The effect of sward surface height on the response to mixed grazing by cattle and sheep

Grassland biodiversity and ecosystem functions benefit more from cattle than sheep in mixed grazing: A meta-analysis

Grasslands have been widely grazed for livestock production by cattle and sheep. However, previous studies have mainly focused on the impacts of single-species grazing on grassland biodiversity and ecosystem functions; the effects of mixed grazing of cattle and sheep remain largely unknown. We conducted a meta-analysis to examine the impacts of mixed grazing and analyzed the relative roles of cattle and sheep on grassland biodiversity and multiple ecosystem functions. Mixed grazing studies mainly originated from Europe, the USA, and China. Generally, cattle and sheep exhibited distinctive impacts on grassland biodiversity and functions in single-species and mixed grazing regimes. Cattle grazing alone increased plant diversity and soil organic carbon content (SOC), while sheep grazing alone had little impact. Compared to single-species grazing, mixed grazing generally increased plant density and richness of insect herbivores and decreased soil nematode richness, but did not alter plant biomass, soil nitrogen, or nematode abundance. Cattle in the mixed grazing regime increased plant diversity, biomasses of forbs and legumes, SOC, and liveweight gains of livestock. The mixed grazing impacts were further regulated by climate conditions, grazing intensity, and grazing duration. Our findings provide compelling evidence that mixed grazing benefits biodiversity, soil carbon sequestration, livestock production, and community structure of grasslands, and cattle are more influential than sheep in creating the benefits of mixed grazing for sustainable management of grasslands.

Combining beef cattle and sheep in an organic system. I. Co-benefits for promoting the production of grass-fed meat and strengthening self-sufficiency

Numerous advantages of combining cattle and sheep have been demonstrated at the grazing-season level, but the effects of this practice on system self-sufficiency require system-level and longer-term studies. We established three grassland-based organic systems as separate farmlets: one mixed system combining beef cattle and sheep (MIX) and two specialised systems, beef cattle (CAT) and sheep (SH), to serve as reference points. These farmlets were managed for 4 years, to assess the benefits of combining beef cattle and sheep in promoting the production of grass-fed meat and strengthening system self-sufficiency. The ratio of cattle to sheep livestock units in MIX was 60:40. The surface area and stocking rate were similar across all systems. Calving and lambing were adjusted to grass growth to optimise grazing. Calves were pasture-fed from 3 months old on average until weaning in October, fattened indoors with haylage and slaughtered at 12-15 months. Lambs were pasture-fed from 1 month old on average until slaughter; if lambs were not ready for slaughter when the ewes mated, they were stall-finished with concentrates. The decision to supplement adult females with concentrate was based on the achievement of a target body condition score (BCS) at key periods. The decision to treat animals with anthelmintics was based on mean faecal egg excretion remaining below a certain threshold. A higher proportion of lambs were pasture-finished in MIX vs SH (P < 0.001) due to a higher growth rate (P < 0.001) which led to a lower age at slaughter (166 vs 188 days, P < 0.001). Ewe prolificacy and productivity were higher in MIX vs SH (P < 0.02 and P < 0.065, respectively). The levels of concentrate consumption and number of anthelmintic treatments in sheep were lower in MIX vs SH (P < 0.01 and P < 0.08). Cow productivity, calf performance, carcass characteristics and the level of external inputs used did not differ between systems. However, cow BW gain during the grazing season was higher in MIX vs CAT (P < 0.05). These outcomes validated our hypothesis that the association of beef cattle and sheep promoted the self-sufficient production of grass-fed meat in the sheep enterprise. It also promoted better ewe and cow BCS and BW at key stages of the reproduction cycle and better development of the females used for replacement, which may enhance animal and system resilience.

