Pastoral Farming Systems Research Articles

Modelling pastoral farm systems — Scaling from farm to region

Farm system and nutrient budget models are increasingly being used to inform and evaluate policy options on the impacts of land use change on regional environmental and economic performance. In this study, the common approach of up-scaling representative farm systems to a regional scale, with a limited input of resource information, was compared with a new approach that links a geospatial land resource information data base (NZLRI, Agribase™) that includes independent estimates of the productive capacity of land parcels, with individual farm-scale simulation (Farmax® Pro and Farmax® Dairy Pro) and nutrient budgeting models (Overseer®). The Southland region of New Zealand, which is currently undergoing enormous land use change, was used as a case study. Model outputs from the new approach showed increased profit of about 75% for the region if the current land area under dairying increases from 16% to 45%, with the shift to dairy constrained to high pasture production classes only. Environmental impacts associated with the change were substantial, with nitrate leaching estimated to increase by 35% and greenhouse gas emissions by 25%. Up-scaling of representative farm systems to the regional scale with limited input of resource information predicted lower potential regional profit and higher N leaching from dairy conversion. The new approach provides a farm scale framework that could easily be extended to include different systems, different levels of farming performance and the use of mitigation technologies.

Integration of measures to mitigate reactive nitrogen losses to the environment from grazed pastoral dairy systems

SUMMARYThe need for nitrogen (N) efficiency measures for dairy systems is as great as ever if we are to meet the challenge of increasing global production of animal-based protein while reducing N losses to the environment. The present paper provides an overview of current N efficiency and mitigation options for pastoral dairy farm systems and assesses the impact of integrating a range of these options on reactive N loss to the environment from dairy farms located in five regions of New Zealand with contrasting soil, climate and farm management attributes. Specific options evaluated were: (i) eliminating winter applications of fertilizer N, (ii) optimal reuse of farm dairy effluent, (iii) improving animal performance through better feeding and using cows with higher genetic merit, (iv) lowering dietary N concentration, (v) applying the nitrification inhibitor dicyandiamide (DCD) and (vi) restricting the duration of pasture grazing during autumn and winter. The Overseer®Nutrient Budgeting model was used to estimate N losses from representative farms that were characterized based on information obtained from detailed farmer surveys conducted in 2001 and 2009. The analysis suggests that (i) milk production increases of 7–30% were associated with increased N leaching and nitrous oxide (N2O) emission losses of 3–30 and 0–25%, respectively; and (ii) integrating a range of strategic and tactical management and mitigation options could offset these increased N losses. The modelling analysis also suggested that the restricted autumn and winter grazing strategy resulted in some degree of pollution swapping, with reductions in N leaching loss being associated with increases in N loss via ammonia volatilization and N2O emissions from effluents captured and stored in the confinement systems. Future research efforts need to include farm systems level experimentation to validate and assess the impacts of region-specific dairy systems redesign on productivity, profit, environmental losses, practical feasibility and un-intended consequences.

Progress towards developing bloat-safe legumes for the farming industry

Proanthocyanidins (PAs) are polymeric flavonoids derived from the phenylpropanoid pathway, and they bind reversibly to forage proteins within the rumen, providing protection from bloat while enhancing protein utilisation and animal production. The occurrence of PAs varies greatly within forage legume species. Foliar PAs are present in Lotus corniculatus (birdsfoot trefoil) and Onobrychis viciifolia (sainfoin), but such species often show poor persistence under grazing. By contrast, Trifolium repens (white clover) and Medicago sativa (lucerne, or alfalfa) have good persistence but negligible amounts of foliar PAs. We altered the accumulation patterns present in lucerne and white clover by the overexpression of an R2R3-MYB transcription factor (TaMYB14) isolated from T. arvense (rabbit’s foot clover), a species with significant levels of leaf PA. Such plants effectively produced PAs of high degree of polymerisation (DP) in leaf tissue by upregulating genes of the PA pathway. By comparing transcriptome pools, we identified additional MYB transcription factors with putative involvement in PA synthesis in white clover and T. arvense, indicating that these species share a complex PA regulation system. Progress towards producing commercial cultivars of lucerne and white clover containing effective levels of PAs has begun. Such plants will provide a viable option for mitigating bloat in pastoral agriculture-based farming systems.

