Grass-based Systems Research Articles

Short communication: Effects of changing teatcup removal and vacuum settings on milking efficiency of an automatic milking system

The aim of this experiment was to assess strategies to reduce milking time in a pasture-based automatic milking system (AMS). Milking time is an important factor in automatic milking because any reductions in box time can facilitate more milkings per day and hence higher production levels per AMS. This study evaluated 2 end-of-milking criteria treatments (teatcup removal at 30% and 50% of average milk flowrate at the quarter-level), 2 milking system vacuum treatments (static and dynamic, where the milking system vacuum could change during the peak milk flowrate period), and the interaction of these treatment effects on milking time in a Lely Astronaut A4 AMS (Maassluis, the Netherlands). The experiment was carried out at the research facility at Teagasc Moorepark, Cork, Ireland, and used 77 spring-calved cows, which were managed on a grass-based system. Cows were 179 DIM, with an average parity of 3. No significant differences in milk flowrate, milk yield, box time, milking time, or milking interval were found between treatments in this study on cows milked in an AMS on a pasture-based system. Average and peak milk flowrates of 2.15 kg/min and 3.48 kg/min, respectively, were observed during the experiment. Small increases in maximum milk flowrate were detected (+0.09 kg/min) due to the effect of increasing the system vacuum during the peak milk flow period. These small increases in maximum milk flowrate were not sufficient to deliver a significant reduction in milking time or box time. Furthermore, increasing the removal setting from 30% of the average milk flowrate to 50% of the average milk flowrate was not an effective means of reducing box time, because the resultant increase in removal flowrate of 0.12 kg/min was not enough to deliver practical or statistically significant decreases in milking time or box time. Hence, to make significant reductions in milking time, where cows have an average milk flow of 2 kg/min and yield per milking of 10 kg, end-of-milking criteria above 50% of average milk flowrate at the quarter level would be required.

Suckler Bulls Slaughtered at 15 Months of Age: Effect of Different Production Systems on the Fatty Acid Profile and Selected Quality Characteristics of Longissimus Thoracis.

The objective was to compare the quality of beef from bulls reared in typical Irish indoor systems or in novel grass-based systems. Bulls were assigned to one of the following systems: (a) grass silage plus barley-based concentrate ad libitum (CON); (b) grass silage ad libitum plus 5 kg of concentrate (SC); (c) grazed grass without supplementation (G0); (d) grazed grass plus 0.5 kg of the dietary dry matter intake as concentrate (GC) for (100 days) until slaughter (14.99 months). Carcass characteristics and pH decline were recorded. Longissimus thoracis was collected for analytical and sensory analysis. Lower carcass weight, conformation and fatness scores were found for grazing compared to CON and SC groups. CON bulls had highest intramuscular fat and lighter meat colour compared with grazing bulls. The SC meat (14 days aged) was rated higher for tenderness, texture, flavour and acceptability compared with grazing groups. CON saturated and monounsaturated fatty acid (FA) concentration was highest, conversely, omega-3 FA concentration was higher for GC compared with CON, while no differences were found in polyunsaturated FA. In conclusion, while market fatness specification was not reached by grazed grass treatments, beef eating quality was not detrimentally affected and nutritional quality was improved.

The effect of concentrate supplementation type on milk production, dry matter intake, rumen fermentation, and nitrogen excretion in late-lactation, spring-calving grazing dairy cows

