Milk transcriptome biomarker identification to enhance feed efficiency and reduce nutritional costs in dairy ewes

In recent years, rising prices for high-quality protein-based feeds have significantly increased nutrition costs. Consequently, investigating strategies to reduce these expenses and improve feed efficiency (FE) have become increasingly important for the dairy sheep industry. This research investigates the impact of nutritional protein restriction (NPR) during prepuberty and FE on the milk transcriptome of dairy Assaf ewes (sampled during the first lactation). To this end, we first compared transcriptomic differences between NPR and control ewes. Subsequently, we evaluated gene expression differences between ewes with divergent FE, using feed conversion ratio (FCR), residual feed intake (RFI), and consensus classifications of high- and low-FE animals for both indices. Lastly, we assess milk gene expression as a predictor of FE phenotype using random forest. No effect was found for the prepubertal NPR on milk performance or FE. Moreover, at the milk transcriptome level, only one gene, HBB, was differentially expressed between the NPR (n = 14) and the control group (n = 14). Further, the transcriptomic analysis between divergent FE sheep revealed 114 differentially expressed genes (DEGs) for RFI index (high-FERFI = 10 vs low-FERFI = 10), 244 for FCR (high-FEFCR = 10 vs low-FEFCR = 10), and 1 016 DEGs between divergent consensus ewes for both indices (high-FEconsensus = 8 vs low-FEconsensus = 8). These results underscore the critical role of selected FE indices for RNA-Seq analyses, revealing that consensus divergent animals for both indices maximise differences in transcriptomic responses. Genes overexpressed in high-FEconsensus ewes were associated with milk production and mammary gland development, while low-FEconsensus genes were linked to higher metabolic expenditure for tissue organisation and repair. The best prediction accuracy for FE phenotype using random forest was obtained for a set of 44 genes consistently differentially expressed across lactations, with Spearman correlations of 0.37 and 0.22 for FCR and RFI, respectively. These findings provide insights into potential sustainability strategies for dairy sheep, highlighting the utility of transcriptomic markers as FE proxies.

The impact of automated, constant incomplete milking on energy balance, udder health, and subsequent performance in early lactation of dairy cows

Incomplete milking (IM) is one way of mitigating the negative energy balance (NEB) that is characteristic for early lactation and may increase the risk for disease. Our objectives were to test the effects of IM in early lactation on energy balance (EB), metabolic status, udder health, and subsequent performance. To facilitate the practical application, an automated system was used to remove the milking clusters once a predefined amount of milk is withdrawn. Forty-six Holstein cows were equally allocated to either the treatment (TRT, starting on 8 d in milk) or the control group (CON; conventional cluster removal at milk flow rate <0.3 kg/min). Milk removal in the TRT group was limited to the individual cow's milk yield 1 d before IM started and held constant for 14 d. Thereafter, all cows were conventionally milked and records related to EB, performance, and udder health were continued up to 15 wk of lactation. During the 14 d of IM, on average 11.1% less milk was obtained from the TRT cows than from the CON cows. Thereafter, milk yield increased in the TRT group, eliminating the group difference throughout the remaining observation period until wk 15 of lactation. The TRT cows tended to have less dry matter intake and also water intake than the CON cows. The extent of the NEB and the circulating concentrations of fatty acids, β-hydroxybutyrate, insulin-like growth factor-1, and leptin mostly did not differ between the groups. The IM did not affect body condition. Udder health was maintained over the entire observation period in all cows. Our results demonstrate the applicability of the automated cluster removal for limiting milk withdrawal to a defined amount in early lactation. However, it remains to be determined whether the absent effect on energy metabolism was due to the relatively stable energy status of the cows or to the relatively mild IM setting used herein.

Reducing milking frequency from 3 to 2 times daily in early lactation: effects on milk production, health and body condition

