Alteration of cellular immune responses by nutrition and weaning in calves

Commercial Dairy Calf Management: Impact on Performance and Health

The transition for the calf from the milk-feeding phase to the grouping and dry feed feeding phase is the second most difficult time for a calf, with the most difficult life phase being parturition and the first day of life. Reducing these stress factors directly relates to reduced health problems and better performance during subsequent life phases. This review will discuss some of the key management factors associated with achieving maximum production potential for the commercial dairy calf.

Weaning age affects growth, feed intake, gastrointestinal development, and behavior in Holstein calves fed an elevated plane of nutrition during the preweaning stage

Recent research has revealed potential advantages of feeding an elevated plane of nutrition to calves during the preweaning period. However, calves fed more nutrients preweaning may be more susceptible to depressed growth and weaning stress during the transition from liquid to solid feed. The objective of this study was to investigate the relationship between the age of weaning and feed intake, and its influence on growth, gastrointestinal development, and behavioral indicators in dairy calves fed an elevated plane of nutrition during the preweaning period. To meet this objective, 20 female Holstein calves were randomly assigned at birth to be weaned at 6 or 8 wk. Milk replacer (mixed at 150 g/L) was offered at 1.2 kg/calf per day in 2 meals until a 1-wk step-down, when meals were reduced by 50% 1 wk before weaning. Daily starter, chopped oat straw, water intake, and weekly body weights were measured until d 70 of life. To assess digestive tract development, rumen fluid, fecal, and blood samples were taken before and after weaning (d 35, 49, and 63) and analyzed for ruminal short-chain fatty acids, blood β-hydroxybutyrate, and fecal starch, respectively. Behavioral indicators of weaning stress, including vocalizing and non-nutritive oral behavior, were measured by visual observation for 1 h, 3 times per week, before the second feeding of the day during the period from 2 wk before weaning to 2 wk after weaning. The calves weaned at 8 wk compared with 6 wk had higher average daily gain for the week preweaning (0.79±0.09 vs. 0.34±0.10 kg/d) and postweaning (1.05±0.09 vs. 0.35±0.11 kg/d), and were heavier at d 70 (99.9±1.81 vs. 91.0±2.26 kg). From 5 to 8 wk of age, starter and water intakes were lower in calves weaned at 8 wk of age. However, overall starter intake did not differ during the last week of the experiment. Furthermore, calves weaned at 8 wk compared with 6 wk had higher starter intake for 1 wk preweaning (1.36±0.13 vs. 0.40±0.08 kg/d) and postweaning (2.51±0.20 vs. 1.16±0.15 kg/d). In both treatments, weaning increased ruminal short-chain fatty acids, blood β-hydroxybutyrate, and fecal starch, yet the differences between the week before and after weaning were greater for calves weaned at 6 wk compared with those weaned at 8 wk. Treatment × week relative to weaning interactions indicated that several behaviors varied between early- and later-weaned calves during the week before weaning; calves weaned at 6 wk tended to exhibit 75% more non-nutritive oral behavior and spent 55% less time ruminating, and 36% less time lying compared with calves weaned at 8 wk. Under the conditions of this study, the results suggest that calves fed an elevated plane of nutrition preweaning have higher starter intakes and average daily gain during the weaning period when weaning is extended from 6 to 8 wk of age.

Effect of age at weaning on the physiological stress response and temperament of two beef cattle breeds

