Ewe Fleece Weight Research Articles

Predicting ewe body condition score using adjusted liveweight for conceptus and fleece weight, height at withers, and previous body condition score record.

The relationship between ewe body condition score (BCS) and liveweight (LW) has been exploited previously to predict the former from LW, LW-change, and previous BCS records. It was hypothesized that if fleece weight and conceptus-free liveweight and LW-change, and in addition, height at withers were used, the accuracy of current approaches to predicting BCS would be enhanced. Ewes born in 2017 (n = 429) were followed from 8 mo to approximately 42 mo of age in New Zealand. Individual ewe data were collected on LW and BCS at different stages of the annual production cycle (i.e., prebreeding, at pregnancy diagnosis, prelambing, and weaning). Additionally, individual lambing dates, ewe fleece weight, and height at withers data were collected. Linear regression models were fitted to predict current BCS at each ewe age and stage of the annual production cycle using two LW-based models, namely, unadjusted for conceptus weight and fleece weight (LW alone1) and adjusted (LW alone2) models. Furthermore, another two models based on a combination of LW, LW-change, previous BCS, and height at withers (combined models), namely, unadjusted (combined1) and adjusted for conceptus and fleece weight (combined2), were fitted. Combined models gave more accurate (with lower root mean square error: RMSE) BCS predictions than models based on LW records alone. However, applying adjusted models did not improve BCS prediction accuracy (or reduce RMSE) or improve model goodness of fit (R2) (P > 0.05). Furthermore, in all models, both LW-alone and combined models, a great proportion of variability in BCS, could not be accounted for (0.25 ≥ R2 ≥ 0.83) and there was substantial prediction error (0.33 BCS ≥ RMSE ≥ 0.49 BCS) across age groups and stages of the annual production cycle and over time (years). Therefore, using additional ewe data which allowed for the correction of LW for fleece and conceptus weight and using height at withers as an additional predictor did not improve model accuracy. In fact, the findings suggest that adjusting LW data for conceptus and fleece weight offer no additional value to the BCS prediction models based on LW. Therefore, additional research to identify alternative methodologies to account for individual animal variability is still needed.

Broadening breeding objectives for maternal and terminal sheep

Economic values have been calculated and selection indexes defined for maternal and terminal traits for sheep in New Zealand. Using trait-by-trait bio-economic models, economic weights (EW), in $ per lamb born per genetic standard deviation in the trait for maternal and terminal sire performance traits respectively, have been calculated. The EW after accounting for the genetic standard deviation for the traits in the base maternal index were; $1.49 for weaning weight direct, $0.93 for weaning weight maternal, $2.86 for carcase weight, −$1.54 for ewe mature weight, $0.14 for lamb fleece weight, $0.23 for one-year-old replacement fleece weight, $0.77 for ewe fleece weight, and $2.80 for number of lambs born. For those traits not in the base maternal index, EWs ranged from $0 to $0.66 for lean and fat yield traits, $0.53 to $1.12 for one-year-old dam reproductive performance traits, $2.34 to $2.58 for lamb survival traits, −$1.11 to −$0.94 for faecal egg count traits, −$0.38 to $0.09 for resilience traits, −$0.40 to −$0.27 for dag score traits, and −$0.91 to −$0.35 for facial eczema traits. The EW for twinning rate was $1.45. For traits in the base terminal index trait EWs were $1.07 for weaning weight direct, $2.14 for carcase weight, $0.21 for shoulder lean yield, $0.52 for leg lean yield, $0.50 for loin lean yield, −$3.74 for fat yield, and $1.83 for lamb survival direct. For traits not in the base terminal index, faecal egg count EWs ranged from −$0.79 to −$0.69, and the EW for lamb dag score was −$0.11. The inclusion of a wide range of traits in indexes for terminal and maternal sires spanning production, lambing, maternal, and health traits increases the scope by which breeders and commercial farmers alike can assess the suitability of selection candidates for target end use of the progeny. Although the genetic variation in merit of additional traits when compared to those in the base indexes does not have such a large impact as growth and reproduction (maternal) and yield (terminal), their inclusion represents an opportunity for farmers to further optimise animal performance and to define a market difference for the genotype they are developing with their breeding programme.