The objective of this experiment was to investigate the effect of reducing early lactation milking frequency on milk yield and persistency through lactation and early lactation fat mobilization, measured by body condition score (BCS) and BHB in milk. We hypothesized that milking cows twice per day in early lactation before milking them 3 times per day for the remaining lactation would cause less fat mobilization in early lactation, a lower peak milk yield but improved persistency throughout lactation compared with milking cows 3 times per day for the entire lactation. The experiment took place on 2 commercial dairy farms in Denmark. All cows calving in a period of nine months (n = 239) in their current first and later parities were randomly allocated at dry-off to 1 of 3 treatments based on expected calving date. The treatments were (1) cows milked 2 times per day for 1 week after calving, (2) cows milked 2 times per day for 4 weeks after calving and (3) cows milked 2 times per day for 7 weeks after calving. All cows were then milked 3 times per day for the remaining lactation. Milk yield peaked 3.3 and 3.6 d later and milk yield persistency improved with 18 and 19 g per day when cows were milked 2 times per day for 4 and 7 weeks, respectively, compared with milking 2 times per day for 1 week after calving. We found a significant highest milk BHB in treatment 2, but the underlying effect of milking cows 2 times per day for 4 weeks compared with 1 or 7 weeks was unclear. In conclusion, we did not confirm our hypothesis that milking cows 2 times per day compared to 3 times in early lactation would reduce fat mobilization and reduce peak yield. We did, however, find an improved milk yield persistency, which partially offset a numerical reduction in peak yield, and hence there was no significant effect of reducing early lactation milking frequency on total lactation (305 DIM) milk yield.

Cow milking order and its influence on milk production in a pasture-based automatic milking system

Context While several studies have documented the consistency of milking order and its association with milk yield in herds with conventional milking systems, there is limited data available on herds in the automatic milking systems (AMS) where cows move to the dairy voluntarily to be milked. Aims The present study was conducted to examine the consistency of milking order in AMS and its association with milk yield and cow characteristics. Methods The study was performed at The University of Melbourne Dookie Dairy in northern Victoria, Australia. The milking herd had up to 158 Holstein–Friesian cows in a pasture-based AMS with a three-way grazing system. The study utilised the individual-cow milking times, parity number, days in milk and data on daily production (milk yield in kilograms, fat and protein percentages and liveweight) from August 2017 till April 2018. Monthly milking order was determined for each milking session by ranking individual cows on the basis of their recorded time of milking. Key results A consistent milking order was observed with the order of cows at the beginning (percentile rank position 0–33) and end of the milking order (percentile rank position 68–100) being less variable than cows in the middle positions. Milking orders from any two consecutive months were highly correlated (P &lt; 0.01). Energy-corrected milk yield was negatively associated with the milking position (5 of 9 months) and days in milk (8 of 9 months), but positively associated with parity number and liveweight (5 of 9 months). The cow factors such as energy-corrected milk yield, liveweight, parity and days in milk were poor predictors of milking order. This suggests that other factors such as health and social dominance might be of importance. Conclusions This observational study indicated that cows at the beginning of the milking order have a higher milk yield than do cows at the end of the milking order in pasture-based automatic milking systems. Implications Grazing-management strategies that allow cows at the end of the milking order to access fresh pasture are worthy of further investigation.

The milking frequency of primiparous cows in their early stage of lactation and its impact on milking performance

An automatic milking system allows cows to present their full production capability by not limiting them to a specific time when the milking occurs or a fix number of milkings per day. The beginning of the first lactation is a key point in terms of subsequent milk production. The aim of the present study was to indicate the relationship between the milking frequency of primiparous cows during the first month of lactation and their subsequent milk performance. Material of the study consisted of 25 Polish herds of Holstein–Friesian dairy cattle. All cows were milked with the use of an automatic milking system. Animals were divided into five groups, depending on the milking frequency in the first month after calving (MFF). The collected data were statistically processed using the multifactorial ANOVA. The best milk and milking parameters characterised primiparous cows, for which the average number of milkings per day was at the level of 3–3.5 or above, this group did not have a preferred time for their milking. This group of cows milked more frequently during the first month of lactation (MFF5) and had the highest milk yield (MY) and milking duration. The highest culling percentage (57.77%) was noted within the group of primiparous cows with the lowest milking frequency during the first month of lactation (MFF1). MFF5 animals maintained better milk and milking parameters in all months of lactation than did those in the other groups. Older animals, that calved after the 28th month of life, and those that calved during warmer seasons, showed the tendency to have a lower milking frequency and poorer milk and milking parameters. The findings obtained in the present study are interesting in terms of their potential use, because they show that frequent milking during the first month after calving corresponds to a better overall MY during that lactation. Hopefully, by promoting frequent milkings at the beginning of lactation, farmer may increase the overall lactation MY.