Animal board invited review: Grassland-based livestock farming and biodiversity

Grasslands dominate land cover nationally and globally, and their composition, structure and habitat value are strongly influenced by the actions of domestic and wild grazing animals that feed on them. Different pastures are characterised by varying opportunities for selective feeding by livestock; agronomically improved, sown swards generally consist of a limited range of plant species whereas longer-term leys and semi-natural grasslands are characterised by a more diverse mixture of plants. In the case of botanically diverse permanent pastures/grazing lands, the dietary preferences of different grazers have a more pronounced effect on the botanical composition of the sward in the longer term. Selection of a dominant species within the sward can give less abundant components a chance to compete, increasing community evenness and species richness. Conversely, the selection of minor components reduces sward compositional heterogeneity and hence plant species richness and evenness. Body size, gut type (foregut vs hindgut fermentation), physiological status (growing, pregnant, lactating), metabolic status (extent of body reserves) and environmental conditions all influence the nutrient requirements of a given animal and related foraging priorities. The diet selected is also strongly influenced by the availability of preferred food items, and their vertical and horizontal distribution within the sward. In general, larger animals, such as cattle and horses, are less selective grazers than smaller animals, such as sheep and goats. They are quicker to switch to consuming less-preferred sward components as the availability of preferred resources declines due to their greater forage demands, and as a result can be very effective in controlling competitive plant species consistently avoided by more selective grazers. As a result, low-intensity mixed grazing of cattle and sheep has been shown to improve the diversity and abundance of a range of taxa within grazed ecosystems. Mixed/co-species grazing with different animals exploiting different grassland resources is also associated with increased pasture use efficiency in terms of the use of different sward components and related improvements in nutritional value. In situations where cattle are not available, for example if they are not considered commercially viable, alternative species such as goats, ponies or South American camelids may offer an opportunity to diversify income streams and maintain productive and biodiverse pastures/grazing lands. Stocking rate and timing of grazing also have a considerable role in determining the impact of grazing. Regardless of the species grazing or the pasture grazed, grazing systems are dynamic since selective grazing impacts the future availability of sward components and subsequently dietary choices. New technologies under development provide opportunities to monitor plant/animal interactions more closely and in real time, which will in future support active management to deliver targeted biodiversity gains from specific sites.

Performance and parasitological parameters of steers sequentially grazed with lambs

In the majority of mixed or sequential gazing studies with sheep, cattle performance remained unaffected. However, the treatment regime of the sheep in these studies was often intense and this may have limited cross-transmission of nematodes from sheep to cattle. We conducted a sequential grazing trial with cattle and sheep with moderate anthelmintic intervention. Twenty first season grazing steers were stratified to 10 couples according to their origin, egg excretion per gram faeces (EPG), metabolic weight and previous weight gain record. Thirty naturally infected ewe lambs were stratified to 5 groups according to metabolic live weight and EPG. Five pairs of the steers were sequentially grazed with the 5 groups of lambs whereas another five pairs of steers served as control. Grazing duration was 70 days with a subsequent indoor period of additional 35 days for the steers. Weight and EPG was recorded 3 days before and 27, 49, 70 and 105 days after trial start. The recorded live-weight of the sequentially grazed steers was 182 ± 14, 191 ± 11, 205 ± 15, 219 ± 15 and 236 ± 18 and the live-weight of the control steers was 180 ± 18, 193 ± 19, 203 ± 21, 217 ± 24 and 234 ± 24 kg respectively. The EPG of the sequentially grazed steers 3 days before grazing start and at day 27, 49, 70 and 105 was 94 ± 100, 95 ± 48, 49 ± 42, 58 ± 41 and 140 ± 73 EPG respectively. The EPG of the control steers at the same dates was 96 ± 82, 98 ± 24, 104 ± 77, 98 ± 71 and 270 ± 287 EPG respectively. The sequentially grazed steer groups did not differ from the control groups with regard to EPG, live weight and daily weight gain. However, the sequentially grazed steers showed elevated pepsinogen levels compared to the control steers (e.g. 3.34 ± 1.05 units tyrosine and 1.29 ± 0.50 units tyrosine after 70 days of grazing, respectively). Larval samples from individual steer coprocultures of both groups were tested PCR-positive for Cooperia oncophora, Ostertagia ostertagi and Haemonchus contortus. We conclude that short term sequential grazing of first season grazing steers with lambs excreting mainly eggs of Haemonchus spp. did not adversely affect steer performance despite increased pepsinogen values. However, hot and dry conditions may have had a suppressive effect on larval development, migration and finally uptake by the steers.

