Pierre Lacasse

Agriculture and Agri-Food Canada | AAFC · Sherbrooke Research and Development Centre (DSRDC)

In dairy cows, it is believed that the decrease in milk production after the peak of lactation is largely caused by mammary epithelial cell loss. However, the physiological regulations of lactation persistency in dairy ruminants are not entirely elucidated. Therefore, several experiments were conducted to assess the effects of hormonal and nutritio...

During the transition period, dairy cows often experience negative energy balance, which can induce metabolic and immunological disturbances. Previous work has shown that there is a relationship between the dysfunction of immune cells and the increase in blood nonesterified fatty acid (NEFA) concentration. Nevertheless, it is difficult to determine...

Mammary gland secretory activity is modulated by systemic and local factors; however, the relationship between these factors is unknown. The aim of this study was to determine how a local factor, such as incomplete milking, affects mammary epithelial cell activity, number, and responsiveness to blood prolactin (PRL). Eight cows in mid-lactation wer...

The use of teat dips is one of the most effective strategies to control mastitis by preventing new intramammary infections. Reducing bacterial load on teat skin helps control the spread of pathogens and spoilage and improves the quality of milk. The objective of this study was to evaluate the reduction of bacterial populations through the applicati...

During the transition period, dairy cows often experience negative energy balance, which induces metabolic and immunological disturbances. Our previous work has shown a relationship between the inhibition of immune functions and increased blood nonesterified fatty acid (NEFA) levels. In this study, we evaluated the effect of 11 fatty acids (palmito...

Antibiotics are the most effective strategy to prevent and treat intramammary infections. However, their misuse has led to the dissemination of multidrug resistant bacteria (MDR) for both animals and humans. Efforts to develop new alternative strategies to control bacterial infections related to MDR are continuously on the rise. The objective of th...

Bovine mastitis, commonly caused by bacteria, is one of the most devastating diseases for the dairy industry worldwide, with high economic, social, and public health impacts. Among the pathogenic bacteria, Staphylococcus aureus is one of the leading pathogens in most countries. Success rate of antibiotic treatment is low such that effective control...

Staphylococcus aureus is a leading cause of bovine intramammary infections (IMI). Standard antibiotic treatments are not very effective and currently available vaccines lack tangible efficacy. Developing a vaccine formulation for S. aureus mastitis is challenging and selection of target antigens is critical. The gene products of six S. aureus genes...

Holstein heifers (n = 45) were subjected to treatments according to a 2 × 2 factorial design where the main effects were the photoperiod treatments during the second isometric (ISO, 52–61 wk of age) and the second allometric (ALLO, 62 wk of age to 8 wk before calving) periods of mammary gland development. During the ISO period, heifers were subject...

Reducing costs for rearing replacement heifers by decreasing age at breeding and first calving is pivotal for the efficiency of dairy productions. Thus, knowledge on mammary gland growth, development and involution are fundamental to promote improved production performance. Mammary gland development and lactation occur in cycles during a cow's life...

Eleven mid-lactation Holstein cows were milked twice daily during the first 2 experimental weeks. During wk 3 to 10, the cows were differentially milked: right quarters were milked thrice daily (3×) and left quarters were milked once daily (1×). During wk 11 to 14, all quarters were milked twice daily. After 4 wk of differential milking, the cows r...

Use of antimicrobial approaches at drying-off for preventing new intramammary infections (IMI) during the dry period in dairy cows could be replaced by non-antimicrobial approaches. Such approaches would be of interest not only for organic but also for conventional dairy producers. The objective of the current review was to quantify the effect of n...

Little is known about the effects of heat stress during the late gestation period on lactation in dairy goats. For this reason, 32 Saanen goats were randomly assigned to 1 of 2 groups, control (CT; n = 16) or heat stress (HS; n = 16), during late gestation. The HS goats were housed in a climatic chamber before parturition and subjected to heat stre...

Cows undergoing a negative energy balance ( NEB ) often experience a state of immunosuppression and are at greater risk of infectious diseases. The present study aimed to evaluate the impact of a folic acid and vitamin B 12 supplement and feed restriction on several immune parameters. Sixteen cows at 45 ± 3 days in milk were assigned to 8 blocks of...

Lactation persistency (LP), defined as the ability of a cow to maintain milk production at a high level after milk peak, is an important phenotype for the dairy industry. In this study, we used a targeted genotyping approach to scan for potentially functional single nucleotide polymorphisms (SNPs) within 57 potential candidate genes derived from ou...

