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This perspective paper provides industry leaders, researchers and policy developers strategic approaches to ensure that the welfare of dairy cattle is protected at the same time as the industry increases its resilience to climate change. Farm systems and practices will evolve in response to the direct impacts of climate change and/or from responses to climate change, such as mitigation strategies to reduce dairy's greenhouse-gas (GHG) emissions. The five domains framework (nutrition, physical environment, health, behaviour, mental state) was used to assess the potential impacts on animal welfare and strategies to minimise these impacts are outlined. Given that the future climate cannot be certain these approaches can be applied under a range of emissions pathways to (1) ensure that the effects of GHG mitigations on animal welfare are considered during their development, (2) engage with end users and the public to ensure solutions to the effects of climate change and weather variability are accepted by consumers and communities, (3) identify and measure the areas where improved animal health can contribute to reducing GHG emissions from dairy production, (4) ensure those supporting farmers to develop and manage their farm systems understand what constitutes a good quality of life for dairy cattle, (5) ensure effective surveillance of animal disease and monitoring of welfare outcomes and farm-system performance in response to climate change and GHG mitigations. Overall, these strategies require a multidisciplinary co-development approach to ensure that the welfare of dairy cattle is protected at the same time as the industry increases its resilience to the wider impacts of a changing climate. [ABSTRACT FROM AUTHOR]

Future development pathways for irrigated dairy farms in Canterbury operating under stricter nitrogen (N) loss limits were compared in two farmlets over four years. One represented the traditional pathway of intensification via higher inputs of N fertiliser and supplementary feed ('higher input-high efficiency', HI-HE), while the other represented a lower input pathway using half the amount of N fertiliser and one quarter the amount of supplementary feed ('lower input-high efficiency', LI-HE). The stocking rate of both systems was matched to feed supply to achieve high utilisation (∼90%) of the pasture grown. Mean total annual N surplus and estimated nitrate-N leaching were lower in LI-HE than HI-HE, by 46% and 25% respectively. Milk production was lower for LI-HE (1,700 kg versus 2,240 kg milk fat + protein per ha/year). Estimated profit was the same for both systems at a milk price of $6.46/kg fat + protein, below which LI-HE was more profitable than HI-HE and vice-versa. Compared with the benchmark high-performing Lincoln University Demonstration Dairy Farm (LUDF) through the same period, LI-HE was 2% less profitable, but estimated N leaching was ∼30% lower. Subsequent adoption of the LI-HE system by LUDF demonstrated that the system is scalable, and profitable. [ABSTRACT FROM AUTHOR]

A short-term, dairy cow, grazing experiment was conducted in late-lactation (autumn) to determine the effect of fodder beet (FB) and maize silage supplementation on dry matter and nitrogen (N) intake, urinary N excretion and milk solids (MS; milk fat + milk protein) production. Seventy-two multiparous, lactating (224 ± 20.0 DIM; mean ± SD) Holstein-Friesian cows were randomly assigned (n = 24 per treatment; 8 per replicate) to one of three groups. Control animals were offered pasture (11 kg DM/cow/day) with maize silage (4 kg DM/cow/day; 'Maize'). The other two groups were either offered pasture (11 kg DM/cow/day) with 25% FB (4 kg DM/cow/day; 'FB25') or pasture (9 kg DM/cow/day) with 40% FB (6 kg DM/cow/day; 'FB40'). At the same supplement DM intake, diets containing maize silage or grazed FB had similar urinary nitrogen (UN) concentrations, but FB increased milk solids (MS) production. At 40% FB inclusion UN excretion was reduced but this came at the expense of MS production. Farmers need to exhibit caution when feeding fodder beet to lactating dairy cows to minimise the risk of adverse animal health effects. Feeding fodder beet allocations high enough to achieve significant environmental benefit is likely to compromise animal health and milk production. [ABSTRACT FROM AUTHOR]

