Complementary Forage Research Articles

Polyparasitic associations in deer from the Republic of Moldova

The analysis of parasitic fauna in deer from the natural reservations of the Republic of Moldova revealed a high level of parasite infestation, in which associations of two or more parasite species predominate. Out of total number of 14 parasite species identified in cervids, only three species (Eimeria austriaca, E. ponderosa, E. capreoli) are characteristic for them, while the other 11 parasite species identified (D. lanceolatum, F. hepatica, P. cervi, S. papillosus, C. punctata, O. ostertagi, T. vitulorum, T. axei, M. benedeni, E. asymmetrica, E. bovis) are common not only to cervids but also to the domesticated ruminants. The level of parasitic infestation of deer from the Natural Reservation „Plaiul Fagului” is characterized by the mixture of parasitic forms, with 36,1% higher incidence in noble deer, 30,3% higher in the sika deer and 13,0% higher in roe deer compared to those from the Natural Reservation „Codrii”, due to the specific biotope and the complementary foraging of the deer in difficult seasonal periods.

Temperature fluctuation alters optimal predator community composition for anticipated biological control

Alongside pesticides and specialist predators, natural communities of generalist beetle and spider predators play an important role in suppressing agricultural pests. However, the predation pressure of natural communities can be unpredictable. Overall predation pressure is influenced by a dense network of potential intraguild interactions, which are further shaped by species traits and environmental factors. Understanding how these different influences combine to impact pest control is especially important in the context of changing global temperatures. Recent empirical studies have demonstrated that the foraging behavior of arthropod predators is influenced by an interaction between temperature and predator body size. To explore the consequences of these findings for intraguild interactions and pest control, we expand a previously published model describing interactions between arthropod predators and a pest population. The model assumed that interaction strengths are influenced by body size and habitat preference. In our updated model, we incorporate the effect of temperature on predator foraging activity. We parameterize the model to match empirically observed predator community composition in 10 agricultural fields and use simulations to demonstrate how temperature-dependent behaviors change the expected efficiency of the natural predator community. Then, we use an optimization approach to identify the most efficient composition of natural predators for pest control. We then evaluate whether the most efficient predator compositions would change with increasing average daily temperature and its variability, as is expected under future temperature change. We find that optimal communities often include predators with complementary foraging activity and that in 2 fields, the optimal community changes drastically under future temperatures. We also note that at some temperatures, foraging activity reduces the negative effects of intraguild interference on pest consumption. This work allows us to assess the effect of climate change on the efficiency of natural predator communities to control pest populations and provide guidance for farmers to design pest management strategies tailored to different climate scenarios.

A combination of rules govern fruit trait preference by frugivorous bat and bird species: nutrients, defence and size

Several hypotheses explain how sensory, anatomical and physiological constraints drive fruit preference in frugivores. Optimal diet theory (ODT) states that frugivores make decisions based on the energy contained in food. In contrast, geometry of nutrition (GN) states that animals balance their macronutrient intake instead, opting for rough energy. The defence trade-off hypothesis (DTH) assumes a negative relationship between secondary compounds and fruit preference. Finally, the size-matching hypothesis (SMH) states that frugivores are more attracted to fruits that are easier to handle and consume. We tested these four hypotheses by offering paired fruit species to three fruit-eating animal species in captivity that either chew fruit in the beak or mouth (‘masher’: 1 bird species, 1 bat species) or swallow whole fruits (‘gulper’: 1 bird species), from which we built a ranking of fruit preference. We then explored the importance of 13 fruit traits in explaining fruit preference. The masher bird was the only species whose fruit preference pattern corresponded with GN. Fruit preference of the masher and gulper bird species supported DTH and SMH, while fruit preference by the bat species was not related to any analysed trait. More than one single rule governs fruit preference in different frugivore species. Fruit preferences of functionally different frugivore species are affected by particular fruit traits, which they either select or avoid. The search for specific macronutrients, while avoiding toxicity in fruits matching the anatomical limitations of frugivores, could lead to complementary foraging choices. Variability between seed disperser species in their search for easily manageable fruits allows achieving a complementary fruit diet, with preferred and avoided traits. It can be an important driver of fruit trait diversity in fleshy-fruited plant assemblages. • Fruit macronutrient content and secondary compounds influence frugivore preferences. • Fruit size also influences frugivores' ability to interact with fruits. • Frugivore species differ in their search strategies to obtain complementary diets. • Preferred and avoided traits can drive diversity of fleshy-fruited plant assemblages.

