Performance of Hereford and two-breed rotational crosses of Hereford with Angus and Simmental cattle: I. Calf production through weaning

Cow size, reproductive traits and calf performance through weaning were evaluated in a range environment for Simmental (S) x Hereford (H) and Angus (A) x H crosses in two-breed rotations and straightbred H. Data were grouped into seven dam breed categories: straightbred Hereford (H), crossbred F1 S x H cows (SH), S x H cows of low percentage H (SHS), S x H cows of high percentage H (HSH), F1 A x H cows (AH), A x H cows of low percentage H (AHA) and A x H cows of high percentage H (HAH). Straightbred H, SH, AH, SHS and AHA cows were mated to H bulls, HSH cows were mated to S bulls and HAH cows were mated to A bulls. Cows in the SHS and AHA groups ranged from 1/4 to 3/8 H and their calves from 5/8 to 11/16 H. Cows within the HSH and HAH groups ranged from 5/8 to 3/4 H and their calves from 5/16 to 3/8 H. Cow age ranged from 3 to 10 yr. Simmental-cross cows were heavier and taller and produced heavier calves at birth and weaning than A-cross. Pregnancy rate, calf birth date and percentage of difficult births did not vary significantly among dam breed groups. Within the A x H and S x H rotations, dam breed group rankings for calf birth weight were inverse to rankings for proportion of H in the breed makeup of the calf.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of reciprocal differences in Bos indicus x Bos taurus backcross calves produced through embryo transfer: I. Birth and weaning traits

Angus (A) and Bos indicus (B; Brahman or Nellore) reciprocal backcross, embryo transfer calves, belonging to 28 full-sib families, were evaluated for differences in birth weight, gestation length, and weaning weight. Two methods were investigated; method I made no distinction between how the F(1) parents were produced, whereas method II distinguished between the 2 types of F(1) parents (AB vs. BA corresponding to A x B vs. B x A, respectively). Bos indicus backcross calves had a 4.3 d longer (P < 0.05) gestation length but did not differ in their average birth weight from A backcrosses. Among B backcrosses, B x F(1) calves had a 5.2 d longer (P = 0.01) gestation length than F(1) x B calves (290.5 vs. 285.3, respectively). Under method II analysis, there was a consistent trend for gestation length, in which BA F(1) parents produced calves that ranked greater than calves from AB F(1) parents, as sires and dams. Crosses with a greater proportion of B in the sire in relation to the amount in the dam had a heavier (P < 0.05) birth weight (F(1) x A and B x F(1); 38.1 and 38.4 kg, respectively) than their respective reciprocal crosses (A x F(1) and F(1) x B; 34.3 and 33.5 kg, respectively). The F(1) x A and B x F(1) crosses showed a large difference in birth weight between males and females (5.3 and 4.1 kg, respectively), whereas A x F(1) and F(1) x B crosses showed a small difference (P > 0.10) in birth weight between males and females (1.5 and 1.1 kg, respectively). Further examination within each sex showed a difference between male reciprocals that was generally much larger than that between female reciprocals. Calves with a greater percentage of B in the sire compared with the proportion in the dam ranked heavier for weaning weight as for birth weight, though these differences were not significant. In breeding systems involving B x Bos taurus crosses, even when using embryo transfer, not only does the breed composition of the calves affect their preweaning performance, but the particular cross that produces the calves also should be considered in making breeding decisions.     

Serum IgG and total protein concentrations in dairy calves fed two colostrum replacement products

