Genetic analyses of scrotal circumference size and growth in Rambouillet lambs

The objectives of this study were to identify nongenetic factors influencing scrotal circumference size and growth and to estimate heritabilities of scrotal circumference size at different ages and scrotal circumference growth between ages. Data on scrotal circumference, live weight, and age were recorded over 6 yr (1982 to 1987) on 541 spring-born Rambouillet ram lambs (109 sires, 307 dams) at the Dixon Springs Agricultural Center. Scrotal circumference and live weight were predicted at four ages (90, 120, 150, and 180 d) for each lamb. The two models used to evaluate factors affecting scrotal circumference size at fixed ages were the same except for the addition of live weight and live weight squared to one of the models. Likewise, the two models used for scrotal circumference growth between ages were the same except for the addition of live weight change and live weight change squared to one of the models. Year and type of birth were significant sources of variation for both traits under both models. Regression coefficients for live weight and live weight squared on scrotal circumference size and for live weight change and live weight change squared on scrotal circumference growth and for day of birth within year for both traits were generally different from zero (P less than .05). Heritability estimates for scrotal circumference size at fixed ages ranged from .19 to .41. Adjustments for live weight led to an average 41.5% increase in heritability estimates. For scrotal circumference growth, heritabilities ranged from .17 to .60 and adjustments for live weight change resulted in an average 13% decrease in estimates.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of prenatal testosterone treatment on nitrogen utilization and endocrine status of ewe lambs

Thirty-eight pregnant Suffolk ewes were assigned randomly to a control group or implanted with approximately 2 g of testosterone propionate (TP) when they were between d 40 and 60 of gestation. Implants were removed 3 wk prior to lambing. Five ewe lambs born to implanted ewes and ten ewe lambs born to nonimplanted ewes were utilized in this experiment. Ram lambs were not used in this trial. No differences (P greater than .10) were observed for fecal, urinary and total N excretion and amount of N absorbed. Nitrogen retained (percentage of N intake and g/d) was higher (P less than .05) in prenatally androgenized ewe lambs than in control ewe lambs. Plasma insulin concentrations averaged 99% higher (P less than .05) in prenatally androgenized ewe lambs. Plasma insulin-like growth factor I (IGF-I) concentrations averaged 29% higher (P less than .06) in ewe lambs treated prenatally with testosterone. Nonesterified fatty acid (NEFA) concentrations averaged 41% higher (P less than .05) in prenatally androgenized ewe lambs. Significant (P less than .05) treatment x time effects were observed in plasma thyroxine, glucose and urea N concentrations of prenatally androgenized vs control ewe lambs. These significant modifications in the plasma metabolite and endocrine status could be an important element of the physiological mechanism(s) by which prenatal androgenization improves growth performance and leanness of ewe lambs.

Effect of prenatal trenbolone acetate treatment on lamb performance and carcass characteristics

Forty-three pregnant Dorset and Dorset crossbred ewes were assigned randomly to a control group or implanted with either 300 mg trenbolone acetate (Low TBA) or 1,200 mg trenbolone acetate (High TBA) between d 40 and 60 of gestation. Adjusted weaning weights for ewe lambs were 23.3% less (P less than .10) with vs without TBA treatments. Postweaning ADG of ewe lambs was lower (P less than .05) but ADG of ram lambs was greater (P less than .05) for high TBA vs low TBA. Ewe lambs receiving high TBA had 19% less (P less than .05) gain per unit of feed than those receiving low TBA. Days on test for ewe lambs was greater (P less than .05) due to TBA treatment and for high TBA vs low TBA. Days on test for ram lambs was decreased (P less than .05) due to high TBA compared to low TBA. Subcutaneous fat over the ribeye and lower rib were greater (P less than .05) for high-TBA ewe lambs vs low-TBA ewe lambs. Percentage kidney and pelvic fat of ewe lambs was lower (P less than .05) due to TBA treatments. Ribeye area per unit of carcass weight was lower (P less than .05) in high-TBA ewe lambs vs low-TBA ewe lambs. Yield grade of ewe lambs was lower (P less than .05) for low TBA vs high TBA. Prenatal trenbolone acetate treatment of ewe lambs did not improve their subsequent postnatal growth performance and carcass traits. In addition, TBA implantation of the pregnant ewe produced dystocia and less milk production, as evidenced by the need for more lambs to be grafted.

