Effects of melengestrol acetate on the inflammatory response in heifers challenged with Mannheimia haemolytica.

Previous research from our laboratory has indicated that melengestrol acetate (MGA) added to the diet during the first 35 d after arrival in the feedlot improves growth rates and tends to reduce chronic respiratory disease in heifers naturally challenged with bovine respiratory disease. The current study was conducted to provide further insight into the possible immunomodulatory effects of MGA. Crossbred heifers (n = 48; 232 +/- 5.5 kg of BW) were used in a randomized complete block design to determine the effects of MGA on lung pathology and markers of inflammation after Mannheimia haemolytica challenge. On d 0, cattle were blocked by BW and randomly assigned, within block, to diets (54% concentrate) that provided 0 or 0.5 mg of MGA per heifer daily for the duration of the experiment. Inoculum containing from 1.3 x 10(9) to 1.7 x 10(9) cfu of M. haemolytica (20 mL) was instilled at the bifurcation of the trachea on d 14. Blood samples were collected, clinical observations were made, and rectal temperatures were recorded for each animal at 0, 12, 24, 48, 72, 96, 120, and 138 h after inoculation. Heifers fed MGA had greater circulating concentrations of eosinophils and postchallenge concentrations of segmented neutrophils and white blood cells (P < 0.01) than controls, as well as elevated plasma protein, serum haptoglobin, and fibrinogen after M. haemolytica challenge (P < 0.01). Heifers fed MGA had lower plasma glucose (P < 0.01), greater plasma urea N (P = 0.02), and elevated respiratory indices (P < 0.01) compared with controls. Necropsies performed on d 6 after inoculation suggested that M. haemolytica challenge was relatively mild, because lesions were confined to a small portion of the lungs. On a 0 to 100 scale, average lung lesion scores were 3 and 1 for MGA-fed and control groups, respectively (P < 0.06). Heifers fed MGA before mild M. haemolytica challenge were more susceptible to infection, as evidenced by a greater number of heifers fed MGA exhibiting pulmonary lesions 138 h after inoculation than controls (14 out of 23 vs. 6 out of 24 for MGA and controls, respectively; P < 0.02).

Relationship between mean body surface temperature measured by use of infrared thermography and ambient temperature in clinically normal pigs and pigs inoculated with Actinobacillus pleuropneumoniae.

OBJECTIVE: To determine the relationship between ambient temperature and mean body surface temperature (MBST) measured by use of infrared thermography (IRT) and to evaluate the ability of IRT to detect febrile responses in pigs following inoculation with Actinobacillus pleuropneumoniae. ANIMALS: 28 crossbred barrows. PROCEDURES: Pigs (n = 4) were subjected to ambient temperatures ranging from 10 to 32 C in an environmental chamber. Infrared thermographs were obtained, and regression analysis was used to determine the relationship between ambient temperature and MBST. The remaining pigs were assigned to groups in an unbalanced randomized complete block design (6 A pleuropneumoniae-inoculated febrile pigs [increase in rectal temperature > or = 1.67 C], 6 A pleuropneumoniae-inoculated nonfebrile pigs [increase in rectal temperature < 1.67 C], and 12 noninoculated pigs). Infrared thermographs and rectal temperatures were obtained for the period from 2 hours before to 18 hours after inoculation, and results were analyzed by use of repeated-measures ANOVA. RESULTS: A significant linear relationship was observed between ambient temperature and MBST (slope, 0.40 C). For inoculated febrile pigs, a treatment X method interaction was evident for rectal temperature and MBST, whereas inoculated nonfebrile pigs only had increased rectal temperatures, compared with noninoculated pigs. A method X time interaction resulted from the longer interval after inoculation until detection of an increase in MBST by use of IRT. CONCLUSIONS AND CLINICAL RELEVANCE: Infrared thermography can be adjusted to account for ambient temperature and used to detect changes in MBST and radiant heat production attributable to a febrile response in pigs.

Use of infrared thermography to detect inflammation caused by contaminated growth promotant ear implants in cattle.

