Type of cottonseed and level of gossypol in diets of lactating dairy cows: plasma gossypol, health, and reproductive performance.

Objectives were to determine effects of altering gossypol intake by feeding whole linted Upland (WUP) or a 1:2 blend of WUP and cracked Pima (BUPCP) cottonseed on plasma gossypol (PG) concentrations, reproduction, and health of Holstein cows. Cows, 813, on three dairy farms were assigned to one of two diets starting at 13 +/- 11 d in milk for a 170-d experiment. Diets contained 717 and 951 mg of free gossypol/kg of dry matter from WUP and BUPCP, respectively. Concentrations of PG, as well as the proportion of total gossypol (TG) as the minus isomer were higher for cows fed BUPCP vs cows fed WUP. Conception rate at the first postpartum artificial insemination did not differ between treatments. However, cows consuming the higher gossypol diet had reduced subsequent conception rates and a lower pregnancy rate. Incidence of abortions increased in the higher gossypol diet, and cows that aborted or remained open had higher PG concentrations. Increasing PG concentrations resulted in reduced conception rates and extended days open. The probability of conception after the first artificial insemination declined at a decreasing rate as the plasma TG increased. Incidence of health disorders were unaffected by gossypol intake and PG concentrations. Similarly, gossypol intake and PG concentrations had no effect on culling or mortality. Six cows died in each diet, and none had postmortem signs compatible with gossypol toxicity. Consumption of a high gossypol diet for 170 d had no effect on health of lactating dairy cows, but it increased PG concentrations and impaired reproductive performance.

Fecal shedding of Giardia duodenalis, Cryptosporidium parvum, Salmonella organisms, and Escherichia coli O157:H7 from llamas in California.

OBJECTIVE: To evaluate fecal shedding of Giardia duodenalis, Cryptosporidium parvum, Salmonella organisms, and Escherichia coli O157:H7 from llamas in California with respect to host factors and management practices. ANIMALS: 354 llamas from 33 facilities. PROCEDURE: Fecal specimens were collected and examined for G. duodenalis and C. parvum by means of immunofluorescent microscopy. Salmonella organisms were cultured by placing feces into selenite enrichment broth followed by selective media. Escherichia coli O157:H7 was cultured by use of modified tryptocase soy broth followed by sorbitol MacConkey agar, with suspect colonies confirmed by means of immunofluorescent microscopy. RESULTS: 12 of 354 fecal specimens (3.4%) had G. duodenalis cysts. Younger llamas (crias) were more likely to be shedding cysts, compared with older llamas. Farm-level factors that increased the risk of shedding were large numbers of yearlings on the property (> 10), smaller pen sizes, large numbers of crias born during the previous year (> 10), and large pen or pasture populations (> 20). None of the 354 fecal specimens had C. parvum oocysts. Seventy-six (from 7 facilities) and 192 (from 22 facilities) llamas were tested for Salmonella organisms and E. coli O157:H7, respectively. All fecal specimens had negative results for these bacteria. CONCLUSIONS AND CLINICAL RELEVANCE: Shedding of G. duodenalis was primarily limited to crias 1 to 4 months old. Llamas from properties with large numbers of crias born in the previous year, resulting in large numbers of yearlings in the current year, were at greater risk of infection. In addition, housing llamas in smaller pens or pastures and managing llamas and crias in large groups also increased the risk of G. duodenalis shedding.

Virulence factors in Escherichia coli isolated from the blood of bacteremic neonatal calves.