Estimation of the inter-annual marginal value of additional feed and its replacement cost for beef cattle systems in the Flooding Pampas of Argentina

The effects of climate variability are projected to increase in the future threatening the expected outcomes of grazing-based animal production, feed use efficiency, and development of sustainable farming livelihoods. The identification of profitable farm management strategies to overcome critical inter-annual feed supply deficits is a worldwide management problem for grazing-based livestock systems and such information is essential for designing resilient feed-bases against climate variability. Increasingly, beef breeding herd (cow-calf) farmers in the Flooding Pampas region of Argentina have added backgrounding enterprises to deal with inter-annual system risks, but the impact of adopting such livestock managements under different forage growth patterns has not been widely investigated in the region. The aims of our study were to explore the marginal value of feed (MVF; it quantifies the economic value of an extra kg DM or MJ of metabolizable energy) in a representative beef cattle farm from the Flooding Pampas region. By combining this variable with the replacement cost method, different feed alternatives available for farmers to increase feed-on-offer were compared, under climate and price variability. The feed scenarios were baseline [unchanged herbage mass accumulation (HMA)] or with an extra 10% of the annual HMA in different seasons (summer, autumn, winter, spring or all year around), within a full range of beef cattle systems (stocking rates and steer/cow rates with different target market liveweights for steers and heifers). These scenarios were tested by integrating forage, livestock and economic models in series. Drier years reached higher MVF, and cumulative curves showed greater absolute values and probabilities of obtaining a higher MVF in winter or spring, and lowest in summer. The backgrounding management alternatives provide opportunities to increase the MVF (by up to 20% >0.09 US$ per extra kg DM added in winter at 0.55 cows ha−1 with a 0.4 steer/cow rate), enabling the purchase of high-quality forages (>0.07 US$ kg−1 DM). However, high stocking rate and grazing intensity (>0.6) may reduce the inter-annual farm performance (LW sales ha−1 and profitability). The framework developed in this study has provided new insights for diversifying into the use of complementary forage sources in the farm feed-base to improve farm resilience against climate and price variability in the Flooding Pampas of Argentina.

Designing Diverse Agricultural Pastures for Improving Ruminant Production Systems

Pasture-based production systems represent a significant sustainable supplier of animal source foods worldwide. For such systems, mounting evidence highlights the importance of plant diversity on the proper functioning of soils, plants and animals. A diversity of forages and biochemical-primary and secondary compounds- at appropriate doses and sequences of ingestion, may lead to benefits to the animal and their environment that are greater than grazing monocultures and the isolated effects of single chemicals. Here we review the importance of plant and phytochemical diversity on animal nutrition, welfare, health, and environmental impact while exploring some novel ideas about pasture design and management based on the biochemical complexity of traditional and non-traditional forage sources. Such effort will require an integration and synthesis on the morphology, ecophysiology and biochemistry of traditional and non-traditional forage species, as well as on the foraging behavior of livestock grazing diverse pasturelands. Thus, the challenge ahead entails selecting the “right” species combination, spatial aggregation, distribution and management of the forage resource such that productivity and stability of plant communities and ecological services provided by grazing are enhanced. We conclude that there is strong experimental support for replacing simple traditional agricultural pastures of reduced phytochemical diversity with multiple arrays of complementary forage species that enable ruminants to select a diet in benefit of their nutrition, health and welfare, whilst reducing the negative environmental impacts caused by livestock production systems.

