Normal Lamb Research Articles

Utilization of wheat stubble pastures by gestating ewes

A 4-month field trial was conducted with 48 mature Sardi ewes on the effects of stocking rate and supplementation on wheat stubble availability, biomass, chemical composition, dry matter (DM) intake and diet quality, and to test the effectiveness of supplementation in late gestation on ewes and lamb live weights (LW). Animals on treatments A (12 ewes ha −1) and B (24 ewes ha −1) grazed stubble alone for 10 weeks; animals on treatment C (24 ewes ha −1) received alfalfa hay at 0.5% LW (as-fed basis) after 4 weeks of grazing. At the start of the 11th week of grazing (last 5 to 6 weeks of gestation) alfalfa supplementation was discontinued and animals from each plot received a high (200 g cottonseed meal and 300 g whole barley) or a low (200 g cottonseed meal and 50 g whole barley) daily concentrate supplement. At lambing, all ewes were removed from the stubble and given an identical pen-fed ration of 1250 g chopped alfalfa hay, 400 g dried sugar beet pulp and 500 g whole barley. Stocking rate had no effect on biomass throughout the trial. Amount of wheat stubble and weeds did not differ up to the fourth week of grazing but declined sharply thereafter ( P< 0.05). Residual grain totally disappeared during the same initial period. Crude protein (CP) and fiber fractions of weed-free stubble were similar first but then CP decreased ( P<0.05) and fiber fractions increased ( P<0.05), except for acid detergent lignin which remained constant. Crude protein and ash content of esophageal extrusa samples decreased ( P<0.05) and neutral detergenber increased ( P<0.05) with increasing stocking rate. In vitro digestibility of extrusa and ewe DM intake tended to be lower at the higher stocking rate. Stocking rate had no effect on ewe performance on treatments A and C whereas animals on treatment B initially gained but then lost weight. Concentrate supplementation during the last 4 weeks of gestation tended to double LW gain of ewes on treatment A, compared to C. Lamb birth weight averaged 4.0 kg. Weight gains of A lambs were higher than of C lambs ( P<0.01), suggesting that ewes on treatment A had been fed adequately and produced enough milk for normal lamb growth rate, but ewes on B had not.

Pulmonary pressure-flow relationships in the fetal lamb during in utero ventilation

Pressure-flow relationships in the ventilated lung have not been previously determined in undelivered fetal sheep. Therefore we studied 11 late-gestation chronically prepared fetal sheep during positive-pressure ventilation with different gas mixtures to determine the roles of mechanical distension and blood gas tensions on pressure-flow relationships in the lung. Ventilation with 3% O2-7% CO2 produced a substantial fall in pulmonary vascular resistance even though arterial blood gases were not changed. Increases in pulmonary arterial PO2 during ventilation were associated with falls in pulmonary vascular resistance beyond that measured during mechanical distension. Decreases in pulmonary arterial PCO2 and associated increases in pH were also associated with falls in pulmonary vascular resistance. Pulmonary blood flow ceased at a pulmonary arterial pressure that exceeded left atrial pressure, indicating that left atrial pressure does not represent the true downstream component of driving pressure through the pulmonary vascular bed. The slope of the driving pressure-flow relationship in the normal mature fetal lamb was therefore different from the ratio of pulmonary arterial pressure to pulmonary arterial flow. We conclude that mechanical ventilation, increased PO2 and decreased PCO2, and/or increased pH has an important influence on the fall in pulmonary vascular resistance elicited by positive pressure in utero ventilation of the fetal lamb and that the downstream driving pressure for pulmonary blood flow exceeds left atrial pressure.

Ovine White-Liver Disease (OWLD). Serum Copper and Effects of Copper and Selenium Supplementation

Serum copper was generally higher in lambs affected with ovine white-liver disease (OWLD) than in cobalt/vitamin B12 supplemented lambs grazing the same pastures. Although the copper content of the grass was very low on the OWLD pastures, dosing lambs with Cu alone resulted in worsening of the clinical condition and aggravation of clinical pathology. Dosing with selenium had no effect on OWLD. Dosing with a combination of Co, Se and Cu resulted in normal lamb growth and normal laboratory tests. Lambs growing well on other pastures (H) showed elevated serum Cu when they were subclinically B12 deficient.