Water footprint of beef cattle and sheep produced in New Zealand: water scarcity and eutrophication impacts

Abstract There is increasing recognition of the tension between livestock production and freshwater availability. Changes in freshwater availability can be generated by both freshwater consumptive and freshwater degradative use. Agriculture is a major water user, and beef cattle and sheep farming is an important agricultural activity in New Zealand (NZ). This study assessed potential environmental impacts associated with water use in beef cattle and sheep farming in NZ, following a water footprint method compliant with life cycle assessment principles with a focus on the water scarcity footprint and eutrophication potential (EP) impacts. The life cycle required for the production of beef cattle and sheep was analysed cradle-to-farm-gate, excluding animal transport or processing. Survey data from Beef and Lamb New Zealand for the year 2009/10 were used to cover a range of beef cattle and sheep farm types throughout NZ (426 farms averaged in seven farm classes), and water scarcity footprint and EP weighted averages were calculated for beef cattle and sheep. The normalised NZ weighted average water scarcity footprint of beef cattle of 0.37 L H2O-eq/kg LW was lower than the published normalised values for the water scarcity footprint of beef cattle produced in Australia (3.3–221 L H2O-eq/kg LW) and in the UK. Also, the NZ weighted average water scarcity footprint of sheep of 0.26 L H2O-eq/kg meat (assuming that 40% LW was converted into meat) was lower than the water scarcity footprint of sheep meat reported for the UK (8.4–23.1 L H2O/kg meat). Blue water losses associated with evapotranspiration from irrigated pasture comprised the greatest proportion of the total water scarcity footprint, despite the small areas of farmland irrigated. The weighted average EP of beef cattle was 51.1 g PO4-eq/kg LW, and the weighted average EP of sheep was 26.1 g PO4-eq/kg LW. The NZ weighted average EP for beef cattle was lower than the 105 g PO4-eq/kg LW reported for European Union suckler beef cattle. On-farm nitrate leaching and phosphorus runoff dominated the EP. From an international marketing perspective, beef cattle and sheep produced in NZ have a potential advantage by having low water scarcity footprints compared to some non-NZ pastoral farming systems due to their production efficiencies and low annual water-stress levels. The impact of NZ pastoral farming on freshwater availability can potentially be reduced by practices that decrease water use, increase feed conversion efficiencies, increase the use of non-irrigated feed supplements, and reduce irrigation. The indicator EP was chosen to enable comparisons with non-NZ studies, but gaseous emissions of nitrogen compounds contributed 33–40% of the total, and their contribution to water pollution is uncertain. This study highlighted the need for a harmonised methodology and as well as to consider specific local contextual information when interpreting the absolute and relative implications of EP results, for example by developing NZ-catchment-specific characterisation factors for aquatic eutrophication in future studies.

Controlled drainage systems to reduce contaminant losses and optimize productivity from New Zealand pastoral systems

Drainage systems are essential for managing soil water levels, thereby ensuring optimal plant productivity while protecting soil quality. Although beneficial, drainage systems are also known to be a significant loss route for dissolved nutrients. A potential way of reducing nutrient loss through drainage systems is to use weirs to strategically control drainage of excess water from the soil profile. This review evaluates the scientific literature to ascertain whether controlled drainage could be a useful crop productivity and nutrient loss mitigation tool for New Zealand pastoral farming systems. While a range of risks and potential disadvantages have been identified, evidence from studies of cropped systems with controlled drainage in Europe, Canada and the US suggests that suitably managed controlled drainage offers significant benefits for water quality, agricultural productivity and nutrient- and water-use efficiency. The practical efficacy of controlled drainage requires field evaluation under New Zealand farming conditions.

Impact of short-interval, repeat application of dicyandiamide on soil N transformation in urine patches