The role of forage management in addressing challenges facing Australasian dairy farming

Forage management underpins the viability of pastoral dairy systems. This review investigated recent developments in forage research and their potential to enable pastoral dairy systems to meet the challenges that will be faced over the next 10 years. Grazing management, complementary forages, pasture diversity, fertiliser use, chemical restriction, irrigation management and pasture breeding are considered. None of these areas of research are looking to increase production directly through increased inputs, but, rather, they aim to lift maximum potential production, defend against production decline or improve the efficiency of the resource base and inputs. Technology approaches consistently focus on improving efficiency, while genetic improvement or the use of complementary forages and species diversity aim to lift production. These approaches do not require additional labour to implement, but many will require an increase in skill level. Only a few areas will help address animal welfare (e.g. the use of selected complementary forages and novel endophytes) and only complementary forages will help address increased competition from non-dairy alternatives, by positively influencing the properties of milk. Overall, the diversity of activity and potential effects will provide managers of pastoral dairy systems with the best tools to respond to the production and environmental challenges they face over the next 10 years.

Tall Wheatgrass and Western Wheatgrass Used for Complementary Cool-Season Forage Systems

Core Ideas Western wheatgrass provides greater individual animal gain potential than tall wheatgrass in the spring. Deferred grazing of rangelands can potentially reduce late season animal performance. Native rangelands with a significant cool-season grass component provides high early season animal gain potential similar to complementary cool-season forage. Seeded monocultures of tall wheatgrass [Thinopyrum ponticum (Podp.) Z.-W. Liu & R.-C. Wang] and western wheatgrass [Pascopyrum smithii (Rydb.) Á. Löve] have demonstrated good yield potential and persistence in plot studies within the southern Great Plains region. These cool-season grasses have potential to serve as a complementary forage in a grazing system with warm-season dominated mixed-grass rangelands, but few studies have included their use under such systems to provide animal data. Multiparous cows with calves at side were stocked on one of three replicated grazing systems: (1) native mixed-grass rangelands from April to October [NR-only], (2) seeded tall wheatgrass from April to mid-June followed by native mixed-grass rangelands from mid-June to October [(TW)NR], or (3) seeded western wheatgrass from April to mid-June followed by native mixed-grass rangelands from mid-June to October [(WW)NR]. Cows grazing native rangelands or western wheatgrass typically had greater spring body weight gain than cows grazing on tall wheatgrass. Spring calf gains on the native rangeland system were similar to calf gains on western wheatgrass, but were greater than calf gains on tall wheatgrass. For the total growing season, cows only on native rangeland had greater total body weight gain than the western wheatgrass and tall wheatgrass complementary systems in two and three of the five years, respectively. Calf body weight gain for the entire growing season was similar in most years. Deferred grazing in the native rangeland portion of the complementary cool-season grass systems allowed indigenous western wheatgrass composition to increase over time. Benefits of the seeded cool-season grasses were masked by the deferred grazing of the native rangeland component and the relatively high beginning proportion of indigenous western wheatgrass in the native rangeland-only system.

Grazer effects on soil carbon storage vary by herbivore assemblage in a semi‐arid grassland

Abstract Accounting for 10%–30% of global soil organic carbon, grassland soils potentially present a large reservoir for storing atmospheric CO2. Livestock grazing management can substantially affect grassland soil carbon (C) storage, but few controlled experiments have explored how herbivore assemblages (different herbivore species and combinations) affect soil C storage. We examined effects of moderate grazing by different herbivore assemblages (no grazing; sheep grazing; cattle grazing; mixed grazing by sheep and cattle) on soil organic carbon storage in two types of grassland communities (high forbs/high diversity and low forbs/low diversity), within a semi‐arid grassland with a 5‐year grazing history. We found that herbivore assemblage generated varying effects on soil C storage and the effects were subject to grassland community types. In the low diversity community, none of three herbivore assemblages studied had obvious effects on soil C storage. In the high diversity community, however, sheep grazing significantly decreased soil C storage due to high selectivity for high quality forbs, and cattle grazing had no effects on soil C storage, while mixed grazing by sheep and cattle significantly increased soil C storage. Overall, soil C storage was highest in mixed‐grazed grassland sites with high diversity. Synthesis and applications. Our study suggests that explicitly incorporating grazer species and the combination of grazing livestock into grassland grazing management may help mitigate greenhouse gas emissions. Caution should be exercised when using grazer species with high food selectivity in grazing management aimed at climate mitigation, especially in grasslands with abundant high quality forbs and high plant diversity, as sheep grazing may reduce soil carbon (C) storage. Moreover, mixed grazing, including multiple herbivore species, may contribute to a reduction in foraging selectivity for a plant community by means of complementary foraging. It could therefore be considered as an optimal grazing management strategy to maintain and improve soil C storage.