Evaluation of sheep genetic resources in North America: Ewe productivity of purebred, crossbred and synthetic populations

Ewe productivity from divergent genetic types of established purebreds e.g., Dorset (D), Lincoln (L), Rambouillet (Ra), Suffolk (Su) and Targhee (T); fecund-type breeds e.g., Finnsheep (F) and Romanov (Ro) breeds, and their reciprocal crosses; the Outaouais (O) and Rideau (R) Arcott breeds and their reciprocal crosses; and Synthetic I (½ F, ½ L), Synthetic II (½ D, ½ Ra) and Synthetic III (¼ F, ¼ L, ¼ D, ¼ Ra) populations were evaluated. Prolificacy, fecundity, ewe weight, grease fleece weight, wool grade, lamb survival and total lamb weights at birth, 30 d and 140 d per ewe lambing were considered jointly as a measure of ewe productivity. In general, fecund-type breed cross and Arcott breed cross were highest in productivity, the fecund-type breed, Arcott breed and synthetic populations were intermediate, in contrast the established breeds was lowest. Regardless of significantly heavier ewe and grease fleece weights, and superior wool grade of the established breeds, their poor performance can be attributed to lower prolificacy, fecundity and total lamb weights (P < 0.05). Within established breeds, the D, L, Ra and T breeds were comparable in productivity to the Su breed, but lower than the F breed (P < 0.05). The Ro breed surpassed the F breed because of significantly higher prolificacy and fecundity, and heavier ewe weight and total lamb weights, while grease fleece weight and wool grade were inconsistent. The F and Ro breeds were comparable to the Su breed despite significantly higher prolificacy and fecundity, in contrast to lighter ewe and grease fleece weights, lower wool grade, lamb survival, similar total lamb weights. Although the R breed produced significantly heavier grease fleece weight and total lamb weights than the O breed, both breeds were similar to the Su breed despite their significantly higher prolificacy and fecundity, in contrast to similar ewe weight, wool grade, lamb survival and total lamb weights, and lighter grease fleece weight. The O and R breeds were more productive than the F breed as a result of significantly heavier ewe weight, superior wool grade, higher lamb survival and heavier total lamb weights, despite their similar prolificacy, fecundity and grease fleece weight. Synthetic I and Synthetic III with Finnsheep lineage surpassed Synthetic II in productivity as a result of significantly higher prolificacy and fecundity, and heavier total lamb weights, despite similar ewe and grease fleece weights and inconsistent wool grade and lamb survival. At the same time, Synthetic I and Synthetic III were not only similar to the Su breed, but surpassed the F breed, whereas Synthetic II was similar to the Su breed and lower than the F breed. Finally, systematic crossbreeding and composite population of complementary fecund-type and established breeds achieved increased productivity from additive genetic variation and heterosis. Key words: Reproductive performance, ewe and grease fleece weights, total lamb weights, Arcotts, Finnsheep, Romanov, synthetic populations, established breeds

The Norwegian sheep breeding scheme: description, genetic and phenotypic change

The developments in Norwegian sheep breeding since the early 1990s are reviewed. For the largest breeding population, the Norwegian White Sheep, results are presented for both genetic and phenotypic changes. Of the nine traits that make up the aggregate genotype, the largest gain per year, in per cent of the corresponding phenotypic average, was found for carcass grade (1.66%) and carcass weight (0.99%), number of lambs born at 1, 2 and 3 years of age (0.32% to 0.60%) and the maternal effect on weaning weight (0.26%). For fat grade, a genetic deterioration was estimated. This may be due to the too small weighting of this trait in the aggregate genotype and the true genetic parameters being somewhat different from the estimates in the prediction of breeding values. For lamb as well as ewe fleece weight, genetic change was close to zero – interpreted as mainly a correlated response to other traits in the aggregate genotype. Data for the two traits of fleece weight were, respectively, selected and few. Thus, phenotypic change was calculated for all traits except for fleece weight, and in addition for number of lambs at weaning, being indirectly selected for through number of lambs born. For all traits, with the exception of fat grade, advantageous phenotypic change was estimated. For weaning and carcass weight, the phenotypic change was less than the genetic change, while the opposite was observed for carcass and fat grade and number of lambs born. The latter traits can be more easily controlled by environmental actions, and the results thus exemplify the interdependency between environmental and genetic change.

