Age and season related dynamics of vitamin E levels in the serum of young cattle from birth to the age of 22 months]

The dynamics of serum vitamin E levels in heifers was followed for 22 months. We found that calves were born with a very low, almost nil, content of this vitamin (on an average 0.029 mg%) as a result of the limited diaplacental transfer from the mother to the fetus. In the following period of extrauterine life and growing up of the young cattle conspicuous age dynamics was recorded which is, however, linked or affected by the seasons. Colostral nutrition which is reflected in the increasing serum concentration of vitamin E has an important role. After the change from winter feeding rations to summer feed, consisting mainly of grazing, a marked increase in the serum concentration of vitamin E with an apex was observed, i.e. with the maximum mean value in November. In relation to the age of animals the highest concentration of vitamin E in the blood serum of heifers was recorded, expressed as mean values toward the end of our observations (0.736 mg%), i.e. in the period of sexual maturity; it equalled the concentration of vitamin E determined in cows.     

Performance of beef cows receiving cull beans, sunflower meal, and canola meal as protein supplements while grazing native winter range in Eastern Colorado

A 2-yr grazing performance study was conducted in Eastern Colorado to evaluate the effects of feeding raw cull beans (Phaseolus vulgaris) or canola meal, compared to sunflower meal, to beef cows grazing dormant, native winter range on body weight and body condition score (BCS) change, reproductive performance, and calf performance. Ninety-five pregnant, spring-calving crossbred cows (541 +/- 51 kg) in 1995 to 1996 and 65 cows (602 +/- 60 kg) in 1996 to 1997 were randomly assigned to one of five treatments (19 and 13 cows per treatment in 1995 to 1996 and 1996 to 1997, respectively): 1) unprocessed Great Northern beans to supply 182 g/d of CP (GNB); 2) canola meal to supply 182 g/d of CP (CM); 3) a mixture of Great Northern beans and sunflower meal, each to supply 91 g/d of CP, for a total of 182 g/d of CP (MIX); 4) sunflower meal to supply 182 g/d of CP (SFM+); and 5) sunflower meal to supply 91 g/d of CP (SFM-). Cow weight and body condition performance were broken into a gestation and a lactation phase in 1995 to 1996; calves were weighed at birth, at the end of the lactation phase in April, and at weaning the following September. Only gestation performance was monitored in 1996 to 1997, and subsequent calf birth and weaning weight were recorded. The SFM- group lost more weight during the gestation phase than other treatments (P < .05), yet no differences were detected for gestation phase daily BCS change, calf birth weight, lactation phase daily weight change, lactation phase daily BCS change, first-service conception rate to AI, or overall pregnancy rate. Off-test calf weight was higher in April for calves from dams of the SFM+ and CM treatments than for calves from dams on the GNB or SFM- treatments (P < .05), and calves from cows on the CM treatment were heavier in April than calves from cows on the MIX treatment (P < .05). No differences in calf weight were present at weaning. Consumption of beans by cows on the GNB treatment was low because of palatability problems. Mixing the beans with sunflower meal in the MIX treatment eliminated this problem. Canola meal, Great Northern beans, or a combination of sunflower meal and Great Northern beans were comparable to sunflower meal as protein supplements for beef cows grazing native winter range, despite obvious palatability problems with the beans.     

Reaction of foster cows to prevention of suckling from and separation from four calves simultaneously or in two steps

The aim of this study was to investigate if a 2-step method of preventing suckling and cow-calf separation reduces the stress reaction in foster cows compared with a simultaneous separation method. Seven Swedish Holstein and 5 Swedish Red dairy cows were used as foster cows, each having a group of 4 calves. The foster cow-calf group was formed when calves were 1 wk old, and the calves were prevented from suckling at 10 wk of age. In 6 of the cow-calf groups, calves were prevented from suckling by simultaneous separation from the cow (control). In the other 6 groups, calves were fitted with a nose-flap, which prevented them from suckling while they were kept together with the cow for another 2 wk before they were separated (2-step). The behavior of the foster cows was observed at 4 observation periods, 0 to 2, 8.5 to 9.5, 24 to 26, and 72 to 74 h after the calves were prevented from suckling (2-step), after separation (2-step), and after calves were prevented from suckling by simultaneous separation (control). For both treatments, saliva cortisol was sampled once daily for 5 d at wk 10. This was repeated at wk 12 for the 2-step treatment. Heart rate was measured with the behavioral observations. Control foster cows vocalized more (P < 0.001) and walked more (P = 0.005) than the 2-step foster cows after prevention of suckling and after separation from the calves. When control cows were separated from their calves, they more frequently (P < 0.001) held their head out of the pen than was the case with 2-step cows when separated 2 wk after prevention of suckling. The variation in heart rate was larger in the control group compared with 2-step cows at 0 to 2 h after separation/prevention of suckling (P = 0.002). No effect of treatment was found on cortisol concentration. Our conclusion is that separating the 2 events "prevention of suckling" and "separation" reduces the stress experienced by the foster cow at weaning.     

