Short communication: Circulating serotonin is related to the metabolic status and lactational performance at the onset of lactation in dairy cows

Serotonin (5-hydroxytryptamine, 5-HT) affects many physiological functions because it is involved in glucose and lipid metabolism, calcium homeostasis, and regulation of lactation in dairy cows. This study aimed to examine physiological differences in serum 5-HT concentrations (high vs. low) and their association with metabolic status and milk production at the onset of lactation. Twelve multiparous Holstein dairy cows were milked within 4 h of calving, and blood and milk samples were collected at the first 6 subsequent milkings after parturition and at the evening milkings on d 5, 8, 10, and 14. Cows were retrospectively divided into 2 groups (6 cows/group): low serum 5-HT (LSS) and high serum 5-HT (HSS) according to their calculated areas under the curve (AUC) for serum 5-HT for the entire experimental period (cut-off: 46,000 ng/mL × 324 h). Concentrations of 5-HT, free fatty acids (FFA), β-hydroxybutyrate (BHB), glucose, calcium, and IGF-1 were measured in blood. Milk was analyzed for fat, protein, lactose, and 5-HT concentrations. Milk yield was recorded at each milking and energy-corrected milk yield was calculated. Serum 5-HT concentrations were higher in HSS than in LSS [AUC (ng/mL × 324 h): 57,830 ± 4,810 vs. 25,005 ± 5,930]. The amount of energy-corrected milk was lower in HSS than in LSS. The HSS group produced less colostrum and had decreased milk yield, specifically during the first 6 milkings. Concentrations of FFA, BHB, and glucose in plasma did not differ between groups. Concentrations of IGF-1 in serum were elevated in HSS compared with LSS throughout the experiment. Total circulating calcium concentrations in serum tended to be higher in HSS than in LSS. Milk fat and protein yields were decreased in HSS compared with LSS. Milk 5-HT decreased overall during the experimental period, with LSS maintaining higher 5-HT concentrations than HSS until d 14 of lactation. In conclusion, cows with high serum 5-HT concentrations showed a reduced metabolic load at the onset of lactation, concomitantly lower milk yield, and a reduced energy output via milk.     

Inhibition of oxytocin release and milk let-down in postpartum primiparous cows is not abolished by naloxone

About 10% of primiparous cows have no milk ejection during the first milkings after delivery. Therefore, 17 Brown Swiss dairy cows in their first lactation were used to evaluate the extent of disturbed milk let-down and the corresponding oxytocin (OT) plasma values in the 1st 5 days after delivery. The first milking was 9-22 h after parturition and served for classification of the cows to groups with inhibited (INH), bimodal (BIMO), or normal (NOR) milk let-down. The OT plasma levels before the start of manual teat stimulation and machine milking were comparably high during the first milking especially in NOR and BIMO cows. Ten minutes before the second milking (M2), 300 mg of the opioid antagonist naloxone was injected to test whether the disturbance was affected by the action of endogenous opioids on the neurohypophysis. The milk yield was not influenced by the naloxone treatment, and the INH cows had milk ejection only after a vaginal stimulation. Afterwards, the cows were milked twice every day, until the milk let-down and the OT release were unaffected (equal to control milking). Then, at the next milking, the cows were injected with 300 mg morphine 10 min before milking. The central OT release in response to manual teat stimulation and machine milking was completely blocked in all cows, but a vaginal stimulation was able to abolish this block, at least partially, in 16 cows. Thus, morphine produced a milk let-down characteristic as in the INH cows during the first three milkings. For the following milking, the cows were pre-treated with 300 mg naloxone (-15 min) plus 300 mg morphine (-10 min) before milking. The OT release and the milk yields were unaffected when compared with the control milking. This experiment demonstrates that exogenous opioids can affect the central release of OT in a naloxone-reversible manner even very soon after parturition. However, endogenous opioids are probably not the main mediators of disturbed central OT release and alveolar milk ejection in post-partum primiparous cows.     