OBJECTIVE: To compare the infrared thermographic appearance of bovine ears that had received contaminated growth promotant implants with ears that had received clean implants and ears without implants. DESIGN: Prospective study. ANIMALS: 32 yearling crossbred beef steers with a mean weight of 322 kg (708 lbs). PROCEDURE: Contaminated (n = 16) and clean (16) implants were placed in the ears of feedlot cattle. Nonimplanted (n = 32) ears served as a within-animal control for thermographic comparisons. Images of rostral and caudal surfaces were obtained during a 21-day period, using an infrared thermal imaging radiometer. Repeated measures ANOVA was used to determine the relationship between mean temperature in a zone on the rostral surface of the ear and at 3 locations (proximal, middle, distal) on the caudal surface of the ear (response variables) with treatment (ears with contaminated implants or clean implants vs control ears with no implants), time (repeated day of measurement), and interactions among these variables. RESULTS: Significant temperature differences existed between ears with contaminated implants and control ears. Temperatures for ears with clean implants were significantly higher than control ears on day 2. At low ambient temperatures when the ears became wet, a greater temperature contrast was detected between ears with contaminated implants and control ears. CONCLUSIONS AND CLINICAL RELEVANCE: Thermal imaging of the ears of feedlot cattle is a noninvasive diagnostic tool that can be used to identify cattle with abscesses caused by contaminated growth-promotant implants.

Effect of source of cattle and distance transported to a commercial slaughter facility on carcass bruises in mature beef cows.

OBJECTIVE: To determine the effect of source of cattle and distance cattle were transported to a commercial slaughter facility on prevalence and severity of carcass bruises in mature beef cows. DESIGN: Epidemiologic investigation. SAMPLE POPULATION: Carcasses from 3,955 beef cows from 11 states assembled in 89 procurement lots. PROCEDURE: Each carcass was scored for bruise severity and location. Source of cattle was categorized. Distance from source to slaughter facility was determined. An ANCOVA was used to determine effects of variables on carcass bruises. RESULTS: Mature beef cows marketed through livestock auctions conducting first-point testing for brucellosis, especially when transported longer distances (> 325 km) to slaughter facilities, had a greater number and severity of carcass bruises than cows originating from ranches or livestock auctions not conducting first-point testing. There was an increase in number of rib bruises in cows originating from livestock auctions not conducting first-point testing. Prevalence and severity of bruises were not significantly affected by transportation distance between cows originating from auctions not conducting first-point testing and cows originating from ranches. CLINICAL IMPLICATIONS: A strong association existed between handling for brucellosis testing prior to sale for slaughter and distance transported to slaughter facility with carcass bruises in mature beef cows. Bruises are major quality defects that decrease carcass value and slaughter-cow prices. Repeated handling and restraint as well as long-distance transport are issues to consider regarding the responsibility of the livestock industry to provide for the safety and well-being of cattle sold for slaughter.

Effect of treatment with ivermectin on reproductive performance of yearling beef heifers.

To determine the effect of treatment with ivermectin on reproductive parameters, 78 fall-born, yearling heifers were allotted to either an ivermectin treatment group or to the control, non-treatment group. The heifers were treated in June and October when they were approximately 7 and 11 mo old, respectively. Ivermectin effectively lowered fecal egg counts in the treated heifers compared with that of the controls. In heifers that were maintained on a marginal plane of nutrition, treatment with ivermectin not only improved weight gains during each recording period but also hastened the onset of puberty and improved the pregnancy rate during a 60-d breeding season. The positive effect of ivermectin on these reproductive characteristics could not be explained by increased weight gain alone, because the correlation between weight gain and puberty was not significant. Treatment with ivermectin positively affected pelvic area but not uterine score when compared with those of the controls.

Inflammatory response to clostridial vaccines in feedlot cattle.

In 24 individually housed feedlot steers that weighed 275 kg, clostridial vaccines were compared for size of injection site reactions, systemic inflammatory response caused by vaccination, and impact on feed consumption. Vaccines were a bacterin/toxoid containing antigens from multiple clostridial species (7-way), and a Clostridium perfringens type C and D toxoid; sterile physiologic saline solution was used as the control. Injection site reactions were observed in all vaccinated cattle. Differences in size of lesions were found, with cattle given the 7-way vaccine (7-way group) having the largest lesions. The inflammatory-response to vaccination, measured by serum concentration of the acute-phase protein haptoglobin, was significantly (P < 0.05) increased in both vaccinated groups over that of controls. However, the 7-way group had higher postinjection values than did the group given type C and D toxoid. The 7-way group had a significant (P < 0.05) 20% decrease in feed consumption in response to the second injection of vaccine. These findings are indicative of potential negative effects of multiple clostridial vaccinations.