The effects of genotype and selected environmental factors on colostrum production and intake in cattle

The aim of this study was to determine effects of genotype and selected environmental factors on colostrum production, intake, and efficiency in the cattle. The investigations were conducted on 67 dam-calf pairs. All cows were of Polish Holstein-Friesian breed, the Black-and-White variety (PHF-HO), whereas calves were sired by bulls of the following breeds: PHF-HO, Polish Holstein-Friesian of the Red-and-White variety (PHF-RW), Jersey (JE), Montbéliarde (MB) and Limousine (LI). The colostrum was collected from cows and offered to calves "from bucket" thrice a day. The amount of produced colostrum considerably exceeded the ability of its consumption by calves. Low share of HF genes in the cow, older cow's age and calving in the period from January to April appeared to be favorable factors for colostrum production. Calves born to cows with low HF gene share drank more colostrum than calves originating from cows with higher gene share of this breed. Crosses with JE drank the highest amount of the colostrum in relation to body weight, while MB-sired calves drank the highest amount in absolute terms. Colostrum intake was positively correlated with the dam's age. Furthermore, it was shown that in case of the first colostrum intake the most favorable period was from May to September, while in cases of total intake in the first day of life and mean intake in the first 5 days of life it was the period from January to April. Crosses with JE were characterized by extremely high use of colostrum per unit of body weight gain.     

Effects of breeding season length and calving season on range beef cow productivity

A 5-yr study was conducted beginning in 1983 with 460 cows to evaluate the effects of three breeding seasons (30, 45, and 70 d in length) and two times of spring calving, March (early) and April (late), on cattle production under Nebraska Sandhills range conditions. Criteria evaluated included pregnancy and weaning percentages, calving date and distribution, cow weights and body condition at four intervals, calf birth and weaning weights, and cow productivity. The 30-d breeding season included a 10-d estrus synchronization and AI period; in the other breeding seasons only natural breeding was used. The same sires were used over the entire study period. Percentage of cows pregnant and percentage of calves weaned were lower (P less than .01) for cows bred for 30 d than for cows bred for 45 or 70 d. Average calving dates were similar among the breeding groups within the early and late calving herds. Pregnancy rates from AI were higher (P less than .01) for the cows calving in April (64%) than for the cows calving in March (41%). Cows calving in April lost less weight between precalving and prebreeding and were heavier (P less than .05) at prebreeding time than the cows calving in March. Calf weaning weights were not different (P greater than .10) among any of the breeding season groups or between the two calving herds when calves were weaned at a similar age. Cow productivity (calf weaning weight per breeding female) was highest (P less than .05) for the cows bred for 70 d (186 kg), intermediate for the cows bred for 45 d (172 kg), and lowest for cows bred for 30 d (162 kg).(ABSTRACT TRUNCATED AT 250 WORDS)     

Seroepidemiology of neosporosis in dairy cattle in Uruguay

A seroepidemiological survey of Neospora caninum was done in a dairy farm in Uruguay employing indirect fluorescent antibody test (IFAT). Sera from 217 cattle (155 cows, 31 heifers and 31 calves) were tested for N. caninum antibodies in July 2000 and it was found that abortions were significantly associated with the seropositivity of the cows by chi(2)-test (P = 0.025). The cows with an IFAT titre of 1:3200 were at a significantly higher risk of abortion than seronegative cows (P = 0.0013). Neospora organisms were detected in the brains of two aborted foetuses by immunohistochemical examination. The infection of N. caninum was considered postnatal because of the even distribution of seropositive cows (60%), low seroprevalence (20%) in calves and no significant correlation in the serostatus between calves and their dams (P = 0.43). A fitted binomial generalised linear model revealed that there was an increasing risk of abortion with increasing IFAT titre and increasing age between 2 and 6 years.     

Coccidia in cows and calves on pasture in north Georgia (U.S.A.)

