Biomedical subjects

G D Snowder

Publications and source records attributed to G D Snowder.

At least 37 records · Page 2Linked to original sources

PubMed2000

Effect of the callipyge gene on muscle growth, calpastatin activity, and tenderness of three muscles across the growth curve.

Changes in muscle growth, calpastatin activity, and tenderness of three muscles were assessed in 20 callipyge and 20 normal wether lambs slaughtered at live weights (LW) of 7, 20, 36, 52, and 69 kg. At 24 h postmortem, the longissimus (LM), semimembranosus (SM), and supraspinatus (SS) muscles were removed and weighed and samples were obtained for calpastatin activity (CA; 24 h) and Warner-Bratzler shear force (WBS; aged 6 d). For muscle weights and calpastatin activity, the weight group x muscle x phenotype interaction was significant (P < 0.05). Muscle weights were similar (P > 0.05) between phenotypes for all three muscles at 7 kg LW. At 20 kg LW, the LM and SM muscles from the callipyge lambs were heavier (P < 0.05) than those from normal lambs; however, the SS did not differ (P > 0.05) between phenotypes at 7, 20, or 52 kg. From 20 to 69 kg LW, the LM and SM weights were 42 and 49% heavier (P < 0.05) for callipyge than for normal lambs. Calpastatin activity of the callipyge LM was greater (P < 0.05) than that of normal LM at 36, 52, and 69 kg. In the callipyge LM, CA was similar (P > 0.05) at 20, 36, and 52 kg LW and did not differ (P > 0.05) from 7-kg or 69-kg values. Calpastatin activity declined (P < 0.05) across the growth curve for the SM and SS, but values were higher (P < 0.05) in the SM in callipyge than in normal lambs. Shear force values of the LM were lower (P < 0.05) for normal lambs at 36, 52, and 69 kg LW than for callipyge lambs. In the SM and SS, WBS values decreased (P < 0.05) across the growth curve, but values were higher (P < 0.05) for callipyge lambs in the SM only. These data indicate that the selective muscular hypertrophy of the callipyge phenotype develops during the postnatal growth period between 7 and 20 kg LW (19 and 100 d of age). Longissimus and semimembranosus muscles in the callipyge lambs were over 40% heavier from 20 to 69 kg LW; however, they also had higher levels of calpastatin activity and Warner-Bratzler shear force during this time period, indicating the need for postmortem tenderization treatments to improve palatability.

Age Factors↗

PubMed2000

Genetic parameters among weight, prolificacy, and wool traits of Columbia, Polypay, Rambouillet, and Targhee sheep.

Genetic parameters for Columbia, Polypay, Rambouillet, and Targhee sheep were estimated using REML with animal models for prolificacy, weight, and wool traits. All bivariate analyses included a covariance between additive genetic effects for the two traits plus appropriate additional covariances. Number of observations by breed ranged from 5,140 to 7,095 for prolificacy traits, from 7,750 to 9,530 for weight traits, and from 4,603 to 34,746 for wool traits. Heritability estimates ranged from .03 to .11 for prolificacy traits (litter size at birth and litter size at weaning), from .09 to .26 for weight traits (birth weight and average daily gain), and from .25 to .53 for wool traits (fleece weight, fleece grade and staple length). Estimates of direct genetic correlations among prolificacy and among weight traits were positive and ranged from .58 to 1.00 and .18 to 1.00, respectively. Estimates of direct genetic correlation between fleece weight and staple length were positive (.50 to .70) but were negative between fleece weight and fleece grade (-.60 to -.34) and between staple length and fleece grade (-.72 and -.40). Prolificacy and wool traits were essentially uncorrelated. Weight and prolificacy traits were slightly positively correlated. Weight traits had a moderate positive direct genetic correlation with fleece weight and staple length, but were uncorrelated with fleece grade. These estimates of genetic parameters between prolificacy, weight, and wool traits can be used to construct multiple-trait selection indexes for dual-purpose sheep.

Age Factors↗

PubMed1999

Genotypic expression at different ages: I. Prolificacy traits of sheep.