Resilience in Forage and Grazinglands

ABSTRACTThe current reality of population growth, resource scarcity, and climate change requires resilient agroecosystems to sustain food production and protect the environment. This manuscript reflects a combined effort of speakers at the 2017 C6 Forage and Grazinglands Division Symposium, which was titled “Resiliency in Forage and Grazinglands.” The symposium brought together speakers representing a diverse cross‐section of forage systems across the United States. Each speaker discussed resilience‐related topics from their specific region, including: the importance of diversity and use of complementary forages in grazing systems, how grazing and defoliation affect resilience, the importance of soil fertility and pest management, and development of decision aids to evaluate resilience in grazinglands. Several themes emerged that we propose would help improve the resilience of forage and grazingland systems: (i) identifying moderately diverse, site‐specific mixtures (grasses–legumes) for use in specific regions of the United States, (ii) greater use of complementary forage species such as C3 and C4 grasses to lengthen the grazing season and provide a buffer against weather variation, (iii) adoption of moderate defoliation intensities to help stabilize forage production and species composition, (iv) more attention to maintaining and improving soil fertility to improve the productivity of desirable forage species and reduce weed pressure, and (v) increase adoption of assessment tools to evaluate the relative “health” and potential resilience of forage‐livestock systems. An integrative management approach that combines many of these elements would help improve the resilience of forage and grazinglands to sustain high productivity under increasingly erratic and extreme weather.

Modelling forage yield and water productivity of continuous crop sequences in the Argentinian Pampas

In recent years, the use of forage crop sequences (FCS) has been increased as a main component into the animal rations of the Argentinian pasture-based livestock systems. However, it is unclear how year-by-year rainfall variability and interactions with soil properties affect FCS dry matter (DM) yield in these environments. Biophysical crop models, such as Agricultural Production Systems Simulator (APSIM), are tools that enable the evaluation of crop yield variability across a wide of environments. The objective of this study was to evaluate the APSIM ability to predict forage DM yield and water productivity (WP) of multiple continuous FCS. Thirteen continuous FCS, including winter and summer crops, were simulated by APSIM during two/three growing seasons in five locations across the Argentinian Pampas. Our modelling approach was based on the simulation of multiple continuous FCS, in which crop DM yields depend on the performance of the previous crop in the same sequence and the final soil variables of the previous crop are the initial conditions for the next crop. Overall, APSIM was able to accurately simulate FCS DM yield (0.93 and 3.2 Mg ha−1 for concordance correlation coefficient [CCC] and root mean square error [RMSE] respectively). On the other hand, the model predictions were better for annual (CCC = 0.94; RMSE = 0.4 g m−2 mm−1) than for seasonal WP (CCC = 0.71; RMSE = 1.9 g m−2 mm−1), i.e. at the crop level. The model performance to predict WP was associated with better estimations of the soil water dynamics over the long-term, i.e. at the FCS level, rather than the short-term, i.e. at the crop level. The ability of APSIM to predict WP decreased as seasonal WP values increased, i.e. for low water inputs. For seasonal water inputs, <200 mm, the model tended to under-predict WP, which was directly associated with crop DM yield under-predictions for frequently harvested crops. Even though APSIM showed some weaknesses in predicting seasonal DM yield and WP, i.e. at the crop level, it appears as a potential tool for further research on complementary forage crops based on multiple continuous FCS in the Argentinian livestock systems.

