Survival Rate Of Lambs Research Articles

Effect of controlled breeding on the fertility of Awassi and Red Karaman ewes and the performance of the offspring

This study was aimed at determining the effects of progestagen and ovarian stimulation agents (eCG) treatment, together with nutritional flushing, on the lambing rate of Awassi (A) and Red Karaman (RK) ewes and the performance of their offspring. In the trial, 60 Awassi and 40 Red Karaman ewes and their lambs were used. Each breed was randomly allocated to two groups per breed; one being the treatment group and the other the control. Estrus was synchronized by means of fluorogestone acetate (FGA) (40 mg) intravaginal sponges (14 days) and eCG (500 IU) injected i.m. at sponge withdrawal in all treatment groups. The interval from introduction of the ram to the onset of estrus was significantly earlier ( P < 0.01) in the control, compared to the treatment group. Lambing rate was recorded as 83.3 and 93.3% in the Awassi ewes and 90.0 and 85.0% in the Red Karaman ewes for the treatment and control groups following mating, respectively. An overall higher ( P < 0.05) percentage multiple birth rate was recorded in the ewes synchronized with FGA + eCG (34.9%), compared to ewes in the control groups (13.3%). Prolificacy significantly increased following treatment with eCG from 114 to 152% in the Awassi and from 111 to 133% in the Red Karaman ewes. Most of the lambing (75%) took place over a short period of time (5 days) in the treated groups. Progestagen sponge and eCG treatment resulted in an extra 6 kg meat being produced per ewe, compared to the control groups. Birth and weaning weights of the Awassi and Red Karaman lambs were found to be similar for the treatment and control groups. The highest lamb survival rates (lowest mortalities) at weaning in both breeds (81% versus 78% and 89% versus 74% in the Awassi and Redkaraman control and treated ewes, respectively) were obtained for ewes in the control groups. It is concluded that intravaginal sponges (FGA) can be used for estrus synchronization and mating in Awassi and Red Karaman ewes during the breeding season and that treatment with eCG following progestagen treatment has the potential of increasing the twinning rate. Nutritional flushing also resulted in a higher number of lambs born in the control ewes.

The effect of progesterone supplementation post mating and shearing of ewes in early pregnancy on the reproductive performance of ewes and birthweight of lambs

AIM: To determine whether short-term progesterone supplementation post mating or shearing of ewes in early pregnancy affected either the proportion of ewes that lambed or that had multiple lambs, or the birthweight of lambs. METHODS: Romney ewes (n=457) were synchronised in oestrus using controlled internal drug-releasing (CIDR) devices containing progesterone, and mated to Romney rams over a 5-day period. The mid-point of mating (Day 0) occurred 2 days after the withdrawal of CIDR devices. Ewes mated (n=397) were randomly allocated to one of four treatment groups: shearing at Day 5, shearing at Day 30, no shearing, and no shearing plus progesterone supplementation using a CIDR device inserted on Day 3 for 6 days. During the period from Day 5 to Day 27, six harnessed Suffolk rams were placed with the ewes and matings recorded. At Day 48, all ewes that did not return to the Suffolk rams were scanned for pregnancy using ultrasound. At Day 140, single- and multiple-bearing ewes were set-stocked at 15.1 and 12.2 ewes/ha, respectively, and equivalent numbers of ewes from each treatment group were placed in each paddock. Blood samples from 10 unshorn and 10 progesterone-supplemented ewes were collected on Days 3, 6 and 9, and analysed for plasma progesterone concentrations. Lambs were identified to their dam and weighed within 12 h of birth, and again at 27 and 93 days after the mid-point of lambing. The ewes were weighed at regular intervals throughout the trial. RESULTS: Plasma progesterone concentrations of supplemented ewes were higher than those of unsupplemented ewes (3.28 vs 1.75 ng/ml) on Day 6 (p=0.02) but not on Day 9 (4.58 vs 4.63 ng/ml). Treatment of ewes had no effect on either the proportion of ewes which lambed to the synchronised mating period or that had multiple lambs. Lambs born to ewes shorn at Day 30 tended (p=0.09) to be heavier at birth (by 0.28 kg) than those born to unshorn ewes but this effect was not evident when data were corrected for length of gestation. Neither shearing at Day 5 nor progesterone supplementation had any effect on the birthweight of lambs, and the treatment of ewes had no effect on the survival rate of lambs to weaning. CONCLUSIONS: Progesterone supplementation for 6 days beginning 3 days post mating did not increase either the proportion of ewes that lambed or that had multiple lambs, or the birthweight of lambs. Shearing 5 days after mating had no significant effect on the reproductive performance of ewes and need not be avoided, but is unlikely to result in an increase in lamb birthweight. Shearing ewes at Day 30 may result in an increase in the birthweight of lambs but, ideally, ewes should be further advanced in pregnancy before shearing is undertaken.

