Milking Frequency Research Articles

The effects of milking frequency in early lactation on milk yield, mammary cell turnover, and secretory activity in grazing dairy cows

In dairy cows, short-term changes of milking frequency in early lactation have been shown to produce an immediate and a long-term effect on milk yield in stall-fed cows. The effect is controlled locally within mammary glands and could be a function of either secretory mammary epithelial cell number or activity. To resolve this and determine its applicability in other feed management systems, a unilateral milking frequency experiment was conducted with udder halves of 17 multiparous, pasture-fed dairy cows milked either 4 times (4×) or once a day (1×) for 14d from 5±2d in milk. Mean half-udder milk yield during the treatment period was higher from the 4× compared with 1× udder halves and continued to be higher until 200d in milk once returned to twice a day milking. Mammary biopsies were obtained on d 14 of treatment from both udder halves of 10 cows. Proliferation of mammary cells was higher in 4× udder halves compared with 1×, whereas no difference in apoptosis levels was detected. Abundance of αS1-casein, β-casein, α-lactalbumin, and β-lactoglobulin mRNA was higher in tissue samples from 4× udder halves compared with 1×, whereas lactoferrin mRNA abundance was lower in 4× udder halves. In summary, change in milking frequency during early lactation affects proliferation of mammary cells as well as expression of the major milk protein genes, which both contribute to the observed changes in milk yield during and after unilateral milking frequency treatment.

Design and implementation of a questionnaire to evaluate the dietary quality of school meals

The school canteen provides a substantial proportion of the daily nutritional intake for many children. There are nutritional standards for school meals, however, it is still difficult to assess the dietary quality. To design a questionnaire for assessing the dietary quality of school meals, quickly and easily. A dietary questionnaire (COMES) was designed on the basis of the current recommendations. COMES consist of 15 items related to the food-frequency and to other characteristics of school meals. Then, a longitudinal prospective study was performed in order to analyze, with COMES, 36 school meals of 4 catering companies from Castilla y León during the academic years 2006-2007 to 2010-2011. Differences in dietary quality menus according to the management system of catering companies (in situ vs. transported) were analyzed by using the Mann-Whitney and the Kruskal-Wallis tests. The significance was reached at p <0,05. The frequency intake of meat, dairy and prepared products was higher to the recommended in 97,2%, 94,4% and 27,8% of the analyzed menus, respectively. By contrast, the frequency intake of fish, fruit, legume, and vegetable garnishes were lower to the recommended in 83,3%, 94,4%, 91,7% and 75% of menus, respectively. Nevertheless, recommendations established by our consensus document for school meals are complied for all food groups, except for dairy and fruits. The variety of foods and culinary techniques were appropriate. No significant differences were found in the COMES score according to the management system (p=0,87), although catering system provides higher dietary quality. A new tool to assess quickly and easily the nutritional quality of school meals has been proposed. The assessment of the frequency intake of the most problematic foods for schoolchildren with this scale is much more demanding than the current recommendations. Even so, menus analyzed showed an acceptable quality in terms of variety of foods and culinary techniques, although milk frequency in the menus was excessive at the expense of fresh fruit. On the other hand, the transported system (i.e. catering, both hot and cold-holding) provides menus more consistent with the dietary recommendations.

Temporary alterations to postpartum milking frequency affect whole-lactation milk production and the energy status of pasture-grazed dairy cows