In pastoral farming systems, bovine urine patches are ‘hot-spots’ of elevated soil nitrogen (N). Nitrification in urine patches is linked to deleterious environmental outcomes, such as formation of the greenhouse gas nitrous oxide (N2O). The nitrification inhibitor dicyandiamide (DCD) reduces the rate of nitrification in soils subsequently limiting N-losses. Dicyandiamide's bacteriostatic mode of inhibiting ammonia oxidising bacteria (AOB), has raised concerns about the efficacy of frequent DCD use. For example, frequent use could result in selection for a DCD-tolerant AOB community. Furthermore, the impacts of DCD on other aspects of microbial N transformation in soil are largely unknown. To test the influence of short-term repeat application of DCD on soil N cycling, we established a replicated field-trial in which ±urine and ±DCD were added to pasture soils (fully crossed, 2×2 factorial design). After 57 d, treatments were re-applied. Mineral N pools, pH, DCD concentration, moisture and temperature were measured, along with N2O fluxes. Microbial communities involved in ammonia oxidation (bacteria and archaea), nitrite reduction, and N2O reduction were quantified using real-time PCR targeting functional genes (amoA, nirS, and nosZ). Overall, the addition of DCD significantly (P<0.05) reduced both the formation of nitrate (∼64%), and N2O loss from urine-treated soils (∼44%). The effect of repeating the urine and DCD applications produced similar results with no decline in DCD efficacy. This was despite a doubling in the size of the AOB community, stimulated by the initial urine application. The application of urine+DCD had a significant but minor impact on denitrifying bacteria (nirS), rather the population size of these bacteria correlated with increasing soil temperature over time (rho=0.7; P=0.002). In contrast, copies of nosZ increased with urine addition (P<0.05) but were unaffected by sampling date (increasing soil temperature). Our results demonstrate that an initial DCD application does not affect its efficacy to inhibit nitrification and reduce N2O emissions following a subsequent DCD application 57 days later.

Process-based modelling to understand which ryegrass characteristics can increase production and decrease leaching in grazed grass–legume pastures

A significant challenge for the pastoral farming systems is to maintain or increase production while reducing leaching of nitrogen, and for pastoral systems, this means reducing leaching from urine patches. Here we explore the potential impact of four ryegrass characteristics to increase pasture production and reduce leaching from ryegrass–white clover pastures. We focus on understanding which characteristics are desirable, the stage before investigating the achievability of those characteristics in a breeding program. Those characteristics were: the winter- or summer-dominance of growth (GP); the ability of the plant to intercept radiation at low pasture mass (LI); rooting depth (RD); and resistance to moderate water stress (WF). The impact of these ryegrass characteristics, both singly and combined within a ryegrass–clover pasture, was explored across a range of soils, climates, irrigation management, and urine patch concentrations using the process-based model APSIM. Of the four characteristics tested, LI was the most effective in increasing production and reducing leaching in all environments. The characteristics RD and WF were moderately effective, with RD having a greater impact on reducing leaching whereas WF had a greater effect on increasing production. The characteristic with the least impact was GP and it seems that ryegrass is currently well adapted for typical temperatures in New Zealand. The production and environmental effects of the characteristics were additive. The characteristics should be investigated further in the typically more diverse mixtures normally found in pastures but show promise for achieving improved production while reducing leaching provided they can be achieved in a breeding program.

Reconciling pastoral agriculture and nature conservation: developing a co-management approach in the English uplands

The article assesses the influence of the Common Agricultural Policy (CAP) on the pastoral farming systems in a National Park within the south west of England and more recent attempts to use innovative and participatory techniques to reconcile pastoral farming systems with wildlife management. The paper confirms evidence that the economic sustainability of farm businesses in the UK involved in pastoral farming is reducing, and that wildlife-orientated schemes are changing traditional farming systems in a way that might not be in the long-term interest of wildlife. The data gathered raise questions about the cost-effectiveness of the current environmental approaches, which are government-run with centrally determined prescriptions relating to the natural resource and wildlife. Drawing on the concept of co-management, an alternative approach is identified and explored with both farmers and nature conservation regulators. This approach places more emphasis upon adjusting the traditional farming system of this marginal type of farming to align with the sustainable management of a fragile ecosystem.

Grazing impacts and woodland management in Eriksfjord: Betula, coprophilous fungi and the Norse settlement of Greenland

This paper focuses on the impact of Norse settlement on vegetation and landscape around the head of Tunulliarfik (Eriksfjord) in southern Greenland. Pollen, radiocarbon, microscopic charcoal and fungal spore data are presented from a peat monolith which was collected close to the ruins of a large Norse farm complex (group O39 at Qinngua in the former Eastern Settlement). Landnam is identified at ca. cal. a.d. 1020 by a small decrease in pollen from Betula, a slight increase in Poaceae, and the appearance of pollen from Norse apophytes (native plants favoured and spread by human activity) and anthropochores (not native and unintentionally introduced by people). Increases in microscopic charcoal and palynological richness are also apparent. This pattern is broadly consistent with that seen in other pollen diagrams from this region. The sequence is unusual for Greenland, however, in that relatively high Betula pollen percentages (average 20% TLP) are recorded throughout the period of settlement, up to the end of the 14th century a.d. before the profile becomes truncated. If these data are primarily representative of the dry land vegetation, then they suggest that birch woodland and scrub may well have persisted close to the farm throughout the Norse period. Given the potential resource value of woodland to the settlers, this may imply that birch was being managed sustainably, as was the case in Iceland during the medieval period. Coprophilous fungal spores typically found on animal dung are abundant during the early phase of settlement, yet subsequently decline in abundance. This may indicate a likely decrease in grazing intensity or livestock numbers over time, possibly in response to climatic deterioration and/or soil erosion that is expected to have placed increased stress on the pastoral farming system.