OBJECTIVE: To evaluate effects of 2 commercially available colostrum replacement products on serum IgG and total protein concentrations in dairy calves. DESIGN: Prospective clinical trial. ANIMALS: 84 Holstein bull calves from a single dairy. PROCEDURES: Calves were randomly assigned to be given 4 quarts of colostrum (group 1; n = 21), 2 packages of a colostrum replacement product (product A; group 2; 21), 1 package of a different colostrum replacement product (product B; group 3; 21), or 2 packages of product B (group 4; 21). Treatments were given within 3 hours after birth, and blood samples were collected 24 hours later and submitted for determination of serum total protein and IgG concentrations. RESULTS: Group 1 calves had significantly higher serum total protein and IgG concentrations than did calves in the other 3 groups. However, the percentage of calves with adequate passive transfer (ie, serum IgG concentration > 1,000 mg/dL) was not significantly different among groups 1 (90%), 3 (81%), and 4 (95%). In contrast, only 10% of calves in group 2 had adequate passive transfer. It was predicted that calves fed product B that had serum total protein concentrations > 5.2 g/dL would have serum IgG concentrations > 1,000 mg/dL at least 90% of the time. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that product B could be considered as an alternative to colostrum in dairy calves, but product A failed to routinely provide adequate serum IgG concentrations when fed according to label directions.     

Ontogeny of mRNA abundance of nuclear receptors and nuclear receptor target genes in young cattle

After birth the development of appropriate detoxification mechanisms is important. Nuclear receptors (NR), such as constitutive androstane receptor (CAR), pregnane X receptor (PXR), peroxisome proliferator-activated receptor-alpha (PPARalpha), retinoid receptors (RAR, RXR), and NR target genes are involved in the detoxification of exogenous and endogenous substances. We quantified abundances of hepatic mRNA of NR and several NR target genes (cytochromes, CYP; cytochrome P450 reductase, CPR; UDP-glucuronosyl transferase, UDP) in calves at different ages. Gene expression was quantified by real-time RT-PCR. Abundance of mRNA of CAR and PXR increased from low levels at birth in pre-term calves (P0) and full-term calves (F0) to higher levels in 5-day-old calves (F5) and in 159-day-old veal calves (F159), whereas mRNA levels of PPARalpha did not exhibit significant ontogenetic changes. RARbeta mRNA levels were higher in F5 and F159 than in F0, whereas no age differences were observed for RARalpha levels. Levels of RXRalpha and RXRbeta mRNA were lower in F5 than in P0 and F0. Abundance of CYP2C8 and CYP3A4 increased from low levels in P0 and F0 to higher levels in F5 and to highest levels in F159. Abundance of CPR was transiently decreased in F0 and F5 calves. Levels of UGT1A1 mRNA increased from low levels in P0 and F0 to maximal level in F5 and F159. In conclusion, mRNA levels of NR and NR target genes exhibited ontogenetic changes that are likely of importance for handling of xeno- and endobiotics with increasing age.     

Ruminal microbial development in conventionally or early-weaned calves

Eight bull calves (four Holsteins and four Ayrshire calves with mean birth weight of 38.8 kg) were ruminally cannulated at 3 d of age and allocated to one of two weaning programs. All calves were fed colostrum for 3 d after birth and milk until weaning. Calves in the conventional-weaning program were fed a starter diet from 3 d of age and weaned at 6 wk of age. In the early-weaning program, calves were fed a highly palatable pre-starter diet from 3 d of age until they consumed 227 g/d, and then fed a mixture of pre-starter (227 g) and starter diet ad libitum. Calves in this group were weaned at 4 wk of age. Ruminal samples were collected at 3 and 7 d, then weekly thereafter through 8 wk and at 10 and 12 wk of age to assess microbial activity. Calves in the early-weaned group had a higher concentration of total ruminal volatile fatty acids at an earlier age than the calves in the conventional-weaning program. This was accompanied by a trend toward higher lactate concentrations and lower ruminal pH in the early-weaned group during their first 4 wk of age. Lactate and ammonia concentrations decreased with calf age. The total anaerobic bacterial counts increased slightly with calf age, whereas Streptococcus bovis and facultative bacterial populations decreased with calf age. Amylolytic, proteolytic, lactobacilli, lactate-utilizers, cellulolytic and methanogenic bacterial populations increased progressively in both groups. Cellulolytic and methanogenic bacteria were present in both groups at 3 d of age. No protozoa were detected in calves of either group. In general, the most significant changes in bacterial populations and metabolic activity in both groups occurred between 4 and 6 wk of age. Although calves in both groups had similar patterns of bacterial development, calves in the early-weaning program tended to have high ruminal microbial activity at an earlier age than the conventionally weaned calves.     

