Etiology and predisposing factors in respiratory disease of milk-fattened veal calves

Air Quality, Management Practices and Calf Health in Italian Dairy Cattle Farms

Simple Summary

Calf mortality is an important factor of economic loss in dairy operations. Among the factors which can affect calf health, air quality in calf housing has rarely been studied. In the present research, the relations among air quality in the calf pens, management practices, microclimatic conditions and calf health and mortality were studied in 25 Italian dairy cattle farms. Microbial air quality in the calf pens was found to be related to temperature and humidity, design and position of the pen, some management practices and calf health and mortality. Maintaining dry bedding and controlling microclimatic conditions in the calf pen can be useful practices to promote good air microbiological quality in the calf pen, improving calf health and reducing mortality.

Abstract

Among factors that can affect calf health, microbial quality of the pen air is poorly studied. In 25 Italian dairy farms, data concerning air quality in the calf pens, hygiene of pens and equipment, microclimatic conditions, calf health and management were collected during the winter season (January-March 2020 and December-March 2021). The average air Standard Plate Count (SPC) of 85 pens was 4.51 (SD = 0.52) log₁₀ cfu/m³ whereas the average air ammonia concentration was 0.66 (SD = 0.53) ppm. Positive correlations were found between average Temperature Humidity Index (THI) in the pen and air SPC, night maximum THI and air SPC and between SPC and yeast, mould and ammonia concentration in the pen air. The concentrations of E. coli, Enterobacteriaceae and yeasts in the pen air were higher and calf cough increased as the renewal interval of bedding material became longer. High bedding dry matter and low THI were associated with low air SPC, good calf health scores and low mortality. Maintaining low bedding humidity and controlling microclimatic conditions can contribute to enhancing air microbiological quality in the pen and reduce calf diseases and mortality.

Characterizing the literature surrounding transportation of young dairy calves: A scoping review

Transportation is a stressful event for cattle, as it may involve various handling practices, commingling, deprivation of food and water, and fluctuating temperatures. Calves are particularly susceptible to these stressors because their physiological and immune systems are still developing. There has been no formal synthesis of the scientific literature evaluating the effect of transportation on young dairy calf health and performance; the aim of this scoping review is to describe and characterize this body of work. We targeted both descriptive and analytic studies examining transport of calves, including listing how the effect of transport has been evaluated. Eight databases were searched for relevant articles with eligible studies being primary research articles investigating transportation of calves of either sex who were younger than 60 d of age or weighed less than 100 kg. Two reviewers independently screened the title and abstracts of 6,859 articles with 361 potentially relevant articles screened at full text. Of these, 46 were relevant and had data extracted. Articles reporting study location were conducted in the United States (n = 5), Australia (n = 3), Japan (n = 3), and New Zealand (n = 3). Common transport-related variables evaluated included time in transit (n = 13), distance of transportation (n = 8), vehicle-related factors (n = 8), and age at time of transportation (n = 4). Outcome measures varied greatly, including blood parameters (n = 28), health assessments (n = 20), weight (n = 17), behavioral metrics (n = 14), mortality (n = 7), feed intake following transportation (n = 4), salivary cortisol concentrations (n = 3), morbidity (n = 3), and isolation of Salmonella Dublin in fecal samples (n = 2). Outcome parameters were measured during transport or ranged from immediately after to one year following transportation. As the transport-related risk factors and outcomes measured assessed varied widely between studies, future quantitative synthesis (e.g., meta-analysis) in this area may be limited. Several knowledge gaps were identified, including methods to prepare calves for transportation, such as improving nutrition, administering medication, or transporting calves at an older age or weight. Further research could also focus on consistent and clear reporting of key items related to study conduct and analysis, as well as the development of a core outcome set for calf transport studies.

The effect of climatic housing and level of nutrition on the performance of calves

Five hundred and seven British Friesian × Ayrshire bull calves were reared on a once-daily milk replacer feeding system from approximately 6 to 72 days of age in four naturally ventilated, unheated calf houses differing in design and degree of insulation. Environment within the calf houses was monitored each hour. Differences in design and degree of insulation produced small but significant differences in internal house temperature, humidity and air movement which had no measurable effect on calf daily live-weight gains.

Calves receiving 0·6 kg/day compared with 0·3 or 0·4 kg/day of milk replacer plus concentrates ad libitum ate less concentrates but had higher daily live-weight gains (0·56 compared with 0·49 kg/day respectively) (P < 0·001). Rations supplying similar amounts of metabolizable energy from varying proportions of milk:concentrate resulted in comparable live-weight gains. Results suggest that calf viability was affected by level of nutrition and that low levels of milk replacer feeding resulted in higher mortality. Naturally ventilated, unheated calf houses were demonstrated to be suitable for rearing calves in south-west Scotland.

Herd-level risk factors for infectious diseases in Swedish dairy calves aged 0–90 days

The effect of environmental factors and management routines on the risk of diarrhoea, respiratory disease and other infectious diseases was investigated in 3081 heifer calves 0-90 days old in 122 Swedish dairy herds. The farmers kept records on cases of diseases in their heifer calves and in addition, project veterinarians clinically examined all calves every 2-3 months. At each visit, the veterinarians also measured the ammonia concentration and relative air humidity in the housing facilities for the calves. The cleanliness of the animals and their environment was recorded as a measure of the hygienic status of the farm. The presence or absence of draught (i.e. wind velocity>0.5 m/s) was recorded twice during the study period. The effect of these factors, as well as the placing of the calf pens, the nature of the pen walls, air volume per animal, management factors (such as the status of the caretaker and feeding routines) and presence or absence of a bovine viral diarrhoea virus (BVDV) infection in the herd, was evaluated by means of a two-level variance component logistic model. The placing of calf pens along an outer wall was significantly associated with the risk of diarrhoea (odds ratio (OR): 1.92, P<0.01). The risk for respiratory disease was significantly associated with an ammonia concentration below 6 ppm (OR: 0.42, P<0.05) while the odds ratio for moderately to severely increased respiratory sounds was significantly associated with a BVDV infection in the herd (OR: 2.39, P<0.05) and draught (OR: 3.7, P<0.02). Absence of draught was significantly associated with the risk for infectious diseases other than diarrhoea and respiratory disease (OR: 0.42, P<0.01).

