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This study aimed to identify suitable predictors of nitrogen (N) use efficiency (NUE; milk N/N intake) for cows that differed in breeds and were fed with ryegrass pasture, using existing data from the scientific literature. Data from 16 studies were used to develop models based on the relationships between NUE and dietary and animal-based factors. Data from a further 10 studies were used for model validation. Milk urea N (MUN) and dietary water-soluble carbohydrate-tocrudeprotein ratio (WSC/CP) were the best and most practical animal- and diet-based proxies to predict NUE. The results indicate that it might be necessary to adopt separate models for different breeds when using WSC/CP to predict NUE but not when using MUN. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the relationship between plasma amino acid (AA) concentration and urinary nitrogen (N) concentration of dairy heifers offered cut plantain or perennial ryegrass-white clover pasture indoors. Twelve Jersey-Friesian heifers aged 9–10 months were equally assigned to two dietary treatments (plantain vs. perennial ryegrass-white clover pasture) in a completely randomised design. Urinary N concentration was lower in plantain fed heifers (1.4 g/kg) than in perennial ryegrass-white clover pasture fed heifers (3.4 g/kg). Feeding cut plantain or perennial ryegrass-white clover pasture did not have an effect on either plasma essential AA, non-essential AA or total AA. There was no association found between plasma AA concentration and urinary N concentration in the present study. Therefore, the urinary N concentration reduction in plantain fed heifers compared with perennial ryegrass-white clover pasture cannot be attributed by the differences in plasma AA. [ABSTRACT FROM AUTHOR]

The objective of this study was to quantify amino acid (AA) profiles in plasma collected from dairy heifers grazing swards containing ryegrass/clover, chicory and plantain in autumn and spring. The study comprised a 28-day autumn trial and a 21-day spring trial using 56 Friesian x Jersey heifers. Total AA concentrations ranged from 2849 to 3165 μM in autumn and from 3195 to 3454 μM in spring, with no treatment effect. Season affected essential AA (EAA) and total AA concentrations. Total plasma AA concentrations were lower in autumn (2965 μM) than in spring (3303 μM). Based on these results, feeding dairy heifer's either pure chicory, binary mixture or pure plantain does not affect EAA and total AA of Friesian x Jersey heifers. Further, no relationship was established between AA and weight gain of heifers in this study. [ABSTRACT FROM AUTHOR]

Eight 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. [ABSTRACT FROM AUTHOR]

The aim of this research was to assess the potential of using perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) forages containing plantain (Plantago lanceolata L.) (PRGWC + Plantain) to mitigate nitrate (NO3−) leaching in grazed grassland. Lysimeter studies were carried out to determine NO3− leaching losses from the PRGWC + Plantain forage, compared with the standard perennial ryegrass and white clover forage (PRGWC) under three different irrigation conditions (flood, rotorainer and pivot). Fresh dairy cow urine (700 kg N ha−1) was applied to these lysimeters in early summer (December) and late summer (February). Nitrogen (N) dynamics and the abundance of ammonia oxidising bacteria (AOB) and archaea (AOA) were also determined in companion mini-plots alongside the lysimeters. Nitrate leaching losses from the PRGWC + Plantain forage were 82% lower than those from the PRGWC forage when urine was applied in December and 74% less when urine was applied in February (P < .05). This was possibly due to the release of biological nitrification inhibitors by plantain which slowed down the nitrification process and this, combined with a lower drainage volume, was largely responsible for the lower NO3− leaching losses in the PRGWC + Plantain forages. The three different irrigation schemes did not significantly affect NO3− leaching losses under the two forage types. These results demonstrate the potential of using PRGWC + Plantain forages as an effective mitigation option for NO3− leaching in grazed grasslands. [ABSTRACT FROM AUTHOR]

