Search

Staphylococcal enterotoxin C (SEC), a superantigen, is the most frequently expressed enterotoxin by bovine strains of Staphylococcus aureus causing mastitis. To examine the possible impact of SEC on the immune response of the bovine mammary gland, we monitored changes in lymphocyte subpopulations in mammary glands of four lactating cows after intramammary instillation of S. aureus strain Rn4220 transformed with a plasmid containing a gene coding for SEC1. Four other lactating cows received the same strain transformed with the plasmid without the SEC1 gene (positive control), and four cows were untreated (negative control). Mammary quarter milk samples for somatic cell count (SCC) analysis and determination of N-acetyl-beta-D-glucosimindase (NAGase) activity levels were collected daily for 21 d postinstillation. Flow cytometry utilizing three-color analysis was used to phenotype lymphocyte subpopulations isolated from milk samples collected on d 0, 4, 7, 11, 14, 18, and 21 postinstillation from all the cows. Milk from mammary gland halves (positive control and experimental) or all mammary quarters (negative control) was collected for flow cytometric analysis. Increased NAGase activity, SCC, and isolated S. aureus demonstrated that infection was established in mammary quarters intrammarily instilled with bacteria. There were no significant differences (P0.05) in the proportions of BoCD4 helper T lymphocytes or BoCD8 cytotoxic T lymphocytes between the two infected treatment groups. There was a significant day x treatment difference of the proportion of a gammadelta T cell subpopulation that did not express BoCD2, but did express the ACT2 activation molecule and a significant treatment difference of a gammadelta T cell subpopulation that expressed BoCD2, but not the ACT2 activation molecule (P0.05). Results do not support the hypothesis that the presence of the gene for SEC1 alters the mammary BoCD4 or BoCD8 T lymphocyte response to infection.

This trial was to determine the effect of dietary rapeseed screenings on milk production, milk composition, and feed intake of lactating dairy cows. Pelleted rapeseed screenings were fed at 0, 7, and 14% of diet DM. Assignment of 36 multiparous Holstein cows was based upon parity and previous lactation performance. The experimental period was from parturition through wk 16 of lactation. The control ration had 3.1% ether extract, whereas the ration with 14% rapeseed screenings had 5.4% ether extract. The rapeseed screenings contained 52.2% of C18:1 and 24.2% of C18:2 as percentage of total fatty acids. There were no significant effects of dietary treatment on milk yield or feed intake. There were significant increases in milk fatty acids C18:1 and C18:2 for cows consuming the diets with rapeseed screenings. Treatment did not significantly affect milk protein percentage as measured by Kjeldahl N or by the infrared method. Increased unsaturated fatty acids in the milk of cows fed rapeseed screenings had no apparent effect on infrared fat analysis. There was no interaction of treatment and milk fat analysis method (infrared versus Babcock). Dietary treatment did not affect blood serum nonesterified fatty acid concentrations over the 16-wk period. In conclusion, rapeseed screenings, fed at levels up to 14% of the diet, did not affect milk yield, milk protein, or milk fat percentage but did change milk fatty acid composition.

A split-plot design with repeated measures was used to test the relationship between visual teat skin condition score, the degree of transepidermal water loss from the skin, and the colonization by Staphylococcus aureus on experimentally chapped and inoculated teats of 20 lactating Holstein cows. Visual teat skin chapping score and the number of S. aureus colonies obtained from a teat skin swab were correlated (r = 0.53). Transepidermal water loss and S. aureus count were not correlated (r = 0.02). Results indicated that visual teat skin evaluation is superior to measurements of transepidermal water loss in the prediction of the susceptibility of teat skin to colonization by S. aureus.

An incomplete block split-plot design with repeated measures was used to test the effects of eight combinations of premilking and postmilking teat disinfectants on teat skin and teat end condition over a 6-wk period. These combinations included iodine, sodium chlorite, lactic acid, and orthophosphoric acid. Visual assessments of teat skin and teat ends were made on the teats of 101 cows. Teat skin thickness, teat end thickness, and transepidermal water loss were assessed for the teats of 50 cows. The interaction of predip and postdip had no effect on teat condition. Postdip had a significant effect on transepidermal water loss, visual teat skin condition, and visual teat end condition. The 1% iodine postdip was associated with the poorest teat skin condition.