Bovine immunoglobulin G, beta-lactoglobulin, alpha-lactalbumin and serum albumin in colostrum and milk during the early post partum period.

Colostrum and milk samples from 60 Holstein-Friesian cows were analysed for concentrations and yields of immunoglobulin G (IgG), beta-lactoglobulin (beta-lg), alpha-lactalbumin (alpha-la) and serum albumin (BSA) throughout the first 16 milkings post partum (8 d of lactation) using a single radial immunodiffusion assay. Concentrations (mg/ml, means +/- SD) at first milking were IgG 59.8 +/- 28.5, beta-lg 14.3 +/- 4.6, alpha-la 2.04 +/- 0.6, BSA 1.21 +/- 0.44. Large variations were recorded for IgG concentrations (15.3-176.2 mg/ml) and yields (0.2-925 g). Cows in their first lactation produced significantly lower concentrations and yields of colostral IgG than cows in later lactations. A colostral yield of IgG below the 100 g required to prevent calf hypo-gamma-globulinaemia was found in 18.3% of the cows. The concentrations of IgG, beta-lg and BSA dropped abruptly in subsequent milkings and alpha-la concentration decreased slowly. The mean IgG concentration was < 2 mg/ml after eight milkings and < 1 mg/ml after fifteen milkings. However, IgG concentration did not differ significantly, at the 1% level, during milkings 11-15. The results were tabulated to make it possible to calculate the excess of whey proteins that would be obtained if early milks were illegally added to the milk supply.     

Individual differences in behavioral and physiological responsiveness of primiparous dairy cows to machine milking

An experiment was performed in primiparous dairy cows (n = 23) to examine consistency of individual differences in reactivity to milking, and correlations between measures of behavior, physiology, and milk ejection. Responsiveness to milking was monitored during the first machine milking, on d 2 of lactation, and during milkings on d 4 and 130 of lactation. Measurements included kicking and stepping behavior, plasma cortisol and plasma oxytocin, heart rate, milk yield, milking time, milk flow rate, and residual milk obtained after administration of exogenous oxytocin. With repeated early lactation milkings, residual milk and the incidence of abnormal milk flow curves decreased. On d 130 of lactation all heifers exhibited normal milk ejection. Except for higher plasma cortisol concentrations on d 2, all measures were consistent over time between d 2 and 4 of lactation as indicated by significant rank correlations. Individual differences in the behavioral response to udder preparation were consistent over time between early lactation milkings and d 130 of lactation. Residual milk, milk yield, maximum milk flow rate, plasma oxytocin and heart rate during udder preparation were similarly interrelated on d 2 and 4 of lactation. High heart rate responses on d 2 and 4 were associated with enhanced inhibition of milk ejection. In contrast, behavior recorded during the milking process was unrelated to ease of milk removal. Our results indicate that milking at the beginning of lactation may be stressful to some heifers, to the extent that milk ejection is inhibited, but less disturbing to others. The existence of consistent behavioral and physiological responses in the present study suggests that responsiveness of dairy heifers to milking is mediated by stable animal characteristics.     

Covariance among milking frequency, milk yield, and milk composition from automatically milked cows

Automatic milking systems allow cows voluntary access to milking and concentrates within set limits. This leads to large variation in milking intervals, both within and between cows, which further affects yield per milking and composition of milk. This study aimed to describe the degree to which differences in milking interval were attributable to individual cows, and how this correlated to individual differences in yield and composition of milk throughout lactation. Data from 288,366 milkings from 664 cow-lactations were used, of which 229,020 milkings had milk composition results. Cows were Holsteins, Red Danes, and Jerseys in parities 1, 2, and 3. Data were analyzed using a linear mixed model, with cow-lactation as a random effect and assuming heterogeneous residual variance over the lactation. Cow-lactation variance was fitted using linear spline functions with 5 knot-points. Residual variance was generally greatest in early lactation and declined thereafter. Accordingly, animal-related variance tended to increase with progression of lactation. Milking frequency (the reverse of milking interval) was found to be moderately repeatable throughout lactation. Daily milk yield expressed per milking was found to be highly repeatable in all breeds, with the highest values occurring by the end of lactation. Fat percentage had only moderate repeatability in early to mid lactation but increased toward the end of lactation. Individual level correlations showed that cows with higher milking frequency also had greater yields, but had lower fat percentage. Correlations were slightly weaker in very early lactation than in the remaining parts of lactation. We concluded that individual differences exist among cows milked automatically. Cows with higher yields are milked more often and have lower fat content in their milk.     

