This research communication describes how different detachment levels (0.48, 0.3 and 0.06 kg milk/min) at the quarter-level affect milk flow profiles and overall milking efficiency in automatic milking systems. We hypothesized a higher detachment level would result in greater mean flow rates without affecting the volume of harvested milk per cow during 24 h compared to lower detachment levels. The data suggest milk flow decreased to a rate below the overmilking limit within the 6-s delay time required for termination in all treatments, but the duration of overmilking was shorter for the greatest detachment level compared to the other treatments. We conclude that setting a detachment level at a greater milk flow rate reduces the duration of overmilking without affecting the amount of milk harvested when applied to cows in mid-lactation during quarter-level milking. We also suggest that the steepness of the decline phase of the milk flow curve might have a larger effect than the actual detachment level on the duration of overmilking.

The objective of the studies reported in this research communication was to investigate differences in composition and enzymatic activities in bulk milk samples provided from Swedish dairy farms with different management systems, i.e. automated (AMS) and conventional milking systems (CMS). A bulk milk sample was collected from each of 104 dairy farms, 51 using AMS and 53 using CMS, located in the same geographical region. Sampling took place within two consecutive days during the indoor period (October). Milk samples were analysed for contents of total fat and protein, free fatty acids (FFA), caseins and whey proteins, somatic cell count (SCC), pH, plasmin and plasminogen derived activities, and total proteolysis. Our results showed a lower protein content and higher SCC in bulk milk from AMS herds compared with milk from CMS herds. Plasmin, plasminogen and total plasmin/ plasminogen derived activities were lower in milk from AMS herds but despite this, total casein and the ß-casein fraction as % of total protein were lower in milk from AMS herds than in milk from herds using CMS. Total proteolysis was higher in milk from AMS herds, suggesting that other proteases than plasmin, e.g. cellular and bacterial proteases, contributed to the degradation of casein. This was supported by a positive correlation between SCC and total proteolysis (P < 0·01), as well as a negative correlation between total proteolysis and ß-casein fraction (P < 0·05). In conclusion, comparing the quality of bulk milk from commercial dairy herds using AMS and CMS, respectively, several differences were observed, suggesting a significant effect from management system.

In order to increase milking efficiency, the effects of two different cluster take-off levels (200 and 800 g/min) and feeding vs. not feeding during milking were tested in a Latin square design study including 32 cows. Milk yield, milking time, milk flow and milking interval were measured and milk samples were analysed for gross composition, sodium and potassium concentration, free fatty acid (FFA) content, milk fat globule (MFG) size, MFG membrane (MFGM) material and fatty acid composition. Residual milk was harvested to evaluate udder emptying. Increasing the take-off level from 200 to 800 g/min at the whole udder level decreased milking time and increased harvest flow. Udder emptying decreased slightly, but there were no effects on milk yield, FFA content or MFGM. There were interactive effects of take-off level and feeding during milking on content of fatty acids C4:0, C6:0, C16:0, C18:3(n-3) and C20:0. Feeding during milking increased milk yield per day and decreased milking interval. Sodium and potassium concentrations in milk were unaffected by treatments, indicating no loss of tight junction integrity. From these results, it is clear that feeding during milking should be used to increase milk yield and improve milking efficiency, regardless of take-off level used, and that the effect of feeding is more pronounced when a low take-off level is used. Feeding seemed to counteract the effects of the low take-off level on milking time and milking interval. Low take-off levels can therefore be used in combination with feeding.

The pulsation ratio of a milking machine affects milk flow and milking time, and has also been reported to influence teat condition and milk somatic cell count (SCC). However, most studies comparing pulsation ratios have been performed on conventional cluster milking (whole-udder level), where effects such as deteriorated teat end condition and increased milk SCC are likely to be caused by over-milking on teats that are emptied faster than the other teats. When the teat cups are detached from each udder quarter separately which can be done in automatic milking systems (AMS), the risk of over-milking, especially in front teats, may be significantly reduced. This study investigated the effects of pulsation ratio on teat end condition, milk SCC, milk yield, milking time and milk flow in an automatic milking system where each udder quarter is milked separately. In total, 356 cows on five commercial farms were included in a split-udder design experiment comparing three pulsation ratios (60:40, 70:30 and 75:25) with the standard pulsation ratio (65:35) during 6 weeks. Pulsation rate was 60 cycles/min and vacuum level 46 kPa. The 70:30 and 75:25 ratios increased peak and average milk flow and the machine-on time was shorter with 75:25, while both peak and average milk flows were lower and machine-on time was longer with the 60:40 ratio. No negative effects on teat condition or milk SCC were observed with any of the pulsation ratios applied during the study. Thus it is possible that increased pulsation ratio can be used to increase milking efficiency in AMS where quarter milking is applied.