Twenty-five Escherichia coli isolates from the blood of critically ill bacteremic calves sampled in two separate studies on a calf-rearing farm housing over 15,000 calves, in the San Joaquin Valley, California were studied. Isolates were characterized for O serogroups and for pathotypes as determined by the presence of specific virulence factors including heat-labile enterotoxin (LT), heat-stable enterotoxins a and b (STa, STb), verotoxins 1 and 2 (VT1, VT2), cytotoxic necrotizing factor (CNF), aerobactin, intimin Eae and P, F17 and CS31A fimbrial adhesins, and resistance to bactericidal effects of serum. These isolates constituted a heterogeneous group. However, isolates were mostly aerobactin positive and often resistant to the bactericidal effects of serum. Isolates of pathotypes O78 (n=6), O119:CS31a (n=3), and P positive but O non-typeable (n=3) were associated with a high mortality rate. The remaining isolates belonged to diverse pathotypes, often possessing the adhesins P, F17, CS31A and Eae but belonging to O serogroups other than O78 and O119, and were less frequently associated with mortality. Although no virulence factor common to all isolates was identified, the capacity to use iron by the presence of aerobactin which is important to the capture of iron was a predominant factor. Moreover, certain pathotypes appear to be associated with primary colisepticemia whereas other pathotypes may cause a bacteremia without necessarily leading to septicemia.

Bacteriological culture of blood from critically ill neonatal calves.

The objectives of this study were to estimate the prevalence of bacteremia in critically ill, neonatal calves with severe diarrhea or depression, and to describe the variety of bacteria involved. Two studies were conducted in the summers of 1991 and 1993 involving 190 neonatal calves, 1-day to 19-days-old. Bacteremia was detected by blood culture in 31% (28/90) of calves in study 1, and in 24% (19/79) of ill calves and 0% (0/21) of control calves in study 2. Bacteria cultured from blood included Escherichia coli (51% of all isolates), other gram-negative enterics (25.5%), gram-negative anaerobes (5.9%), gram-positive cocci (11.8%), and gram-positive rods (5.9%). Among clinically ill calves, the average age was significantly lower in the blood culture-negative group (5.5 d) than in the blood culture-positive group (7.5 d) (P = 0.004). Mean serum IgG concentration was significantly (P = 0.0001) lower in blood culture-positive calves (1.146 g/L) than in blood culture-negative calves (3.077 g/L). The mortality rate was significantly (P < 0.0001) higher in the blood culture-positive group (57.4%) than in the blood culture-negative group (15.1%). Bacteremia appeared to be a frequent entity in this particular rearing situation. Early recognition of the problem, as well as appropriate treatment, may be beneficial in increasing survival rates. Results also support the need to address the failure of passive transfer of maternal antibodies to prevent bacteremia in calves.

Use of a clinical sepsis score for predicting bacteremia in neonatal dairy calves on a calf rearing farm.

In human, equine, and bovine neonates, early diagnosis of bacteremia remains a challenge for the internist. The objective of this study was to develop a predictive model for risk of bacteremia, based on a clinical evaluation system called the clinical sepsis score. Blood from 90 ill calves, 1- to 14-days-old from a calf-raising farm in the San Joaquin Valley of California was cultured. The calves were also scored according to a clinical score for hydration status, fecal appearance, general attitude, appearance of scleral vessels, and umbilical abnormality. Age, rectal temperature, heart rate, respiratory rate, and presence or absence of a focal site of infection were recorded. Prevalence of bacteremia was 31% (28/90). A logistic regression model indicated that high clinical score, presence of a focal infection, and increased age were associated with an increased risk of bacteremia in ill calves (P < 0.06). Calves for which the model predicted bacteremia with a probability > or = 40.8% were considered bacteremic, yielding acceptable sensitivity (75%) and specificity (71%) estimates. The predictive model was validated through a 2nd sampling of 100 calves (79 ill calves and 21 controls), of which 17 calves were bacteremic. The classification was 75% correct using the model, with an estimated sensitivity of 76% and specificity of 75%. Overall, results indicated that the model could be a useful tool for predicting bacteremia in ill calves in a clinical setting.

Passive immunotherapy in neonatal calves--II. The efficacy of a J5 Escherichia coli hyperimmune plasma as immunotherapy in neonatal calves.