Pulmonary Development in the Fetal Lamb with Severe Bladder Outlet Obstruction and Oligohydramnios: A Morphometric Study

The lethal feature of male newborns with severe bladder outlet obstruction and oligohydramnios is pulmonary hypoplasia. We report a fetal lamb model of bladder outlet obstruction created in the early second trimester, and morphometric analysis of the profound pulmonary hypoplasia that resulted. At 55 to 65 days of gestation 8 consecutive male fetuses underwent surgical clipping of the urethra and urachus near the abdominal wall. A sham operation was performed in 1 female fetus. The lambs were delivered by cesarean section 10 weeks later. The right lungs were immediately fixed at a distending pressure of 25cm. water. The results of the morphometric studies were compared to control animals from our earlier study of normal fetal lamb lung development; slides for both studies were scored in a blind, randomized fashion by 1 of us (S. G. D.). Although mean body weights for the groups were similar, mean right lung volume in the operated lambs was 63.8cM.3 compared to 158cM.3 in the control animals and 137cM.3 in the sham operated fetus (p less than 0.0005). Relative volume of respiratory tissue was 87 per cent in the operated animals, and 92 per cent in the controls and the sham operated fetus (p less than 0.0005). Microscopic morphometry revealed an increased relative volume of inter-alveolar tissue in the experimental animals (35 compared to 23 per cent in the normal lambs, p less than 0.05), with a corresponding decrease in relative airspace volume. Alveolar numerical density and alveolar surface density were not statistically different between the groups, although total alveolar number and surface area were substantially decreased in the operated lambs due to the reduced mean lung volume. Mean alveolar wall thickness was increased at 3.6μM. in the operated group versus 2.1μM. in the normal group (p less than 0.0005) and 2.8μM. in the sham operated fetus. Thus, the lung in the lamb with severe bladder outlet obstruction is hypoplastic and immature.

Evidence for estrogen-dependent blastocyst formation in the pig.

The physiological significance of estradiol-17beta for the early embryonic development in the pig was investigated in vitro by four different experimental designs. A total of 1635 morphologically intact morulae were cultured in vitro in Krebs-Ringer bicarbonate solution supplemented with 10% heat-inactivated lamb serum, and the blastocyst formation rate (BFR) was recorded after 24 or 48 h. The addition of estradiol-17 beta (0.1 nM, 1 nM, 100 nM), progesterone (100 nM, 500 nM) or cortisol (100 nM) to the culture medium did not affect BFR (95 to 100%, Experiment 1). Similarly, adding charcoal-stripped lamb serum to the medium instead of normal lamb serum in the absence or presence of 1 nM estradiol-17 beta had no effect (93 to 95% BFR, Experiment 2). The antiestrogen Nafoxidine, however, at a concentration of 15 micrograms/ml, significantly (p less than 0.01) reduced BFR to 13.3 +/- 5.8% compared to controls (93.3 +/- 4.2%, Experiment 3). Supplementation with estradiol-17 beta (1 nM) in the presence of 15 micrograms/ml Nafoxidine significantly (p less than 0.01) improved BFR to 57.2 +/- 8.9%. Higher concentrations of estradiol-17 beta (100 nM, 100 microM) did not further enhance BFR. The stimulatory effects of estradiol-17 beta were specific since the BFR remained low in the presence of 100 nM progesterone (10.0 +/- 4.5%) or 100 nM cortisol (3.3 +/- 3.3%). Addition of 5% estradiol-17 beta-antiserum to the culture medium (Experiment 4) significantly (p less than 0.01) reduced BRF to 51.9 +/- 6.7% compared to controls (93.1 +/- 2.2%).(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental changes in myocardial contractile reserve in the lamb.