The prevalence and abundance of coccidian oocysts were determined in a herd of beef cows and calves on fescue pastures in the Piedmont area of Georgia during 4-consecutive grazing seasons. Twelve species of Eimeria were found in the feces of the calves and 10 species were found in the feces of the cows. Eimeria bovis was the most prevalent species found in both the calves and cows. It occurred in 72.5% of 1090 samples from the calves and 10.2% of 719 samples from cows. Eimeria bovis also comprised the majority of oocysts present in the fecal samples from the calves and cows. The greatest number of E. bovis in a sample was 45 800 oocysts per gram of feces (OPG) from a calf and 1900 OPG from a cow. No cases of clinical coccidiosis were seen in any of the animals sampled during the survey.     

Postpartum supplemental fat, but not maternal body condition score at parturition, affects plasma and adipose tissue fatty acid profiles of suckling beef calves

Three-year-old Angus x Gelbvieh beef cows, which were nutritionally managed to achieve a BCS of 4 +/- 0.07 (479 +/- 36 kg of BW) or 6 +/- 0.07 (580 +/- 53 kg of BW) at parturition, were used in a 2-yr experiment (n = 36/yr) to determine the effects of maternal BCS at parturition and postpartum lipid supplementation on fatty acid profile of suckling calf plasma and adipose tissue. Beginning 3 d postpartum, cows within each BCS were assigned randomly to 1 of 3 treatments in which cows were all fed hay and either a low-fat (control) supplement or supplements with either high-linoleate cracked safflower seeds (linoleate) or high-oleate cracked safflower seeds (oleate) until d 61 of lactation. Diets were formulated to be isonitrogenous and isocaloric, and safflower seed supplements were provided to achieve 5% of DMI as fat. Total concentration of fatty acids in plasma did not differ (P = 0.48) due to maternal BCS at parturition. Percentage of 20:5n-3 in plasma tended (P = 0.06) to be greater for calves suckling cows with a BCS of 6 at parturition. No other differences (P = 0.12 to 0.99) were noted in calf plasma fatty acid profile due to maternal BCS at parturition. Likewise, no differences were detected for total fatty acid concentration (P = 0.88) in calf adipose tissue due to maternal BCS at parturition. Weight percentage of 14:1 (P = 0.001) was greatest in adipose tissue of calves suckling cows fed control and oleate; however, the percentages of 14:0, 15:0, 16:0, 16:1, 17:0, and 18:3n-3 were greater (P < 0.001) in adipose tissue from calves suckling cows fed control compared with calves suckling cows fed linoleate or oleate. Percentages of 18:0, 18:1trans-11, 18:2n-6, and cis-9, trans-11 CLA were greater (P < 0.001) in adipose tissue from calves suckling cows fed linoleate compared with calves suckling cows fed control and oleate. Calves suckling cows fed oleate had greater (P < 0.001) percentages of 18:1trans-9, 18:1trans-10, and 18:1cis-9 in adipose tissue than calves suckling cows fed control or linoleate. Calf plasma and adipose tissue fatty acid profiles were reflective of milk fatty acids. Because fatty acids play an important role in metabolic regulatory functions, changes in milk fatty acid profile should be considered when beef cows are fed lipid supplements.     

The effect of clover silage treated with acrylic acid on selected indicators of metabolism in cows around the time of parturition and the status of their calves]

A trial was conducted with 16 cows divided into control and test group (eight cows in either); since day 57.6 +/- 21.1 before parturition, test cows were given feed rations for 107 days which contained 16.0 kg clover-grass silage a day, treated with 3 l acrylic acid per t ensiled matter. Control group of cows was administered feed rations containing silage treated with 4 l formic acid per 1 t ensiled matter from day 55.5 +/- 21.9. In the blood (plasma) of test cows the alkaline phosphatase activity was increasing gradually, in the time after parturition a tendency of lower glucose (P 0.05 to 0.01), thyroxine and triiodothyronine concentrations was observed, and the phagocytal activity of leucocytes and its index decreased. The levels of ketone bodies and aspartate aminotransferase activity were found to be higher. In this period in urine the pH value and net acid-base output were lower, while the inorganic phosphorus concentration was higher. No difference were observed in colostrum density, liveweight of born calves and in the target metabolic parameters in the blood (plasma) of calves. In the 30-day period of investigation the cows of test group gave an average daily milk yield lower by 1.5 l (in comparison with control cows). The residues of acrylic acid (method sensitivity of 1.0 mg acrylic acid in 1 l sample) were not detected in their colostrum and milk.     