McRae Trust - a study of issues around livestock greenhouse gas emissions and the implications for farmers

McRae Trust Farm was used to examine how hill country farming policies and management affected the quantity of livestock greenhouse gas (GHG) emissions, profitability, and risk. Land use decisions were subject to the opportunities and constraints inherent in the natural soil capital of the farm. Analysis was undertaken using FARMAX® and OVERSEER®. Features of the pastoral farming system in 2009 were compared with 1990, and data around livestock GHG emissions was compared with the methodology proposed in the Climate Change (Agriculture Sector) Regulations 2010 which is intended to be the basis for calculating farmers' liability in 2015. Changing livestock policies can potentially change livestock GHG emissions by around 10%. Reduced emission intensity (kg CO2-e/kg meat &amp; fibre) is achievable, but total GHG emissions may be increased over the baseline. Profitability, as measured by Economic Farm Surplus, may be increased or decreased with no relationship with the level of GHG emissions. Between 1990 and 2009, intensity of GHG emissions has been reduced by about 5% on this farm. An area of 12 ha of forestry will assist in reducing GHG liability in the initial period of agriculture's inclusion in the Emissions Trading Scheme (ETS).

The effect of situational variability in climate and soil, choice of animal type and N fertilisation level on nitrogen leaching from pastoral farming systems around Lake Taupo, New Zealand

Agricultural systems with grazing animals are increasingly under scrutiny for their contribution to quality degradation of waterways and water bodies. Soil type, climate, animal type and nitrogen (N) fertilisation are contributors to the variation in N that is leached through the soil profile into ground and surface water. It is difficult to explore the effect of these factors using experimentation only and modelling is proposed as an alternative. An agro-ecosystem model, EcoMod, was used to quantify the pastoral ecosystem responses to situational variability in climate and soil, choice of animal type and N fertilisation level within the Lake Taupo region of New Zealand. Factorial combinations of soil type (Oruanui and Waipahihi), climate (low, moderate and high rainfall), animal type (sheep, beef and dairy) and N fertilisation level (0 or 60 kg N/ha/yr) were simulated. High rainfall climates also had colder temperatures, grew less pasture and carried fewer animals overall which lead to less dung and urinary N returned. Therefore, even though a higher proportion of N returned ultimately leached at the higher rainfall sites, the total N leached did not differ greatly between sites. Weather variation between years had a marked influence on N leaching within a site, due to the timing and magnitude of rainfall events. In this region, for these two highly permeable soil types, N applied as fertiliser had a high propensity to leach, either after being taken up by plants, grazed and returned to the soil as dung and urine, or due to direct flow through the soil profile. Soil type had a considerable effect on N leaching risk, the timing of N leaching and mean pasture production. Nitrogen leaching was greatest from beef cattle, followed by dairy and sheep with the level of leaching related to urine deposition patterns for each animal type and due to the amount of N returned to the soil as excreta. Simulation results indicate that sheep farming systems with limited fertiliser N inputs will reduce N leaching from farms in the Lake Taupo catchment.

An evaluation of two pastoral dairy production systems using automatic milking technology

The objective of this study was to evaluate the performance of two pastoral farming systems using automatic milking systems (AMS).

