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

Effects of feeding level, milking frequency, and single injection of cabergoline on blood metabolites, hormones, and minerals around dry-off in dairy cows

This study aimed to investigate the effect of the different dry-off strategies based on reducing feeding level (normal vs. reduced energy density), reducing milking frequency (twice vs. once daily), and administration of a dopamine agonist after last milking (i.e. saline vs. cabergoline injection) on blood metabolites, hormones, and minerals around dry-off. In this experiment, 119 Holstein dairy cows were used in a 2 × 2 × 2 factorial arrangement. In the last week before dry-off, cows were allocated to 1 of the 4 possible dry-off strategies based on feeding level and milking frequency. Within 3 h after last milking, cows were injected with either saline or a D₂ dopamine agonist (cabergoline; Velactis, Ceva Santé Animale, Libourne, France; labeled for use only with abrupt dry-off, e.g., no preceding reduction in feeding level or milking frequency before last milking). After dry-off, all cows were fed the same dry cow diet and data collection continued for a week. Blood samples were collected from the coccygeal vein on d -9, -6, -5, -2, 1, 2, 5, and 7 relative to dry-off. Additionally, blood was sampled at 0, 3, and 6 h relative to injection of either cabergoline or saline, equivalent to d 0.125, 0.250, and 0.375 relative to last milking (dry-off). The reduced feeding level before dry-off caused reduced glucose and insulin concentrations as well as increased free fatty acid concentrations, particularly when reduced feeding level was combined with milking the cows 2× daily. The intramuscular injection of cabergoline caused the expected reduction in circulating prolactin concentrations. In addition, dopamine-agonist cabergoline induced an atypical simultaneous pattern of plasma metabolites (i.e., increased glucose and free fatty acid concentrations), hormones (i.e., reduced insulin and increased cortisol concentrations), and minerals (i.e., reduced calcium concentration), indicating that normal metabolic and mineral homeostatic regulations were hindered after the injection of ergot alkaloid cabergoline. In conclusion, reducing milking frequency seems the best management strategy to reduce milk production at dry-off among those tested in this study.

Reproductive Hormones Mediate Intestinal Microbiota Shifts during Estrus Synchronization in Grazing Simmental Cows

To study shifts in the intestinal microbiota during estrus synchronization in ruminants, we characterized the intestinal microbiota in grazing Simmental cows and the possible mechanism that mediates this shift. Fourteen postpartum Simmental beef cows were synchronized beginning on day 0 (D0) with a controlled internal release device (CIDR), and cloprostenol was injected on D9 when the CIDR was withdrawn. Synchronization ended with timed artificial insemination on D12. Serum and rectal samples harvested on D0, D9, and D12 were analyzed to assess the reproductive hormones and microbiota. Reproductive hormones in the serum of the host were measured using enzyme-linked immunosorbent assay. The microbiota was characterized using 16S rRNA sequencing of the V3−V4 hypervariable region, alpha diversity and beta diversity analyses (principal coordinate analysis, PCoA), cladogram of the linear discriminant analysis effect size (LEfSe) analysis, and microbiota function analysis. Levels of the reproductive hormones, except gonadotropin-releasing hormone (p > 0.05), shifted among D0, D9, and D12 (p < 0.05). Decreased community diversity (Chao1 and ACE) was observed on D12 compared with D0 (p < 0.05). The beta diversity (PCoA) of the microbiota shifted markedly among D0, D9, and D12 (p < 0.05). The LEfSe analysis revealed shifts in the intestinal microbiota communities among D0, D9, and D12 (p < 0.05 and LDA cutoff >3.0). The KEGG pathway analysis showed that carbohydrate metabolism, genetic information and processing, the excretory system, cellular processes and signaling, immune system diseases, and the metabolism were altered (p < 0.05). Reproductive hormones (especially estradiol) were correlated with the alpha diversity indices, beta diversity indices, and an abundance of biomarkers of the shifting intestinal microbiota (p < 0.05). In conclusion, the structure, composition, and function of the intestinal microbiota were shifted during estrus synchronization in a grazing Simmental cow model, and these shifts were mediated by reproductive hormones.