Differences in susceptibility to gastrointestinal nematode infection between Angus and Brangus cattle in south Louisiana

Breed susceptibility to nematode infection was evaluated in Angus (Bos taurus) and Brangus (B. indicus crossbreed) cattle. A cow-calf herd and a yearling replacement heifer herd were monitored during one grazing season. Calves were born in March and were weaned in October. Individual rectal fecal samples were collected monthly from the two herds and processed for fecal egg counts (FEC) and coprocultures. Cow and calf FEC increased from April, reaching maximum values during the summer. Angus cows and calves had significantly (p<0.05) greater FEC than Brangus cows and calves, and Haemonchus and Cooperia were the predominant genera. Replacement heifer FEC showed a similar pattern with maximum levels during late summer/fall, and Haemonchus was the predominant genus. No significant differences were seen between breeds, however, infection levels were consistently lower in Brangus heifers. Ostertagia was present in cows and heifers only in fall/winter, which is consistent with summer inhibition. The data suggested that cows were an important source of pasture contamination for their susceptible calves and that the Brangus breed was relatively more resistant to infection. The use of B. indicus crossbreeds may help in alleviating reliance on chemical control by reducing the rate of pasture contamination and subsequent infection losses.     

Metabolic profile of newborn calves and levels of immunoglobulins in the first days of life

After examination of the clinical state of 128 new-born calves, blood was collected from their vena jugularis for the determination of blood actual pH value, concentration of lactic acid, pCO2, base excess, buffer base and standard acid bicarbonate. The course and difficulty of parturition exerted a significant influence on the vitality of the calves and on the studied parameters of acid-base state. In the normally born calves, compared with those after dystocia, the following values were obtained: pH 7.20 +/- 0.03 : 7.11 +/- 0.07, pCO2 = 8.4 +/- 0.9 : 10.0 +/- 1.1 kPa, base excess -2.30 +/- 2.10 : 5.80 +/- 4.60 mmol/l, buffer base 43.0 +/- 2.4 : 39.5 +/- 6.5 mmol/l, standard acid bicarbonate 22.3 +/- 1.8 : 19.6 +/- 4.1 mmol/l and lactic acid concentration 5.6 +/- 2.0 : 10.7 +/- 5.1 mmol/l. The differences were statistically significant (P less than 0.05) and statistically highly significant (P less than 0.01). The continual study of the blood actual pH value and lactic acid concentration in the calves in the first 24 hours of life showed that with the same trend of changes in calves after dystocia the initial values were less favourable and that their normalization lasted longer. Attention is drawn to the importance of dystocia for the rise of respiratory metabolic acidosis and its effect on the vitality of newborn calves, and/or on their survival. The discussion deals with the importance of immunoglobulin levels in calves in the first days after birth for their further development. The determination of antibody content in colostral serum from the first milking in 33 and 29 cows on two farms showed great drawbacks in quality. A satisfactory level of IgG was found only in 36.36% and 58.62% of the cows, and a satisfactory level of IgM only in 12.12% and 24.13% of the studied cows. The determination of immunoglobulin content in their calves two to three days from birth (33 + 33 animals) showed normoglobulinemia only in 24.24% and 15.15% of cases. In 33 and 29 cows on two farms the colostrum serum from the first milking had an average content of immunoglobulins of class G amounting to 27.99 +/- 20.25 mg/ml and 36.95 +/- 21.62 mg/ml, and class M amounting to 3.64 +/- 1.25 and 2.04 +/- 1.42 mg/ml. Three days from birth, their calves had an IgG content of 4.25 +/- 2.57 mg/ml and 3.99 +/- 1.86 mg/ml and an IgM content of 0.30 +/- 0.20 and 6.38 +/- 0.25 mg/ml.     

Factors associated with in utero or periparturient transmission of bovine leukemia virus in calves on a California dairy.

A three-year prospective study involving 143 calves born from infected cows was undertaken on a California dairy to evaluate possible factors of the dam associated with bovine leukemia virus infection in utero or during the periparturient period. In utero or periparturient infection occurred at a rate of 4.8% and was more likely in calves born to cows with an average peripheral blood lymphocyte count during pregnancy greater than 12,000 cells/microL (p = 0.043) or in calves born to cows that developed malignant lymphoma (p = 0.00004), but not in calves born to cows with p-24 antibodies (p = 0.675).     

