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Extraordinary advances are occurring in biomedical science that may revolutionise how we approach health and disease. Many have applications in the dairy industry. We have described one particular area of extracellular vesicles that have already proven to be of interest in diagnostics and prognostics for fertility and assessment of ‘transition’ cows (i.e. evaluation of the problems related to the risk of clinical diseases in dairy cows, such as mastitis and milk fever, during transition period). The addition of measurements of circulating RNA and DNA may prove of value in identifying dairy cows with higher risks of clinical diseases and potentially poor fertility. We describe the exciting opportunity provided by the possibility of generating exosomes to order as therapeutic agents to potentially enhance fertility. The even more radical concept of using exosomes to deliver a CRISPR-linked gene editing function is presented. Undoubtedly, the use of biomedical advances to assist the dairy industry is an obvious and practical approach that has significant merit.

Lying behaviour and activity were measured in healthy grazing dairy cows during the transition from late gestation to early lactation (i.e. the transition period). Behaviour data derived from IceTag® or IceQube® (IceRobotics, Edinburgh, Scotland, UK) tri-axial accelerometers were collated from 311 cow parities of mixed age and breed (Holstein–Friesian, Jersey and crossbred Holstein–Friesian × Jersey) cows from four experiments. The IceTag and IceQube devices captured lying and step data at 1- and 15-min intervals respectively. Behaviour was recorded during the transition period (Day –21 prepartum to Day 34 postpartum) to determine daily lying time, number of lying bouts (LB), mean LB duration and number of steps. The effect of rainfall and air temperature on lying behaviour and activity during two periods, namely, prepartum (Day –21 to Day –3) and postpartum (Days 3–34) was evaluated. Multiple-regression analysis determined that decreased air temperature and increased rainfall is associated with a decline in daily lying time, number of LB and LB duration during both prepartum and postpartum periods. Exposure to both wet and cold conditions exacerbated the behavioural response. The results highlighted the importance of considering the effects of air temperature and rainfall and the interaction of these two climate variables when analysing lying behaviour and activity. Further work is required to quantify the trigger points for this activity modulation, to help understand the balance of welfare experiences in the life of a grazing cow.

In grazing systems, the marginal milk-production response to additional feed (i.e. supplement) is dependent on the relative feed deficit of the cow. We hypothesised that the relative feed deficit could be defined by post-grazing residual (PGR), with a greater PGR indicating a smaller relative feed deficit. The objective of our study, therefore, was to determine the relationship between post-grazing residual and the marginal milk-production response to supplements. We undertook a computerised literature search utilising keywords associated with grazing systems and supplementary feed. We collated data from 26 experiments and 90 treatments, wherein pasture-level, supplementary-feed, and milk-production variables were reported. A meta-analysis was undertaken using random coefficient regression fitted as a mixed model to determine the marginal milk-production response to supplements. On average, pasture DM intake declined (P < 0.001; –0.28 kg/kg supplement DM) and milk, fat and protein yields increased (P < 0.001; 0.64 kg, 20 g and 30 g/kg supplement DM respectively) with an increased supplement use. For every kilogram of DM supplement consumed, PGR pasture height and mass increased by 1.4 mm and 42 kg DM/ha. Associated with every 10-mm increase in post-grazing pasture height in the control treatment, marginal milk response declined (P < 0.05) by 9%. These results will enable farmers to use the change in PGR when feeding supplements, to estimate likely marginal milk-production response to supplementary feeds.