Pasture mitigation strategies are needed to reduce the negative effects of nitrate (NO3−) leaching from intensive pastoral livestock production systems. We explored the capability of pasture grasses with different cool season (winter-early spring) growth rates to reduce NO3− leaching and increase N uptake. Following a single urine application of 700 kg N ha−1, NO3− leaching loss and N uptake by Italian ryegrass and four perennial ryegrass cultivars of varying seasonal growth (heading dates from -7 to +20 days), either undersown with/without Italian ryegrass, were quantified in a 12 month lysimeter study. Italian ryegrass cv. Tabu had lower NO3−-N leaching loss and drainage, and greater N uptake and DM yield than perennial ryegrass varieties. Italian ryegrass total N leaching loss (143 kg N ha−1 yr−1) was 46-33% less (P < .05) than early and mid-season maturing Tyson, Arrow and AberDart perennial ryegrass. Italian ryegrass total N uptake (463 kg N ha−1) was 1.2-1.4 times greater than all other grass sward types. Overall, perennial ryegrass pure swards had similar N uptake and N leaching. Late-season maturing One 50 perennial ryegrass showed significantly reduced (P < .05) total N leaching loss. Undersowing Italian ryegrass into established perennial ryegrass swards resulted in lower NO3− leaching and greater N uptake than non-undersown perennial ryegrass swards, though not significant. Results confirm Italian ryegrass is a useful pasture grass option for reducing annual N leaching loss. Cool season perennial ryegrass varieties appear not to influence soil N uptake and leaching loss. [ABSTRACT FROM AUTHOR]

Irrigated, diverse pastures were managed under normal (grazed to 3.5 cm) or lax (grazed to 5 cm allowing ryegrass seed head development) grazing intensity, with or without mowing (to 3.5 cm), in spring. On the subsequent grazing rotation in summer, an experiment was conducted to investigate the carry-over effects of previous management on herbage regrowth and milk production. Nine groups of three Friesian × Jersey dairy cows each were randomly allocated to three replicates of three treatments: normal grazing (Norm); previously lax managed pastures (Lax); previously lax managed pastures that were pre-graze mown (Mow). Herbage in Mow treatments had a higher ME (p < 0.05) than Lax and Norm (11.7, 11.3 and 11.4 MJ ME/kg DM, respectively). There was no difference in dry matter intake (18 ± 0.30 kg DM/cow/d) or MS production (1.85 ± 0.02 kg MS/cow/d) among treatments. Results of this study indicated that milk production was not altered by grazing management. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess live weight gain, animal behaviour and N excretion in the urine of dairy heifers fed herbs during autumn and spring. Sixty heifers were allocated into five dietary treatments: 100% ryegrass-white clove pasture (100RG/WC); 50% RG/WC + 50% chicory (50CH); 75% RG/WC + 25% chicory (25CH); 75% RG/WC + 25% plantain (25PL); and 50% RG/WC + 50% plantain (50PL). The 100RG/WC had the highest (5.0 times/6 h) and lowest (2.5 times/6 h) urination frequency compared with other treatments in autumn (averaged 3.5 times/6 h) and spring (averaged 4.5 times/6 h), respectively. The heifer LWG in spring was higher in 25CH (1.36 kg/day) than other treatments (averaged 1.10 kg/day). Urinary N concentration was 0.18% and 0.23% in autumn and spring, respectively, across treatments, with no difference between treatments. The study demonstrated inconsistent results of use of chicory and plantain as a mitigation tool to reduce the environmental impact of heifer rearing systems in autumn and spring. [ABSTRACT FROM AUTHOR]

This study investigated the effects of three forage treatments [herbal plantain (PL), ryegrass-white clover pasture (RW) and root crop fodder beet (FB)] on ex-vivo rumen fluid fermentations. Quantitative real-time Polymerase Chain Reaction (qPCR) and PCR-single-stranded conformation polymorphism (PCR-SSCP) analyses were undertaken for aliquots collected from the fermentations. The FB treatment had the highest volatile fatty acid (VFA) and lowest pH compared with other treatments. The RW culture that had a higher fibre content, had higher Fibrobacter succinogenes(F. succinogenes) and anaerobic fungi levels when compared with the FB and PL. Protozoans were however the most abundant microorganisms in the FB cultures, and they had the highest water-soluble carbohydrate (WSC) content. The abundance of F. succinogenes increased in the RW fermentation up to 12 h, and the abundance of anaerobic fungi increased in the RW fermentation up to 24 h. In all the treatments, no effect was found on the overall abundance of bacteria. The findings confirmed that changes in rumen microbial community and fermentation products are partly related to the WSC and fibre content of two novel forages (i.e. PL and FB) increasingly used in animal production. [ABSTRACT FROM AUTHOR]