Effects on milk yield of milking interval regularity and teat cup attachment failures with robotic milking systems

A database consisting of 35291 milking records from 83 cows was built over a period of 10 months with the objectives of studying the effect of teat cup attachment failures and milking interval regularity on milk production with an automated milking system (AMS). The database collected records of lactation number, days in milk (DIM), milk production, interval between milkings (for both the entire udder and individual quarters in case of a teat cup attachment failure) and average and peak milk flows for each milking. The weekly coefficient of variation (CV) of milking intervals was used as a measure of milking regularity. DIM, milking intervals, and CV of milking intervals were divided into four categories coinciding with the four quartiles of their respective distributions. The data were analysed by analysis of variance with cow as a random effect and lactation number, DIM, the occurrence of a milking failure, and the intervals between milkings or the weekly CV of milking intervals as fixed effects. The incidence of attachment failures was 7.6% of total milkings. Milk production by quarters affected by a milking failure following the failure was numerically greater owing to the longer interval between milkings. When accounting for the effect of milking intervals, milk production by affected quarters following a milking failure was 26% lower than with regular milkings. However, the decrease in milk production by quarters affected by milking failures was more severe as DIM increased. Average and peak milk flows by quarters affected by a milking failure were lower than when milkings occurred normally. However, milk production recovered its former level within seven milkings following a milking failure. Uneven frequency (weekly CV of milking intervals >27%) decreased daily milk yield, and affected multiparous more negatively than primiparous cows.     

Feeding patterns and performance of cows in controlled cow traffic in automatic milking systems

Two groups of dairy cows monitored from 3 to 19 wk postpartum were subjected to 2 different cow traffic routines in an automatic milking system with control gates and an open waiting area. Using different time settings in the control gates, the groups of cows were separated by average milking frequency; cows in the high milking frequency routine had a minimum of 4 h between milkings (MF₄) and were milked 3.2 ± 0.1 times daily, whereas cows in the low milking frequency routine had at least 8 h between milkings (MF₈) and were milked 2.1 ± 0.1 times daily. Cows in the 2 groups were switched to the opposite milking frequency control for wk 18 and 19. The increased milking frequency resulted in a higher milk yield of about 9% through 16 wk of early lactation Although the higher milk yield was not significant when measured as energy-corrected milk, significant interactions of milking frequency and study period for milk yield and energy-corrected milk yield were consistent with a yield response when cows were milked more frequently. Meal criteria estimated for each individual cow were used to group feeding visits into meals. During MF₄, cows fed in fewer meals per day and had longer meals than during MF₈. The control gates were used efficiently, with only a few passages not resulting in actual meals. Although the voluntary meal intervals seemed to be short, the average milking frequency was far below that theoretically possible. This was explained by individual differences in milking frequency and long intervals from when a cow was redirected in a control gate until it arrived in the milking unit. A wide individual range in the voluntary interval between the first and the second meal in the milking cycle suggests that fixed time limits for control gates set on group level have no justifiable biological basis. It was also concluded that primiparous cows were well adapted to the automatic milking system after 2 wk in the barn.     