Does sward height grazed by ewes in mid- to late-pregnancy affect indices of colostrum intake by twin and triplet lambs?

AIMS: To determine if sward height grazed by ewes in mid- to late-pregnancy affects subsequent indices of colostrum intake by twin and triplet lambs, and the extent of the variation in colostrum intake between twin and triplet litter-mates. METHODS: Blood samples were collected from 75 twin and 46 triplet litters, respectively, 24–36 h after birth. Samples were not collected from lambs that died before this age. Lambs were born to ewes which had grazed one of four sward heights (2, 4, 6 and 8 cm) during mid- to late-pregnancy. Serum samples were analysed for gamma-glutamyl transferase (GGT) activities and glucose concentrations. The number of lambs present at weaning was used to determine lamb survival rate. RESULTS: GGT activities of lambs born to ewes that grazed swards 2 cm high were lower than those born to ewes that grazed swards 4 and 6 cm high (p=0.053 and p=0.037, respectively). Glucose concentrations were higher in twin than triplet lambs (p=0.003) and in lambs born to ewes grazed on swards 6 cm high than those born to ewes grazed on swards 2 cm high (p=0.033). These differences were not evident after correction for differences in birthweight. There was significant (p<0.001) variation within litter-mates for GGT activities and glucose concentrations in both twins and triplets. The blood constituent status of lambs that died before the 24–36 h collection period is not known. However, lambs which died after this period had significantly lower GGT activities (p=0.009) and glucose (p=0.010) concentrations at the time of sampling than those which survived. CONCLUSIONS: Farmers should ensure twin- and tripletbearing ewes in mid- to late-pregnancy are grazing at least 4 cm of herbage to ensure colostrum intake of lambs in the postpartum period is not adversely affected.

Effect of hogget nutrition in pregnancy on lamb birthweight and survival to weaning

The effect of hogget nutrition during pregnancy on birthweight and survival of lambs has not been thoroughly examined under pastoral conditions in New Zealand. The aims of the present study were to examine the effect of three hogget nutrition levels during pregnancy on both lamb birthweight and lamb survival, and hogget performance. Hoggets were offered either a “low”, “medium” or “high” level of nutrition of herbage during pregnancy, which resulted in total liveweight increases of 12, 21, and 30 kg, respectively over the period from 13 days after the average day of mating to average day 130 of pregnancy. Hogget nutritional treatment failed to affect either lamb birthweight or lamb survival. Nutritional treatment also failed to consistently affect ewe metabolic status. However, “low” group hoggets weaned significantly (P < 0.05) lighter lambs and were themselves significantly (P < 0.05) lighter at weaning and produced significantly (P < 0.05) less wool. The results of this study indicate that offering pregnant hoggets a level of nutrition that increases their liveweight gain above that of the expected conceptus growth will not benefit lamb birthweight or survival rate to weaning, but will increase hogget fleece weight and lamb weight at weaning. On the other hand, and in contrast to some earlier research, an even higher level of nutrition in pregnancy did not reduce birthweight or survival rate to weaning. This suggests that when farmers are aiming to achieve heavy lamb weaning weights and two‐tooth mating weights, they need not avoid offering hoggets a high level of nutrition in pregnancy.