Selection for high or low backfat depth in Coopworth sheep: breeding-ewe traits

AbstractA breeding experiment in Coopworth sheep where selection was applied to backfat depth was evaluated after 14 years (1981-94). There were three self-replacing lines, two selected for increased or decreased subcutaneous fat depth, and an unselected control (average size = 51 ewes per line per year). Reproductive traits, ewe body weight and ewe fleece weight were monitored in each line as potential correlated responses. In the last 4 years studied, the fat (F), control (C) and lean (L) lines differed significantly in the proportion of ewes lambing (0·87, 0·93, 0·94 respectively), litter size at birth (1·64, 1·83 and 1·89), and lamb survival up to weaning, unadjusted for birth rank and sex (0·88, 0·81 and 0·74). The overall reproductive trait, lambs weaned per ewe joined (1·22, 1·33 and 1·26), did not differ significantly among lines. From pre-mating weights of ewes present in 1993 or 1994, means for mature ewes by line were 60·1, 62·4 and 63·3 kg, respectively (P < 0·01). Means for weight at scanning time (7 months of age) by line, as a proportion of mature weight were: 0·533, 0·561 and 0·559, respectively (P < 0·05). There were also significant line differences in ewe fleece weights, with the 1993 and 1994 data averaging 3·93, 4·05 and 4·27 kg respectively (P < 0·01). For weight of lamb weaned per ewe weaning at least one lamb, the L line had a 0·09 higher mean proportionally than the F line (P < 0·05), but for a composite trait which was a weighted combination of weight of lambs weaned and ewe fleece weight per ewe joined (with or without allowance for different ewe live weights), the L line was no longer significantly different from the F line. Repeatabilities and single-record heritabilities were also estimated for various ewe traits. The implications are that lean-lamb selection would be associated with only small changes in net reproduction, ewe fleece weight and live weight, but larger differences would be expected from selection in the opposite direction.

Tactical versus continuous stocking in perennial ryegrass-subterranean clover pastures grazed by sheep in south-western Victoria. 3. Herbage nutritive characteristics and animal production

A 4-year grazing experiment was carried out in south-western Victoria to compare the effect of tactical stocking with continuous stocking on the persistence of perennial ryegrass (Lolium perenne L.) and the productivity of sheep used for prime lamb production. Tactical stocking consisted of variable length summer, autumn and winter rotations and continuous stocking in spring. The 2 grazing strategies were compared on 2 contrasting pastures: an upgraded pasture, sown with newer cultivars of perennial ryegrass and subterranean clover (Trifolium subterraneum L.) with 26 kg phosphorus/ha.year, and a naturalised perennial ryegrass pasture receiving 6 kg phosphorus/ha.year. Paddocks were grazed by Border Leicester x Merino ewes, which were mated to a terminal sire to lamb in September. In this final paper of the series, the effects of the grazing systems and pasture treatments on animal production and herbage quality are presented. The liveweights of the ewes were similar across all treatments during autumn and winter, but the tactically stocked ewes were 3–6 kg lighter than continuously stocked ewes during spring and summer. The lower liveweight was attributed to the lower (P<0.001) herbage quality on the tactically stocked pastures in spring (P<0.001). Both digestibility and crude protein concentration were about 4 percentage units lower with tactical stocking in spring. This lower quality was associated with the higher herbage mass (by 500–900 kg dry matter/ha) on the tactically stocked pastures, which presumably had a higher stem:leaf ratio and showed reproductive growth earlier than the continuously stocked pastures. Although there were differences in ewe liveweight, this did not affect individual lamb weaning weight or ewe fleece weight. There were significant increases in production per hectare from tactically stocked or upgraded pasture treatments due to the higher stocking rates that could be carried, 9 and 51%, respectively. In 1998, 544 kilograms of lamb per hectare was weaned from continuously stocked paddocks and 607 kg/ha from tactically stocked paddocks (P<0.05), and 449 and 702 kg/ha from the typical and upgraded pastures, respectively. This study reinforces the view that soil fertility and pasture improvement have a much greater impact on animal productivity than changes to grazing method with little effect on per head productivity. The negative impact of rotational stocking on herbage quality reinforces the need to use these systems strategically when benefits from increased herbage mass are expected to increase animal production or overcome sustainability or pasture persistence problems.

Environmental effects on growth traits and fleece weights in Baluchi sheep

SummaryData from 20 249 Baluchi lambs, recorded from 1966 to 1989 in the Abbasabad Sheep Breeding Station located in the north‐east of Iran (Mashhad), were used to investigate the influences of environmental factors, multiplicative and additive adjustment factors for lamb weights at birth (BW), weaning (WW), six month (W6) and 12 months (YW) of age, preweaning (WG) and postweaning (PWG) gains, lamb fleece weight (LFW) and ewe fleece weight before first mating (FW1). Significant effects of flock, year, sex, birth‐rearing type and parity of ewe were observed for lamb weight at different ages and weight gains. Male lambs were heavier than females and the difference between them increased with age of lamb. The ratio of single lamb weight (S–S) to twin birth and single rearing (Tw–S) and twin birth and twin rearing (Tw–Tw) decreased with advancing age of lamb. Lambs born at parity 4–6 were heavier than lambs of younger or older ewes. Weight gain declined in all subclasses from weaning to 12 months of age. The effects of flock and year were significant for lamb and ewe fleece weights. In addition the effect of sex was significant for LFW. Based on a test of heterogeneity of variance among class levels of fixed effects, multiplicative adjustment of sex, type of birth and parity of ewe for BW, and the effects of sex and parity of ewe for lamb weight at other ages were recommended. For LFW the effect of sex should be considered for multiplicative adjustment. Due to homogeneous variances, the additive adjustment for effect of birth‐rearing type should be considered for WW, W6 and YW.