Carbon and nitrogen isotopic ecology of Holocene camelids in the Southern Puna (Antofagasta de la Sierra, Catamarca, Argentina): Archaeological and environmental implications

This article focuses on camelid isotope ecology from archaeological sites dating to the Holocene (c. 9800–420 BP) located in the Southern Argentine Puna. We present 92 carbon and nitrogen stable isotope values (δ13C and δ15N) extracted from wild (Vicugna vicugna and Lama guanicoe) and domesticated (L. glama) camelid bone collagen. The samples come from the following archaeological sites: Quebrada Seca 3, Cueva Salamanca 1, Peñas de la Cruz 1.1, Casa Chávez Montículos 1 and 4, Bajo del Coypar II, Cueva Cacao 1A, Real Grande 1, and Real Grande 6, all of them located over 3300masl in Antofagasta de la Sierra, Catamarca, Argentina. Mean carbon isotopic relationship (δ13C) was −17.2‰, ranging from −20.1‰ to −11.6‰, and mean nitrogen isotopic relationship (δ15N) was 6.8‰, ranging from 3.4‰ to 10.8‰. We interpret these isotope values against the background of environmental and cultural changes that occurred throughout this period. Variations in δ13C and δ15N values were generally not structured per the availability of different pasture areas across varying altitude. Instead, there was an appreciable increase of some δ13C values in domesticated camelids, suggesting the use of complementary forage in their diet. That aside, the isotope values do not differ significantly among the different camelid taxa. More generally, a noticeable increase in δ15N values, and to a lesser extent in δ13C values, was noted at around 8000 BP, coinciding with a palaeoclimatic phase of extreme regional aridity. Yet, no significant increase of δ13C and δ15N values was recorded during a later arid phase (1500 BP), and no significant variations were observed in isotope values during the arid and wet fluctuations (sub-phases) within each of the principal Holocene palaeoenvironmental phases recorded for the region. These results highlight the varying magnitude of past climatic changes and their differential impact, and emphasise the need to investigate further into the environmental aspects that produce variation in isotope data.

Residual Effect of Herbicides Used in Pastures on Clover Establishment and Productivity

A major hindrance to establishment of successful complementary forage systems that include warm-season perennial grasses and clovers is tolerance of the latter to herbicides available for weed control. Field experiments were conducted in 2013 at two locations in northeast Louisiana to evaluate simulated residual rate effects of fluroxypyr plus triclopyr and 2,4-D plus picloram applied at 0, 0.25, 0.38, and 0.5× use rates immediately after fall planting of ball, white, crimson, and red clover. For all clovers, when averaged across herbicide rates, plant population 161/171 d after planting (DAP), ground cover, and height 184/196 DAP were equivalent for fluroxypyr plus triclopyr and the nontreated control and greater than 2,4-D plus picloram. Averaged across clovers, plant height after all rates of fluroxypyr plus triclopyr was equivalent to the nontreated control (14.2 to 14.3 vs. 15.3 cm) and greater than 2,4-D plus picloram. Compared with the nontreated control, 2,4-D plus picloram at 25, 38, and 50% of the normal use rates reduced height 58, 76, and 85%, respectively. When averaged across clover species, yield for fluroxypyr plus triclopyr at all rates was equivalent to the nontreated control (2,624 to 2,840 vs. 2,812 kg ha−1). Compared with the nontreated control, 2,4-D plus picloram at the 0.25, 0.38, and 0.50× use rates reduced yield 65, 89, and 99%, respectively.

Sequential Relationship between Profitability and Sustainability: The Case of Migratory Beekeeping

When beekeeping is managed on a migratory basis, the bee colony produces physical outputs (honey) and pollination services on a sequence of forage sites. Forage sites are competitors if their flowering periods overlap, and are complementary otherwise. Viable sequences consist only of complementary forage sites. A part of the bee colony’s production time is spent on each forage site in the period when the crop or wild vegetation covering it is in flower. The total period covered by the sequence of sites, including the base site, must be equal to or less than the duration (365 days) of the bee colony’s annual biological cycle. The migratory beekeeper draws up viable sequences of forage sites and calculates their profitability levels. Variations in the profitability of forage sites which alter the composition of the sequence, affecting provision of the non-marketed ecosystem pollination services, impact the biodiversity of the pollinated plants with trickle-down effects on sustainability. In the case of migratory beekeeping, there is, therefore, a sequential relationship between profitability and sustainability.