Hyperimmunized bovine plasma containing antibodies to a mutant Escherichia coli O111:B4 (J5) was used to conduct a prospective double-blind clinical trial to evaluate its efficacy as an immunotherapy to bovine neonates in field conditions. Two- to three-day-old calves (N = 150) were randomized into three groups (n = 50) to receive (1) no plasma (NP) or (2) control (traces or no J5 antibody) bovine plasma (CP), or (3) hyperimmune bovine anti J5 plasma (HP) in two subcutaneous total doses of 10 ml kg-1 body weight at a 24 h interval. Various physiological, pathological and clinical parameters of the study subjects were observed up to three weeks while other data such as morbidity, mortality and the effect on heart girth increase were collected up to the end of the eighth week. Weekly serum total protein and immunoglobulin G (IgG) concentrations were preferentially increased from the baseline values in HP calves but not statistically significant (p > 0.05) in group comparison. Mean (geometric) serum J5 ELISA titers in the HP group were significantly (p < 0.001) higher than the other two groups that increased about 1-log by the first week of plasma intervention, followed by a gradual decline by the third week. Out of three total deaths due to septicemia and colitis, one was from the NP group while the other two were from the HP group. Morbidity as measured daily on a 13-point scoring scale were not statistically (p > 0.05) different among the groups. Variation in the mean heart-girth increase was non-significant (p > 0.05) among groups by the eighth week. Higher increase in heart girth was generally associated with higher initial serum IgG (p < 0.01) concentration. Our results suggest that this lot of hyperimmune J5 plasma at this dose was not superior to control plasma or to no intervention in terms of calf morbidity and mortality.

Reproductive performance in high producing dairy cows treated with recombinant bovine somatotropin.

The reproductive performance of 156 cows treated with recombinant bST for two consecutive lactations was assessed as part of a target animal safety study conducted in the San Joaquín Valley of central California. Daily intramuscular administration of 17.2, 51.6, and 86 mg of bST per cow started at d 70 postpartum and ended at dry-off or 305 d postpartum. The AI did not begin until d 70 postpartum. During the first lactation study, multiparous cows treated with bST had significantly decreased pregnancy rates, increased behavioral anestrus, and increased anestrus confirmed by palpation. Treated primiparous cows in first lactation had shorter mean days to first standing estrus. In the second lactation study, cows treated with bST had an increased rate of delayed uterine involution, cystic ovarian condition, behavioral anestrus, and anestrus confirmed by palpation. Progeny from the first lactation cows were evaluated for rates of growth, morbidity, mortality, and for reproductive performance; no difference was detected between the progeny from different groups.

Bovine ketosis and somatotrophin: risk factors for ketosis and effects of ketosis on health and production.

Aspects of the metabolism and health of 63 cows which had been treated with different amounts of bovine somatotrophin (BST) daily in the preceding lactation and 25 control cows were studied. The aims of the study were first, to identify cows with ketotic conditions, either by measurements of blood metabolite concentrations or by clinical observations, secondly, to evaluate the risk of such conditions in cows treated with BST in the preceding lactation, and thirdly, to examine the metabolic and production consequences of the ketotic conditions in an environment in which the cows' health, body condition and nutrition were closely observed. The cows were categorised objectively by the use of cluster analysis into non-ketotic cows and ketonaemic cows, on the basis of their plasma metabolite concentrations. Twelve of the control cows and none of the cows previously treated with BST were classified as ketonaemic. Similarly, nine of the control cows but only two of the cows previously treated with BST had clinical ketosis. Some, but not all, of the decrease in the risk of clinical ketosis was attributable to the lower body condition score of the cows previously treated with BST. The clinically ketotic cows had a greater risk of other illness in the first 10 days post partum than their herdmates, but the ketonaemic cows had a significantly lower risk of other disease in the first 10 days post partum. The ketonaemic control cows were significantly heavier than the non-ketotic control cows, but they maintained a higher dry matter intake than the latter cows, probably a key factor in reducing the risk of clinical ketosis.

Interval from calving to conception in high producing dairy cows treated with recombinant bovine somatotropin.