Genetic parameters for lamb weight at different ages and wool production in Baluchi sheep

AbstractThe Baluchi breed is the most common native breed of Iran adapted to harsh environments in the eastern parts of the country. The data used in the present study, collected from two research flocks at the Abbasabad sheep breeding station in north-east Iran, included 20 534 animals descended from 363 sires, 5992 dams, 282 maternal grandsires, and 2865 maternal granddams during the period 1966 to 1989. The traits recorded were: birth weight (BW), weaning weight (WW), weight at 6 months (W6), weight at 12 months (YW), pre-weaning gain (WG), post-weaning gain (PWG), lamb fleece weight (LFW), ewe fleece weight sheared before first joining (FW1) and adult ewe fleece weight (FW). Genetic parameters, estimated with restricted maximum likelihood and a two-trait animal model, were similar in the two flocks. Direct heritabilities for the various body weight traits were moderate and varied between 0·13 and 0·32, while the maternal heritabilities were low and varied between 0·01 and 0·12. Direct and maternal genetic correlations between WW and weights at later ages were moderate to high (0·59 to 0·96). Direct heritabilities of weight gain measures varied between 0·12 and 0·19, while no significant maternal influence on either of these weight gain measures could be detected. The estimates of direct genetic correlation between WG and PWG were positive and varied between 0·54 and 0·74, while negative maternal genetic correlation (0·17 on average) between WG and PWG was detected. For LFW, direct heritability was low and no maternal heritability could be shown. For FW1, both direct and maternal genetic influences were demonstrated (0·07 to 0·26). Direct genetic correlation between LFW and FW1 was very low and close to zero, while maternal genetic correlation was positive and relatively high (0·72 on average). The relative contributions to phenotypic variance from variance components due to common environmental effects ranged from 0·01 to 0·15 for all traits. The repeatability of FW was low (0·03 to 0·12).

Population parameters for birth and ewe fleece weight at different parities in Baluchi sheep

