Rates of hoof growth and wear in Holstein cattle

Rates of hoof growth and wear were recorded on 223 Holstein cows in two herds during 20 mo. Herd 1 was mainly on pasture or dirt lots, and herd 2 was completely or partially confined in a new freestall facility. Growth and wear were measured on both dorsal and lateral surfaces of front and rear outside claws. Lateral measurements were taken 1 cm in front of the junction of wall and heel. No differences were detected in rates of hoof growth for various places on the dorsal wall. Herd effects influenced rates of growth and wear. Cow differences were not significant for hoof growth but were for a few wear rates. Monthly rates of dorsal hoof growth during first lactation were 6.04 mm for front claws and 6.58 mm for rear claws. Corresponding monthly wear rates were 5.78 and 6.11 mm, respectively. Wear rates on front and rear claws decreased with advancing stage of lactation. Front hooves grew and wore less than rear hooves. Lateral walls grew faster and wore more than dorsal walls on both front and rear hooves. Cows completely confined had higher rates of hoof growth and wear than cows on pasture. Rates of growth and wear were lowest during winter and highest during spring and summer.     

Genetic parameters for claw disorders in Dutch dairy cattle and correlations with conformation traits

Impaired claw health is one of the major problems causing production loss and reduced animal welfare in dairy cattle. In response, the Dutch Animal Health Service (GD) Ltd. initiated this study, in which claws of lactating and near-term cows and heifers in 430 herds were trimmed by hoof trimmers and the health status of the rear claws recorded. Only herds with >75% of the animals having feet trimmed were considered, resulting in records on 21,611 animals. Eight claw disorders were scored: digital dermatitis (DD), interdigital dermatitis/heel horn erosions (IDHE), sole hemorrhage (SH), chronic laminitis (CL), sole ulcer (SU), white line disease (WLD), interdigital hyperplasia (HYP), and interdigital phlegmona (IP). The prevalence varied from 0.6% (IP) to 39.9% (SH). More than 70% of the animals had at least one claw disorder. Conformation traits and locomotion were recorded once during the animal's first lactation by trained classifiers of the Royal Dutch Cattle Syndicate and completely independent of the moment of claw trimming. Heritabilities were estimated using a sire model, and ranged from <0.01 (IP) to 0.10 (DD and HYP). Genetic correlations of incidences of claw disorders with locomotion were variable, ranging from 0.13 (SH) to −0.91 (CL). Genetic correlations with the rear leg conformation traits were lower, ranging from 0.04 (ID with rear leg side view) to −0.69 (IP with rear leg rear view).     

Induction of Lactation by Two Techniques: Success Rate,Milk Composition,Estrogen and Progesterone in Serum and Milk,and Ovarian Effects

Induction of lactation was attempted in 12 heifers and 12 cows with estradiol benzoate (.011 mg/kg body weight per day) subcutaneous for 10 days or that plus progesterone (.1 mg + .25 mg/kg body weight per day) for 7 days. Milking commenced on day 20 for those treated with the mixture and on day 11 for the others. Lactations were induced (minimum of 4.5 kg of milk/day) in five of six heifers and two of six cows by the mixture and in six of six heifers and three of six cows for estradiol benzoate. Milk production was 44% of herdmates in the 16 induced lactations. Cows on the single treatment had lower production than the other three groups. Ovarian status, cycling, cystic, or static, was affected adversely in 5 of 16 animals induced successfully. Two of the 16, both heifers, carried calves to term following induction. The transition to normal composition of milk was slower for single than double treatment. Lactose increased slowly to normal over the 1st wk of milking while protein decreased slowly. Estrogen and progesterone in milk of induced cows were approximately twice as concentrated as in normal post-parturient cows, probably because milk production was halved.     