The effect of delays in feeding colostrum and the relationship between immunoglobulin concentration in the serum of neonatal calves and their rates of growth

SUMMARY Eighty-five unsuckled newborn calves, were fed 1.5 L of colostrum of known IgG concentration at either 2, 4, 6 or 8 hours after birth with no additional colostrum feeding. Another group of 11 calves were left with their dam for 16 hours after birth, before separation. Blood samples were taken from all calves 24 hours after colostrum feeding or separation from the dam and serum Ig concentrations were measured by electrophoresis. There were no significant differences in mean serum Ig concentrations between calves fed at the different times after birth. Three of the 11 calves left to suckle were hypogamma-globulinaemic. Other calves in this group had higher serum Ig concentrations than the means of all other groups. All groups had mean serum Ig concentrations higher than the suggested minimum concentration required for adequate calf health. There were a number of calves that did not reach the suggested minimum serum concentration after feeding, but calf mortality was low and all calves were healthy apart from a slight scour for a few weeks after birth. There was no significant relationship between serum Ig concentration 24 to 48 hours after birth and either calf mortality or average growth rate over an 8- to 10-month period.     

Colostrum management in calves: effects of drenching vs. bottle feeding

The objective was to examine whether the administration of colostrum by a drencher is a safe method to achieve satisfying immunoglobulin concentrations in newborn Holstein Friesian (HF)-calves. Twenty-one calves were fed 1 h postnatum with 2 l colostrum from their dam using a nipple bottle (group I); 15 calves were drenched with 4 l colostrum from their dam 1 h postnatum (group II). Thereafter, all calves were fed milk replacer exclusively. Serum concentration of total immunoglobulin [analysed by Sandwich-enzyme-linked immunosorbent assay (ELISA)] 24 h postnatum was higher in drenched calves (25.2 g/l; 12.8/52.2; median and 10/90 percentiles) compared with bottle-fed calves (14.1 g/l; 9.2/24.7). To characterize the kinetics of immunoglobulin absorption, 17 blood samples were taken frequently within 72 h postnatum using a jugular catheter in five calves fed 2 l colostrum by nipple bottle and five calves drenched with 4 l colostrum 1 h postnatum. A slightly delayed increase of serum immunoglobulin concentration (approximately 3 h) was obvious in drenched calves compared with bottle-fed calves, but drenched calves reached significantly higher immunoglobulin concentrations compared with bottle-fed calves. It is concluded that the proper application of colostrum by a drencher is a useful method for adequate colostral supply in newborn calves. The failure of the oesophageal groove reflex in drenched calves caused no clinical consequences.     

Effects of age on the pharmacokinetics of single dose ceftiofur sodium administered intramuscularly or intravenously to cattle