ZUSAMMENFASSUNG: Populationsparameter für Geburts- und Vließgewicht von Baluchi Schafen Das Datenmarterial stammt von zwei Herden einer Schafzuchtstation in NO Iran aus den Jahren 1966-1989. Die Tiere waren unselektiert und stammten aus zufällig verteilten Paarungen. Es wurden Geburtsgewicht und Vließgewicht bei verschiedenen Altersstufen erhoben und Varianzkomponenten mittels Restringierter Maximaler Likelihood mit einem bivariaten Tiermodell mit fixen Wirkungen von Jahr, Geschlecht, Geburtstyp und Parität sowie Zufallswirkungen für additiven Genotyp des Lammes (direkt) und des Mutterschafes (maternal), gemeinsamer Umwelt (ausgenommen Vließgewicht) und Resteinfluß geschätzt. Direkte und maternale genetische Korrelationen zwischen Leistungen verschiedener Paritäten wurden berechnet. In Herde 1 scheinen Varianzen und Heritabilitätswerte für Lammgewicht bis Parität 5 zuzunehmen, kaum aber in Herde 2. Die durchschnittlichen Heritabilitätswerte, direkt, maternal und gesamt waren 0.12, 0.11 und 0.26, die genetische Korrelation zwischen direkten und maternalen Wirkungen 0.42. Bei Vließgewicht waren in Herde 1 keine Veränderungen der Varianzen und Heritabilitätswerte mit Alter zu erkennen, aber bei Herde 2 nahmen phänotypische und Umweltvarianz mit Alter leicht zu. Durchschnittliche direkte, maternale und Gesamtheritabilität waren 0.19, 0.04 und 0.22, die genetische Korrelation zwischen direkten und maternalen Wirkungen geringgradig positiv in Herde 1, aber mit Alter zunehmend negativ in Herde 2. Die genetischen Korrelationen für direkte Wirkungen auf Geburtsgewicht waren hoch zwischen Paritäten 1 bis 5, aber niedriger bei Parität 6 und jene zwischen maternal bedingten Wirkungen zeigten ähnliche Trends. In Herde 2 waren Werte mit Parität 6 ähnlich wie die zwischen den übrigen Paritäten. Die die Vließgewichte betreffenden direkt genetischen Korrelationen zwischen Paritäten waren in beiden Herden ähnlich (0.73-0.92), jene, die maternale Wirkungen betreffen, deutlich geringer, besonders soweit sie Paritäten 5 und 6 betroffen haben und zeigten besonders bei Herde 2 starke Schwankungen (-0.54 bis 0.74). Direct and maternal performance of ewes at different parities were examined in Baluchi sheep. The data set was collected during the period 1966-1989 from two flocks at a sheep breeding station in the north-east of Iran. The animals included in the data set were unselected and randomly mated. The traits analysed were birth weight of lamb and fleece weight at different parities of the ewe. Variance components were estimated using Restricted Maximum Likelihood with a bivariate animal model including fixed effects of year, sex, type of birth and parity, and random effects of additive genotype of lamb (direct genetic effect), additive genotype of ewe (maternal genetic effect) and common environment (excluded for ewe fleece weight), and random residual effect. Direct and maternal genetic correlations between different parities were estimated. There was evidence of increasing phenotypic and genetic variances and heritabilities from parity 5 for birth weight of lamb in flock 1, but only evidence of a slightly increasing age trend for the environmental and phenotypic variance in flock 2. The average heritabilities over flocks and parities were 0.12, 0.11 and 0.26 for the direct, maternal and total heritability, respectively, while the average genetic correlation between direct and maternal effects for this trait was 0.42. There were no indications of any age changes in variances or heritabilities for ewe fleece weight in flock 1, but indications of slightly increasing age trends for the environmental and phenotypic variance. The average heritabilities over flocks and parities were 0.19, 0.04 and 0.22 for the direct, maternal and total heritability, respectively, while the average genetic correlation between direct and maternal effects was slightly positive in flock 1 but increasingly negative with age of the ewe in flock 2. Direct genetic correlations between parities 1-5 were very high for birth weight of lambs (on average 0.96) in contrast to the markedly lower correlations of parities 1-5 with parity 6 (on average 0.67) in flock 1 with a similar pattern for the maternal genetic correlations. In flock 2, these correlations were also high but without the marked decrease between parities 1-5 with parity 6 that was found in flock 1. Direct genetic correlations between the various parities for ewe fleece weight were similar for the two flocks, ranging from 0.73 to 0.92 and without any obvious differences between the various combinations of parities. However, the maternal were markedly lower than the direct genetic correlations, especially for the combinations of parity 5 and 6 with the earlier parities, and most pronounced in flock 2 fluctuating from -0.54 to 0.79. To obtain reliable estimates of breeding values for birth weight of lamb, it is recommended that the prediction should include not only earlier but also later parities (ages) of the ewe.

Lifetime lamb and wool production of targhee or Finn-Dorset-Targhee ewes managed as farm or range flock: I. Average annual ewe performance.

Lifetime (5 yr) lamb production and wool production from 207 straightbred Targhee (T) and 474 1/4 Finn-1/4 Dorset-1/2 Targhee (FDT) crossbred ewes managed in a range or farm flock system were evaluated for ewe fertility, prolificacy, ewe fleece weight, and total lamb weight weaned per ewe exposed. Data included 2,620 ewe exposures, 2,384 parturitions, 4,638 lambs born, and 3,498 lambs weaned. Ewes were born in 1984 through 1987 and lambed the first time as 2-yr-olds. Expressed as mean annual values, ewe fertility rates were similar (92.2 vs 91.0%, P = .30) for FDT and T ewes. Finn-Dorset-Targhee ewes had higher (P < .001) prolificacy (2.11 vs 1.75), weaned more lambs per ewe exposed (1.41 vs 1.18), produced more total lamb weight weaned per ewe exposed (33.8 vs 29.9 kg), and lambed 2 d earlier than T ewes. Targhee ewes produced more (P < .001) wool (4.5 vs 3.5 kg) than FDT ewes. Range flock ewes had a higher (P < .001) fertility rate (94.5 vs 88.7%), higher number of lambs weaned per ewe exposed (1.38 vs 1.22), and higher total lamb weight weaned per ewe exposed (34.7 vs 29.0 kg) than farm flock ewes. Farm flock ewes had a higher (P < .001) prolificacy (2.00 vs 1.86) and produced more wool (4.2 vs 3.8 kg) than range flock ewes. Targhee ewes had heavier lambs at birth (5.2 vs 4.6 kg; P < .001) and at weaning (25.8 vs 25.4 kg; P < .05). Range flock lambs were heavier (P < .001) at weaning than farm flock lambs (26.2 vs 24.9 kg). Lambs from FDT dams had a higher (P < .01) survival rate than lambs from T dams (75.6 vs 71.4%). Lamb survival from birth to weaning was higher (P < .001) for range flock lambs than for farm flock lambs (76.6 vs 70.4%). Incorporation of Finnsheep and Dorset breeding increased the reproductive performance in both management systems but decreased wool production.