Mixed grazing of adult goats and cattle: Lessons from long-term monitoring

Mixed grazing of breeding goats and cattle (goats to cattle ratio: about 50 %, based on metabolic weight) was monitored for 2 years on a rotational pasture with the two species grazing together, then for 5 years with cattle grazing immediately after goats. For both modalities, the level of goat parasite infection was not significantly different from that of the control groups. Nevertheless, the association allowed a slight improvement in kid growth and goat productivity, probably in relation to a better food quality. The response of adult goats to mixed grazing is therefore very different from that previously obtained with kids post-weaning. The question of the relationship between heterogeneity of pastures, knowledge of their environment, grazing behaviour of adult goats and risk of infection with gastrointestinal nematodes requires further investigation.

Impacts of mixed-grazing on root biomass and belowground net primary production in a temperate desert steppe

The impacts of large herbivores on plant communities differ depending on the plants and the herbivores. Few studies have explored how herbivores influence root biomass. Root growth of vegetation was studied in the field with four treatments: sheep grazing alone (SG), cattle grazing alone (CG), mixed grazing with cattle and sheep (MG) and no grazing (CK). Live and total root biomasses were measured using the root ingrowth core and the drilling core, respectively. After 2 years of grazing, total root biomass showed a decreasing trend while live root biomass increased with time during the growing seasons. Belowground net primary production (BNPP) among the treatments varied from 166 ± 32 to 501 ± 88 g m-2 and root turnover rates (RTR) varied from 0.25 ± 0.05 to 0.70 ± 0.11 year-1. SG had the greatest BNPP and RTR, while the CG had the smallest BNPP and RTR. BNPP and RTR of the MG treatment were between those of the CG and SG treatments. BNPP and RTR of the CK were similar to MG treatment. Compared with other treatments, CG had a greater impact on dominant tall grasses species in communities. SG could decrease community diversity. MG eliminated the disadvantages of single-species grazing and was beneficial to community diversity and stability.

Mixed grazing systems benefit both upland biodiversity and livestock production

Background

With world food demand expected to double by 2050, identifying farming systems that benefit both agricultural production and biodiversity is a fundamentally important challenge for the 21^st century, but this has to be achieved in a sustainable way. Livestock grazing management directly influences both economic outputs and biodiversity on upland farms while contributing to potentially damaging greenhouse gas emissions, yet no study has attempted to address these impacts simultaneously.

Methods

Using a replicated, landscape-scale field experiment consisting of five management ‘systems’ we tested the effects of progressively altering elements within an upland farming system, viz i) incorporating cattle grazing into an upland sheep system, ii) integrating grazing of semi-natural rough grazing into a mixed grazing system based on improved pasture, iii) altering the stocking ratio within a mixed grazing system, and iv) replacing modern crossbred cattle with a traditional breed. We quantified the impacts on livestock productivity and numbers of birds and butterflies over four years.

Results, Conclusion and Significance

We found that management systems incorporating mixed grazing with cattle improve livestock productivity and reduce methane emissions relative to sheep only systems. Systems that also included semi-natural rough grazing consistently supported more species of birds and butterflies, and it was possible to incorporate bouts of summer grazing of these pastures by cattle to meet habitat management prescriptions without compromising cattle performance overall. We found no evidence that the system incorporating a cattle breed popular as a conservation grazer was any better for bird and butterfly species richness than those based on a mainstream breed, yet methane emissions from such a system were predicted to be higher. We have demonstrated that mixed upland grazing systems not only improve livestock production, but also benefit biodiversity, suggesting a ‘win-win’ solution for farmers and conservationists.