In Ireland, milk is primarily produced using a spring-calving grass-based system, with the use of concentrate supplementation mainly when pasture availability and quality are reduced. In the autumn, when cows are in late lactation, reduced pasture productivity results in reduced milk yield and altered milk composition. Nitrogen utilization efficiency also reduces as lactation progresses. Concentrate supplementation has been found to increase milk production and reduce nitrogen (N) excretion, as high-N grass is usually replaced by a lower-N supplement; however, there is a paucity of information with regard to the optimum type of supplementation in late lactation. Therefore, the objective of this research is to investigate the effect of different concentrate supplementation types, based on barley or maize, on milk production, dry matter intake (DMI), rumen fermentation, and N excretion in late-lactation, spring-calving, grazing dairy cows. Thirty-six Holstein Friesian dairy cows were blocked on days in milk (185 DIM) and balanced for parity, pre-experimental milk yield, milk composition, and body condition score. Cows were randomly assigned to 1 of 3 dietary treatments in a randomized complete block design (n = 12). The 3 treatments consisted of a perennial ryegrass-based pasture-only (PO) treatment and pasture plus either of 2 supplementary concentrates, based on barley (PB) or maize (PM). The diets were fed for a 14-d acclimatization period and then for a further 63-d experimental period. Cows offered PO had a lower daily milk yield (15.1 kg) than PB (18.2 kg) or PM (16.8 kg). Similarly, PO had lower daily milk solids yield (1.46 kg) than PB or PM (1.68 and 1.53 kg, respectively). Cows offered PB had a greater milk yield and higher fat and protein yields than those offered PM. Offering PB increased total DMI (19.5 kg) compared with PO (17.7 kg), and milk response to concentrates was also greater for PB compared with PM (1.21 vs. 0.71 kg of milk per kg of concentrate). Cows offered PB had increased N in milk compared with PO. In conclusion, concentrate supplementation based on barley or maize resulted in increased milk and milk solids yield compared with offering PO. Cows offered barley had a greater response to concentrates and increased milk and milk solids yield in comparison to maize and showed increased N partitioning in milk compared with PO. A barley-based concentrate increased total DMI compared with PO.

Livestock Performance for Sheep and Cattle Grazing Lowland Permanent Pasture: Benchmarking Potential of Forage-Based Systems

Here we describe the livestock performance and baseline productivity over a two-year period, following the establishment of the infrastructure on the North Wyke Farm Platform across its three farmlets (small farms). Lowland permanent pastures were continuously stocked with yearling beef cattle and ewes and their twin lambs for two years in three farmlets. The cattle came into the farmlets as suckler-reared weaned calves at 195 ± 32.6 days old weighing 309 ± 45.0 kg, were housed indoors for 170 days then turned out to graze weighing 391 ± 54.2 kg for 177 days. Therefore, it is suggested for predominantly grass-based systems with minimal supplementary feeding that target live weight gains should be 0.5 kg/day in the first winter, 0.9 kg/day for summer grazing and 0.8 kg/day for cattle housed and finished on silage in a second winter. The sheep performance suggested that lambs weaned at 100 days and weighing 35 kg should finish at 200 days weighing 44 to 45 kg live weight with a killing out percentage of 44%. Good levels of livestock production are possible with grass and forage-based systems using little or no additional supplementary concentrate feeds.

Case report

Risk factors and production losses are reported for an outbreak of bovine respiratory disease (BRD] in stocker cattle in a southeastern US grass-based system. Beef calves purchased from livestock auctions arrived in 2 groups 1 week apart (n=133 and 77, respectively]. Cattle were mass- medicated with antibiotics and vaccinated 3 days after arrival, then commingled on ryegrass pasture. A daily BRD score (0-4] based on presence and severity of clinical signs was used to determine antibiotic treatment eligibility over the 150-day stocker phase. BRD morbidity and mortality were 61.9% and 12.9%, respectively. Cattle in arrival group 2 had a greater incidence density of BRD (rate ratio = 1.54,95% Cl: 1.07,2.22]. Odds for death were 5.0 times greater for cattle in arrival group 2 (95% Cl: 2.0,12.2] and 42.5 times greater for cattle diagnosed with BRD (95% Cl: 2.5,713.2]. Average daily gain was decreased 0.15 lb/day (0.07 kg/day] in cattle with BRD. Including death loss, calves with BRD gained an average of 64.1 lb (29.1 kg] less than unaffected calves over the stocker phase. Despite metaphylaxis and prompt identification of sick cattle, this BRD outbreak resulted in high morbidity, mortality, and production loss in a stocker cattle system.

52 Evaluation of Production Economics and a Value of Carcasses Processed into Wholesale Cuts from Steers Finished in a Conventional System Compared to Carcasses Processed into Ground Beef from Steers Finished on a Grass-Based Systems.

52 Evaluation of Production Economics and a Value of Carcasses Processed into Wholesale Cuts from Steers Finished in a Conventional System Compared to Carcasses Processed into Ground Beef from Steers Finished on a Grass-Based Systems.