Herbage accumulation (HA) data from four sites were combined to (1) address the hypothesis that adjustments to the New Zealand Forage Value Index to account for grass-clover interactions are not required and (2) explore the main effects of clover and nitrogen (N) fertiliser treatments on pasture productivity. In summer and autumn, pastures based on mid-season heading ryegrass cultivars consistently supported a greater clover content than pastures based on late heading cultivars. However, the clover ×  cultivar interaction was significant in only 2 of 17 HA data sets available for analysis. Thus, the hypothesis is supported. Compared with ryegrass monocultures, mixtures yielded an additional 2.4 (in the Low-N treatment) and 1.2 (High-N treatment) t DM/ha/year. Apparent N transfer from clover to grass was 79 (Low N) and 27 (High N) kg N/ha/year, derived from estimated N fixation efficiencies of 66 (Low N) and 50 (High N) kg N/t clover DM grown. [ABSTRACT FROM AUTHOR]

The development of economic indexing systems for ranking cultivars of forage species requires new knowledge of factors that may influence the scaling of agronomic data collected in controlled, small-plot evaluation trials to whole farm systems. In the case of perennial ryegrass indexing, one such knowledge gap is the effect of growing clover with ryegrass on the relative rankings of different ryegrass cultivars. The objective of the investigation reported in this series was to test whether the relative yield rankings of perennial ryegrass (Lolium perenne L.) cultivars representing the range in phenotypes now available to New Zealand farmers as a result of recent breeding differed when those cultivars were grown in monocultures (as per standard protocols for cultivar yield trialling systems such as the National Forage Variety Trials) versus mixtures of grass and clover. This paper presents the rationale for the investigation by reviewing developments in perennial ryegrass breeding and evaluation in the context of grass-clover relationships in grazed pasture systems. The papers that follow report results from a multi-year, multi-site investigation comparing the yield, nutritive value and other productivity-related variables of eight perennial ryegrass cultivars grown with or without white clover (monoculture versus mixture respectively) at two levels of nitrogen fertiliser. Key considerations in the design of the experiment on which the investigation was based are discussed. [ABSTRACT FROM AUTHOR]

This paper describes how the core treatments in the national experimental design (all combinations of with/without clover and high/low nitrogen (N)) were implemented at an irrigated Canterbury site and monitored for three years. There was a consistent N × clover interaction, caused mainly by substantially lower yields in the Low N without clover treatment compared with all other treatments. At the phenotypic contrast level, the main effect of perennial ryegrass heading date on white clover content was significant in four of the nine seasonal data sets available: on these occasions, mixtures based on mid-season heading cultivars had higher clover content than later season-heading cultivars. However, this difference was not sufficient to cause any clover × cultivar interactions in herbage accumulation. Hence, the hypothesis that relative yield rankings of ryegrass cultivars do not differ when ryegrass is grown in monoculture or in mixture with white clover is supported. [ABSTRACT FROM AUTHOR]