The effects of maturation on the intravenous (IV) and intramuscular (IM) pharmacokinetics of ceftiofur sodium following a dose of 2.2 mg ceftiofur equivalents/kg body weight were evaluated in 16 one-day-old Holstein bull calves (33-53 kg body weight initially; Group 1) and 14 six-month-old Holstein steers (217-276 kg body weight initially; Group 2). Group 1 calves were fed unmedicated milk replacer until 30 days of age and were then converted to the same roughage/concentrate diet as Group 2. Groups 1-IV and 2-IV received ceftiofur sodium IV, and Groups 1-IM and 2-IM received ceftiofur sodium IM. Group 1 calves were dosed at 7 days of age and at 1 and 3 months of age; group 2 calves were dosed at 6 and 9 months of age. Blood samples were obtained serially from each calf, and plasma samples were analysed using an HPLC assay that converts ceftiofur and all desfuroylceftiofur metabolites to desfuroylceftiofur acetamide. C_max values were similar in all calves, and were no higher in younger calves than in older calves. Plasma concentrations remained above 0.150 μg ceftiofur free acid equivalents/mL for 72 h in 7-day-old calves, but were less than 0.150 μg/mL within 48 h following IV or IM injection for 6- and 9-month-old calves. Intramuscular bioavailability, assessed by comparing the model-derived area under the curve (AUC_mod) from IM and IV injection at each age, appeared to be complete. After IV administration, the AUC_mod in 7-day-old and 1-month-old calves (126.92±21.1 μg-h/mL and 135.0±21.6 μg.h/mL, respectively) was significantly larger than in 3-, 6- and 9-month-old calves (74.0±10.7 μg.h/mL, 61.0±17.7 μg.h/mL and 68.5±12.8 μg.h/mL, respectively; P< 0.0001). The V_d(ss) decreased linearly within the first 3 months of life in cattle (0.345±0.0616 L/kg, 0.335±0.919 L/kg and 0.284±0.0490 L/kg, respectively; P= 0.031), indicative of the decreasing extracellular fluid volume in maturing cattle. The Cl_b was significantly smaller in 7-day-old and 1-month-old calves (0.0178±0.00325 L/h.kg and 0.0167±0.00310 L/h.kg, respectively) than in 3-, 6- and 9-month-old calves (0.0303±0.0046 L/h.kg, 0.0398±0.0149 L/h.kg and 0.0330±0.00552 L/h.kg, respectively; P≦0.001). This observation may be indicative of maturation of the metabolism and/or excretion processes for ceftiofur and desfuroylceftiofur metabolites. The approved dosage regimens for ceftiofur sodium of 1.1-2.2 mg/kg administered once daily for up to 5 consecutive days will provide plasma concentrations above the MIC for bovine respiratory disease pathogens for a longer period of time in neonatal calves than in older calves. Peak plasma concentrations of ceftiofur and desfuroylceftiofur metabolites were no higher in neonatal calves than in more mature cattle, highly suggestive that peak tissue concentrations would be no higher in neonatal calves than in more mature cattle.     

Effect of tropically adapted sire breeds on preweaning growth of F1 Angus calves and reproductive performance of their Angus dams

The objective of this study was to determine the effect of tropically adapted sire breeds on preweaning growth performance of F1 calves and on reproductive performance of their Angus dams. Angus (A) cows were bred in two consecutive years (1992 and 1993) by AI using semen from Brahman (B; Bos indicus; n = 10), Senepol (S; Bos taurus; n = 10), and Tuli (T; Sanga; n = 9) bulls. A total of 82 B x A, 85 S x A, and 91 T x A calves were born. The statistical model included the fixed effects of year, sire breed, calf sex, sire breed x calf sex, and cow parity and the random effect of sire within sire breed. Birth weight, weaning weight, 205-d adjusted weaning weight, ADG from birth to weaning, and hip height at weaning were greater (P < .001) for B x A calves than for S x A or T x A calves. Greater differences were detected between sexes for B x A than for S x A and T x A (for all traits sire breed x calf sex, P < .05). Sire breed affected (P < .01) the percentage of unassisted calvings (B x A, 87%; S x A, 98%; and T x A, 100%) and tended (P < .10) to affect the percentage of calves that survived until weaning (B x A, 90%; S x A, 94%; and T x A, 98%). Sire breed of calf did not affect (P > .10) length of gestation, and sire breed did not affect the interval from calving to first observed estrus or pregnancy in Angus dams. These results demonstrate that preweaning growth performance of B x A calves was greater than that of either S x A or T x A calves. However, use of Brahman sires on Angus dams led to calving problems and tended to reduce the percentage of calves that survived until weaning. Thus, heavier weaning weights of B x A calves would be an advantage for cow-calf producers marketing calves, but heavier birth weights and calving difficulty attributed to Brahman sires would be a disadvantage.     