This study investigated the immediate and long-term effects of temporary alterations to postpartum milking frequency (MF) on milk production, body condition score (BCS), and indicators of energy status in pasture-grazed cows supplemented with concentrates. Multiparous Holstein-Friesian cows (n=150) were randomly assigned to 1 of 5 groups at calving: milked twice daily (2×) throughout lactation (control), or milked either once daily (1×) or 3 times daily (3×) for 3 or 6wk immediately postpartum, and then 2× for the remainder of lactation. During wk 1 to 3 postpartum, cows milked 1× produced 15% less milk and 17% less energy-corrected milk (ECM) than cows milked 2×. This immediate production loss increased to 20% less milk and 22% less ECM during wk 4 to 6 postpartum for cows that remained on 1× milking; these animals also produced less than 1× cows switched to 2× milking after 3wk. During wk 8 to 32, when all cows were milked 2×, those previously milked 1× had sustained reductions in milk (−6%) and ECM (−8%) yields, which were not affected by the duration of reduced postpartum MF. In contrast, cows milked 3× postpartum had 7% greater milk yields during wk 1 to 6 compared with 2× controls, irrespective of the duration of increased MF. Milk yields also remained numerically greater (+5%) during wk 8 to 32 in cows previously milked 3×. Nevertheless, yields of ECM were not increased by 3× milking, because of lower milk fat and protein contents that persisted for the rest of lactation. In addition, indicators of cow energy status reflected an increasing state of negative energy balance with increasing MF. Cows milked 1× postpartum had greater plasma glucose and lower plasma nonesterified fatty acid concentrations during the reduced MF, and plasma glucose remained lower for 2wk after cows had switched to 2× milking. Moreover, BCS was improved relative to 2× controls from wk 5 to 6. In contrast, cows milked 3× had lower plasma glucose concentrations, greater plasma nonesterified fatty acid concentrations, and greater BCS loss during wk 1 to 3; however, greater body fat mobilization was not sustained, indicating that additional energy supplements may be required to achieve better milk production responses. In conclusion, temporary 1× milking had lactation-long negative effects on milk and milk component yields but improved cow energy status and BCS, whereas temporary 3× milking immediately increased milk yield but did not improve milk fat and protein yields in pasture-grazed cows.

Economic viability of the third milking in systems of production using closed-circuit mechanical milking

This study aimed to analyze the economic viability of the third milking in production systems using mechanical milking in a closed circuit, aiming to provide technicians and farmers with information to assist them in decision-making. Specifically, it intended: (a) to estimate the cost of one milking; (b) to estimate the cost of the third milking; (c) to develop a mathematical equation to estimate the minimum amount of milk produced with two milkings, from which it would be economically feasible to do the third milking. Data were collected from three dairy farms, from November 2010 to March 2011, keeping a twice-a-day milking frequency, with three data collections in each farm, totalizing nine collections. Considering the average data, it would be feasible to do the third milking if the average milk yield per day of lactating cows in a twice-a-day milking frequency was greater than or equal to 24.43 kg of milk.

Blood Lead Level in Relation to Awareness and Self Reported Symptoms among Gasoline Station Workers in the Gaza Strip

Background: Leaded gasoline is being used in Gaza Strip. Measurements of blood lead level (BLL) and relate it to awareness of gasoline station workers would be helpful in lead protection programs.Purpose: To determine BLL and to assess its relation to awareness and self reported symptoms among gasoline station workers in the Gaza Strip. Methods: A cross section of 72 workers was asked to fill in a questionnaire. BLL was determined by atomic absorption spectrometry. Results: Thirty four (47.2%) workers had BLL&gt;10 ?g/dl. The mean BLL was inversely related to the education level (p=0.001). Workers worked d”5 years in the station had lower BLL than those worked &gt;5 years (7.8±5.6 v 12.5±5.8 ?g/dl, p=0.004). The variation in workers’ knowledge by their BLL was not significant. Higher BLL was generally found in workers who did not practice protective measures compared to those who did, with significant difference for respiratory mask (12.4±5.9 v 5.6±1.6 ?g/dl, p=0.001), gloves (13.1±6.0 v 8.6±4.9 ?g/dl, p=0.001) and frequent milk drink (13.5±6.0 v 9.3±5.2 ?g/dl, p=0.018). Higher BLL was also found in workers who reported symptoms than in those who did not, with significant differences for irritability (12.4±5.4 v 9.2±5.6 ?g/dl, p=0.031), headache (12.2±5.8 v 9.0±5.9 ?g/dl, p=0.046), concentration difficulties (12.9±5.8 v 9.4±5.6 ?g/dl, p=0.015), sleep disturbances (14.1±5.8 v 8.9±5.0 ?g/dl, p=0.001) and hypertension (13.3±6.4 v 8.1±2.9 ?g/dl, p=0.001). Conclusions: High BLL was associated with low education level, long work duration, lack of protective measures and increase self reported symptoms. Educational programs on protective measures practices are recommended.DOI: http://dx.doi.org/10.3329/jom.v14i2.19658 J Medicine 2013, 14(2): 135-142

Time-budget constraints for cows with high milking frequency on farms with automatic milking systems