The study was conducted to evaluate the effect of age at weaning and breed on the stress response of calves to weaning and their temperament. At calving, 14 Parda de Montaña calves and 14 Pirenaica calves were randomly assigned to either early weaning (at 90 days) or traditional weaning (at 150 days) treatment. During nursing, calves were allowed to suckle their dams twice a day for 30 min. After weaning, calves were placed in an adjacent barn without access to their dams, where they remained for 7 days. On day 8 after weaning, they were transported to a feedlot where they received an intensive diet. Blood samples were taken 168 h before weaning (baseline) and 6, 24, 48 and 168 h after weaning for cortisol, fibrinogen and haematology analyses, and temperament was measured 90 and 180 days after weaning with the flight speed test. Cortisol concentration increased after weaning, irrespective of age at weaning. Early-weaned calves had a lower fibrinogen baseline and a greater increase in fibrinogen concentrations 48 h after weaning than traditionally weaned calves. Moreover, fibrinogen concentration returned to baseline values 168 h after weaning in traditionally weaned calves, whereas it remained high in early-weaned calves. Concerning breed effects, Pirenaica calves had higher cortisol concentration and fibrinogen increments after weaning than Parda de Montaña calves. Slight alterations occurred after weaning in haematology, but all parameters returned to baseline values 168 h after weaning, with no significant effects of age at weaning or breed. Despite the absence of clinical signs, early-weaned calves of both breeds suffered marginal anaemia, according to haemoglobin values. Regardless of age at weaning, Pirenaica calves had greater reactivity to human presence than Parda de Montaña calves, according to their higher flight speed values measured. Finally, early-weaned calves were lighter than traditionally weaned calves at weaning, but had similar weight gains in the feedlot. Consequently, they needed an additional 40 days to reach the target weight, irrespective of breed. Therefore, age at weaning had no major effects on the stress response to weaning or temperament, but early weaning increased the length of the feedlot period. On the other hand, Pirenaica calves were more reactive than Parda de Montaña calves to the stress of weaning and human presence.

Influence of Stress and Nutrition on Cattle Immunity

Today, the scientific community readily embraces the fact that stress and nutrition impact every physiologic process in the body. At last, the specific mechanisms by which stress and nutrition affect the immune function are being elucidated. The debate among animal scientists concerning the definition and quantification of stress as it relates to animal productivity and well-being is ongoing. However, an increased appreciation and understanding of the effects of stress on livestock production has emerged throughout the scientific community and with livestock producers. The intent of this article is to provide an overview of the general concepts of stress and immunology, and to review the effects of stress and nutrition on the immune system of cattle.

Pre- and Postweaning Performance of Holstein Female Calves Fed Milk Through Step-Down and Conventional Methods

Milk consumption, dry feed intake, body weight (BW) gain, occurrence of diarrhea, and selected blood metabolites were studied in female Holstein calves fed milk either through conventional or step-down (STEP) methods. In conventional method, the calves (n = 20) were fed colostrum and then milk at the rate of 10% of BW for the entire period of 45 d. In STEP method, the calves (n = 20) were given colostrum and then milk for 25 d at the rate of 20% of BW, which was reduced (between d 26 to 30) to 10% of BW for the remaining 15 d. The calves fed through conventional and STEP methods were weaned gradually by diluting milk with water between d 46 and 50. Feed intake and BW of the calves were monitored until 90 d of age. The STEP calves consumed 92.3, 19.4, and 62.4% more milk than conventionally fed calves during pre-STEP (d 1 to 30), post-STEP (d 31 to 50), and preweaning (d 1 to 50) periods, respectively. Consumption of starter and hay were greater during the pre-STEP period and lesser during the post-STEP and postweaning (d 51 to 90) periods in calves provided milk using conventional method compared with STEP-fed calves. Body weight gain, dry matter intake, and feed efficiency of calves were greater in those on the STEP method than on the conventional method. Lesser blood glucose and greater blood urea nitrogen at weaning (d 50) and postweaning (d 60) possibly indicated a better functioning rumen in calves fed milk through The STEP method than those fed conventionally. Occurrence of diarrhea was higher during wk 3 and 4 of age in calves fed milk through conventional method compared with STEP-fed calves. In conclusion, STEP milk feeding may prevent the problems of depressed solid feed intake associated with ad libitum milk feeding and of poor BW gain with conventional milk feeding in dairy calves.