Effect of frequency of milking on yield,composition and processing quality of milk

The objective was to determine the effect of once-daily milking (ODM) and omitting one evening milking each week (13TWM), in late lactation on milk production, composition and processability. Seventy-two cows were assigned to three treatments (ODM, 13TWM and twice-daily milking [TDM]) from 4 October to 12 December. Cows were on average 218 d into lactation at the start of the trial, and all cows were managed similarly throughout the trial. Milk yields and gross milk composition of cows on all treatments were measured, and milk samples for detailed compositional and processability analysis were collected from TDM and ODM treatments at two consecutive milkings and at one milking each week, respectively. Milk yield was significantly reduced (P < 0.001) and milk fat and protein concentrations were increased (P < 0.01) with ODM compared with TDM. Milk yield and fat and protein concentrations of milk from TDM and 13TWM herds were similar. Casein concentrations in ODM and TDM milks were similar, but ODM milk had a higher (P < 0.05) whey protein content. Somatic cell count of ODM and TDM milks was similar. Rennet coagulation time (RCT) and curd firmness (A60) of milk were not affected by milking frequency. However, rate of curd aggregation (K20) of ODM milk was reduced (P < 0.05) compared with that of TDM milk. Plasmin activity in ODM milk was numerically higher than in TDM milk, but the effect was not significant. ODM milk had higher NAGase activity than TDM milk (P < 0.01). In conclusion, once daily milking reduced milk yield by 29% and did not adversely affect the processability of milk. Moreover, one evening milking per week could be eliminated without adverse effects on milk yield or composition.     

The milk yield response to frequent milking in early lactation of dairy cows is locally regulated

Frequent milking during early lactation of dairy cows increases milk production throughout lactation; however, whether this response is regulated systemically via lactogenic hormones, locally in the mammary gland, or both is unknown. We hypothesized that the effects of frequent milking on milk production during early lactation are regulated via local mechanisms. Ten multiparous cows were assigned at parturition to unilateral frequent milking [UFM; twice daily milking of the left udder half (2×), or 4 times daily milking of the right udder half (4×)] for d 1 to 21 of lactation. After treatment, cows were milked twice daily for the remainder of lactation. At the first milking after calving, milk yield from individual quarters was measured to verify that udder halves produced equal amounts of milk prior to treatment. Thereafter, individual quarters were milked on d 3 and 7, weekly for the first 5 wk of lactation, and once every 3 mo for the remainder of lactation. During UFM, cows produced 3.9 ± 0.7 kg/d more from the side milked 4× than the side milked 2×. Upon cessation of treatment, milk production from the side milked 4× decreased, but remained at 1.8 ± 0.5 kg/d more than the side milked 2× for the remainder of lactation. After milk yield was corrected to the equivalent of a whole-udder basis, acute milk yield responses to frequent milking were found to be consistent with previous reports. Moreover, we observed greater persistency in the milk yield response, which lasted throughout lactation. We conclude that both immediate and persistent effects on milk production of frequent milking during early lactation are regulated at the level of the mammary gland. Our results demonstrate that UFM is a valid and efficient model for investigating the effects of frequent milking during early lactation in dairy cows.     