Intervals from calving to conception in cows treated for two lactations with recombinant bST were ascertained using survival analysis methods. Daily intramuscular administration of placebo, 17.2, 51.6, or 86 mg of bST per cow started at d 70 postpartum and ended at culling or drying off. Breeding began at d 70 postpartum. Multiparous cows treated during the first lactation had significantly longer intervals from calving to conception. Cows treated during the previous lactation, but not during the second lactation, had significantly shorter intervals from calving to conception. Cox proportional hazards regression analysis was used with adjustment for the confounding effect of serum metabolites, milk production, energy balance, and body condition.

Pregnancy incidence in high producing dairy cows treated with recombinant bovine somatotropin.

Reproductive performance in cows exposed for two lactations to recombinant bST was measured using unconditional logistic regression. Intramuscular administration of 17.2, 51.6, and 86 mg of recombinant bST/d per cow started at d 70 postpartum and ended at dry-off or 305 d postpartum. Performance was measured as the cumulative incidence of cows becoming pregnant by 305 d post-partum. Within each parity group, cows treated with bST had higher total milk yield. During the first study lactation, the log odds of a cow becoming pregnant decreased linearly as dose increased, following adjustment for serum cholesterol, blood urea N, average daily milk yield, peak milk yield, net energy balance, and body condition score. However, differences in pregnancy incidence between treated and untreated cows were statistically significant only at the higher dose categories, the 51.6 and 86.0 mg of recombinant bST per cow. During the second study lactation, pregnancy rates were similar to those in the first lactation; rates reduced as recombinant bST dose increased. The singular exception was for cows exposed to recombinant bST during the previous lactation but not during the second. In the latter group, previously treated cows had higher pregnancy incidence than did the controls.

Relationships between maternal and fetal liver copper, iron, manganese, and zinc concentrations and fetal development in California Holstein dairy cows.

Associations between maternal trace element deficiencies and abortion have been made for many mammalian species. Objectives of this study were to estimate and correlate maternal and fetal hepatic Cu, Fe, Mn, and Zn concentrations through gestation. Additionally, aborted fetuses, stratified by cause of abortion (infectious or noninfectious), were compared to size-matched nonaborted fetuses to examine for magnitude and direction of change in hepatic trace element status. Dam and fetal liver were removed at slaughter from 103 Holstein dairy cows judged grossly normal by ante- and postmortem examination. Liver samples were collected from fetuses submitted by veterinarians for routine diagnosis of abortion (n = 80). Hepatic Cu, Fe, Mn, and Zn concentrations were determined by flame spectrophotometry. Comparisons of groups, estimations of correlations, and derived prediction equations were made by least-squares methods. Maternal liver Cu, Fe, Mn, and Zn concentrations did not vary during gestation. Compared with the dam, fetal liver Fe and Zn concentrations were higher (P < 0.05), fetal Cu concentrations were similar (P > 0.05), and fetal liver Mn concentrations were lower (P < 0.05). As fetal size increased, fetal liver Cu and Zn concentrations increased (P < 0.05), fetal liver Fe concentration decreased (P < 0.05), and fetal liver Mn did not change (P > 0.05). Aborted fetuses had lower liver Cu, Mn, and Zn concentrations than did nonaborted fetuses (P < 0.05). Liver Fe concentration was lower in aborted fetuses than in nonaborted fetuses in the second trimester only (P < 0.05). Consistently lower liver Cu, Fe, Mn, and Zn concentrations in aborted fetuses suggest a nonspecific change in trace element status, which implies an effect of abortion, not a cause of abortion.

Efficacy of intramammary antibiotic therapy for treatment of clinical mastitis caused by environmental pathogens.

For three California dairy herds with bulk tank SCC < 200,000/ml, twice daily milking, and no mastitis vaccine, 254 quarters with mild clinical mastitis were randomly assigned to three groups. Group A (n = 74) was treated with 62.5 mg of intramammary amoxicillin every 12 h for three milkings. Group C (n = 75) was treated with 200 mg of intramammary cephapirin every 12 h for two milkings. Group O (n = 105) was treated with 100 units of intramuscular oxytocin every 12 h for two or three milkings. Aseptic pretreatment quarter samples revealed 94 (37%) coliforms, 65 (26%) environmental streptococci, 34 (13%) other bacteria, and 61 (24%) with no isolate on bovine blood agar plates. Contagious pathogens were not isolated. Clinical cure (return of quarter and milk to normal) and bacterial cure (absence of primary pathogen isolated pretreatment) were assessed at milking 8 and d 20 after initial treatment. No difference existed in clinical (67.6, 67.7, or 66.7%) or bacterial (43.9, 55.0 or 49.1%) cure rate among groups. Clinical cure rates did not differ when quarters were grouped by etiology, but clinical cure rates for quarters with pathogens other than streptococci or coliforms were lower in group O.