Genetic parameters for prolificacy traits for Columbia (COLU), Polypay (POLY), Rambouillet (RAMB), and Targhee (TARG) breeds of sheep were estimated with REML using animal models. Traits were number of live births (LAB), litter size at birth (LSB) and weaning (LSW), and litter weight weaned (LWW). Numbers of observations ranged from 5,140 to 7,095 for prolificacy traits and from 5,101 to 8,973 for litter weight weaned for the four breeds. For single-trait analyses, ewes were classified as young (1 yr old), middle-aged (2 and 3 yr old), or older (> 3 yr old). After single-trait analyses, three-trait analyses were done for each characteristic with traits defined by age class. Generally, heritability estimates from single-trait analyses were low and ranged from .01 to .17 for LAB and LSB and from .00 to .10 for LSW. Heritability estimates obtained for LWW ranged from low to moderate (.00 to .25) and were less for older ewes. Heritability estimates from the three-trait analyses were generally similar to estimates from single-trait analyses. Heritabilities for LAB and LSB were similar, and, for three-trait analyses, they ranged across age groups from .07 to .13 for COLU, .13 to .16 for POLY, .10 to .16 for RAMB, and .01 to .16 for TARG. Estimates for LSW from three-trait analyses ranged from .07 to .12 for COLU, .04 to .09 for POLY, .01 to .11 for RAMB, and .03 to .11 for TARG. For LWW, heritabilities ranged from .00 to .21 for COLU, .05 to .08 for POLY, .12 to .15 for RAMB, and .18 to .29 for TARG. Genetic correlations for LAB, LSB and LSW among age-defined traits ranged from .25 to 1.00. Genetic correlations for LAB and LSB between young and middle and between young and older age classes were less than .80 in COLU, POLY, and RAMB breeds. Only genetic correlations between middle and older age classes for these breeds were greater than .80. For TARG, genetic correlations among all age classes were greater than .80 (.88 to 1.00) for those traits. All genetic correlations among ages for LSW were greater than .80 for POLY and TARG. For RAMB, only the correlation between young and older age classes for LSW was less than .80 (.45). None was greater than .80 for COLU. For LWW, genetic correlations among all age classes in POLY and RAMB were greater than .80 (.82 to 1.00). For COLU, genetic correlation between young and middle was low (.07), between young and older was high (.88), and between middle and older classes was moderately high (.54). For TARG, genetic correlations were .49, .65, and .98 for young-middle, young-older, and middle-older age classes, respectively. Results indicate that more progress could be made in selection programs for prolificacy traits in some sheep breeds by considering age of ewe as a part of the trait rather than by simply adjusting for ages of ewes.

Aging↗

PubMed1999

Genotypic expression at different ages: II. Wool traits of sheep.

Genetic parameters for wool traits for Columbia, Polypay, Rambouillet, and Targhee breeds of sheep were estimated with single- and multiple-trait analyses using REML with animal models. Traits considered were fleece grade, fleece weight, and staple length. Total number of observations ranged from 11,673 to 34,746 for fleece grade and fleece weight and from 3,500 to 11,641 for staple length for the four breeds. For single-trait analyses, data were divided by age of ewe: young ages (age of 1 yr), middle ages (ages of 2 and 3 yr), and older ages (age greater than 3 yr). Heritability estimates averaged over breeds for fleece grade decreased from .42 at a young age to .37 for older ages. For fleece weight, heritability estimates averaged .52, .57, and .55 within the successively older groups. Heritability estimates for staple length averaged .54 for young and middle age classes. Few older ewes had staple length measurements. After single-trait analyses, new data sets were created for three-trait analyses with traits defined by three age classes when animals were measured. Heritability estimates with three-trait analyses, except for a few cases, were somewhat greater than those from single-trait analyses. For fleece grade, the genetic correlations averaged over breeds were .72 for young with middle, .42 for young with older, and .86 for middle with older age classes. For fleece weight, the average genetic correlations were .81, .83, and .98. For staple length, the average genetic correlation for young with middle age classes was .82. Estimates of genetic correlations across ages varied considerably among breeds. The average estimates of correlations suggest that fleece grade may need to be defined by age, especially for the Columbia and Rambouillet breeds. For fleece weight and staple length, however, the average correlations suggest no need to define those traits by age.