Adequate lying times and feed consumption are essential for the welfare and performance of dairy cows. The time budget of cows housed in barns with an automatic milking system (AMS) might be constrained in several ways. Cows with a high milking frequency might also have to visit the AMS at night, possibly interfering with their night-time lying behavior. Moreover, competition for access to the AMS might cause some cows to spend more time waiting in front of the milking unit, resulting in a lower milking frequency. In the present study, the individual total duration of stay and time spent per visit in the feeding, lying and waiting area, as well as lying behavior, was therefore investigated in the daytime and throughout the night in relation to milking frequency.A total of 138 focal cows (day of lactation: 1–200) housed on 4 Swiss working farms with an AMS were automatically tracked for 48h. Individual lying times were recorded over 7 days with data loggers. The daily milking frequency was calculated from the AMS records and included as a continuous explanatory variable in linear mixed-effects models.Time spent in the waiting area at night increased with increasing milking frequency. In addition, cows with a relatively high milking frequency had shorter daytime lying bouts, and spent less time in the lying area per visit during the daytime as well as at night. The same individuals also visited the feeding area for shorter times during the day, and on average remained longer per visit in the waiting area at night. The daily time budget of cows with a relatively low milking frequency was not adversely affected.Cows with a relatively high milking frequency may face some trade-offs in their time-budget allocation, since the increased time spent by them in the waiting area at night as well as their shorter lying bouts might affect their welfare, health and performance. Nevertheless, the overall daily time budget for lying and feeding, and hence the welfare of cows with both a relatively high or low milking frequency, suffered no obvious adverse effects.

Intakes of Dairy Products and Calcium and Obesity in Korean Adults: Korean National Health and Nutrition Examination Surveys (KNHANES) 2007-2009

BackgroundThe possible effects of dairy product intake against obesity have been suggested in animal studies; however, the association is still not well established in epidemiological studies. Few studies in Asian countries with relatively low intake of dairy products exist.ObjectiveWe investigated the association between dairy products and calcium intake and obesity in Korean population with relatively low intake of dairy products.Subjects and MethodsOur study population consisted of adults (n = 7173) aged 19–64 among participants of the 2007, 2008 and 2009 Korean National Health and Nutrition Examination Survey who had not made any attempt of intentional weight loss. Dietary intake data from food frequency questionnaire (FFQ) and 24-hour recall were used. Dairy products included milk and yogurt in the FFQ. Obesity was defined as BMI≥25 kg/m2.ResultsHigher frequency of dairy product intake was associated with a reduced prevalence of obesity (OR = 0.63; 95% CI = 0.45–0.89 for ≥2 times/day vs. ≤1 time/month; p for trend = 0.003) using the intake data from FFQ. Similarly, high frequency of milk or yogurt intake had an inverse association with obesity. The association between milk and yogurt intake and obesity was similar when the intake from 24-hour recall was examined. Higher calcium intake from dairy products as well as total dietary calcium intake was associated with a decreased prevalence of obesity (OR = 0.83; 95% CI = 0.71–0.98 for highest vs. lowest quintile of dairy calcium intake; p for trend = 0.02, OR = 0.78; 95% CI = 0.64–0.94 for highest vs. lowest quintile of total calcium intake; p for trend = 0.04). The associations appeared to be stronger in women than in men.ConclusionThese results suggest that high consumption of dairy products is associated with a lower prevalence of obesity and that calcium in dairy products may be one of the components contributing to the association. Further longitudinal studies are warranted to replicate our findings.

Genetic parameters for rennet- and acid-induced coagulation properties in milk from Swedish Red dairy cows