Growth, morphology and biological nitrogen fixation potential of perennial ryegrass-white clover swards throughout the grazing season

AbstractSustainable ruminant production systems depend on the ability of livestock to utilize increased quantities of grazed herbage. The current study aimed to compare the effect of white clover (WC) inclusion and perennial ryegrass (PRG) ploidy on herbage dry matter (DM) production, plant morphology, nutritive value and biological nitrogen (N) fixation (BNF) under high N fertilizer use (250 kg N/ha) and high stocking rates (2.75 livestock units/ha). Four sward treatments (diploid-only, tetraploid-only, diploid-WC, tetraploid-WC) were evaluated over a full grazing season at a farmlet scale. White clover inclusion had a significant effect on herbage DM production, herbage growth rate, tiller density, organic matter digestibility, crude protein and BNF. Tetraploid swards had a lower tiller density, lower sward WC content and post-grazing sward height and increased organic matter digestibility and crude protein than diploid swards. White clover inclusion improved herbage DM production and nutritive value across a full grazing season, with tetraploid and diploid swards producing similar herbage DM yields across the year. Perennial ryegrass ploidy had an effect on WC morphology as plants in diploid-WC swards had narrower, longer stolons, fewer branches and more petioles than tetraploid-WC swards. The current study highlights the benefit of including WC in grass-based systems under a high N fertilizer regime and high stocking rate.

Agroforestry for ruminants: a review of trees and shrubs as fodder in silvopastoral temperate and tropical production systems

Among the oldest agroforestry systems, silvopastoralism uses shrubs and trees to feed ruminants. The practice is common in extensive livestock production systems, whereas the intensification of grass-based systems in the past century has led to the removal of woody species from agricultural temperate landscapes. In Europe however, woody species are promoted again on grasslands through environment-friendly policies due to the ecosystem services they provide such as carbon sequestration, control of soil erosion, limitation of airborne pollutants and biodiversity conservation. Positive effects of browse on rumen digestion and parasite control have also been documented across different plant species and regions. Under optimal conditions, feeding ruminants from woody fodder sustains animal production. Nonetheless, limitations can restrict the use of woody forage into animal diets, such as the presence of anti-nutritive and toxic compounds. The incorporation of this resource in ruminant feeding systems raises the question of the management of the interface between the plant and the animal. Various management systems are practiced. Temperate species such as Salix spp. and Populus spp. are fed to sheep and cattle in fodder blocks or by pruning trees in New Zealand, and Fraxinus spp. or Corylus avellana in hedgerows supply forage to livestock in Belgium, whereas Leucaena leucocepahala and Desmanthus spp. browsing is common in Australia. Nowadays, ensiling and pelleting techniques are being developed as a way to store browse forage. As the renewed interest in using shrubs and trees to feed ruminants is recent, especially in temperate regions, additional research about the optimal introduction of this resource within systems is needed.

Measures of lamb production efficiency in a temperate grass-based system differing in ewe prolificacy potential and stocking rate.

The objective of this study was to quantify the effects of ewe prolificacy potential (PP; predicted number of lambs born ewe yr), as dictated by sire breed type, and stocking rate (SR; ewes ha) on ewe production efficiency (kg lamb live weight weaned:kg ewe live weight mated), lamb growth, lamb carcass output, and dry matter (DM; kg) and energy (UFL; unit of energy kg DM) consumption (in the form of both grazed and conserved herbage, concentrate supplementation, and total) in a temperate grass-based lamb production system. The study was a 2 × 3 factorial design, consisting of 2 differing ewe prolificacy potentials (medium prolificacy [MP]-Suffolk-sired crossbred ewes and high prolificacy [HP]-Belclare-sired crossbred ewes) and 3 stocking rates: low (LSR; 10 ewes ha), medium (MSR; 12 ewes ha), and high (HSR: 14 ewes ha). Each treatment was managed in a 5-paddock rotational system for the duration of the study. The HP treatment weaned more lambs ewe and ha ( < 0.01), yielded a higher average daily live weight gain (ADG) ha ( < 0.001), produced an additional 50 kg of lamb carcass ha ( < 0.05), and required 13% less DM and UFL to produce a kg of lamb carcass ( < 0.001) compared to the MP treatment. High prolificacy potential ewes had a 4% higher production efficiency ( < 0.05) than MP ewes. Ewe prolificacy potential had no effect on the total quantity of DM and UFL consumed ewe and lamb unit ( > 0.05). Increasing stocking rate increased the number of lambs weaned ha ( < 0.001) and increased lifetime lamb ADG ha ( < 0.001). Lamb carcass output (kg) ha was highest at the HSR, intermediate at the MSR, and lowest at the LSR ( < 0.001). The quantity of DM and UFL consumed ewe and lamb unit and kg of lamb carcass produced ha increased as stocking rate increased ( < 0.001). In conclusion, results from this study demonstrate HP ewes to be more efficient in the production of lamb. Increasing stocking rate provides the opportunity to increase lamb carcass output ha; however, achieving this increase in output required additional DM and UFL ewe and lamb unit above 12 ewes ha.