Supplementation of high fecundity Border Leicester x Merino ewes with a high protein feed: its effect on lamb survival

Two hundred and fifty Border Leicester x Merino ewes (40% heterozygous for the Booroola Fec B gene) were used in an experiment, replicated over 2 years, to examine the effects of cottonseed meal-based supplementation on lamb survival, birth, marking and weaning weight, as well as, liveweight and fleece characteristics of ewes. From 50 to 100 days of pregnancy, half of the ewes were supplemented with 80 g/head.day. The supplemented group was then split according to litter size and, until 30 days after lambing, were offered pellets at 80, 160 and 220 g/head .day, respectively, for ewes bearing single, twin and triplet (or more) lambs. Over the 2 years, ewes averaged 2.11 lambs per parturition and supplementation significantly increased lamb survival to weaning (73 v. 58%) with no interaction with litter size. Although supplementation had a positive effect on birth weight of all but twins, the effects of supplementation on survival were independent of birth weight effects. Significant effects of year, sire breed and litter size on lamb survival and birth weight were also noted. No effects of supplementation were apparent on lamb growth while ewe age, sire breed, sex and rearing rank all significantly influenced growth rates. Ewe weights, fleece weights and staple strength were significantly influenced by year, ewe age and litter size but not by supplementation. These findings indicate the benefits to lamb survival of providing a 'bypass' protein supplement to high fecundity flocks even when ewes are grazing good quality pastures.

Application of a multiple-trait animal model for genetic evaluation of maternal and lamb traits in Norwegian sheep

AbstractA selection index for overall economic merit and five subindexes for maternal and lamb traits were constructed. For estimation of breeding values, two computer programs were developed. A multiple-trait animal model was programmed for the ewe traits including number of lambs born ofl-, 2- and 3-years-old ewes and ewe fleece weight of yearlings. In order to reduce the memory requirement, the lamb data (growth rate, carcass weight, carcass grade, fat% and lamb fleece iveight) were analysed by a reduced multiple-trait animal model including genetic maternal effect. Experiences with the computer programs in genetic evaluation of approximately 619 000 animals are presented. It is concluded that the models and computing strategy may be used for genetic evaluation in the national sheep breeding programme in Norway.Relative economic values for all traits were derived from a profit equation on a 3-year-old ewe basis. The sensitivity towards changed economic values urns found to be low. Further, the genetic change in the ewe traits of the Norwegian breeds has been estimated, and a significant improvement was found, which was two to four times higher in the ram circles than outside. For breeding rams, the genetic change for number of lambs born was estimated to be approximately 0·01 lambs per ewe and year.

Production of yearling Targhee or Finn-Dorset-Targhee ewes managed as a farm or range flock.

Production data from 681 yearling ewes were evaluated for the effect of ewe breed and management system on fertility, prolificacy, lamb birth weight, lamb survival, lamb weaning weight, ewe fleece weight, and total lamb weight weaned per ewe exposed. Two hundred seven straightbred Targhee (T) and 474 1/4 Finn-1/4 Dorset-1/2 Targhee (FDT) crossbred ewes managed in a range or farm flock system were included in this study. Ewes were born in 1984 through 1987 and lambed the first time as 2-yr-olds. The basic model included main effects of ewe breed and management system. Lamb sex was added to the model for birth and weaning weight analysis. The FDT ewes had higher (P < .05) fertility (95.3 vs 91.3%) and (P < .01) prolificacy (1.93 vs 1.45 lambs) than the T ewes. Targhee ewes had heavier (P < .01) lambs at birth (5.2 vs 4.0 kg) and weaning (26.1 vs 23.4 kg, P < .01) and produced more (P < .01) wool (3.8 vs 3.2 kg). Lamb survival was not different (P > .10) between the breeds or management systems. Although FDT lambs were lighter at weaning, FDT ewes weaned 5.8 kg more (P < .01) total lamb weight per ewe exposed than did the T ewes (34.7 vs 28.9 kg), because FDT weaned more (P < .01) lambs per ewe exposed (1.46 vs 1.09 lambs). Farm flock ewes were more prolific (1.73 vs 1.64 lambs, P < .05) and had heavier lamb birth weight (4.8 vs 4.4 kg, P < .01) than range flock ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of pre-mating nutrition on reproductive performance of Booroola Merino × South Australian Merino ewes