Milk coagulation is an important processing trait, being the basis for production of both cheese and fermented products. There is interest in including technological properties of these products in the breeding goal for dairy cattle. The aim of the present study was therefore to estimate genetic parameters for milk coagulation properties, including both rennet- and acid-induced coagulation, in Swedish Red dairy cattle using genomic relationships. Morning milk samples and blood samples were collected from 395 Swedish Red cows that were selected to be as genetically unrelated as possible. Using a rheometer, milk samples were analyzed for rennet- and acid-induced coagulation properties, including gel strength (G′), coagulation time, and yield stress (YS). In addition to the technological traits, milk composition was analyzed. A binary trait was created to reflect that milk samples that had not coagulated 40min after rennet addition were considered noncoagulating milk. The cows were genotyped by using the Illumina BovineHD BeadChip (Illumina Inc., San Diego, CA). Almost 600,000 markers remained after quality control and were used to construct a matrix of genomic relationships among the cows. Multivariate models including fixed effects of herd, lactation stage, and parity were fitted using the ASReml software to obtain estimates of heritabilities and genetic and phenotypic correlations. Heritability estimates (h2) for G′ and YS in rennet and acid gels were found to be high (h2=0.38–0.62) and the genetic correlations between rennet-induced and acid-induced coagulation properties were weak but favorable, with the exception of YSrennet with G′acid and YSacid, both of which were strong. The high heritability (h2=0.45) for milk coagulating ability expressed as a binary trait suggests that noncoagulation could be eliminated through breeding. Additionally, the results indicated that the current breeding objective could increase the frequency of noncoagulating milk and lead to deterioration of acid-induced coagulation through unfavorable genetic associations with protein content (0.38) and milk yield (−0.61 to −0.71), respectively. The outcome of this study suggests that by including more detailed compositional traits genetically associated with milk coagulation or by including milk coagulation properties directly within the breeding goal, it appears possible to breed cows that produce milk better suited for production of cheese and fermented products.

The mammary gland in small ruminants: major morphological and functional events underlying milk production--a review.

The importance of small ruminants to the dairy industry has increased in recent years, especially in developing countries, where it has a high economic and social impact. Interestingly and despite the fact that the mammary gland is the specialised milk production organ, very few authors studied the modifications occurring in the mammary gland through the lactation period in production animals, particularly in the small ruminants, sheep (Ovis aries) and goat (Capra hircus). Nevertheless, understanding the different mammary gland patterns throughout lactation is essential to improve dairy production. In addition, associating these patterns with different milking frequencies, lactation number or different diets is also of high importance, directly affecting the dairy industry. The mammary gland is commonly composed of parenchyma and stroma, which includes the ductal system, with individual proportions of each changing during the different periods and yields in a lactation cycle. Indeed, during late gestation, as well as during early to mid-lactation, mammary gland expansion occurs, with an increase in the number of epithelial cells and lumen area, which leads to increment of the parenchyma tissue, as well as a reduction of stroma, corresponding macroscopically to the increase in mammary gland volume. Throughout late lactation, the mammary gland volume decreases owing to the regression of the secretory structure. In general, common mammary gland patterns have been shown for both goats and sheep throughout the several lactation stages, although the number of studies is limited. The main objective of this manuscript is to review the colostrogenesis and lactogenesis processes as well as to highlight the mammary gland morphological patterns underlying milk production during the lactation cycle for small ruminants, and to describe potential differences between goats and sheep, hence contributing to a better description of mammary gland development during lactation for these two poorly studied species.

Short-term effects of milking frequency on milk yield, milk composition, somatic cell count and milk protein profile in dairy goats.

Goats in Canary Islands are milked once a day by tradition, but in most countries with high technology on farms, goats are milked twice a day, which is known to improve milk yield. Therefore it is important to know whether the increase of milking frequency can improve the production without impairing milk quality. The objective of this study was to investigate the short term effects of three milking frequencies on milk yield, milk composition, somatic cell count (SCC) and milk protein profile in dairy goats traditionally milked once a day. Twelve Majorera goats in early lactation (48±4 d in milk) were used. During a 5-week period, goats were milked once a day (X1) in weeks 1 and 5, twice a day (X2) in weeks 2 and 4, and three times a day (X3) in week 3. Milk recording and sampling were done on the last day of each experimental week. Milk yield increased by 26% from X1 to X2. No differences were obtained when goats were switched from X2 to X3, and from X3 to X2. The goats recovered the production level when they returned to X1. Different patterns of changes in the milk constituents due to the milking frequency effect were observed. Fat percentage increased when switched from X1 to X2, then decreased from X2 to X3, and from X3 to X2, whereas it did not show significant differences from X2 to X1. Milking frequency did not affect the protein and lactose percentages. SCC values were unaffected when goats were milked X1, X2 and X3, but then they increased slightly when milking frequency was returned to X2 and X1. Finally, quantitative analysis showed an increase in intensities of milk protein bands from X1 to X2, but the intensities of casein bands (α(S1)-CN, α(S2)-CN, β-CN, κ-CN) and major whey proteins (α-La, β-Lg) decreased from X2 to X3.

