Correlations between mean echogenicity and material properties of normal and diseased equine superficial digital flexor tendons: an in vitro segmental approach.

The objective of this study was to test the hypothesis that tendon echogenicity is associated with the material properties of the corresponding tendon site, especially in case of lesions, due to local changes in tendon matrix composition. Four normal and nine spontaneously injured equine superficial digital flexor tendons (SDFT) were isolated then ultrasonographically examined under tension, in a special device placed in a water bath. Ultrasonographic transversal images (7.5MHz linear transducer) of five segments along each tendon were digitized, and analyzed in order to measure the mean cross-sectional area (MCSA) and mean echogenicity (ME) of each segment. The tendons were then tested in traction until rupture in a testing machine. For each segment, stress and strain were determined throughout the test, and the elastic modulus (EM) was evaluated. The tendon lesions were also documented by histology. No correlation was found between ME and the material properties of normal tendon segments. At the rupture sites of the nine diseased tendons, ME was positively correlated with maximal stress and EM, whereas no correlation was demonstrated with maximal strain. Besides, a positive correlation was demonstrated between ME and both MCSA and EM, when the three metacarpal segments of the diseased tendons were considered. Although ME gives only rough information about tendon matrix structure, it does show, under these in vitro conditions, significant correlations with material properties of pathological tendon segments, which may improve the functional significance and therefore the prognostic value of the ultrasonographic examination of tendon lesions.

Effects of heel and toe elevation upon the digital joint angles in the standing horse.

Five sound mature horses, age 8-14 years, with toe angles 45.5-55.0 degrees were placed on a specially designed platform with only the left forelimb weightbearing, which allowed the successive production of 7 different conditions of foot orientation: neutral position (N), 5, 10, 15 degrees heel (H5, H10, H15) and toe (T5, T10, T15) elevation, performed according to 2 different sequences. For each condition, 2 lateromedial radiographs were taken to evaluate the metacarpophalangeal joint (MPJ) and both interphalangeal joint (PIPJ and DIPJ) angles, respectively. In addition, two-dimensional (2-D) kinematic recordings, using reflective skin markers placed laterally on the left forelimb joints, were performed. The value of each joint angle (JA) and its angular variation to N (AV) were considered for statistical analysis. For all JA and their AV determined radiographically, the condition effect was significant and the sequence did not influence the differences between conditions. The relationships between the JA and the conditions (in the sequence: T15, T10, T5, N, H5, H10, H15) were overall linear for the 3 joints. The maximal range T15-H15 was mean +/- s.d. 6.9 +/- 2.0 degrees for MPJ (dorsal angle decrease), 7.3 +/- 1.0 degrees and 29.5 +/- 1.8 degrees for PIPJ and DIPJ (palmar angle decrease), respectively. Contrary to JA and in spite of large variations in hoof conformation, AV did not show any significant horse effect. Wide differences were observed between the digital JA measured radiographically and from kinematics, which could be related to cutaneous displacement. Heel elevation induced elbow flexion, whereas a slight extension was observed with toe elevation. These movements, even slight (mean elbow angle amplitude: 3.6 +/- 1.3 degrees), may have consequences upon flexor tendon tension.

Periodic fluctuations of gut regulatory peptides in phase with the duodenal migrating myoelectric complex in preruminant calves: effect of different sources of dietary protein.

Four preruminant calves with implanted electrodes in the duodenum and a catheter in the external jugular vein were used for investigation of plasma gut regulatory peptide profiles during different phases of migrating myoelectric complex (MMC) in the small intestine. The effects of different dietary proteins on the rhythmic activity of gut peptides and gastrointestinal motility were compared. In particular, the effects of skimmed-milk protein (retaining physiological patterns of abomasal clotting, and abomaso-intestinal digesta flow) v. fish protein (devoid of clotting activity and modifying the digesta flow) were studied. In calves fed on the milk diet, plasma concentrations of pancreatic polypeptide, motilin, secretin, cholecystokinin (CCK) and somatostatin, but not vasoactive intestinal polypeptide or gastrin, fluctuated in phase with the duodenal MMC in the preprandial period. Feeding transiently affected the intestinal MMC and abolished the peptide fluctuations in a specimen-specific manner. In contrast, calves fed on the fish-protein diet showed more profound changes in intestinal MMC. In these animals the MMC-related fluctuations were significant only for plasma CCK. In conclusion, the source of dietary protein has an impact on the physiological endocrine function of the small intestine. Observed fluctuations of plasma gut regulatory peptides seem to be secondary to duodenal motility cycles.

