Relation of growth hormone response to growth hormone-releasing hormone to estimation of milk production via deuterium oxide dilution in beef cattle

Current methods of estimating milk production in beef cows can be time-consuming, labor-intensive, and subject to high variability. The weigh-suckle-weigh (WSW) method requires repeated separation of offspring from their dams. Machine milking requires that animals be acclimated to the equipment prior to the estimation. The objective of Exp. 1 was to validate a deuterium oxide (D2O) dilution method of estimating milk production in cattle. In Exp. 1, Holstein calves (n = 5) averaging 29+/-2 d of age and 52.6+/-2.5 kg (+/- SE) were used as the model. Blood was collected for baseline D2O measurements followed by an injection of 300 mg D2O/kg BW. Syringes were weighed before and after the injection to gravimetrically determine the dose. Another blood sample was collected after D2O was allowed to equilibrate with body water for 2 h, and on each of the next five consecutive days, prior to feeding. Actual milk intake was measured by disappearance (i.e., amount of milk replacer offered to the calf minus the amount refused). Deuterium oxide in plasma was measured by mass spectrometry and milk intake was computed from the disappearance curve of D2O in blood plasma for each calf. Accumulated milk intake estimated by D2O dilution was highly correlated (y = 0.9x + 0.6; R2 = 0.99; P < 0.001) with actual milk intake. The objectives of Exp. 2 were to determine whether 1) D2O dilution was comparable to a standard measure of milk production in beef heifers and 2) growth hormone (GH) response to GH-releasing hormone (GHRH) in heifers at weaning is predictive of subsequent milk production. Deuterium oxide dilution and WSW were compared using 14 first-calf Angus heifers and their calves. Deuterium oxide dilution was used to estimate milk production of 40 first-calf Angus heifers that had been challenged with GHRH at weaning. Results indicate that the D2O dilution method is correlated (R2 = 0.89; P = 0.04) to the WSW estimation of milk production. Growth hormone response to GHRH in weanling heifers is positively related (R2 = 0.22; P = 0.03) to their subsequent milk production. Deuterium oxide dilution in calves offers an additional approach to the estimation of milk production of the dam in typical beef cattle production settings.     

Severity and persistence of footrot in Merino sheep experimentally infected with a protease thermostable strain of Dichelobacter nodosus at five sites

Objective To test the hypothesis that ovine footrot associated with a thermostable protease strain of Dichelobacter nodosus undergoes self cure or is sustained as an annually recurring disease, depending on the environment.
Design and procedure Forty Merino sheep from a single blood line were infected with a protease thermostable strain of D nodosus a t each of five sites in Western Australia. Footrot lesions and microscopic evidence of D nodosus were recorded every fortnight for 2.5 years, supplemented by laboratory culture. Rainfall, soil and air temperature, pasture quantity and composition and soil types were also recorded. Flocks that apparently self cured were relocated to a more favourable site for footrot in the final spring season.
Results The maximum prevalence of feet with clinical footrot lesions was 80.6, 1.3, 14.4, 3.8 and 88.1% at the five sites. Severe footrot occurred for three consecutive spring seasons at one site that had clay loam soil and at least 3500 kg/ha total pasture dry matter annually. However, the infection was asymptomatic for up to 10 weeks between outbreaks. D nodosus was isolated from flocks for 2.5 years at only two sites, although there was microscopic evidence of the organism at other sites in the final year. A thermolabile variant (strain U6) of D nodosus was isolated from the two sites where footrot persisted.
Conclusion Depending on time and location, ovine footrot induced by a protease thermostable strain of D nodosus either self cured or persisted as annual outbreaks interspersed with periods of asymptomatic infection.     

Acute cortisol responses of calves to four methods of dehorning by amputation

Objective To measure the plasma cortisol response in calves dehorned by four different methods (scoop, guillotine shears, saw, embryotomy wire) for 9 h after dehorning.
Design A physiological study with controls.
Procedure Horn amputation was carried out on calves restrained manually in a race.
Results The four methods of dehorning provoked similarly increased cortisol responses which lasted for 6 h. During the first hour after dehorning the plasma cortisol concentrations were similar to those following ACTH injection. The overall cortisol response to control handling was about 30% of the responses to dehorning.
Conclusions The similarity of the cortisol responses produced by the four methods of dehorning suggests that the distress experienced by calves following dehorning by amputation is similar regardless of method used.     

Clinical evaluation of protein electrophoresis of cerebral spinal fluid

Protein fractions of cerebral spinal fluid samples were analyzed in an effort to find a reliable, minimally invasive and cost effective method of diagnosing cervical vertebral myelopathy. There were six separate protein fractions analyzed by electrophoresis. In this study we specifically looked for a post beta spike in horses with spinal cord compression. There was no correlation in our study between horses with a post beta spike and CVM as diagnosed by a myelogram.     