Milk Consumption and Progression of Medial Tibiofemoral Knee Osteoarthritis: Data From the Osteoarthritis Initiative

Milk consumption has long been recognized for its important role in bone health, but its role in the progression of knee osteoarthritis (OA) is unclear. We examined the prospective association of milk consumption with radiographic progression of knee OA. In the Osteoarthritis Initiative, 2,148 participants (3,064 knees) with radiographic knee OA and dietary data at baseline were followed up to 12, 24, 36, and 48 months. Milk consumption was assessed with a Block Brief Food Frequency Questionnaire completed at baseline. To evaluate progression of OA, we used quantitative joint space width (JSW) between the medial femur and tibia of the knee based on plain radiographs. The multivariate linear models for repeated measures were used to test the independent association between milk intake and the decrease in JSW over time, while adjusting for baseline disease severity, body mass index, dietary factors, and other potential confounders. We observed a significant dose-response relationship between baseline milk intake and adjusted mean decrease of JSW in women (P = 0.014 for trend). With increasing levels of milk intake (none, ≤3, 4-6, and ≥7 glasses/week), the mean decreases of JSW were 0.38 mm, 0.29 mm, 0.29 mm, and 0.26 mm, respectively. In men, we observed no significant association between milk consumption and the decreases of JSW. Our results suggest that frequent milk consumption may be associated with reduced OA progression in women. Replication of these novel findings in other prospective studies demonstrating the increase in milk consumption leads to delay in knee OA progression are needed.

Factors That Affect Body Mass Index of Adults

The aim of the study is to determine the factors that contribute to the body mass index (BMI) of adults and evaluate the eating habits of the individuals. The study was conducted on 498 adults whose ages were ranging from 20 to 85 (39.1±14.9 year). The data were collected using a questionnaire form that consisted of questions concerning general characteristics of individuals, frequency of food consumption and eating habits. Food types in the food consumption frequency were grouped together according to Nutrition Guide for Turkey. Body weights and heights of the individuals were measured. BMI of the 55% of the individuals participated in the study is 25 or higher than 25. The average BMI of the individuals differs according to age, educational, marital, smoking status, parity and sleep duration (p 0.05). A statistically significant correlation was found between BMI of participants and their habit of eating at night, appetite and use of sweeteners (p<0.05). Individuals with BMI<25 were determined to have a lower consumption frequency of milk and dairy products and fruits-vegetables monthly (p<0.05). In this study; age, educational, marital, smoking status and sleep duration were found to affect body mass index. Analysis of genetic and environmental factors affecting obesity is required to reveal the factors affecting body mass index of individuals more clearly.

Differences in Voluntary Cow Traffic between Holstein and Illawarra Breeds of Dairy Cattle in a Pasture-based Automatic Milking System.

Automatic milking systems (AMS) rely upon voluntary cow traffic (the voluntary movement of cattle around a farm) for milk harvesting and feed consumption. Previous research on conventional milking systems has shown differences between dairy cow breeds for intake and milk production, however, the ability to manipulate voluntary cow traffic and milking frequency on AMS farms through breed selection is unknown. This study investigated the effect of breed (Holstein Friesian versus Illawarra) on voluntary cow traffic as determined by gate passes at the Camden AMS research farm dairy facility. Daily data on days in milk, milk yield, gate passes and milking frequency for 158 Holstein Friesian cows and 24 Illawarra cows were collated by month for the 2007 and 2008 years. Illawarra cows had 9% more gate passes/day than Holstein cows over the duration of the study; however, the milking frequency and milk yield of both breeds were similar. Gate passes were greatest for both breeds in early lactation and in the winter (June to August) and summer (December to February) seasons. These findings highlight an opportunity to translate increased voluntary cow movement associated with breed selection into increased milking frequencies, milk production and overall pasture-based AMS performance.