Herdmates versus Contemporaries for Evaluating Progeny Tests of Dairy Bulls

Distributions of various kinds of herdmates, defined as nonpaternally related cows calving in the same moving 5- mo herd-year-season, were studied on 113,386 first and 70,044 second lactations initiated 1966 to 1968. These data were all the lactations available from 6,428 herds and 5 major dairy breeds. From 6 to 23% of progeny in first lactation sired by bulls in artificial insemination and 9 to 25% of the naturally sired progeny with a herdmate of some age did not have contemporary herdmates in first lactation. Similar values for second lactations were 10 to 28% and 15 to 29%. Only 1 to 5% did not have herdmates of some age. For those with herdmates, the average number of contemporaries ranged from 3 to 15 but were 5 to 10 for most groups. Numbers of herdmates ranged from 12 to 37, but most groups averaged over 20. Values for second lactation were lower. Biases against AI sired first lactations caused by comparing them to selected older cows were small in three breeds (+7 to ?10 kg) but were larger for Jerseys and Brown Swiss (?86 and ?115 kg). Biases against non-AI sired first lactation cows were of similar magnitudes. Larger biases resulted from comparing first lactations to only their first and second lactation herdmates. Sire summaries based on first lactation vs. first lactation herdmates would have a larger sampling variance (about 5 to 40%) but would not be biased by culling. Sampling variances would be lower when first lactations are compared to herdmates of all ages, but biases resulting from older cows being the survivors of culling for yield would be present. A modified contemporary comparison that uses all cows with at least one herdrnate of any age but that is unbiased by culling is presented.     

Genetic Trends Among Artificially Bred Holsteins in Quebec

Mixed-model methods were used to evaluate 52 Holstein sires in artificial insemination for milk, fat, and protein yield and fat and protein percent. A total of 3288 305-day first lactations of Holstein on the Dairy Herd Analysis Service were studied. Sires were grouped by year of first service, and groups were used to measure trends in the average generic merit of sires sampled. Annual genetic trends among sires were 85, 1.4, and 1.0 kg for milk, fat, and protein yield and kg for milk, fat, and protein yield and ?.029 and ?.031% for fat and protein test. Genetic trends among their daughters were estimated for Quebec herds according to relative sire usage. Trends in yields were positive. Average yearly genetic gains for milk, fat, and protein yield were 46, 1.1 and .5 kg for all herds and 57, 1.9, and 1.1 kg for herds in Analysis Service. Trends for milk composition were negative. Annual genetic declines in fat and protein percent were ?.004 and ?.008% for the population and ?.003 and ?.014% for herds in Analysis Service.     

Effect of dry period length on milk yield over multiple lactations

Shortening or omitting the dry period (DP) can improve the energy balance of dairy cows in early lactation through a decrease in milk yield after calving. Little is known about the effect of a short or no DP on milk yield over multiple lactations. Our objectives were (1) to assess the effect of DP length over multiple lactations on milk yield, and (2) to assess if the prediction of milk yield in response to DP length could be improved by including individual cow characteristics before calving. Lactation data (2007 to 2015) of 16 Dutch dairy farms that apply no or short DP were used to compute cumulative milk yield in the 60 d before calving (additional yield) and in the 305 d after calving (305-d yield), and the mean daily yield over the interval from 60 d before calving to 60 d before next calving (effective lactation yield). The DP categories were no (0 to 2 wk), short (3 to 5 wk), standard (6 to 8 wk), and long (9 to 12 wk). The effect of current DP and previous DP on yields was analyzed with mixed models (n = 1,420 lactations). The highest effective lactation yield of fat- and protein-corrected milk (FPCM) was observed for cows with a standard current DP (27.6 kg per day); a daily decrease was observed of 0.6 kg for a long DP, 1.0 kg for a short DP, and 2.0 kg for no DP. Previous DP did not significantly affect the effective lactation yield. Thus, cows can be managed with short or no DP over consecutive lactations without a change in quantity of milk losses. Cows that received no DP for consecutive lactations had a lower additional yield before calving (?172 kg of FPCM), but a higher 305-d yield (+560 kg of FPCM), compared with cows that received no DP for the first time. This could lessen the improvement of the energy balance in early lactation when no DP is applied a second time compared with the first time. For the second objective, a basic model was explored to predict effective lactation yield based on parity, DP length, and first-parity 305-d yield (n = 2,866 lactations). The basic model was subsequently extended with data about recent yield, days open, and somatic cell count. Extending the model reduced the error of individual predictions by only 6%. Therefore, the basic model seems sufficient to predict the effect of DP length on effective lactation yield. Other individual cow characteristics can still be relevant, however, to make a practical and tailored decision about DP length.     