Increased serum serotonin improves parturient calcium homeostasis in dairy cows

Hypocalcemia in dairy cows is caused by the sudden increase in calcium demand by the mammary gland for milk production at the onset of lactation. Serotonin (5-HT) is a key factor for calcium homeostasis, modulating calcium concentration in blood. Therefore, it is hypothesized that administration of 5-hydroxy-l-tryptophan (5-HTP), a 5-HT precursor, can increase 5-HT concentrations in blood and, in turn, induce an increase in blood calcium concentration. In this study, 20 Holstein dairy cows were randomly assigned to 2 experimental groups. Both groups received a daily i.v. infusion of 1 L of either 0.9% NaCl (C group; n = 10) or 0.9% NaCl containing 1 mg of 5-HTP/kg of BW (5-HTP group, n = 10). Infusions started d 10 before the estimated parturition and ceased the day of parturition, resulting in at least 4 d of infusion (8.37 ± 0.74 d of infusion). Until parturition, blood samples were collected every morning before the infusions, after parturition samples were taken daily until d 7, and a final sample was collected on d 30. Milk yield was recorded during this period. No differences between groups were observed for blood glucose, magnesium, and β-hydroxybutyrate. Cows receiving the 5-HTP infusion showed an increase in fatty acid concentrations from d ?3 to ?1 before parturition. Serum 5-HT concentrations were increased at d ?4 related to parturition until d 5 postpartum in the 5-HTP group compared with the C group. In addition, cows from the 5-HTP group had increased 5-HT concentrations in colostrum, but not in mature milk, on d 7 postpartum. Serum calcium concentrations decreased in both groups around parturition; however, calcium remained higher in the 5-HTP group than in controls, with a significant difference between groups on d 1 (1.62 ± 0.08 vs. 1.93 ± 0.09 mmol/L in control and 5-HTP groups, respectively) and d 2 (1.83 ± 0.06 vs. 2.07 ± 0.07 mmol/L in control and 5-HTP groups, respectively). Additionally, colostrum yield (first milking) was lower in the 5-HTP group compared with the C group, but without consequences on colostrum IgG concentrations. Milk yield did not differ between groups during the rest of the experiment. The study data were consistent with the concept that infusion of 5-HTP to dairy cows increases blood 5-HT concentrations, which in turn is a significant regulatory component in the chain of effectors that affect calcium status around parturition, hence the occurrence of clinical or subclinical hypocalcemia.     

Peripartal progesterone and prolactin have little effect on the rapid transport of immunoglobulin G into colostrum of dairy cows

Colostrum formation and lactogenesis in the mammary gland and the timing of parturition are regulated by endocrine signals. Changes in progesterone (P4) and prolactin (PRL) are considered key events that inhibit colostrum formation, trigger parturition, and signal the onset of lactation. The goal of our study was to determine if colostrum yield and composition and immunoglobulin transfer are affected by prepartum milking relative to the decrease in P4, peak of PRL, or occurrence of parturition. Twenty-three multiparous cows were randomly assigned to 1 of 2 groups: (1) control with first milking at 4 h postcalving (CON, n = 11), and (2) treatment group with first milking approximately 1 d before calving and second milking at 4 h after parturition (APM, n = 12). Colostrum yields were recorded and proportional samples were analyzed for immunoglobulin G (IgG) concentration. Blood plasma samples for the analyses of P4 and PRL were collected 3 times daily at 8-h intervals for 4 d prepartum and again taken at 4 h after parturition. Total colostrum mass of APM cows was higher than that of CON cows. Immunoglobulin G concentration and protein content did not differ between antepartum milking in APM cows and postpartum milking in CON cows. Colostrum IgG concentration and protein content in APM cows at the postpartum milking were lower compared with the IgG concentration established at the prepartum (APM) and postpartum milkings of CON cows. Immunoglobulin G mass did not differ in first and second colostrum collection in APM cows but was lower compared with that of CON cows. The sum of IgG mass in APM cows (prepartum + postpartum collections) did not differ from that of CON cows. Lactose and fat in milk (concentration and mass) increased from first to second milking in APM cows. Total mass of lactose and fat in APM cows (prepartum + postpartum collections) was greater compared with that of CON cows. The finding that the time of milking relative to parturition, P4 decrease, and PRL peak slightly affected yield and quality of colostrum emphasizes the complex interactions of numerous endocrine and morphological changes occurring during colostrogenesis and lactogenesis in dairy cows. The considerably rapid transfer of immunoglobulins into colostrum of prepartum-milked cows within a few hours leads to the hypothesis that the transfer of IgG can be very fast and—contrary to earlier findings—persist at least until parturition.     