The mammary tissue is characterized by its capacity to adapt in response to a wide variety of changing conditions. This adaptation capacity is referred to as the plasticity of mammary tissue. In dairy ruminants, lactation is challenged by modifications that can either be induced on purpose, such as by modifying management practices, or occur involu...

Accumulating evidence supports that the hormone prolactin (PRL) is galactopoietic in dairy ruminants. Accordingly, the inhibition of PRL secretion by the dopamine agonists quinagolide and cabergoline causes a sharp decline in milk production and could be useful in several critical periods. First, PRL inhibition may reduce the incidence during the p...

Bovine mammary gland involution, as a part of the reproductive cycle in dairy cows, is a very important remodeling transformation of the mammary gland for the subsequent lactation. There is considerable incentive to accelerate mammary gland involution to improve udder health, shorten the dry period, and simplify the management process by reducing d...

The present work described physicomechanical properties of three blends of commercial chitosans (A, B, or C) with polyvinyl alcohol (PVA). Chitosans at concentration of 20 g/L and 30 g/L were hydrated in acidic solution and basified with either β-glycerophosphate (β-Gph) or sodium bicarbonate (NaHCO3) up to the pH 6.8. Shear and frequency developme...

The present experiment was conducted to determine whether, during periods of negative energy balance, the increase in glucose availability, despite similar DMI and greater milk production, induced by a combined supplement of folic acid and vitamin B 12 was related to effects of insulin on metabolism. Sixteen multiparous Holstein cows averaging 45 d...

Accumulating evidence supports that the hormone prolactin (PRL) is galactopoietic in dairy ruminants. Accordingly, the inhibition of PRL secretion by the dopamine agonists quinagolide and cabergoline causes a sharp decline in milk production and could be useful in several critical periods. First, PRL inhibition may reduce the incidence during the p...

The mammary tissue is characterized by its capacity to adapt in response to a wide variety of changing conditions. This adaptation capacity is referred to as the plasticity of mammary tissue. In dairy ruminants, lactation is challenged by modifications that can either be induced on purpose, such as by modifying management practices, or occur involu...

Three experiments were conducted to better understand why milking-induced prolactin (PRL) release decreases as lactation advances. Experiment 1 compared the effects of milking, 2-min manual stimulation of the mammary gland (without milking), or injection of 1 IU of oxytocin (without milking) on hormonal release in early lactation cows, late-lactati...

The main objective of the current study was to measure the effect of incomplete milking on luteal activity and on pregnancy hazard. We also aimed to study the effect of early-lactation hyperketonemia (i.e., β-hydroxybutyrate blood concentration ≥1.4 mmol/L during the first 3 wk in milk) on those reproductive outcomes. Multiparous Holstein cows (n =...

The aim of this study was to investigate the effect of an incomplete milking on risk of mastitis and reproductive tract disease. Multiparous dairy cows (n = 878) from 13 commercial herds were enrolled in a randomized controlled trial. Cows were randomly assigned to either a control (milked conventionally) or a treatment group, which consisted of an...

Limiting milk production for a short period of time in early lactation could be a relevant strategy to prevent hyperketonemia (HYK). From December 2013 to March 2015, 838 multiparous Holstein cows from 13 herds were enrolled in a randomized controlled trial evaluating the effect of incomplete milking in early lactation on ketonemia and its effect o...

An incomplete milking in early lactation could help limit negative energy balance in dairy cattle, but its potential effects on culling hazard and on milk production and composition throughout the entire lactation are unknown. The objective of this study was to evaluate the effect of an incomplete milking during the first 5 d in milk on culling haz...

The objective of this study was to determine whether the responsiveness of the mammary gland to prolactin (PRL) is affected by the concentration of the hormone. After 1 pre-experimental week (d -7 to -1), 18 Holstein cows in mid to late lactation were injected intramuscularly twice daily with either 0.5 mg of quinagolide (QN) or 2 mL of water (cont...

Estradiol inhibits milk production in dairy cows. The present study evaluated the effect of 17β-estradiol (E2) injections on prolactin (PRL) secretion and the mammary gland response to this hormone. Eight mid-lactation cows were used in a crossover design. During each experimental period, the cows were injected daily with either E2 (2.5 mg) or soy...