Aging↗

PubMed1999

Genotypic expression with different ages of dams: III. Weight traits of sheep.

Correlations between genetic expression in lambs when dams were young (1 yr), middle-aged (2 and 3 yr), or older (older than 3 yr) were estimated with three-trait analyses for weight traits. Weights at birth (BWT) and weaning (WWT) and ADG from birth to weaning were used. Numbers of observations were 7,731, 9,518, 9,512, and 9,201 for Columbia (COLU), Polypay (POLY), Rambouillet (RAMB), and Targhee (TARG) breeds of sheep, respectively. When averaged, relative estimates for WWT and ADG were similar across breeds. Estimates were variable across breeds. On average, direct heritability was greater when environment was young dams (.44 for BWT and .34 for WWT) than when environment was dams of middle age or older (.24 and .28 for BWT and .20 and .16 for WWT, respectively). Maternal heritability was greater when dams were middle-aged or older (.28 and .22 vs .18) for BWT but was greater when dams were younger (.10 vs .05 and .04) for WWT. The estimates of genetic correlations for direct effects across age of dam environments averaged .32 for birth weight and averaged .70 for weaning weight. Average estimates of maternal genetic correlations across age of dam classes were .36 or less for both BWT and WWT. Average estimates of correlations among maternal permanent environmental effects were .49 or less across age of dam classes. Total maternal effects accounted for .33 to .42 of phenotypic variance for BWT and for .09 to .26 of phenotypic variance for WWT. The average estimates of genetic correlations between expressions of the same genotypes with different ages of dams suggest that measurements of BWT of lambs with dams in young, middle, and older age classes should be considered to be separate traits for genetic evaluation and that for WWT measurements with young age of dam class and combined middle and older age of dam classes should be considered to be separate traits for genetic evaluation.

Aging↗

PubMed1999

The callipyge phenomenon: evidence for unusual genetic inheritance.

In 1983, a male lamb exhibiting a pronounced muscular hypertrophy, particularly noticeable in the hind quarters, was born into a commercial Dorset flock in Oklahoma. The ram was premonitorily called Solid Gold. He subsequently produced offspring expressing the unusual phenotype, which is referred to as callipyge (Greek: calli- beautiful + -pyge buttocks). Animals demonstrating the callipyge phenotype are all descendants of this founder ram. These animals produce leaner, higher yielding carcasses, but there is some concern with decreased tenderness of the loin. Genetic characterization of the locus has demonstrated a unique mode of inheritance termed polar overdominance, in which only heterozygous offspring inheriting the mutation from their sire express the phenotype. The three other genotypes are normal in appearance. Progeny data indicate that reactivation of the maternal callipyge allele occurs after passage through the male germ line, although this reactivation is not absolute. The callipyge gene has been mapped to the distal end of ovine chromosome 18.

Animals↗

PubMed1999

Economics of callipyge lamb production.

This paper examines the economic implications of callipyge (CLPG) lamb production. The price, as it relates to competing meats and excess fat, significantly impact lamb demand, and CLPG genetics improves those factors. The CLPG phenotype does not affect number or weight of lambs weaned or postweaning ADG, but it does improve postweaning feed efficiency by approximately 10%; dressing percentage approximately 7.5%; and yields of wholesale leg (11.8%), loin (4.7%), rack (2.5%), and shoulder (2.3%). Total production costs for a 59-kg lamb are 4% lower in CLPG lambs due to improved feed efficiency. Assuming pelt and offal value pays for slaughter costs, the costs of normal (N) and CLPG carcasses are the same as for live lambs, $81 and $78, respectively; but, due to dressing percentage, the N carcass weighs 29.2 kg and the CLPG carcass, 31.4 kg. Thus, carcass costs for N and CLPG lambs are $2.77/kg and $2.49/kg, respectively. Decreased feed costs, combined with increased carcass and primal cut yields for CLPG lambs, lowers the price required to recover meat costs for leg, loin, rack, and shoulder by 19.7, 14.4, 12.6, and 11.9%, respectively. Successful marketing of CLPG loin and rack depends on the use of one of several postharvest tenderization procedures. Moisture-enhanced pork is accepted by consumers and often sells for a premium; and moisture enhancement may be appropriate for CLPG lamb. The meat cost per kilogram (including a $.10 per kilogram treatment cost) of tenderized and moisture-enhanced CLPG leg, loin, rack, and shoulder containing 10% added water and ingredients would be lowered to $2.51, $4.65, $5.34, and $1.85, respectively. That represents a total of a 20.9% reduction in cost-basis price. When expressed on the basis of increased revenue from the additional yield of cuts at a given market price, the value of CLPG and moisture-enhanced CLPG cuts from a 59-kg lamb would be, respectively, 14.2% and 23.4% higher than for N lamb. Industrywide adoption of CLPG could increase intermediate-run U.S. profits by $109 million, but the actual effects of CLPG attributes, such as a visual appeal, lower fat and cholesterol content, and reduced seam fat, on consumer demand need to be quantified. If accepted by packers and consumers, moisture-enhanced CLPG lamb has the potential to decrease the cost of lamb to consumers and increase lamb industry profitability.