Modelling Pasture-based Automatic Milking System Herds: System Fitness of Grazeable Home-grown Forages, Land Areas and Walking Distances

To maintain a predominantly pasture-based system, the large herd milked by automatic milking rotary would be required to walk significant distances. Walking distances of greater than 1-km are associated with an increased incidence of undesirably long milking intervals and reduced milk yield. Complementary forages can be incorporated into pasture-based systems to lift total home grown feed in a given area, thus potentially ‘concentrating’ feed closer to the dairy. The aim of this modelling study was to investigate the total land area required and associated walking distance for large automatic milking system (AMS) herds when incorporating complementary forage rotations (CFR) into the system. Thirty-six scenarios consisting of 3 AMS herds (400, 600, 800 cows), 2 levels of pasture utilisation (current AMS utilisation of 15.0 t dry matter [DM]/ha, termed as moderate; optimum pasture utilisation of 19.7 t DM/ha, termed as high) and 6 rates of replacement of each of these pastures by grazeable CFR (0%, 10%, 20%, 30%, 40%, 50%) were investigated. Results showed that AMS cows were required to walk greater than 1-km when the farm area was greater than 86 ha. Insufficient pasture could be produced within a 1 km distance (i.e. 86 ha land) with home-grown feed (HGF) providing 43%, 29%, and 22% of the metabolisable energy (ME) required by 400, 600, and 800 cows, respectively from pastures. Introduction of pasture (moderate): CFR in AMS at a ratio of 80:20 can feed a 400 cow AMS herd, and can supply 42% and 31% of the ME requirements for 600 and 800 cows, respectively with pasture (moderate): CFR at 50:50 levels. In contrast to moderate pasture, 400 cows can be managed on high pasture utilisation (provided 57% of the total ME requirements). However, similar to the scenarios conducted with moderate pasture, there was insufficient feed produced within 1-km distance of the dairy for 600 or 800 cows. An 800 cow herd required 140 and 130 ha on moderate and high pasture-based AMS system, respectively with the introduction of pasture: CFR at a ratio of 50:50. Given the impact of increasing land area past 86 ha on walking distance, cow numbers could be increased by purchasing feed from off the milking platform and/or using the land outside 1-km distance for conserved feed. However, this warrants further investigations into risk analyses of different management options including development of an innovative system to manage large herds in an AMS farming system.

Modelling Pasture-based Automatic Milking System Herds: The Impact of Large Herd on Milk Yield and Economics.

The aim of this modelling study was to investigate the effect of large herd size (and land areas) on walking distances and milking interval (MI), and their impact on milk yield and economic penalties when 50% of the total diets were provided from home grown feed either as pasture or grazeable complementary forage rotation (CFR) in an automatic milking system (AMS). Twelve scenarios consisting of 3 AMS herds (400, 600, 800 cows), 2 levels of pasture utilisation (current AMS utilisation of 15.0 t dry matter [DM]/ha, termed as ‘moderate’; optimum pasture utilisation of 19.7 t DM/ha, termed as ‘high’) and 2 rates of incorporation of grazeable complementary forage system (CFS: 0, 30%; CFS = 65% farm is CFR and 35% of farm is pasture) were investigated. Walking distances, energy loss due to walking, MI, reduction in milk yield and income loss were calculated for each treatment based on information available in the literature. With moderate pasture utilisation and 0% CFR, increasing the herd size from 400 to 800 cows resulted in an increase in total walking distances between the parlour and the paddock from 3.5 to 6.3 km. Consequently, MI increased from 15.2 to 16.4 h with increased herd size from 400 to 800 cows. High pasture utilisation (allowing for an increased stocking density) reduced the total walking distances up to 1 km, thus reduced the MI by up to 0.5 h compared to the moderate pasture, 800 cow herd combination. The high pasture utilisation combined with 30% of the farm in CFR in the farm reduced the total walking distances by up to 1.7 km and MI by up to 0.8 h compared to the moderate pasture and 800 cow herd combination. For moderate pasture utilisation, increasing the herd size from 400 to 800 cows resulted in more dramatic milk yield penalty as yield increasing from c.f. 2.6 and 5.1 kg/cow/d respectively, which incurred a loss of up to $AU 1.9/cow/d. Milk yield losses of 0.61 kg and 0.25 kg for every km increase in total walking distance (voluntary return trip from parlour to paddock) and every one hour increase in MI, respectively. The high pasture utilisation combined with 30% of the farm in CFR in the farm increased milk yield by up to 1.5 kg/cow/d, thereby reducing loss by up to $0.5/cow/d (c.f. the moderate pasture and 800 cow herd scenario). Thus, it was concluded that the successful integration of grazeable CFS with pasture has the potential to improve financial performance compared to the pasture only, large herd, AMS.