Review: extended lactation in dairy cattle

This paper reviews the effects of extended lactation (EXT) as a strategy in dairy cattle on milk production and persistency, reproduction, milk quality, lifetime performance of the cow and finally the economic effects on herd and farm levels as well as the impact on emission of greenhouse gas at product level. Primiparous cows are able to produce equal or more milk per feeding day during EXT compared with a standard 305-d lactation, whereas results for multiparous cows are inconsistent. Cows managed for EXT can achieve a higher lifetime production while delivering milk with unchanged or improved quality properties. Delaying insemination enhances mounting behaviour and allows insemination after the cow's energy balance has become positive. However, in most cases EXT has no effect or a non-significant positive effect on reproduction. The EXT strategy sets off a cascade of effects at herd and farm level. Thus, the EXT strategy leads to fewer calvings and thereby expected fewer diseases, fewer replacement heifers and fewer dry days per cow per year. The optimal lifetime scenario for milk production was modelled to be an EXT of 16 months for first parity cows followed by an EXT of 10 months for later lactations. Modelling studies of herd dynamics indicate a positive effect of EXT on lifetime efficiency (milk per dry matter intake), mainly originating from benefits of EXT on daily milk yield in primiparous cows and the reduced number of replacement heifers. Consequently, EXT also leads to reduced total meat production at herd level. For the farmer, EXT can give the same economic return as a traditional lactation period. At farm level, EXT can contribute to a reduction in the environmental impact of dairy production, mainly as a consequence of the reduced production of beef. A wider dissemination of the EXT concept will be supported by methods to predict which cows may be most suitable for EXT, and clarification of how milking frequency and feeding strategy through the lactation can be organised to support milk yield and an appropriate body condition at the next calving.

Robot utilisation of pasture-based dairy cows with varying levels of milking frequency

Achieving a consistent level of robot utilisation throughout 24 h maximises automatic milking system (AMS) utilisation. However, levels of robot utilisation in the early morning hours are typically low, caused by the diurnal feeding behaviour of cows, limiting the inherent capacity and total production of pasture-based AMS. Our objective was to determine robot utilisation throughout 24 h by dairy cows, based on milking frequency (MF; milking events per animal per day) in a pasture-based AMS. Milking data were collected from January and February 2013 across 56 days, from a single herd of 186 animals (Bos taurus) utilising three Lely A3 robotic milking units, located in Tasmania, Australia. The dairy herd was categorised into three equal sized groups (n=62 per group) according to the cow's mean daily MF over the duration of the study. Robot utilisation was characterised by an interaction (P&lt; 0.001) between the three MF groups and time of day, with peak milking time for high MF cows within one h of a fresh pasture allocation becoming available, followed by the medium MF and low MF cows 2 and 4 h later, respectively. Cows in the high MF group also presented for milking between 2400 and 0600 h more frequently (77% of nights), compared to the medium MF group (57%) and low MF group (50%). This study has shown the formation of three distinct groups of cows within a herd, based on their MF levels. Further work is required to determine if this finding is replicated across other pasture-based AMS farms.

Short communication: The effect of temperature-humidity index on milk yield and milking frequency of dairy cows in pasture-based automatic milking systems

Hot weather is known to negatively affect cow performance primarily through reduced feed intake and milk yield. However, little information is available on how it affects cow milk yield and milking frequency in automatic milking systems (AMS). Milking data were collected from 6 pasture-based AMS farms in Australia to assess the effect of temperature-humidity index (THI) on milk yield and milking frequency. Daily measures of average milk yield per cow and average milking frequency per cow during December to February (Australian summer) were assessed for associations with maximum, minimum, and average THI from d 0, -1, -2, and -3 in relation to the milking data. Average daily milk yield per cow was negatively associated with an increasing maximum, minimum, and average THI (-0.11, -0.08, and -0.15 kg/THI unit increase, respectively) on the collection day and up to 3 d prior. The average daily milking frequency was negatively associated with maximum THI on 1 d (-0.003/THI unit increase) and 2 d (-0.003/THI unit increase) before collection. Our results show that high THI conditions were negatively associated with milking frequency and milk yield in a pasture-based AMS and that research into management and infrastructure (cow cooling) in these systems is warranted to reduce production losses.

Demographics, farm and reproductive management strategies used in Australian automatic milking systems compared with regionally proximal conventional milking systems

OBJECTIVE

To determine the management practices utilised in automatic milking systems (AMS) that affect reproductive management and performance and how these compare with the management practices used in regionally proximal conventional milking systems (CMS).

METHODS

This study examined demographic and management data from AMS and CMS dairy farms through a survey, with a specific focus on reproductive management procedures.