Compositional analysis of nonfat dry milk by using near infrared diffuse reflectance spectroscopy

Proximate data from 82 nonfat dry milk (NFDM) samples were correlated with near infrared reflectance (NIR) measurements. The best wavelengths for determining constituent concentrations were chosen from 19 preselected filters by using linear regression analysis. The correlation coefficient (r) was 0.971 and the standard error of prediction (SEP) was 0.274 when the predicted values (from NIR measurements) using the 3 wavelengths selected for determining moisture content were compared with laboratory values; r and SEP were 0.961 and 0.099, respectively, when the predicted values using the 4 wavelengths selected for fat content were compared with laboratory results; 0.887 and 0.594, respectively, using the 4 wavelengths selected for lactose content; 0.905 and 0.438 using the 8 wavelengths selected for protein (micro-Kjeldahl) content; and 0.911 and 0.509 using the 7 wavelengths selected for protein (dye binding). These data indicate that NIR can be used to estimate moisture, fat, lactose, and protein content of NFDM.     

Effect of Insemination–Ovulation Interval and Addition of Seminal Plasma on Sow Fertility to Insemination of Cryopreserved Sperm

In swine, the use of frozen-thawed (FT) sperm for artificial insemination (AI) is limited because of poor sow fertility, possibly associated with a post-thaw capacitation-like status resulting in fewer fully viable sperm. Sow fertility to AI with FT sperm may improve with deeper deposition of sperm within the female tract, insemination very close to ovulation, or reversal of cryocapacitation by seminal plasma (SP). We performed two experiments to examine these suggestions. In experiment 1, 122 multiparous Yorkshire sows received 600 IU equine chorionic gonadotrophin at weaning and 5 mg pLH 80 h later to control time of ovulation. The predicted time of ovulation (PTO) was 38 h after pLH injection. Thereafter, sows were assigned on the basis of parity to a single AI of FT sperm at 2 h before PTO, or at 12 h before PTO, or FT sperm supplemented with 10% SP at 12 h before PTO. Control sows received fresh semen at 12 h before PTO. All semen doses were adjusted to 3 x 10(9) live cells and deposited into the cervix. Experiment 2 employed 99 multiparous crossbred sows and repeated the treatments of experiment 1 except that all FT inseminations were intrauterine. In both experiments, farrowing rates were lower (p < 0.01) following FT inseminations with no effect of time of insemination or of supplemental SP. In experiment 1, litter size was smaller following FT insemination (p < 0.05), but no effect on litter size was evident in experiment 2. Supplemental SP had no effect on litter size in either experiment. The lack of effect of either SP or timing of FT insemination on sow fertility suggests that the non-lethal sperm cryoinjury affecting fertility involves more than just cryocapacitation.     

Effect of breed of cattle on innate resistance to infection with <i>Babesia bovis, B bigemina and Anaplasma marginale

Objective To assess the innate resistance of naive Bos taurus, Bos taurus cross Bos indicus and Bos indicus cattle to virulent Babesia bovis, B bigemina and Anaplasma marginale parasites. Design Groups of 10, pure B indicus, fi B indicus cross,/B indicus cross and pure B taurus steers were infected with virulent B bovis, B bigemina and A marginale parasites. Procedure Sequential infections were carried out by intravenous inoculation of infected blood containing 1 times 10⁸ parasites of B bovis, followed by B bigemina and then A marginale. To assess resistance, measurements were made of parasitaemia, rectal temperature, packed cell volume and the number within a group requiring chemotherapy to control infection. There was a recovery period between each infection. Results Infection with B bovis showed that pure B indicus steers were significantly more resistant to B bovis infection than the other groups, with none of this group requiring treatment. There was no significant difference between fi B indicus cross and/B indicus cross with 30% and 20%, respectively, of steers in these groups requiring treatment. The pure B taurus steers were significantly more affected then those in the other three groups with 80% requiring treatment. Infections of B bigemina produced a mild response in comparison to that of B bovis and none of the steers required treatment. However, the pure B taurus group was significantly more affected than the other three groups for all other measurements. After the A marginale infection, B indicus steers were moderately affected with 50% requiring treatment, whereas 70% of the fi B indicus group, 80% of the /B indicus cross group and 100% of the pure B taurus group required treatment. Conclusions All breeds of cattle, ranging from pure B indicus to pure B taurus may be at risk of severe disease if exposed to virulent A marginale. The results confirm that pure B indicus cattle are relatively resistant to B bovis, but there could be a significant risk of severe mortalities if cross-bred herds are exposed to virulent infection.     

Diplococcus pneumonia Type 16 in Laboratory Rats

An acute respiratory disease in a colony of Wistar-derived rats is described. The infection, due to Diplococcus pneumoniae type 16, has apparently not been described previously in the rat. Rigid sanitary measures and treatment with penicillin were effective in controlling the disease.