Influence of selection for milk yield on endogenous hormones and metabolites in Holstein heifers and cows

Plasma concentrations of prolactin (PRL), growth hormone (GH), insulin, glucagon, glucose, urea and free fatty acids (FFA) were measured in Holstein calves, yearlings, bred heifers and primiparous cows, either sired by bulls with high predicted differences (PD) for milk (selection group) or by bulls from an unselected random bred control population (control group; n = 6). Serial blood samples were collected before and after feeding for an 8-h period from 0900 to 1700 h. All animals were fed a complete feed at 1100 h and administered insulin (.6 IU/100 kg body weight) at 1400 h. Mean plasma PRL was greater in control animals after feeding and insulin administration, while GH was greater overall in selection cattle. Insulin remained elevated longer in selection animals after exogenous administration, and plasma glucagon was increased in the control group. While plasma glucose and urea were unaffected by genetic group, plasma FFA were elevated in selection group calves and primiparous cows compared with the control group. All hormones and metabolites differed among the pre- and post-feeding and insulin administration periods and also with age. Mean PRL and GH increased after feeding, while glucagon decreased after exogenous insulin. Plasma FFA declined after feeding, while urea and glucose were similar before and after feeding. Mean PRL increased and glucagon decreased with advancing age and plasma GH and insulin showed inverse relationships at different ages. Plasma FFA changes closely followed GH changes with age, while plasma glucose more closely followed insulin changes with age. Results indicate that all hormones measured and FFA responded to genetic selection for milk, and increases in GH are uniformly associated with increased genetic potential for milk yield.     

Effects of intracisternal bead devices on lacteal secretion components, plaque formation, and bacterial infection during the nonlactating period

Effects of placing intracisternal bead devices (ICB) into teat cisterns of 6 dairy cows, from the end of lactation through parturition, were studied. Lacteal secretion samples were collected weekly from each mammary quarter during the nonlactating period to monitor composition changes in ICB-fitted and nonfitted quarters. In quarters remaining uninfected (n = 15), there were significantly higher mean somatic cell counts (P less than 0.05), percentage of neutrophils (P less than 0.019), and cell viability (P less than 0.038), but significantly lower percentage of macrophages (P less than 0.013) in ICB-fitted quarters compared with those in nonfitted quarters. The ICB had no significant effect on mean weekly values for percentage of lymphocytes, pH, lactoferrin, citrate, citrate/lactoferrin molar ratio, serum albumin, alpha-lactalbumin, and N-acetyl-beta-D-glucosaminidase. In infected quarters (n = 9), pH of mammary secretions was significantly (P less than 0.004) higher in ICB-fitted quarters, but concentrations of lactoferrin (P less than 0.004), alpha-lactalbumin (P less than 0.013), and N-acetyl-beta-D-glucosaminidase (P less than 0.028) were significantly lower, compared with those in nonfitted quarters. Coagulase-negative staphylococci comprised approximately 90% of all infections. Over the nonlactating period, 16.4 and 41.5% of samples from nonfitted and ICB-fitted quarters, respectively, contained coagulase-negative staphylococci. Microscopic examination of ICB from uninfected quarters revealed a thin coating of plaque with adhering neutrophils, macrophages, and multinucleated giant cells. Microscopic examination of plaque on devices from ICB-fitted quarters harboring coagulase-negative staphylococci revealed numerous adherent cocci and neutrophils.     

Increased degradation of insulin-like growth factor-I in serum from feed-deprived steers

Severe feed restriction decreases serum insulin-like growth factor I (IGF-I) concentration in animals, and this decrease is thought to be due to reduced IGF-I production in the liver. The objective of this study was to determine whether feed deprivation also increases degradation of serum IGF-I and serum levels of IGF binding protein 3 (IGFBP-3) and acid-labile subunit (ALS), which inhibit IGF-I degradation and increase IGF-I retention in the blood by forming a ternary complex with IGF-I, in cattle. Five steers had free access to pasture, and another five were deprived of feed for 60 h. Serum concentration of IGF-I and liver abundance of IGF-I mRNA at the end of the 60-h period were 50% and 80% lower, respectively, in feed-deprived steers than in fed steers. Less ¹²⁵I-labeled IGF-I remained intact after a 45-h incubation in sera of feed-deprived steers than in sera of fed steers, suggesting that serum IGF-I is more quickly degraded in feed-deprived animals. Serum levels of IGFBP-3 and ALS were decreased by 40% and 30%, respectively, in feed-deprived steers compared with fed steers. These decreases were associated with more than 50% reductions in IGFBP-3 and ALS mRNA in the liver, the major source of serum IGFBP-3 and ALS. Taken together, these results suggest that feed deprivation reduces serum concentration of IGF-I in cattle not only by decreasing IGF-I gene expression in the liver, but also by increasing IGF-I degradation and reducing IGF-I retention in the blood through decreasing IGFBP-3 and ALS production in the liver.     