Factors affecting productivity of Rambouillet ewes mated to ram lambs

Objectives of this study were to estimate the magnitude of the effects of various factors associated with ewes and their ram lamb mates on fertility, prolificacy, lamb survival, lamb weaning weight and ewe productivity and to estimate the heritability and repeatability of each trait. Records from 731 ewe-years, 75 ram lamb sires and 616 lambs born from the University of Illinois Rambouillet flock were used. Ewes mated to single-born ram lambs had higher fertility rates (P less than .01), gave birth to lambs with higher survival rates (P less than .01), weaned lighter (P less than .05) individual lambs but weaned more weight of lamb per ewe exposed (P less than .01) than ewes mated to multiple-born ram lambs. Ram lamb breeding weight, ram lamb scrotal circumference, ewe breeding weight and ewe age had relatively large and positive effects on the composite trait of weight of lamb weaned per ewe exposed and significant effects on a number of the component traits. Heritability and repeatability estimates were, respectively, as follows: fertility, 3%, 3%; prolificacy, 34%, 19%; lamb survival, 15%, 8%; lamb weaning weight, 7%, 36%; and ewe productivity, 27%, 10%.

Effect of prenatal androgenization on lamb performance, carcass composition and reproductive function

Two experiments were conducted in which pregnant crossbred ewes were randomly assigned to a control group or implanted with testosterone propionate/silastic implants between d 40 and d 60 of gestation. Implants contained approximately 2 g testosterone propionate and provided a constant delivery of 8.7 mg/d. Androgenized ewes (TE), born to implanted dams, had lower adjusted birth weights (P less than .05) than control ewes (CE) in both experiments. Treated rams (TR) also displayed lower birth weights than control rams (CR) in both experiments, but the difference was significant only in Exp. 2. Average daily gain was 16.4% more (P less than .05) for TE than for CE in Exp. 1. In Exp. 2, TE gained 9.6% faster (P less than .05) and had 14.6% (P less than .05) more weight per unit of feed consumed than CE. In both experiments, average daily gain and gain-to-feed ratio were similar for TR and CR. In Exp. 2, prenatal androgenization of ewes reduced (P less than .05) 12th rib fat thickness and decreased (P less than .05) percent kidney and pelvic fat. Yield grades of TE were lower than CE in both Exp. 1 (P less than .10) and Exp. 2 (P less than .05). From additional measurements taken in Exp. 2, liver weight per unit of carcass weight was greater (P less than .05), anogenital distance was greater (P less than .01) and test tube penetration into the vestibule was less (P less than .01) for TE than CE. The TE did not exhibit regular estrous cycles, while CE displayed recurring estrous cycles.

Effects of plane of nutrition and phenobarbital during the pre-mating period on reproduction in ewes fed differentially during the summer and mated in the fall

An increased plane of nutrition of ewes before mating (flushing) has been associated with an increased number of lambs per ewe. The following study was done to investigate a possible mechanism for the flushing effect. During the summer, 98 Hampshire and Suffolk ewes grazed pastures with 50 of the ewes supplemented with .45 kg of corn grain X head-1 X d-1. For approximately 12 d before fall mating, each ewe received daily either .45 kg of a corn grain-soybean oil meal mixture, an oral dose of 1 g phenobarbital or no treatment. Liver biopsies were collected from 23 ewes, representing all treatment combinations, 3 d after initiation of pre-mating treatment for determination of concentration of hepatic mixed function oxidase enzymes (MFO). Summer supplementation vs no summer supplementation resulted in ewes with heavier (P less than .05) body weights near mating (75.6 vs 71.1 kg), higher (P less than .01) mating condition scores (3.2 vs 2.9), a greater (P less than .01) number of ovulations (1.99 vs 1.74), but little difference (P greater than .10) in number of lambs born per ewe lambing. Pre-mating treatment with phenobarbital or grain mix resulted in a greater number of ovulations (P less than .01, P less than .10, respectively) than no pre-mating treatment (2.14, 1.85, 1.60; respectively). Ewes given phenobarbital had more (P less than .10) lambs per ewe than ewes given no treatment (1.71 vs 1.40). Both phenobarbital and grain mix resulted in a significant increase in concentration of MFO compared with no treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of temazepam elixir and trimeprazine syrup as oral premedication in children undergoing tonsillectomy and associated procedures

Temazepam 0.5, 1.0 and 1.5 mg kg-1 in an elixir formulation (Euhypnos Elixir), was compared with trimeprazine tartrate 3 mg kg-1 in a syrup (Vallergan Forte Syrup), as premedication in 220 children (ASA grade I) undergoing tonsillectomy and associated procedures. Each patient was randomly allocated to one of the four treatments. The administration was blind to the observers in theatre, recovery room and postoperative ward, who assessed each patient according to a total of 14 criteria. A modelling technique allowed account to be taken of the effects of concomitant variables (e.g. age and duration of anaesthesia) where appropriate. No statistically significant difference was found between the efficacy of the treatments. The only statistically significant differences were that temazepam was associated with more ectopic beats under anaesthesia (P = 0.03 or 0.002, depending on the test applied), more postoperative vomiting (P = 0.04) and more postoperative restlessness (P less than 0.0001).