High Growth Rate Fails to Enhance Adaptive Immune Responses of Neonatal Calves and Is Associated with Reduced Lymphocyte Viability

The objective of the study was to evaluate the effects of 3 targeted growth rates on adaptive (i.e., antigen-specific) immune responses of preruminant, milk replacer-fed calves. Calves (9.1 +/- 2.4 d of age) were assigned randomly to one of 3 dietary treatments to achieve 3 targeted daily rates of gain [no growth (maintenance) = 0.0 kg/d, low growth = 0.55 kg/d, or high growth = 1.2 kg/d] over an 8-wk period. The NRC Nutrient Requirements of Dairy Cattle calf model computer program was used to estimate the milk replacer intakes needed to achieve target growth rates. All calves were fed a 30% crude protein, 20% fat, all-milk protein milk replacer reconstituted to 14% dry matter. Diets were formulated to ensure that protein would not be limiting. All calves were vaccinated 3 wk after initiation of dietary treatments with Mycobacterium bovis, strain bacillus Calmette-Guerin and ovalbumin. Growth rates for no-growth (0.11 kg/d), low-growth (0.58 kg/d), and high-growth (1.16 kg/d) calves differed throughout the experimental period. Blood glucose concentrations in high-growth calves increased with time and were higher than in low- and no-growth calves. Mononuclear and polymorphonuclear leukocyte percentages in peripheral blood were unaffected by growth rate but did change with advancing age. Percentages of CD4(+) T cells increased with age in no-growth and low-growth calves, a characteristic of maturation, but failed to increase in high-growth calves. Growth rate did not affect the percentages of CD45RO(+) (memory) CD4(+) and CD8(+) T cells, antigen (i.e., ovalbumin)-specific serum IgG concentrations, or antigen (i.e., purified protein derivative)-induced IFN-gamma and nitric oxide secretion by mononuclear cell cultures. Antigen-elicited cutaneous delayed-type hypersensitivity responses of no-growth calves exceeded responses of low-growth, but not high-growth, calves. In resting- and antigen-stimulated cell cultures, viabilities of CD4(+), CD8(+), and gammadeltaTCR(+) T cells from high-growth calves were lower than those of the same T cell subsets from no-growth and low-growth calves. Alternatively, resting cultures of mononuclear leukocytes from high-growth calves produced more nitric oxide than those from no-growth and low-growth calves. In conclusion, adaptive immune responses were affected minimally by growth rate. The results suggest that protein-energy malnutrition in the absence of weight loss is not detrimental to antigen-specific responses of neonatal vaccinated calves and that a high growth rate does not enhance these responses. The negative effect of a high growth rate on the viability of circulating T cell populations may influence infectious disease resistance of the calf.

Calf Respiratory Disease and Pen Microenvironments in Naturally Ventilated Calf Barns in Winter

Relationships between air quality, a variety of environmental risk factors, and calf respiratory health were studied in 13 naturally ventilated calf barns during winter. A minimum of 12 preweaned calves were randomly selected and scored for the presence of respiratory disease in each barn. An air sampling device was used to determine airborne bacteria colony-forming units per cubic meter (cfu/m3) of air in calf pens and central alleys within the barns. Airborne bacteria samples were collected on sheep blood agar (BAP) and eosin methylene blue (EMB) agar plates. Temperature and relative humidity were recorded in each calf pen, the barn alley, and outside the barn. Samples of bedding were collected in each pen and DM was measured. Pen bedding type and a calf nesting score (degree to which the calves could nestle into the bedding) was assigned to each barn. Calf numbers, barn and pen dimensions, ridge, eave, and curtain openings, and exterior wind speed and direction were determined and used to estimate building ventilation rates. Factors that were significantly associated with a reduced prevalence of respiratory disease were reduced pen bacterial counts (log10 cfu/m3) on BAP, presence of a solid barrier between each calf pen, and increased ability to nest. Individual calf pen bacterial counts were significantly different from barn alley bacterial counts on both BAP and EMB. Significant factors associated with reduced calf pen bacterial counts on BAP were increasing pen area, increasing number of open planes of the calf pen, decreasing pen temperature, and wood-particle bedding. Significant factors associated with reduced alley bacterial counts on BAP were increased ventilation changes per hour, increased barn volume per kilogram of calf, reduced pen bacterial counts, and barn type.

