Search

The aims of this study were to compare methods for examining measurements of CH₄ and CO₂ emissions of dairy cows during milking and to assess repeatability and variation of CH₄ emissions among individual dairy cows. Measurements of CH₄ and CO₂ emissions from 36 cows were collected in 3 consecutive feeding periods. In the first period, cows were fed a commercial partial mixed ration (PMR) containing 69% forage. In the second and third periods, the same 36 cows were fed a high-forage PMR ration containing 75% forage, with either a high grass silage or high maize silage content. Emissions of CH₄ during each milking were examined using 2 methods. First, peaks in CH₄ concentration due to eructations during milking were quantified. Second, ratios of CH₄ and CO₂ average concentrations during milking were calculated. A linear mixed model was used to assess differences between PMR. Variation in CH₄ emissions was observed among cows after adjusting for effects of lactation number, week of lactation, diet, individual cow, and feeding period, with coefficients of variation estimated from variance components ranging from 11 to 14% across diets and methods of quantifying emissions. No significant difference was detected between the 3 PMR in CH₄ emissions estimated by either method. Emissions of CH₄ calculated from eructation peaks or as CH₄ to CO₂ ratio were positively associated with forage dry matter intake. Ranking of cows according to CH₄ emissions on different diets was correlated for both methods, although rank correlations and repeatability were greater for CH₄ concentration from eructation peaks than for CH₄-to-CO₂ ratio. We conclude that quantifying enteric CH₄ emissions either using eructation peaks in concentration or as CH₄-to-CO₂ ratio can provide highly repeatable phenotypes for ranking cows on CH₄ output.

Objectives of this study were to determine the physiological effects of psychological stress applied to dairy calves and to test if molasses consumption could be used to validate that a stressed condition was achieved. Twenty male calves (3 wk old) received jugular catheters and were randomly assigned to control (CTR; n = 4 pens of 1 calf per pen) or social stress treatments (STR; n = 4 pens of 4 calves per pen). The STR treatment included 5 cycles of 24-h isolation followed by regrouping with unfamiliar animals for 48 h (over 15 d). An ACTH challenge (0.1 IU/kg of body weight) was used to determine adrenal fatigue. Peak and total cortisol concentrations were greater for STR calves until the ACTH challenge. After the ACTH challenge, CTR calf cortisol increased and STR calf cortisol continued to decrease, suggesting adrenal fatigue. The number of calves that became positive for fecal shedding of Salmonella after the acute stress of being moved and the number of calves that were positive after the move decreased with each move. Fifty-six percent of STR calves changed from negative to positive for shedding after the first move compared with 18.75% of STR calves remaining negative after the third move. Difference in fecal shedding of Enterobacteriaceae from samples taken before and after moving calves on d 6 was less than that on d 2, 3, and 5. Leukocyte counts were not different, but trends for day effects were detected for neutrophil and monocyte percentages. Molasses consumption was greater for STR calves on d 2 and 11, as was total consumption. Latency to lie after eating also increased as the study progressed; STR calves required more time to lie after eating on d 12 than on d 3, and latency to lie was greater for STR than CTR on d 4, 8, 12, and 14. The STR calves also stood more than the CTR calves in the 4-h afternoon period on d 4, 5, 7, and 14. However, during the 4-h morning observations on d 14 (ACTH challenge), CTR calves stood more than STR calves. This model induced chronic stress, as characterized by adrenal fatigue, which was confirmed by molasses consumption and behavior changes. Therefore, molasses consumption could be used to confirm social stress in experimental models.

Feed sorting is a natural behavior of dairy cows that can result in inconsistencies in the nutritive value of a total mixed ration (TMR). The objective of this study was to determine the effects of replacing high-moisture corn with glycerol on feed sorting and the feed intake pattern of transition dairy cows. Multiparous Holstein cows (n=26) were paired by expected calving date, housed in individual tie stalls, and fed diets containing either glycerol or high-moisture corn once daily from d -28 to +56 relative to calving. Glycerol was included at 11.5 and 10.8% of the ration dry matter for the pre- and postpartum diets, respectively. The feed consumption pattern was determined by measuring TMR disappearance during the intervals from 0 to 4 h, 4 to 8 h, 8 to 12 h, and 12 to 24 h relative to feed delivery. Feed sorting was determined on d -16, -9, 9, 16, and 51 relative to calving at 4, 8, 12 and 24 h after feeding. The TMR particle size profile was determined at feed delivery and at 4, 8, 12, and 24 after feed delivery by using the Penn State Particle Separator (Nasco, Fort Atkinson, WI) to yield long (19 mm), medium (19 mm,8 mm), short (8 mm,1.18 mm), and fine (1.18 mm) particles. Overall feed intake did not differ between diets and was 14.7±0.4 and 20.2±0.5 kg/d for the pre- and postpartum intervals, respectively. During the prepartum period, glycerol decreased the amount of feed consumed during the first 4h after feed delivery (7.22 vs. 5.59±0.35 kg; control vs. glycerol, respectively) but increased feed consumed from 12 through 24 h after feed delivery (2.22 vs. 3.82±0.35 kg; control vs. glycerol, respectively). Similar effects on the feed consumption pattern were observed after calving. During the prepartum period, cows fed the control diet sorted against long particles, whereas cows fed glycerol did not sort against long particles (77.2 vs. 101.5±3.50% of expected intake for control vs. glycerol; significant treatment effect). The data indicate that addition of glycerol to the TMR alters the feed consumption pattern to increase feed consumption late in the day at the expense of feed consumed immediately after feeding, and it reduces sorting behavior against long particles. Together, these may reduce diurnal variations in the rumen environment to promote greater rumen health in transition cows.