Gene expression in liver and adipose tissue is altered during and after temporary changes to postpartum milking frequency

Short-term changes to milking frequency can alter the metabolic status of dairy cows depending on the duration, magnitude, and stage of lactation at which the milking frequency changes occur. Additionally, effects of altered milking frequency that are subsequent to cows returning to a normal twice-daily (2×) milking regimen are not well established. This study tested the hypothesis that plasma concentrations of key hormones and metabolites and transcription of genes involved in the somatotropic axis and lipid metabolism would be altered in liver and subcutaneous adipose tissue from cows milked with different frequencies. Multiparous Holstein-Friesian dairy cows were allocated to 2× milking for the whole lactation, or once-(1×) or 3 times-(3×) daily milking for 3 or 6wk, immediately postpartum, and then 2× milking for the remainder of the lactation. Liver and subcutaneous fat were biopsied at wk 1 (liver only), 3, 6, and 9 postpartum, and transcription of genes involved in the somatotropic axis and lipid metabolism were measured. At wk 3, cows milked 3× had lower hepatic expression of growth hormone receptor (GHR1A) compared with cows milked 2× or 1×, and lower IGF1 expression compared with cows milked 1×, indicating greater uncoupling of the somatotropic axis. At wk 6, reduced transcription of total GHR and GHR1B occurred in the adipose tissue of cows milked 3×. Cows milked 1× had greater transcription in adipose tissue of lipogenesis genes at wk 3 and 6, and lipolysis genes at wk 6, compared with cows milked 2×, indicating a period of increased fatty acid storage, followed by increased fatty acid reesterification. At wk 9, cows previously milked 3× for 6wk maintained lower transcription of genes involved in lipogenesis, lipolysis, and ketolysis in adipose tissue compared with cows milked 2×, indicating that the effects of 3× milking persist for at least 3wk after switching to 2× milking. Results indicate that alterations to milking frequency affect the transcription of genes involved in lipid mobilization and storage, enabling the animal to manage the energy demands associated with the change in milk production. Some of these gene transcription changes were maintained in cows previously milked 3×, indicating that the adipose tissue gene expression changes were still required even after 3wk of the less-demanding 2× milking regimen.

Evaluation of Changing Daily Milking Frequency on Milk Yield and Total Solids from Boran Breeds Crossed with Holstein Frisians at Hawassa, South Ethiopia

The study was conducted at Hawassa University dairy farm for three consecutive weeks with the objective to evaluate the effect of changing milking frequency from 2X to 3X daily on yield and total solids of milk using half udder technique. Five cows (2 nd and greater lactation) were selected from the farm. Their udder was divided diagonally and assigned randomly to 2X and 3X milking treatments. During the experiment all cows were managed alike and fed roughage free choice and concentrate feeds controlled. The results of the study indicated that, the quarters milked 3X daily produced significantly (P<0.05) more milk yield (12.5%) than that of 2X daily, and there was no significant difference (P<0.05) between the treatments in ash and dry matter percentage, although DM and ash percentages for the quarters milked 3X daily were numerically lower. The amount of total solids in 3X milking was increased by about 8.28 kg due to the increased yield. Therefore, it can be concluded that 3X milking is highly productive mainly in terms of yield, however, the management and production systems of the farm have to be improved to maintain the production advantage.

Factors affecting reproductive performance of dairy cows in a pasture-based, automatic milking system research farm: a retrospective, single-cohort study

A retrospective, single-cohort study was conducted to identify production and health factors associated with reproductive performance in a pasture-based, automatic milking system research farm. The calving system of this herd shifted from split calving to year-round calving gradually during the study period. Data from 365 cows with 798 lactations were analysed. Reproductive outcome variables of interest were intervals from calving to first oestrus, to first insemination, and to conception, as well as number of inseminations per conception, probability of submission for insemination by 80 days in milk, probability of conception by 100 days in milk and probability of conception at first insemination. Production factors (milk yield and its composition, milking frequency), record of periparturient disease, parity and season of calving were considered as predictor variables. The associations between predictor and outcome variables were assessed by multivariable linear regression, logistic regression and survival analyses, for quantitative, binary and time-to-event outcomes, respectively. Average milk yield and milking frequency during 100 days in milk were not significantly associated with any of the reproductive measures. The likelihood of conception by 100 days in milk decreased gradually with year of automatic milking system commissioning. Cows calved in autumn were 43% (hazard ratio 1.43, P &lt; 0.05) more likely to conceive than cows calved in summer. Multiparous cows were more likely (P &lt; 0.05) to be recorded for oestrus than primiparous cows. Twinning was negatively associated with the reproductive outcomes measured in the automatic milking system research herd. Milk yield and milking frequency during 100 days in milk had no effect on reproductive measures in the pasture-based, automatic milking system research herd.