Economic analysis of feeding pasteurized nonsaleable milk versus conventional milk replacer to dairy calves

OBJECTIVE

To determine growth, morbidity, and mortality rates in dairy calves fed pasteurized nonsaleable milk versus commercial milk replacer and compare economics of feeding pasteurized nonsaleable milk versus commercial milk replacer in dairy calves.

DESIGN

Clinical trial.

ANIMALS

438 dairy calves.

PROCEDURE

Calves were assigned at 1 to 2 days of age to be fed pasteurized nonsaleable milk or a commercial milk replacer until weaned. Body weight was measured at the time of study enrollment and at the time of weaning, and any medical treatments administered and deaths that occurred prior to weaning were recorded. A partial budget model was developed to examine the economics of feeding pasteurized nonsaleable milk versus commercial milk replacer.

RESULTS

Calves fed conventional milk replacer had significantly lower rates of gain (-0.12 kg/d [-0.26 lb/d]), lower weaning weights (-5.6 kg [-12.3 lb]), higher risk for treatment during the summer and winter months (odds ratio [OR], 3.99), and higher risk of death during the winter months (OR, 29.81) than did calves fed pasteurized nonsaleable milk. The estimated savings of feeding pasteurized nonsaleable milk, compared with milk replacer, was dollars 0.69/calf per day. The estimated number of calves needed to economically justify the nonsaleable milk pasteurization system was 23 calves/d.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that dairy calves fed pasteurized nonsaleable milk have a higher growth rate and lower morbidity and mortality rates than do calves fed conventional milk replacer. Feeding pasteurized nonsaleable milk could be an economically viable strategy for dairy calf producers.

Effects of ad libitum milk intake on dairy calves

Conventional milk feeding for calves (by bucket twice daily at a total of 10% of body weight) was compared with feeding milk for ad libitum consumption from a nipple. Calves were weaned gradually between d 37 and 42 by diluting the milk with water, and body weight and feed consumption were followed until d 63. Calves fed ad libitum drank 89% more milk than calves fed conventionally during the preweaning period, but the ad libitum-fed calves ate only 16% as much calf starter and 17% as much hay. Consumption of starter and hay increased rapidly after weaning, and treatment differences disappeared. Probably as a result of the much higher intake of milk, the ad libitum-fed calves gained 63% more weight than the conventionally fed calves before weaning, resulting in a 10.5-kg weight advantage on d 35. During and immediately after weaning, the rate of weight gain slowed for both treatment groups, but recovered by approximaely d 49. There were no treatment differences in weight gains over the weaning or postweaning periods, and at the end of the experiment on d 63, the calves fed ad libitum maintained an advantage in mean (+/- SEM) body weight (89.07 +/- 2.47 kg vs 81.07 +/- 2.47 kg for the conventionally fed calves). Incidence of diarrhea was low and did not differ between treatment groups. We conclude that ad libitum nipple feeding of milk to dairy calves can allow for increased milk intake and weight gain with no detrimental effects on intake of solid food after weaning.

Mycobacterium bovis infection and tuberculosis in cattle

This review considers the possible events that can occur when cattle are exposed to Mycobacterium bovis and, where appropriate, draws on principles accepted for tuberculosis infection in humans and laboratory animal models. Consideration is given to the many complex factors which influence the outcome of challenge with tubercle bacilli. These include features inherent to the mycobacterium, the host and the environment. It is apparent that clinical disease probably occurs only in a relatively small, but undetermined, proportion of cattle that are exposed to Al. bovis. The majority of animals may clear infection or control the bacilli, possibly in a condition of latency. It is concluded that a better understanding of the dynamics of the events following M. bovis exposure and subsequent infection in cattle would be of significant benefit in developing new tools appropriate for disease control and to designing optimal approaches for their application.