Thirty-eight lactating dairy cows including 6 ruminally cannulated cows were used in a feeding study to assess effects of feed sources that differed in dietary nonfiber carbohydrate (NFC) composition and ruminal degradability of dietary protein (RDP) on production, ruminal, and plasma measures. The design was a partially balanced, incomplete Latin square with three 21-d periods and a 3 x 2 factorial arrangement of treatments. Samples and data were collected in the last 7 d of each period. Feed sources that differed in NFC profile were dry ground corn (GC; starch), dried citrus pulp (DCP; sugar and pectins), and sucrose+molasses (SM; sugar). Dietary RDP was altered by providing CP with soybean meal (+RDP) or substituting a heat-treated expeller soybean product for a portion of the soybean meal (-RDP). Diets were formulated to be isonitrogenous and similar in NFC concentration. Cows consuming GC had the greatest milk urea nitrogen and milk protein percentage and yield, tended to have the greatest dry matter intake, but had a lesser milk fat percentage compared with cows consuming DCP and SM. Sucrose+molasses diets supported greater dry matter intake, milk protein yield, and 3.5% fat- and protein-corrected milk yield than did DCP diets. On -RDP diets, milk protein percentage was less and milk urea nitrogen and protein yield tended to be less than for +RDP diets. Dry ground corn diverged from DCP and SM in the effect of NFC x RDP, with cows consuming GC having lesser milk yield, 3.5% fat- and protein-corrected milk yield, and efficiency with -RDP as compared with +RDP, whereas these production measures were greater with -RDP than +RDP for cows consuming DCP and SM. In contrast, in situ NDF digestibility at 30h for GC and SM was greater for -RDP as compared with +RDP, but the reverse was true for DCP. The lowest ruminal pH detected by 6h postfeeding was also influenced by the interaction of NFC x RDP, with cows consuming SM having a lower pH with +RDP than with -RDP and cows consuming DCP having a similar pH on either RDP treatment. Total rumen volatile fatty acid concentrations did not differ among diets, but acetate molar percent was greater for DCP than for SM, and GC had the lowest molar percent for butyrate and valerate and greatest branched-chain volatile fatty acid concentration. Valerate molar percent and NH(3) concentration tended to be greater with +RDP than with -RDP. Plasma glucose and insulin were both greater in cows receiving SM than in those receiving DCP. Protein degradability, NFC source, and their interactions affected lactation, ruminal, and blood measures, suggesting that these dietary factors warrant further consideration in diet formulation.

This study was conducted to determine the effect of experimentally increased glucose demand on voluntary consumption of molasses by dairy calves. Three-week-old calves received 0.365 g of phlorizin by s.c. injection. Urinary output and molasses consumption were measured hourly, and urinary glucose concentration was screened. Molasses consumption for the 24 h after treatment was (mean +/- SE) 72.0 g (+/-7) for the control group and 142 g (+/-1) for the phlorizin-treated group. Urinary output for the 8-h test period was 1.13 kg for the control group and 1.67 kg for the phlorizin-treated calves. Mean urinary glucose peaked at 10 g/L by 4 h after treatment for calves given phlorizin, whereas the concentration for the control group remained close to 0 g/L. Phlorizin treatment increased voluntary consumption of molasses in 3-wk-old Holstein calves.

The objective of this study was to use a within-cow, half-udder model to compare the effect of cessation of milk removal from mammary quarters within respective half udders at either 30 or 70 d before expected calving date (ECD) on the ability of the half udders to subsequently produce milk. Pregnant Holstein cows were assigned to control (n = 14) or treatment (TRT, n = 26) groups. All mammary quarters in the udder of cows in the control group had 70-d (68 +/- 9 d) dry periods, whereas in each cow of the TRT group, 1 randomly selected half udder was dried at 70 d before ECD and the other half udder continued to be milked twice daily until dried at 30 d before ECD. From 80 through 70 d before ECD, amounts of milk produced by the left and right half udders of cows in the TRT group were measured at the first-shift milking. No differences were detected in the actual or relative amounts of milk produced by the left (3.46 +/- 0.2 kg; 48.8 +/- 1.0%) and the right (3.63 +/- 0.2 kg; 51.2 +/- 1.0%) half udders. Furthermore, the actual and relative amounts of milk produced by the half udders (n = 12 left, 14 right) subsequently dry for 67 +/- 7 d (3.56 +/- 0.2 kg; 50.2 +/- 1.0%) and the half udders (n = 14 left, 12 right) subsequently dry for 27 +/- 7 d (3.54 +/- 0.2 kg; 49.8 +/- 1.0%) did not differ before they were dried. However, from 3 to 100 d of the subsequent lactation, the 30-d dry half udders produced 18.9% less milk than the 70-d dry half udders (16.3 vs. 20.1 +/- 1.0 kg/d). In addition, relative amounts of total-udder milk produced by the 30- and 70-d dry half udders in the same cow differed (44.9 vs. 55.1 +/- 0.2%, respectively). Cows in the control group produced more milk than cows in the TRT group through 80 DIM (39.5 vs. 35.2 +/- 0.6 kg/d), but not from 3 through 150 DIM (39.0 vs. 36.2 +/- 1.6 kg/d). Thus, half udders that produced the same actual and relative amounts of milk before being dried did not do so when given a 30-d dry period instead of a 70-d dry period. When compared with the pre-dry value (49.8%), the relative contribution of half udders dry for 30 d to the total milk yield during the first 100 DIM was decreased by 9.8%.

CD36, a common milk fat globule membrane glycoprotein, was isolated from skim milk by methods similar to those previously utilized for the isolation of sulfhydryl oxidase. Two separate methods that were employed, gave similar purity as observed by electrophoresis. The first was based on differential centrifugation and size-exclusion chromatography, whereas the second combined ultrafiltration and affinity chromatography. After significant purification, the protein was identified by Western blotting and sequence analysis. Deglycosylation decreased the apparent molecular mass from approximately 85 to 57 kDa. These results suggested tissue-specific glycosylation. The purified fractions also exhibited low levels of sulfhydryl oxidase activity, the significance of which will require further study.