Productivité des brebis Timahdite et croisées D’man x Timahdite en station et chez les éleveurs au Maroc

L’étude a porté sur la comparaison des productivités des brebis Timahdite et croisées D’man x Timahdite (DxT) en station et chez quatre éleveurs privés pratiquant le croisement industriel. Ainsi, une dizaine de brebis gravides DxT nées à la station ont été cédées à chaque éleveur. Au total, 131 performances de reproduction des brebis Timahdite et croisées DxT, et 188 performances de croissance et de viabilité des agneaux issus du croisement entre ces brebis et des béliers de race Ile-de-France ont été analysées. Les performances de reproduction des brebis DxT ont été supérieures à celles des brebis Timahdite, sauf pour le poids de portée à 70 jours. La taille de portée à la naissance, à 70 jours et le poids de portée à la naissance des brebis DxT ont été respectivement de 0,49 agneau, 0,32 agneau et 0,29 kg plus élevés que ceux des brebis Timahdite. Cependant, ces écarts ont été plus importants dans les élevages privés qu’en station. Les poids de portée à 70 jours des deux types génétiques n’ont pas été statistiquement différents. Pour les performances de croissance des agneaux, la race de la mère n’a eu d’effet significatif que sur le poids à 70 jours. Les agneaux issus de mères Timahdite ont pesé en moyenne 2,60 kg de plus que les agneaux nés de mères DxT. La différence entre ces deux catégories d’agneaux a été plus élevée en station (3,30 kg) que chez les éleveurs privés (1,6 kg). En conclusion, les brebis DxT ont réalisé chez les éleveurs des performances généralement plus élevées que les brebis Timahdite qui sont souvent utilisées comme support de croisement.

The effect of ewe maternal behaviour score on lamb and litter survival

The study was carried out on a commercial New Zealand sheep farm with high ewe reproductive rates and lamb survival produced through intensive selection in its Coopworth flock for maternal ability. Heritability and repeatability estimates were derived for ewe maternal behaviour score (MBS) and litter survival (LIS). Heritability estimates were derived for lamb survival as a trait of the lamb (LAS) for all lambs, for twin (LAS2) and for triplet (LAS3) lambs. MBS and LIS were measured on 1954 dams, for a maximum of four parities: 1997, 1998, 1999 and 2000. MBS was measured at tagging on a 5-point scale (1=poor, 5=excellent) when the dam's lambs were between 12 and 36 h old. The mean MBS in this study was 3.3 and increased with litter size. LIS was measured from birth to weaning. Mean litter survival was 83%. LIS increased significantly as MBS increased ( P<0.01). LIS decreased as the size of the litter increased ( P<0.01). Age of dam was a nonsignificant effect on LIS ( P>0.05). LAS was measured from birth to weaning on 4171 Coopworth lambs. Mean LAS was higher for lambs born as twins compared to lambs born as singles and lowest for lambs born as triplets ( P<0.01). LAS was lower for lambs born to dams aged 2 years. This effect was significant for all lambs, regardless of litter size at birth and for the triplet lamb data set ( P<0.01). The effects of age of dam and sex of lamb on twin lamb survival were not significant ( P>0.05). Ewe lamb survival rate was higher when compared to ram lambs in the full data set, however the relationship was reversed for the triplet lamb data set where ram lamb survival was greatest ( P<0.01). LAS decreased as the MBS of its dam increased ( P<0.01). The relationship was significant for lambs in the full data set and the twin data set ( P<0.05). MBS and LIS were under minimal genetic control. The heritability and repeatability for MBS were both 0.09. The heritability and repeatability for dam LIS were 0.0 and 0.11. Heritability for LAS over all lambs attributed to direct effects was 0.14, while the heritability attributed to maternal effects was 0.11. The heritability for twin (LAS2) and triplet (LAS3) lamb survival differed. Heritability attributed to direct and maternal effects were 0.0 and 0.21, respectively, for twin lambs and 0.08 and 0.16, respectively, for triplets. The genetic correlation between maternal and direct effect for LAS was −0.74. It is possible that the genes that regulate physiological and biochemical processes for survival are incompatible with the genes that enhance ewe–lamb bonding. For example, the genes that regulate the physiological factors to reduce gregariousness at parturition may in fact be the same genes that encourage isolation in the neonate from its littermates and dam. There is minimal genetic variation in this flock for lamb survival and maternal traits. Low genetic variation suggests that selection will be ineffective, and that farmers must consider environment and management techniques for improving lamb survival.