Comparative study of forestomach digestion in llamas and sheep.

To compare digestion in the forestomach of llamas and sheep, the animals were fed four different diets: hay alone (H), low in nitrogen; the same hay with soybean meal (HS), with barley (HB) and with both soybean meal and barley (HSB). The sheep intakes were restricted to obtain about the same intake level in the two species. On average, the digestibilities of DM, OM and NDF were significantly higher in llamas: respectively, +2.7, 3.6 and 5.3 for the four diets. Added barley impaired hay digestion in the sheep, but very little in the llamas. The llamas retained nitrogen better than the sheep owing to very low urine losses. For hay alone, the retention time of digesta in the forestomach was higher in the llamas than in the sheep. In contrast, there was no difference between species for the other diets. The pH and ammonia levels were higher in llamas. In contrast, the SCFA levels were lower. In all cases the in-situ rate of digestion was greater in llamas. The low intake of llamas generally observed in the literature does not account for their better digestion. The stability of the two first compartment pH levels and an excellent cellulolytic activity are determining factors in the better digestion efficiency of plant cell walls in the llamas. However, higher NH3 levels were observed in llamas, although the urinary N excretion was lower.

Physical characteristics of reticular content in the bovine and consequences on reticular outflow.

Reticular content was sampled in cows before and 2 and 5 hours after they were fed various forages. Dry matter, particle size distribution, pH, osmotic pressure and viscosity of the liquid phase were measured. Consistency was also evaluated using purpose-built apparatus. The contents were fractionated by vertical distribution under gravity and by intermittent flow through an orifice into fractions containing different particle concentrations, to model reticular retention of large particles in rumen outflow. Retention occurs as a result of a combination of flotation carrying large particles back into the rumen, and filtration which prevents them leaving it. These processes are particularly effective after feeding, and with poor hay, and so help prolong fermentation time. The consistency of reticular content is relatively stable; it may be autoregulated by adjustment of feeding parameters in response to sensory receptor signals.

Systemic bone growth factors concentrations in calves during the perinatal period.

Plasma somatostatin (SRIF), growth hormone (GH), somatomedin C (IGF1), osteocalcin (BGP), 1,25-dihydroxyvitamin D (1,25-(OH)2D), calcium and inorganic phosphorus were measured in 10 chronically-catheterized fetal calves and in their dams during the two last months of gestation. Thus fetal life is associated with high levels of GH (1.53 +/- 0.14 nmol.l-1), BGP (64 +/- 4 nmol), Ca (2.90 +/- 0.06 nmol.l-1) compared to the results obtained in the pregnant cows. The first week of postnatal life was associated with a tremendous increase in plasma SRIF concentration (from 36 +/- 5 to 106 +/- 15 pmol.l-1; P less than 0.01). These results agree with an intense bone growth during the end of fetal life in the bovine species. However, IG 1 might not play a major role in the regulation of fetal skeletal growth during this period.

[Retention of large-size particles in the reticulum of the cow]. / Sur la rétention des particules de grande taille dans le réticulum chez la vache.

To explain the retention of large particles in the reticulum, in vitro sedimentation, sorting of particles by gas production and flow of contents through a hole simulating the reticulo-omasal orifice (ROO) were examined. Removal of large particles from the floor of the reticulum by gas production and a sieving mechanism through the ROO are discussed.

Regulation of growth hormone release in fetal calves.

Plasma GH and IGF1 concentrations were measured during the last 2 months of gestation in 9 chronically catheterized fetal calves under basal conditions or following growth-hormone-releasing factor (GRF), thyrotropin-releasing hormone (TRH) or SRIF intravenous cotyledonnary injections. Plasma GH concentrations were higher in fetuses (1.40 +/- 0.10 nmol/l) than in dams (0.14 +/- 0.01 nmol/l). Plasma GH secretory profile was pulsatile. The number of secretory pulses, as well as their magnitude and mean baseline values decreased from 220 to 270 days of gestation. Synthetic 1-29 GRF or TRH increased fetal plasma GH concentration at 250 and 270 days of gestation but was devoid of any significant effect at 220 days. SRIF injection decreased plasma GH concentration in 270-day-old fetuses. Plasma IGF1 concentrations were lower in fetuses than in dams. No treatment had a significant effect on fetal and maternal IGF1 levels.