Thirty-two lactating, multiparous Holstein cows were utilized in a 91-d experiment in Auburn, Alabama, during summer to determine whether rectal and skin temperatures and respiration rates are repeatable and interrelated and whether whole cottonseed or calcium salts of long-chain fatty acids (Megalac, Church & Dwight Co., Inc., Princeton, NJ) affected milk production or its constituents. Treatments were (I) control, (II) I plus 10.4% whole cottonseed, (III) I plus 2.6% Megalac, and (IV) I plus 5.2% whole cottonseed plus 1.3% Megalac. Data included 358 to 2644 measurements analyzed as a split-plot design of experiment. Only milk protein percentage and protein-to-fat ratio were significantly affected by dietary treatment. Milk protein percentage was depressed by dietary fat additions, especially by the combination of whole cottonseed and Megalac. Within lactation repeatabilities for milk, fat, protein, and SCM yields ranged from 0.44 to 0.66; two percentages and protein to fat ratio, 0.21 to 0.32; feed efficiency, 0.18; dry matter intake (DMI) and body weight, 0.98 and 0.84; rectal and skin temperatures and respiration rate, 0.001 to 0.055. Partial and simple correlations were similar in sign and magnitude. Noteworthy were partial correlations between milk yield and DMI, 0.367; milk yield and rectal temperature, -0.135; milkyield and respiration rate, 0.102. Skin temperature was unrelated to other variables. Respiration rate was correlated with DMI, 0.270. Results should help researchers designing future experiments involving these responses to predict the number of measures needed to detect differences.

The objective of this research was to determine whether different dry matter intakes (DMI) or forage percentages prepartum would have an impact on postpartum performance. Multiparous Holstein cows (n = 41) received either high (H) or low (L) forage rations that were fed free choice (F) or restricted (R), i.e., HF, HR, LF, and LR. The L rations were higher in net energy of lactation and lower in neutral detergent fiber concentrations. After calving, all cows were fed the same ration ad libitum. Prepartum DMI were 8.0 for R versus 12.4 kg/d for F with LF greater than HF (14.1 vs. 10.7 kg/d). Prepartum treatments did not affect postpartum means for DMI, milk yield, milk protein percentage, body weight, body condition score, or plasma glucose concentrations (overall means 1 to 40 DIM were, respectively, 21.1 kg/d, 34.0 kg/d, 3.03%, 624 kg, 3.2, and 66 mg/dl). However, curves from 1 to 40 DIM showed that DMI and milk yield were slightly higher in early lactation in cows whose DMI had been restricted prepartum but mean milk fat percentage was lower (3.10 vs. 3.42%). Plasma NEFA were higher and insulin lower in H versus L before and after calving. High DMI prepartum, at best, showed no advantage over restricted feeding.

Forty-eight lactating Holstein cows were fed low-Cu diets with 500 mg of supplemental Fe/kg of dry matter (DM), a Cu antagonist, for a 30-d Cu-depletion period. After depletion, two Fe treatments (0 and 500 mg of Fe/kg of dietary DM) and five Cu treatments (2 x 5 factorial arrangement) were compared over 83 d. The Cu treatments were control (basal diet containing 8 mg of Cu/kg of DM) and either 15 or 30 mg of supplemental Cu/kg of dietary DM from either CuSO4 or Cu-lysine. Feeding 500 mg of supplemental Fe/kg of DM (in addition to basal dietary concentration of 140 mg Fe/kg) depressed liver Cu in the absence of Cu supplementation. Apparent Cu retention, estimated from Cu intake minus fecal Cu, was increased greatly by Cu supplementation immediately after the depletion period but declined to very low net retention by d 45 of the 83-d experiment. There were no differences detected between CuSO4 and Cu-lysine except a tendency over time for Cu-lysine to maintain higher plasma Cu, especially in the absence of the Fe antagonist.

Correlations were obtained between 18 response variables of a Jersey herd (Florida Agricultural Experiment Station, Gainesville) for 374 first lactations. Estimates were from the use of multivariate, derivative-free, restricted maximum likelihood procedures with the simplex method of partial maximization. Estimates agreed closely with those obtained previously by other methods in this and other dairy populations. All correlations between yields were high and positive; those between yields and days from parturition to first service were negative and near zero. Correlations between yields and somatic cell scores were moderate and negative; those between yields and constituent percentages in general were negative, except for the yield and percentage of the same constituent. Genetic correlations between chloride content and somatic cells and between measures of somatic cells were 1.0. Results suggest that single-trait selection for milk yield should result in correlated increases in constituent yields with slight decreases in percentage composition of constituents and somatic cell counts.

First lactation DHI records of 4293 Holstein and 2143 Jersey cows from 14 herds for 1984 through 1992 in Florida were studied to estimate effects on milk, fat, and protein yields of milking three times daily. Analyses were by derivative-free REML using the animal model. Advantages of milking three times daily for 305 d compared with milking twice daily were 1226 (17.3%), 29 (12.3%), and 19 kg (8.8%) for the milk, fat, and protein yields for Holsteins, respectively, and 284 (6.3%), 13 (6.2%), and 7 kg (4.3%) for Jerseys. Additional research is needed to evaluate effects on other economically important traits such as composition, health, and reproduction. Economic studies are required to determine the efficacy of milking three times daily, especially for Jerseys with their relatively low response.

Records of yield and reproduction from 4293 Holstein and 2143 Jersey first lactation cows from eight Holstein and six Jersey herds were utilized to evaluate genetic parameters for Florida, a subtropical environment. Statistical analyses were by derivative-free REML with the animal model. Genetic variances were based on variation in estimated breeding values of individual cows. Heritabilities were .27 to .43 for yields (6 estimates), .38 to .51 for constituent percentages (4 estimates), and .025 to .056 for reproduction (6 estimates), which were similar to estimates for temperate areas from similar procedures. Also, correlations of breeding values between yields were high and between yields and reproduction were low and generally antagonistic. Correlated responses in calving interval from selection for yield, with selection intensities of 1.0 to 1.5, would be expected to lead to increases of 1.0 to 5.2 d per generation (12 estimates). Thus, estimates of genetic parameters and correlated responses in this subtropical environment did not differ appreciably from those that occur in temperate dairy areas.

Percentage of white coat color was measured visually on registry certificates of 4293 first lactation Holstein cows on eight Florida dairy farms; records of production and reproduction were obtained from DHI. Data were analyzed using derivative-free REML with an animal model to estimate heritability of nine performance measures and to establish their relationships with white percentage. Adjustment of other response variables for white percentage altered heritabilities very little. Regression of milk production on white percentage was 1.91 kg/1% white. Regression coefficients were negative for fat and protein percentages and positive for protein and fat production. Regression coefficients for reproductive traits on white percentage were negative (i.e., white was desirable) but were not statistically significant. Probability of survival to second parturition was higher but not significant for cows with higher white percentage, Interaction of white percentage and season for fat percentage and days open was significant. In a subtropical environment, white percentage appears to affect productive and perhaps reproductive performance. Economic aspects of selection for increased white percentage need to be investigated.