Leptin concentrations in relation to energy balance,milk yield,intake, live weight,and estrus in dairy cows

The objective of this study was to describe fluctuations in leptin concentrations during late pregnancy and lactation and to investigate how those fluctuations are related to energy balance, milk yield, milk components, dry matter intake, live weight, first postpartum luteal activity, and first observed estrus during lactation. Live weight, dry matter intake, energy balance, and milk yield were measured weekly on 304 primiparous Holstein cows for the first 80 d of lactation. The first postpartum luteal activity was determined by measuring milk progesterone, and independently, first observed estrus. For measuring leptin concentrations from 30 d before until 80 d after calving, blood samples were taken at 2-wk intervals at a fixed time of the day after milking but before feeding. Leptin concentrations were high during pregnancy and declined to a nadir at parturition. It seems that leptin concentrations reflect the state of energy balance during lactation; plasma leptin concentrations were lower in cows with a mean negative energy balance during lactation. Those cows usually produced more milk, consumed less feed, and had a lower live weight compared with cows having a mean positive energy balance. The recovery of leptin concentrations from the leptin nadir at parturition seemed to depend on the extent and duration of the negative energy balance, thus probably on the amount of fat that was re-accumulated. Although there was lack of a relationship between leptin and first postpartum luteal activity, higher leptin concentrations associated with shorter intervals to first observed estrus might indicate a relationship between leptin and expression of estrus.     

Short communication: Timing of first milking affects serotonin (5-HT) concentrations

Hormonal signals differentially regulate the timing of parturition, as well lactogenesis and, potentially, colostrum formation in the mammary gland. Non-neuronal serotonin (5-HT) is a homeostatic regulator of the mammary gland. In the current study, we manipulated the timing of first milking to investigate its effects on serum 5-HT and calcium concentrations in the maternal and calf circulation, as well as in colostrum. Twenty-three cows were randomly assigned to a control (CON; n = 10) group, milked for the first time at 4 h postcalving, or a treatment (TRT; n = 13) group, milked for the first time approximately 1 d before calving in addition to 4 h postcalving. Maternal blood samples were collected for 4 d precalving, 3 times daily, and 1 blood sample was taken 4 h postcalving. Calf blood samples were collected 4 (before first colostrum feeding) and 12 h after birth, and at 3 wk of age. Calves from both treatments were fed colostrum from their respective mothers. Serum 5-HT concentrations were greater in CON cows and decreased significantly in TRT cows after milking was initiated precalving (951 vs. 524 ± 111 ng/mL, respectively). Cow serum calcium concentrations were affected by time, beginning to decrease 1 d precalving until 4 h postcalving, but this drop in serum calcium was more pronounced in TRT cows. Serum 5-HT and calcium concentrations were negatively correlated (r = −0.57) for the CON cows and positively correlated (r = 0.6) for the TRT cows. Maternal calcium and 5-HT decreased similarly due to precalving milking. Calcium and 5-HT concentrations were greater in colostrum collected from TRT cows milked precalving. Overall, calves had higher circulating 5-HT concentrations than cows, and calves born to TRT cows had increased 5-HT concentrations compared with the CON. Precalving milking could affect 5-HT synthesis within the mammary gland and therefore affect maternal 5-HT and calcium concentrations. Further research is needed in ruminants to assess the extent of 5-HT placental transfer, its role on pre- and postnatal development of the calf, the importance of its presence in colostrum, and potential long-term effects on calf health.     

Camel (Camelus dromedarius) immunoglobulin G, alpha-lactalbumin, serum albumin and lactoferrin in colostrum and milk during the early post partum period