Pain-related cerebral potentials in response to acute painful electrical stimulation in sheep

Objective To examine associations between late event-related cerebral potential amplitudes and behavioural responses to noxious electrical stimulation as an indicator of acute pain in sheep.
Design Analysis of variance for the effects of stimulus intensity on the behaviour and event-related cerebral potential variables.
Procedure Ninety-six brief constant current electrical pulse trains were presented to the front left leg of eight sheep at four intensities (2.5 to 10 mA) in a randomised order. An event-related cerebral potential and a graded flinch response were recorded for each stimulus and the 24 event-related cerebral potentials at each intensity were averaged to produce a mean waveform. Various components of this waveform were analysed and changes in these measures and the sheep's flinch response, as stimulus intensity increased, were determined.
Results Both the flinch response and some event-related cerebral potential components, that is, peak amplitudes 114 {N1}, 187 {P1}, 318 {P2} and 230 {Pm} ms after stimulus onset, were significantly affected as stimulus intensity increased.
Conclusion These corresponding behavioural and event-related cerebral potential changes indicate the usefulness of using changes in the event-related cerebral potential to measure acute pain in sheep.     

Histological evaluation of ovine mammary tissue xenografted into cyclosporine-treated mice

Histological and pathological alterations of ovine mammary parenchyma xenografted into cyclosporine-treated mice were studied. Forty-two mature, virgin female mice were assigned randomly to one of four treatments: 1) control, 2) control + estrogen/progesterone, 3) cyclosporine, and 4) cyclosporine + estrogen/progesterone. All mice received two subcutaneous mammary tissue explants taken from an estrogen and progesterone-primed ewe. After 3, 7, 14, 21, and 35 d, mice were killed and tissue was removed for an evaluation of epithelial morphology on a scale from 1 (poor) to 5 (excellent). Leukocyte type and number were determined in subepithelial stroma. The mean epithelial score for tissue collected on d 7 and d 21 were higher (P less than .05) for cyclosporine treatments (3.0) than for controls (1.6). Scores also were greater (P less than .01) when cyclosporine was combined with estrogen and progesterone than when cyclosporine was the sole treatment (3.8 vs 2.3). Epithelial scores for tissue recovered from mice given cyclosporine and steroids up to 35 d were not different from those of explants fixed at zero time. However, scores were lower (P less than .05) for three of five time periods for explants recovered from mice given cyclosporine alone. Lymphocyte number was higher (P less than .07) in controls (66) than in mice given cyclosporine and steroids (13 per field). The correlation between lymphocyte number and epithelial score was -.55. These results indicate that ovine mammary tissue xenografted into mice treated with cyclosporine can maintain a normal histological structure for an extended period of time.     

Effects of plane of nutrition, growth hormone and unsaturated fat on mammary growth in prepubertal lambs.

Effects of plane of nutrition, growth hormone treatment and dietary polyunsaturated fat on mammary development were assessed in prepubertal ewe lambs. Ten lambs (15.6 kg initial body weight) were assigned to each of four treatment groups. Treatments included: (A) lambs given ad libitum access to a high-energy ration; (G) fed as group A but injected s.c. daily with bovine growth hormone (.08 mg/kg BW); (R) feed intake restricted to achieve a growth rate of about 120 g/d; and (S) given ad libitum access to a ration including a formaldehyde-protected sunflower seed supplement. Diets were isonitrogenous and isocaloric and were fed from about 7 to 22 wk of age. At slaughter, the udder was removed and divided into halves. One udder half was trimmed and the parenchyma was dissected from surrounding stroma for compositional analyses. Final body weight and rate of gain averaged 41.2, 42.8, 27.3 and 46.0 kg, and 251, 267, 112 and 311 g/d for groups A, G, R and S, respectively. In the same treatment order, mammary parenchymal weight averaged 15.3, 20.3, 14.2 and 25.6 g. Parenchymal dry, fat-free tissue and DNA content were 1.7, 2.5, 1.3 g and 12.6, 24.1, 10.4 and 18.8 mg, respectively. Mammary parenchymal development was stimulated by polyunsaturated fat but was not affected by plane of nutrition. Supplemental dietary lipid may promote mammogenesis in ruminants.     