Usefulnes of cervical mucus of cattle for pregnancy tests

A qualitative fructose test was adapted for a pregnancy test in cattle. Cervical mucus was heated 1-2 minutes in a corn syrup-water solution according to the method of Hopwood. In mucus from 320 slaughtered cows there were 8.5% false positives among 118 nonpregnant and 5.0% false negatives among 202 pregnant cows. 6 distinct positives, 3 equivocal tests, and 2 definite negatives were recorded in 11 cases of intrauterine death with pseudopregnancy. The mucus from 56 live cows produced 9.7% false positives and 12.0% false negatives. Fructose contents were determined quantitatively in 96 cervical mucus samples: 60 pregnant cows averaged 148 mg%; 36 nonpregnant 34.9 mg% (p less than .005); and pregnant in the first 5 weeks 111 mg%. This method was 90% accurate in the first 5 weeks.     

Neospora caninum infection and congenital transmission: serological and parasitological study of cows up to the fourth gestation

In this paper, a parasitological and serological study performed in three cows up to the fourth gestation is reported in order to clarify the extent of vertical propagation and, secondly, in which period of gestation the recrudescence of previous infection occurs. The cows selected for the study delivered healthy but congenitally infected calves in first pregnancy. The parasite was found, by biological tests in Swiss mice, in all the placentas of the three cows examined, during the three subsequent gestations, at calving. The parasite was found, at slaughtering, in the brains of all nine calves born clinically healthy from the three cows as well. The serological profile, performed at monthly intervals on serum of the cows, showed that IgG and IgM increased in the third trimester of gestation; this rise of antibodies was constantly observed during the three gestations and in all three cows. In the calves, the IgG titres increase after colostrum consumption and an IgM peak at birth, were indicative of a late infection. These findings, along with negative results obtained by a serological study conducted simultaneously on 38 cows housed in the same stable as the experimental animals and the negative results obtained in isolating parasite or antibodies from farm dogs, suggest that N. caninum infection can be maintained over several bovine generations and that recrudescing persistent infection, rather than a new infection, explains the Neospora infection of calves.     

The influence of dietary selenium as selenium yeast or sodium selenite on the concentration of selenium in the milk of Suckler cows and on the selenium status of their calves

The aim of this trial was to determine whether the selenium status of suckling calves could be improved by supplementing their dams' diet with organic Se instead of sodium selenite. A herd of 103 Hereford cows, which were on grass paddocks all year round, was divided into two groups. Both groups had free access to a mineral supplement that contained 30 mg of Se/kg; for one group the source of the Se was a Se yeast product, and for the other group the source was sodium selenite. The basal feed contained .02 mg of Se/kg DM. During the trial, the mean daily consumption of the mineral supplement was approximately 110 g/cow. The calving season started in the middle of March and ended in the middle of May. Blood samples were taken from 11 cows and their calves in the yeast group and from nine in the selenite group at the end of April and again at the beginning of June, and milk samples were taken at the same times. At both samplings, the concentration of Se in whole blood and the activity of glutathione peroxidase (GSH-Px) in the erythrocytes of the cows and calves in the yeast group were higher than in the samples from the animals in the selenite group. The same pattern was seen for plasma, except for the cows at the first sampling. The mean concentrations of Se in whole blood from calves in the yeast and selenite groups were 130 and 84 microg/L, respectively, and plasma concentrations were 48 and 34 microg/ L, respectively. Mean Se concentration in the milk from the yeast group (17.3 microg/L) was higher than that in milk from the selenite group (12.7 microg/L). There were significant correlations (r = .59 to .68) between the concentrations of Se in the cow's milk or cow's whole blood compared with Se concentrations in the calves whole blood and plasma or with the erythrocyte GSH-Px activity of the calves. The Se status of the calves in the selenite group was considered to be marginal, but the status of the calves in the yeast group was considered to be adequate. Supplementation of the suckler cows' diet with organic Se in the form of Se yeast rather than sodium selenite improved the Se status of their calves when the Se was mixed into a mineral supplement containing 30 mg of Se/kg. In practice, such supplementation would probably eliminate the risk of nutritional muscular degeneration in suckling calves.     

Losses over a 2-year period associated with fetal infection with the bovine viral diarrhea virus in a beef cow-calf herd in Saskatchewan.