Effects of genetic merit on energy intake, milk yield, fat and protein percentages, BW, BW change, plasma concentration of bST, and plasma concentration of urea N were determined for 139 heifers. Heifers, daughters of bulls of high genetic merit (average +408 kg of PTA for milk) or of average genetic merit (average -153 kg of PTA for milk), were allotted to either a high or low energy diet. Heifers of high genetic merit yielded 8.1% more milk and had 7.7% higher bST concentration than did heifers of average genetic merit, which were 3% heavier than heifers of high genetic merit. There was no significant effect of genetic merit group on energy intake, plasma concentration of urea N, or percentages of fat and protein. Heifers fed the high energy diet consumed 35.1% more energy, yielded 11.8% more milk with a lower fat percentage, and weighed 3% more than did heifers fed the low energy diet. The high energy diet depressed bST concentration by 13.3% and plasma concentration of urea N by 14.2% compared with concentrations for heifers fed the low energy diet. Correlations among bST, BW, and energy intake were negative and significant. Correlations of bST concentration with milk yield, fat percentage, and protein percentage were not significant. Body weight, BW change, milk yield, and energy intake were negatively correlated with plasma concentration of urea N.

The objective of the study was to establish and compare equations that would estimate the body fat content of lactating dairy cows from different indirect techniques. The techniques used were body condition scoring, dilution of D 2 O in body water, and determination of mean fat cell size diameter of the subcutaneous, abdominal, and perirenal depots. Each technique was validated against direct determination of body fat content of the same lactating cows. To apply equations to high producing, lactating dairy cows, cows were from a herd producing more than 9500kg of FCM/305 d, were lactating, and were in less than average body condition. Eight days prior to slaughter, a single injection of D 2 O was injected into the jugular vein, and body dilution was followed for 4 d. Cows were scored for body condition on the day of injection and weighed daily for the 4 d prior to slaughter. Samples of subcutaneous, perirenal, and omental adipose depots were taken, and adipocyte size and number were determined. Body fat was not predicted well by D 2 O space alone, but inclusion of BW did improve the prediction of body fat from this variable. The best equations were derived from use of BW with body condition score or subcutaneous fat cell diameter: observed body fat=−122.1 + .21 × BW + 36.0 × body condition score, and −195.6 + .290 × BW + .927 × subcutaneous fat cell diameter; standard errors of the estimate were 4.6 and 5.5kg, respectively. Equations using diameters of abdominal and perirenal fat cells gave similar relationships. Equations using all four predictors (live BW, fat cell diameter, condition score, and D 2 O space) were only slightly improved over these equations. Thus, use of body condition score, adipocyte diameter, and BW in laboratory and field conditions may help in the study and management of the use of body fat in lactating dairy cows.

Practical relationships were determined between milk production, health, and reproduction with the amount and use of body fat in high producing lactating Holstein dairy cattle. Approximately 350 cows and heifers > 15 mo of age in a high producing herd were assigned body condition scores at monthly intervals for 24 mo. Production of 305-d FCM averaged 9541 kg (range 8826 to 10,818 kg). Body condition score at each of four calvings at 30, 60, 90, 120, and 305 DIM in each parity and loss in score in each lactation were summarized. Multiple regression related scores to milk and milk fat production, reproduction, and disease variables within and among lactations. No difference in score occurred at calving or at dry-off among parities. The range of body condition scores was less than is commonly reported; however, loss of condition increased with increasing parity from .3 in first lactation to .9 body condition score units in lactations > or = 4. The body condition score varied quadratically with DIM but, at a given DIM, was not related to the daily milk production on that DIM. Parity had a stronger relationship with milk and milk fat production than did body condition score. However, within lactation, body condition score at calving and the loss of score were related quadratically to milk production. No significant relationships of body condition score to the incidences of pyometra, metritis, retained placenta, cystic ovarian disease, AI per conception, days to first AI, or dystocia existed in this herd.

Diurnal changes in percents of inorganic phosphorus in plasma were measured in three Holstein cows fitted with indwelling jugular catheters. Blood was sampled 34 times over 48 h. Changes of inorganic phosphorus of blood plasma appeared to be related to patterns of feed consumption. In a second experiment, effects of diet, season of calving, stage of lactation, lactation number, and milk yield on inorganic phosphorus of plasma and milk were measured with 40 Holstein cows. Dietary treatments were 1.0% calcium, .31% phosphorus; 1.0% and .54%; 1.8% and .30%; 1.7% and .54%. Blood and milk samples were taken at wk 6 postpartum and every 5th wk thereafter. Inorganic phosphorus in plasma and milk was higher for cows in first lactation than multiparous cows. Cows which calved in November to December had the highest inorganic phosphorus in plasma but the lowest in milk. Month of year affected inorganic phosphorus in milk but not in plasma. Inorganic phosphorus in plasma increased as milk yields decreased and as inorganic phosphorus in milk decreased. Dietary phosphorus affected inorganic phosphorus in plasma but not in milk. The correlation between inorganic phosphorus in milk and plasma was -.15. These data indicate the limitations of using inorganic phosphorus in plasma or milk as sole or primary means of determining nutritional phosphorus status of lactating cows.