Effects of Early and Late Breeding of Heifers on Multiple Lactation Performance of Dairy Cows

Dairy heifers were randomly divided into two treatment groups. One group of 253 heifers was bred at first estrus after 350 d of age and the second group of 249 heifers after reaching 462 d of age. Feeding and management practices were identical; groups differed only in age at first breeding. This report compares production of second and third lactations, reproductive traits observed during first and second lactations, and lifetime performance. Comparisons of heifer reproduction and first lactation production were reported earlier. Although the 462-d breeding age group of heifers had slightly better first lactation performances than the 350-d breeding age group, these advantages were not carried over to second and third lactations. No significant differences existed in three-parity performance between the two breeding groups. The 350-d breeding group had longer 61-mo productive life (730 vs. 623 d), produced greater 61-mo total milk (10,693 vs. 9218 kg), and yielded more milk per day of 61-mo herdlife (6.8 vs. 5.9 kg). A reduction of 1 mo in age at first calving would increase three-parity and 61-mo total milk by 427 and 554 kg, respectively. Results from this study suggest that early breeding is a viable and practical approach to improve profitability for the dairy industry.     

Breeding Practices on Selected North Carolina Dairy Farms

In 1978, 147 North Carolina dairy farms were surveyed concerning their breeding practices. Average herd size was 121 cows (range 24 to 440). Of 17,773 cows 78.5% and of 4,300 heifers 25.5% were bred by artificial insemination. Approximately 25% of dairymen indicated they had increased artificial insemination in the past 3 yr, whereas 12% reported less. A bull was used on 88% of farms. Herds having the same number of cows but using 100% artificial insemination on the milking herd averaged more days open (13.3), longer calving intervals (.44 mo), and more cows leaving the herd because of reproductive problems (8.3% vs. 5.8%) compared to herds using 80 to 99% artificial insemination. Herds using 0 to 75% artificial insemination were intermediate between the two. Herds using 100% artificial insemination and those using 80 to 99% averaged 7050 kg milk and 1.8 services per conception. Herds using 0 to 75% artificial insemination had lower milk production (480 kg). Larger herds had lower reproductive performance. Herds with higher average milk production had more services per conception. Average estimated transmitting abilities of 88 natural service sires were 371 kg milk, ?.05% fat and 10 kg fat.     

Sorghum forage in precision-fed dairy heifer diets

Sorghum forage is an alternative crop that is more adapted to drier conditions and more resistant than corn to drought conditions. Thus, sorghum forage maximizes water utilization. The objective of this study was to evaluate sorghum silage (SS), including digestibility and fermentation parameters, in precision-fed dairy heifers. Eight Holstein heifers (13.7 ± 0.6 mo of age and 364.8 ± 17.64 kg of body weight) fitted with rumen cannulas were used in a replicated 4 × 4 Latin Square design; treatments were 4 levels of forage to concentrate ratios (85:15, 75:25, 65:35, and 55:45). Rumen contents were sampled at various times to determine pH and volatile fatty acid concentrations. Dry matter (DM) and neutral detergent fiber (NDF) in situ degradation kinetics were compared between SS and corn silage (CS) diets. Fecal total collection was used to estimate apparent total-tract digestibility. Fecal grab samples at 0, 6, 12, and 18 h after feeding were used to estimate total-tract starch digestibility. Amount of concentrate in the diet affected the time that heifers spent eating as well as rumen pH. When the concentrate proportion of the diet increased, eating time and rumen pH decreased linearly. Total volatile fatty acid concentrations were not affected by treatment, but butyrate increased as the proportion of concentrate increased in the diet. Digestibility of DM and starch were higher in diets with lower forage to concentrate ratio, but NDF, acid detergent fiber, and hemicellulose digestibility were not affected. Corn silage had greater DM and NDF digestibility than SS. Also, fractional rate of digestion was faster for CS than SS (2.78 vs. 2.42% per hour, respectively). We conclude that fecal grab samples are suitable for predicting starch digestibility in heifers given the starch levels studied. In addition, SS was an adequate alternative forage in precision-fed dairy heifers with outcomes very similar to CS-based rations.     