Estimating the cost of subclinical parasitism in grazing ewes

The aim of the study was to quantify the cost of gastrointestinal nematode parasitism in a typical New Zealand sheep flock. On the 9th January 2007, 500 ewes from a mixed age flock of 3000 Romney cross-bred ewes were selected. Of these, 250 were given a controlled release capsule releasing a continuous dose of either albendazole or ivermectin over a 100-day period. The other 250 ewes remained as untreated controls. Further capsules were administered to the treatment group on the 12th March, the 12th June and the 26th July. At each of these times, the ewes were weighed and faecal samples were collected for worm egg counts and larval cultures. The initial worm burdens in January were low (mean: 34 epg), but in the untreated ewes rose to high levels before mating in March and reached a mean of 1416 epg. Haemonchus was identified as the principal parasitic genus. In June, epg were reduced to a mean of 526 epg, with Trichostrongylus being the principal genus (48%), whilst in late July mean epg was 826 with Cooperia being the principal genus (60%). Epg of treated ewes were zero throughout that period. Throughout the study, there was a significant difference in body weight of treated ewes over controls, which was 2.7 kg (March), 4.3 kg (June), 5.7 kg (July) and 3.6 kg (November). There were more multiple pregnancies among treated ewes, identified at ultrasound scanning as 12.4 foetuses per 100 ewes ( p < 0.05). At weaning of lambs, on the 26th November, mean body weight of twin lambs born to treated ewes were on average heavier by 2.15 kg ( p < 0.05). Assuming that in treated ewes no adverse effects were observed from subclinical parasitism alone, the benefits of controlling the problem could be clearly evaluated. Innovative ways of controlling subclinical parasitism on pastoral farming systems need to be considered. It should be taken into account that the authors do not recommend repeated anthelmintic treatments, which was performed in the trial, only with a view to meet the specific objectives of the work.

Geographic distribution and environmental characterization of livestock production systems in Eastern Africa

The central role played by livestock in the livelihoods of rural households in the developing world is seldom fully appreciated by policy makers, development agencies and donors. Knowledge gaps in the geographic distribution and environmental determinants of farming systems, especially if viewed through the livestock lens, compound this problem. We have produced a map of pastoral, agro-pastoral and mixed farming systems across Eastern Africa, by analysing datasets collected in the framework of livelihood analysis. Input data were gathered between 2000 and 2007 by various emergency and development agencies for Djibouti, Eritrea, Kenya, Somalia, Uganda and parts of Ethiopia and Sudan. A quantitative definition of the production systems is adopted, based on the ratio of livestock- to crop-derived income. The resulting livelihood-based map of livestock production systems was compared through correspondence analysis to an alternative livestock production systems map, produced independently from environmental data. Convergence between the two mapping approaches was evident. The geographic distribution of the livestock production systems was also modelled using multivariate analysis of remotely sensed and other geospatial datasets. Models show high statistical accuracy, and were thus used to fill the gaps in the observed distribution of livestock production systems. Finally, selected environmental factors underpinning the systems (agro-climatology, human and livestock populations and land cover) were analysed in detail, enabling the livestock production systems to be characterized in terms of them. The regional scope of the map, as well as its direct link with a vast amount of livelihood information, render it a valuable tool for a range of development and research applications, including those related to global change.

Estimating nutrient loss to waterways—an overview of models of relevance to New Zealand pastoral farms

Reliable estimation of nutrient losses from farmland is of increasing interest, driven by both economic and environmental concerns. Routine direct measurement of nutrient losses is currently impractical given the scale and variability of the problem. Simulation models are the best alternative and their use for assessing potential nutrient losses has been increasing worldwide. In New Zealand, there are a considerable number of models in use, or that are being developed, aiming to estimate N and P losses from pastoral fields. This range of alternative models reflects both the different level of detail and scale at which N and P losses can be estimated, and the diverse range of purposes assumed during the model development. Thus, it is important to understand the differences between models in order to select the one that will produce estimates appropriate to the intended use. This work presents an overview of the principal models for estimating nutrient loss being used or developed in New Zealand. It emphasises models that deal with N and P losses from pastoral farming systems, particularly via leaching, and that may allow the handling of different farm management procedures. Most of the models have gone through some testing and are supported by published works, although some are not fully operational yet and others need further evaluation. There is, in general, a lack of organised information about how several of these models work and what their main purposes are. We aim to supply some basic information about the available tools, sorting them into categories to highlight their primary differences and similarities. This is intended to assist discussions about model selection as well to highlight where information gaps about particular models need to be addressed.