The objectives were to evaluate effects of jet aircraft noise before milking on milk yield and composition, amount of residual milk, and behavior of dairy cows. Thirty-six Holstein cows (79 to 155 DIM) were assigned to a partially balanced incomplete block design with three treatments. Cows received two of the three treatments during consecutive 21-d periods, each preceded by 5- to 7-d adjustment periods. Treatments were control (ambient noise) and ambient noise plus one of two recorded jet aircraft noises. Cows were exposed to jet noise up to four times daily on 10 to 12 d per period. Yields of milk, 3.5% FCM, residual milk, and components and component percentages were not affected significantly by exposure to recorded jet noise. Differences detected were due to time of milking, period, advancing stage of lactation, and management. Objective and subjective evaluations detected no evidence of behavioral responses, such as vocalization or aversive behaviors (startle, freeze, or retreat) at time of noise or more aggressive or agitated behavior during subsequent milking or postmilking. The lack of behavioral response was not caused by habituation of cows to noise during the 21-d periods.

Effects of increasing concentrations of alfalfa hay fed in diets containing corn silage, whole cottonseed, tallow, and yeast were studied using 36 midlactation Holstein cows in a 3 × 4 factorial arrangement of treatments with three forage and four fat treatments fed as TMR in three 28-d periods. Forages were 1) 50% corn silage, 2) 37.5% corn silage and 12.5% alfalfa hay, and 3) 25% corn silage and 25% alfalfa hay. Fat treatments were 1) control (0% added fat), 2) 2.5% tallow, 3) 2.5% tallow and 12% whole cottonseed, and 4) 12% whole cottonseed. Yeast was imposed across all treatments and fed to half of the cows continuously throughout the experiment. Statistical models including effect of treatment imposed in the previous period indicated no carry-over effects. Production of milk (21.0 vs. 22.8kg/d), fat (666 vs. 809g/d), FCM (19.9 vs. 22.9kg/d), and SCM (19.9 vs. 22.7kg/d) were lower for cows fed whole cottonseed-corn silage diets than for those fed whole cottonseed-alfalfa hay diets. Added tallow increased milk production with all forage treatments but tended to decrease milk fat percentage with corn silage versus alfalfa hay diets. Tendency toward lower DM, OM, NDF, and ADF digestibilities suggested that fats probably had more negative effects on ruminal fermentation when diets were based on corn silage as the only forage. The depression in milk production and fat percentage that was due to cottonseed or tallow inclusion in corn silage diets was overcome by replacing 25 to 50% of the corn silage DM with alfalfa hay. Yeast treatment had no effect on measured parameters.

Thirty-six early to midlactation Holstein cows were used in a 2 × 3 factorial design to determine effect of three concentrations of hydrolyzed feather meal (0, 3, or 6% of dietary DM) at two protein concentrations (14 or 18% of DM) in TMR on DMI, milk production and composition, and nutrient digestibilities. Diets (DM) contained 50% corn silage and 8% soybean hulls and were balanced with corn meal, soybean meal, and hydrolyzed feather meal. The experiment was conducted over three 28-d periods. Yeast (0 or 57 g/d) was fed continuously to half of the cows throughout all three periods. Concentration of feather meal had no effect on DMI and milk fat percentage at either protein concentration. A curvilinear effect of feather meal on milk production showed 3% feather meal to be beneficial at 14% CP but not at 18% CP. Milk protein percentage was affected adversely by feather meal concentration. Treatment with yeast culture decreased DMI (22.0 vs. 22.9 kg/d), but milk and SCM production and milk fat and protein percentages were not affected. Increasing feather meal had a negative linear effect on CP digestibility and a positive linear effect on NDF digestibility. Increasing dietary CP from 14 to 18% increased CP and NDF digestibilities. Yeast culture tended to increase NDF digestibility. Increasing dietary CP caused increases in blood urea N concentrations; increasing feather meal resulted in curvilinear increases in blood urea N. Dietary yeast culture decreased blood urea N.

Drawings from a random sample of 32 registry certificates were used to evaluate procedures for measuring the percentage of white coat color of Holstein cows. Measurements were obtained using a planimeter and by visual evaluations of two inspectors. Mean white percentage of the total cow, excluding face, was 27.8%. With the planimeter, correlations between white percentages on the drawing of the total cow and on the upper and lower body sections were .99 and .92; correlation between right and left sides of the same drawing of the total cow was .96. Percentage of white exhibited greatest variability relative to the mean when measured in the upper body (CV = 122). From upper body, white percentage was correlated >.97 between inspectors and planimeter and >.98 between inspectors. If errors were distributed normally, confidence limits of correlations would be narrow; e.g., 95% limits of correlation .96 are .92 to .98. However, percentage of white appears to be a nonnormal variable skewed to the right. Attempts to transform data to avoid a departure from normality were not successful; additional attempts using other transforms seem warranted. Visual appraisal appears to be an efficient procedure for evaluating percentage of white coat based on registry certificates.

Objectives were to determine the effect of dietary concentration of P in DM on routes of excretion of P and to evaluate direct and indirect measures of calculating DM digestibility and P excretion. Twelve lactating Holstein cows were fed 20 kg of DM containing .41% P daily for 4 wk and then were assigned randomly to one of three diets: low (.30%), medium (.41%), or high (.56%) in P for 9 wk. Total collections of excreta (feces and urine) and milk were made during wk 4, 7, 10, and 13. At wk 4, cows excreted 88.2% of P consumed daily: 68.6% of excreted P in feces, 1.0% in urine, and 30.3% secreted in milk. Cows assigned to the low P diet decreased intake by 26.8% and excretion of P in feces by 22.7% in wk 13 compared with wk 4, whereas cows fed the high P diet increased intake by 36.5% and excretion of P in feces by 48.6%. Digestibility of DM was 62.6% when calculated from total collection of feces but only 55.7 or 56.5% when estimated indirectly using Cr or acid detergent lignin as indigestible markers. Apparent excretion of P was less than that estimated using either of the marker techniques (49.7 vs. 59.1 and 58.1 +/- .7 g/d of P) because digestibility of DM was underestimated. A prediction equation was developed for P excretion based on P intake and milk production.