Effects of co-grazing dairy heifers with goats on animal performance, dry matter yield, and pasture forage composition

Mixed livestock grazing can offer an alternative management system for rearing dairy replacement heifers (Bos taurus). A 2-yr study was conducted during 2009 (yr 1) and 2010 (yr 2) to determine the effects of co-grazing Holstein heifers under rotational stocking with Boer × Kiko goats on animal performance, pasture DM yield, and botanical composition. Each year, 24 heifers (134 ± 6 d of age and 147.4 ± 31.2 kg BW in yr 1; 166 ± 11 d of age and 168.0 ± 27.6 kg BW in yr 2) and 6 goats (2 yr old and 39.7 ± 16.2 kg BW in yr 1; 1 yr old and 33.7 ± 7.4 kg BW in yr 2) were divided into 6 paddocks with 4 heifers and 2 goats, where applicable, per group. Low endophyte-infected tall fescue (Festuca arundinacea Schreb.) and white clover (Trifolium repens L.) pastures were used to evaluate 2 grazing strategies (heifers grazed alone [HO] or heifers co-grazed with goats [HG]). In addition, 6 goats were assigned to 2 paddocks and grazed alone (GO) each year to estimate goat pasture forage intake and compare Haemonchus contortus infection to co-grazed goats. Forage samples were taken monthly to assess DM yield and botanical composition. Samples collected for botanical composition were manually sorted into grass, legume, and weed species. Forage DMI was estimated using a rising plate meter before and after grazing. Heifer BW at the conclusion of yr 1 and yr 2 did not differ between HO and HG (P = 0.40 and P = 0.12, respectively). Likewise, overall ADG did not differ between HO and HG, averaging 0.65 kg/d and 0.63 kg/d over both grazing seasons (P = 0.70). Grazing strategy did not affect forage or total DMI in yr 1; however, HO consumed 2.3 kg/d more forage DM than HG (P < 0.01), resulting in greater total DMI for HO in yr 2 (P < 0.01). Heights at the hip and withers were greater for HO than for HG during both grazing seasons (P < 0.05). Weed presence did not differ between grazing strategies over both grazing seasons as determined by manual harvesting, but visual estimation of botanical composition at the end of yr 2 showed that HO paddocks had 3.5 times more weed presence than HG pastures (P < 0.01). Within the confines of this study, co-grazing did not affect overall heifer BW gain, but it decreased DMI, suggesting that dairy heifers can be co-grazed with goats without negative effects on ADG or feed efficiency.

Effects of maternal protein nutrition and subsequent grazing on chicory (Cichorium intybus) on parasitism and performance of lambs

Forty-eight 4- to 5-yr-old Blackface x Bluefaced Leicester (Mule) ewes and their 24-d-old twin lambs were used to assess the effects of maternal protein nutrition and subsequent grazing on chicory (Cichorium intybus) on performance and parasitism. The experiment consisted of 2 grazing periods: safe pasture period and experimental pasture period. During an adaptation period of 66 d, ewes were infected through oral dosing with Teladorsagia circumcincta infective larvae (3 d per wk) and were supplemented with protein (HP) or not (LP) for the last 45 d of this period. At the end of this period, ewes and their lambs were turned out onto a parasitologically safe pasture; all ewes continued to be dosed with parasite (once a week), and HP ewes received protein supplementation for the first 35 d. Ewes and lambs grazed the safe pasture for an additional 43 d after termination of protein supplementation and of oral dosing with parasites. Ewes and their lambs were then moved onto newly established experimental pastures sown with chicory or grass/clover (Lolium perenne/Trifolium repens). During the safe pasture period, HP ewes had decreased fecal egg counts (FEC) compared with LP ewes, whereas HP lambs had temporarily less (P < 0.05) FEC, decreased (P < 0.001) plasma pepsinogen concentrations, and grew faster (P = 0.028) than LP lambs. Lambs grazing chicory had consistently less (P < 0.001) FEC and grew faster (P = 0.013) than lambs grazing grass/clover but had greater (P < 0.001) concentrations of pepsinogen. Pasture larvae counts were decreased (P = 0.07) for the chicory compared with the grass/clover plots. There were no interactions (P > 0.10) between maternal nutrition and grazed forage type on performance or parasitological measurements. Our results suggest that increased maternal protein nutrition and subsequent grazing of chicory independently improve lamb performance and reduce lamb parasitism.