The effect of litter size and sward height on ewe and lamb performance

This study compared ewe and lamb performance in twin‐ and triplet‐bearing/rearing ewes offered varying sward heights from day 64 (P64) of pregnancy until weaning at day 87 (L87) of lactation. Ninety‐six twin‐ and 90 triplet‐bearing Romney ewes were randomly assigned on P64 to four replicated sward height treatments (2, 4, 6, and 8 cm sward height). Within 24–36 h of parturition (L1) the ewes were reassigned to two (4 and 8 cm) replicated sward heights until weaning at L87. Ewes grazing the 2 cm sward height during pregnancy were significantly (P < 0.01) lighter at P99 and P132 and at L1 than ewes grazing 4, 6 or 8 cm swards. These ewes also had significantly (P < 0.01) lower dry matter intakes, condition scores, and ultrasonic backfat depths. Litter size had no effect on ewe intake, ewe liveweight or condition score throughout pregnancy and lactation. Ewes grazing the 2 cm sward height had significantly (P < 0.05) lower dry matter intakes during pregnancy than ewes on the 4, 6, and 8 cm treatments. Estimated herbage dry matter intakes measured using n‐alkanes were similar to calculated energy requirements. Lambs born to ewes grazing the 2 cm swards during pregnancy were lightest at birth (P < 0.01), but sward height during pregnancy or lactation had no effect on lamb weaning weight or lamb survival rate to weaning. Triplet‐born lambs were 0.9 kg lighter (P < 0.05) than twins at birth, with the difference increasing in those lambs reared as a full triplet set to 4.7 kg at L87. Lamb losses were 14% in twin‐born lambs and 32% in triplet‐born lambs. There was no sward height by litter size interaction for ewe liveweight, intake or lamb birth and weaning weight or survival, therefore the results suggest ewes rearing either twins or triplets should be fed sward height allowances of 4 cm or better during pregnancy. However, there is no need to feed above 4 cm in pregnancy or lactation to optimise lamb weaning weight, lamb survival or ewe liveweight and condition score gain.

The effect of high dietary protein levels during late gestation on colostrum yield and lamb survival rate in singleton-bearing ewes

The study was carried out to determine the effect of crude protein (CP) levels in late pregnancy on the subsequent colostrum production and lamb survival rate. A total of 40 singleton-bearing Hampshire Down X Karayaka (F 1) crossbred ewes were allocated to two treatment groups ( n=20 for each group), namely a control (P) and high CP (1.4P) group. The ewes in the P group were fed a protein maintenance level for pregnant ewes (117 g CP and 10.5 MJ metabolizable energy (ME)/kg dry matter (DM)), while ewes in the 1.4P group were fed 1.4 times the protein requirement level for pregnant ewes (165 g CP and 10.5 MJ ME/kg DM). The high crude protein level (1.4P) offered to the ewes did not affect lamb body weight from birth to weaning, however, it increased the live weight changes of ewes (2.5±1.3 kg for P versus 6.4±1.5 kg for 1.4P; P<0.05), lambing difficulty (5% versus 30%; χ 2=4.33; P<0.05) and lamb birth weight (4.3±0.1 kg versus 4.9±0.1 kg; P<0.05). It also decreased the total colostrum yield (1700±165 g versus 1200±147 g; P<0.01) and lamb survival from birth to weaning (100% versus 80%; χ 2=4.44; P<0.05). These results indicate a high level of CP (1.4P) supplementation to singleton-bearing ewes during late gestation to increase lamb birth weight decrease colostrum yield, increase lambing difficulty and reduce lamb survival rate prior to weaning. In conclusion, because of the adverse effect of high dietary protein nutrition during late gestation on colostrum yield and lamb survival rate in singleton-bearing ewes, feeding of protein to pregnant ewes with a view to increase postnatal lamb growth performance and lamb survival rate, should be treated with caution.

Effect of herbage allowance and concentrate feed level offered to ewes in late pregnancy on ewe and lamb performance

Lower cost systems of sheep production, with reduced labour inputs, require examination for the future viability of the sheep industry. Carson and Dawson (2002) demonstrated that ewes lambing under grass-based systems had similar lamb outputs and survival rates to ewes lambing under labour intensive, indoor lambing systems. Although there is a significant amount of information is available on the effect of conserved forage on ewe performance in late pregnancy, there is a scarcity of information on the effect of grazed grass and concentrate supplementation at grass in late pregnancy on subsequent ewe performance. The aims of this study were to investigate the effects of herbage allowance and concentrate feed level during late pregnancy on ewe live weight and body condition change and lamb growth and development.

