future
Effects of post-grazing herbage height and concentrate feeding on milk production and major milk fatty acids of dairy cows in mid-lactation
No full textAbstract
Milk fatty acids (FA) were compared in mid‐lactation dairy cows in four feeding systems combining grazing management and supplementation. The four treatments were factorial combinations of compressed herbage grazed to 3·7 or 4·6 cm post‐grazing height, with or without concentrate feeding (3·6 kg cow−1 d−1). Milk yield and composition were measured for four groups of eight Friesian × Jersey dairy cows over 3 weeks in mid‐lactation for cows that had grazed treatments for 64 d from early spring. Milk yield was higher in cows fed concentrate plus herbage (23·9 kg d−1 cow−1) than cows fed herbage only (20·3 kg d−1 cow−1). Milk fat percentage was higher in cows fed herbage only (5·5%) than that fed herbage plus concentrate (5·1%). Milk protein percentage was higher in cows fed herbage plus concentrate (4·0%) than that fed herbage only (3·7%). The concentrations of conjugated linoleic acids c9, t11, C18:0, C18:1 t11 and C18:2 t9, c12 FA were lower where concentrate was fed. The concentrations of C18:1 t10, C18:1 t5, t8 and C18:2 c9, c12 FA were higher where concentrate was fed. The concentrations of C18:1 c6, C18:1 c9, C18:1 t9 and C18:3 c6,9,15 were unaffected by concentrate feeding. Post‐grazing herbage height had no significant effect on milk yield or concentration of milk FA. Provided dairy cows are harvesting leafy material of similar nutrient and FA concentration, post‐grazing herbage height does not appear to alter milk FA and the supply of high energy concentrates is more influential on milk FA profiles
Milk yield and nitrogen excretion of dairy cows grazing binary and multispecies pastures
No full textThree grazing experiments were carried out in late spring (early lactation), summer (mid-lactation) and autumn (late lactation) to compare the effects of perennial ryegrass cultivar or grass species, sown in binary or multispecies mixtures, on milk yield and nitrogen excretion of dairy cows. Replicated groups of multiparous Holstein Friesian × Jersey cows were offered either a control or high-sugar perennial ryegrass (Lolium perenne) or tall fescue (Festuca arundinacea) base grass in a binary mixture with white clover (Trifolium repens) or in a multispecies mixture with additional legumes, bromegrass (Bromus willdenowii) and forbs. During each 9-day experiment, botanical composition, milk production and faecal and urine composition were measured. Milk solid (MS) yield for the control ryegrass, high-sugar ryegrass and tall fescue grass types averaged, respectively, 1.53, 1.64 and 1.70 kg MS cow⁻¹ day⁻¹ for a binary mixture sward, compared with 1.65, 1.54 and 1.53 kg MS cow⁻¹ day⁻¹ for a multispecies sward. Legume content influenced milk production more than the number of species present in a mixture. There was lower urine N concentration from a multispecies sward compared with a binary mixture. Urine N concentration of cows grazing the control ryegrass, high-sugar ryegrass and tall fescue grass types averaged, respectively, 4.6, 5.3 and 6.8 g N L⁻¹ for a binary mixture, compared with 4.1, 3.9 and 3.9 g N L⁻¹ for a multispecies mixture. Feeding dairy cows on multispecies swards containing forbs presents an opportunity to reduce N losses without compromising milk yield
Different types of rectification at electrical synapses made by a single crayfish neurone investigated experimentally and by computer simulation
No full textThe rectification properties of electrical synapses made by the segmental giant (SG) neurone of crayfish (Pacifastacus leniusculus) were investigated. The SG acts as an interneurone, transmitting information from the giant command fibres (GFs) to the abdominal fast flexor (FF) motoneurones. The GF-SG (input) synapses are inwardly-rectifying electrical synapses, while the SG-FF (output) synapses are outwardly rectifying electrical synapses. This implies that a single neurone can make gap junction hemichannels with different rectification properties. The coupling coefficient of these synapses is dependent upon transjunctional potential. There is a standing gradient in resting potential between the GFs, SG and FFs, with the GFs the most hyperpolarized, and the FFs the most depolarized. The gradient thus biases each synapse into the low-conductance state under resting conditions. There is functional double rectification between the bilateral pairs of SGs within a single segment, such that depolarizing membrane potential changes of either SG pass to the other SG with less attenuation than do hyperpolarizing potential changes. Computer simulation suggests that this may result from coupling through the intermediary FF neurones.</p
Reducing nitrogen leaching losses in grazed dairy systems using an Italian ryegrass‐plantain‐white clover forage mix