Environmental impacts of Italian beef production: A comparison between different systems

Livestock production, particularly beef supply chain, is charged as the major contributor to green-house gas (GHG) emissions, as well as, in land degradation and deforestation. Environmental impacts per kg of edible beef, however, vary largely due to differences in beef production systems. Thus, this study aimed to compare the cradle-to-farm gate sustainability of four different Italian beef production systems, in terms of land occupation (LO, m2/year), global warming (GWP, kg CO2 -eq), water depletion (WD, m3), acidification (AP, g SO2 -eq) and eutrophication (EP, g NO3 -eq) potentials by using the LCA methodology (SimaPro 8.01 PhD, PRé Consultants). The primary data were obtained from 25 farms: 7 farms conducting cow–calf operations, with specialized beef cattle maintained on pasture and finished in confinement, (Specialized extensive, SE); 6 farms conducting high grain fattening of specialized beef breed imported calves (Fattening systems, FS); 5 farms conducting cow-calf operations, with specialized beef animals constantly kept in confinement (Cow-calf intensive; CCI); 7 farms conducting cow–calf operations, with Podolian cattle (a native breed of Southern Italy) maintained on pasture and finished in confinement, (Podolian system; PoS). The functional unit was 1 kg of live weight of marketed beef cattle. Intensive systems (i.e. CCI and FS) showed lower GWP values than systems partially based on pasture such as PoS, and even SE (17.62 ± 1.78 and 21.94 ± 1.95 kg CO2 –eq vs 26.30 ± 1.65 and 25.41 ± 1.65 kg CO2 –eq, P < 0.01, for FS, CCI, SE, and PoS, respectively). No significant effect of production system on WD was observed. Acidification potential was significantly (P < 0.001) affected by production system with the highest values observed in CCI (0.30 ± 0.02 kg SO2 –eq) compared with the other three beef production systems. As for eutrophication potential, FS and PoS tended to show lower values compared with CCI and SE systems (961.71 ± 65.30 and 779.17 ± 70.53 g NO3 -eq vs 1009.20 ± 77.27 and 1009.71 ± 65.30 g NO3 –eq, respectively; P < 0.10). Significant differences (P < 0.001) were observed for LO between the four systems (177.71 ± 20.87 and 194.43 ± 20.87 m2/year vs 40.67 ± 22.54 and 32.60 ± 23.69 m2/year, for PoS and SE vs FS and CCI, respectively). However, as diets in intensive meat systems are mainly based on cereals products that humans could consume directly, the degree of competition with human nutrition should be another feature to be considered. About this aspect, although human edible protein conversion efficiency (HEPCE) was not significantly influenced by production system, PoS showed a higher HEPCE index (0.44 ± 0.08), particularly if compared with CCI system (0.17 ± 0.09), but also in comparison with groups FS and SE (0.34 ± 0.08 and 0.39 ± 0.08, respectively). In addition, grass-based systems may provide other non-commodity outputs and non-marketable public goods services named “ecosystem services” (e.g. provision of clean drinking water, preservation and enhancement of biodiversity, conservation of cultural landscapes, contribution to the socio-economic viability of many rural areas particularly in marginal areas, enhancement of meat quality and animal welfare as perceived by consumers). The present results showed a lower impact of the intensive beef production systems in terms of GWP and LO, whereas some of them were more impactful at AP and EP levels. However, in order to achieve a more accurate estimation of the impact of the beef production chain, particularly for traditional and extensive farming systems conducted in marginal areas, such as the Podolian system, further LCA studies are needed, taking into account the allocation of their ecosystem services.