Effects of stocking density on oxidative stress status and mammary gland permeability in early lactating dairy cows

The current study was conducted to investigate the effect of stocking density (SD) on oxidative stress status and mammary gland permeability in early lactating dairy cows. Thirty-two dairy cows were allocated into 16 blocks, basing on parity, previous milk yield, and body weight, and were then randomly assigned into one of the two treatments as follows: 75% (75SD) and 100% (100SD) SD. The cows were fed with same diet throughout the 8-week experimental period. The milk yield and milk sample were collected on two consecutive days during the 8-week experimental period weekly. Plasma samples were collected on fourth and eighth experimental weeks. Raw, energy-corrected, and 4% fat-corrected milk yield were significantly higher in 75SD-cows than that of 100SD-animals, respectively. The milk somatic cell count was lower in 75SD-cows than that of 100SD-animals. The levels of Na⁺ , Na⁺ /K⁺ , bovine serum albumin and plasmin were lower in 75SD-cows than those of 100SD-cattle, respectively. The 75SD-cows had reduced insulin and insulin/glucagon levels but higher prolactin and growth hormone concentrations, compared with those of 100SD-animals, respectively. In conclusion, compared with low SD-animals, early lactating cows with higher SD had higher oxidative stress status, which further led to a greater mammary gland permeability.

Innovative dairy cow management to improve resistance to metabolic and infectious diseases during the transition period

The incidence of metabolic and infectious diseases varies greatly during the lactation cycle. Most new cases of clinical mastitis appear at the beginning of lactation, and the incidence increases with the level of milk production. In addition to mastitis, many other infectious diseases become clinically apparent during the first 2weeks of lactation. During this time, cows are in a negative energy balance and must mobilize body reserves to balance the deficit between food energy intake and energy required for milk production. The relationships between energy deficit and metabolic diseases, such as ketosis and hepatic lipidosis, are well known. Furthermore, cows in energy deficit have a weakened immune system and are therefore more susceptible to infections. There is now good evidence that the increase in circulating non-esterified fatty acids impairs immune cell functions. Therefore, management approaches that reduce the negative energy balance and the increase in non-esterified fatty acids at the beginning of lactation are likely to improve resistance to infection. Improving the nutrient supply through periparturient nutritional management has been the subject of considerable research. However, another way to reduce the imbalance between nutrient supply and demand is to temporarily decrease the latter. In this review, we examine how management strategies such as conjugated linoleic acid feeding, prepartum milking, or limiting postpartum milk production could be used to reduce metabolic perturbations and immunosuppression during the transition period. At this stage, it appears that reducing the amount of milk harvested postpartum by means of partial milking in the first days after calving is the most promising approach to reduce metabolic stress and immunosuppression without compromising the productivity of high-yielding dairy cows.

Relationship between glucocorticoids and prolactin during mammary gland stimulation in dairy cows

The objectives of this study were to determine the role of glucocorticoids in the regulation of prolactin (PRL) release induced by mammary gland stimulation and to investigate whether the milk depression induced by glucocorticoids in dairy cows is due to a decrease in PRL release. In experiment 1, 8 dairy cows were used in a 4 × 4 Latin square design. Four hours after the morning milking, the cows received 1 of the following treatments: (1) a 5-min manual stimulation of the mammary gland; (2) an i.v. injection of 1 mg of dexamethasone; (3) 2 infusions of 2.5 g of metyrapone (an inhibitor of cortisol biosynthesis) in the omasum 4 and 2 h before a 5-min stimulation of the mammary gland; or (4) no treatment. Sixty minutes later, the mammary gland of each cow was stimulated for 5 min. Blood samples were collected from 20 min before to 120 min after the start of the treatment. When the mammary gland was stimulated twice in 60 min, less PRL and cortisol were released during the second stimulation. Metyrapone did not affect PRL or cortisol release. Dexamethasone decreased serum cortisol concentration but did not affect PRL concentration. In experiment 2, 16 cows were used in a crossover experimental design consisting of 2 experimental weeks separated by 1 resting week. During the first week, cows were treated as follows: (1) 4 cows were injected with 0.5 g of domperidone (a PRL secretagogue) in canola oil on d 1 and 2 and 20 mg of dexamethasone on d 1; (2) 4 cows were injected with 0.5 g of domperidone on d 1 and 2; (3) 4 cows were injected with canola oil on d 1 and 2 and with 20 mg of dexamethasone on d 1; and (4) 4 cows were injected with canola oil on d 1 and 2. During the second experimental week, the same 4 treatments were repeated, except the cows that did not receive dexamethasone in the first week received it on d 1 of the second week, and cows that did receive it in the first week did not receive it in the second week. On d 1 and 2 of each week, blood samples were collected during morning milking for PRL determination. Dexamethasone reduced milk production and decreased both basal and milking-induced PRL release. It also increased milk fat and protein percentages and decreased milk lactose content. Domperidone increased basal PRL levels in serum and milk but did not affect milk yield. Although we cannot rule out the possibility that inhibition of PRL secretion or reduction of mammary gland PRL responsiveness play a role in the inhibition of milk production by glucocorticoids, the fact that enhancement of PRL secretion by domperidone could not prevent the depression of milk yield suggests that other mechanisms are involved.