Morphometric and ultrastructural study of postnatal lung growth and development in calves

The objectives of this study were to characterize basic patterns of postnatal lung growth in 1- to 150-day-old Holstein calves and to identify periods of accelerated lung growth and times of epithelial cell development that might correlate with periods of heightened susceptibility to pulmonary injury by infective agents and dietary toxins. Calves had fully developed alveoli at birth. There was an age-associated increase in total alveolar surface area and alveolar number, which was most marked in calves older than 30 days. Lung volume and body weight increases were also most marked when calves were older than 30 days. Mean bronchiolar cross-sectional area increased significantly (P less than 0.05) with age, and there was a significant (P less than 0.05) decrease in the percentage of terminal bronchioles with diameters less than 3 x 10(4) microns between 1 and 150 days. In newborn calves, nonciliated bronchiolar epithelial cells retained fetal characteristics of differentiation, including abundant cytoplasmic glycogen and sparse agranular endoplasmic reticulum. Glycogen deposits were depleted, and agranular endoplasmic reticulum was developed in nonciliated cells by the time calves were 30 days old. We concluded that bronchiolar epithelium in calves is well differentiated by the time they are 30 days old and that lung growth in calves raised in semi-isolation begins most rapidly when calves are approximately 30 days old.     

The influence of colostral antibodies on the postvaccinale humorale immune response in neonatal calves

The aim of this study was to evaluate the efficiency of vaccination of young calves and to see whether maternal antibodies may influence the immunological response in calves. For this project 20 matched-pairs of cows and their offspring were selected. Of each pair, one cow received a placebo 8 and 4 weeks before term (group A) and the other was vaccinated against Feline Leucose Virus, FeLV, with Leucogen? (group B). All calves received colostrum from their respective mother shortly after birth and all calves were vaccinated with Leucogen? 10 days after birth. Blood samples from the cows and calves were taken during the whole study period (till four weeks after calf vaccination). An ELISA test was done in the lab to define the FeLV antibody concentration. 30 % of the vaccinated cows showed a seroconversion, 13 out of 20 vaccinated cows passed the antibodies onto their calves. 11 calves of group B did not convert in comparation of only 4 of group A. All seroconverted calves had low antibody concentration before their vaccination. Calves of group B with a low passive antibody level at the beginning showed a higher seroconversion as compared to calves with higher antibody concentrations of the same group. Two thirds of the calves without maternal antibodies reacted adequately to the vaccination. Therefore, an early vaccination of calves can be recommended.     

Influence of orally administered bovine lactoferrin on lipid metabolism in lipopolysaccharide-injected preruminant calves

The aim of this study was to investigate the influence of oral lactoferrin (LF) administration on lipid metabolism changes in calves given lipopolysaccharide (LPS). Twenty-one 4-day-old Holstein calves were divided into three groups, with each group receiving one of three oral doses of LF (0, 1, 3 g/day) for 10 consecutive days (day −10 to day −1). All calves were intravenously injected with LPS (50 ng/kg BW) on day 0, the day after LF treatment ended. Plasma triglyceride concentrations were lower ( P  < 0.05) in the LF-treated calves than in the control calves given 0 g/day of LF at 12 and 24 h after LPS injection. Plasma NEFA concentrations were elevated between 6 and 24 h after LPS treatment. At 12 h, the concentration of plasma NEFA was lower ( P  < 0.05) in the calves given LF 3 g/day than in the control calves. On day 0, plasma total cholesterol and phospholipid concentrations tended to be lower in the LF groups administered 1 and 3 g of LF/day than in the control group, but did not differ significantly among the groups. The plasma very-low-density and low-density lipoprotein concentrations were lower ( P  < 0.05) at 12, 24, and 72 h in the LF groups than in the control calves. The concentrations of plasma high-density lipoprotein tended to be lower in the LF groups than in the control group between day 0 and 96 h, though there were no significant group differences. The concentration of plasma interleukin-1β was lower ( P  < 0.05) in the calves fed LF 3 g/day than in the control calves at 2 and 12–48 h after LPS injection. These data suggest that LF inhibits LPS-induced alterations in lipid metabolism in preruminant calves.     