There have been several analyses of the economics of pastoral dairy farm systems in New Zealand using real farm data, as well as several relevant international studies. However, these analyses have often used a dataset with a limited number of years that do not reflect long-term exposure to volatility, or do not allow for regional differences, and often focus on imported feed without due attention to other important characteristics of profitable farms. Several prior analyses have failed to consider the importance of a business that is resilient to major risks. We re-examined the relevance of their conclusions for New Zealand dairy systems against 12 years of DairyBase data, focussing on two major regions, deriving key insights on relevant strategic choices for profitable and resilient businesses at a farm and, by extension, industry level. Within years and regions, the top quartile of observations was identified, on the basis of ranking by operating return on assets, as a proxy for farms achieving their potential, and compared with the remaining observations. Within geographical region, the greater profitability of the top quartile was associated with greater pasture and crop eaten, greater stocking rate and production per cow, and lesser operating expenses per hectare and per kilogram milksolids (MS), defined as fat plus protein. However, greater profitability was not associated with greater use of imported feed. Linear regression was used to determine that increases in total operating expenses were associated with increases in the costs of imported feed (including winter grazing and silage made on farm). On average, for every NZ$1 spent on imported feed, total costs increased by NZ$1.66 and NZ$1.53 for the Waikato and Canterbury–Marlborough regions, respectively. This is consistent with the international literature for temperate grazing systems and is likely the reason why profitability was not greater even if above-average responses to supplement were achieved on farm. Indeed, greater use of imported feed was positively associated with operating expenses per kilogram of MS, implying that the marginal cost of additional MS was greater than the cost of the base milk, and often higher than the value of the milk produced. If gross farm revenue per kilogram MS (which is largely made up of the milk price, with a lesser contribution from livestock sales) was greater than NZ$7.50 (which it was the case in only 3 of the past 12 years), farms could generate higher profit from more imported feed use; however, the reverse was true at lower milk prices. When milk prices are low, (i.e. gross farm revenue is less than NZ$6.50/kg MS, which occurred in half of the past 12 years), farmers are often under cashflow pressure. Therefore, farm systems that are less reliant on imported feed provide a better chance for farmers to meet financial commitments, although they fail to maximise profitability when the milk price is high (e.g. >NZ$7.50/kg MS). In conclusion, maximising pasture harvested, and minimising reliance on supplementary feed, and effective cost control (minimising expenditure) are the key factors that lead to profitable businesses that are also resilient to the low milk prices that occur in volatile markets.

The sustainable intensification of pasture-based food-production systems provides an opportunity to align the ever-increasing global demand for food with the necessity for environmentally efficient ruminant production. Biophysically and financially resilient grazing systems are designed to harvest a large amount of the pasture grown directly by the cow, while minimising the requirement for machinery and housing, and exposure to feed prices. This is primarily achieved by matching the feed demand of the herd with the annual pasture supply profile (i.e. seasonal milk production). Ideally, the entire herd is calved before pasture growth equals herd demand; breeding and drying-off policies facilitate this. The type of cow is also important; she must be highly fertile and have good grazing-behaviour characteristics. Pasture species are chosen to best suit the predominant climate, and pasture management aims to maximise the production and utilisation of chosen species. Purchased supplementary feeds support biophysical resilience and can be successfully incorporated into grazing systems, if stocking rate (SR) is increased to achieve high pasture utilisation. However, industry databases indicate that, on average, profitability declines with increasing purchased supplementary-feed usage, because of reduced pasture utilisation and lower than expected marginal milk-production responses. In the present paper, we outline the characteristics of resilient pasture-based dairy systems in the context of the necessity for the sustainable intensification of global food production.