The objective was to determine the relationship between thawing time and post-thaw temperature when the final temperature of the semen was brought to 40 C. One ejaculate from each of 12 dairy bulls was packaged in .5-ml French straws. Semen in five straws from each ejaculate was thawed in a 35 c water bath for 12 s or 1 min. The straws were then immediately placed in water baths at 0, 10 or 20 C for 1 min and then transferred to a water bath at 40 C for 1 min. Control treatments were thawed at (1) 35 C for 1 min, plunged into a 35 C water bath for 1 min and transferred to a final water bath at 40 C for 1 min, and (2) thawed at 40 C for 1 min, plunged into 40 C water bath for 1 min and transferred to a final water bath at 40 C for 1 min. Semen was incubated at 40 C and evaluated at 0, 4 and 8 h of incubation for percentage of motile spermatozoa (%MOT) and percentage of spermatozoa with intact acrosomes (PIA). Semen thawed at 35 C for 12 s and held at 0 C before being warmed to 40 C sustained immediate acrosomal damage (P less than .05) due to a delay in complete thawing of the semen. Semen thawed at 35 C for 1 min, held at 0 C and then warmed to 40 C also sustained immediate acrosomal damage which was due to cold shock. Cold shock damage was greater than damage due to a delay in complete thawing, therefore, precautions should be taken to prevent post-thawing cold shock. The 10 C post-thaw treatment resulted in spermatozoal damage with both thawing times, however, the effects were latent since damage was not observed until the 4- and 8-h evaluations. The 20 C post-thaw treatment did not decrease (P greater than .05) % MOT or PIA with either thawing time.

Blood and milk were sampled and quarter California Mastitis Test scores were taken during four 2-wk periods from 45 lactating cows. Vitamin A and beta-carotene in plasma and milk were analyzed within 48 h after collection. Total vitamin A equivalent (2 X amount of beta-carotene plus amount of vitamin A) also was calculated. Additionally, the total amount of vitamin A and beta-carotene excreted in milk was calculated from concentrations of vitamin A and beta-carotene in milk and milk weights recorded on sampling day. Independent effects of lactation number, period of collection, days in lactation, and California Mastitis Test Scores (the highest test score of four quarters used in the analysis) were examined by least-squares procedures using each blood and milk measure as the dependent variable. Results showed a highly significant independent effect of California Mastitis Test Scores for concentrations of plasma vitamin A, beta-carotene, and total vitamin A equivalent. Cows with lower plasma vitamin A, beta-carotene, and total vitamin A equivalent had higher test scores than cows with higher vitamin A and beta-carotene. Similar comparisons for amount of milk vitamin A, beta-carotene, and total vitamin A equivalent and total amount of each component excreted in milk showed no significant independent effects attributed to California Mastitis Test. Therefore, low concentrations of vitamin A and beta-carotene in plasma were associated with severity of mastitis in cows.

Holstein calves were assigned to treatments of 1) pelleted prestarter (22% protein and 12% fat) and starter containing 10% alfalfa; 2) prestarter and starter containing 20% alfalfa; 3) no prestarter and starter containing 10% alfalfa; and 4) no prestarter and starter containing 20% alfalfa. Calves assigned to treatments 1 and 2 were fed 3.64 kg milk/d for 2 wk and calves assigned to treatments 3 and 4 were fed 3.64 kg milk/d for 3 wk and 1.82 kg milk/d for wk 4. Calves on treatments 2 and 3 were heavier at 10 wk but body weights and heights were similar by 6 mo. Rumen fluid and plasma measures were similar among treatments. Bull calves were assigned to treatments 1 and 3 and necropsied at 3 or 6 wk. Dry feed intakes to 3 wk and volatile fatty acid concentrations were greater for calves on treatment 1 than those on treatment 3. Wet weights of the empty reticulorumens were greater for calves on treatment 1 than those on treatment 3. Papillary development was not affected by weaning system. Calves weaned at 17 d and fed a prestarter have earlier rumen development than calves fed no prestarter and weaned later.