To investigate the effect of pre-mating nutritional status on the reproductive performance of ewes carrying the Booroola ( Fec B ) gene, Booroola Merino × South Australian Merino ewes heterozygous for the high fecundity gene ( Fec B Fec + ), were exposed to varying levels of nutrition 11 weeks before and 6 weeks during mating, and the reproductive performance and productivity were assessed. Liveweight varied from 44.0 to 55.2 kg for five nutritional treatments and mean ovulation rates varied from 2.62 to 3.01. The positive response of ovulation rate to improved nutrition was reflected in increases in litter size at days 40 and 80 of pregnancy, and at birth ( P < 0.05). There were no statistically significant differences between nutritional treatments for either the proportion of pregnant ewes of ewes mated or lamb survival. Differences between nutritional treatments for ovulation rate and litter size were not reflected in net reproductive efficiency (lambs weaned per ewe exposed). Lamb growth was not affected by varying the level of pre-mating nutrition of the ewe, although ewe fleece weight and wool quality (tenderness) were compromised.

Reproduction, growth and survival of Merino ewes and lambs in south-western Queensland and their response to trace element supplementation

The effects of cobalt (Co), selenium (Se), copper (Cu) and Co + Se + Cu plus manganese, iodine and zinc (All) supplements on the liveweight change, fleece weights, reproduction and survival of Merino ewes and their lambs were studied on 3 commercial properties (W, B and G) in south-western Queensland during 1978 and 1979. There was no significant effect of supplementation on ewe and lamb liveweights or ewe fleece weights in 1978 (723 mm rain). In 1979 (303 mm rain), ewes given Co and All supplements were significantly (P&lt;0.05) heavier than all other ewes at weaning, but lamb weaning weights were not improved by any supplements. Zinc and manganese may have only been effective for a short period following dosing. Weaner lambs given supplements of Co, Se and Co+Se had significantly (P&lt;0.05) higher greasy fleece weights (3.67 kg) than unsupplemented lambs (3.38 kg). In 1978, there was no significant effect of supplementation on reproductive rate. On property W, only 68% of maiden ewes successfully mated and this flock had a significantly (P&lt;0.05) higher rate of reproductive wastage (27%) than did flocks on properties B (12.5%) and G (16.5%). The mean liveweights of maiden ewes for properties W, B and G in this year were 39.1, 35.1 and 37.1 kg, respectively. In 1979, ewes given the All supplement had significantly (P&lt;0.05) lower overall rates of reproductive wastage (12.2%) than did ewes without supplement (30.2%). Supplementary treatments did not improve ewe or lamb survival. In 1978, ewe mortality between joining and weaning was significantly (P&lt;0.05) higher on property W (24.2%) than on property G (7.0%). In 1979, there were no significant effects of either age or property on ewe mortality between joining and weaning. Neither trace element supplementation to ewes nor the sex of the lamb had a significant effect on lamb survival between marking and weaning.

Effects of helminth infection on the pre-weaning production of ewes and lambs: comparison between safe and contaminated pasture.

Comparison was made of the performances of cross-bred ewes and their lambs on pastures of low helminth infectivity ("safe" pastures) or contaminated pastures and at high or low stocking rates. Ewes grazing the safe, but not the contaminated, pastures were given a single pre-lambing drench. The largest difference in parasite infection between treatments was the level of exposure of sheep to Trichostrongylus spp, which was negligible on the safe pastures. The effects of parasite control on lamb growth were significant only in twins during the last 2 months before weaning. However, 22% of lambs on contaminated plots became soiled in the breech area and 38% were flystruck, compared with 8% and 10% respectively for lambs on the safe pastures. Ewe bodyweight gains were greater at low than at high stocking rate and were not affected by the parasite control treatments; differences in breech soiling and fly strike were similar to those in the lambs. Most importantly the parasite treatment produced a highly significant effect on ewe fleece weight at weaning. Ewes drenched and lambing on the safe pastures produced an extra 0.43 kg of wool, calculated to represent an increase of at least 40% during this period at the low-level of parasitic infection.