A large dataset comprising output from an automatic milking (AM) system between 1999 and 2006 was examined and a total of 172 cow lactation curves and 68 heifer lactation curves were identified for further analysis. Relationships between milking frequency at different stages of lactation and lactation persistency and total lactation yield were determined. Cows had higher peak and total milk yields than heifers, but heifers had higher persistency (defined as the rate of decline in milk yield between days 100 and 300 post calving). Milking frequency did not differ significantly between cows and heifers in early lactation, but thereafter decreased significantly more in cows than in heifers. The effect of milking frequency on yield characteristics was analysed by comparing the highest and lowest quartiles for milking frequency. High milking frequency in early lactation was consistently associated with increased peak yield. High milking frequency averaged across the whole lactation was associated with increased peak yield in both cows and heifers, and with improved lactation persistency in cows only. This resulted in total lactation yield that was 21% greater in the high quartile cows compared with the low.

Dairy herds are expanding and, with increasing numbers of animals in each herd, there is a need for automatic recording of indicators in milk in order to detect mastitis, inflammation of the udder. A number of biomarkers for mastitis have been suggested over the years. Mastitis usually occurs in one of the four udder quarters and since it is now possible to milk each udder quarter separately in automated milking systems, it is important to evaluate the normal variation in the biomarkers at udder quarter level. This study evaluated the normal variations between milkings for some biomarkers in clinically healthy cows, determined by repeated somatic cell count and bacteriological analysis. The biomarkers studied were serum amyloid A (SAA), haptoglobin (Hp), lactate dehydrogenase (LDH), N-acetyl-β-d-glucosaminidase (NAGase) and alkaline phosphatase (AP), parameters that have been suggested as markers for mastitis. Ten cows were monitored on 42 consecutive milking occasions through collection of udder quarter milk samples and representative cow composite milk samples, giving a total of 2100 individual milk samples. Each cow had its individual profile for the concentrations and variations in the parameters analysed. Although there was relatively large variation between cows for the biomarkers analysed, the variation between milkings in clinically healthy quarters within cows was often below 10%. The biomarker with the lowest variation in this study was LDH. The results suggest that comparing quarters within an individual cow can identify deviations from the natural variations between milkings. This could be a valuable tool instead of, or in combination with, a cut-off value for each parameter in order to detect changes in the milk indicating mastitis.

Milking-related release of oxytocin, prolactin, and cortisol was studied following three pre-milking treatments. Six Murrah buffaloes were treated with direct application of milking cluster (O), a 1-min pre-stimulation (M), and combined feeding and pre-stimulation (MF). Machine milk yield, stripping yield and milk composition were recorded. Milk ejection occurred significantly earlier with MF than M and O (P<0·05; 2·50, 5·10 and 6·33 min, respectively). In all treatments, milk ejection occurred with small increases >3–5 ng/l in oxytocin concentration. Increase in oxytocin concentration over a threshold level and milk ejection occurred simultaneously and were closely correlated (r=0·83, P<0·05). There was a positive correlation between total time oxytocin concentration remained elevated over threshold levels and machine yield (r=0·86, P<0·05). For treatment O, milk ejection was inhibited during machine milking, while a marked increase in oxytocin occurred during hand stripping (6 and 16 ng/l, respectively). For treatment M, mean oxytocin concentrations remained unchanged during pre-stimulation but increased during subsequent machine milking and hand stripping (6·38, 18·06 and 12·36 ng/l, respectively). For treatment MF, although there was a 3·6-fold increase during pre-stimulation, oxytocin increased by 10-fold and 3-fold during machine milking and hand stripping, and was significant for machine milking (P<0·05, 17·32, 47·86, 18·13 ng/l, respectively). Milk-ejection-related cortisol release was visible only in treatment MF. For treatments O and M, prolactin concentration increased prior to the increase in oxytocin. The stripping yield was higher, and fat content in the stripping yield significantly lower, for treatment O indicating incomplete milking. Thus buffaloes are easily disturbed even by small changes in milking routines.