Effects of prepartum dietary crude protein on growth hormone, insulin in blood plasma, and subsequent reproduction and lactation were investigated in 30 Holsteins. Cows were fed either 80 or 100% of the crude protein recommended by National Research Council starting about 60 days precalving. Postcalving all animals were fed according to recommendations. Blood was sampled on days 220 (start of experiment), 250, 270, and 280 of gestation and on days 10 and 30 postpartum. Cows fed 80% crude protein prepartum showed decreased intake of dry matter and urea nitrogen in blood plasma prepartum, and yields of milk and total solids decreased by about 15%. Body weight changes through 30 days postpartum were not significantly different between treatments. There were no significant differences for growth hormone and insulin except growth hormone tended to be higher on day 270 of gestation for cows fed 80% crude protein. Insulin was negatively correlated with lactation number −.51 to −.56. Reproductive efficiency was similar between treatment groups. Lower crude protein intake during the dry period decreased dry matter intake and yields of milk and total solids.

The effect of four levels of progesterone on the occurrence and intensity of estrous behavior was determined in ovariectomized cows. Twelve Holsteins were bilaterally ovariectomized at least 2 mo before treatment. Progesterone (P4) was administered im two times/day for 5 d followed 72 h later with 2 mg estradiol (E2) im to induce estrous behavior. Treatments were control = oil, 100 mg P4/d, 300 mg P4/d and 500 mg P4/d. Each animal received all P4 treatments in a 4 X 4 Latin-square design. From d 2 through 6, with d 1 being the first day of P4 treatment, serum P4 concentrations averaged .3, 2.5, 6.1 and 12.3 ng/ml in treatments I to IV, respectively. Progesterone levels at the time of peak E2 (d9) were less than 1 ng/ml for treatments I, II and III and 1.8 ng/ml for treatment IV. Peak E2 levels for all groups averaged 23.9 pg/ml (12 h after E2 injection). Cows were observed continuously for 48 h after E2 injection to quantitate estrous behavior. Behavioral traits measured were: mounts initiated, mounts received, standing when mounted, chin rests initiated and chin rests received. Progesterone treatment caused a decrease in frequency of all five traits measured. As P4 levels increased, there was a linear (P less than .01) decrease in frequency of a behavioral trait. The percentage of the cows that showed each behavioral trait and mean time to first occurrence of each trait were not different after progesterone treatment, with the exception of standing behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipolytic adaptations of bovine adipose tissue during late pregnancy, lactation, and dry period were studied in Holsteins. Treatment groups consisted of first lactation daughters of high or low bulls based on Predicted Difference for milk. Heifers were fed either a 60% concentrate, 40% hay diet or a 40% concentrate, 60% hay diet from 0 to 140 d lactation. Feeding a low energy diet for the first 140 d of lactation did not affect adipose tissue lipolytic rates measured in vitro. Epinephrine and norepinephrine responsiveness of bovine adipose tissue increased prior to parturition, increased further in early lactation, then remained elevated during lactation and into the dry period. This responsiveness was unaffected by feeding low energy diets. Basal glycerol release in high genetic merit heifers was 64, 17, 40, 23, 20, and 42% greater than in low genetic merit heifers at -30, -15, 30, 60, 180, and 349 d about parturition. Response to norepinephrine was 15, 20, 18, and 15% greater in high genetic than low genetic merit heifers and response to epinephrine was 12, 20, 14, and 50% greater in high genetic than low genetic merit heifers at 30, 60, 180, and 349 d postpartum. The lack of a dietary energy restriction effect on lipolysis in early lactation suggested that these rates were near the physiological maximum for those animals. Rates of lipolysis were positively related with milk fat production. This study indicates a genetic component in adrenergic regulation of lipolysis in adipose tissue, independent of energy balance, in supporting lactation.