Measurement of gastric emptying rate.

Gastric emptying rate was measured chronically using an electromagnetic probe inserted into the proximal duodenum via a duodenal cannula. Each duodenal gush was identified and its value calculated on the basis of pre-established threshold and timing criteria which eliminate shifts in the baseline and artefacts due to the presence of particles. The net flow of digestive contents and the aboral cumulative flow were displayed online. This system has been used in sheep for continuous measurement of duodenal flow over periods of 3-5 weeks.

Development of digestive functions in the newborn ruminant.

To assess the progress of developing digestive functions accurately, it is necessary to evaluate the relative changes of certain variables. Observations have been reported on anatomical, biochemical and physiological changes that occur during the digestive adaptation of the neonatal lamb or calf to the extra-uterine life. For example, chymosin, a milk-clotting acid protease, is maintained by the milk diet at a high level until weaning in calves, as a result of the stimulation by casein of the rate of chymosin synthesis.

Energy metabolism and thermoregulation in the newborn calf.

About half of calf losses occur during the first two days of life. Mortality rate is increased by difficult parturition and adverse climatic conditions. However, thermoregulatory mechanisms are operative at birth, these including the metabolism of brown adipose tissue, shivering and physical activity. Thermoregulation is just as effective in twin as in single calves provided that calving conditions are good. Heat production of Charolais and Salers calves was lower than that of Friesian; the difference came from a lower basal metabolic rate rather from a better thermic insulation. In dystocial calves, blood pH at birth was very low, lactataemia was two or three times higher than in eutocial calves, mobilization of body lipids was reduced and plasma thyroïd hormone level were low, which can explain the lower heat production and the drop in rectal temperature. The physiological responses of calves born by caesarean parturition depend on the delay incurred during surgical removal.

Thyroxine, triiodothyronine and iodide in different breeds of newborn calves.

Plasma thyroxine (T4), triiodothyronine (T3) and iodide levels were measured from birth until 30 days of age in 17 Holstein x Friesian (HF), 7 Salers and 7 Charolais calves born at term. The response of plasma T4 and T3 levels to bovine thyrotropin (TSH) injection was also compared in two groups of 9 HF calves 3hrs and 21 days, respectively, after birth. In the HF calves, plasma T4 and T3 levels increased from birth to 6 hrs (when the rectal temperature of these calves decreased slightly), then diminished until day 7 and remained stable until 30 days of age. In Salers calves, changes in the plasma T4 and T3 levels were not different from those observed in HF animals. However, in Charolais calves, there was no significant increase in plasma T4 and T3 levels after birth. Twelve and 24 hrs after birth, the plasma iodothyronine levels measured in these animals were lower than in HF calves. In Salers and Charolais calves a positive linear relationship was demonstrated between plasma T4 (or T3) levels at birth and the birth weight. In the three groups of calves, plasma iodide levels decreased from birth until 10 days of age, then remained stable until the end of the first neonatal month. Intravenous injection of the same dose of bovine TSH (5 mU/kg of body weight) induced a rise in the plasma T4 and T3 levels which was significantly more intense in 21-day old calves than in 3-hr old calves.

Plasma levels of vitamin D metabolites in the bovine species during the perinatal period.

Plasma vitamin D metabolites (25-OH D; 24,25-(OH)2D and 1,25-(OH)2D) were measured simultaneously in the blood plasma samples of young cows and their calves. Four of the calves were chronically catheterized in utero at least 2 weeks before the expected time of parturition. No significant hypocalcaemia occurred in the dams at calving. Plasma vitamin D metabolites showed no significant variations for 2 weeks before and 4 days after calving. But rapid changes in plasma 1,25-(OH)2D concentrations were observed in one calf during the first 48 postnatal hours. Before birth, the maternal and foetal concentrations of either 1,25-(OH)2D or 24,25-(OH)2D were positively correlated. 25-(OH) D (13 ng/ml), 24,25-(OH)2D (1 ng/ml) and 1,25-(OH)2D (76 pg/ml) were detected in one foetal plasma collected 35 days before term.