Records from Florida Agricultural Experiment Station dairy herd for 1144 heifers freshening from 1959 to 1979 were studied to evaluate effects of age and problems at parturition on subsequent yield and reproduction. Statistical analysis was by method of ordinary least squares analysis of variance; five measures of reproduction, survival to second lactation, and 15 measures of yield were studied. Mean first parturition age was 25.8 mo with 40% of individuals less than or equal to 23 mo; survival to second parturition was 67%. No effects of age at first parturition were detected on survival, postpartum reproductive performance, or milk composition other than lactose-mineral, chloride, and acidity percentages; effects on yield were similar to previous reports. Stillbirth did not affect subsequent reproductive performance but was associated with decreased milk yield: 181 kg or 5.2% of overall mean. Milk yield was depressed by 239 kg for retained fetal membrane, 173 kg for dystocia, and 98 kg for metritis; milk composition essentially was unaltered. Heritability of postpartum days to first estrus was .14; estimates were 0 for days to first service, days open, and calving interval. Additional research is needed on interrelationships of gestation length with subsequent yield and reproduction and in alleviating detrimental effects of problems at parturition.

Effects of several factors on reproductive performance were evaluated. Mean performance and number of observations were for days from parturition to first service, 93 and 7730; days from first to successful service, 35 and 11,751; days open, 123 and 8571; gestation length, 280 and 13,612; and calving interval, 400 and 8524. Data covered 52 yr during which no detectable trends in calving interval occurred; other variables changed slightly. Jerseys had 8 fewer d from parturition to first service, 16 fewer d from first service to conception, 8 fewer d open, and 8-d shorter calving intervals than did Guernseys and Holsteins, which did not differ. Cows freshening in warm rather than cool weather suffered by 7, 7, 12, and 13 d for these variables. Repeatabilities ranged from .05 to .12; heritabilities were .05 and .06. Nonmaternal estimate of heritability of gestation length was .22. Phenotypic and genetic correlations between days from parturition to first service and calving interval were .48 and .87; for days open and calving interval, they were .97 and .96. Although days from first to successful service were essentially uncorrelated with days open and calving interval phenotypically (.05), genetic correlations were greater than 1.0 and estimated as unity. Results show no discrepancy between estimates for measures of reproductive performance in a subtropical environment and numerous studies in temperate areas. Large studies from subtropical areas are sparse; essentially none concerns long-term trends.

Reproductive performance of five breeds (81% Holstein or Jersey) in the Florida Agricultural Experiment Station herd was evaluated from data collected over 20 yr. Data represented 1144 parturitions after gestations greater than 250 d with all twin births excluded. Number of services per conception was not affected by age at first insemination. Mean age of exposure to first service was 414 d; mean age at first parturition was 25.8 mo. Overall, 39.7% of heifers calved at 23 mo or less. Intermediate ages, 24 to 27 mo, comprised 33.9% of heifers, whereas 26.4% of heifers calved at greater than or equal to 28 mo. Overall incidences of problems at parturition were retained fetal membranes, 3.6%; dystocia, 3.8%; metritis, 10.5%; and stillbirth, 11.5%. Frequencies of stillbirth and retained fetal membranes apparently were not affected by age, but metritis increased linearly with age at first parturition. Holsteins experience higher incidences of all problems than did Jerseys. Heritability (from paternal half-sib correlation) of birth weights and gestation lengths were .31 and .24; genetic correlation was .14. Heritabilities of occurrence of stillbirth, retained fetal membranes, metritis, and dystocia were negative and considered to be 0. Heritabilities of age at first service, days from first service to conception, number of services, and age at first parturition were .22, .11, .05, and .43. Dairy producers can consider reducing age at first parturition to at least 22 mo, under environmental and management conditions of this study, without increased frequencies of problems at parturition.

The mechanism by which high density lipoprotein promotes spontaneous lipolysis in milk was investigated. Spontaneous milk samples were characterized by an elevated cream-associated lipoprotein lipase activity compared with nonspontaneous milk samples. This cream lipase activity was correlated (.70) with cold storage acid degree value. Blood preparations (serum, plasma) added to warm milk, upon milk cooling, caused correlated (.89) increases in cream lipase activity and acid degree values. Total milk lipase activity was not correlated with level of cold storage lipolysis; however, skim milk lipase activity was negatively correlated (–.38). Addition of high density lipoprotein to recombined milk caused transfer of active lipoprotein lipase from unheated skim milk onto fat globules, which had been recovered from milk heated to inactivate cream-associated lipoprotein lipase. Transfer of lipoprotein lipase to fat globules by high density lipoprotein occurred in a dose-response manner with a correlation of .68 between high density lipoprotein added and cream lipase activity. These observations supported the concept that biological variation in high density lipoprotein content of milk can contribute to the variability in spontaneous lipolysis observed among milk samples. This contribution by high density lipoprotein is mediated primarily through its ability to redistribute lipoprotein lipase toward fat globules rather than activation of the lipoprotein lipase that was initially associated with fat globules.

Effects of stage of lactation and pregnancy and their interactions on 17 milk yield and constituent traits of Holsteins and Jerseys were studied. Data were 11,120 Jersey and 11,092 Holstein daily milk samples. After adjustment for all other known and systematic genetic and environmental effects, stage of lactation influenced all traits and accounted for 11.8 to 26.3% of variation in yields and .2 to 9.9% in percentages. In general, yields declined and percentages increased after about 3 mo of lactation. Chloride percentage showed an initial decline and then a rise after 2 mo. Stage of pregnancy accounted for small but significant variation in most traits; variation was .2 to .4% and less than .1 to 3.0% in yields and percentages for Holsteins, and less than .1 to .2% and .1 to 1.1% for Jerseys. Interactions between stage of lactation and pregnancy were investigated by response surface methodology and found to be very small.