We have assessed serial changes in myocardial contractility and reserve in the normal lamb over the first month of life using an in vivo adaptation of the endsystolic pressure-volume relationship. Via a left thoracotomy, we insert a catheter tip pressure transducer into the left ventricle, affix an echo transducer onto the left ventricular epicardium, place an electromagnetic flow transducer around the pulmonary artery, and insert catheters for monitoring and infusions. We measure contractility by generating left ventricular wall stress-volume index (the cube of dimension) curves, at the same time increasing afterload by infusing phenylephrine. The slope of the endsystolic wall stress-volume index relationship is our index of contractility. Weekly studies were performed at rest and during isoproterenol infusion in 12 animals, and after propranolol administration in four. The data showed a progressive decrease in resting contractility but no change in maximal contractility during isoproterenol infusion over the 4 wk. Taking each week separately, the average increase in contractility during isoproterenol infusion was small at 1 wk (13%), moderate at 2 and 3 wk (24 and 26%, respectively), and large at 4 wk (79%). beta-Adrenergic blockade with propranolol caused a significant decrease in contractility in three of four animals studied at 1 wk, in only one of four animals at 2 wk, and in none of four animals at 3 or 4 wk. Thus, the newborn lamb shows a limited reserve in contractility that increases progressively with age; the limited reserve appears secondary to a high resting beta-adrenergic state.

The effect of halothane anaesthesia on the asphyxiated foetal lamb in utero.

In a previous study, we examined the effects of halothane on the normal foetal lamb in utero. The most significant finding was a 33 per cent fall in foetal mean arterial blood pressure (MABP). Cardiac output and placental blood flow were not affected. To determine if the asphyxiated foetus would respond similarly, the following study was performed. Seven pregnant ewes were surgically prepared two days prior to study with maternal and foetal indwelling arterial and venous cannulas. An inflatable occlusion loop was secured around the umbilical cord. On the day of study, a tracheostomy was performed on each ewe. Microspheres were injected into the foetal circulation during the control period. The occlusion loop was inflated to produce foetal asphyxia and microspheres were again injected. The ewe was then anesthetized with halothane; and after 15 minutes, microspheres were injected into the asphyxiated foetus and halothane levels were measured. The asphyxiated foetuses showed a significant rise in MABP, fall in heart rate and fall in cardiac output from control. Blood flow to the brain was significantly increased and flow to the placenta and gut decreased. Exposure of the asphyxiated foetus to halothane resulted in a fall of MABP to control but no significant change in cardiac output or brain blood flow. The mean halothane level in the foetus was 46.0 mg X l-1 or 0.32 vol%. Exposure of the asphyxiated foetus to halothane for 15 minutes does not produce significant further deterioration of the foetal lamb in utero.

Effect of Halothane on Cardiac Output and Regional Flow in the Fetal Lamb In Utero

We studied the effect of halothane on the fetal cardiovascular system of six lambs in utero by measuring fetal heart rate and femoral arterial blood pressure and by injecting labeled microspheres during a control period and again after 60 and 90 min of halothane anesthesia administered to six pregnant ewes at an inspired concentration of 1.5%. There were no significant effects on maternal cardiovascular function or acid-base balance, but fetal blood pressure decreased significantly by 27% after 8 min of halothane anesthesia and remained at this level for the duration of the experiment. However, there were no significant changes either in fetal regional blood flow to the vital organs or in fetal cardiac output. Fetal oxygenation and acid-base status remained stable. We conclude that in normal fetal lamb in utero the decrease in mean fetal arterial blood pressure associated with maternal halothane anesthesia is due to a decrease in peripheral vascular resistance because regional blood flow and acid-base status are well maintained.

Bluetongue virus serotype 20 infection in pregnant Merino sheep

Eleven maiden Merino ewes, free of antibody to bluetongue virus serotype 20 (BTV-20) in agar gel immunodiffusion and serum neutralisation tests, were mated once with a ram. Ten ewes were inoculated with BTV-20 35 to 42 days after service, and one ewe was left as an uninoculated control. One of the inoculated ewes and the control ewe remained uninfected throughout the experiment. Eight of the remaining 9 ewes showed clinical signs ranging from mild to moderate, and the other showed no clinical signs of infection. BTV-20 viraemia was detected in ewes between days 3 and 11 post inoculation, and the serum antibody response was followed. The control ewe and 5 of the 9 infected ewes were pregnant when examined 90 to 97 days after service. Each of these animals produced a normal lamb. There was no evidence of abortion in the remaining 5 ewes, and no transplacental transfer of virus was detected in the lambs of the 5 infected ewes. At necropsy, 46 days after the birth of the last lamb, no gross or microscopic lesions were observed in either the ewes or lambs.

