Invited review: Nutritional and management factors that influence colostrum production and composition in dairy cows

Colostrum is a rich source of nutritional and non-nutritional components and is recognized as essential to transfer passive immunity to newborn calves. Because of the individual and seasonal variability in colostrum yield and composition, maintaining an adequate supply of high-quality colostrum year-round remains a challenge for commercial dairy producers. In this narrative review, we described the individual, seasonal, and herd-level variability of colostrum production and summarized the association between individual animal factors such as parity, sex of the calf, calf birth weight, as well as indicators of the cow's metabolic status and the yield and composition of colostrum. Further, we reviewed the current knowledge on the influence of prepartum nutrition and management strategies on colostrum production. Research on the metabolizable energy and protein supplied in the prepartum diet as well as on the inclusion and source of vitamins, minerals, and feed additives suggests prepartum nutrition influences the yield, quality, and composition of colostrum. Furthermore, the prepartum environment and dry period length remain influential factors in the production of colostrum. However, additional research is needed to understand the mechanisms by which prepartum nutrition and management affect colostrum production. Finally, time from calving to colostrum harvest and oxytocin administration as well as the current knowledge on the effect of heat treatment and colostrum storage strategies on colostral components were discussed. To conclude, we identify critical gaps in knowledge for future focus of investigation in colostrum research.

A meta-analysis of the effects of colostrum heat treatment on colostral viscosity, immunoglobulin G concentration, and the transfer of passive immunity in newborn dairy calves

Newborn ruminants depend on colostrum intake immediately after birth to obtain immunoglobulins for effective transfer of passive immunity (TPI). As colostrum may also be a vehicle of infectious agents, heat treatment of raw colostrum is a practice aimed at eliminating or reducing its pathogen load. Despite the usefulness of heat treatment in preventing the transmission of infectious colostrum-borne diseases, heat treatment of colostrum may have some side effects. A systematic review and meta-analysis were conducted to summarize the effects of colostrum heat treatment on colostral viscosity and IgG concentration, and serum IgG concentration as a proxy for TPI in newborn calves fed raw versus heat-treated colostrum. Moderators were studied to identify sources of heterogeneity. Literature databases were searched for peer-reviewed articles published between 1946 and 2022. A Master of Science thesis was also included. Five, 21, and 19 original publications were quantitatively evaluated in 3 separate meta-analyses, based on predefined selection criteria. Two-level and 3-level random-effects meta-analysis revealed a significant overall effect of heat treatment on colostral viscosity and IgG concentration, and serum IgG concentration in newborns. Heat-treated colostrum had significantly higher viscosity (21.0 cP, 95% CI: 3.8 to 38.2) and lower IgG concentration (-7.4 g/L, 95% CI: -11.1 to -3.7) compared with raw colostrum. Overall, newborn calves fed heat-treated colostrum had higher serum IgG concentrations (2.8 g/L, 95% CI: 1.4 to 4.0) 24-48 h after birth than those fed with raw colostrum. Particularly, this positive effect on the serum IgG concentrations was seen when colostrum was heat-treated at ≤60°C (2.9 g/L, 95% CI: 0.9 to 4.2) and when the standard low-temperature low-time (LTLT) method was used for heat treatment (2.6 g/L, 95% CI: 0.1 to 5.1). Colostrum treated at >60-63.5°C tended to have higher viscosity (275.6 cP, 95% CI: -37.9 to 589.3) and had lower IgG concentration (-21.7 g/L, 95% CI: -27.3 to -16.1). Calves fed colostrum treated at this temperature range had significantly lower serum IgG (-4.2 g/L, 95% CI: -7.9 to -0.4) compared with those fed raw colostrum. Heat treatment of colostrum at 72-76°C was not associated with a significant increase in colostral viscosity (6.3 cP, 95% CI: -324.3 to 336.9) nor a reduction in IgG colostral concentration (-13.1 g/L, 95% CI: -26.5 to 0.2), but calves fed colostrum treated at this temperature range had a significant reduction in serum IgG (-11.3 g/L, 95% CI: -17.1 to -5.4). Feeding newborn calves with colostrum heat-treated at ≤60°C by the standard LTLT method, particularly within 2 h after birth, resulted in increased serum IgG concentration at 24-48 h of age. Importantly, delaying feeding of heat-treated colostrum to newborns beyond 2 h of age resulted in no significant difference in IgG serum levels compared with feeding raw colostrum, highlighting the importance of early administration of heat-treated colostrum to favor TPI. On-farm colostrum heat treating should achieve an equilibrium between pathogen elimination and the preservation of colostral immunoglobulins while minimizing undesired increases in viscosity. The beneficial effects of colostrum heat treatment on TPI can be negligible if colostrum feeding is not performed within 2 h after birth.