Dairy heifer growth and liveweight at first calving are regarded as important management variables affecting profitability and animal welfare. However, the appropriateness of heifer growth rate targets for different farming systems is not clear. Retrospective assessments of the association between heifer liveweight and subsequent productivity indicate significant benefits in milk production and, even, reproduction from increasing liveweight at breeding and first calving. However, prospective interventionist experiments do not concur, with very variable effects of liveweight at breeding on milk production and with only limited evidence of a positive effect of first-calving liveweight on first-lactation milk yield. In addition, any benefit in the first lactation is not evident in subsequent lactations in the limited number of long-term studies reported. Pre-weaning nutrition and average daily weight gain are areas of increasing interest, with lifelong increases in milk production resulting from accelerated growth rates during the first 8 weeks of life, indicating a possible significant return from a short-term investment. This could be one reason for the inconsistent effects of heifer liveweight at breeding and first lactation on milk production. Although the effect of pre-weaning average daily gain on heifer liveweight is short-lived, a recent meta-analysis indicated that pre-weaning average daily gain explains 22% of the variation in first-lactation milk production. Whether these differences in animal physiology have relevance in grazing systems, wherein heifers and cows do not consume sufficient nutrients to reach their potential, requires investigation. Despite considerable extension efforts over successive decades, current evidence indicates that failure to provide the new-born calf with sufficient high-quality colostrum is common. To understand the reasons for suboptimal colostrum feeding requires social research, with appropriate extension strategies developed to elicit practice change. Although there can be little doubt regarding the importance of heifer rearing to the profitability and sustainability of the farming business, the collective literature points to a failure of retrospective analyses in determining the cause of poor heifer performance. In reality, it is likely to be a combination of factors. The objective of this review is to investigate the effect of liveweight gain at various stages of the growth cycle of the heifer on the milk-production capacity of the lactating animal.

The transition period of the dairy cow generally refers to the last three weeks of gestation and the first three weeks of lactation. During this period, the dairy cow faces numerous physiological challenges, requiring both homeostatic and homeorhetic changes to support the demands of lactation. Management strategies to achieve a successful transition have developed over many decades. Historically, these strategies focussed on achieving high energy intakes pre-calving in an attempt to improve post-calving metabolism; however, more recent research has indicated that this approach may not be appropriate. Physiological and molecular data have indicated that imposing a slight negative energy balance (EBAL) pre-calving can improve post-calving EBAL, metabolic health indices and milk production. It was hypothesised that the challenges of the transition period would be less in a grazing system than in an intensive confinement system, due to the lower milk production and the difference in population density and, therefore, pathogen exposure. However, the molecular and immunological responses to the change of state are similar in magnitude in a moderate-yielding pasture-fed cow and in a high-yielding cow fed a total mixed ration. The collective data point to a peripartum immunosuppression, which is affected by body condition score and feeding level. This review will outline the literature and provide an assessment of the most recent transition cow management for grazing dairy cows.

Dairy cow fertility has declined in recent decades, coincidental with large increases in milk production. Cows take longer to return to oestrus, display poorer signs of oestrus, have greater early embryo loss, and may have poorer conception rates. The problem is often considered to be nutritional, at least in part, and, therefore, can be corrected through dietary adjustment. Although acknowledged as highly digestible, high quality pastured forages tend to be low in non-structural carbohydrates (NSC), high in rumen degradable protein and the temporal supply may not be adequate for cow demand at key times; diet adjustment is often recommended to overcome these limitations. The interaction between nutrition and reproduction is poorly defined, however, and study results are often contradictory. Hypothesised limitations to pastured forages within a grazing system will be discussed, and the likely impact of nutritional adjustment on pre- and post-ovulatory reproductive processes examined. The effect of energy balance, carbohydrate type, protein and fat on reproductive outcomes will be considered. Nutrition is an important component of successful reproduction, but dietary adjustment to improve pregnancy rates is complicated, and merely offering pastured cows a supplement is unlikely to result in large effects. Conclusions indicate that care must be taken in interpreting associative analyses and in applying results from different farming systems.

Prevailing weather conditions are one factor that influences herbage growth and quality, and therefore may have a substantial impact on animal production. The objective of the present study was to quantify the associations between weather, herbage quality and mineral concentration, and animal production. Daily weather data and weekly records of herbage quality and mineral concentration, as well as dairy cattle production, were available from a research farm and nearby weather station across the years 1995 to 2001, inclusive. Animal production variables of interest included individual cow milk production and composition, body condition score, and liveweight, as well as group herbage dry matter intake. Results indicate moderate relationships between some weather- and herbage-related variables and dairy cattle production variables, although most relationships appeared to be an artefact of temporal variation, as evidenced by weakening of correlations following adjustment for animal parity, stage of lactation, and week of the year at calving. Prior to adjustment for the confounding factors, the negative associations between milk yield and all temperature-related variables (r = –0.46 to –0.34) were most notable. Following adjustment for time of year, milk yield became positively associated with sunlight hours (r = 0.14). Negative relationships were demonstrated between temperature-related variables and milk protein concentration (r = –0.08), regardless of time of year. Milk protein concentration was positively associated with herbage metabolisable energy content (r = 0.06), water-soluble carbohydrate (r = 0.11), and organic matter digestibility (r = 0.06) concentrations, and negatively associated with ether extract (r = –0.07), acid detergent fibre (r = –0.06), and neutral detergent fibre (r = –0.05) concentrations. Weather, herbage quality and mineral concentration explained up to 22% more variation in dairy cattle production variables over and above farmlet and time of year, with a greater effect on dry matter intake than the other production parameters.