Efficacy of a dried colostrum powder in the prevention of disease in neonatal Holstein calves.

The efficacy of a dried colostrum powder, DCW Concentrate, as a colostrum supplement or substitute was tested using four groups of 15 calves. Physical condition and IgG status were examined during the first 30 d of life. Calves were fed the dried colostrum powder (group A), pooled colostrum (group C), or both (groups B and D) 2 h after birth. Calves fed 85 g of the dried colostrum powder dissolved in 3 kg of whole milk (group A) had significantly lower IgG concentrations 24 h after birth than calves of the other groups. Administration of 85 g of the dried colostrum powder plus 3 kg of colostrum (group C) did not lead to significantly higher IgG concentrations 24 h after birth than did administration of 3 kg of colostrum alone (group B). Calves fed 85 g of the dried colostrum powder plus 1.5 kg of colostrum (group D) had an IgG concentration at 24 h of age that was not significantly different from that of calves given 3 kg of colostrum (group B). Morbidity and mortality rates were not significantly different among groups. One calf died in each of groups A and B; no losses occurred in groups C and D. Body weight increase was not significantly different among groups.

Effect of graded concentrations of gossypol on calf performance: toxicological and pathological considerations.

The effects of feeding diets containing 0, 100, 200, 400, or 800 ppm of free gossypol were examined in 60 Holstein bull calves from 1 to 120 d of age. The concentrations of free gossypol were varied by varying amounts of cottonseed meals from three different sources. Cottonseed meal totaled 31% of each treatment ration. Feed consumption, BW, and blood parameters were collected on all calves at 30-d intervals throughout the trial. There were no significant differences between the groups for feed consumption, BW, or average daily gain. Changes in the group means for hematology and chemistry variables examined were modest and insufficient to distinguish diagnostically between safe and unsafe free gossypol concentrations for the different groups. Clinical evidence of disease was limited to the calves fed 400 or 800 ppm of free gossypol after 90 d of age. One calf in the group fed 400 ppm and 4 in the group fed 800 ppm died as a result of circulatory failure associated with gossypol consumption. We conclude from this study that a ration containing up to 200 ppm of free gossypol is safe, 400 ppm of free gossypol is toxic, and 800 ppm of free gossypol results in death losses. These results are compatible with previously reported naturally occurring toxicological outbreaks.

Time series cross-correlation analysis of postparturient relationships among serum metabolites and yield variables in Holstein cows.

Time series cross-correlation analysis was used to determine relationships among serum beta-hydroxybutyrate, glucose, FFA, cholesterol, milk yield, DMI, and estimated net energy balance for 42 d postpartum for 14 multiparous cows. Milk yield was positively associated with beta-hydroxybutyrate concentrations on the same day, and milk yield was a primary determinant of metabolic change. Dry matter intake was negatively correlated with beta-hydroxybutyrate concentrations 3 d later and on the same day. The data supported in vitro studies showing that FFA are positively associated with beta-hydroxybutyrate production, showed that glucose concentrations are negatively cross-correlated with beta-hydroxybutyrate concentrations, and found that estimated net energy balance is negatively cross-correlated with beta-hydroxybutyrate. Analyses suggested that serum glucose and cholesterol concentrations significantly decreased with increased milk yield; analyses also suggested that elevated beta-hydroxybutyrate concentrations were associated with decreases in milk yield 6 d later. beta-Hydroxybutyrate and FFA concentrations 3 to 9 d before parturition were positively related to cholesterol concentrations, and relationships were positive between estimated net energy balance and cholesterol, suggesting that cholesterol concentrations increased as precursors for cholesterol synthesis were available. Time series cross-correlation analysis was a useful tool in examining relationships among variables when repeated samples were obtained from the same individuals.