Accelerated Growth and Early Breeding of Holstein Heifers

Twenty-four Holstein heifers were fed grain and alfalfa hay ad libitum for accelerated growth from 91 kg body weight until verification of pregnancy (Treatment A). Grain then was deleted until near time of freshening. They were bred at second estrus if they weighed at least 305 kg. An additional 24 heifers were fed a conventional roughage ration to allow a growth rate corresponding to the Beltsville growth standard and were bred when 15 to 16 mo of age (Treatment S). Observations were of growth rate, reproductive and productive performance, and length of herd life under normal culling.The A heifers gained 38% faster to 364 kg body weight (1.1 versus .8 kg/day). Average weights and ages were first estrus 275 kg, 8.3 mo (A), 288 kg, 10.2 mo (S); first breeding 319 kg, 9.6 mo (A), 392 kg, 16.8 mo (S); and first calving 560 kg, 19.7 mo (A), 26.9 mo (S). Differences in body dimensions at given weights were negligible. Treatment effects on dystocia were inconclusive. Lactation number, numbers of animals milked 100+ days, and average milk yields (kg) were: 1st lactation 24, 4436 (A), 22, 5415 (S); 2nd–22, 5295 (A), 18, 5903 (S); 3rd–12, 6278 (A), 10, 6407 (S); 4th–6, 7181 (A), 5, 5269 (S). Mean accumulative milk yields per animal to 36 mo of age were 7173 (A) and 4853 kg (S). Accelerated growth and early breeding did not affect herd life.     

Overstocking dairy cows during the dry period affects dehydroepiandrosterone and cortisol secretion

Stressful situations trigger several changes such as the secretion of cortisol and dehydroepiandrosterone (DHEA) from the adrenal cortex, in response to ACTH. The aim of this study was to verify whether overstocking during the dry period (from 21 ± 3 d to the expected calving until calving) affects DHEA and cortisol secretion and behavior in Holstein Friesian cows. Twenty-eight cows were randomly divided into 2 groups (14 animals each), balanced for the number of lactations, body condition score, and expected date of calving. Cows in the far-off phase of the dry period (from 60 to 21 d before the expected calving date) were housed together in a bedded pack. Then, animals from 21 ± 3 d before the expected calving until calving were housed in pens with the same size but under different crowding conditions due to the introduction of heifers (interference animals) into the pen. The control condition (CTR) had 2 animals per pen with 12.0 m² each, whereas the overstocked condition (OS) had 3 interference animals in the same pen with 4.8 m² for each animal. On d ?30 ± 3, ?21 ± 3, ?15 ± 3, ?10 ± 3, and ?5 ± 3 before and 10, 20, and 30 after calving, blood samples were collected from each cow for the determination of plasma DHEA and cortisol concentrations by RIA. Rumination time (min/d), activity (steps/h), lying time (min/d), and lying bouts (bouts/d) were individually recorded daily. In both groups, DHEA increased before calving and the concentration declined rapidly after parturition. Overstocking significantly increased DHEA concentration compared with the CTR group at d ?10 (1.79 ± 0.09 vs. 1.24 ± 0.14 pmol/mL), whereas an increase of cortisol was observed at d ?15 (3.64 ± 0.52 vs. 1.64 ± 0.46 ng/mL). The OS group showed significantly higher activity (steps/h) compared with the CTR group. Daily lying bouts tended to be higher for the OS group compared with CTR group in the first week of treatment. The overall results of this study documented that overstocking during the dry period was associated with a short-term changes in DHEA and cortisol but these hormonal modifications did not influence cow behavior.     

Effect of forage to concentrate ratio with sorghum silage as a source of forage on rumen fermentation,N balance,and purine derivative excretion in limit-fed dairy heifers