Studies of the optical spectra of CaCl and SrF at sub-Doppler resolution

Lines in the (0, 0) bands of the A2Π–X2Σ+ and B2Σ+–X2Σ+ systems of CaCl and the B2Σ+–X2Σ+ system of SrF have been studied at sub-Doppler resolution by intermodulation spectroscopy. The linewidth was typically 40 MHz (f.w.h.m.). The 19F hyperfine splitting was resolved in the SrF spectrum and was measured for several rotational lines. The measurements were used in conjunction with the hyperfine parameters for the molecule in the ground state (measured by e.s.r.) to determine the following parameters for the B2Σ+ state: b= 12.9 ± 1.6 MHz c=–51 ± 28 MHz. These results suggest that the molecule is ionic, Sr+F–, in the B state. It has not proved possible to resolve 35Cl or 37Cl hyperfine structure in any of the lines studied in either the A–X or the B–X transitions of CaCl. There are pronounced crossover signals in the A–X system which have a negative sign (i.e., opposite to the normal Lamb dip signal). The dependence of these signals on various experimental parameters has been investigated. A density matrix description of the three-level system is presented and solved to 4th order by an iterative method. To this order, the model predicts that the Lamb dip and crossover signals should have the same sign.

Infection of pregnant sheep with the NADL strain of bovine virus diarrhoea virus and their subsequent challenge with Border disease IIB pool

Ten South Country Cheviot ewes were injected intraperitoneally with NADL strain of bovine virus diarrhoea virus (BVD) on the 54th gestational day. At term, one produced a weak hairy lamb with generalized hypomyelinogenesis of the CNS-features characteristic of Border disease (BD) 3 produced non-hairy, normally myelinated offspring with severe intracranial malformations, one aborted and one produced an apparently normal lamb. Four ewes were killed at intermediate stages of gestation and some of the foetuses and placentae had lesions consistent with BD or the early phases of intracranial malformation. The following year the surviving 6 ewes were challenged with a pool of BD infected lamb brain; one produced a BD affected lamb, one a lamb with severe neural and skeletal malformations and one aborted. The other 3 produced normal offspring. The findings emphasize the close similarity between BVD and BD virus diseases and the variable extent of cross immunity between strains. It is suggested that the outcome of infection with these viruses is dependent upon genetic make-up and immune status of the dam and the strain of infecting virus in addition to the gestational age at infection.

Myocardial Rupture: III. Chamber Pressure, Rate of Distention, and Ventricular Disruption in Isolated Hearts

We have developed an in vitro technique for producing myocardial rupture in lamb hearts, which relates tensile strength to a variety of conditions which can prevail in normal and infarcted human hearts. Retrograde perfusion of saline solution and inflation of the left ventricle was used to apply progressive stress to the left ventricular wall. Three separate sites of myocardial rupture were observed and occurred with the frequency of 54% at the papillary muscle, 30% at the interventricular septum, and 16% at the free wall of the left ventricle. The distribution and configuration of the experimental ruptures were similar to those usually noted as complications of human myocardial infarction. The mean rupturing pressure was 526 mm Hg in normal lamb hearts. Application of these techniques should ultimately provide data relevant to the diagnosis, prevention, and treatment of myocardial rupture.

Mutations altering the cellular localization of the phage lambda receptor, an Escherichia coli outer membrane protein.

Two mutant strains of Escherichia coli have been isolated in which the cellular location of an outer membrane protein, the phage lambda receptor (the lamB gene product), is altered. These mutations were initially selected in a strain containing a lamB-lacZ fusion. In the parent strain the protein coded for by the hybrid gene is located, at least in part, in the outer membrane. In the mutants it is located in the cytoplasm. The mutations responsible for the alteration of cellular location lie very early in the lamB gene, in a region corresponding to the NH2-terminus of the lambda receptor protein. One of these mutations is a small deletion internal to the lamB gene. When this mutation is present in an otherwise wild-type lamB gene, the protein produced is of lower molecular weight than normal receptor. The other mutation behaves as a point mutation; when it is present in an otherwise normal lamB gene, reversion can be demonstrated. The molecular weight of this mutant protein, which is located in the cytoplasm, is larger than that of the wild-type gene product by approximately 2000. It is suggested that these two mutations are in the portion of the lamB gene coding for a signal sequence and thereby block export of the protein.