Autumn grazing of high-yielding forage crops such as fodder beet (FB) has increased in popularity in many regions of New Zealand. During grazing, large amounts of urinary nitrogen (N) is returned to the soil which is at risk of leaching. This study evaluated using two different catch crops of oats or Italian ryegrass ('Italian RG') to reduce the risk of N leaching both after FB grazing by lactating dairy cows and after lifting (i.e. un-grazed FB) in autumn. During FB grazing, cows grazed either (i) high [40% of diet dry matter (DM), with pasture; FB40] or (ii) low (25% of diet DM, with pasture; FB25) FB allocations. Both Italian RG and oats reduced soil mineral N (0–90 cm depth) by 16%–37% by August, and 53%–58% by October, compared with a fallow control (115 and 100 kg N ha−1 for August and October, respectively). The greatest reductions in soil mineral N were from oats, largely attributed to higher DM yields resulting in greater N uptake. Furthermore, the total amounts of soil mineral N in the soil after grazing differed between FB allocation treatments and lifted FB (FB25 > FB40 > lifted FB), in proportion to urinary-N inputs and associated dietary N intake. [ABSTRACT FROM AUTHOR]

Two short-term dairy cow grazing experiments in mid-lactation (late spring) and late-lactation (late summer), were conducted in the Waikato region of New Zealand, to determine the effect of pasture species mixtures on urinary nitrogen (N) concentration and milk solids production. The mixtures included perennial ryegrass, tall fescue, lucerne and narrow-leaved plantain (cv. Tonic), structured to compare the two grass species, both with and without plantain. With plantain, apparent intake of plantain was 46%–70% of dry matter intake and estimated water intake was increased by 8%–21% over grass-lucerne swards. This led to significantly lower N concentrations of spot-sampled urine, by 38% in summer and 21% in spring, but no difference in milk production. A decline in apparent N intake was also implicated in summer. The effect of relatively high levels of plantain intake on reducing urinary N concentration is likely to be positive for reducing N leaching risk, particularly in late-lactation. [ABSTRACT FROM AUTHOR]

Nitrate leaching from soil is a major problem in New Zealand pastoral systems, requiring development of practical methods to manage accumulation of nitrates. Nine feed trials were carried out in the Waikato (n = 3) and in Canterbury (n = 6) between 2013 and 2016; from which 424 samples were selected for forage quality testing. Only tick beans and forage rape met the lactating feed criteria for adequate crude protein (CP; > 16% DM) and soluble sugars and starch (SSS; > 25% DM). When an 'environmental' criterion was added to a feed value for lactating cows this reduced the options to fodder beet only. However, the CP measurements for fodder beet were suboptimal for milk production, requiring the fodder beet to be mixed with high protein feeds such as pasture or pasture silage. The lower protein requirements for non-lactating cows, including an additive environmental criterion enabled a wider range of feeds to be considered e.g. kale, sunflowers and swedes in Canterbury (12 entries) and fodder beet and rape in the Waikato (21 entries). Addition or restriction of nitrogen fertiliser was the only agronomic management intervention that consistently altered animal feed quality and potentially changed N excretion. Crop choice was likely to have the greatest impact at the farm level. By limiting feed quality assessment to CP, SSS and their ratio (SSS:CP) we were able to define a selection/feed monitoring method to minimise N content of feed, maximise SSS feed value and limit excess N intake to reduce the nitrate leaching risk. [ABSTRACT FROM AUTHOR]