Sorghum silage has been shown to be a good alternative to corn silage for dairy cows; however, studies regarding heifers are insufficiently explored. Therefore, the objective of this study was to evaluate effects of changing forage to concentrate ratio (FOR:CON) in diets based on sorghum silage on N digestibility, rumen fermentation, N balance, C excretion, and microbial N yield in limit-fed dairy heifers. A split-plot 4 × 4 Latin square design with 19-d periods (15 d of adaptation and 4 d of sampling) was conducted with 8 rumen cannulated dairy heifers (age 13.7 ± 0.6 mo and weight 364.8 ± 17.6 kg). Heifers were fed sorghum silage–based diets with 4 FOR:CON (85:15, 75:25, 65:35, and 55:45) balanced for similar metabolizable energy intake per unit of body weight and crude protein concentration. Diets were fed to allow 900 to 1,000 g/d body weight gain and were fed once daily. Total collection of feces and urine was completed on d 15 to 19 to determine N, C, urea N, allantoin, uric acid, and creatinine excretion. Rumen contents were sampled on d 19 at 0, 1.5, 3, 4.5, 6, 9, 13, 17, 21, and 23 h after feeding to measure pH, volatile fatty acid (VFA), ammonia-N, and free AA concentrations. The pH decreased linearly while ammonia-N and free AA levels increased linearly with decreasing FOR:CON of diets. Although mean total VFA did not differ among treatment diets, molar proportions of VFA did. Acetate proportion decreased while propionate and butyrate increased with decreasing FOR:CON. Intake of N and urea N excretion decreased with decreasing forage proportion in diets while total N excretion, apparent N digestibility, and N retention were not different. Intake of C and excretion in feces (g/d) decreased linearly with decreasing FOR:CON in diets. Creatinine, allantoin, and uric acid excretion were not affected by FOR:CON; however, microbial N yield tended to increase linearly with greater concentrate in diets. Heifers limit fed diets based on sorghum silage demonstrated the effect of available ammonia-N and readily fermentable carbohydrates with subsequent effects on nutrient utilization when different FOR:CON were applied. Based on the presented results, FOR:CON 65:35 had the most suitable balance of available ammonia-N and readily fermentable carbohydrates for the most optimal results.     

An analysis of anterior scleral shape and its role in the design and fitting of scleral contact lenses

Purpose

The purpose of this study was to evaluate the shape of the anterior sclera by measuring the sagittal height and corneoscleral transition angles in the four cardinal and four oblique segments of the eye.

alpha-Amylase activity in rumen fluid of cows producing milk of low and normal fat content

α-Amylase activity in cell-free rumen fluid from lactating cows was measured by Phadebas amylase test. Effects of handling and storage of rumen fluid on α-amylase activity were determined. Assays of 35,000 × g centrifuged rumen fluid stored at ?18 °C showed good reproducibility, while reproducibility of assays of samples uncentrifuged prior to freezing was poor. In frozen stored samples of rumen fluid centrifuged at 35,000 × g or 3,200 × g, α-amylase activity decreased, whereas in frozen uncentrifuged samples α-amylase activity increased with storage time. α-Amylase activity was high and showed wide variations in one cow with experimentally induced low milk fat syndrome. Enzymatic activity was correlated negatively with rumen pH and positively with total concentration of volatile fatty acids. α-Amylase activity was significantly higher in rumen fluid samples from cows with low milk fat in conventional herds compared to cows with normal milk fat in the same herds. Enzymatic activity showed negative correlation coefficients with milk fat percentage and positive with total viable counts of rumen bacteria and mole percent of rumen propionic acid in the low milk fat cows but not in the cows with normal milk fat. α-Amylase activity in cell-free rumen fluid may be a useful indicator of activity of starch-hydrolyzing rumen microorganisms.     

Genetic parameters for feet and leg traits evaluated in different environments

The objective of this study was to test for genotype x environmental interaction (GXE) for feet and leg traits scored in different environments. Genetic correlations of seven feet and leg traits were estimated across different management systems: free versus tie stalls, slatted versus solid flooring, and intact versus trimmed hooves. Data were records from first-lactation Holstein cattle. Traits were claw uniformity, depth of heel, rear leg rear view, foot angle, bone quality, rear leg side view, and overall feet and legs. Different subsets of data were used for each comparison, resulting in 147,400; 53,550; and 145,160 records for housing, flooring, and hoof trimming management systems, respectively. Genetic parameters were estimated using REML and two-trait models in which for each animal a given trait was observed in one environment and missing in the other. Phenotypic scores were lower with tie stalls, slatted floors, and no trimming. Heritabilities tended to be greater in herds with tie stalls and slatted floors. Trimming had little effect on genetic parameters. The genetic correlations of feet and leg traits across pairs of management systems were > or = 0.85, except for rear legs, rear view. Therefore, effects of GXE were assumed to be of little importance and modification of genetic evaluation procedures on the basis of housing, flooring, and hoof conditions seems unnecessary.     