Prevailing weather conditions are one factor that influences herbage growth and quality, and therefore may have a substantial impact on animal production. Before investigating relationships between weather factors, herbage growth and quality, and animal production, it is beneficial to first quantify temporal trends in weather variables. The objective of the present study was to investigate the existence of temporal weather trends in a predominantly dairy production region of New Zealand, and to quantify the level of intra-dependency among the weather variables measured. Daily weather data across the years 1995 to 2001 were merged. Fitted sinusoidal functions demonstrated cyclic temporal trends in weather throughout the year. Air and soil temperatures, radiation, and potential evapotranspiration were highly repeatable within fortnight. Repeatability of all other weather variables was low; for example repeatability of rainfall was ≤7%. Linear relationships were also observed among all weather variables. All air and soil temperature measurements were highly positively correlated with each other (r = 0.53–0.99), and with evaporation (r = 0.40–0.68) and potential evapotranspiration (r = 0.43–0.79), while maximum air temperature was positively correlated with radiation (r = 0.61). Further investigation is required to quantify the effect of temporal weather trends on herbage growth and quality, and subsequent animal production.

Over the past three decades, there has been a significant decline in dairy cattle fertility. A large proportion of pregnancy losses are believed to occur during the pre-implantation period, when the developing embryo is elongating rapidly and signalling its presence to the maternal system. The molecular mechanisms that prevent progression of the estrous cycle and allow the allogenic embryo to survive within the maternal environment are not well understood. To gain a more complete picture of these molecular events, global transcriptional profiling was performed using endometrial tissue from reproductive day 17 pregnant and non-pregnant (cycling) Holstein-Friesian dairy cattle. Microarray analysis revealed 357 differentially expressed transcripts (with≥2 fold change in expression; P-value < 0.05) between pregnant and cycling animals in both caruncular and intercaruncular tissue. Additionally, 122 and 26 differentially expressed transcripts were identified only in either caruncular or intercaruncular endometrium, respectively. Pathway analysis of differentially expressed genes revealed enrichment for genes involved in interferon signalling and modulation of the immune response in pregnant animals. Many of these genes have already been described in relation to bovine reproduction. However, this analysis also revealed a number of genes not previously identified in this context, providing further insight into the mechanisms by which the embryo regulates the maternal immune response.

Prevailing weather conditions influence herbage growth and quality, and therefore may have a substantial impact on animal production. Before investigating relationships between weather factors, herbage quality, and animal production, it is beneficial to first quantify temporal trends in herbage quality characteristics and mineral concentrations. The objective of the present study was to investigate the existence of temporal trends in herbage quality characteristics and mineral concentrations, and to quantify the intra-dependency among these variables. Weekly herbage quality and mineral concentration data from a research farm were collected from 1995 to 2001, inclusive. Fitted sinusoidal functions demonstrated cyclic temporal trends across herbage quality variables, but there was little cyclic temporal variation in the majority of herbage mineral concentration variables. The repeatability of herbage quality measurements was low to moderate (22% for ether extract to 54% for metabolisable energy). Linear relationships were observed within all herbage quality variables and herbage mineral concentration variables. Neutral detergent fibre and acid detergent fibre concentrations were strongly positively correlated with each other (r = 0.87), and negatively correlated with herbage digestibility (r = –0.64 and –0.74, respectively), water-soluble carbohydrate concentration (r = –0.52 and –0.68, respectively) and metabolisable energy content (r = –0.60 and –0.75, respectively). The absolute correlations among most herbage minerals were poor (r