Effect of low light intensity at night on cow traffic in automatic milking systems

Several studies have shown benefits of long-day (16 h) photoperiod in lactating dairy cows, but have not identified a suitable light intensity for the dark hours. It is known that the locomotion pattern of dairy cows is altered at low light intensities and this may translate to reduced cow traffic and milking frequency, which would have a negative impact on system productivity. However, it is also recognised that a significant disturbance of rest may have a negative impact on the health and productivity of high-yielding dairy cows. This study examined the effect of three different night-time light intensities (LOW: 11 ± 3, MED: 33 ± 1 and HIGH: 74 ± 6 lx) on number of gate passages, milking frequency and milk yield in dairy cows in automatic milking systems. The study was conducted in Sweden during the winter of 2012–13 and the treatments were applied in a crossover design to three herds with an automatic milking system. Minimum day time light intensity was 158 lx. Data on gate passages, milking frequency and milk yield for 172 ± 49 (mean ± s.d.) cows during the last 22 days of each 34-day study period were analysed for treatment differences and differences in daily distribution over 24 h, during day time and night time. Light intensity did not affect total number of gate passages per 24-h period and cow, but number of gate passages per hour and cow was in all treatments lower during night time than during day time. Milking frequency was increased in MED compared with both HIGH and LOW (P &lt; 0.05). Milk yield decreased with reduced light intensity, and differed significantly between HIGH and LOW treatments, 45 ± 1 kg and 44 ± 1 kg, respectively (P &lt; 0.001). Our conclusion is that reducing light intensity to 11 lx at night time does not affect cows’ general activity as gate passages remained the same for all treatments. However, milk yield decreased with reduced light intensity, which might be related to a lower feed intake. We argue that providing night light for dairy cows, as required by many welfare acts, might be related to production level rather than welfare aspects and that the recommendations should be revised.

Pattern and predictors of dairy consumption during adolescence.

We aimed to prospectively assess dairy intake among adolescents, and determine the predictors of adequate dairy consumption during adolescence. 634 Sydney schoolchildren (351 girls and 283 boys) who had dietary data at both age 12 and 17 were included for analyses. Dairy consumption was assessed from validated semi-quantitative food frequency questionnaires. At age 12, mean total dairy intake was 1.62 serves/day which decreased to 1.40 by age 17 (p<0.0001). Mean serves/day of milk decreased from 1.11 to 0.92 during adolescence. Moreover, 90% of the decrease in serves/day of total dairy was due to reduced milk consumption. At age 12, 8.5% of children consumed >=3.5 serves/day of total dairy and this decreased to 6.2%, 5 years later at age 17 (p=0.001). A lower proportion of girls compared with boys consumed >=3 serves/day of total dairy at both ages 12 (p=0.005) and 17 (p=0.01). Participants with tertiary qualified parents at baseline were 85% more likely to have intakes of the dairy food group above the median during the 5 years, OR 1.85 (95% CI 1.18-2.91). Frequent flavored milk consumption (>=2 serves/week) at baseline was associated with ~5-fold greater likelihood of maintaining intakes of dairy foods above the median during adolescence. Dairy food consumption decreased significantly during adolescence, driven primarily by a decrease in milk consumption. Most adolescents did not meet national recommended guidelines for the dairy food group intake. These findings highlight the need for further research into intervention strategies aimed at sustaining dairy consumption.