Effect of ewe prolificacy potential and stocking rate on ewe and lamb performance in a grass-based lamb production system

Effect of ewe prolificacy potential and stocking rate on ewe and lamb performance in a grass-based lamb production system

Measures of lamb production efficiency in a temperate grass-based system differing in ewe prolificacy potential and stocking rate

Measures of lamb production efficiency in a temperate grass-based system differing in ewe prolificacy potential and stocking rate

Economic and environmental implications of wheat-crop sequences on organic dairy-farm simulations

The market for high-quality organic bread wheat (Triticum aestivum L.) is increasing in New England, USA, providing opportunities for organic dairy farmers to grow this alternative cash crop. Our objective was to determine the sustainability of eight 3-year crop sequences compared with a perennial forage baseline in long-term (25-year), well-managed, medium-sized organic dairy farm simulations. Systems included wheat (spring or winter) preceded by maize (Zea mays L.) silage, a 1-year-old perennial forage grass, or soybean as well as maize silage followed by maize silage or soybean. Farm net return was highest for the entirely grass-based system (US$742.15 cow–1). Higher winter wheat yields for soybean–wheat–grass resulted in 7% more income from feed sales ($1027) than spring wheat. Soybean followed by wheat reduced soil nutrient accumulation by 0.8 kg ha–1 year–1 for phosphorus runoff and leachate losses and for potassium accumulation (–17%); there was also a 4% reduction in water footprint (kg kg–1 fat- and protein-corrected milk). Growing winter wheat provides long-term environmental and economic benefits, although for spring wheat, much of this benefit is lost. Use of maize silage in place of grass, winter or spring wheat, or soybean was less profitable. Most cropping system scenarios were less economically favourable than producing and feeding exclusively grass silage. However, inclusion of soybean increased economic benefits.

The effect of stocking rate on soil solution nitrate concentrations beneath a free-draining dairy production system in Ireland

Economically viable and productive farming systems are required to meet the growing worldwide need for agricultural produce while at the same time reducing environmental impact. Within grazing systems of animal production, increasing concern exists as to the effect of intensive farming on potential N losses to ground and surface waters, which demands an appraisal of N flows within complete grass-based dairy farming systems. A 3-yr (2011 to 2013) whole-farm system study was conducted on a free-draining soil type that is highly susceptible to N loss under temperate maritime conditions. Soil solution concentrations of N from 3 spring-calving, grass-based systems designed to represent 3 alternative whole-farm stocking rate (SR) treatments in a post-milk quota situation in the European Union were compared: low (2.51 cows/ha), medium (2.92 cows/ha), and high SR (3.28 cows/ha). Each SR had its own farmlet containing 18 paddocks and 23 cows. Nitrogen loss from each treatment was measured using ceramic cups installed to a depth of 1m to sample the soil water. The annual and monthly average nitrate, nitrite, ammonia, and total N concentrations in soil solution collected were analyzed for each year using a repeated measures analysis. Subsequently, and based on the biological data collated from each farm system treatment within each year, the efficiency of N use was evaluated using an N balance model. Based on similar N inputs, increasing SR resulted in increased grazing efficiency and milk production per hectare. Stocking rate had no significant effect on soil solution concentrations of nitrate, nitrite, ammonia, or total N (26.0, 0.2, 2.4, and 32.3mg/L, respectively). An N balance model evaluation of each treatment incorporating input and output data indicated that the increased grass utilization and milk production per hectare at higher SR resulted in a reduction in N surplus and increased N use efficiency. The results highlight the possibility for the sustainable intensification of grass-based dairy systems and suggest that, at the same level of N inputs, increasing SR has little effect on N loss in pastoral systems with limited imported feed. These results suggest that greater emphasis should be attributed to increased grass production and utilization under grazing to further improve the environmental impact of grazing systems.

Ohio Livestock Producers’ Perceptions of Producing and Marketing Grass-Based Beef and Lamb

Although small and mid-size cattle and sheep producers may be positioned to meet local market demand for grass-based meat and meat products, they share similar challenges as they consider converting to grass-based systems. A survey of Ohio beef and sheep producers reveals a number of underlying factors that influence the decision to convert a livestock management system to a grass-base including available infrastructure, knowledge and technical skills, financial costs and a desire to change their system. These findings demonstrate that there are substantive production and marketing issues that influence producer decisions to change an existing management system. A better understanding of the livestock production system and direct marketing opportunities can improve local food programs’ capacity to increase the supply of grass-based meat and meat products.