Colostrum and milk samples from twelve Tunisian camels were analysed for concentration of immunoglobulin G (IgG), alpha-lactalbumin (alpha-la), serum albumin (CSA) and lactoferrin throughout the first 14 milkings post partum (7 days of lactation) using single radial immunodiffusion assay. Concentrations (mg/ml, means+/-SD) at first milking were IgG, 100.7+/-60.4; alpha-la, 2.2+/-0.7; CSA, 8.5+/-3.6 and lactoferrin, 1.2+/-0.3. Large variations were recorded for IgG and CSA concentrations (11.8-211.1 mg/ml and 2.9-13.8 mg/ml respectively) Concentrations of IgG and CSA dropped abruptly in the subsequent milkings while alpha-la concentration increased until milking 5 and then decreased slowly. Lactoferrin dropped only from milking 7. Mean IgG concentrations were 3.6 and 2.5 mg/ml at milking 9 and 13 respectively. However, IgG concentration did not differ significantly, at the 1% level, from milkings 11 to 14. The contribution of CSA to the increase in whey proteins in early milks was greater than that described in the bovine and caprine species.     

Effect of cobalt supplementation during late gestation and early lactation on milk and serum measures

Thirty-six multiparous cows were assigned to a study to determine the effects of dietary Co supplementation during late gestation and early lactation on concentrations of Co in serum and liver, vitamin B₁₂ concentrations in serum and milk, and milk yield. Nonlactating cows received diets containing 0.15, 0.89, or 1.71 mg/ kg of Co (dry matter basis) from 55 d before parturition, and lactating cows received diets containing 0.19, 0.57, or 0.93 mg/kg of Co (dry matter basis) from parturition through 120 d postpartum. Serum vitamin B₁₂ concentrations declined sharply in all cows between 55 and 20 d prepartum. Dietary Co supplementation tended to cause an increase in the concentration of vitamin B₁₂ in colostrum and milk. Cobalt intake did not affect concentrations of Co in liver or serum, but increased the Co concentration of milk (0.089, 0.120, and 0.130 μg of Co/mL) at 120 days in milk. There was no effect of Co supplementation on dry matter intake or yield of milk and milk components. In conclusion, serum concentrations of vitamin B₁₂ are reduced in the early dry period, and added dietary Co may increase ruminal synthesis of vitamin B₁₂ as indicated by a tendency for increased vitamin B₁₂ concentrations in colostrum and milk of cows supplemented with dietary Co.     

Secretion and mammary gland uptake of prolactin in dairy cows during lactogenesis

Mammary arteriovenous differences of prolactin concentration and net mammary uptake of prolactin from blood were quantified near parturition in 9 dairy cows. Six cows were milked once daily for at least 6 d before parturition, and prepartum lactogenesis occurred in 3 of 6 cows. Prepartum milking 2 or more d before parturition abruptly increased secretion of prolactin into blood, but milkings within 1 d before or after parturition did not increase prolactin secretion. Concentrations of prolactin in whole milk sampled over 8 d before parturition (64.5 ng/ml) were substantially greater than those occurring several days after parturition (19 ng/ml). Milk prolactin concentrations were unaffected by the successful induction of prepartum lactogenesis, which greatly increased prepartum yields of milk (2 to 8 kg/milking). Therefore, the alveolar lumenal content of prolactin was greatest in pregnant cows with prepartum lactogenesis. This enhanced content of intraalveolar prolactin before parturition was associated with an absence of mammary uptake of prolactin immediately prior to ejection of the prolactin-containing milk from the alveoli. However, prolactin uptake was quickly restored to about 2 micrograms/min per half udder shortly after milk ejection. During the prepartum period, an enhanced intraalveolar reservoir of 200 to 400 micrograms prolactin, due to induction of prepartum lactogenesis, appears to saturate temporarily all putative sites for uptake of prolactin from blood.     