Colostrum Management: Keys to Optimizing Output and Uptake of Immunoglobulin G

Colostrum is essential for the health and wellbeing of dairy cattle. This review provides insight into different means of augmenting or enhancing colostrum quality including colostrum feeding, dry cow management, prepartum cow diets, freezing, pasteurization, colostrum additives, and colostrum replacers. Other components in colostrum such as maternal cells and their importance are discussed. New research is needed regarding the components in colostrum (bioactive peptides and growth factors) and their effects on the neonate. Colostrum replacers and a prediction equation to estimate colostrum quality are reviewed.

Heat treatment of colostrum at 60°C decreases colostrum immunoglobulins but increases serum immunoglobulins and serum total protein: A meta-analysis

Calves are born hypogammaglobulinemic; thus, the newborn calf's immune defense relies on the ingestion and absorption of colostrum, which provides energy, immunoglobulins, immune cells, and cytokines to the newborn calf. A heat treatment applied to colostrum for 60 min at 60°C has been found to be effective at reducing the total bacterial count while preserving the colostrum IgG levels. The objective of this work was to perform a meta-analysis on the association between the characteristics of heat-treated colostrum and the concentration of colostrum IgG, serum IgG concentration, and serum total protein (STP). A meta-analysis was carried out based on existing peer-reviewed literature. Publications comparing colostrum IgG, serum IgG, and STP for heat-treated or raw frozen colostrum were included. The different heating temperatures applied to the colostrum were divided into 2 subgroups: high temperature (HT; > 60°C) and low temperature (LT; ≤ 60°C). Twelve studies, including 21 trials, met the inclusion criteria for colostrum IgG concentration. The results indicated decreases in colostrum IgG by 20.6 g/L [95% confidence interval (CI) = 11.8-29.4] for HT and 5.38 g/L (95% CI = 2.9-7.8) for LT when colostrum was heat-treated compared with raw or frozen colostrum. Heterogeneity was high to moderate (I² = 82% for HT and 65% for LT). The heat treatment of colostrum was also associated with a nonsignificant decrease in serum IgG by 3.40 g/L for HT (95% CI = 7.54-0.74) but a significant increase in serum IgG by 2.65 g/L for LT (95% CI = 1.51-3.79). The regression model indicated that heterogeneity was not explained by any moderators. The heat treatment of colostrum was also associated with a significant increase in STP by 0.21 g/dL for LT (95% CI = 0.07-0.35). In conclusion, the present work demonstrated that the heat treatment of colostrum ≤60°C decreased colostrum IgG by 5.38 g/L for LT and increased serum IgG by 2.65 g/L and STP by 0.21 g/dL. When compared with the range of values observed in the field for serum IgG, the present results are of high interest for the cattle industry. Because immune colostrum benefits also include cytokines and immune cells, further work is required to evaluate the effect of colostrum heat treatment on these 2 immune components of colostrum.

Influence of first colostrum pasteurization on serum immunoglobulin G, iron, and activity of gamma-glutamyltransferase in newborn dairy calves

Background and Aim:

Colostrum pasteurization is an established procedure in dairy farms in developed countries. This practice can improve the health status of the offspring by reducing several pathogens. This study aimed to focus on the pasteurization of bovine first colostrum and its influence on certain important bioactive components.

Materials and Methods:

This study was conducted in Holstein-Friesian bull calves, which were randomly divided into two groups and fed with 6 L of untreated (UT, n=10) or 6 L of heat-treated (HT, 63.5°C for 30 min, n=10) colostrum from their own dam within the first 12 h after birth. Blood samples were taken before, 24 h, and 48 h after first colostrum intake to determine the concentrations of immunoglobulin G (IgG) and iron and the activity of gamma-glutamyltransferase (GGT) in the serum.

Results:

The level of IgG was not affected by pasteurization (p=0.19). However, a slower increase in GGT activity (p<0.05) and a lower serum iron concentration (p=0.04) were observed in the HT group.

Conclusion:

It can be concluded that pasteurization influences the absorption of colostrum components and therefore, the passive transfer of immunity, although the level of IgG was not affected by pasteurization in this study.