Insufficient water availability is one of the most serious environmental stresses for a plant and can be a major limitation to herbage production in many regions. Plant hormones, such as cytokinins, have been reported to reduce the detrimental effects of low water availability in many different plant species. However, there is little research available concerning the effect on pasture grasses. The aim of the present study was to quantify the effect of surface applications of 6-benzylaminopurine (BAP) before and during water deficit on herbage growth and quality of perennial ryegrass–white clover pastures. Pastures fertilised with BAP were compared with unfertilised pastures and pastures receiving nitrogen. Exogenous BAP application did not significantly affect herbage production or quality relative to unfertilised pastures. Nitrogen fertiliser increased total herbage production, but had little effect on herbage quality compared with BAP. The failure of surface applications of exogenous BAP to improve herbage production or quality suggests that it is not an appropriate method to enhance plant tolerance to water deficit at the concentration applied in this study.

Osmoprotectants have been reported to reduce the detrimental effects of various environmental stresses in many different plant species. However, there is little research available concerning pasture species. Two experiments were undertaken with the aim of quantifying the effect of surface applications of exogenous glycine betaine (GB) on herbage production and quality of perennial ryegrass (Lolium perenne L.)–white clover (Trifolium repens L.) pastures during periods of moisture stress and cold temperatures over 2 years. Pastures fertilised with GB were compared with unfertilised pastures and pastures fertilised with nitrogen (N). Rates of 0.5, 1.0 and 1.5 kg GB/ha.defoliation were applied in experiment 1 and 5 kg GB/ha.defoliation was applied in experiment 2. Surface applications of GB did not significantly affect herbage production relative to unfertilised pastures; herbage yields averaged 12 248 and 12 693 kg DM/ha over 11 months in experiment 1, and 7253 and 7177 kg DM/ha over 6 months during summer and autumn in experiment 2, for the unfertilised control and GB, respectively. During both experiments, herbage quality parameters were not affected by GB application, although the proportion of white clover in the sward between summer and winter during experiment 1 was greater (P < 0.01) in plots treated with GB than in untreated plots. Application of N fertiliser increased (P < 0.001) herbage production, but did not consistently affect herbage quality. The failure of surface applications of exogenous GB to improve the herbage production or quality of perennial ryegrass–white clover pastures suggests that it is not an appropriate method to enhance plant tolerance to environmental stress at the concentrations applied in these studies.

The objective of the current study was to quantify the effects of greater herbage residuals in winter on leaf appearance rate, herbage accumulation and quality, and plant energy reserves, as well as quantifying the effects nitrogen (N), or phosphorus (P) and sulfur (S) fertilisers had on the above measures. Ten pasture areas were grazed to different residual masses (1260 ± 101 and 1868 ± 139 kg DM/ha, Severe and Lax, respectively) over five consecutive days by dry dairy cows. Two randomly located subplots within each grazing area were fertilised with either 50 kg N/ha (N treatment) or 50 kg N/ha, 31 kg S/ha plus 26 kg P/ha (N + S + P treatment) on the day immediately following defoliation (day 1), and were compared with a control subplot. Neither growth rate (15.1 ± 8.1 kg DM/ha.day), nor leaf appearance rate (15.1 ± 0.3 days per new leaf) differed between treatments. As a result, herbage accumulated over the 49 days of regrowth was similar across grazing treatments and averaged 726 kg DM/ha. Application of N + S + P tended to increase total herbage accumulated during regrowth compared with either the control or N treatment subplots (860 v. 675 and 643 kg DM/ha, respectively), likely a result of increased tiller density. Swards defoliated more severely had lower initial water-soluble carbohydrate (WSC) concentrations compared with swards laxly defoliated, but this difference had disappeared before appearance of the third new leaf. Herbage quality improved in the Severe treatment subplots after emergence of the third new leaf, with higher digestibility, greater WSC and metabolisable energy, and lower fibre content than in laxly grazed subplots.