Milk samples (n = 1818), collected from 261 cows, were used to evaluate effect of time of onset of rapid cooling on milk fat hydrolysis. Aliquots, either cooled immediately or after 1 h at ambient temperarure, were analyzed for FFA content after storage at 4°C for 48 h. Acid degree values for immediately cooled aliquots were higher than delayed cooled aliquots following adjustment for days in milk, days pregnant, milk yield, and SCC (.76 vs. .71). Correlation of .89 existed between aliquots; however, within a sample, aliquot response on cooling was variable in direction and magnitude. Immediate cooling enhanced lipolysis associated with increased days pregnant, decreased milk yield, and increased SCC. Consequently, effect of immediate cooling on milk fat hydrolysis was greater in milk collected from late lactation cows.

Six midlactation Holstein cows were exposed to treatments of thermal comfort environments with ad libitum or restricted (70% of ad libitum) DM intake and a thermal stress environment with ad libitum intake in two balanced 3 X 3 Latin squares to evaluate effects on mammary blood flow and other physiological measurements. Daily DM intake decreased from 17.8 kg in thermal comfort with ad libitum intake to 12.5 kg in thermal comfort with restricted intake and to 14.8 kg in thermal stress. Daily milk production decreased from 23.9 kg in thermal comfort ad libitum to 22.2 kg in thermal comfort restricted and 21.6 kg in thermal stress. Mammary blood flows (half udder) over the entire sampling interval (18 h) were 5.1, 4.3, and 4.5 L/min for treatments: thermal comfort, ad libitum intake; thermal comfort, restricted intake; and thermal stress, ad libitum intake. Mammary blood flows did not differ significantly among between treatments. Relationship of hald udder blood flow (L/min) to previous day's DM intake (kg/d) was described by the linear equation: L/min = .49 + (.27 kg/d); r2 = .46; and the quadratic equation: L/min = 6.04 - (.54 kg/d) + (.03 [kg/d]2); r2 = .55. Mammary blood flows 10 min before through 10 min after milking machine attachment were greater for cows at thermal comfort and ad libitum intake than for cows at thermal comfort and restricted intake or thermal stress and ad libitum intake (5.5, 4.8, and 4.8 L/min).

The objectives of this experiment were to determine whether low doses of bovine somatotropin (bST) during the transition period and early lactation period improved dry matter intake (DMI), body weight (BW), or body condition score (BCS); provoked positive changes in concentrations of somatotropin, insulin, insulin-like growth factor-I (IGF-I), glucose, nonesterified fatty acids, and Ca; or improved milk yield (MY) response without obvious adverse effects on health status. Eighty-four multiparous Holstein cows completed treatments arranged in a 2 x 3 x 2 factorial design that included prepartum and postpartum bST, dry period (30 d dry, 30 d dry + estradiol cypionate, and 60 d dry), and prepartum anionic or cationic diets. Biweekly injections of bST began at 21 +/- 3 d before expected calving date through 42 +/- 2 d postpartum (control = 0 vs. bST = 10.2 mg of bST/d; POSILAC). At 56 +/- 2 d in milk, all cows were injected with a full dose of bST (500 mg of bST/14 d; POSILAC). During the prepartum period and during the first 28 d postpartum, no differences in mean BW, BCS, or DMI were detected between the bST treatment group and the control group. During the first 10 wk of lactation, cows in the bST treatment group had greater mean MY and 3.5% fat-corrected milk yield and lower SCC than did cows in the control group. When cows received a full dose of bST, an increase in milk production through wk 21 was maintained better by cows in the bST group. Mean concentrations of somatotropin, IGF-I, and insulin differed during the overall prepartum period (d -21 to -1). During the postpartum period (d 1 to 28), cows in the bST group had greater mean concentrations of somatotropin and IGF-I in plasma. Concentrations of Ca around calving did not differ because of bST treatment. Results suggest that changes in concentrations of blood measures provoked by injections of bST during the transition period and early lactation period resulted in improved metabolic status and production of the cows without apparent positive or negative effects on calving or health.

Objectives were to evaluate the effects of a low dose of bovine somatotropin (bST) injected prepartum and postpartum on body condition score (BCS), body weight (BW), and milk yield (MY) in cows as well as somatotropin insulin, insulin-like growth factor-I (IGF-I), glucose, and nonesterified fatty acids (NEFA) in plasma. Holstein cows nearing second or later parities were assigned randomly to control (CON = 98) or bST-treated (TRT = 95) groups. Biweekly injections of bST began 21 +/- 3 d before expected calving and continued through 42 d postpartum (CON vs. TRT; 0 vs. 10.2 mg of bST/ d). From 42 to 100 d postpartum, no cows received bST. During yr 1, somatotropin, IGF-I, insulin, NEFA, and glucose were measured in plasma samples from 82 cows. During yr 2, effects of bST on BCS and BW of 111 cows were evaluated, but no blood samples were collected. Milk yields through 100 d of all 193 cows were analyzed. Prepartum treatment with bST resulted in greater prepartum plasma concentrations of somatotropin, insulin, and numerically greater NEFA but did not affect glucose or IGF-I. Postpartum bST increased mean plasma concentrations of somatotropin and NEFA, but not INS, IGF-I, or glucose. Mean BCS of cows did not differ prepartum, around parturition, or postpartum. Although mean BW did not differ prepartum or around calving, cows receiving bST maintained greater BW postpartum. Cows receiving bST tended to have higher MY (6.6%) in the first 60 d of lactation, but differences did not persist through 100 d, including approximately 40 d when no cows received bST. Number of cows that were culled due to health (CON = 3 vs. TRT = 2) or died (CON = 3 vs. TRT = 1) were not affected by treatment. Low doses of bST in the transition period resulted in higher postpartum BW, quicker recovery of body condition during lactation, and significantly more milk during treatment.