Radioimmunassay of ovine alpha-fetoprotein

Highly purified ovine alpha-fetoprotein (AFP) was used both for radioisotope labelling and as the reference standard in the double antibody radioimmunoassay of ovine AFP. The sensitivity of the assay is 2 ng/ml which is about 8000 times more sensitive than radialimmunodifussion assay. The assay is of sufficient sensitivity to quantitate AFP in normal adult sheep serum, pregnancy serum, amniotic fluid and fetal lamb serum.

Effect of cortisol on liver glycogen concentrations in hypophysectomized, adrenalectomized and normal foetal lambs during late or prolonged gestation.

1. The changes in liver glycogen concentration in normal, adrenalectomized and hypophysectomized foetal lambs have been examined during the last third of gestation using a biopsy technique to remove one or more samples of liver from the same foetus at different gestational ages. 2. The rate of glycogen deposition increased sharply from about 130 days' gestation in normal lamb foetuses whereas after hypophysectomy or adrenalectomy liver glycogen concentrations remained low even when gestation was prolonged. 3. I.V. infusions of cortisol (4-10 mg/day) for 52 hr resulted in four- to fivefold increases in liver glycogen in all three groups of foetuses. The level of glycogen in the liver appeared to be related to log plasma corticosteroid concentration in all foetuses whether they had received cortisol infusions or not. 4. Little or no change occurred in glycogen concentration in other foetal tissues apart from a decrease in the glycogen levels in peri-renal fat of adrenalectomized and hypophysectomized foetuses after cortisol infusion. There were also no detectable changes in foetal plasma lactate, urea or alpha amino nitrogen following the cortisol infusions. Foetal plasma glucose values rose slightly but this change was significant only in the adrenalectomized group. 5. The 52 hr cortisol infusions to the foetus resulted in a slight but significant fall in maternal plasma progesterone in the last few hours of the infusion period.

Effects of Selenium and Vitamin E Deficiencies in Lambs on Hepatic Microsomal Hemoproteins and Mitochondrial Respiration

Microsomal hemoprotein levels and delta-amino levulinic acid dehydrase activity were determined in livers and rate of oxygen uptake, ADP:O ratios, and respiration control index were determined on mitochondria from muscle, liver, and heart of normal and white muscle diseased (WMD) lambs. WMD lambs were produced by feeding their dams either low selenium purified or alfalfa hay diets. Vitamin E and/or selenium was injected in a 2 x 2 factorial treatment in the ewes fed purified diets. Hepatic microsomal cytochrome P 450 levels and total heme content were significantly lower in WMD lambs. Cytochrome b5 content was significantly lower in lambs on the -E-Se or -E + Se treatments than those on the +E--Se treatment, but the cytochrome b5 content was not different between WMD and normal lambs from ewes fed the hay diet. No differences were found in hepatic delta-amino levulinic acid dehydrase activity, or in the rate of oxygen uptake, ADP:O ratios or respiratory control index between mitochondria from normal and WMD lamb tissue on any of the treatments.

IMPAIRED SURFACTANT PRODUCTION IN CRETIN LAMBS

Mid-gestation fetal thyroidectomy was performed to study the effect of congenital hypothyroidlsm on the availability and composition of pulmonary phospholipids (PPL) in 8 fetal lambs and 8 sham operated lambs. Amniotic fluid (AF) was collected for baseline thyroxine, thyrotropin, and 3,3'5' tri-iodothyronine. Mean preterm AF lecithin to sphingomyelin (L/S) ratios were 1.15; non-acidic and acidic PPL were 43% and 57% of total. Delivery at term by hysterotomy yielded 2 cretin and 8 normal lambs. Newborn serum studies confirmed hypothyroidism. At term mean normal AF L/S ratios were 1.89 with AF cortisol levels of 1.60 μg/dl. Term cretin AF L/S ratios were 1.56 with AF cortisol levels of 1.3 g/ dl. Lambs breathed for 10 to 30 min., then pharyngeal, tracheal, and gastric contents were aspirated for L/S ratios and PPL assays. Mean normal lamb L/S ratios were 6.66 vs 1.52 for cretins (p<.03). Non-acidic to acidic PPL separation reversed in normal lambs to 63% and 37%; cretins increased the acidic to 69%. Percent postnatal phosphatides in total aspirate PPL were:Cretin lambs died at 2 hr. of age of profound respiratory failura.We conclude that congenital hypothyroidism results in the formation of surfactant with an abnormal phosphatide composition and the release of predominantly acidic PPL with poor surface activity.