Effect of β-Lactoglobulin Variant and Environmental Factors on Variation in the Detailed Composition of Bovine Milk Serum Proteins

Between November 1979 and November 1981, 17,086 test-day milk samples were collected from individual Holstein cows in 62 Quebec herds. Samples were analyzed for protein, fat, casein, serum protein, somatic cell count, and the relative percentages of β-lactoglobulin, α-lactalbumin, bovine serum albumin, and the immunoglobulins. Cows included in the study were phenotyped with respect to β-lactoglobulin. Unadjusted means ± standard error for the relative percentages of β-lactoglobulin, α-lactalbumin, bovine serum albumin, and immunoglobulins were 64.80 ± .07%, 21.54 ± .05%, 6.51 ± .02%, and 7.15 ± .04%. Least-square analyses showed that month of test, stage of lactation, age of cow, somatic cell count, and phenotype of the cow for β-lactoglobulin had significant effects on the relative percentages of β-lactoglobulin, α-lactalbumin, bovine serum albumin, and immunoglobulins. Test-day milk yield, fat percent, protein percent, casein percent, casein number, and serum protein percent, when included in a statistical model as covariates, had a significant effect on the relative percentage of Ig. Relative proportion of β-lactoglobulin and α-lactalbuminim were not significantly affected by serum protein and total protein contents. For bovine serum albumin, only the covariates fat percent and serum protein percent were not significant.     

Clinical trial on the effects of a free-access acidified milk replacer feeding program on the health and growth of dairy replacement heifers and veal calves

The objectives of this study were to evaluate the effects of free-access acidified milk replacer feeding on the pre- and postweaning health of dairy and veal calves. Individually housed calves were systematically assigned at birth to 1 of 2 feeding programs: free-access feeding (ad libitum) of acidified milk replacer (ACD, n = 249) or traditional restricted feeding (3 L fed twice daily) of milk replacer (RES, n = 249). Calves were fed milk replacer containing 24% crude protein and 18% fat. Acidified milk replacer was prepared to a target pH between 4.0 and 4.5 using formic acid. Calves were weaned off milk replacer at approximately 6 wk of age. Weaning occurred over 5 d, and during this weaning period, ACD calves had access to milk replacer for 12 h/d and RES calves were offered only one feeding of milk replacer (3 L) daily. Calves were monitored daily for signs of disease. Fecal consistency scores were assigned each week from birth until weaning. A subset of calves was systematically selected for fecal sampling at 3 time points between 7 and 27 d of age. Fecal samples were analyzed for enterotoxigenic Escherichia coli F5, Cryptosporidium parvum, rotavirus, and coronavirus. Hip width, hip height, body length, heart girth, and body weight were measured at birth and weaning. Postweaning body weight measurements were collected from the heifers at approximately 8 mo of age. Postweaning body weight and carcass grading information was collected from the veal calves at slaughter once a live weight between 300 and 350 kg had been achieved. The odds of ACD calves being treated for a preweaning disease event tended to be lower than that of the RES calves (1.2 vs. 5.2%, respectively). Preweaning mortality, postweaning disease treatment, and postweaning mortality did not differ between feeding treatments. The ACD feeding treatment supported greater preweaning average daily gain (0.59 vs. 0.43 kg/d) and structural growth than RES feeding. Postweaning average daily gain and carcass characteristics were similar for ACD and RES calves. These results indicate that free-access acidified milk replacer feeding tended to support improved health, and greater body weight gain and structural growth during the preweaning period; these effects did not persist in the postweaning period. The growth advantage observed before weaning in the ACD calves likely disappeared due to the weaning methods used.     