Teat stimulation-induced oxytocin and catecholamine release in pregnant and lactating Holstein heifers

The effect of manual teat stimulation (milking paradigm) on release of oxytocin, epinephrine and norepinephrine was studied in (1) 15 heifers at 100, 150, 200 and 250 d of gestation and at 30 and 90 d of lactation (during machine milking) and (2) simultaneously in six heifers at less than 100 d and in six heifers at greater than 200 d of gestation. Oxytocin responses to teat stimulation, including peak heights and area under the response curves, at 150, 200 and 250 d or at greater than 200 d of gestation were similar and were significantly greater than responses at 100 d or at less than 100 d. Responses to milking were lower at 90 d compared to responses at 30 d. Catecholamines were measured only during gestation and were generally not affected by teat stimulation. Epinephrine levels were significantly higher at 200 and 250 d compared to levels at 100 and 150 d. Baseline oxytocin concentrations and responses to teat stimulation were greatest at 150 d of gestation when epinephrine levels were still low, suggesting that stimulatory mechanisms responsible for the release of oxytocin develop and/or are expressed prior to the development of inhibitory sympathetic mechanisms. For norepinephrine, linear analyses did not show significant responses to teat stimulation overall. However, elevated norepinephrine responses (greater than .2 pmol/ml) following teat stimulation were seen in 28 of 51 trials, and large oxytocin responses (greater than 75 pg/ml/min) were seen predominantly only when norepinephrine responses were low (less than = .2 pmol/ml).     

Bilateral Testicular Mixed Germ Cell-sex Cord-stromal Tumours in a Stallion

An 18-year-old Friesian stallion was examined approximately one week after reportedly presenting scrotal swelling due to torsion of the spermatic cords. Upon presentation no scrotal swelling was noted, the testes were normally oriented, and no abnormalities of the spermatic cords were noted. However, both testes were smaller than expected for a mature stallion and deep palpation revealed that the consistency of the testes was nodular. Ultrasonographic evaluation of the testes revealed diffuse heterogeneous parenchyma with multiple hypoechoic nodular areas. Grossly, the testicular parenchyma was effaced by multiple gray-tan nodules of varying consistency interspersed with gray-white bands of tissue. Microscopic analysis revealed multiple pleomorphic neoplastic foci disseminated throughout both testes. Histological and immunohistochemical features were atypical and consistent with the diagnosis of bilateral testicular mixed germ cell-sex cord stromal tumours. Bilateral testicular tumours and testicular mixed cell tumours are extremely rare in stallions and this is the first report of bilateral testicular mixed germ cell-sex cord-stromal tumours in a stallion. Our findings indicate that certain ultrasonographic characteristics are suggestive of testicular tumour and that immunohistochemistry markers can be used to better characterize testicular neoplasms in stallions.     

Distribution of thiobacillus ferrooxidans and leptospirillum ferrooxidans: implications for generation of acid mine drainage

Although Thiobacillus ferrooxidans and Leptospirillum ferrooxidans are widely considered to be the microorganisms that control the rate of generation of acid mine drainage, little is known about their natural distribution and abundance. Fluorescence in situ hybridization studies showed that at Iron Mountain, California, T. ferrooxidans occurs in peripheral slime-based communities (at pH over 1.3 and temperature under 30 degreesC) but not in important subsurface acid-forming environments (pH 0.3 to 0.7, temperature 30 degrees to 50 degreesC). Leptospirillum ferrooxidans is abundant in slimes and as a planktonic organism in environments with lower pH. Thiobacillus ferrooxidans affects the precipitation of ferric iron solids but plays a limited role in acid generation, and neither species controls direct catalysis at low pH at this site.