Lactation records (n = 2362) of 1402 crossbred cows in 22 cooperating dairy herds in southeastern Brazil were evaluated. Cows were mixtures of Zebu (Gir, Guzera, and unknown) and European breeding (mostly Holstein). Lactation milk yields were expressed as total, 3050-d, or deviated 305-d yields, either adjusted or unadjusted for days in milk (DIM). Mean DIM was 280. Arithmetic means unadjusted for DIM were 1942, 1666, and 5 kg per record. Milk yields of daughters from sires of 6/8 and 7/8 European breeds were higher than yields of daughters from sires of 5/8 European breeds when data were either adjusted or unadjusted for DIM. The differences associated with breed group of sire were only slightly reduced when records were adjusted for DIM. There was no evidence of a decline in milk yield as the fraction of European breeding of the sire increased from 6/8 to 7/8. For a given breed group of sire, whether the grandsire was purebred or crossbred had no detectable effect. These results should be useful in determining strategies for crossbreeding of dairy cows in tropical areas, particularly when crossbred sires are used.

The purpose of this study was to evaluate whether the plasminogen and plasmin system within bovine mammary secretions was influenced by an estrogen treatment that was used to accelerate mammary tissue involution. Holstein cows were injected with 4ml of ethanol excipient (n = 21) or 15mg of estradiol-17 β (n = 23) on each of the 4 d that preceded final milk removal. Dates of final milk removal (d 0) were designated as 60 d prior to expected dates of calving. Each mammary quarter was sampled once to collect secretions that corresponded to d 0, 3, 11, and 25 or d 1, 7, 18, and 30 of the dry period. Concentrations of plasminogen, plasmin, and somatic cells in secretions increased earlier for treated cows than for control cows. The ratio of plasminogen to plasmin in secretions decreased earlier for treated cows than for control cows. These responses support the suggestion that the plasminogen and plasmin system is involved in the involution of bovine mammary tissue. Estrogen treatment increased the activation of plasminogen, which was evidenced by a precipitous decrease in the ratio of plasminogen to plasmin that occurred as concentrations of plasminogen and plasmin increased. The activation of plasminogen likely contributed to the increased rate of mammary tissue involution that was effected by exogenous estrogen. Endogenous estrogen secreted by the developing fetal and placental unit might mediate, in part, the gradual involution that occurs during lactation.

To evaluate whether estrogen hastened involution of mammary tissue, Holstein cows were injected with 4ml of ethanol excipient (n = 21) or 15mg of estradiol-17 β (n = 23) on each of the 4 d that preceded final milk removal. Dates of final milk removal (d 0) were designated as 60 d prior to expected dates of calving. Milk volumes were recorded, and samples were collected prior to the first and fourth injections. During the dry period, each mammary quarter within the cow was sampled once to collect secretions on dates that correspond to d 0, 3, 11, and 25 or 1, 7, 18, and 30 of the dry period. Milk synthesis and secretion declined abruptly because of treatment. The decreased concentrations of α-lactalbumin, lactose, citrate, and potassium in secretions of controls, as well as the increased somatic cells, protein, lactoferrin, and sodium, occurred earlier in secretions from treated cows. These shifts of approximately 6 d, relative to days dry, suggested that exogenous estradiol increased the involution rate of mammary tissue.

Four forage treatments (45% corn silage, 33.75% corn silage plus 11.25% alfalfa hay, 11.25% bermudagrass hay, or 11.25% cottonseed hulls on a DM basis) were arranged factorially with no added fat, 12.5% whole cottonseed, or 2.5% tallow. Different diets were fed during three 28-d periods to 20 control Holstein cows and to 20 cows receiving yeast continuously in a split-plot design. Milk yield of cows fed cottonseed hulls with corn silage was 2.4 kg/d higher than with corn silage plus bermudagrass hay and .7 kg/d higher than with corn silage only or corn silage plus alfalfa hay. Whole cottonseed depressed milk yield by 1 kg/d. Cows fed yeast had increased DMI, and yeast interacted with forage so that more milk was produced by cows fed alfalfa diets. Yeast depressed milk protein percentage. Holstein cows in a commercial Florida dairy were fed no yeast or 10 g/d continuously for 60 d; milk fat percentage was greater (3.51 vs. 3.37%) with yeast. In summary, effects on milk and SCM were positive when cottonseed hulls were utilized with corn silage, negative with whole cottonseed, and neutral with supplemental tallow. Yeast effects on SCM, although not significant for either experiment, tended to be positive for both (mean +1.2 kg/d per cow).

Economic aspects of reductions in reproductive efficiency associated with increased production of milk and fat were evaluated for Holsteins and Jerseys in Florida during warm and cool seasons. Net returns from sire selection for increased production were examined with and without incorporation of such negative effects. The economic framework is the application of risk analysis in portfolio selection to selection of dairy sires. Estimates of effects of production on reproduction were from an earlier study of 4293 Holstein and 2143 Jersey cows in first lactation on 14 Florida dairy farms in warm and cool seasons. The scenario represented the typically low reproductive efficiency of cows, especially Holsteins, during summer in Florida, although some statistics used represented US values. Least squares estimates of net returns after adjustment for reproductive losses showed major reductions in net returns for both breeds for both seasons, for example, $28 to $30/yr per lactation, representing 47 to 53% of predicted net returns for Holsteins and 27 to 31% for Jerseys. The results also suggested that increased use of young sires, which results generally in higher conception rates and lower semen costs, might be justified in tropical and subtropical areas, particularly during hot seasons.

This study compared diets supplemented with distillers dried grains plus solubles originating from whiskey distilling with those from fuel alcohol production or soybean meal. Forty-eight cows in mid and early lactation were offered a different dietary treatment in each of three 28-d periods. Dietary design included three supplements at 14 or 18% CP of dietary DM, with or without blood meal. Additionally, a third, darker, fuel ethanol source was added at 14 and 18% CP without blood meal during period 3 to incorporate greater variation in quality of distillers grains. No detectable differences occurred in DMI or in any variables because of blood meal. Milk yield was higher when cows were fed diets at 18% rather than at 14% CP. Cows fed the two lighter distillers grains diets yielded .8 kg/d more milk than cows fed soybean meal diets, and cows fed whiskey distillers grains yielded 1.3 kg/d more SCM than cows fed diets with darkest distillers grains. Milk protein percentage was depressed when the darkest distillers grains were fed. Distillers dried grains plus solubles can provide an excellent substitute for soybean meal and corn in dairy cow diets.