Forages and forage mixtures with greater tolerance of dry conditions than perennial ryegrass (Lolium perenne L.) are desirable for dairy farming in New Zealand, and a low urinary nitrogen (N) excretion is desirable to lessen pollution of waterways and ground water, and nitrous oxide emissions. Measurements were undertaken with late-lactation Holstein-Friesian cows (5/treatment) fed tall fescue (Festuca arundinacea Schreb.) with a substantial incursion of weed grasses, as either a sole diet (Grass), or with lucerne (Medicago sativa L.) or lucerne and plantain (Plantago lancelota L.), in metabolism stalls. Approximate ratios (DM basis) of Grass with lucerne (GL) were 55 : 45, and Grass with lucerne and plantain (GLP) were 55 : 25 : 20. Measurements included intakes, production, digestion, rumen function, and urinary excretion, including the circadian patterns of metabolite excretion with a focus on nitrogenous aspects. The DM intakes (kg/day) of cows fed Grass, GL and GLP were 14.9, 12.7 and 15.0 (P = 0.006), and DM digestibility (%) was 58.0, 59.8 and 61.9 (P = 0.006), respectively. Milk yields (kg/day) were Grass, 9.0; GL, 8.7 and GLP, 11.7 (P = 0.003) but composition was not affected by diet. Rumen digesta weight was greatest in cows fed Grass, averaging 23.4% of liveweight after morning feeding. The microbial growth (g/kg organic matter digested) was 16.8 in cows fed Grass and ~24.0 in the other diets. Dietary crude protein concentrations (g/100 g DM) were Grass, 15.4, GL, 20.1 and GLP, 18.3 and urinary N excretion (g/day) was lowest with the Grass diet but urinary N concentration was lowest from cows fed GLP. Daily creatinine excretion was unaffected by diet but there was a 2-fold range in excretion rates within 24 h and values from cows fed fresh forages are lower than published values from cows fed dry diets. Results showed that supplementation of poor quality pasture with lucerne or lucerne with plantain had minor effects on digestibility, and measurements of urinary N suggest a need for caution when predicting urinary N excretion from spot urine sampling in grazing trials. Farmers need forages that are tolerant of dry conditions, so fescue grass was fed to dairy cows as a sole diet, and with either lucerne or lucerne and plantain. The best combination was fescue with lucerne and plantain because digestibility and production were highest and the urine nitrogen concentration was lowest. This combination of three forages will enable dairy production in dry conditions with less urinary nitrogen pollution than feeding fescue alone or with lucerne. [ABSTRACT FROM AUTHOR]

Dairy cow effluent collected over winter from a loose-housed barn was applied to a series of large infield plots (400 m2) using low rate and low depth (LRLD) application methods. Applications were confined to the winter period, at a time when soil moisture content was often at or very near to field capacity and was applied over two seasons. Cows were confined to the housing facility during winter only, and outside of this period they remained on pasture. Losses of nitrogen (N), phosphorus (P) and the faecal indicator bacteriumEscherichia coli(E. coli) in surface runoff and subsurface drainage from the LRLD treatment were compared with losses from effluent applications that occurred during spring to autumn, at an application depth not exceeding the soil water deficit, i.e. a standard practice treatment (SP, typically 10–15 mm per application). The annual quantities of nutrients applied by the treatments and the grazing managements imposed were similar. Although winter losses of N were significantly greater for the LRLD treatment (15 vs. 8 kg N ha−1for the SP treatment), on an annual basis fluxes were similar between treatments (approximately 20 kg N ha−1year−1). Effluent management had no significant effect on the annual fluxes of P andE. colialthough the latter varied considerably. Average contaminant fluxes over a 2-year period indicated that the LRLD management system did not lead to a significantly greater risk to water quality compared with standard practices. [ABSTRACT FROM PUBLISHER]

The New Zealand Government’s National Policy Statement on Fresh Water Management has resulted in increased scrutiny of New Zealand grazing systems with regards to their environmental impact. With this has been greater interest in nitrogen (N) loss mitigation options, including identifying crops with high nutritive value but low protein content. New Zealand data have been collated with key data fields: publication, experiment, site and, crop details and chemical analysis. This paper discusses these data with respect to the range of nutritive values observed in these New Zealand crops and feed supplements, including the implications for reducing N leaching risk. Feeds most likely to result in less urinary nitrogen (UN) excretion, and thus less nitrate (NO3−) leaching, include fodder beet, swedes, turnips, barley and wheat grain. The high soluble sugar and starch content of these feeds will support high animal production but may increase the risk of nutritional disorders. [ABSTRACT FROM PUBLISHER]