Immune functions of veal calves fed low amounts of iron

Immune functions were studied in male calves fed milk replacer (MR) containing 10 or 50 mg iron (Fe)/kg. Calves fed 10 mg Fe/kg MR developed marked hypoferremia and anemia, whereas serum-Fe and haemoglobin concentration of calves fed 50 mg Fe/kg MR were normal. Growth performance was reduced, while feed/gain ratio, incidence of infections (especially pneumonias), febrile body temperatures and antibiotic treatments were higher in calves fed 10 than 50 mg Fe/kg MR (p < 0.05). Whereas antibody production (to horse erythrocytes) and lymphocyte stimulation (by mitogens) were not significantly altered, cell-mediated immunity (measured as cutaneous delayed-type hypersensitivity reaction to dinitrofluoro-benzene), number of neutrophils with phagocytic capacity, activity of the Fe-containing enzyme myeloperoxidase, blood serum IgG concentration and the number and diameter of germinal centres as a measure of the number and production of B-cells in cervical superficial lymph nodes in calves fed 10 mg Fe/kg MR were reduced when compared with calves fed 50 mg Fe/kg MR (p < 0.05). In conclusion, severe Fe deficiency caused reduced growth performance, associated with and partly due to higher incidence of infections because of defective immune reactions.

Two housing systems for calves

Thirty-six male Holstein calves were in an experiment with 2 X 2 factorial design with the objective of comparing management systems and milk feeding. Housing systems were similar except calves on A system were housed in pens .66 m wide with grated floors whereas calves on B system were in pens that were 1.36 m wide with solid floors bedded with straw. Within each management system nine calves were fed milk at 8% of body weight and nine calves at 12% of body weight. There was no interaction between management system and feeding percent. Preweaning calves fed more milk gained faster (.64 versus .50 kg/day) compared with calves fed less. Management system did not influence body weight gain or feed conversion prior to weaning, but postweaning A system resulted in slower gains (.74 versus .90 kg/day) and less favorable feed conversion (2.00 versus 1.77 kg dry matter intake/kg body weight gain) than calves housed under the B system. Eosinophil count was higher during 5th and 7th wk of the experiment for calves housed in A compared with B system. Measurements of body weight gain and feed conversion were effective in differentiating between two housing systems for calves.

[Reference values of hemoglobin content, hematocrit and mean concentration of corpuscular hemoglobin of calves reared without iron supplementation. 3. Comparison of the observed age dependency with literature values]

The average hemoglobin (Hb) and hematocrit (Hc) values determined in our own investigations with 491 rearing calves in the first five months of their lives were compared with the nationally and internationally published data of the dependence of these hematologic values on the age or rearing resp. milk fattening calves. The main influencing factors on the ageing development were the initial level of Hb and Hc, the length of the milk feeding period, the time of the beginning of feed supplementing, the development of dry matter consumption resp. the supply with milk, the iron content of the milk exchanger and the live weight increase achieved under the respective nutritional conditions. This dependence on the development proves that anaemia occurring with rearing calves in the first few weeks of their lives is mainly caused by iron deficiency. From the similarity of the average Hb resp. Hc values one can derive the conclusion that the considerable anaemia frequencies observed in one's investigations are not a phenomenon specific of one farm or of time but represent a general problem of the rearing of calves without iron substitution.

Symposium: disease prevention in calves. Factors affecting susceptibility of calves to disease

Enteric and respiratory disorders are the main hazards to successful calf rearing. The many interrelated factors in the etiology of these disorders are reviewed, and an attempt has been to classify the factors into those of a microbiological, immunological, nutritional, genetic, physical, or psychological nature. No one would dispute that enteric and respiratory disorders are the two main hazards to calf health, but many would argue about the relative importance of specific pathogens and other predisposing factors in the etiology of these disorders.

[Investigations of anemia of male rearing calves. 1. Reference conditions and anemia frequency]

In a longitudinal investigation (3 points of time n = 214, 206 resp. 202) the hemoglobin quota (Hb), the hematocrit (Hct) resp. the average corpuscular hemoglobin concentration (MCHC) were analysed at male calves receiving semi-liquid feed in the transitional period from pre-ruminal to ruminal digestion (56d). Breed, live weight development, consumption of milk, concentrated feed resp. dried forage, diseases of the calves as well as the father and the milk yield resp. the lactation age of the mother were registered as reference conditions. The percentage of calves with an Hb less than 10.5 g/dl was at the three points of time 50.00%, 86.41% resp. 41.58%, of calves with an Hct less than 33,5% it was 43.46%, 66.02% resp. 31.68% and of calves with an MCHC less than 30.5 g Hg/dl erythrocytes 51.87%, 76,21 resp. 47,03%. 21.50%, 33.50% resp. 4.46% of all test animals even had an Hb of less than 8.5 g/dl.