Effects of genetic selection for milk secretion and dietary energy restriction on adipose tissue lipid synthesis were tested in first lactation Holsteins. Daughters of bulls of 795 kg or 167 kg of Predicted Difference, base 1974, for milk had a 305 d first lactation of 8626 and 7038 kg of milk at 3.02 and 2.71% milk fat, respectively. Animals of each genetic group were allotted to treatments of a diet of 40% hay and 60% concentrate or of 60% hay, 40% concentrate ad libitum from 0 to 140 d of lactation. First lactation heifers fed the low energy diet ate 19% less net energy and produced 7% less milk of 28% more milk fat percent compared with heifers fed the high energy diet. Lipogenesis rates at 15, 30, 60, and 180 d postpartum in heifers fed low energy diets were 107, 66, 21, and 166% of those in heifers fed high energy diets. Rates of lipogenesis in adipose tissue of heifers of high genetic merit were 40, 10, 45, and 66% of those in low genetic merit heifers at 15, 30, 60, and 180 d postpartum. Lipogenesis in bovine adipose tissue homeostatically adapts to decreased energy intake and home orhetically adapts to genetically selected increase in milk fat secretion.

Semen from each of 10 Holstein bulls was extended to 15 X 10(6) total spermatozoa per dose in egg yolk-Tris and in egg yolk-Tris containing 20% (vol/vol) heat-treated heifer serum. Semen was used during 12 mo by 11 herdsmen-inseminators in four commercial dairy herds to inseminate 2820 Holstein cows on the first postpartum service. Percentage conception of cows free of clinical disorders at breeding was determined by rectal palpation at 30 to 60 days after insemination. Addition of serum to the extender did not influence percentage conception. A significant interaction of bull x seminal treatment was found. Least squares means of percentage conception to first service ranged from 45.3 to 59.9% among the 10 bulls. When bulls were classified as either high (greater than 55%), average (50 to 55%), or low conception (less than 50%), approximately 200 first services were required to classify correctly 80 to 90% of the bulls. Least squares means of conception rates ranged from 40.1 to 62.7% among the 11 herdsmen-inseminators. 1) Addition of heat-treated homologous heifer serum to the extender does not influence conception in a predictable fashion; 2) fertility inherent to the bull significantly influences conception; and 3) inseminator skill affects conception greatly.

Effects of management and environmental factors on reproductive performance were evaluated as part of a fertility experiment in four large commercial dairy herds. The herds were selected because they utilized routine herd health programs, kept complete reproduction records on all cows, were enrolled in Dairy Herd Improvement, and would follow the protocol of the experiment. Only data from first services following parturition were utilized, and conception was determined by rectal palpation. Information on over 2800 experimental breedings was collected during 13 mo. Percentage conception to first service was not affected by milk production during current or previous lactations. However, cows with higher production during current or previous lactations. However, cows with higher production during current or previous lactation had longer intervals to first service. Previous days dry did not affect conception or interval to first service significantly. Conception was less for cows with less than 50 days to first service (32%) than for cows with over 50 days to first service (49 to 57%). No differences were found among 10-day intervals to first service of over 50 days. Cows in third and later lactation had lower reproductive performance than cows in first or second lactation. Month of breeding did not affect conception significantly but did affect interval to first service. However, no seasonal trends were apparent. Differences among herds were significant for both conception and interval to first service.

We assessed the damage to frozen semen packaged in French straws stored for 2 yr in 60 on-the-farm semen tanks on 56 Washington dairy farms. Percentage of motilic spematozoa and percentage of spermatoza with intact acrosomes were not affected significantly by position of the semen on the rack (top or bottom goblet). The semen in 3 of the 60 tanks was lost to tank failure.

The objective of this study was to compare conception to artificial insemination (AI) services in dairy cattle when semen was deposited into the uterine body or into both uterine horns (cornual insemination). Nine herdsman inseminators (HI) in four commercial dairy herds in Washington constituted the experimental units. Herds ranged in size from 393 cows to 964 cows. The duration of the experiment was 12 mo in three herds and 18 mo in the fourth herd. At the beginning of the experiment all inseminators were trained to deposit semen in the body of the uterus. Inseminators were instructed to use this method for 6 mo. Following employment of body deposition, the same inseminators were retrained to deposit one-half of the semen into the right uterine horn and one-half into the left uterine horn. Cornual inseminations were performed for 6 mo. A total of 4,178 services constituted the data set. Milk samples were collected from cows on the day of insemination and later were assayed for progesterone (P4). There was variation (P less than .01) in conception associated with month of insemination and insemination method (P less than .001). The monthly variation was not associated with season of the year. Least squares means for conception when semen was deposited in the uterine body was 44.7%, compared with 64.6% when cornual insemination was employed. The insemination treatment X inseminator interaction was not significant. Results suggest that cornual insemination provides an alternative to deposition of semen in the uterine body.