Protein-energy relationships in the digestion products of sheep fed on herbage diets differing in digestibility and nitrogen concentration

The digestion of organic matter and nitrogen in 17 herbages was studied in sheep fitted with duodenal re-entrant cannulas. Each herbage was in chopped form, and was given at levels close to ad libitum but offered at an even rate hourly by automatic feeder. Diets ranged from 0.4 to 5.1% nitrogen and from 49 to 79% digestibility of organic matter (OM). At the levels of intake achieved, the apparent digestibility of OM in the stomachs ranged from 28 to 45%; between 54 and 72% of the apparently digested OM disappeared before the duodenum. Though the percentage of the digestible OM digested across the stomachs tended to increase with decreasing overall digestibility, the relationship was poor (r² = 0.25). Of the OM apparently digested between duodenum and faeces, 5ndash;40% could be accounted for as crude protein. Non-protein OM digested in the intestines contributed about 25% of total apparently digested OM. The nitrogen intakes extended over a range of 1.8–57.1 g/day, and the apparent digestibility of nitrogen rose from negative values to 84% with increasing nitrogen intake. Small gains (1–3 g) in nitrogen at the lower end and substantial losses of up to 40% of nitrogen at the upper end of the dietary range resulted in yields of non-ammonia nitrogen (NAN) of 2.4–32 g/day at the duodenum, of which 75–80% was accounted for as α--amino nitrogen. Crude protein yielded at the duodenum ranged from 10.3 to 42.5 g/100 g OM apparently digested across the stomachs. Metabolic faecal nitrogen losses were estimated at 0.65 g/100 g OM entering the duodenum of which 0.60 g was estimated to arise in the intestines. Over all diets the estimated mean true digestibility of NAN entering the intestines was 84%. Crude protein truly digested in the intestine contributed 5.6–21.2 g of each 100 g OM apparently digested, or an estimated 5.3–20 g of each 100 g OM truly digested. This would have provided from c. 7% to c. 24% of digestible energy as protein, or 14–45 g truly digestible true protein/Mcal metabolizable energy (ME) to the animal. While a 12-fold range of dietary crude protein concentration was condensed to a fourfold range of protein concentration in the OM digested by the animal, it is suggested that diets 1–13 still provide insufficient protein per unit energy to meet requirements for normal lamb growth even if adequate ME intake could be achieved, and that diets 1–8 would not provide adequate protein for maintenance. The protein yield as grams truly digested true protein per Mcal ME (P) was related to the dietary nitrogen concentration, expressed as grams per 100 g digestible OM (N), by the equation P = 11.50 + 4.58N (?3.19; r² = 0.88) However, despite the high correlation, prediction on this basis would not separate diets in the mid-range of nitrogen concentration (i.e. 3.0 g N/100 g digestible OM) which provided, in terms of eventual protein yield per unit energy, 19–42 g truly digestible true protein per Mcal ME (or roughly 11–22% of calories).

Toughness in lamb induced by rapid chilling

SummaryLamb carcasses were chilled rapidly and slowly under controlled conditions and the texture of the meat examined after cooling and after conditioning at 0°C. Sensory and objective measurements of texture showed that the rapid chilling rate induced toughness in normal lamb carcasses. Texture was in all cases significantly improved by conditioning, but the rapidly chilled samples remained undesirably tough. The tenderizing effect of conditioning was measurable by both sensory and mechanical assessments of texture, but the changes in sarcomere length were only marginal.

Automatic system for the determination of the coordinates of defects and their number in the inspection of sheets by means of normal (Lamb) waves: Defectoskopiya, No 1 (1968) pp 12–16

Automatic system for the determination of the coordinates of defects and their number in the inspection of sheets by means of normal (Lamb) waves: Defectoskopiya, No 1 (1968) pp 12–16