A Scoping Review of On-Farm Colostrum Management Practices for Optimal Transfer of Immunity in Dairy Calves

Newborn calves are agammaglobulinemic and rely for their first immune protection almost completely on the transfer of immune constituents via colostrum. Inadequate colostrum management practices such as on-farm colostrum storage practices and colostrum feeding methods could affect immune components in colostrum and subsequently immune status of the newborn calf. We conducted a scoping review to identify all literature on the interactions between several colostrum management factors and immunological colostrum quality and passive transfer of immunity. Three major stages were defined: milking methods, colostrum treatment and storage, and administration procedures. Separate CAB Abstracts searches were performed for each of the subjects of interest. The search process was completed on November 9, 2020. Colostrum should be milked as soon as possible, as IgG concentration diminishes over time, probably due to dilution. To minimize bacterial contamination, it is advised to pasteurize colostrum in small batches at maximal 60°C for 30 or 60 min. Freeze/thawing of colostrum does not or only slightly affect IgG concentrations, as long as thawing is done au bain-marie and temperature does not exceed 40°C. In on-farm situations, it is difficult to determine the volume that should be fed as the variables contributing to the absorption of IgG by the newborn calf are many and include the quality of the colostrum, the bacterial contamination, the time interval between birth and first moment of feeding and the weight of the calf. Despite all knowledge regarding optimal colostrum management strategies, it remains challenging to predict the effects of certain colostrum management choices in field conditions. Therefore, we recommend measuring the colostral quality, weighing the newborn calf, adjusting the feeding volume accordingly to ensure optimal colostrum intake for each calf.

NEONATAL INTENSIVE CARE OF 10 HOSPITALIZED GIRAFFE CALVES (GIRAFFA CAMELOPARDALIS) REQUIRING HAND-REARING

This retrospective case series describes the clinicopathologic findings, diagnoses, treatment, and outcomes of 10 hand-reared newborn giraffe (Giraffa camelopardalis) calves admitted to a university teaching hospital for intensive care. Ten calves (five males, five females; nine reticulated giraffes [Giraffa camelopardalis reticulata], one Masai giraffe [G. c. tippelskirchi]), were admitted under 2 days of age. Inadequate transfer of passive immunity was suspected in 5 of 10 calves based on assessment of serum total solids and globulin values. These calves were treated with oral frozen bovine colostrum and/or intravenous hyperimmune bovine plasma. Diarrhea occurred in 6 of 10 calves and was managed with supportive care, fecal microbiota transplantation, and limiting milk intake (offering 10% body weight [BW] in milk per day, while feeding <2 L per meal at 2- to 4-hr intervals). Less common diagnoses included pneumonia (n = 3) and mycoplasma-associated septic arthritis (n = 1). Eight calves received systemic antimicrobial therapy. Hyperlactatemia (lactate > 5 mmol/L; n = 8) and hypercreatininemia (creatinine > 2.0 mg/dl, n = 7) were the most common presenting laboratory abnormalities, which resolved with intravenous fluid therapy. All neonatal giraffes survived to discharge after a median hospitalization of 9.5 days (range, 5-37 days) and were successfully hand-reared at their place of birth. In conclusion, neonatal giraffe calves can be intensively managed in a hospital environment. Diarrhea was a common clinical problem and can be related to feeding regimens. Intravenous hyperimmune bovine plasma infusion was well tolerated to manage failure of transfer of passive immunity in calves with inadequate colostrum administration. The current study supports that compromised neonatal giraffe calves may carry an excellent prognosis after early, intensive intervention.

Composition and Factors Affecting Quality of Bovine Colostrum: A Review

Simple Summary

In an attempt to improve the most important production traits of dairy cows, breeders omit the problem of calf rearing, whose regularity has a major impact on subsequent dairy and reproductive use. Therefore, it should be made clear to farmers that one of the ways to improve profitability is to improve the quality of colostrum. The most critical time for calves is the first 2 weeks, when the most falls occur, which may result from disorders of the digestive system and contribute to poor quality of colostrum or poor husbandry. Colostrum possesses a number of properties, such as nourishing, energetic, protective, but also purgative. It activates peristalsis, thus the excretion of meconium, therefore preventing its excessive densification and problems with excretion. Colostrum contains bioactive components with immune enhancing properties: Immunoglobulins, lactoferrin, lysozyme, lactoperoxidase, α-lactalbumin, β-lactoglobulin, or fat that carries important vitamins and polyunsaturated fatty acids. The concentration of the above-mentioned compounds is variable and depends on many factors, including breed, productivity, parity, feeding intensity, season of the year, and/or production system.