Animals↗

PubMed1998

Effect of freezing on calpastatin activity and tenderness of callipyge lamb.

The longissimus muscles (LM) from 12 lambs (eight = callipyge [CLPG] and four = normal [NML]; 48 kg) were used to 1) assess the effect of freezing with or without prior immersion in liquid nitrogen on calpastatin activity (CA) and on Warner-Bratzler shear force (WBS) in CLPG, 2) determine the freezing time required to reduce CA and WBS of CLPG to that of NML, and 3) compare sensory panel ratings for CLPG that is aged fresh to CLPG that is aged after freezing. At 24 h postmortem, chops (.64 and 2.54 cm) were removed from each CLPG LM and randomly assigned within side to one of six freezing times (0, 2, 4, 8, 20, and 42 d). Left-side chops were vacuum-packaged and frozen at -20 degrees C for the assigned time (FROZEN) and right-side chops were treated similarly, except that they were frozen in liquid nitrogen first (FLASH). After freezing for the assigned time, the .64-cm chop was immediately assayed for CA, and 2.54-cm chop was thawed, aged at 2 degrees C for 14 d, and refrozen for subsequent WBS measurement. Chops (.64 and 2.54 cm) were also removed from the longissimus of NML lamb carcasses. The d-0 CLPG and NML chops (2.54 cm) were vacuum-packaged, aged at 2 degrees C for 14 d, and frozen for subsequent WBS measurement. Calpastatin activity did not differ between freezing treatments (P = .99) or with the freezing treatment x freezing time interaction (P = .80). Freezing reduced (P = .01) CA in CLPG by 44% from d 0 to d 42. Calpastatin activity for CLPG was similar (P > .05) to that of NML lamb after freezing for 8, 20, or 42 d. Freezing at -20 degrees C for 42 d and then aging for 14 d reduced (P = .01) WBS in CLPG by 44% from d-0 values. Shear force values for CLPG-FROZEN were similar (P > .05) to NML after 8, 20, or 42 d of freezing. Sensory panel tenderness scores were higher (P < .05) for CLPG aged after freezing 42 d than for those aged fresh. Juiciness and flavor ratings did not differ (P > .05) between CLPG aged fresh or after freezing. Freezing for at least 8 d before aging seems to be a viable method for increasing the tenderness of CLPG LM without reducing juiciness or flavor ratings.

Adult↗

PubMed1996

Polar overdominance at the ovine callipyge locus.

An inheritable muscular hypertrophy was recently described in sheep and shown to be determined by the callipyge gene mapped to ovine chromosome 18. Here, the callipyge phenotype was found to be characterized by a nonmendelian inheritance pattern, referred to as polar overdominance, where only heterozygous individuals having inherited the callipyge mutation from their sire express the phenotype. The possible role of parental imprinting in the determinism of polar overdominance is envisaged.

Animals↗

PubMed1996

Collagen crosslinks in longissimus muscle from lambs expressing the callipyge gene.