Percentage of white coat color was measured on registration certificates of 4293 Holstein heifers on eight dairy farms in Florida. Measurements of white percentage were by visual evaluation on one side of the upper body (head, neck. and trunk) only and obtained in increments of 5%. Mean, median, mode, standard deviation, and skewness of white percentage were 25.6, 15, 0, 26.9, and 1.03. Distribution of white percentages showed lack of normality. Original data were transformed using an extension of the Box-Cox transformation to approach normality and to provide maximum likelihood estimators of the transformed parameters. Heritability estimates for percentages of white coat color were computed using derivative-free REML with an animal model. Estimates of heritability were .715 from untransformed data and .779 for transformed. Standard errors of estimates were slightly lower (.032 vs. .035) following transformation. Additional study to find an improved transformation procedure still seems warranted.

Because some previous studies indicated that addition of dietary fat may delay milk yield response and that effects carry over after withdrawal, an objective of this reversal design with four 28-d periods was to estimate residual effects. Diets were fed 2 wk before period 1 to permit inclusion of pretreatment diet in the mathematical model and changed for each of 33 cows at the start of periods 1 through 3; period 4 treatments continued those for period 3. Diets were 50% corn silage supplemented to be 12% CP with soybean meal and urea; 15% CP with soybean meal, blood and soybean meals, or feather and soybean meals; and 18% CP with soybean meal or blood and soybean meals. Protein treatments were replicated in diets containing 2.0% Ca soaps of fatty acids. No carry-over effects were significant; however, yield increases from Ca soaps were not evident until wk 4. Diet CP had a positive linear effect on milk and SCM yields, BW, and blood urea N. Milk protein percentage was higher from soybean meal diets. Addition of dietary Ca soaps of fatty acids increased milk, protein, fat, and SCM yields. Milk protein percentage was depressed when Ca soaps of fatty acids were fed with blood meal but not with soybean meal. No positive responses were observed from increasing dietary undegradable protein with blood meal or feather meal.

To determine composition, milk samples were obtained at random from camels at two camel rearing areas near Riyadh, Saudi Arabia. Proximate analyses indicated 3.15% fat, 2.81% protein, 4.16% lactose, 10.95% total solids, .15% acidity, .83% ash, and 88.33% water. Mineral composition was (milligrams per gram) 30.03, Ca; 72.48, K; 43.10, Na; .28, Fe; .18, Pb; and 4.50, Mg. Results should contribute to the overall knowledge of camels as a food source, but much still needs to be learned if efficient improvement programs are to be initiated.

Holstein cows (n = 135) under commercial management were used to determine whether sometribove (recombinant methionyl bST, 25 mg/d) administered during the dry period affected milk yield during the ensuing lactation. Cows scheduled to begin lactations (greater than or equal to 2) during January to March were assigned randomly to treatments of sodium bicarbonate excipient (n = 67) or bST (25 mg/d, n = 68). Subcutaneous injections were given for 14 d, corresponding to d -21 to -7 relative to expected calving date. Days dry prior to first injection (64.0, 60.2) and number of injections received (13.9, 13.8) were similar for control and treatment groups, but days from last injection to calving (8.8, 7.1) differed. No differences in incidence of dystocia or udder edema were detected. Previous lactation yields were 8251 and 7952 kg, and yields for lactations following treatment were 8328 and 7852 kg, based on complete lactation data. Mean test date 3.5% FCM yields for control and treated groups during experimental lactation differed before (30.3 vs. 28.1 kg) but not after (29.5 vs. 28.4 kg) covariance adjustment for previous total lactation milk yield. Test of heterogeneity of regression provided no evidence that respective curves for FCM yield during lactation were not parallel or of different magnitude. Elevation of serum bST during 2 wk of the dry period resulted in no apparent increase in extent of mammogenesis or lactogenesis that was translated into an increase in milk yield.

Objectives were to determine concentrations of P in phytate in selected concentrates, disappearance of P in phytate from these concentrates in vitro, and extent of hydrolysis of phytate in vivo. Total P and P in phytate were determined for eight concentrates; 32 to 81% of total P was in phytate. Six concentrates were incubated in vitro to determine the extent of phytate disappearance from solids and its appearance and disappearance from solution. Greater than 90% of P in phytate disappeared from solids between 6 and 8 h of incubation in vitro (wheat middlings, rice bran, hominy, soybean meal, and dried distillers grains) or between 12 and 24 h (cottonseed meal). Phosphorus in phytate in solution was hydrolyzed by 12 h except for cottonseed meal (by 24 h). Hydrolysis of the inositol ring to release P in vivo was greater than 99%, based on total fecal collection from 11 cows and the use of Cr as an indigestible marker in excreta, and between 94 to 98% for the same samples when acid detergent lignin was used as an indigestible marker to calculate phytate disappearance. These results further indicate that P in phytate should be considered available to lactating dairy cows when rations to meet their P requirements are being formulated.

Thirty-six midlactation Holstein cows were used in a randomized incomplete block design to evaluate lactational responses to varying dietary concentrations of Mg supplemented by MgO or Mg chelate. Basal diet was 41:4:55 corn silage:cottonseed hulls:concentrate (.21% total Mg). Magnesium oxide was added to the basal diet to give .32, .37, and .43% total dietary Mg, and Mg chelate was added to provide .23, .25, and .27% Mg, DM basis. Dietary treatments were formulated to supply equal concentrations of bioavailable Mg from either Mg source. Dry matter intake and milk yield were greater by cows fed MgO-supplemented than Mg chelate-supplemented treatments. Milk fat percentages were not affected. Milk protein percentages increased with Mg chelate compared with protein percentages with MgO. Treatments did not affect gross efficiency (4% FCM/DM intake) or body weight change. Lack of response to Mg chelate suggested that either the bioavailability was not as high as assumed or that sufficient total bioavailable Mg was not provided in those treatments. A companion in vitro experiment showed that MgO-supplemented concentrates, with more total supplemental Mg, supplied two to three times more soluble Mg than Mg chelate-supplemented concentrates.