Clinical mastitis is an important disease in dairies. Its treatment is mainly based on the use of antimicrobial drugs. Numerous non-antimicrobial drugs and treatment strategies have already been reported for clinical mastitis treatment, but data on their efficacy have never been collated in a systematic way. The objective of this systematic review...

The risk for a dairy cow to acquire new intramammary infections is high during the transition from lactation to the dry period, because of udder engorgement and altered immune functions. Once the gland is fully involuted, it becomes much more resistant to intramammary infections. Therefore, strategies to depress milk yield before drying-off and acc...

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 2 weeks of lactatio...

Staphylococcus aureus is one of the major pathogens causing bovine intramammary infections (IMIs) and mastitis. Mastitis is the primary cause for the use of antibiotics in dairy farms but therapeutic failure is often observed. One of the reasons for the lack of effectiveness of antibiotic therapy despite the observed susceptibility of bacterial iso...

During the periparturient period, the abrupt increase in energy demand for milk production often induces metabolic and immunological disturbances in dairy cows. Our previous work has shown that reducing milk output by milking once a day or incompletely in the first few days of lactation reduces these disturbances. The aim of this study was to reduc...

This study shows that how commercial chitosans owing three different molecular weights and high degree of acetylation can be neutralized closed to physiological pH using β-glycerophosphate to produce liquid solution at room temperature and formation of hydrogel upon subsequence heating up to the biological temperature (37 °C). The addition of β-gly...

The transition from lactation to the dry period in dairy cows is a period of high risk for acquiring new intramammary infections. This risk is reduced when the involution of the mammary gland is completed. Accordingly, approaches that speed up the involution process after drying-off could reduce the incidence of mastitis. The current study aimed to...

Lactation persistency (LP), defined as the rate of declining milk yield after milk peak, is an economically important trait for dairy cattle. Improving LP is considered a good alternative method for increasing overall milk production because it does not cause the negative energy balance and other health issues that cows experience during peak milk...

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 desi...

Intramammary infection (IMI) treatment and prevention at drying-off is one of the leading causes for using antimicrobials on dairy farms. The objective of the current paper is to describe the protocol used for conducting a systematic review of the literature on non-antibiotic strategies that can be used on dairy cows at dry off to treat and prevent...

When cows are unable to consume enough feed to support milk production, they often fall into severe negative energy balance. This leads to a weakened immune system and increases their susceptibility to infectious diseases. Reducing the milk production of cows subjected to acute nutritional stress decreases their energy deficit. The aim of this stud...

It has been previously shown that the long-term inhibition of milking-induced prolactin (PRL) release by quinagolide (QN), a dopamine agonist, reduces milk yield in dairy cows. To further demonstrate that PRL is galactopoietic in cows, we performed a short-term experiment that used PRL injections to restore the release of PRL at milking in QN-treat...

Mammary epithelial cells (MEC), that produce milk, are shed into milk during the lactation process. We propose the estimation of MEC exfoliation rate into milk as an original trait to characterize the lactation persistency of dairy cows. We developed a non-invasive method to determine this rate through milk MEC purification by an immuno-magnetic me...

In previous studies, our team showed that the inhibition of prolactin (PRL) secretion by the dopamine agonist quinagolide reduces milk production in dairy cows. The objective of this study was to determine the effects of administration of a dopamine antagonist on basal and milking-induced PRL concentrations in blood and on milk production during po...

In most mammals, prolactin (PRL) is essential for maintaining lactationand its suppression inhibits lactation. However, the involvement of PRLin the control of ruminant lactation is less clear because inconsistenteffects on milk yield have been observed with short-term suppression ofPRL by bromocriptine. Therefore, several experiments were conducte...

The transition from the lactation to the dry period in dairy cows is a period of high risk for acquiring new intramammary infections. This risk is reduced when involution of mammary glands is completed. Consequently, strategies that accelerate the involution process after drying-off could reduce the incidence of mastitis. The objective of this stud...

A cow's risk of acquiring a new intramammary infection during the dry period increases with milk production at drying-off. A method commonly used to reduce milk production is a drastic reduction in feed supply in the days that precede drying-off. Milk production can also be reduced by inhibiting the lactogenic signal driven by prolactin (PRL). This...