The objective of this study was to determine whether increased amounts of collagen and (or) hydroxylysylpyridinoline crosslinks in longissimus muscle are partially responsible for decreased tenderness when callipyge lambs are compared to normal lambs. The longissimus muscle was used because we believe tenderness is a greater problem in loin chops of callipyge lambs than it is in other cuts. Ten normal and 10 half-sibling lambs expressing the callipyge gene were compared. Lambs were slaughtered at approximately 8 mo of age when they reached a target weight of 59 kg. Dressing percentages were higher for the leaner callipyge lambs that exhibited larger longissimus muscle areas and heavier leg weights (P < .01). Warner-Bratzler shear values for longissimus muscle from callipyge lambs were higher (P < .01) than those from normal lambs. The higher shear values were not explained by amount of muscle collagen or by hydroxylysylpyridinoline crosslink concentration because both collagen percentage (P < .09) and crosslink concentration (P < .04) were lower in callipyge lambs. Therefore, attempts to modify shear values and make loin chops from callipyge lambs more acceptable to consumers should focus on the myofibrillar fraction of muscle.

Amino Acids↗

PubMed1996

Histology and composition of muscles from normal and callipyge lambs.

The histology and composition of muscles from normal (n = 10) and callipyge (n = 11) wether lambs was compared. Normal Rambouillet ewes were mated with callipyge Dorset rams, and their progeny were visually classified as callipyge or normal based on muscle definition in the loin and hind quarters. The muscles examined included three muscles that hypertrophy in callipyge lambs (semitendinosus, longissimus, and gluteus medius) and one muscle believed not to hypertrophy (supraspinatus). The hypertrophy-responsive muscles from callipyge lambs had a higher (P < .001) percentage of fast-twitch glycolytic (FG) fibers and lower (P < .001; P < .02 for SO in gluteus medius) percentages of slow-twitch oxidative (SO) and fast-twitch oxidative glycolytic (FOG) fibers. The diameters of the FG and FOG fibers were larger (P < .005 and P < .04, respectively) in hypertrophy-responsive muscles from callipyge lambs, but the SO fiber diameter was smaller (P < .05). Also, the protein:DNA ratio, an indicator of cell size, was greater (semitendinosus, P < .05); longissimus, P < .002; gluteus medius, P < .008) in the hypertrophy-responsive muscles from callipyge lambs. Thus, hypertrophy in callipyge lambs was, at least in part, due to fiber type changes and muscle cell enlargement. Hypertrophy was strongly associated with changes in the FG fibers, the only fiber type that increased in both proportion and average diameter in callipyge muscles. The protein:RNA ratio and RNA:DNA ratio, which are indicators of translational and transcriptional activity in the muscle cells, were not different between callipyge and normal muscles. This indicated that the accumulation of protein necessary for myofiber enlargement occurred without differences in the translational or transcriptional activity of callipyge muscle.

Animals↗

PubMed1996

Prediction of live lamb chemical composition utilizing electromagnetic scanning (ToBEC).

Electromagnetic scanning was investigated to determine its accuracy in predicting chemical composition in live lambs. Forty-seven Rambouillet wether lambs were scanned with an electromagnetic instrument (ToBEC Model HA-2). Lambs were serially scanned and slaughtered over the weight range of 29.5 to 63.5 kg. Each lamb was scanned twice: before and immediately after 24 h of food deprivation. Chemical composition was determined from whole-animal ground samples by AOAC methods for percentage of DM, CP, ether extract (EE), and Ash. Percentage of fat-free mass (FFM) was calculated from the percentage of moisture and CP. Correlation and stepwise regression procedures were used to identify the most reliable independent variables for predicting chemical composition. Independent variables included electromagnetic scan data and live animal measures for weight, body length, and chest girth circumference. Electromagnetic data included the average scan response curve (PH0) and Fourier transformations (P1T, P1R, P2T, and P2R). Repeatability of the HA-2 model was extremely high (r = .98). Reliable prediction equations were obtained for DM, CP, EE, and FFM (R2 > .66). The percentage of ash could not be predicted from the independent variables. Electromagnetic scan responses contributed little to the model sum of squares. Body weight accounted for the majority of the model sum of squares. Depriving lambs of food for 24 h slightly improved the R2 value and significantly decreased scan responses (P < .01). Body weight was a better predictor of chemical composition over a large weight range than any of the scan responses. Further investigation of the HA-2 is needed to determine whether it is effective in determining differences in live body composition between animals of equal weight.