Effect of climate variability on pasture-based dairy feeding systems in south-east Australia

The Australian dairy industry relies primarily on pasture for its feed supply. However, the variability in climate affects plant growth, leading to uncertainty in dryland pasture supply. This paper models the impact of climate variability on pasture production and examines the potential of two pasture-based dairy feeding systems: (1) to experience winter deficits; (2) to carry forward the conserved pasture surpluses as silage for future use; and (3) to conserve pasture surpluses as hay. The two dairy feeding systems examined were a traditional perennial ryegrass-based feeding system (ryegrass max. – RM) and a system that incorporated double cropping into the perennial ryegrass pasture base (complementary forage – CF). The conditional probability of the RM and CF systems to generate pasture deficits in winter were 94% and 96%, respectively. Both systems could carry forward the surplus silage into the following lactation almost once in every 4–5 years with the RM system performing slightly better than the CF system. The proportions of the grain-based concentrates fed in the two systems were 25% and 27% for the RM and CF systems, respectively. This study suggests that double-cropping systems have the potential to provide high-quality feed to support the feed gaps when pasture is not available due to increased variability in climatic conditions.

Cool-Season Grass Biomass in the Southern Mixed-Grass Prairie Region of the USA

Emphasis is trending toward future bioenergy production being derived from cellulosic materials rather than starch from seed crops. The majority of research on perennial biomass production for conversion to ethanol or other biofuel has used warm-season grasses as the feedstock material. Some cool-season grasses also have great potential for biomass production, even in the southern prairie region. A study was conducted for 4 years to evaluate the dry matter production potential of several cool-season grass cultivars in west-central Kansas. Ten cultivars were grown at two locations, one an upland soil and the other a lowland soil, and harvested in late June from 2007 to 2010 when fully headed with mature seed. Three cultivars, one tall [Thinopyrum ponticum (Podp.) Barkw. & D.R. Dewey], intermediate [T. intermedium (Host) Barkw. & D.R. Dewey], and western wheatgrass [Pascopyrum smithii (Rydb.) Love], had the greatest biomass production with 4,525–4,840 kg ha−1 dry matter averaged over four years at an upland location. At a lowland location, three cultivars, either intermediate or tall wheatgrasses, averaged 5,340–5,490 kg ha−1 dry matter over the 4 years. During the particularly moist spring of 2007, three cultivars at the upland location and eight cultivars at the lowland location produced over 9,000 kg ha−1 dry matter. All cultivars increased in plant stand frequency from 2006 to 2011, except for the western wheatgrass and Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski] cultivars that already had a high frequency before the first biomass harvest. These grasses may add versatility to production systems by not only serving as complementary forage for grazing or hay, but also by providing an alternative feedstock for cellulosic ethanol and combustion energy production.

A Potential Role of Shrimp Farms for the Conservation of Nearctic Shorebird Populations

Shrimp aquaculture farms have greatly expanded at tropical areas worldwide, especially during the past three decades. One of the main core areas of this expansion was the northwestern coast of Mexico, prompting conservation concern for the shorebird populations that spend the nonbreeding period (October to March) in the region. We conducted a series of counts and behavioral observations to evaluate the importance of a shrimp farm as foraging habitat for shorebirds, relative to adjacent intertidal areas, during and after the shrimp harvest period at a tropical wetland in Sinaloa, Mexico, 2012 and 2013. Overall, low-tide counts within the entire wetland had an average of 3,168 ± 605 (SE) shorebirds during the shrimp harvest period (October–November) and subsequently dropped to 1,408 ± 373 birds following harvest (December to January), when shrimp ponds were emptied and foraging opportunities were reduced. The proportion of counts at the shrimp farm relative to total counts over the entire wetland ranged from 10 to 80 % for different shorebird species and dropped to 0 to 10 % in the postharvest period. During the harvesting period, black-necked stilt, American avocet, willet, and whimbrel selected shrimp ponds over intertidal areas to forage during low tide, while marbled godwit, western sandpiper, and dowitchers did not. The proportion of shorebirds observed feeding at the shrimp farm ranged between 60 and 90 % for most species and did not differ between low- and high-tide counts. These results suggest that shrimp farms can provide ephemeral but important complementary foraging areas for shorebirds, and appropriate management of existing farms may aid in conservation efforts for these species.