Atlanto-occipital fusion in two polled Hereford calves.

Two cases of atlanto-occipital fusion were diagnosed in Polled Hereford calves. The cause, genetic or environmental, of this abnormality could not be determined. Since relatively minor traumatic forces during birth can cause severe injury in the head region, atlanto-occipital fusion should be ruled out in calves dying acutely after assisted parturition.

Evaluation of reproductive traits in Bos taurus and Bos indicus crossbred heifers: effects of postweaning energy manipulation.

Reproductive traits were evaluated in Bos taurus and Bos indicus crossbred heifers that were fed different diets during the postweaning period. The study was designed in a 2 x 2 x 2 factorial arrangement of treatments. Angus x Hereford (AH; n = 148) and Brahman x Hereford (BH; n = 148) heifers were sorted after weaning by body weight into light (LW) and heavy (HW) weight blocks. Heifers in each weight block were assigned to diets calculated to reach a target weight of 55% (LE) or 65% (HE) of their projected mature weights by the start of the breeding season. Puberty was determined after a 160-d observation period and characterized by the following criteria: 1) behavioral estrus, 2) presence of a palpable corpus luteum (d 6 to 10; estrus = d 0), and 3) rise in serum progesterone above 1 ng/ml (d 6 to 10). A higher (P = .01) proportion of AH heifers than of BH heifers reached puberty by the breeding season (93% vs 67%). Interactions of breed x weight block and energy level x weight block also contributed to this difference. Weight at puberty was heavier (P = .001) among HE than among LE heifers and greater for heifers in HW than for those in LW blocks (P = .02). Differences in prebreeding weight, body condition, average daily gain, hip height, and pelvic area were influenced selectively by breed, energy level, or weight block. Pregnancy rates were higher (P = .01) among AH than among BH heifers. Incidence and severity of dystocia was influenced by the breed x energy level interaction (P = .01). Brahman x Hereford heifers had less (P = .01) dystocia than AH heifers, HE heifers had less (P less than .02) dystocia than LE heifers, and HE-AH heifers had less (P less than .01) dystocia than LE-AH contemporaries. Subsequent duration of the postpartum interval to estrus was shorter (P = .002) among AH than among BH females. Pregnancy rates at the end of the 2nd yr were higher (P = .02) among LW than among HW females and weights were heavier (P = .001) at weaning among calves weaned from BH dams.

Influence of prepartum exposure of beef heifers to winter weather on concentrations of plasma energy-yielding substrates, serum hormones and birth weight of calves.

The influence of exposure to ambient winter weather conditions (WW) during the final 90 d of gestation on serum hormones, plasma substrates, and birth weight of calves was evaluated in spring-calving, primiparous beef heifers. At of 192+/-14 d of gestation, heifers were assigned by expected calving date, breed, and sire of fetus to one of two treatments. Thirteen heifers were assigned to thermoneutral environment (TN; 12 degrees C) and housed in temperature-controlled rooms. Heifers in WW (n=16) were maintained outdoors in drylots without access to shelter and given additional dietary energy when average weekly windchill fell below -6.7 degrees C. Body weights, hip-heights and samples of serum and plasma were obtained biweekly until heifers were relocated, approximately 7 d prior to expected calving. Polynomial response curves for concentrations of glucose and nonesterified fatty acids (NEFA) in plasma and cortisol in serum were not influenced by treatment. However, average concentrations of NEFA in plasma were increased (P<0.02) and glucose tended to be higher (P=0.13) in WW heifers compared to TN heifers (172.5+/-8.9 vs 136.9+/-7.7 micromol/L and 87.8+/-2.4 vs 83.3+/-2.7 mg/100ml for NEFA and glucose, respectively). Time trends of concentrations of estradiol in serum (P<0.01) and hip-height to weight ratios were different (P<0.05) for WW and TN. Birth weights of calves from TN heifers were greater (P<0.06) than calves from WW heifers (42.3+/-2.0 vs 36.9+/-1.8 kg), but average calving difficulty scores were similar for both heifer groups (3.2+/-0.5 vs 2.7+/-0.4). These data suggest that exposing spring-calving cows to reduced effective ambient temperatures during the final 90 d of pregnancy may elevate energy-yielding metabolites in plasma and alter endocrine function. These changes may contribute to reduced birth weight of calves.