In 1992, significant calf losses occurred between birth and weaning in a 650-cow Saskatchewan beef herd. These losses occurred subsequent to ill-thrift and disease, and every calf necropsied was found to be persistently infected with bovine viral diarrhea virus (BVDV). The objectives of this study were to describe the losses associated with fetal infection with BVDV in this herd and to determine why they occurred. For investigative purposes, blood samples were collected from the entire cow herd and the surviving calves at pregnancy testing in 1992, and tested by virus isolation for BVDV. Between 51 and 71 persistently infected calves were born in 1992. Bovine viral diarrhea virus was only isolated from calves. The only confirmed fetal infections with BVDV were recorded as the birth of persistently infected calves. However, abortions, reduced pregnancy rates, and delayed calvings were also recorded in the cow herd and may have been the result of fetal infections. The herd was monitored again in 1993. Fetal infections with BVDV were recorded as the birth of stunted, deformed, and persistently infected calves. The greatest losses due to fetal infection with BVDV in the 2 years of this study occurred in cows that were 3-years-old at calving (second calves). Bovine viral diarrhea virus appears to have remained endemic in this herd by transmission from persistently infected calves on young 3- and 4-year-old cows to naive calved 2-year-old cows that were mingled with them annually for rebreeding. Significant numbers of the 2-year-old cows remained naive to BVDV, because they were segregated from persistently infected calves at weaning, preventing cross-infection with BVDV.     

In utero transmission of bovine leukemia virus

In an initial study, 18 calves born to cows persistently infected with bovine leukemia virus (BLV) were tested for infective virus and antibodies at birth, and no infected or seropositive animals were found. Four of these calves were maintained in quarters where infected animals were housed, and 3 of the 4 subsequently became infected. These were probably contact infections acquired during, or at some time after, birth. The remaining 14 calves were kept in isolation pens in a building housing no infected cattle. None of this group was found to be BLV infected during 1 year of observation. In further studies, 15 pregnant cows inoculated with BLV became infected. One abortion, considered to be unrelated to the BLV inoculation, occurred 38 days later. The remaining 14 cows gave birth to 1 dead and 14 live calves. The dead calf and its live twin were seropositive for BLV at birth, indicating that they had been infected in utero. The remaining 13 calves were negative for BLV antibodies at birth and remained so during 1 year of observation.     

Changes in plasma fibrinogen levels in experimental Mycoplasma bovis arthritis in calves

Plasma fibrinogen levels were measured as a means of following the course of an intravenous and intraperitoneal challenge of vaccinated and non-vaccinated animals in an experimental Mycoplasma bovis arthritis in calves. Intraperitoneal challenge failed to induce as much elevation of fibrinogen concentration as intravenous challenge in both the vaccinated and non-vaccinated groups.The elevation of fibrinogen levels among the vaccinated calves remained within the normal range of 300–800 mg% throughout, irrespective of the route of challenge. In contrast, the level rose to over 1600 mg% ten days postchallenge in all but one of the non-vaccinated calves that were challenged intravenously. The relatively low plasma fibrinogen levels in non-vaccinated calves that were challenged intraperitoneally correlated with the absence of arthritis in this group. In general, there was an inverse correlation between high fibrinogen levels and protection from M. bovis arthritis.     

Factors affecting dystocia and early calf mortality in Angus cows and heifers.

Calving performance records (965,417) from purebred American Angus herds throughout the United States were used to study dystocia and early calf mortality during the period from 1972 to 1985. A sample of 53 (n = 83,467) herds was used to establish reasonable limits on the expected frequency of dystocia and mortality within and among herds that have good reproductive management programs and to verify the frequencies of scores in all other herds (n = 4,130) reporting calving performance information. The data were analyzed by logistic regression models. Dystocia and perinatal mortality, to a lesser extent, were found to be more frequent in heifers than in cows. The odds of unassisted births vs births with major difficulty were 11.58 times greater in cows than in heifers. In heifers, the odds of an unassisted birth increased with age of dam and decreased with birth weight of calf. At a baseline age of 22 mo the odds of an unassisted birth for calves weighing 30 and 40 kg were .13 and .02 times lower than the odds for calves weighing 20 kg. Alternately, at 29 mo, the odds of an unassisted birth for heifers producing a 20-kg calf were 4.53 times greater than at 22 mo. Survival of calves to 24 h in heifers was primarily affected by birth weight. Heifers producing calves at intermediate weights of 29 kg had higher odds of producing live calves at all ages. Considering all heifers calving at 22 to 29 mo relative to 20-kg calves, the odds for survival to 24 h were 3.83 times greater for 29-kg calves and lower by a factor of .52 for 40-kg calves.