The effects of anaesthetics and high pressure on the responses of the rat superior cervical ganglion in vitro

The effects of helium pressure and of general anaesthetics were studied on the responses of the isolated superior cervical ganglion of the rat, to determine how far these reflected the pressure reversal of anaesthesia seen in vivo. The method of Brown & Marsh (1974) for extracellular recording of surface potentials was adapted for use in a high-pressure chamber. Helium alone, at 130 atm, did not alter the responses of the ganglion to gamma-aminobutyric acid (GABA) but significantly depressed the depolarizing and hyperpolarizing components of the nicotinic responses, and the muscarinic responses. The potentiation of the responses to GABA caused by pentobarbitone was not altered by the application of helium, at 130 atm. This pressure also decreased further the nicotinic responses which were depressed by pentobarbitone. Nitrogen, at 34 atm (the anaesthetic ED50 in vivo) and at 68 atm, significantly decreased the nicotinic responses of the ganglia, and the addition of helium to a total of 130 atm further increased this depression. At pressures of 3.3-68 atm, nitrogen caused small decreases in the responses to GABA. Nitrous oxide at 1.5 atm (the ED50 for loss of righting reflex in mice) and at 3 atm, significantly depressed the responses to GABA and to the nicotinic agonist, but did not alter the responses to methylfurmethide. The effects of nitrous oxide were unaltered when helium was added to a total of 130 atm, although this pressure of helium added alone significantly depressed the cholinergic responses. A mixture of 50% nitrous oxide and 50% oxygen, when added to the pressure chamber, at normal atmospheric pressure, caused transient increases in the responses to GABA. The effects of temperature on GABA responses and on nicotinic responses were very different from those of pressure. Preliminary evidence suggested that raising the temperature may decrease the extent of potentiation of GABA responses by pentobarbitone. The results are discussed in relation to the pressure reversal of anaesthesia in vivo. It was concluded that there was no evidence that the basis of this interaction lay in the potentiation of GABA responses by general anaesthetics, or the depression of cholinergic responses, although the changes seen were not in all cases simply additive. It was considered that effects of general anaesthetics such as the potentiation of GABA may contribute to the effects used to measure general anaesthesia in vivo, such as loss of righting reflex, but may not be related to the non-specific actions which cause anaesthesia.

Evaluation of growth, carcass traits and reproductive organs of young boars in response to zeranol implantation

Two experiments were conducted to evaluate the effect of implants containing zeranol on growth rate, carcass composition, palatability and reproductive organ development of intact male pigs. In Exp. 1, three treatment groups were evaluated: control barrows, intact control boars and implanted boars (implanted at either 28, 56 or 112 d of age with one 12-mg dose of zeranol). In Exp. 2, four treatment groups were evaluated: control barrows, intact control boars, boars implanted at 28 d with 24 mg of zeranol (single implant) and boars implanted at 28 d and re-implanted at 56 and 112 d of age with 24 mg of zeranol (triple implant). Differences for average daily gain and carcass traits were not consistent between treatment groups with the exception of 10th rib fat, where barrows were fatter than boars. There were no differences among treatments due to zeranol for the reproductive organ characteristics, with the exception that bulbourethal gland and teat weights were heavier for boars in Exp. 2. Penis weights and lengths were lower for barrows in both experiments. Juiciness, tenderness, Warner-Bratzler shear force, pork flavor intensity and sensory scores were not consistently affected by male condition or zeranol treatment. In two of the three comparisons, implanted boars had higher off-flavor intensity scores in Exp. 1, but no treatment difference was observed in Exp. 2. Zeranol implantation did not result in significant changes in growth rate, development of reproductive organs or carcass characteristics of young boars.

Breed and sire effects on crossbred lamb production from Panama ewes and on spermatozoan midpiece length

Three-hundred mature Panama-type range ewes were mated to Clun Forest, Dorset, Border Leicester, Polypay and Suffolk rams during the 1979 and 1980 breeding seasons. Sire breed and ram within breed effects on lamb growth, ewe reproduction, spermatozoan midpiece length (MPL) and midpiece length coefficient of variation (MPLCV) were examined. Associations among MPL and MPLCV and economically important traits also were assessed. Suffolk-sired lambs weighted .18, 2.0 and 1.5 kg more, at birth, weaning and post-weaning, respectively, than the average of all groups. Dorset-sired lambs had the lightest postweaning weight. Variation was greatest among Suffolk rams for average weaning and postweaning weights of their progeny. The Border Leicester breed had the least among ram variation for progeny weaning weight; while variation among Dorset rams was least for progeny postweaning weight. Fertility (ewes lambing/ewe exposed) and prolificacy (lambs born/ewe lambing) of the rams' mates were not influenced significantly by sire breed. Lamb mortality also was not influenced by breed of sire nor by rams within a breed. For variation in MPL, 26.4% was due to the breed effect (P less than or equal to .01) and 21.6% was attributable to ram variation within a breed (P less than or equal to .01). Clun Forest rams had the longest average MPL and greatest MPLCV, while Dorsets had the shortest MPL and smallest MPLCV. There were no important associations between either MPL or MPLCV and any of the economic traits.