RESULTS

Overall, responses from AMS and CMS dairy farms showed little difference in terms of respondent demographics, farm size, herd structure and most farm management strategies. AMS dairies were more likely to use activity meters or other electronic oestrus detection aids than CMS dairies (P < 0.001) and were also more likely to have changed to electronic recording systems (P = 0.007). Although many respondents indicated that they used key monitoring parameters to assess reproductive performance (e.g. days in milk, conception vs pregnancy rate etc.), the format of responses varied significantly, indicating a relatively widespread (among the respondents) lack of knowledge regarding the meaning and usage of some of these common parameters/terminology.

CONCLUSIONS

Ultimately, reproductive management practices of AMS dairies were largely similar to those of CMS dairies, indicating that such practices can be implemented in a practical sense, even though the resultant reproductive performance is not yet understood. Understanding that the key reproductive management strategies do not need to change vastly is important to ensure that new adoptees are well informed. Further work is needed to objectively measure AMS performance to increase the knowledge base and generate the confidence that will facilitate further adoption of this innovation.

Current and potential system performance on commercial automatic milking farms

Dairy farmers considering installing automatic milking systems (AMS) would benefit from adequate contextual information on commercial AMS farm performance. The aim of the present study was to capture key performance indicators related to AMS utilisation on commercial Australian AMS farms on a monthly basis, with the aim of understanding the current and potential system performance. Eight Australian AMS farms were monitored on a monthly basis for a 12-month period. The average number of milking events (milkings/robot.h) was calculated for every hour of the day, on a monthly basis for each of the participating farms. Data exported electronically also allowed the calculation of the number of current and potential extra (both average and maximum) milkings (milkings/robot.day), cows (cows/robot), yield (kg milk/robot.day) and milking time (h/robot.day) for every month on each farm. Despite a wide range in farm performance, the actual milkings (120 milkings/robot.day), cows (51 cows/robot), yield (1263 kg milk/robot.day) and milking time (13.63 h/robot.day) indicated that there is an opportunity to improve these parameters by a maximum of ~60%. To achieve this would require the adoption of a variety of strategies that might be quite farm specific and would be reliant on optimisation of data relating to cow traffic and system utilisation that are relevant to automatic milking systems.

The effect of herd mentality on dairy heifers conditioned to traffic through audio cues

The objective for the present trial was to understand whether dairy heifers could be trained to respond to an audio cue paired with a feed reward. The use of acoustic conditioning to induce cattle movement has not previously been tested with animal-mounted devices to call cattle both individually and as a group. Five heifers underwent testing for 6 days as part of an 18-day field trial (12 days of conditioning). The 6-day testing and data-collection period involved the heifers being called via a smartphone device mounted on the cheek strap of a halter. Heifers were called either as individuals or as a group. When the audio cue was sent, heifers were expected to traffic from a group-holding area to a feeding area (~80-m distance) to receive an allocation of a grain-based concentrate. Heifers were significantly (P = 0.001) more likely to approach the feeding area when called as a group (91% response rate) than when they were called as individuals (67% response rate). When heifers did respond to being called, their time to traffic to the feed area was quicker (P < 0.001) when they were called as a group (77.9 ± 55.4 s) than when they were called as individuals (139.3 ± 89.2 s). The present trial has shown that animals can be trained to respond to an audio cue paired to a feed reward, highlighting the potential for acoustic conditioning to improve voluntary cow movement with an animal-mounted device. It also highlights the limitations of cattle responding to being called individually compared with being called as a group.

Modelling Pasture-based Automatic Milking System Herds: The Impact of Large Herd on Milk Yield and Economics