Endogenous opiates and behavior: 2014

This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants). This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants).

Release of β-endorphin, adrenocorticotropic hormone and cortisol in response to machine milking of dairy cows

Aim:

The present study was undertaken with the objective to obtain insight into the dynamics of the release of β-endorphin, adrenocorticotrophic hormone (ACTH) and cortisol in response to machine milking in dairy cows.

Materials and Methods:

A total of 10 healthy multiparous lactating Italian Friesian dairy cows were used in the study. Animals were at the 4^th-5^th month of pregnancy and were submitted to machine milking 2 times daily. Blood samples were collected in the morning: In baseline conditions, immediately before milking and after milking; and in the early afternoon: In baseline conditions, before milking and after milking, for 2 consecutive days. Endocrine variables were measured in duplicate, using a commercial radioimmunoassay for circulating β-endorphin and ACTH concentrations and a competitive enzyme-linked immunoassay for cortisol concentration.

Results:

Data obtained showed a similar biphasic cortisol secretion of lactating dairy cows, with a significant increase of cortisol concentration after morning machine milking, at both the 1^st and the 2^nd day (p<0.05), and a decrease after afternoon machine milking at the 2^nd day (p<0.01). One-way RM ANOVA showed significant effects of the machine milking on the cortisol changes, at both morning (f=22.96; p<0.001) and afternoon (f=15.10; p<0.01) milking, respectively. Two-way RM ANOVA showed a significant interaction between cortisol changes at the 1^st and the 2^nd day (f=7.94; p<0.0002), and between the sampling times (f=6.09; p<0.001). Conversely, no significant effects of the machine milking were observed on β-endorphin and ACTH changes, but only a moderate positive correlation (r=0.94; p<0.06) after milking stimuli.

Conclusions:

A wide range of cortisol concentrations reported in this study showed the complex dynamic patterns of the homeostatic mechanisms involved during machine milking in dairy cows, suggesting that β-endorphin and ACTH were not the main factors that caused the adrenocortical response to milking stimuli.

The effects of parity, litter size, physiological state, and milking frequency on the metabolic profile of Lacaune dairy ewes

Effects of parity (primiparous, PRIM vs multiparous, MULT) and litter size (singletons, SING vs twins, TWIN) on metabolic profiles from 1 wk before lambing to the end of lactation were studied in 48 Lacaune dairy ewes reared in confinement during most of the year and grazed on improved pastures at the end of lactation (summer). Another group of 48 ewes was incorporated during the milking period (ie, from 1 wk after weaning), to measure the effects of milking frequency (1 vs 2 milkings per day) on intake, milk production and composition, and body energy usage. Thus, in a 2 × 2 × 2 factorial design, ewes (n = 96) were allocated to homogeneous groups according to body weight (BW) and body condition score (BCS) and were monitored from late pregnancy to late lactation as a function of parity (PRIM, n = 48; MULT, n = 48), litter size (LSi) (SING, n = 40; TWIN, n = 56) and daily milking frequency (FREQ; milked once, ONE; n = 48; or twice, TWO; n = 48). Individual BW, BCS, plasma metabolites, and metabolic hormones were measured regularly (ie, 9 consecutive sampling dates). The BW was higher in MULT but no differences because of LSi or FREQ were detected at the intra-parity group level. The BCS was higher in MULT and in ewes with SING throughout the experiment. The latter was related to the demands for body reserves mobilization, as expressed by higher nonesterified fatty acids and β-hydroxybutyrate concentrations in ewes with TWIN from late pregnancy to weaning (35 d postpartum) in both PRIM and MULT ewes. This was consistent with higher insulin in MULT and higher triiodothyronine, leptin and insulin-like growth factor 1 in ewes with SING during this period. Differences in energy balance because of FREQ were evident after interpretation of plasma nonesterified fatty acids, glucose, insulin, and leptin concentration during the milking period. At similar feed intakes, ewes in ONE were in positive balance with regard to TWO. Overall, clear effects of parity, LSi, physiological states, and FREQ on metabolic profiles were found because of differences in nutrient partitioning when combining these experimental factors. Without considering FREQ, changes in metabolic measures in milking period were marginal compared with the periparturient adjustments performed until weaning to compensate energy deficiencies.