Dichelobacter nodosus, Fusobacterium necrophorum and the epidemiology of footrot

Footrot is a debilitating disease of sheep resulting in lameness, production losses and suffering. To study the basic bacteriology of the disease, a survey was initiated across commercial farms and non-commercial research flocks to compare the bacteriology of symptomatic footrot infected sheep with healthy asymptomatic sheep. Of the 80 farmers initially contacted, 14 collected hoof swabs and returned the swabs by post. Following DNA extraction, species-specific PCR was used to identify if Dichelobacter nodosus ( D. nodosus) or Fusobacterium necrophorum (F. necrophorum) species were present on each swab. Of the 42 swabs taken from symptomatic footrot infected sheep, 17 were positive for both F. necrophorum and D. nodosus, two were positive for F. necrophorum only, two for D. nodosus only and 23 swabs were negative for both F. necrophorum and D. nod osus. Of the 50 swabs received from healthy asymptomatic sheep, one was positive for F. necrophorum only and 49 were negative for both D. nodosus and F. necrophorum. This suggests that both F. necrophorum and D. nodosus are linked to footrot in the field in a pastoral farming system. If these bacteria are linked together and collectively cause footrot, this may need to be considered when managing a footrot outbreak, or maintaining a quarantine.

Effects of tillage, simulated cattle grazing and soil moisture on N2O emissions from a winter forage crop

Nitrous oxide (N2O) emissions to the atmosphere from grazed pasture can be high, especially from urine-affected areas. When pastoral soils are damaged by animal treading, N2O emissions may increase. In New Zealand, autumn-sown winter forage crops are often grown as a break-crop prior to re-sowing pasture. When these crops are grazed in situ over winter (as is common in New Zealand) there is high risk of soil damage from animal treading as soil moisture contents are often high at this time of year. Moreover, the risk of soil damage during grazing increases when intensive tillage practices are used to establish these forage crops. Consequently, winter grazed forage crops may be an important source of N2O emissions from intensive pastoral farming systems, and these emissions may be affected by the type of tillage used to establish them. We conducted a replicated field experiment to measure the effects of simulated cattle grazing (mowing followed by simulated treading and the application of synthetic urine) at three soil moisture contents ( field capacity) on measured N2O emissions from soil under an autumn (March) sown winter forage crop (triticale) established with three levels of tillage intensity: (a) intensive, IT, (b) minimum, MT, or (c) no tillage, NT. In all treatments, bulk density in the top 7.5 cm of the soil was unaffected by treading when simulated grazing occurred at field capacity, and by 10% in the MT plots trodden at > field capacity. Treading did not significantly increase the bulk density in the NT plots. Emissions of N2O from the tillage treatments decreased in the order IT > MT > NT. N2O emissions were greatest from plots that were trodden at > field capacity and least from plots trodden at field capacity. The N2O emission from urine-amended NT plots that were trodden at < field capacity was 2.0 kg ha−1 over 90 days (0.25% of the total urine N applied). Decreasing the intensity of tillage used to establish crops and restricting grazing when soils are wet are two of the most effective ways to minimise the risk of high N2O emissions from grazed winter forage crops.

Milking frequency affects the circadian body temperature rhythm in dairy cows

The objective of this study was to investigate milking frequency as a potential stressor in Holstein–Friesian dairy cows managed in a pastoral farming system. The circadian body (vaginal) temperature rhythm was measured in cows milked twice-a-day (2x) or once-a-day (1x) in two experiments. The first experiment was conducted at peak lactation (50 ± 11 days in milk, DIM) and the second in response to a transition from 2x to 1x milking at mid-lactation (153 ± 21 DIM). At peak lactation, body temperature was continuously recorded for seven days in 40 dairy cows, milked either 2x (two groups, n = 10 per group) or 1x (two groups, n = 10 per group) from the time of calving. At mid-lactation, 60 dairy cows were milked either 2x (four groups, n = 5 per group), 1x (four groups, n = 5 per group) or switched from 2x to 1x on the afternoon of 156 DIM (2x:1x, four groups, n = 5 per group). Body temperature was measured in three of the five cows per group (36 cows in total) for 10 days from 153 to 162 DIM. Milk yield and total grazing time (Experiment 2 only) were recorded in all cows. At peak lactation cows milked 2x had a higher ( P ≤ 0.051) mean body temperature between 1600 and 0000 h than 1x cows (38.6 vs. 38.4 °C; SED = 0.03 °C). At mid-lactation, mean body temperature was also elevated between 1600 and 2000 h in 2x cows compared to 1x cows (2x: 38.6 °C, 1x:38.4 °C, SED = 0.04 °C; P < 0.001) and tended ( P = 0.083) to be higher in 2x cows between 2000 and 0000 h. On the day the milking frequency was switched from 2x to 1x (156 DIM), mean body temperature still tended to be higher ( P = 0.087) between 1600 and 2000 h in cows continuing on 2x compared with 2x:1x and 1x cows. Body temperature in 2x:1x cows on 157 DIM was lower than 2x cows and similar to that of 1x cows, but there was no consistent effect of milking frequency on body temperature from 158 to 162 DIM. Cows milked 2x had a higher daily milk yield than 1x cows at peak lactation and at mid-lactation (peak lactation 2x: 28.1 ± 5.1, 1x: 24.5 ± 4.7 kg milk per day). Time spent grazing between 1600 and 2000 h was initially at least 22 min higher ( P = 0.031) in 1x cows than in 2x:1x and 2x cows on 153 DIM but there were no differences ( P ≥ 0.107) in the remaining days of the trial. Milk yield in 2x:1x cows declined rapidly on 156 DIM to be lower ( P < 0.001) than both 2x and 1x cows but from 157 DIM began to follow the same pattern as 1x cows. In conclusion, milking frequency had an effect on the circadian body temperature rhythm, particularly in the late afternoon and evening. There was a decline in body temperature from 1600 h if milking frequency was reduced, but this change was not explained by treatment differences in time spent grazing during the same period. The alterations in the circadian body temperature rhythm with milking frequency were likely due to differences in metabolic activity and internal heat production associated with locomotor activity and relative milk production rather than physiological stress per se.