This experiment investigated whether increased crude protein concentration in turnips fertilised with nitrogen would improve milk production. Dairy cows were offered a basal diet of silage, hay and 5 kg dry matter barley supplemented with 5 kg dry matter turnips fertilised with nitrogen (n = 12) or 5 kg dry matter control turnips (n = 12) over 14 days. The effect of providing a diet isonitrogenous with the nitrogen-fertilised turnip diet and with rumen degradable protein on milk production was also investigated by replacing 1 kg barley with 1 kg lupins; 12 cows were offered 4 kg (dry matter) barley, 1 kg lupins with 5 kg control turnips. The control cows (offered control turnips with barley) consumed 17.8 kg dry matter, 2.34 kg crude protein and 187 MJ metabolisable energy. In comparison with the control cows, cows offered nitrogen-fertilised turnips with barley had lower (P

This review considers the current literature on the energy and protein nutrition of dry cows and its subsequent impact on early lactation performance. Energy intake close to calving appears to be critical to events that occur post-partum, such that a key objective of dry cow feeding should be to maximise or maintain feed intake immediately prior to calving, or at least to minimise the decline in intake. Although a decline in dry matter intake seems to be a normal adaptive event in peri-parturient ruminants, it is the magnitude and duration of the decline that are of concern. Most research has been undertaken using total mixed rations or conserved forage and concentrates, where a wide range of quantities and types of feeds have been used. However, no clear conclusions can be drawn regarding optimum levels of feeding, types of forage, or proportions of concentrates that should be fed to cows in the late dry period to minimise the intake decline. The importance of maintaining energy intake is associated with the reduction of the incidence and severity of metabolic diseases post-partum, by reducing triglyceride mobilisation from adipose tissue, and preventing excessive depletion of hepatic glycogen levels.

This review considers the current literature on the macro-mineral nutrition of the soon-to-calve, or transition, dairy cow. Calcium is the main focus, since milk fever (clinical hypocalcaemia) appears to be the most common mineral-related problem faced by the transition cow Australia-wide. The importance of minimising calcium intake and optimising the balance of the key dietary electrolytes, sodium, potassium, sulfate, and chloride, in the weeks before calving is highlighted. Excess dietary potassium can, in some situations, induce milk fever, perhaps even more effectively than excess calcium. Excess sodium remains under suspicion. In contrast, excess dietary chlorine and, to a lesser extent, sulfur can improve the ability of the cow to maintain calcium homeostasis. Diets that promote either a hypomagnesaemia or hyperphosphataemia have also the potential to precipitate milk fever at calving. Current prevention strategies focus on the use of forages with moderate to low levels of calcium, potassium, and sodium, and also rely on or utilise addition of chloride and sulfate in the form of 'anionic' feeds. Anionic salts are one example of an anionic feed. However, legitimate questions remain as to the effectiveness of anionic salts in pasture-feeding systems. The causes and prevention of milk fever are considered from the perspective of the variety of Australian feedbases. Impediments to the use of anionic feeds in Australia feeding systems are outlined. The potential for improving maternal reserves of calcium around calving to reduce the risk of milk fever is also discussed.

Two experiments were conducted to test the hypothesis that offering a given daily allowance of herbage as smaller feeds more frequently than once per day will increase daily herbage intake and milk yield. In experiment 1 (spring 1995), cows in early lactation were offered either 40 or 65 kg DM/cow.day allowance of herbage as either 1 feed or as 6 equal feeds. The latter cows received a fresh strip of herbage at 0600, 0900, 1100, 1330, 1800 and 2000 hours. The experiment lasted 28 days with treatment effects being measured from days 15 to 28. There were no significant differences in herbage intake (15.6 v. 15.9 kg DM/cow.day), grazing time (9.4 v. 9.5 h/cow.day), milk production (25.4 v. 25.2 L/cow.day) or milk composition between the 1-feed treatment and 6-feed treatment, respectively, during the final 2 weeks of the experiment. Increasing herbage allowance increased (P