Pharmacokinetics of sulfadiazine/trimethoprim in neonatal male calves: effect of age and penetration into cerebrospinal fluid

Sulfadiazine (SDZ)/trimethoprim (TMP; 30 mg of SDZ/TMP/kg of body weight) was given IV to the same 6 male calves at 1, 7, and 42 days of age and to 2 additional calves at 7 days of age. Serum concentrations of SDZ and TMP were best represented by a 2-compartment open model, but in 42-day-old calves, CSF concentrations of both drugs were best represented by a 1-compartment open model with first-order input. Between 1 and 42 days of age, the elimination half-life (t1/2(beta)) of SDZ decreased from 5.7 to 3.6 hours, and total body clearance (CLtot) increased from 1.43 to 1.88 ml/min/kg; the area under the curve (AUC0----infinity) decreased from 291.5 to 225.4 mg/L.h. The distribution coefficient (Vd(area)/kg of body weight) decreased with age, changing from 0.72 to 0.59 L/kg, between 1 and 42 days of age. Therapeutic concentrations of SDZ in serum (greater than 2 micrograms/ml) were maintained for 24 hours in 1-day-old calves and for about 15 hours in 7- and 42-day-old calves. The elimination rate of TMP increased about 9-fold; t1/2(beta) was 8.4, 2.1, and 0.9 hours, respectively, at 1, 7, and 42 days of age. Other values also reflected an increase in TMP elimination rate with age: CLtot increased from 2.8 to 12 to 28.9 ml/min/kg, k13 increased from 0.336 to 0.654 to 1.664/h and AUC0----infinity decreased from 32.8 to 7.9 to 3.1 mg/L.h, respectively. Therapeutic concentrations (greater than 0.1 microgram/ml) were maintained for 15 hours, 8 hours, and about 6 hours in 1-, 7-, and 42-day-old calves, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Blood pH, plasma carotene, vitamin A, albumin and globulin concentrations in newborn calves and in dams during the first three days of the postnatal period.

Blood pH, total plasma carotene, plasma vitamin A fractions and some plasma proteins were determined in newborn calves (n = 38) and their dams. Calves were assigned to one of two groups according to their blood pH immediately after birth: group 1 (normal) with pH above 7.2 (n = 27) and group 2 (slightly acidotic) with pH 7.0 to 7.2 (n = 11). The difference between the neonatal blood pH values of the two groups immediately post partum disappeared 24 h after birth. The blood pH of the dams was normal. The extremely low plasma carotene concentration (group 1: 32.7 micrograms/l; group 2:20.5 micrograms/l) and the low plasma globulin fractions (group 1:19.6 g/l; group 2:19.2 g/l) immediately after birth were elevated by the intake of colostrum. There was no significant change in plasma vitamin A fractions (retinol, retinyl ester) during the early postnatal period (3 days post partum) in newborn calves. The acid-base balance of newborn calves does not have any influence on the physiological alterations of plasma vitamin A, carotene and some plasma proteins during the first three days of life.     

The physiological and physical status of single calves at birth in a dairy herd in New Zealand

AIM: To determine the physiological status of calves at birth and the perinatal factors that might predispose newborn calves to debility and death, using criteria previously established for newborn lambs. METHODS: Friesian mixed-aged cows and heifers on a dairy farm in New Zealand that were close to calving were separated from the main herd and observed 24 h a day until they calved. Cows in which labour did not progress for over 1 h or which were in distress were assisted. About 12-13 min after birth, rectal temperature was measured and a blood sample was taken from each calf. The packed cell volume (PCV) and plasma lactate, glucose and fructose concentrations were determined. The time to stand for each calf and the air temperature and weather conditions at birth were recorded. RESULTS: The parameters measured were within normal ranges for newborns for the majority of calves. Calves sired by an Angus bull and born to heifers (AngusX) had significantly higher plasma lactate and fructose concentrations than Friesian calves born to cows, but there were no significant differences between the two breeds in any of the other parameters measured. Calves of both breeds born with assistance had significantly higher plasma lactate concentrations than those born without. Friesian calves that were assisted at birth had significantly lower PCVs and took significantly longer to stand than calves born without assistance. Assisted AngusX calves were significantly heavier than their unassisted counterparts. Calves born during windy and wet weather and when air temperatures were below 10 degrees C had lower rectal temperatures, took longer to stand and had higher plasma glucose concentrations than those born in dry weather and when air temperatures were above 10 degrees C. CONCLUSIONS: Calves with physiological parameters outside the normal range had experienced difficult labour and/or intrapartum hypoxaemia. Placental insufficiency and maternal undernutrition during late pregnancy did not apparently contribute to neonatal problems in the present study.     