Abstract

Colostrum as a secretion of the mammary gland is produced and accumulated in the final stage of pregnancy and in the first days after calving. It is designed to provide the calf with the necessary nutrients and biologically active ingredients. One of the most difficult periods in the life of animals is their rearing, and the most sensitive are the first days after birth. This is the time when most falls occur, and they are caused by mortality and morbidity, even at the level of 30%. Such losses affect the performance and profitability of animal production (the percentage of animals intended for reproduction or fattening is reduced and the intensity of selection in the herd is also reduced). Both diseases and mortality are the cause of serious economic, production, and breeding losses, which are the result of weak immune mechanisms. The adaptability of calves to the environment is determined by their immune status. Colostrum has a regulating function and stimulates the young organism to grow, and it has properties that support the functioning of systems: Endocrine and immunological. For colostrum to fulfil its role, it must be administered immediately after birth, because the immunoglobulins it contains are absorbed during the first 16–27 h after the birth of the calf, preferably within 2–4 h of age. Blood from calves that have been properly calved should have an antibody concentration of 15g/L (24–48 h of age). Therefore, immunoglobulins are the most important factor affecting infectious immunity; an adequate concentration of immunoglobulins in calves’ blood is related to their survival and health. It is the intent of this review to synthesize and summarize the information currently available on colostrum, as well as to discuss the interpretation of the results.

Colostrum Management for Dairy Calves

Colostrum management is the single most important management factor in determining calf health and survival. Additional benefits of good colostrum management include improved rate of gain and future productivity. Successful colostrum management requires producers to provide calves with a sufficient volume of clean, high-quality colostrum within the first few hours of life. This article reviews the process of colostrogenesis and colostrum composition, and discusses key components in developing a successful colostrum management program. In addition, the article discusses approaches for monitoring and proposes new goals for passive immunity in dairy herds.

Associations between management practices and colostrum quality on New Zealand dairy farms

AIMS

To describe colostrum quality in spring-calving dairy herds in New Zealand, in terms of Brix, pH and total and coliform bacterial counts and to investigate associations between farm management practices and these measures of colostrum quality.

METHODS

In June 2015, commercial dairy farms (n=105), located in North and South Islands of New Zealand, were visited shortly after the first cows had calved, and when approximately 50% and 80% of the herd had calved (early, middle and late visits). One litre of pooled colostrum that was being fed to newborn calves was collected at each visit and used to determine Brix, pH, total bacterial and coliform counts. A survey of calf management practices was conducted with the herd manager or calf rearer after the final visit.

RESULTS

Of 298 pooled colostrum samples tested 29/298 (9.7%) had Brix >22%. Brix was higher on farms where calves were picked up twice daily compared with once daily (18.2 (95% CI=16.5-19.9)% vs. 15.9% (95% CI=15.2-16.6)%; p=0.012), and was lower where first milking colostrum was combined with colostrum obtained at later milkings (15.0 (95% CI=13.9-16.1)%) compared with where it was not (16.9 (95% CI=16.3-17.6)%; p=0.002). Vaccination of all cows against calf diarrhoeal pathogens was associated with increased Brix compared with no vaccination (18.1 (95% CI=16.6-19.6)% vs. 16.3 (95% CI=15.6-17.0)%; p=0.033). Mean pH of samples tested decreased from 5.97 (95% CI=5.84-6.09) to 5.58 (95% CI=5.45-5.71) for early and late-season visits, respectively (p<0.001). Of 268 samples tested, 23 (8.6%) had bacterial counts below the recommended threshold of 1.00×10⁵ cfu/mL. Mean bacterial counts increased from 2.75 (95% CI=1.80-3.70)×10⁸ to 4.99 (95% CI=3.95-6.03)×10⁸ cfu/mL for early and late-season visits, respectively (p<0.001). Of 259 samples tested, 23 (8.9%) had coliform counts below the recommended threshold of 1.00×10⁴ cfu/mL.

CONCLUSIONS AND CLINICAL RELEVANCE

On a large majority of dairy farms included in this study the pooled colostrum fed to newborn calves had sub-optimal Brix and excessive bacterial counts. Farm-level risk factors such as twice daily pick up of calves from the paddocks, herd vaccination and feeding pooled colostrum that did not combine colostrum obtained at later milkings with first milking colostrum were associated with colostrum quality measures.