Thin-layer agarose isoelectric focusing: an improved technique for determining sheep hemoglobin type

An improved technique for rapid screening of sheep flocks for hemoglobin (Hb) type is presented. This technique, isoelectric focusing (IEF) on thin-layer agarose gels is simple, rapid, inexpensive and is suitable for screening large numbers of sheep for Hb type. With this technique, up to 100 sheep blood samples can be prepared, tested and interpreted within 2 h after samples are drawn. The new technique was shown to provide better resolution than polyacrylamide gel electrophoresis (PAGE) and was able to resolve samples in which the Hb had become partially degraded. These same samples could not be resolved by PAGE. The use of a special electroendosmosis-free grade of agarose provided resolution essentially equal to polyacrylamide as a matrix for IEF. The advantages are that the casting of the agarose gels is considerably easier, the focusing of samples is more rapid, staining and destaining times are greatly reduced and hazards from potential neurotoxicity of acrylamide are eliminated. Blood from 138 ewes at the Oregon State University Sheep Center was examined by the new agarose IEF technique to determine and demonstrate its usefulness for screening. No difficulty was encountered with interpretation of any of the samples. Frequencies of the HbA and B alleles were similar to those found in earlier studies when polyacrylamide tube gel electrophoresis was used. The observed frequencies were also similar to those expected with the population in Hardy-Weinberg equilibrium.

Effects of season and bread of sire on incidence of estrus and ovulation rate in sheep

The effects of season and breed of sire on estrous activity and ovulation rate were estimated in 50 mature ewes, 10 each sired by North Country Cheviot, Dorset, Finnsheep, Romney and Suffolk rams and born from Suffolk dams. Estrus was checked with vasectomized rams from July 1979 through December 1980. From May through December of 1980, ovulation rate was determined by the counting of corpora lutea (CL) during laparoscopic examinations of ovaries. A breed X month interaction (p less than .01) was found for incidence of estrus. Finnsheep-sired ewes were slower to enter anestrus and had the shortest anestrus period. Cheviot-sired ewes had the longest anestrus period. Ovulation rate, measured as the number of CL/ewe examined per month from August through December of 1980, was highest (P less than .05) in October and November. Finnsheep-sired ewes tended to have higher ovulation rates (2.04) per ewe ovulating than did Romney-or Cheviot-sired ewes (1.48). Suffolk- and Dorset-sired ewes were intermediate. Ovulation rate, measured as the number of CL/ewe available per month from May through December of 1980, was highest (P less than .05) in September, October and November. Suffolk-, Finnsheep- and Dorset-sired ewes had higher (P less than .10) ovulation rates (.95) per ewe available than did Romney- and Cheviot-sired ewes (.67). Monthly repeatability of ovulation rate from August through December of 1980 was .41 +/- .25.

Relationships between hemoglobin type and reproduction, lamb, wool and milk production and health-related traits in crossbred ewes

Relationships among hemoglobin (Hb) types and production traits were examined in 294 crossbred ewes from North Country Cheviot, Dorset, Finnsheep and Romney rams, and Suffolk and Columbia-type ewes. Hb BB ewe lambs were youngest at first estrus, while Hb AA ewe lambs were oldest. Ewe lamb fertility was similar for Hb AB and Hb BB ewes, and both were superior to Hb AA ewes. When Finnsheep crossbreds were excluded, from which Hb BB was absent, Hb BB ewes had higher ewe lamb fertility than did Hb AB ewes. There was a minor advantage of the A over the B allele in ewe lamb prolificacy. Hb BB ewes were highest, Hb AB ewes were intermediate and Hb AA ewes were lowest for average fertility, prolificacy per ewe lambing, lambs born per ewe exposed to mating, total number of lambs weaned and total kilograms of lamb weaned. Grease wool production, staple length, fiber diameter grade, incidence of medullated fibers and incidence of cotted fleeces all were similar across Hb types. Likewise, Hb type did not affect milk production or composition. Ewes with Hb AB had the lowest incidence of footrot; Hb AA and Hb BB ewes were similar. Ewes with Hb AA had the lowest fecal parasite egg counts, while ewes with Hb AB or Hb BB were similar. Ewes with Hb AA also had the lowest incidence of mastitis, Hb BB ewes were intermediate and Hb AB ewes were highest. The combination of overdominance (as for footrot resistance), beneficial effects of the A allele on health-related traits (as for mastitis and parasite resistance) and the beneficial effect of the B allele on reproductive traits, if real, could partly explain the genetic polymorphism commonly reported at the Hb locus in sheep.