Animals↗

PubMed1995

Collagen characteristics of skin, fell, and epimysium from rams, wethers, and zeranol-implanted ram lambs.

Eighteen spring-born Columbia ram, wether, and zeranol-implanted ram lambs were examined to determine the influence of castration or zeranol implantation on collagen characteristics of skin, fell, and epimysium and possible relationships between collagen properties of each tissue and difficulty of pelt removal. Pelt removal force was lower in wethers than in rams (P < .05) and intermediate for zeranol-implanted rams. Collagen concentration in skin of rams was greater (P < .05) than that in wethers or implanted rams, but percentage of heat-soluble collagen in skin was higher in implanted rams. Percentage of type III collagen in skin was highest in rams and lowest in wethers (P < .05); that in the skin of implanted rams was intermediate. The fell of wethers contained a higher (P < .05) collagen concentration, higher insoluble collagen amount, and lower percentage of soluble collagen than that of rams or implanted rams. The fell had a lower percentage of type III collagen than that of rams (P < .05). Epimysium collagen concentration of rams and wethers was higher (P < .05) than that of implanted rams; however, percentage of soluble collagen was higher for the implanted rams than for the other classes. Type III collagen percentage in the epimysium did not differ by animal class (P < .05). Zeranol-implanted ram lambs had a higher percentage of soluble collagen in all tissues examined than did non-implanted rams and force required for pelt removal was reduced in implanted rams.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Production by ewes rearing single or twin lambs: effects of dietary crude protein percentage and supplemental zinc methionine.

Eighty Targhee ewes with single or twin lambs were used to investigate the effects of chelated zinc methionine and level of dietary CP on milk and wool production, DMI, and ewe and lamb BW change. Treatments were arranged as a 2 x 2 x 2 factorial. Dietary treatments started 30 d prepartum and continued until 42 d postpartum. Milk production was estimated at 4, 10, 18, and 28 d postpartum. During gestation, DMI by ewes receiving zinc methionine and the 14.9% CP diet was greater (P < .10) than DMI by ewes not supplemented with zinc methionine and ewes fed the 11.3% CP diet. Ewes fed the 14.9% CP diet tended (P < .14) to gain more BW from 30 d prepartum to 4 d postpartum and lose more BW from 4 to 42 d postpartum than ewes fed the 11.3% CP diet. Ewes fed zinc methionine and the 14.9% CP diet produced more (P < .10) milk on d 28 than their counterparts. Ewes rearing twins produced more (P < .05) milk on d 4, 10, and 18 than ewes rearing single lambs. However, milk production on d 28 was not affected by number of lambs reared (P = .68). Lamb ADG at 28, 42, and 59 d postpartum was greater (P < .05) for both the zinc methionine treatment and the 14.9% CP diet. Zinc methionine (P = .11) and the 14.9% CP diet (P = .02) increased weaning weights by 6 and 9%, respectively. We conclude that both the zinc methionine supplement and the 14.9% CP diet resulted in more persistent milk production. In addition, when ewes and lambs were fed for an average of 42 d during early lactation, a 14.9% CP diet, and to a lesser degree, a chelated zinc methionine supplement, lamb weaning weights were improved.

Animal Nutritional Physiological Phenomena↗

PubMed1995

Breed effects of foster lamb and foster dam on lamb viability and growth.

The objective of this study was to compare maternal ability under natural and fostered rearing conditions in four breeds of sheep for lamb survival and growth to weaning age. Data included records from 1981 through 1991 of 24,696 lambs of four breeds, Rambouillet, Columbia, Targhee, and Polypay, reared by their natural dam, and 720 records of lambs fostered within their breed or across breeds. The majority (94%) of the foster lambs were from multiple-birth litters and were approximately .5 kg lighter than lambs reared by their natural dams (P < .05). Viability up to 3 wk of age was influenced by breed of foster dam; lambs reared by Polypay dams had the highest viability (96%) and lambs reared by Targhee dams the lowest (81%). Targhee dams were less successful in rearing foster lambs (75%) to weaning than the other breeds studied (average 84%). The lower viability of Targhee-reared foster lambs could not be explained by lower birth weights of foster lambs, increased starvation, or lower milk scores for Targhee dams. Although there were breed differences in weaning weights at 120 d of age, the foster lambs were lighter but the ranking by breed did not change. These results suggest that there are small breed differences in maternal ability for a ewe to raise her own lamb or foster lamb(s), except for the Targhee ewe, which has a lower success in rearing a foster lamb. Management practices to reduce the mortality rate of foster lambs should be investigated.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1994

Maternal factors associated with prenatal transmission of ovine lentivirus.