Gammaglobulin and selenium status in healthy neonatal dairy calves in Switzerland

Serum samples from 142 calves and their dams were analyzed for gammaglobulins (gammaG, calves) and selenium concentrations (Se, calves and dams). A questionnaire provided information about birth and colostrum management. The calves and their dams were distributed into two groups according the calves' gammaG concentration (< 10 and >= 10 g/L), Se concentrations were compared between groups. The correlation between gammaG and Se concentrations in the calves and their dams was analyzed. Risk factors for failure of passive transfer and Se deficiency were assessed based on the questionnaire. The gammaG concentration of 42.9 % of the calves was < 10 g/L (median: 10.9). Calves showed significantly higher gammaG values after optimized colostrum administration than calves with suboptimal colostrum administration (p < 0.004). The median Se concentration was 26.8 and 36.5 μg/L for the calves and dams, respectively. A high correlation was observed between the Se concentration of the dam and her calf (r = 0.72, p < 0.001). The calves' Se and gammaG concentrations were not significantly correlated. These results demonstrate that further efforts toward better information of farmers regarding colostrum management and Se supply are warranted.     

Prevalence of Cryptosporidium parvum infection and pattern of oocyst shedding in calves in Japan

Cryptosporidium parvum infection and the pattern of oocyst shedding were observed in calves. A total of 480 fecal samples were collected from 30 calves (age, < or =30 days) over a period of 10 months from June 1998 to March 1999. A sucrose centrifugal flotation technique revealed 28/30 (93%) calves were passing Cryptosporidium oocysts. Oocyst shedding was first detected on the sixth day after birth, with 8% of the calves testing positive. This rate increased day by day and reached approximately 80% by day 15. Oocyst shedding varied from 1 to 13 days, with a mean of 7 days. Calves infected with C. parvum had a significantly higher rate of diarrhea (33%) than non-infected calves (8%) (P<0.05), suggesting C. parvum infection as the likely cause. The mean number of oocysts excreted by calves < or =30 days old was approximately 6x10(7) per gram of feces. These results indicated that one calf would excrete some 6x10(11) oocysts in the first month after birth, taking both the quantity of feces in a day and the period of excretion into consideration. Accordingly, it is clear that calves are important in the spread of cryptosporidiosis to calves and humans.     

Effects of zeranol on reproduction in beef bulls: luteinizing hormone, follicle-stimulating hormone, and testosterone secretion in response to gonadotropin-releasing hormone and human chorionic gonadotropin

Effects of zeranol on the maturation of the adenohypophyseal-gonadal axis were studied in beef bulls. Calves were implanted with 36 mg of zeranol at 3-month intervals from birth through 6 months of age (group 2, n = 10) or were not treated (control group 1, n = 10). After 9 months, group-2 calves were given implants of 36 mg of zeranol at 3-month intervals through 18 months of age (group 2B, n = 5) or were not reimplanted (group 2A, n = 5). Areas under the curves outlined by concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone for 6 hours after the administration of 100 micrograms of gonadotropin-releasing hormone (GnRH) were calculated. Gonadotropin-releasing hormone was administered at 3-month intervals from 1.5 through 19.5 months of age. Areas under the curves for concentrations of testosterone for 4 hours after the administration of 10,000 IU of human chorionic gonadotropin (HCG) at 4.5, 7.5, and 10.5 months or 1,000 IU at 13.5 and 16.5 months of age also were calculated. The amount of FSH released was greater (P less than 0.05) for group-2 than for group-1 calves at 4.5 and 7.5 months of age. The amount of FSH released in groups 2A and 2B tended (P less than 0.10) to be greater than that for group 1. Significant differences between groups 2A and 2B were not observed. The amount of LH released at 7.5 months of age was less for groups 1 and 2 than that at earlier ages, and the decrease was greater (P less than 0.05) for group 2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Urinary GGT/creatinine ratio and fractional excretion of electrolytes in diarrhoeic calves