Impact of bovine somatotropin administration beginning at day 70 of lactation on serum metabolites, milk constituents, and production in cows previously exposed to exogenous somatotropin.

Metabolic and production responses are reported for 72 cows treated with bovine somatotropin (BST) for 30 days starting at day 70 of lactation. Of these 72 cows, 48 had been exposed in the preceding lactation to long-term treatment with BST at 3 dosages and 24 (controls) had not been given BST. Approximately half of the cows in each group were parity-2 cows, the rest were older. Comparisons between groups were made separately for parity-2, and older cows. Analyses, using pretreatment values of each variable as a covariate, indicated that older cows, but not parity-2 cows, significantly (P less than 0.05) increased milk production during treatment. Parity-2 cows, however, had a significantly higher milk fat percentage than controls following treatment. Cows treated with 51.6 or 86 mg BST/d in both parity groups had significantly higher serum-free fatty acids than controls. Estimated net energy balances were significantly lower for older treated cows, but did not significantly differ from controls for parity-2 treated cows. Older cows in the 86 mg of BST/d group tended to have higher concentrations of blood glucose than did older control-group cows. Treatment with BST did not significantly increase serum ketone concentrations in any group of animals, and none of the cows developed clinical ketosis during this period. Estimated net energy balance (ENEB) during treatment was a significant (P less than 0.05) covariate for free fatty acid concentrations in older cows and for milk fat percentage in parity-2 cows. Covariate adjusted analyses, using ENEB during treatment as a covariate, indicated that lipolytic stimuli already acting may be enhanced by treatment with BST, but a negative energy balance was not a necessary precondition for free fatty acid concentrations to increase following somatotropin treatment. Similarly, milk fat percentages for parity-2 treated cows were significantly (P less than 0.05) higher during treatment than controls when ENEB during treatment was used as a covariate. Increased milk fat concentrations in parity-2 treated cows were not associated with significant increases in the ratio of C18:C4-10 milk fatty acids, indicating that increased milk fat resulted from either an increase in incorporation of C18 fatty acids into milk fat coupled with an increase in de novo mammary synthesis of C4-10 milk fatty acids or an increase in C12-16 fatty acids that may arise either from increased tissue mobilization, from diet, or from de novo mammary synthesis.

Microbiologic investigation of an epizootic of mastitis caused by Serratia marcescens in a dairy herd.

An epizootic of subclinical and clinical mastitis caused by Serratia marcescens was investigated in a 1,000-cow dairy farm in California. Serratia marcescens was isolated from 13 to 18% of composite milk samples obtained from lactating dairy cows. During monthly milk sampling performed during a 4-month period, S marcescens was isolated from 38.8 to 62.3% of composite milk samples obtained from cows from which S marcescens was previously isolated. Few cows infected with S marcescens had evidence of clinical mastitis. Somatic cell count value was associated with isolation of S marcescens. Cows with somatic cell counts greater than 500,000 were 5.48 times as likely to have intramammary infections with S marcescens, compared with cows with somatic cell count less than or equal to 500,000. Lactation number also was associated with S marcescens intramammary infection. After adjusting for the effect of lactation number, cows with high somatic cell count values were 2.98 times as likely to have intramammary infection with S marcescens, compared with cows with low somatic cell counts. Infection with S marcescens was independent of days in lactation, production string, and daily milk production. Eleven months after the beginning of the epizootic, S marcescens was isolated from organic bedding samples obtained from the dairy. Despite numerous attempts, other sources of S marcescens could not be identified on this dairy.

Relation among body condition score, serum urea nitrogen and cholesterol concentrations, and reproductive performance in high-producing Holstein dairy cows in early lactation.