Effect of dry-off management on milking behavior,milk yield,and somatic cell count of dairy cows milked in automated milking systems

Milk production may be reduced before dry-off to decrease the risk of cows developing intramammary infections during the dry period. Such reductions in milk may be possible in automated milking systems (AMS) where milking frequency and feed allocation at the AMS can be controlled at the cow level. This study investigated the effect of dry-off management of cows milked in AMS on milk yield, milking behavior, and somatic cell count (SCC). Using a 2 × 2 factorial arrangement of treatments, applied from d 14 to 1 before dry-off, 445 cows from 5 commercial dairy farms in Quebec, Canada, were assigned within farm to either (1) reduced feed [RF; allowed a maximum of 0.75 kg/d of AMS pellet for the first week (14 to 8 d before dry-off) of treatment, and 0.50 kg/d for the second week (7 to 1 d before dry-off) of treatment], or (2) nonreduced feed (NF; allowed up to 2 kg/d of AMS pellet), and either (1) reduced milking (RM; reduced to 2 milkings/d or as many times as required to yield 17 kg/milking), or (2) nonreduced milking (NM; allowed up to 6 AMS milkings/d) and no maximum production. Feed and milking behavior data, as well as milk yield and SCC were collected from the AMS software. The RF cows had lower AMS feed delivered during the treatment period, as per the experimental design. Across the treatment period, the NF-NM cows had the highest milking frequency (2.7 times/d), followed by the RF-NM cows (2.4 times/d), and then both of the RM groups (1.8 times/d), which did not differ from each other. All cows, except the NF-NM cows, were gradually milked less frequently as dry-off approached. Across the entire 2-wk treatment period before dry-off, cows with RM allowance experienced a higher reduction in milk yield compared with the cows with no milking allowance restrictions (?4.8 vs. ?3.6 kg). Similarly, cows with a RF allocation tended to have a higher reduction in milk yield than cows with NF (?4.6 vs. ?3.7 kg). As result, those cows with both reduced milking permissions and feed allocation at the AMS experienced the greatest drop in milk production before dry-off. There were no differences between treatments for milking frequency or yield in the next lactation. Somatic cell score (calculated from SCC) was not different between treatments in the 2-wk or day before dry-off, nor in the first month after calving. Overall, these data suggest that reducing both milking frequency and feed quantity in the AMS is the most efficient method to decrease milk yield before dry-off, without negatively influencing milking frequency or yield in the next lactation, as well as without affecting milk quality.     

Three times a day milking during the first half of lactation

Three milking frequency treatments were compared: twice daily milking; thrice daily milking until milk dropped below 24 kg; thrice daily milking until milk dropped below 31 kg. Three time milking was at least 45 days but no more than 150 days. Cows (12 to 14 per group) were managed alike except for milking frequency. In early lactation, increased milking had little effect. With time the superiority in yields increased such that cows on three times for 150 days were outproducing two time cows by 20%. Cumulative milk yields were greater for the thrice groups than for the twice group by 5% at 56 days, 11 and 8% at 154 days, 11 and 9% at 182 days, and 10% at 280 days. Fat percentage, adjusted for previous lactation fat percentage, averaged .2 to .3% lower for the cows milked three times until 24 kig but only .1% lower for cows milked thrice until 31 kg. Increased yield was primarily from prolonged peak yield and less subsequent decline. Switching from three to two milkings decreased yield 6 to 8% in the 1st wk. However, three time milking had a positive carryover, apparently due to higher starting yield at the point at which they were switched.     

Effects of an automatic milking system on milk yield and quality of Mediterranean buffaloes

A study was carried out to evaluate the effects of an automatic milking system (AMS) on milk yield and composition of buffalo (Mediterranean-type Bubalus bubalis) cows. Performed from January 2015 to December 2015 in an organic buffalo dairy farm equipped with both a traditional tandem milking parlor and an AMS, the study involved 90 primiparous buffaloes randomly allotted to a tandem or AMS group from 5 to 10 d of lactation onward. Number of milkings per day and daily milk yield of each cow were recorded, and individual milk sampling was carried out twice a month. Compared with the tandem, the AMS group showed significantly higher daily milk yield and persistence of lactation. Use of the AMS resulted in higher protein and casein contents, and lower somatic cell and total bacterial counts, whereas fat, freezing point, and pH were unaffected by the system. We conclude that, in terms of milk yield and quality, automatic milking may be a suitable alternative to conventional milking for buffaloes.