Effect of transportation and weaning on humoral immune responses of calves

Transportation exposes cattle to stress and results in increased morbidity and mortality. An investigation was made of the effects of transport and another important stressor, weaning, on the immune function of calves by determining humoral immune responses to keyhole limpet haemocyanin (KLH). In a 2 x 2 factorial designed experiment, suckled calves were either (1) weaned at housing (day 0) and not transported, (2) weaned at housing and transported, (3) weaned while still at pasture nine to 13 days prior to housing and not transported or (4) weaned at pasture and transported. All calves were immunized with KLH at housing (day 0) and serum samples were collected subsequently to determine class and subclass anti-KLH antibody responses (IgG1, IgG2, IgA and IgM) by direct ELISA. Increased anti-KLH IgG1 and IgG2 concentrations were shown in calves that were weaned prior to housing and transported on day 10 (P < 0.05 and P < 0.01 respectively). Transported calves had increased IgG1 concentrations on day 20 (P < 0.05) compared with calves that were not transported. However, calves weaned at housing and not transported had increased IgA and IgM responses on day 30 compared with the other groups of calves (P < 0.05). This study shows that transportation and weaning affect the humoral immune responses of suckler calves and that the effects persist for several weeks. However, the effects of the treatments were not consistent for all antibody classes measured.

Effects of supplemental shade on thermoregulatory response of calves to heat challenge in a hutch environment

Holstein (n = 12) and Guernsey (n = 6) calves, housed in hutches, were used to evaluate the complex relationships among external environment, housing microclimate, and thermal status of calves. The study was conducted during the summer; 9 calves were housed in hutches under supplemental shade, and 9 calves were maintained in hutches under direct sunlight. Environmental and calf temperatures were measured twice daily at 0700 and 1500 h, which included determinations of air temperature, inner and outer surface temperatures of the hutch, rectal and skin temperatures of the calf, and respiration rate. Outer and inner surface temperatures of the hutch were lower under supplemental shade. Hutch air temperature was highly correlated with inner surface temperature and therefore was lower in the shaded environment. During the p.m. period, when heat stress was highest, calves housed in a shaded hutch environment had lower skin temperatures and respiration rates than did unshaded calves. Body temperature and respiration rates increased less for calves in shade than for calves in sun. These data define the relationship between the calf and the environment. Supplemental shade diminished the severity of heat stress experienced by calves that were housed in hutches during the summer.

Effect of dietary restriction on cell-mediated immune responses in cattle infected with Mycobacterium bovis

Nine M. bovis-infected cattle on a diet deficient in both protein and energy for 133 days lost approximately 17% of their original body weight. However, dietary restriction did not result in any significant reduction in skin sensitivity to PPD, in vitro production of IFN-gamma or lymphocyte blastogenesis. The number of circulating BoCD4+ cells and B cells were similar in both the malnourished and the control cattle. However, significantly lower numbers (P < 0.01) of circulating BoCD2+ cells, BoCD8+ cells, WC1+ gamma delta T cells and ACT2+ cells were found in the malnourished cattle. With the exception of inorganic phosphate, the changes in plasma biochemical parameters were unremarkable.

Level of nutrition and age at weaning: effects on humoral immunity in young calves

Thirty-two calves were studied to determine the effects of level of nutrition (400 and 1000 g (air-dry matter) milk substitute per d) and age at weaning (5, 9 and 13 weeks) on humoral immune responses measured in serum and bronchoalveolar washings (BAW). All calves were immunized with Keyhole limpet haemocyanin (KLH) at 3 weeks of age, and with horse erythrocytes (HRBC) 1 d after weaning. Feeding the higher level of nutrition compared with the lower level decreased anti-HRBC titres and serum IgG2 and IgA responses to KLH (P < 0.05). Weaning at 5 compared with 9 weeks of age decreased serum anti-HRBC responses (P < 0.05), but weaning age had no effect on anti-KLH responses (P > 0.05). Feeding the higher level of nutrition increased total protein (P < 0.05) and IgG2 concentrations (P < 0.01) in BAW. The results showed that variation in husbandry conditions that is within conventional limits affects humoral immune responses in young, artificially-reared calves.