Farm-scale models were integrated with spatially discrete estimates of pasture production to examine the potential farm and regional implications of removing palm-kernel expeller (PKE) as a supplementary feed from dairy farms in Southland, New Zealand. The following two farm-production systems representing the majority of dairy farms in the region were modelled: a System 3 farm (D3; mid-intensification, with 10-20% of imported feed) and a System 4 farm (D4; mid- to high intensification, with 20-30% of imported feed). Within each system, the impact of the following four PKE options was explored: (1) a control with PKE (Baseline); (2) no PKE, with fewer cows producing the same amount of milk per cow as in Baseline; (3) no PKE, with the same number of cows producing less milk per cow than in Baseline; and (4) PKE replaced with barley grain. Barley grain provides for similar flexibility (timing of purchase and feeding), and can be sourced locally. Faced with the need to remove PKE as a dietary ingredient, farmers would benefit from adopting the second PKE option (no PKE, with fewer cows producing the same amount of milk per cow as in Baseline); farm-operating profits were reduced by only 3% (compared with 30% of System 4 farms adopting the third PKE option, i.e. no PKE, with the same number of cows producing less milk per cow than in Baseline) relative to the Baseline farms. The narrow range of mean annual nitrate-nitrogen (nitrate-N) leaching losses (estimates ranged from 30 to 33 kg N/ha) reflects similar estimates of N intake and N excreted in urine across the modelled options. Substantial amounts of barley grain would need to be transported into the region or produced locally to replace PKE. [ABSTRACT FROM AUTHOR]

Dairy cows are motivated to access dry lying surfaces and will seek protection from wind and rain, but winter conditions may limit these opportunities when cows are managed outdoors. The primary aim of this observational study was to determine the effects of weather and paddock soil conditions on lying behavior of dairy cows managed outdoors during winter and fed crop in situ, a practice occurring in New Zealand with year-round grazing of dairy cows. A secondary aim was to characterize eating and ruminating behaviors during winter weather and paddock soil conditions. Four groups (99 nonlactating, pregnant cows each) were managed on 4 outdoor paddock areas on the same farm; the groups were fed pasture silage and grazed either kale (2 groups) or fodder beet (2 groups). Behaviors were recorded using validated leg-based (lying behavior) and ear-based (eating and ruminating time) accelerometers on 30 focal cows in each group over 32 d. Soil depth and wetness were scored daily at 25 points along 4 transects within each paddock area using recognized technical measures (penetrometer, soil volumetric water content), which were compared with practical tools for farmer use (ruler, moisture meter, percentage of sites in paddock scored as dry, wet, sodden, or with surface water pooling). Rainfall occurred most days during the study (mean 1.6 mm/d; maximum 12.2 mm/d), resulting in wet and muddy paddocks (mud depth with ruler: mean 6 cm, maximum 18 cm; paddock sites scored as wet or sodden: mean 34%, maximum 100%; paddock sites with surface water pooling: mean 27%, maximum 100%). Group lying time was 9.6 ± 2.3 h/d (mean ± standard deviation); however, 21% of cows consistently lay less than 8 h/d (to a minimum of 4.9 h/d). A mixed regression model tested the effects of daily weather and paddock soil conditions on daily lying time, with group as the observational unit, day as repeated measure, crop type as a fixed effect, crop type interactions with explanatory variables, and random intercepts of group and paddock within group. Lying time was less on the day of and day after rainfall (24 and 29 min/d less for 1 mm increase in rainfall, respectively). Two days after rainfall, lying time rebounded to about 1 h longer than before the rainfall. On the day after the heaviest rainfall event, group average lying time was only 2.5 ± 1.9 h/d (mean ± standard deviation); in 2 groups, 30% and 38% of cows, respectively, did not lie down at all for 24 h. Lying time decreased with deteriorating paddock soil conditions, especially with increasing surface water pooling, suggesting that this may be a useful measure to estimate the quality of the lying surface. Descriptively, ruminating time appeared to decrease with increased surface water pooling, possibly due to decreased lying time. Our results demonstrated that dairy cows could experience periods of short or no lying time during inclement weather and muddy paddock soil conditions. Prior rainfall and surface water pooling may be useful measures to determine if lying time, and thus animal welfare, are compromised. [ABSTRACT FROM AUTHOR]