Body condition scoring (using a 5-point scale with quarter-point divisions) was performed on 66 Holstein dairy cows that began their second or later lactation in August, September, or October 1988. Cows' body condition was scored beginning on postpartum day 4 (+/- 1) and subsequently at postpartum days (+/- 1) 18, 32, 46, 60, 73 and 87. Blood samples were obtained on the same dates. Reproductive health examinations were conducted by 1 of 2 veterinarians beginning at postpartum day 21. Reproductive performance was evaluated in relation to body condition score and serum urea nitrogen and cholesterol concentrations. Number of days to first recorded signs of estrus and first breeding were not related to body condition score at calving, amount of condition loss, cumulative 80-day milk yield, or 305-day fat corrected milk yield. Cows that calved with body condition score greater than or equal to 3.50 required more days to conceive. Cows losing greater than 0.75 points of condition had longer days of conception. Body condition score at calving and amount of condition lost were not related to services per conception or diagnosis of follicular cyst. Cumulative 80-day milk yield was not related to days to conception or services per conception. Cows that produced greater than or equal to the mean 305-day milk yield required more services and had longer days to conception than cows that produced less than the mean 305-day milk yield.(ABSTRACT TRUNCATED AT 250 WORDS)

Relation among body condition score, milk production, and serum urea nitrogen and cholesterol concentrations in high-producing Holstein dairy cows in early lactation.

Body condition scoring (using a 5-point scale with quarter-point divisions) was performed on 66 Holstein dairy cows that began their second or later lactation in August, September, or October 1988. Body condition was scored, beginning on postpartum day 4(+/- 1) and subsequently at postpartum days (+/- 1) 18, 32, 46, 60, 73, and 87. Blood samples were obtained on the same dates. Kilograms of milk produced per cow was measured daily. Body condition score and changes in body condition score were evaluated in relation to daily milk production, cumulative 80-day milk yield, and serum urea nitrogen and cholesterol concentrations. Average daily milk production during week 1 was indicative of cumulative 80-day production, but not of 305-day milk yields. Cows that calved with body condition score greater than or equal to 3.50 did not differ in average daily milk production, cumulative 80-day milk yield, or 305-day milk yield, compared with cows that calved with body condition score less than 3.50. Cows that calved with body condition score greater than or equal to 3.50 lost more condition than did cows that calved with body condition score less than 3.50. Body condition score at calving and amount of body condition loss interacted with the rate of change in daily milk production. Serum urea nitrogen concentration did not differ for cows grouped by cumulative 80-day milk production or for cows grouped by amount of condition loss. Serum cholesterol values were higher than previously reported values and increased directly with milk production. Serum cholesterol values were inversely related to condition loss but changes in cholesterol concentration were not related to condition loss.

Postparturient metabolic and production responses in cows previously exposed to long-term treatment with somatotropin.

Postparturient metabolic and production responses were studied for 85 multiparous cows consisting of controls and animals that had been previously exposed to long-term treatment with bST. Older cows previously exposed to bST at high doses (51.6 mg/d) had lower milk yields than controls. However, there were no significant differences compared with controls in milk yield for lower dose (17.2 mg/d) older cows or parity 2 cow groups. The bST-treated groups had higher postpartum DMI, lower serum FFA, lower serum beta-hydroxybutyrate levels, and higher serum glucose than controls. Some bST-exposed groups had lower milk fat but higher milk protein levels. All bST-treated groups had significantly lower ratios of C18 to C4 to 10 milk fatty acids. Control cows of both parity groups were in higher body condition and weighed more than bST-treated cows prior to calving. The differences in postpartum metabolism may be attributed to differences in body composition resulting from bST treatment in the prior lactation, because use of body condition score prior to calving as a covariate did not substantially alter responses. The control cows probably had greater reserves of mobilizable lipid. These contentions are supported by changes in milk composition for bST-treated cows, which were consistent with animals of greater appetite, mobilizing less lipid. The bST-treated cows were probably more energetically efficient milk producers because they produced milk from feed rather than from mobilization of tissue stores. These data suggest that bST use in a prior lactation may have potential benefit in reducing risk of metabolic disorders associated with lipid mobilization in the postparturient period.