Supplementary feeding at milking and minimum milking interval effects on cow traffic and milking performance in a pasture-based automatic milking system

In extensive pastoral dairy farming systems herds graze 12 months of the year with the majority fed a near-100% pasture or conserved pasture diet. The viability of automatic milking in these systems will depend partly upon the amount of supplementary feed necessary to encourage cows to walk from the pasture to the milking unit but also on the efficient use of the automatic milking system (AMS). This paper describes a study to determine the importance of offering concentrate in the milking unit and the effect of minimum milking interval on cow movement and milking performance in a pasture-based AMS. The effects of feeding rate (FR0=0 kg or FR1=1 kg crushed barley/d) and minimum milking interval (MM6=6 h or MM12=12 h) on cow movement and behaviour during milking were studied in a multi-factorial cross-over (feeding level only, 4 weeks per treatment) experiment involving 27 mixed-breed cows milked through a single AMS. Feeding 1 kg barley in the milking unit resulted in a higher visiting frequency to the pre-selection unit (FR0=4.6 visits/d, FR1=5.4 visits/d, sed=0.35, P<0.05) and a higher yield (FR0=22.5 kg/d, FR1=23.6 kg/d, sed=0.385, P<0.01) but had no effect on milking frequency (FR0=1.6 milkings/d, FR1=1.7 milkings/d, sed=0.04, NS). Minimum milking interval was the major factor influencing milking frequency (MM6=1.9, MM12=1.4 milkings/d, sed=0.15, P<0.01). The absence of feeding in the milking unit had no negative effect on behaviour during milking or the number of cows that had to be manually driven from the paddock. The results show that automatic milking can be combined with a near-100% pasture diet and that milking interval is an important determinant for maximizing milk harvested per AMS.

Responses to tuberculin among Zebu cattle in the transhumance regions of Karamoja and Nakasongola district of Uganda

Responses to tuberculin in Zebu cattle of the transhumant pastoral farming system in Karamoja region and Nakasongola district in the north-eastern and mid-central regions in Uganda, respectively, were investigated using a comparative intradermal tuberculin skin test. Of the 1864 cattle tested from 30 large units (superherds) in Karamoja and 7 herds in Nakasongola, a total of 28 animals from 19 herds (51.4%) tested positive. Inter-district tuberculin reactor prevalence variations seemed to be influenced by climate, with impact on both the management patterns and transmissibility of agent. High herd tuberculin reactor prevalence (51.4%) was attributed to widespread contacts and mixing of animals between herds. Low individual animal tuberculin test positivity (mean = 1.4%) was attributed to low transmissibility of the agent under the Karamoja climate, which is semi-arid, and to increased resistance due to non-specific response to environmental mycobacteria and natural selection, since there was no active control against bovine tuberculosis. Owing to similarities in management practices in Karamoja and widespread risk factors, it was difficult to identify which were more important, but variations in sources of drinking water pointed to provision of lake and borehole water during dry season as reducing the risk. Positive bovine tuberculin reactor prevalence and skin reactor status were related to age.