High yielding crops such as maize (Zea mays L.) and fodder beet (FB; Beta vulgaris L), are commonly used to extend lactation and increase animal productivity from pastoral dairy systems. Financial modelling to compare costs and benefits of different crops is useful for decision making, but such modelling often fails to account for potential animal health risks which can be associated with feeding supplements. A multi-component, whole-farm modelling approach was used to predict milk solids (MS, milk fat + protein) production and the economic farm surplus (EFS: operating surplus – adjustments) between 2016 and 2018 for an irrigated farm in Canterbury (South Island) and a non-irrigated farm in the Waikato (North Island), of New Zealand. The financial risk of the dairy business was measured using the ratio between mean return on assets (ROA) minus an assumed 5% risk-free ROA, and the standard deviation of ROA was calculated from 300 combinations of climate, milk, and feed price, land appreciation, and interest rate. Four scenarios of autumn and spring supplementation of pasture were considered at each geographical location; imported maize silage (Base), a crop of maize silage grown on the milking platform (MSC; area used to produce milk), a crop of FB grown on the milking platform (FBC), and a FB crop with an outbreak of acute (1% stock fatality) and subacute ruminal acidosis (5% decline of feed intake) across the entire herd (FBAC). The MSC scenario improved EFS by 5.8% compared with Base in both the irrigated and the dryland system. The predicted response to MSC reflected greater milk production, lower feed expenses, and shorter crop rotation, compared with either Base, FBC, or FBAC. While FBC increased EFS by 4.8% compared with Base under irrigation, EFS was similar to Base under dryland conditions ($2711 and $2759/ha, respectively). The limited advantage of growing FB under dryland conditions reflect reduced herbage supply due to the extended crop duration of FB compared with maize silage. Model predictions suggest that FBAC will increase the financial risk by reducing milk production and EFS by 6.5% (irrigated) and 7.1% (dryland) compared with Base. In the absence of any adverse health risks, farm performance from the FBC scenario was comparable to that of MSC under irrigated conditions. However, in dryland conditions, and when the potential economic cost of acute and sub-acute ruminal acidosis is considered, there is little advantage to growing FB on the milking platform. • There is limited economic advantage to growing fodder beet to support lactation. • Risk exposure to fodder beet crop increased under dryland conditions. • System response to crop inclusion is dependent on commodities market and climate. • Profitability of fodder beet crop was reduced by ruminal acidosis. • Maize silage lowers cow health risk and is a competitive alternative to fodder beet. [ABSTRACT FROM AUTHOR]

Simple Summary: Reducing inputs of nitrogen fertiliser and purchased feed, with an associated reduction in stocking rate on pastoral dairy farms resulted in less nitrate leaching. A co-benefit was a reduction in greenhouse gas emissions. The exception was the implementation of a wintering barn where nitrate leaching was reduced, but greenhouse gas emissions remained unchanged due to greater manure storage and handling. Emission reductions in the lower-input systems came at an average loss of profit of approximately NZ$100 per tonne CO2-equivalent. Between 2011 and 2016, small-scale farm trials were run across three dairy regions of New Zealand (Waikato, Canterbury, Otago) to compare the performance of typical regional farm systems with farm systems implementing a combination of mitigation options most suitable to the region. The trials ran for at least three consecutive years with detailed recording of milk production and input costs. Nitrate leaching per hectare of the milking platform (where lactating cows are kept) was estimated using either measurements (suction cups), models, or soil mineral nitrogen measurements. Post-trial, detailed farm information was used in the New Zealand greenhouse gas inventory methodology to calculate the emissions from all sources; dairy platform, dairy support land used for wintering non-lactating cows (where applicable) and replacement stock, and imported supplements. Nitrate leaching was also estimated for the support land and growing of supplements imported from off-farm using the same methods as for the platform. Operating profit (NZ$/ha/year), nitrate leaching (kg N/ha/year), and greenhouse gas emissions (t CO2-equivalent/ha/year) were all expressed per hectare of milking platform to enable comparisons across regions. Nitrate leaching mitigations adopted in lower-input (less purchased feed and nitrogen fertiliser) farm systems reduced leaching by 22 to 30 per cent, and greenhouse gas emissions by between nine and 24 per cent. The exception was the wintering barn system in Otago, where nitrate leaching was reduced by 45 per cent, but greenhouse gas emissions were unchanged due to greater manure storage and handling. Important drivers of a lower environmental footprint are reducing nitrogen fertiliser and purchased feed. Their effect is to reduce feed flow through the herd and drive down both greenhouse gas emissions and nitrate leaching. Emission reductions in the lower-input systems of Waikato and Canterbury came at an average loss of profit of approximately NZ$100/t CO2-equivalent (three to five per cent of industry-average profit per hectare). [ABSTRACT FROM AUTHOR]