Comparison of immune responses in calves fed heat-treated or unheated colostrum

Understanding the mechanisms that underlie neonatal immune function is important for appropriately treating and preventing disease. Cytokines provided in colostrum may affect immune development and function, but data describing cytokine absorption in calves and the effects of colostrum heat treatment on absorption are limited. The objectives of this experiment were to characterize immune responses in calves that received heat-treated (HT) or unheated (UH) colostrum (in terms of growth, rectal temperature, and blood cytokine and IgG concentrations) and to determine calves' ability to absorb IFNγ and IL1β from HT and UH colostrum. A single large batch of colostrum was divided to create treatments. The HT colostrum was heated to 60°C for 60 min. Both treatments were frozen until needed and warmed immediately before feeding. Bull calves (n = 26) were randomly assigned to receive 8% of their birth weight in colostrum from 1 treatment at birth. Blood was collected at 0 and 24 to 48 h after birth for IL1β, IFNγ, and IgG analyses. Subcutaneous injections of ovalbumin (5.0 mg/mL) were given at 14 and 35 ± 3 d of age. Rectal temperature and growth were monitored for 10 d following each injection. Plasma samples were collected at 0, 4, 8, and 12 h post-injection and daily for the subsequent 10 d to measure IL1β, IFNγ, and IgG concentrations. Colostrum heat treatment failed to increase blood IgG concentrations or the apparent efficiency of IgG absorption. Serum IL1β concentrations were higher in UH calves 24 to 48 h after birth and remained higher than those in HT calves through 15 d of age. Both IFNγ and IgG increased in response to ovalbumin injection; we observed no differences between treatments. Rectal temperature increased and peaked 12 h after injection at 14 and 35 d. Growth rate was reduced by exposure to the foreign antigen. Interactions of calf age and colostrum treatment with time post-injection indicate that calves tended to show greater loss in average daily gain at 35 d than at 14 d, and UH calves tended to recover greater rates of growth 6 to 10 d after receiving ovalbumin injection. Thus, feeding HT colostrum did not inhibit neonatal immune response, but it may have affected recovery from exogenous antigen challenge.

Effect of quality of colostrum on health, growth and immunoglobulin G concentration in Holstein calves in a hot environment

The aim of this study was to determine the effect of ingestion of pasteurized and subsequently frozen–thawed pooled colostrum (≥50 mg Ig/mL) with different bacterial counts and immunoglobulin concentration (IgC) on the occurrence of diarrhea and pneumonia in 306 neonatal Holstein calves in a hot environment. Calves were assigned to be fed colostrum with total bacterial counts (TBC) lower or greater than 100 000 colony‐forming units (cfu)/mL, total coliform counts (TCC) greater or lower than 10 000 cfu/mL, and IgC lower or higher than 85 mg Ig/mL. Calves fed colostrum with TBC ≥100 000 cfu/mL were more likely (risk ratio 1.34, confidence interval 1.05–1.71; P < 0.05) to present pneumonia than calves receiving colostrum with lower TBC (incidence 53.2 vs. 39.8%). Calves fed colostrum with high TCC had increased chances of suffering pneumonia (51.4 vs. 42.1%; P < 0.05) than calves fed colostrum with lower TCC. Calves fed colostrum with ≥85 mg Ig/mL tended to present higher daily weight gain (505 ± 113 vs. 484 ± 126 g; P = 0.09). TBC and TCC in colostrum did not influence the incidence rate of diarrhea. It was concluded that under the conditions of the present study, heavy contamination of on‐farm pasteurized frozen–thawed colostrum is seemingly unavoidable and this contamination poses a threat for pneumonia, but not for diarrhea.

Risk for the development of Antimicrobial Resistance (AMR) due to feeding of calves with milk containing residues of antibiotics

EFSA was requested to: 1) assess the risk for the development of antimicrobial resistance (AMR) due to feeding on farm of calves with colostrum potentially containing residues of antibiotics; 2) assess the risk for the development of AMR due to feeding on farm of calves with milk of cows treated during lactation with an antibiotic and milked during the withdrawal period, and 3) propose possible options to mitigate the risk for the development of AMR derived from such practices. Treatment of dairy cows during the dry period and during lactation is common in the EU Member States. Penicillins, alone or in combination with aminoglycosides, and cephalosporins are most commonly used. Residue levels of antimicrobials decrease with the length of the dry period. When the interval from the start of the drying-off treatment until calving is as long as or longer than the minimum specified in the Summary of Product Characteristics of the antimicrobial, faecal shedding of antimicrobial-resistant bacteria will not increase when calves are fed colostrum from treated cows. Milk from cows receiving antimicrobial treatment during lactation contains substantial residues during the treatment and withdrawal period. Consumption of such milk will lead to increased faecal shedding of antimicrobial-resistant bacteria by calves. A range of possible options exist for restricting the feeding of such milk to calves, which could be targeting the highest priority critically important antimicrobials. β-Lactamases can reduce the concentration of β-lactams which are the most frequently used antimicrobials in milking cows. Options to mitigate the presence of resistant bacteria in raw milk or colostrum are mainly based on thermal inactivation.