The aim of this modelling study was to investigate the effect of large herd size (and land areas) on walking distances and milking interval (MI), and their impact on milk yield and economic penalties when 50% of the total diets were provided from home grown feed either as pasture or grazeable complementary forage rotation (CFR) in an automatic milking system (AMS). Twelve scenarios consisting of 3 AMS herds (400, 600, 800 cows), 2 levels of pasture utilisation (current AMS utilisation of 15.0 t dry matter [DM]/ha, termed as ‘moderate’; optimum pasture utilisation of 19.7 t DM/ha, termed as ‘high’) and 2 rates of incorporation of grazeable complementary forage system (CFS: 0, 30%; CFS = 65% farm is CFR and 35% of farm is pasture) were investigated. Walking distances, energy loss due to walking, MI, reduction in milk yield and income loss were calculated for each treatment based on information available in the literature. With moderate pasture utilisation and 0% CFR, increasing the herd size from 400 to 800 cows resulted in an increase in total walking distances between the parlour and the paddock from 3.5 to 6.3 km. Consequently, MI increased from 15.2 to 16.4 h with increased herd size from 400 to 800 cows. High pasture utilisation (allowing for an increased stocking density) reduced the total walking distances up to 1 km, thus reduced the MI by up to 0.5 h compared to the moderate pasture, 800 cow herd combination. The high pasture utilisation combined with 30% of the farm in CFR in the farm reduced the total walking distances by up to 1.7 km and MI by up to 0.8 h compared to the moderate pasture and 800 cow herd combination. For moderate pasture utilisation, increasing the herd size from 400 to 800 cows resulted in more dramatic milk yield penalty as yield increasing from c.f. 2.6 and 5.1 kg/cow/d respectively, which incurred a loss of up to $AU 1.9/cow/d. Milk yield losses of 0.61 kg and 0.25 kg for every km increase in total walking distance (voluntary return trip from parlour to paddock) and every one hour increase in MI, respectively. The high pasture utilisation combined with 30% of the farm in CFR in the farm increased milk yield by up to 1.5 kg/cow/d, thereby reducing loss by up to $0.5/cow/d (c.f. the moderate pasture and 800 cow herd scenario). Thus, it was concluded that the successful integration of grazeable CFS with pasture has the potential to improve financial performance compared to the pasture only, large herd, AMS.

Invited review: reduced milking frequency: milk production and management implications

Most dairy cows throughout the world are milked twice daily. In intensive dairying systems, however, it is not uncommon to increase milking frequency to between 3 and 6 times daily to increase milk production. Reducing milking frequency is much less common; however, once-daily milking of dairy cows, practiced either strategically during certain parts of the lactation or for the entire lactation, is not uncommon in key dairying countries where less emphasis is placed on milk production per cow. The practice fits well with more extensive dairy production systems, particularly those based on grazed pasture. A feature of once-daily milking is that it reduces milk yield by approximately 22%, depending on stage of lactation, breed, and parity, and it may adversely affect lactation length and persistency. However, it can offer several positive farm management options, especially related to labor requirements and farm working expenses. In addition, it may provide a tool to better manage the metabolism and energy balance of cows during early lactation or during periods of pasture deficit, and it may help to improve reproductive performance and animal health and welfare. Once-daily milking, representing one extreme of the mammary function spectrum, has attracted considerable research interest over the years. Consequently, substantial scientific information is available on its effects on mammary function, at both the physiological and molecular levels. This review focuses instead on the management of the cow milked once daily, covering the production response in relation to breed, stage of lactation, and parity, and its effect on energy status, reproduction, health and welfare, as well as on milk composition and processability.

Triennial Lactation Symposium: A local affair: How the mammary gland adapts to changes in milking frequency

Regular removal of milk from the mammary gland is critical to maintaining milk secretion. Early studies in rodents demonstrated that changes in milking frequency influenced mammary blood flow, as well as mammary cell number and activity. Later studies in ruminants confirmed those observations and that the response was regulated locally within the mammary gland. In addition, it was discovered that increased milking frequency (IMF) during early lactation stimulated an increase in milk production that partially persisted through late lactation, indicating long-term effects on mammary function. The local mechanisms regulating the mammary response to IMF are poorly understood, although several have been proposed. To gain insight into the mechanisms underlying the mammary response to IMF, and to identify genes associated with the response, we used a functional genomics approach and conducted experiments on dairy cows exposed to unilateral frequent milking [UFM; twice daily milking (2X) of the left udder half and 4-times daily milking (4X) of the right udder half]. Across multiple experiments, we were unable to detect an effect of UFM on mammary cell proliferation or apoptosis. We have, however, identified distinct transcriptional signatures associated with the mammary response to milk removal and to UFM during early lactation. Sequential sampling of mammary tissue revealed that when UFM was imposed during early lactation, at least 2 sets of genes were coordinately regulated with changes in differential milk production of 4X vs. 2X udder halves. Moreover, some genes were persistently differentially expressed in 4X vs. 2X udder halves after UFM and were associated with the persistent increase in milk yield. We conclude that a coordinated transcriptional response is associated with the increase in milk yield elicited by IMF during early lactation and that the 2 sets of differentially expressed genes may be a marker for the autocrine up-regulation of milk production. Moreover, we propose that we have identified a novel form of imprinting associated with persistent alteration of mammary function, which we term "lactational imprinting."