The expression of genes involved in hepatic metabolism is altered by temporary changes to milking frequency

Changes to milking frequency (MF) affect the metabolic and energetic status of dairy cows. However, the duration of altered MF necessary to modify hepatic transcription during early lactation is less clear. Additionally, long-term responses to short-term alterations in MF have not been established. Holstein-Friesian dairy cows (n=120) were allocated to 3 or 6 wk of either once-daily (1×) or thrice-daily (3×) milking, immediately postpartum. Following treatment, cows were switched to twice-daily (2×) milking. These 4 treatment groups were compared with cows milked 2× (n=30) for the whole lactation. Liver tissue was collected by biopsy at 1, 3, 6, and 9 wk postpartum from 12 cows per treatment, RNA was extracted, and transcript abundance of genes involved in hepatic metabolism was quantified. Milking frequency altered the expression of most of the genes measured; however, we observed no effects caused by the length of time on the alternative milking frequency and no interactions between MF and length. During the MF treatment, mRNA expression of some, but not all, genes involved in gluconeogenesis (G6PC, PCK1), fatty acid β-oxidation (CPT1A, CPT2), ketogenesis (HMGCS2), lipid transport (APOA1), and lipolysis (PNPLA2) were lower for cows milked 1× and plasma glucose and insulin concentrations were greater. Cows milked 3× had reduced mRNA expression for some of the genes involved in fatty acid synthesis (ACACA) and lipid transport (APOB) and had greater plasma NEFA concentrations at wk 1. At 9 wk postpartum, expression data indicated that cows previously milked 3× had a greater capacity for gluconeogenesis (PCK1), ketogenesis (HMGCS2), and urea cycling (ASL, CPS1) and lower glucose concentrations than cows previously milked 1×, because some of the genes involved in these processes were still altered. Milking cows 1× relative to 2×, however, did not result in significant carryover effects on the expression of the genes measured in this study, indicating that metabolic changes are not sustained beyond the period of reduced MF. Changes to MF altered the hepatic response during early lactation; however, this was not dependent on the duration of MF change. Although we observed only minimal carryover effects on hepatic metabolism from short periods of reduced MF postpartum, there may be long-term effects on urea cycling (ASL, CPS1) and ketogenesis (HMGCS2) when 3× milking occurs immediately postpartum.

Effect of premilking stimulation and milking frequency on milking-induced prolactin release in lactating dairy cows

Four experiments were conducted to investigate the factors controlling prolactin (PRL) release at milking. Each experiment used 9 dairy cows in mid-lactation in a 3 × 3 Latin square design. Experiment 1 evaluated the effect of premilking stimulation. The milking unit was attached after 0, 20, or 120 s of manual stimulation. Blood samples were collected from 20 min before to 60 min after milking-unit attachment. The peak value and total PRL release (area under the curve) were not affected by the treatments, but the 120-s stimulation hastened PRL release. Stimulation (20 or 120 s) increased the β-endorphin peak value (P = 0.02), but the magnitudes of PRL and β-endorphin releases were not correlated. Experiment 2 evaluated the effect of milking frequency. Cows were milked twice, at 7 AM and 7 PM; 3 times, at 7 AM, 1 PM, and 7 PM; or 7 times, at 7 AM, 9 AM, 11 AM, 1 PM, 3 PM, 5 PM, and 7 PM. The amount of PRL released at the 7 PM milking decreased as the number of milkings increased (P < 0.01), and peak values were smaller with 7 milkings than with 2 and 3 milkings (P < 0.05). Beta-endorphin release was not affected by milking frequency and not correlated with the magnitude of PRL release. Experiment 3 evaluated the effect of manual stimulation between milkings on milking-induced PRL release. Cows received no stimulation; 5 stimulations (5 min each), at 9 AM, 11 AM, 1 PM, 3 PM, and 5 PM; or 1 stimulation at 5 PM. Manual stimulation reduced (P < 0.5) the amount of PRL released and the maximum PRL concentration at the 7 PM milking, but no difference were found between 1 and 5 stimulations. Manual stimulation did not affect the amount of cortisol released but did impair milk ejection. Experiment 4 evaluated the effect of milking frequency on the PRL release induced by manual stimulation. Cows were milked at 7 AM only; at 7 AM, 9 AM, 11 AM, 1 PM, 3 PM, and 5 PM; or at 7 AM and 5 PM. All cows then received manual stimulation at 7 PM. Milking every 2 h or once 2 h before manual stimulation reduced the amount of PRL released and the maximum PRL concentration but did not affect cortisol release. In conclusion, the length of premilking stimulation has no significant effect on milking-induced PRL release, but increasing milking frequency reduces the amount of PRL released at milking. This effect is due not to the number of milkings or the amount of milk harvested during the milking but to the interval since the preceding milking.