Simple Summary: Short-term studies have suggested plantain and Italian ryegrass as alternative forages to ryegrass–white clover sward to reduce the environmental footprint of grazing dairy farms. However, the adoption of such forages by farmers will likely be limited until more certainty around its effect on farm productivity and profitability. The objective of this study was to provide multiple-year and farm-scale evidence to farmers with respect to the effects of integrating plantain and Italian ryegrass into the ryegrass and white clover-based dairy system on farm productivity, profitability, and nitrate leaching losses. Under similar farming system input, the plantain plus Italian ryegrass-based dairy system could be used by dairy farmers to mitigate the environmental footprint while maintaining farm productivity and profitability. A two-year farm system study was conducted at Canterbury, New Zealand to evaluate the effects on farm productivity, profitability, and nitrogen (N) losses of integrating plantain (Plantago lanceolate L.) and Italian ryegrass (Lolium multiflorum Lam.) into a ryegrass and white clover (RGWC)-based dairy system. Three farm systems were compared: (1) a lower input RGWC-based system (LIRG) with stocking rate of 3.5 cow/ha, annual N fertiliser rate of 150 kg/ha, and imported feed level of <1.2 t DM/cow/year; (2) a lower input ryegrass + plantain-based system (LIRG + PL) with a stocking rate of 3.5 cow/ha, annual N fertiliser rate of 150 kg/ha, and imported feed level of <1.2 t DM/cow/year; and (3) a higher input RGWC-based system (HIRG) with a stocking rate of 5.0 cow/ha, annual N fertiliser rate of 300 kg/ha, and imported feed level of >1.2 t DM/cow/year. Cows in the LIRG + PL system grazed a diverse mix of Italian ryegrass, perennial ryegrass, white clover, and plantain (60% of farmlet area), and a mixed sward of plantain–white clover (40% of farmlet area). The average annual herbage harvested was similar between LIRG + PL and LIRG (11.7 t DM/ha), but greater in HIRG (12.7 t DM/ha) with the increased N fertiliser rate. During the calving to dry-off period, the average imported supplement feed per ha was higher in HIRG (8.0 t DM) compared with LIRG (3.2 t DM) and LIRG + PL (3.7 t DM). Average milk solid production (MS; fat + protein) was similar in LIRG + PL (1640 kg/ha) and LIRG (1622 kg/ha), but greater in HIRG (2130 kg/ha). Estimated profitability (NZD/ha) at milk price of NZD 6.5/kg MS was 10% greater for HIRG than LIRG + PL and LIRG, and similar (<1.5% numerical difference) between LIRG + PL and LIRG. The average estimated annual N leaching loss from the LIRG and LIRG + PL was 31% and 56% less than the loss from the HIRG. These large reductions in N leaching loss were achieved without a large decrease in profitability (i.e., LIRG and LIRG + PL compared to HIRG). In addition, the estimated reduction in N losses from the LIRG + PL system compared to LIRG suggests that an Italian ryegrass + plantain-based dairy system is a viable strategy to reduce the environmental footprint while maintaining farm profitability. However, the environmental benefits of plantain and Italian ryegrass estimated in this study require further confirmation through direct measurements at full farm level. [ABSTRACT FROM AUTHOR]

Results of studies designed to determine whether or not differences measured among perennial ryegrass cultivars in small-plot studies translate into differences in milk production and profit in dairy whole-system studies were reviewed. Only three experiments were identified that met the criteria for fully self-contained systems repeated over multiple years required to account for annual feed supply-demand balance, its interaction with animal intake and production, and the influence of inter-annual climate variability on these processes. Collectively, these studies provide evidence of improvement in animal production, associated with genetic gains from ryegrass breeding, albeit through shifts in factors such as heading date (as it affects herbage quality and grazing efficiency) and host plant by endophyte interactions, rather than through gains in dry-matter yield. The latter remains unresolved, despite substantial evidence for gains from small-plot trials of dry-matter yield increases in the order of 0.5% per annum. These studies also highlighted the number of factors that have to be taken into account in the design and conduct of such studies, including gaining clarity about the size of the differences that can be expected and ensuring sufficient statistical power. Implementing objective management rules that allow cultivars to express their potential and capture differences through the grazing animal will ensure sufficient measurement intensity to enable differences (if observed) in milk production and profit to be explained. This should guard against confounding factors such as the differential effects of insect pests on plant performance, and consequent changes in pasture botanical composition mediated by ryegrass endophyte strains. Despite these difficulties, more experiments of this type are required to quantify and, ultimately, increase the value being delivered by ryegrass breeding to pasture-based dairy production systems in temperate regions. Therefore, there is a need for whole-system studies to be undertaken to provide valuable new information and give farmers the confidence to invest in the use of new cultivars. [ABSTRACT FROM AUTHOR]