The aim of this study was to monitor renal function in diarrhoeic calves and to determine the effectiveness of an applied fluid therapy. A total of 28 diarrhoeic (n = 18) and healthy (n = 10) Holstein-Friesian calves of different sexes, between 1 and 30 days of age, were used. Blood and urine samples were obtained from diarrhoeic calves before the treatment and then three more times at 24-h intervals during the treatment. From healthy calves, samples were taken only once. Therapy was started by the intravenous administration of 8.4% sodium bicarbonate and 0.9% sodium chloride solutions for the first 24 h, followed by the oral application of a commercial electrolyte solution (sodium chloride 3.5 g, trisodium citrate 2.9 g, potassium chloride 1.5 g and glucose anhydrous 20 g in 1 litre H2O) up to the 48th h of therapy. Before the therapy, the average levels of pH (7.10 +/- 0.12), bicarbonate (HCO3-) (16.48 +/- 3.80 mmol/l), base deficit (-12.65 +/- 5.97 mmo/l) and fractional excretion (FE) of sodium (0.16 +/- 0.11%) and potassium (15.07 +/- 8.56%) were significantly lower while serum urea (17.48 +/- 10.32 mmol/l) and creatinine (Cr) concentrations (169.72 +/- 98.12 micromol/l), haematocrit levels (45.13 +/- 13.60%) and urinary gamma glutamyl transferase (GGT)/Cr ratio (8.6 +/- 4.3 x 1/10(3) U/micromol) were significantly higher in diarrhoeic calves than in healthy calves. Alterations in parameters indicating the presence of renal dysfunction were normalised in the diarrhoeic calves that survived (83.3%). Three calves with severe metabolic acidosis and azotaemia died at the beginning of therapy. It was concluded that the FE of Na and K (FENa, FEK) and urine GGT/Cr ratio may have an important role in assessing renal function in diarrhoeic calves and in evaluating the effectiveness of an applied fluid therapy.     

Effects of prepartum supplementary fat and muscle hypertrophy genotype on cold tolerance in newborn calves.

Effects of feeding pregnant dams supplemental dietary fat during the last 55 d of gestation on cold tolerance of newborn crossbred calves with (Piedmontese cross, P, n = 15) or without (Hereford cross, H, n = 16) the muscle hypertrophy allele was determined. Primiparous F1 dams gestating F2 calves of the respective breeds were assigned randomly within breed to receive gestation diets containing either 2.2 (Low Fat; LF) or 5.1% fat (High Fat; HF). Safflower (Carthamus tinctorius L.) seeds containing 37% oil with 79% linoleic acid were the supplemental fat source in diets formulated to be isocaloric-isonitrogenous. At parturition, calves were separated from their dams, fed 38 degrees C pooled dairy cow colostrum (30 mL/kg BW), muzzled to prevent suckling, and returned to their dams in a heated (22 degrees C) room for 3.5 h. At 4 h of age (birth = 0 h), a catheter was inserted into the jugular vein. At 5 h of age, calves were placed in a 0 degrees C room for 140 min, and rectal temperatures and blood samples were obtained at 10- and 20-min intervals. Blood was assayed for cortisol and glucose. Rectal temperature was affected by diet (P<.05), time, diet x time, and breed x time (P<.01 for time and the interactions). Cortisol and glucose concentrations were not affected by diet, breed, or the diet x breed interaction, but they were affected by time, breed x time (both P<.01), and diet x time (P = .06). Calves from HF dams had higher rectal temperatures than calves from LF dams, and the HF calves maintained higher rectal temperatures throughout cold exposure. Cortisol concentrations were lower (P = .06) in calves from HF dams, and these calves had more (P = .06) glucose available for metabolic heat production than calves from LF dams. Piedmontese-cross calves maintained higher (P<.01) rectal temperatures and had higher cortisol and glucose (both P<.01) concentrations than did H-cross calves. We conclude that feeding dams supplemental fat during late gestation increased heat production in newborn calves and potentially could increase calf survival; calves with muscle hypertrophy may have a different ratio of shivering vs nonshivering thermogenesis due to differences in body composition or relationships among uncoupling proteins.