Effects of lupin grain and type of cereal grain on the value of a hay supplement in the diet of lambing ewes during drought

Two flocks of Border Leicester x Merino ewes, due to lamb at different times (early or late winter), were fed drought rations of either wheat or oat grain, with or without lupin grain, and with or without hay, from 2 weeks before to 6 weeks after lambing. All ewes were offered an estimated 8.7 and 14.5 MJ ME/head.day when pregnant and lactating, respectively. Lupins, when included in the diet, replaced 25% of cereal grain ME; and hay replaced 14% and 20% of cereal grain ME for pregnant and lactating ewes, respectively. Treatment rations had no effect on liveweight or condition of the ewes. Effects on lamb birth weights, growth rate to 17 days, numbers weaned, ewe milk production after 29 days lactation and ewe fleece weights were as follows. Feeding oats, in comparison to wheat, improved growth rate (30 g/day), numbers weaned (16 per 100 ewes lambing) and fleece weight (90 g). Feeding lupins improved birth weight (0.2 kg), growth rate (20 g/day), numbers weaned (12 per 100 ewes lambing), milk production (18 ml/h) and fleece weight (70 g). Feeding hay improved growth rate (17 g/day) but decreased fleece weight (160 g). There were no interactions between treatments. Treatment rations did not affect fertility in the year following feeding.

Reproduction in ewe lambs and its effect on 2-year-old performance

Abstract Reproductive performance was studied in 1- and 2-year-old Romney and Border Leicester x Romney ewes. Control lambs were joined with vasectomised rams, and the remainder were joined with entire rams for 5 weeks. Fertility, growth rate, and weaning rate were higher in crossbred ewe lambs, and birth rank effects were small. Conception rate to first service was negatively related to liveweight gain over joining. Weaning rate (57% lambs weaned/ewe joined) was lower than normally expected from adult ewes. Lamb survival was improved in previously lambed 2-year-old ewes, whereas oestrous and ovarian activity, fertility, fecundity, and lamb growth were unaffected. Ewe liveweight and fleece weights were temporarily reduced. It is concluded that lambing in l-year-old ewes can enhance their reproductive performance as 2-year-olds.

Causes of variation in dental characters of Scottish Blackface sheep in a hill flock, and relations to ewe performance

SUMMARYObservations were made in three successive years on the dentition of Scottish Blackface ewes of 1½–4½ years old in a large hill flock in southern Scotland.The number of permanent incisor teeth was not a reliable guide to age, since at each age there was variation about the modal number. The length of the central permanent incisors increased slightly with age, and associated with this there was a slight forward movement in the position at which these teeth occluded with the dental pad. The modal position was 1 mm behind the anterior point of the dental pad of gum. About 1·5 % of the observations had bite positions deviating by 5 mm or more from the mode.Keeping the females during their first winter on low-ground pasture instead of the hill led to earlier eruption and slightly longer central incisors, but had little effect on bite position.The heritability of the number of incisors present at any one age was estimated to be 0·39 ± 0·11 by paternal half-sib correlation and 0·80 ± 0·27 by daughter-dam regression. Estimates of h2 for incisor length were less than half these values and those for the measure of bite position were very small and not significantly different from zero.For the ages up to 3½ years old, there were low but statistically significant correlations of number of incisors with ewe live weight (0·1–0·2) and fleece weight (around 0·1), incisor length with fleece weight (around 0·1) and at 1½ years old only between the bite measure and both weights (0·1). Weight of lamb weaned by the ewe was uncorrelated with these dental traits.It is concluded that in this flock, culling on the dental characters studied would not have improved performance, and selection would not change the position of the bite.

Sheep production on the north coast of New South Wales. 2. A feasibility study of prime lamb production

Lamb production was studied in an experiment that ran for four years, 1968 to 1972, at Grafton, New South Wales, in a region where no commercial sheep are grown. Merino and Dorset Horn x Merino ewes stocked at 15 ewes ha-1 were mated in spring to Border Leicester rams and the lambs sold for slaughter in October. The mean number of lambs born per 100 ewes mated was 81.7 for crossbred ewes and 48.4 for Merino ewes (P&lt; 0.05) and the mean carcase weights of the lambs were 14.8 kg and 12.7 kg, respectively (P&lt; 0.01). The mean weight of fleeces cut from Merino ewes (3.24 kg) was greater (P&lt; 0.01) than that from crossbred ewes (2.58 kg). The ewes were treated with anthelmintics either every four weeks or according to climatic conditions. There were no significant differences between the anthelmintic treatments for lamb liveweights at birth, weaning or slaughter; carcase weight; ewe fleece weight; or mortality rate. Treatment every four weeks increased ewe live weight during only one short period from August 1971 to February 1972 (P&lt; 0.05). Data from this experiment compared favourably with survey data for the high rainfall zone in Australia and it was concluded that prime lamb production on the north coast of New South Wales is biologically feasible.