Evaluation of cryopreservation techniques for bovine embryos.

A total of 228 embryos was nonsurgically collected from superovulated cows and dehydrated in dimethyl sulfoxide (DMSO) or glycerol by a three-step procedure or a (T.I.T.) timed interval titration procedure. Embryos were loaded in straws, frozen by cooling to -6.0 degrees C at 1.0 degrees C/min, and seeded, followed by cooling to -30 degrees C at 0.3 degrees C/min and to -38 degrees C at 0.1 degrees C/min. At this time the straws were plunged into liquid nitrogen at -195 degrees C. Embryos were thawed in a 27 degrees C or 37 degrees C water bath and rehydrated by a six-step, three-step (sucrose) or one-step (sucrose) procedure. This yielded a 2 x 2 x 2 x 3 factorial treatment structure. Survival was based on development after 12 h in in vitro culture. The only significant single factor affecting survival was the initial quality grade of the embryo. Grades 1 and 2 embryos survived more often than Grade 3 embryos (P < 0.05). Using DMSO as the cryoprotectant resulted in better scores for the post dehydration to post thawing interval (P = 0.02). For both intervals, post dehydration to post thawing and post thawing to post rehydration, the previous quality grade was significant in determining the subsequent quality grade (P < 0.01). At each step of the freeze-thaw process, the embryos became progressively less morphologically intact.

Managing reduced-fertility beef herds.

Many beef herds with less than ideal reproductive efficiency have an 85-90% pregnancy rate, a breeding season longer than 90 days, and less than 60% of the calf crop born in the first 21 days of the calving season. The previous years' fertility levels should be used as a guideline for estimating calf losses and assessing improvement after implementation of reproductive programs. Acute infectious causes of reproductive inefficiency tend to be expressed as abortion or delayed conception. Management-related reproductive problems are common and involve inadequacies in nutrition, replacement heifer development, bull fertility and cow culling.

Influence of the ovary on estradiol-induced luteinizing hormone release in postpartum milked and suckled Holstein cows.

Holstein cows were assigned at parturition to be milked (n = 10) or suckled by four calves each (n = 10). One-half of each group was ovariectomized bilaterally (ovex) at the end of wk 1 and the remaining one-half was ovariectomized unilaterally (intact) at the end of wk 2. Cows were challenged with 400 micrograms estradiol-17 beta (im) at the end of wk 1, 2, 3 and 4 (24 h after surgery) and blood was collected at 0, 12, 14, 16, 18, 20, 22, 24 and 26 h after estradiol to determine luteinizing hormone (LH) concentration. Blood also was collected every 3 d until 6 wk to estimate ovulation in intact cows by monitoring serum progesterone concentration. Calves were weaned from suckled cows after the third blood collection period (wk 3). Total ovarian follicles (16.5 +/- 4 vs 34.2 +/- 4) and follicular fluid weight (.7 +/- .2 vs 1.4 +/- .2 g) were less (P less than .05) in suckled than in milked cows during wk 1, respectively. But the reverse trend appeared to occur during wk 2, although total ovarian follicles (26.4 +/- 6 vs 16.4 +/- 6) and follicular fluid weight (.9 +/- .3 vs .8 +/- .3 g) were similar in suckled and milked cows, respectively. Fewer suckled than milked cows responded to estradiol (LH concentration 1 SD above the average pre-estradiol LH concentration) at the end of wk 1 and 2 (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for ovulation and fertilization in beef cows with short estrous cycles.

Calves were weaned from 15 Polled hereford anestrous cows 25 to 42 days after calving. In eight cows the uterus was flushed on day 6 or 8 after the first postweaning estrus (day 0), and in seven cows the oviduct ipsilateral to the ovary containing an ovulation papilla was removed and flushed on day 3. One ovum (morula) was recovered from the eight uterine flushings, while six ova were recovered from six of the seven oviductal flushings. Of the six, three were fertilized (4 to 8 cells), two unfertilized and only the broken zona pellucida of one was recovered. An ovulation papilla was observed in all cows at the time of oviduct removal. Six of the 15 cows had cycles less than 12 days, and from four of those six fertilized ova were recovered. The data indicate that previously anestrous cows ovulate at their first postweaning estrus and the ova released are capable of being fertilized. Failure to maintain pregnancy appears to be due to early corpus luteum regression.