A case study of the carbon footprint of milk from high-performing confinement and grass-based dairy farms

Life-cycle assessment (LCA) is the preferred methodology to assess carbon footprint per unit of milk. The objective of this case study was to apply an LCA method to compare carbon footprints of high-performance confinement and grass-based dairy farms. Physical performance data from research herds were used to quantify carbon footprints of a high-performance Irish grass-based dairy system and a top-performing United Kingdom (UK) confinement dairy system. For the US confinement dairy system, data from the top 5% of herds of a national database were used. Life-cycle assessment was applied using the same dairy farm greenhouse gas (GHG) model for all dairy systems. The model estimated all on- and off-farm GHG sources associated with dairy production until milk is sold from the farm in kilograms of carbon dioxide equivalents (CO2-eq) and allocated emissions between milk and meat. The carbon footprint of milk was calculated by expressing GHG emissions attributed to milk per tonne of energy-corrected milk (ECM). The comparison showed that when GHG emissions were only attributed to milk, the carbon footprint of milk from the Irish grass-based system (837kg of CO2-eq/t of ECM) was 5% lower than the UK confinement system (884kg of CO2-eq/t of ECM) and 7% lower than the US confinement system (898kg of CO2-eq/t of ECM). However, without grassland carbon sequestration, the grass-based and confinement dairy systems had similar carbon footprints per tonne of ECM. Emission algorithms and allocation of GHG emissions between milk and meat also affected the relative difference and order of dairy system carbon footprints. For instance, depending on the method chosen to allocate emissions between milk and meat, the relative difference between the carbon footprints of grass-based and confinement dairy systems varied by 3 to 22%. This indicates that further harmonization of several aspects of the LCA methodology is required to compare carbon footprints of contrasting dairy systems. In comparison to recent reports that assess the carbon footprint of milk from average Irish, UK, and US dairy systems, this case study indicates that top-performing herds of the respective nations have carbon footprints 27 to 32% lower than average dairy systems. Although differences between studies are partly explained by methodological inconsistency, the comparison suggests that potential exists to reduce the carbon footprint of milk in each of the nations by implementing practices that improve productivity.

Embedded risk management in dryland sheep systems II. Risk analysis

Climatic variability is a major constraint to improved productivity and profitability in dryland grazing systems. This paper reports the physical and economic benefits obtained from incorporating tactical responses in risk management strategies for dryland sheep production systems constrained by climatic variability. A total of 112 potential risk management strategy:response combinations were evaluated using the simulation model LincFarm. The strategies differed in stocking rate (SR; stock units (SU) ha−1), pasture type (legume or grass-based system), and stock classes. All strategies were evaluated at 10, 12, 14 or 16 SR, first without tactical responses and then with responses triggered when soil moisture levels fell to 10.0%, 12.5% or 15.0% in the top 25cm soil. The results show that all strategies including tactical adjustments to management and marketing were economically superior to those that did not vary tactically. The difference in average returns between the best strategy with tactical responses and the best without is $336.04ha−1 year−1, an increase of 40%. The value of including tactical responses in corresponding strategies ranged between 2.98% and 37.32%. This was in addition to tactical responses decreasing the variability of returns by between 19.74% and 67.38%. The combination of risk and return defines a risk-efficient frontier on which any individual farmer should find an optimal strategy which reflects their risk attitude. By including tactical adjustments additional strategies become risk-efficient and the number on the frontier increased from 5 to 11. Comparing the two sets of strategies showed that failure to incorporate tactical adjustments may result in sub-optimal risk management strategies being chosen whereas failure to accommodate risk attitude may change the strategy chosen, but not necessarily to one that is sub-optimal. The results suggest conventional ryegrass:clover pastures are risk efficient when management is aggressive (high stocking rate and later climate response) and that either conventional pasture systems or those with high nutritive value species are superior when management is more conservative. In all cases, retaining a proportion of flexible stock classes such as 2year old cattle or a mob of older ewes is essential. The results also emphasise the importance of maintaining high pasture quality to ensure fast lamb growth rates and early drafting.

Making sense of methods to audit emissions – various audit methods to estimate dairy production carbon footprint