Prenatal transmission of ovine lentivirus (OvLV) was studied in 85 eyes and their offspring. The animals were from a flock with endemic OvLV infection and 49 (58%) had serum antibodies to OvLV. Blood was collected from all lambs before they nursed. Using the polymerase chain reaction (PCR), OvLV DNA was detected in peripheral blood mononuclear cells of 13 (11%) of 117 lambs, including two sets of twins. Mothers with OvLV-infected lambs (n = 11) were younger (mean, 2.5 years) and had fewer pregnancies (mean, 2.4) than seropositive ewes (3.2 years and 3.2 pregnancies; P < .05). Of mothers with OvLV-positive lambs, 4 had plasma antigenemia (mean, 31.3 +/- 2.1 ng/mL OvLV) in conjunction with indeterminate antiviral antibody responses by immunoblotting. These results suggest that maternal factors (age and parity) and host-virus interactions (antiviral antibody and antigenemia) are important risk factors in prenatal transmission of OvLV.

Age Factors↗

PubMed1994

Carcass characteristics and optimal slaughter weights in four breeds of sheep.

Wether lambs from four breeds, Rambouillet (n = 38), Targhee (46), Columbia (38), and Polypay (38), were used to estimate an optimal slaughter weight for lean lamb production. Wethers, weaned at an average of 105 d of age and 38.5 kg, had ad libitum access to a finishing diet of 85% barley grain and 15% pelleted alfalfa and were slaughtered at weights ranging from 39 to 70 kg. Fat, protein, moisture, and ash percentages were determined on fat and lean from 7-rib racks. Optimal slaughter weight was estimated by using carcass backfat depth or extracted fat in the rack as dependent variables in linear equations. An acceptable lean lamb carcass was defined to have 2.5 to 6.5 mm of backfat depth and 26 to 40% rack chemical fat. On a weight-constant basis Columbia lambs were less physiologically mature than the other breeds, having less (P < .05) kidney and pelvic fat and a lower rack fat percentage. Targhee, Rambouillet, and Polypay wethers were similar in carcass fat and protein composition at a constant slaughter weight. Optimal slaughter weights for certified lean lamb carcasses of Targhee, Rambouillet, and Polypay wethers were 45 to 47 kg, resulting in a Choice quality grade and a 2.7 yield grade. The optimal weight for Columbia was heavier, between 45 and 55 kg, producing a Choice quality grade and a 2.4 yield grade. The derived optimal slaughter weights are limited to the populations sampled and may not be specific to other populations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Host-virus interaction as defined by amplification of viral DNA and serology in lentivirus-infected sheep.

To correlate the presence of ovine lentivirus (OvLV) as detected by polymerase chain reaction (PCR) with detection of antibody, 42 sheep from a flock with enzootic OvLV infection were studied. The results of agar gel immunodiffusion (AGID), ELISA, and immunoblotting assays were compared, and leukocytes (blood, bone marrow, lymph node, and lung cells) were assessed for viral DNA by PCR using pol and LTR primers; amplified products were detected by specific DNA and RNA probes. Based on the number of animals that had detectable viral DNA, the specificities of AGID, ELISA, and immunoblotting were 77%, 92%, and 95 or 100% (depending on which criterion was used to interpret immunoblot results), respectively. Only in animals with OvLV-associated disease was OvLV DNA detected in leukocyte DNA prior to the amplification of virus in culture and only in this group was high titer antibody detected to the OvLV major surface (gp 105) and transmembrane (gp 55) antigens. Animals that were both antibody and PCR-negative lacked histopathologic evidence of disease. From this study there was no indication that OvLV infection without the development of antibody occurs, and detection of OvLV DNA in animals with weak or partial serological reactions likely indicates early OvLV infection rather than false-positive PCR results.

Animals↗