The internal arrangement of the mammary gland cavity system, cisternal and alveolar milk fractions and the characteristics of milk ejection were investigated in buffaloes. Twenty-four Murrah buffaloes in three different stages of lactation and of two age groups were used. Continuous ultrasound cross-sections during milk ejection induced by exogenous oxytocin were performed to record the latency period of milk ejection. Buffaloes had small cisterns and the cavity area in the teat and gland regions were not significantly different (P>0·05). The animals had long teat canals (3·1±0·1 cm), longer in the hind than fore quarters. Cisternal milk yield was low (0·17±0·01 kg) and cisternal fraction was only 4·9±0·1% of the total milk. The cisternal area (cm2) was 69·6±4·6, 51·61±4·8 and 26·01±4·8 while the cisternal yield (kg) was 0·32±0·05, 0·18±0·05 and 0·05±0·05 in early, mid and late lactation, respectively. A close correlation (r=0·87, P<0·05) existed between the ultrasound cisternal area and cisternal milk yield. The latency period of induced milk ejection was similar to that reported for cows (25±1 s) and was negatively correlated with milk yield (r=−0·75, P<0·05). Milk ejection occurred shortly after elevated oxytocin concentrations were present. Delayed milk ejection reported earlier in this species must therefore be due to the absence of cisternal milk and delayed oxytocin release. An increase in teat length and circumference at milk ejection was also evident in the ultrasound cross sections.

The aim of the present study was to examine how different types of early interaction between dairy cows and their calves influence milking/suckling-related hormone release in the cows and sucking/bucket-drinking related hormone release in calves. Eighteen cows of the Swedish Red and White breed were studied during the first week after parturition. The cows were machine milked twice daily, and allotted to one of three treatments: [1] cow and calf were kept together and the cow was allowed to suckle the calf for 30 min about 1 h before each milking; [2] cow and calf were kept together and the calf was bucket fed twice daily; and [3] cow and calf were separated immediately after parturition, and the calf was kept in a single box and was bucket fed twice daily. Blood samples were collected around day 7 from both cows and calves. The plasma levels of oxytocin, prolactin, cortisol, gastrin, cholecystokinin (CCK), somatostatin and insulin were analysed. In the cows the levels of oxytocin, prolactin and cortisol were influenced by all three treatments, except for the level of cortisol which did not respond to suckling. The main finding was that the release of oxytocin was significantly greater during suckling compared with machine milking. In the calves, the hormone levels were also influenced by the different milk feeding routines. The plasma concentrations of oxytocin, gastrin, CCK and insulin increased in response to milk ingestion in all treatments. However, during sucking, the increase of oxytocin was significantly greater than during bucket drinking. In addition, a strong correlation between oxytocin and insulin was found in response to sucking. Further, significant increases in prolactin and somatostatin, and a decrease in cortisol were found during sucking. The level of somatostatin also increased in response to bucket feeding when calves were kept separately. During bucket feeding, no significant correlation was found with oxytocin, but strong correlations between the gastrointestinal hormones gastrin, CCK, somatostatin and insulin were seen. Together these data suggest that different hormonal patterns were triggered in the cows by suckling and milking, and in the calves by sucking and bucket drinking. This is further supported by different correlation patterns observed in the calves in response to sucking and bucket feeding. The present findings imply that management routines for cows and calves during the first week after parturition have consequences for the physiology of the animals.

Feeding during milking has been shown to influence milk production, milk flow and milking time as well as the secretion of the pituitary hormones oxytocin and prolactin, and the gastrointestinal hormone somatostatin. However, it is not known whether feeding before or after milking has any effect. The aim of the present study was to investigate how the timing of feeding relative to milking influences milk production and flow, milking time and hormone secretion. The trial was carried out over 9 weeks with 24 cows at varying stages of lactation. Each treatment period lasted for 3 weeks, including one registration week. The cows were fed ad lib. and were exposed to three treatments: feeding 1·5 h before milking (FBM), feeding at exactly the same time as milking (FDM) and feeding 1·5 h after milking (FAM). The most marked treatment effect was observed during morning milking. FDM resulted in higher milk production and higher yields of protein and lactose. FAM produced a lower fat yield and a lower fat content compared with FDM, and a lower lactose content than either FBM and FDM. Milking time was longer when cows were fed during milking, but no significant effects on milk flow were found. The amount of milk collected during the first 2 min of milking was lower when cows were fed after milking. Milking-related oxytocin and somatostatin secretion was lower in FAM than in FDM. The level of prolactin was lower when cows were fed before or after than during milking. More studies are needed to elucidate whether there is a long-term effect on milk production related to the discussed milking routines.