A dairy farm greenhouse gas (GHG) model was applied in this study to compare the Intergovernmental Panel on Climate Change (IPCC) method and the life cycle assessment (LCA) procedure, which are the principal methods for quantifying the carbon footprint of dairy production. The objectives of this paper were to compare the auditing methods in estimating the carbon footprint of grass and confinement dairy systems and to assess the methods in estimating the footprint of grass-based dairy farms varying in cow genetic potential, stocking rate and level of concentrate feeding. The input data used to operate the model was based on published research studies. The results of the study showed that the IPCC and LCA methods ranked the carbon footprint of dairy systems differently. For example, the IPCC method found that the carbon footprint of the confinement dairy system was 8% lower than the grass system, but the LCA results show that the confinement system increased the carbon footprint by 16%. The comparison of grass-based dairy systems, differing in cow genotype, stocking rate and concentrate fed per cow also showed that the methods did not agree on the ranking of dairy systems carbon footprint. The re-ranking of dairy systems carbon footprint occurred because the IPCC method excludes emissions associated with imported goods, for example, concentrate. Thus, it is incorrect to consider only components of the dairy system relevant for policy reporting such as that used by IPCC when estimating the carbon footprint of dairy produce. Instead, holistic approaches, such as LCA, which consider on and off-farm GHG emissions should be used. Therefore, reform of the present policy framework is required to enable quantification of the impact of mitigation strategies on global emissions. The evaluation of the carbon footprint from grass-based systems differing in cow genotype also demonstrated that selecting cows solely for milk production will increase the carbon footprint of grass-based dairy systems relative to cows selected on a combination of traits, because of reduced cow fertility and thus higher emissions from replacement heifers.

Direct and carryover effect of post-grazing sward height on total lactation dairy cow performance

Grazing pastures to low post-grazing sward heights (PGSH) is a strategy to maximise the quantity of grazed grass in the diet of dairy cows within temperate grass-based systems. Within Irish spring-calving systems, it was hypothesised that grazing swards to very low PGSH would increase herbage availability during early lactation but would reduce dairy cow performance, the effect of which would persist in subsequent lactation performance when compared with cows grazing to a higher PGSH. Seventy-two Holstein–Friesian dairy cows (mean calving date, 12 February) were randomly assigned post-calving across two PGSH treatments (n = 36): 2.7 cm (severe; S1) and 3.5 cm (moderate; M1), which were applied from 10 February to 18 April (period 1; P1). This was followed by a carryover period (period 2; P2) during which cows were randomly reassigned within their P1 treatment across two further PGSH (n = 18): 3.5 cm (severe, SS and MS) and 4.5 cm (moderate, SM and MM) until 30 October. Decreasing PGSH from 3.5 to 2.7 cm significantly decreased milk (−2.3 kg/cow per day), protein (−95 g/day), fat (−143 g/day) and lactose (−109 g/day) yields, milk protein (−1.2 g/kg) and fat (−2.2 g/kg) concentrations and grass dry matter intake (GDMI; −1.7 kg dry matter/cow per day). The severe PGSH was associated with a lower bodyweight (BW) at the end of P1. There was no carryover effect of P1 PGSH on subsequent milk or milk solids yields in P2, but PGSH had a significant carryover effect on milk fat and lactose concentrations. Animals severely restricted at pasture in early spring had a higher BW and slightly higher body condition score in later lactation when compared with M1 animals. During P2, increasing PGSH from 3.5 to 4.5 cm increased milk and milk solids yield as a result of greater GDMI and resulted in higher mean BW and end BW. This study indicates that following a 10-week period of feed restriction, subsequent dairy cow cumulative milk production is unaffected. However, the substantial loss in milk solid yield that occurred during the period of restriction is not recovered.

The effect of grazing season length on nitrogen utilization efficiency and nitrogen balance in spring-calving dairy production systems

SUMMARYThere is a continual requirement for grass-based production systems to optimize economic and environmental sustainability through increased efficiency in the use of all inputs, especially nitrogen (N). An N balance model was used to assess N use efficiency and N surplus, and to predict N losses from grass-based dairy production systems differing in the length of the grazing season (GS). Data from a 3-year grazing study with a 3×3 factorial design, with three turnout dates (1 February, 21 February and 15 March) and three housing dates (25 October, 10 November and 25 November) were used to generate estimates of N use efficiency and N losses. As the length of the GS increased by a mean of 30 days, milk production, milk solids production and milk N output increased by 3, 6 and 6%, respectively. The increase in milk production as the length of the GS increased resulted in a 2% decline in N surplus and a 5% increase in N use efficiency. Increasing GS length increased the proportion of grazed grass in the diet, which increased N cycling within the system, resulting in an 8% increase in milk solids/ha produced/kg of surplus N. The increased cycling of N reduced the quantity of N partitioned for loss to the environment by 8%. Reducing fertilizer N input by 20% increased N use efficiency by 22% and reduced total N losses by 16%. The environmental and production consequences of increased length of the GS and reduced N loss are favourable as the costs associated with N inputs increase.