Simple Summary: Dairy farm system practices aimed at reducing nitrate leaching can also reduce emissions of the greenhouse gases methane and nitrous oxide. A study comparing 'current' and 'improved' grazed dairy system practices showed that 'improved' systems generally produced lower greenhouse gas emissions while milk production was maintained. The amount of feed eaten per hectare was the key driver of total greenhouse gas emissions per area, with 'improved' systems generally exhibiting lower total enteric methane and less N flowing through the herd. An important challenge facing the New Zealand (NZ) dairy industry is development of production systems that can maintain or increase production and profitability, while reducing impacts on receiving environments including water and air. Using research 'farmlets' in Waikato, Canterbury, and Otago (32–200 animals per herd), we assessed if system changes aimed at reducing nitrate leaching can also reduce total greenhouse gas (GHG) emissions (methane and nitrous oxide) and emissions intensity (kg GHG per unit of product) by comparing current and potential 'improved' dairy systems. Annual average GHG emissions for each system were estimated for three or four years using calculations based on the New Zealand Agricultural Inventory Methodology, but included key farmlet-specific emission factors determined from regional experiments. Total annual GHG footprints ranged between 10,800 kg and 20,600 kg CO2e/ha, with emissions strongly related to the amount of feed eaten. Methane (CH4) represented 75% to 84% of the total GHG footprint across all modelled systems, with enteric CH4 from lactating cows grazing pasture being the major source. Excreta deposition onto paddocks was the largest source of nitrous oxide (N2O) emissions, representing 7–12% of the total GHG footprint for all systems. When total emissions were represented on an intensity basis, 'improved' systems are predicted to generally result in lower emissions intensity. The 'improved' systems had lower GHG footprints than the 'current' system, except for one of the 'improved' systems in Canterbury, which had a higher stocking rate. The lower feed supplies and associated lower stocking rates of the 'improved' systems were the key drivers of lower total GHG emissions in all three regions. 'Improved' systems designed to reduced N leaching generally also reduced GHG emissions. [ABSTRACT FROM AUTHOR]

Farmers face complex decisions at the time to feed animals, trying to achieve production goals while contemplating social and environmental constraints. Our purpose was to facilitate such decision making for pastoral dairy farmers, aiming to reduce urinary N (UN) and methane emissions (CH 4 ), while maintaining or increasing milk production (MP). There is a number of feeds the farmers can choose from and combine. We used 50 feeds (forages and grains) combined systematically in different proportions producing 11,526 binary diets. Diets were screened, using an a posteriori approach and a Pareto front (PF) analysis of model (Molly) outputs. The objective was to identify combinations with the best possible compromise (i.e. frontier) between UN, CH 4 , and MP. Using high MP and low UN as objective functions, PF included 10, 14, 12 and 50 diets, for non-lactating, early-, mid- and late-lactation periods, with cereals and beets featuring strongly. Using the same objective functions, but including ryegrass as dietary base PF included 2, 4, 8 and 4 diets for those periods. Therefore, from a wide range of diets, farmers could choose from few feeds combined into binary diets to reduce UN while maintaining or increasing MP. If the intention is maintaining pasture-based systems, there are fewer suitable options. Reducing UN will simply require dilution of N supplied by pasture by supplementing low N conserved forages. The results also evidence the risk of pollution swapping, reaching the frontier means arriving at a point where trade-off decisions need to be made. Any further reduction in UN implies an increment in CH 4 , or reduction in CH 4 emissions increases UN. There is no perfect diet to optimize all objectives simultaneously; but if the current diet is not in the frontier some options can offset pollution swapping. The choice is with the farmers and conditioned by their context. [ABSTRACT FROM AUTHOR]