Synthetic estrogen directly affects fish biomass and may indirectly disrupt aquatic food webs

Endocrine-disrupting chemicals are known to alter the fitness of individual organisms via changes in growth, behavior, and reproduction. It is largely unknown, however, whether these effects cascade through the food web and indirectly affect other, less sensitive organisms. The authors present results from a mesocosm experiment whereby the effects of the synthetic estrogen 17α-ethinylestradiol (EE2) were quantified in pelagic communities. Treatment with EE2 at a concentration of 28 ng/L had no large effects on the pelagic communities composed only of phytoplankton and zooplankton. In communities where planktivorous roach (Rutilus rutilus) were also present, however, EE2 caused a significant reduction in fish biomass. Moreover, zooplankton biomass was higher in the EE2 treatments, suggesting that zooplankton may have been released from fish predation. Hence, the direct effect of EE2 on roach may have cascaded down the food web to produce positive indirect effects on zooplankton. This result was supported in complementary foraging experiments with roach, showing reduced foraging performance after exposure to EE2. Despite the observed negative effect of EE2 on roach and the positive indirect effect on zooplankton, these effects did not cascade to phytoplankton, possibly because only copepods, but not cladocerans-the major grazers in these systems-were released from fish predation. The authors conclude that the known reproductive impairment in fish by EE2 in combination with the disturbed foraging performance observed in the present study may be a disadvantage to fish that may result in increasing abundance or biomass of prey such as zooplankton. Hence, EE2 may have consequences for both the structure and function of freshwater communities.

Increasing home-grown forage consumption and profit in non-irrigated dairy systems. 3. Intake, milk production and composition, bodyweight and body condition score

This paper reports the performance [intake, milk production, bodyweight and body condition score (BCS)] of cows managed under two feeding systems over 4 years (June 2005–May 2009) in south-west Victoria, Australia. The feeding systems were ‘Ryegrass Max’ (RM) a well managed perennial ryegrass pasture-based system stocked at 2.2 cows/ha, and a ‘Complementary Forage’ (CF) system based on perennial ryegrass, tall fescue and a double crop of winter-sown cereal and summer-sown brassica crops stocked at 2.82 cows/ha. There were no significant differences in milk production per lactation between feeding systems, with an average of 543 and 553 kg milk solids per cow (1246 and 1642 kg milk solids per ha) produced in the RM and CF systems, respectively. These production levels were 20.9 and 10.8% above pre-experimental model targets, respectively. The bodyweight and BCS of multiparous cows were not significantly different between the two feeding systems; however, bodyweight of heifers in early lactation declined more rapidly in the CF compared with RM feeding system. Over the 4-year study in the RM system pasture comprised 60% of total DM consumed (grazed + conserved), with 26% of the ration being concentrate and the balance being purchased hay supplements. In the CF system, home-grown forage contributed 57.9% of total DM consumed of which 46.6% was pasture (grazed + conserved) and 11.3% was from the double cropping system. These levels of home-grown forage consumption were lower than those predicted by the pre-experimental modelling, leading to higher than predicted levels of purchased concentrates and conserved forages being fed. The lower than expected levels of consumption of the forages produced in the double cropping system reflected both the low intake potential and moderate nutritive value of cereal silage, and the failure of establishment and subsequent low DM yields from the summer brassica crop. Further work is required to determine the risk of implementing CF in rain-fed dairy systems reflecting uncertainties in forage management planning and nutrient delivery to support high levels of milk production.