No full textIn grazed agricultural systems, animal urine patches are the major source of nitrogen (N) leaching losses and can cause a decline in water quality. Urine-N rates often exceed plant requirements, and there is a need for mitigation options to reduce the impact of agriculture on the environment. One approach is to use alternative forages to reduce urine-N loading rates, or to increase N uptake. This study used lysimeters to determine the N leaching losses, dry matter yields and N uptake following ruminant urine application to an Italian ryegrass-plantain-white clover forage mix (IRPWC, Lolium multiflorum Lam.-Plantago lanceolata L.-Trifolium repens L.) or perennial ryegrass-white clover (PRWC, Lolium perenne L.-T. repens L.). Three urine treatments were applied: Control (no urine), Urine Actual (urine from cows grazing each of the forages: 508, and 664 kg N/ha, for IRPWC and PRWC, respectively) and Urine 700 (700 kg N/ha). Compared with PRWC (113 kg N/ha), N leaching losses were 88.9% lower from IRPWC-Urine Actual (12.5 kg N/ha) and 45.5% lower from IRPWC-Urine 700 (61.8 kg N/ha). These reductions were attributed partly to the IRPWC having higher cool season activity and ability to take up N during the cool period, and partly to the lower concentration of urine-N, compared with PRWC. IRPWC is a promising alternative forage for future farm systems with the ability to reduce urine-N excretion from grazing animals and cause large reductions in N leaching losses while producing the same herbage dry matter yields as PRWC
recovery during winter
No full text© 2015 John Wiley & Sons Ltd. Nitrate (NO₃⁻) leaching is an environmental and health concern. In grazed pasture systems, NO₃⁻ leaching primarily occurs beneath animal urine patch areas due to high nitrogen (N) loading and the inability of pasture plants to capture all of this N. This study investigated the relative importance of plant growth and root architecture to recover soil N. Herbage N recovery, dry matter (DM) yield and root architecture, following injections of ¹⁵N-enriched urea at different soil depths (5, 25 and 45 cm), were measured for Italian ryegrass (Lolium multiflorum Lam.) and tall fescue (Festuca arundinacea Schreb.) grown in soil monolith lysimeters (18 cm diameter × 70 cm depth) under simulated South Island, New Zealand winter temperature and light levels. Total herbage N uptake and DM yield were on average 24 and 48% greater in L. multiflorum than F. arundinacea respectively. Root length density (cm cm⁻³ soil) in the 5- to 25-cm-depth horizon was similar between species. In the 25- to 45-cm-depth horizon, F. arundinacea roots were found at higher densities than L. multiflorum. In the 45- to 65-cm-depth horizon, root length density was fourfold to ninefold higher for F. arundinacea than L. multiflorum, but N uptake efficiency was greater in L. multiflorum (0·48 mg ¹⁵N m⁻¹ root) than F. arundinacea (0·09 mg ¹⁵N m⁻¹ root). The results suggest that deep F. arundinacea roots are relatively inactive during the winter period and confirm that plant growth is more important than root architecture (e.g. deep roots) to recover soil N and ultimately reduce nitrate leaching losses
The effect of kale cultivar and sowing date on dry matter intake, crop utilization, liveweight gain and body condition score gain of pregnant, non-lactating dry dairy cows in winter in New Zealand
No full textAn outdoor grazing study on kale was conducted with pregnant, nonlactating (dry) dairy cows over a 42‐day winter grazing period commencing 9 June 2008. Kale treatments consisted of two kale cultivars varying in leaf:stem proportion (“Regal,” a leafy variety and “Caledonian,” a stemmy variety) and two sowing dates (8 November and 15 December). Measurements were made for dry‐matter (DM) utilization, apparent DM intake, liveweight gain and changes in body condition score (BCS) for a total of 120 cows allocated to three replicate groups of the four factorial treatments. Cows were offered a daily allowance of 10 kg DM/cow of kale and 2.2 kg DM/cow of straw. Pregrazing DM yield was higher for kale sown in November (16,517 kg DM/ha) than December (13,867 kg DM/ha), but was unaffected by cultivar (average 15,192 kg DM/ha). “Regal” kale had a higher percentage of leaf compared with “Caledonian” (33.6% vs. 25.6%), lower content of NDF (32.4% vs. 34.1%), but similar metabolizable energy content (12.1 MJ/kg DM for both) in the whole plant. Despite the differences in pregrazing DM yield and forage quality among treatments, no differences were found in DM utilization (between 88.5% and 90.2%), apparent DM intake (between 9.4 and 9.6 kg DM/cow.day), liveweight gain (between 0.53 and 0.67 kg/cow.day) and BCS gain (between 0.43 and 0.46 unit/cow over 42 days). Manipulation of kale yield and quality through choice of cultivar and sowing date had no effect on the performance of pregnant, nonlactating dairy cows
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