Staphylococcus aureus is a significant pathogen frequently causing persistent intramammary infections (IMI) in dairy cows. We compared some genotypic and phenotypic characteristics of 285 strains collected from quarter milk samples from cows with persistent and nonpersistent subclinical IMI across Canada. Variable number of tandem repeats typing wa...

Abstract Text: In previous studies, we have shown that inhibition of prolactin (PRL) secretion by the dopamine agonist quinagolide reduces milk production of dairy cows (Domest Anim Endocrinol 43:154). The objective of this study was to determine the effects of the administration of a dopamine antagonist and feed restriction on basal and milking-in...

A cow's risk of acquiring a new intramammary infection during the dry period increases with milk production at drying off and decreases as mammary gland involution progresses. A method commonly used to reduce milk production is a drastic reduction in feed supply in the days that precede drying off. Milk production can also be reduced by inhibiting...

Holstein multiparous cows (n = 29) and primiparous heifers (n = 32) calving over a 1-yr period were subjected to photoperiod-melatonin treatments according to a 2 × 3 factorial design. Starting 8 wk before expected calving, all animals were subjected to 1 of the following treatments: 8 h of light and 16 h of dark (8L:16D), 16 h of light and 8 h of...

In the present study, the effect of flax hulls with or without flax oil bypassing the rumen on the expression of lipogenic genes in the mammary tissue of dairy cows was investigated. A total of eight dairy cows were used in a replicated 4 × 4 Latin square design. There were four periods of 21 d each and four treatments: control diet with no flax hu...

The effects of flax meal (FM) on the activity of antioxidant enzymes (superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT)) in the blood, mammary tissue and ruminal fluid, and oxidative stress indicators (thiobarbituric acid-reactive substances (TBARS) and 1,1-diphenyl-2-picrylhydrazyl-scavenging activity) in the milk, plasma...

Staphylococcus aureus is a leading cause of intramammary infections (IMI). We recently demonstrated that Staph. aureus strains express the gene guaA during bovine IMI. This gene codes for a guanosine monophosphate synthetase and its expression is regulated by a guanine riboswitch. The guanine analog 2,5,6-triaminopyrimidine-4-one (PC1) is a ligand...

The end of each lactation is a challenging period for high-yielding cows as they are often dried off while still producing significant quantities of milk and, consequently, are highly susceptible to new intramammary infections. Once involution is complete, the mammary gland becomes much more resistant to infection. Therefore, it is critically impor...

Staphylococcus aureus is a leading cause of intramammary infections (IMI) and bovine mastitis is an important disease for the dairy industry. As this bacterium probably expresses specific genes for establishment of IMI, we studied the transcriptional profile of four S. aureus strains recovered from experimentally infected cows. Microbial RNA was ex...

During the transition from pregnancy to lactation, the sudden increase in nutrient demand for milk production causes metabolic perturbations and is associated with immunosuppression and a high incidence of metabolic and infectious diseases in high-yielding cows. In this study, we examined whether limiting milk harvest postpartum while maintaining m...

Once daily milking (ODM) is a management practice that can improve working conditions and reduce production costs in dairy farming compared with twice daily milking (TDM). However, ODM is associated with a decrease in milk yield. Previous research indicated that disruption of tight junctions in the mammary gland may be one of the regulatory factors...

The periparturient period is marked by metabolic, hormonal, and immunological changes, which have an effect on the incidence of infectious and metabolic diseases. In a previous study, a slower increase in milk production was induced by milking cows once daily during the first week of lactation, leading to an improvement in levels of several metabol...

To assess the regulation of mammary cell activity, survival, and proliferation by prolactin (PRL), 5 Holstein cows in early lactation received daily i.m. injections of 1mg of quinagolide, a suppressor of PRL release, for 9 wk, whereas 4 control cows received the vehicle (water) only. During the last week of treatment, one udder half was milked once...

Two studies were conducted to determine the effects of dietary iodine and teat-dipping practices on iodine concentrations in milk. In the first study, 63 cows in mid lactation were assigned to a 3×3 factorial design in which the main effects were dietary iodine levels (0.3, 0.6, and 0.9 mg of dietary I/kg of dry matter) and 3 different postdip mana...

In most mammals, prolactin (PRL) is essential for maintaining lactation and its suppression strongly inhibits lactation. However, the involvement of PRL in the control of ruminant lactation is less clear because inconsistent effects on milk yield have been observed with short-term suppression of PRL by bromocriptine. By contrast, in vitro studies h...