Interrelationships With Estrous Behavior and Conception in Dairy Cattle

A total of 199 inseminations and estrous periods of lactating cows and heifers of breeding age were used to assess behavioral, productive, environmental, and hormonal events at first observation of estrus and those 12 h later with concurrent breeding efficiencies. Cattle were observed twice daily for estrus, and blood samples were collected at the initial observation of estrus (0 h) and at 12 h. Fifty-one percent of the cattle first were detected in estrus in the morning. Morning estrous activity was greater (11.4 mounts/h) than that first observed in the evening (7.6). Mean estrous activity declined from 9.4 mounts/h at 0 h to 1.6 mounts/h at 12 h. Older cows exhibited more mounting activity than younger animals at 0 h. Barn housed cattle exhibited more mounts/h during detection of estrus (11.2) than cattle housed primarily in free stalls (6.5) or pasture (5.4). Early estrous activity (0 h) was not affected by estradiol, progesterone, or luteinizing hormone. However, estradiol and progesterone did exert an influence on activity seen at late estrus (12 h). Glucose and urea at 0 and 12 h were similar. There were no significant correlations of glucose or urea of plasma with estrous activity or conception. Feed intake and milk production from 3 days prior to 3 days postestrus did not change. Season affected estrous activity and conception. Highest conception was associated with low progesterone at 12 h.     

Phenotypic effects of subclinical paratuberculosis (Johne’s disease) in dairy cattle

The effect of subclinical paratuberculosis (or Johne’s disease) risk status on performance, health, and fertility was studied in 58,096 UK Holstein-Friesian cows with 156,837 lactations across lactations 1 to 3. Low-, medium-, and high-risk group categories were allocated to cows determined by a minimum of 4 ELISA milk tests taken at any time during their lactating life. Lactation curves of daily milk, protein, and fat yields and protein and fat percentage, together with log_e-transformed somatic cell count, were estimated using a random regression model to quantify differences between risk groups. The effect of subclinical paratuberculosis risk groups on fertility, lactation-average somatic cell count, and mastitis were analyzed using linear regression fitting risk group as a fixed effect. Milk yield losses associated with high-risk cows compared with low-risk cows in lactations 1, 2, and 3 for mean daily yield were 0.34, 1.05, and 1.61 kg; likewise, accumulated 305-d yields were 103, 316, and 485 kg, respectively. The total loss was 904 kg over the first 3 lactations. Protein and fat yield losses associated with high-risk cows were significant, but primarily a feature of decreasing milk yield. Similar trends were observed for both test-day and lactation-average somatic cell count measures with higher somatic cell counts from medium- and high-risk cows compared with low-risk cows, and differences were in almost all cases significant. Likewise, mastitis incidence was significantly higher in high-risk cows compared with low-risk cows in lactations 2 and 3. Whereas the few significant differences between risk groups among fertility traits were inconsistent with no clear trend. These results are expected to be conservative, as some animals that were considered negative may become positive after the timeframe of this study, particularly if the animal was tested when relatively young. However, the magnitude of milk yield losses together with higher somatic cell counts and an increase in mastitis incidence should motivate farmers to implement the appropriate control measures to reduce the spread of the disease.     

Effect of Phosphorus Supplementation on Growth Rate,Blood Minerals,and Conception Rate of Dairy Heifers

Two trials with Holstein heifers evaluated their ability to meet phosphorus requirements from natural feedstuffs and the adequacy of minimums for phosphorus recommended by the National Research Council in 1974. Thirty-eight Holstein heifers were used in a 364-day study in Trial I and 28 heifers in a 238-day study in Trial II. Treatments were all phosphorus from natural feed-stuffs, and sufficient dicalcium phosphate to increase phosphorus .10% in dry matter of the total ration. All feeds, except pasture forage, were supplied as complete mixed rations. Supplementation of natural feedstuffs with .10% phosphorus had no significant effect on weight gains, efficiency of converting feed to gain, calcium and magnesium in blood serum, and conception rate. Animals supplemented with phorphorus in Trial II maintained higher phosphorus in blood serum than unsupplemented animals. Calcium, phosphorus, and magnesium in blood serum were within normal limits for both groups. Average daily gains were 721 and 745 g for the two groups in Trial I and 821 and 789 g in Trial II. Addition of .10% phosphorus to natural diets containing approximately .22% phosphorus had no effect on animal health or production. The minimum amounts of phosphorus suggested by the National Research Council are adequate for growing dairy heifers.