Reducing the dietary cation-anion difference (DCAD) has been shown to be an effective means of preventing parturient paresis in confinement systems where cows are offered a total mixed ration containing DCAD-reducing mineral compounds (anionic salts). Such a supplementation strategy is not possible in cows being group fed forages precalving, and little is known about the effect of supplementing these cows with large amounts of anionic salts twice daily. Eight non-lactating, pregnant Holstein-Friesian cows were allocated to two levels of DCAD (-20 and +18 meq/100 g DM) for 24 d, with an intensive Ca balance undertaken in metabolism stalls following a 2-week acclimatization to diet. The basal diet was 3 kg DM of crushed barley and 7 kg DM of pasture-hay. Urine and faeces were collected separately, weighed daily for 5 d and analysed for Ca content. Urinary Ca, creatinine and hydroxyproline concentration and plasma Ca concentration were determined during the period of the balance study. The diurnal pattern in urine and rumen pH was determined over 2 d. Decreasing DCAD reduced (P<0.001) the pH of urine, and increased (P<0.05) Ca absorption. Plasma Ca concentration was not affected by DCAD, and DCAD did not affect the output of urinary hydroxyproline, a marker of bone resorption. Twice-daily supplementation of anionic salts was sufficient to reduce the pH of blood and increase gastrointestinal Ca absorption. There was no diurnal variation in the pH of urine, suggesting that time of sampling to determine efficacy of DCAD in reducing systemic pH was not important.

In five short-term experiments conducted in Victoria in 1997 and 1998, grazing dairy cows were given either pasture alone or pasture supplemented with high-energy concentrates, and the fatty acid profiles of milk fat were measured. We established the effects of these feeds on some aspects of milk fat of importance for human nutrition, but we specifically focused on the hypothesis that conjugated linoleic acid (CLA) concentrations in milk fat increase as pasture intake increases, and decrease as more concentrates are fed. In agreement with previous research, feeding fresh pasture alone resulted in high concentrations (1.0-1.8 g/100 g milk fat) of CLA. When the effect of level of pasture consumption on CLA content was examined, a significant positive relationship (r2 = 0.35; P < 0.05) was obtained. When cereal grain concentrates were used to supplement pasture intake, the CLA content of milk fat generally declined (P < 0.05), except where the amount of concentrates given led to a marked reduction in total milk fat concentration. The use of cereal grain concentrates also generally resulted in significant (P < 0.05) increases in medium-chain saturated fatty acids, but always reduced the contribution of butyric acid to milk fat, from 4.5 to 3.9 g/100 g milk fat, on average.

Two experiments were undertaken to determine the effects of cereal grain and fibre (hay or straw) supplements on the fatty acid composition of milk fat of grazing dairy cows in early lactation. In both experiments, grain supplements significantly increased (P < 0.05) the proportion of the endogenously synthesized 10:0-16:0 fatty acids. Of the C18 acids, the proportion of 18:0 and 18:3 was significantly decreased (P < 0.05) by grain supplementation, while that of 18:2 was significantly increased (P < 0.05). Irrespective of diet, 18:1 trans-11 was the most dominant trans 18:1 isomer in milk fat. In the first experiment, the proportions of the 18:1 trans-11 isomer and conjugated linoleic acid (CLA, 18:2 cis-9, trans-11) were highest for the pasture-only diets, and significantly (P < 0.05) decreased with grain supplementation. The opposite result was observed in the second experiment, conducted in a different dairy region, suggesting that factors such as the quality of pasture on offer and the physiological state of the cow could affect the content of CLA and trans fatty acids in milk fat. In both experiments, there was a significant positive linear relationship between CLA and 18:1 trans-11. Fibre supplements had little effect on the fatty acid composition of the milk.