Many farmers in southern Victoria grow fodder turnips as a summer feed for lactating dairy cows. This paper reports on 2 experiments that measured the milk yields and liveweight changes of cows offered a basal forage diet and combinations of turnips, barley and protein supplements (cottonseed meal or lupins). A stall feeding experiment was conducted over 26 days with 40 Friesian cows in mid lactation offered 1 of 5 dietary treatments. All cows were offered 10 kg DM/day of a basal diet comprising pasture, pasture hay and pasture silage which is similar to that available on many southern Victorian dairy farms during summer. Cows in a control group did not receive additional feed supplements. Cows in the other 4 groups were offered a supplement of 5 kg DM/cow.day of either turnips, barley or a mixture containing 3 kg DM/cow.day of turnips and 2.0 kg DM/cow.day of either crushed lupins or cottonseed meal. The marginal milk responses from barley, turnips, turnips + lupins and turnips + cottonseed meal were 0.80, 0.92, 1.15 and 1.00 L/kg DM of supplement eaten. There were no significant differences (P>0.05) in the liveweight changes of the supplemented groups. Samples of the feeds used in this experiment were placed in nylon bags and incubated in the rumen of non-lactating dairy cows. The ‘Ørskov’ protein degradation parameters for these feeds are compared with the published values for a range of Australian feeds. The rate and extent of degradation of protein from the turnip leaves, turnip bulbs and crushed barley were all similar. A grazing experiment was conducted over 65 days with 56 Friesian cows in mid lactation, offered 1 of 4 dietary treatments. All groups were allowed to graze pasture (5 kg DM/cow.day), were offered 3 kg DM/cow.day of pasture silage and were fed different combinations of barley, cottonseed meal and lupins. In addition, 3 of the groups separately strip-grazed turnips (about 5 kg DM/cow.day). The group fed a supplement of 8.0 kg/cow.day of barley yielded similar quantities (18.3 L/cow.day) of milk and milk constituents as another group fed 4.0 kg DM/cow.day of barley and 4.5 kg DM/cow.day of turnips. Furthermore, when either 1.5 kg DM of cottonseed meal or 2.0 kg of lupins were fed in place of barley, milk yield increased by 1.4 L/cow.day. Dietary treatment had no significant (P>0.05) effects on liveweight changes. From this grazing experiment it is concluded that turnips can be used as a cheaper alternative to barley in order to maintain high levels of milk production in summer–autumn. We estimate that if the above quantities of protein supplement were fed with turnips, at 1997–98 prices, lupins would increase profits by 12 cents/cow.day, but there would be no financial benefit from the cottonseed meal. The findings from both experiments show that supplements of rumen-degradable protein (lupins) can produce an economic milk response when fed to cows on typical summer diets (pasture/silage/barley and turnips) in southern Victoria.

Summary. The effect of herbage allowance (20, 30, 40, 50, 60 and 70 kg DM/cow. day) on the consumption of nutrients from herbage and milk production by cows in early lactation, was examined. The experiment was conducted on rainfed perennial ryegrass pastures in September and October 1997 in south-eastern Victoria, Australia. The herbage on offer comprised 64% perennial ryegrass, 21% other grasses, 1% white clover, 5% weeds and 9% dead material on a dry matter (DM) basis. The average pregrazing herbage height was 13 cm, at an estimated pregrazing herbage mass of 3.6 t DM/ha. The herbage on offer was of high quality containing 11.6 MJ metabolisable energy/kg DM, 202 g crude protein/kg DM and 525 g neutral detergent fibre/kg DM. Concentrations of calcium, magnesium, sodium, potassium, phosphorus, sulfur and chloride were 4.4, 2.2, 4.4, 31.2, 3.5, 2.7 and 11.4 g/kg DM, respectively. As daily herbage allowance per cow increased, dry matter intake increased curvilinearly (P