Evaluation of two training programs aimed to improve early lactation performance of heifers in a pasture-based automated milking system

The adaptation success of inexperienced heifers to a pasture-based automated milking system (AMS) is likely to influence the viability and feasibility of the system. This study evaluated two heifer training programs designed to improve adaptation success to determine their impact on early lactation performance within a pasture-based AMS. The two training programs involved heifers calving in spring 2007 (S07) and autumn 2008 (A08) being managed as members of the milking herd for 2 weeks, starting 2 months before their expected calving date. In each calving season, heifers were randomised into two treatment groups with one being fed and teat sprayed (FTS) while visiting the milking stations, while the other group passed through (PT) the milking stations. Milk yield, milking frequency and waiting time were selected as indicators of early lactation performance within an AMS and were reported as values relative to those measured by their experienced herdmates (within calving season). Longer relative waiting times (hours spent in pre-milking area where experienced herdmates = 1.0; FTS: 1.36 vs PT: 1.95; P = 0.006) may have been one cause of the low relative milk production levels reported (range 0.49 S07PT–0.78 A08PT). The milking frequencies of the heifers were in line with their experienced herdmates (range 0.83 S07PT–1.10 A08PT). There were no significant differences between the two training programs, indicating that farmers could adopt either program and expect similar early lactation heifer performance. The choice of program would more likely be affected by AMS utilisation levels, costs of consumables (teat spray and concentrate feed) and any existing desire to feed concentrate to heifers during the training period.

Use it or lose it: Enhancing milk production efficiency by frequent milking of dairy cows1

In the past century, great strides have been made toward optimizing milk production efficiency of dairy cows. One of the key findings that has emerged is that the milk yield of dairy cows is responsive to demands of offspring or milk removal; hence, milk production can be increased by frequent milking. Early studies illustrated the galactopoietic effect of frequent milking during the entire lactation, with 3 times daily milking increasing milk yield by up to 20% relative to twice daily milking. Later studies reported that cows produced more milk during the entire lactation if they were allowed to suckle a calf for the first 3 to 4 mo of lactation. The results of these experiments laid the groundwork for current research, which has identified a time during early lactation wherein the mammary gland of dairy cows is especially receptive to the stimulus of frequent milking. This window of time has been slowly whittled down from the first 10 wk of lactation to the first 6 wk, and it was subsequently established that frequent milking for a short duration within the first 3 wk of lactation can increase milk production through the remainder of lactation [corrected] In addition, there is strong evidence that this milk yield response is locally regulated. Consequently, the concept of "use it or lose it" is becoming more clearly established; that is, the stimulus of frequent milking during early lactation permanently increases the milk production capacity of the mammary gland. Exciting research opportunities now present themselves, and ongoing experiments seek to identify the local factors that are involved in the regulation of milk production efficiency of dairy cows.

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

In extensive pastoral dairy farming systems herds graze 12 months of the year with the majority fed a near-100% pasture or conserved pasture diet. The viability of automatic milking in these systems will depend partly upon the amount of supplementary feed necessary to encourage cows to walk from the pasture to the milking unit but also on the efficient use of the automatic milking system (AMS). This paper describes a study to determine the importance of offering concentrate in the milking unit and the effect of minimum milking interval on cow movement and milking performance in a pasture-based AMS. The effects of feeding rate (FR0=0 kg or FR1=1 kg crushed barley/d) and minimum milking interval (MM6=6 h or MM12=12 h) on cow movement and behaviour during milking were studied in a multi-factorial cross-over (feeding level only, 4 weeks per treatment) experiment involving 27 mixed-breed cows milked through a single AMS. Feeding 1 kg barley in the milking unit resulted in a higher visiting frequency to the pre-selection unit (FR0=4·6 visits/d, FR1=5·4 visits/d, sed=0·35, P<0·05) and a higher yield (FR0=22·5 kg/d, FR1=23·6 kg/d, sed=0·385, P<0·01) but had no effect on milking frequency (FR0=1·6 milkings/d, FR1=1·7 milkings/d, sed=0·04, NS). Minimum milking interval was the major factor influencing milking frequency (MM6=1·9, MM12=1·4 milkings/d, sed=0·15, P<0·01). The absence of feeding in the milking unit had no negative effect on behaviour during milking or the number of cows that had to be manually driven from the paddock. The results show that automatic milking can be combined with a near-100% pasture diet and that milking interval is an important determinant for maximizing milk harvested per AMS.