A Randomized Clinical Trial Evaluating the Effects of Oligosaccharides on Transfer of Passive Immunity in Neonatal Dairy Calves

Background

Bacterial contamination of colostrum is common and can decrease IgG absorption in neonatal calves. Strategies that mitigate this situation without complicating colostrum management will benefit dairy calf health and survival.

Objectives

To evaluate the effects of supplementing colostrum with oligosaccharides (OS) on serum IgG concentration and apparent efficiency of absorption of IgG (AEA%) in calves fed unpasteurized colostrum and characterize these outcomes with respect to colostrum bacterial exposures.

Animals

One hundred twenty‐three neonatal dairy calves.

Methods

Randomized, blinded, controlled clinical trial conducted at a commercial dairy operation. Calves were enrolled at birth in 1 of 4 treatment groups. Data were complete for 123 calves, which were distributed across the treatment groups as follows: mannan‐oligosaccharides (MOS), n = 33; Saccharomyces galacto‐oligosaccharides (SGOS), n = 31; Bifidobacterium galacto‐oligosaccharides (BGOS), n = 28; and lactose control (CON), n = 31. A commercial radial immunodiffusion kit was used to determine colostrum and serum IgG concentrations. Conventional microbiology methods were used to enumerate colostrum bacterial counts.

Results

Bacterial counts were not significantly different among treatment groups. Total bacterial plate counts (TPC) were relatively low for the majority of colostrum samples, but TPC had a significant negative effect on serum IgG concentration and AEA% in the lactose‐supplemented control group but not the OS treatment groups.

Conclusions and Clinical Importance

These results suggest that a complement of OS structures may mitigate adverse effects of bacteria on transfer of passive immunity (TPI).

Effect of feeding heat-treated colostrum on risk for infection with Mycobacterium avium ssp. paratuberculosis, milk production, and longevity in Holstein dairy cows

In summer 2007, a randomized controlled field trial was initiated on 6 large Midwest commercial dairy farms to investigate the effect of feeding heat-treated (HT) colostrum on transmission of Mycobacterium avium ssp. paratuberculosis (MAP) and on future milk production and longevity within the herd. On each farm, colostrum was collected daily from fresh cows, pooled, divided into 2 aliquots, and then 1 aliquot was heat-treated in a commercial batch pasteurizer at 60°C for 60min. A sample from each batch of colostrum was collected for PCR testing (MAP-positive vs. MAP-negative). Newborn heifer calves were removed from the dam within 30 to 60min of birth and systematically assigned to be fed 3.8 L of either fresh (FR; n=434) or heat-treated (HT; n=490) colostrum within 2h of birth. After reaching adulthood (>2 yr old), study animals were tested once annually for 3 yr (2010, 2011, 2012) for infection with MAP using serum ELISA and fecal culture. Lactation records describing milk production data and death or culling events were collected during the 3-yr testing period. Multivariable model logistic and linear regression was used to investigate the effect of feeding HT colostrum on risk for testing positive to MAP during the 3-yr testing period (positive/negative; logistic regression) and on first and second lactation milk yield (kg/cow; linear regression), respectively. Cox proportional hazards regression was used to investigate the effect of feeding HT colostrum on risk and time to removal from the herd. Fifteen percent of all study animals were fed PCR-positive colostrum. By the end of the 3-yr testing period, no difference was noted in the proportion of animals testing positive for MAP, with either serum ELISA or fecal culture, when comparing the HT group (10.5%) versus the FR group (8.1%). There was no effect of treatment on first- (HT=11.797kg; FR=11,671kg) or second-lactation (HT=11,013kg; FR=11,235kg) milk production. The proportion of cows leaving the herd by study conclusion was not different for animals originally fed HT (68.0%) versus FR (71.7%) colostrum. Although a previous study showed that feeding HT colostrum (60°C for 60min) produces short-term benefits, including improved passive transfer of IgG and reduced morbidity in the preweaning period, the current study found no benefit of feeding HT colostrum on long-term outcomes including risk for transmission of Mycobacterium avium ssp. paratuberculosis, milk production in the first and second lactation, and longevity within the herd.