Genetic parameter estimates in Sabi sheep

Genetic parameters for growth traits in Sabi sheep were estimated using asreml from data records of 4123 lambs from 130 sires and 1131 dams collected between 1984 and 1994. Reproduction traits and lamb survival to weaning were analysed fitting a sire threshold model. The direct additive contribution to birth weight, 30-day weight, 60-day weight, weaning weight (WW), preweaning average daily gain (ADG), 12-months weight, 18-months weight and Kleiber ratio (KL=ADG to weaning/WW 0.75) was 0.25, 0.11, 0.13, 0.13, 0.17, 0.26, 0.37 and 0.08, respectively. The direct heritability for slaughter, hot and cold carcass weight, total litter weight weaned, mating and postpartum weight and ewe weight at weaning of lamb was 0.27, 0.18, 0.18, 0.12, 0.58, 0.53 and 0.67, respectively. Maternal heritabilty declined from 0.12 at birth to 0.06 at 60 days of age and was negligible thereafter. The maternal permanent environmental component due to the dam contributed 3–15% of the total phenotypic variances for all the traits under consideration. Genetic progress is possible for all the growth, carcass and ewe traits considered in this study. The heritabilty estimates for reproduction traits were low, viz 0.02, 0.06, 0.04, 0.02 and 0.04 for fertility (whether a ewe lamb or not; 0 or 1); reproductive rate (number of lambs born to a ewe mated; 0, 1 or 2); number of lambs weaned to a ewe lambing (0, 1 or 2); number of lambs weaned to a ewe exposed (0, 1 or 2), and lamb survival rate (whether a lamb born alive, was dead or alive at weaning). Though slow genetic progress is possible with all reproduction and survival traits, it would be more efficient to select for prolificacy (number of lambs born to a ewe that lambed; 1 or 2) ( h 2=0.26) but guarding against a higher lamb mortality.

Productive performance of hair and wool type Dorper sheep under extensive conditions

The reproductive performance, growth, slaughter traits, and several conformation characteristics in Dorper sheep (hair and wool types) were evaluated under extensive conditions in the north-western Karoo region of South Africa. From 1993 to 2000, lambs of hair ( n=1070) and wool ( n=1044) type Dorper sheep, and corresponding reproductive records from 872 and 874, respectively, were analysed. There was no significant differences between hair and wool type lambs for body weight from 42 days till 12 months of age, and for pre- or post-weaning growth rate. The analysis of conformation tend to suggest that the hair type lambs were blockier with shorter legs, compared to the leggier appearance of the wool type lambs. This is also evident from the longer carcass length (108.5 vs. 107.2 cm) and hind leg length of wool type lambs compared to hair type lambs. With regard to other carcass traits, wool type lambs had heavier carcasses (19.6 vs. 19.2 kg) and higher dressing percentage (49.9 vs. 49.0%), though, fat measurements and carcass grades were similar. The ewes of the hair type were heavier at mating than wool type (57.4 vs. 56.4 kg). No differences were, however, observed for percentage of ewes lambed, lambs born, lambs weaned, survival rate of lambs or kg lamb produced per ewe per year. It was concluded that the economically important reproduction and growth traits were similar between the hair and wool types of Dorper sheep. Differences that do occur in some conformation and carcass traits will not effect the economic realisation from the different types.

Characteristics of the American Polypay: A review

SummaryThe Polypay sheep breed was developed at the U.S. Sheep Experiment Station with a reproductive capacity markedly superior to that of domestic US western range breeds. The Polypay is a four breed composite of Targhee, Rambouillet, Dorset and Finnish Landrace breeds. It is a medium-sized wool sheep (average mature ewe weight of 72 kg) with a smooth body free of excessive skin wrinkles on the neck and body and a poll head. Comparative studies with other US domestic breeds have shown the Polypay to have earlier sexual maturity higher fertility and prolificacy rates. Mature ewes give birth to an average of 2.4 lambs and wean an average total litter weight of 63.8 kg per ewe at 120 days post partum. Lamb survival rates to 21 and 120 days are greater than those of other breeds compared. Average individual lamb weaning weight at 120 days (36.1 kg) exceeded that for Rambouillet and Targhee lambs (34.5 and 33.8 kg, respectively). Polypay carcasses are similar to those of Rambouillet and Targhee for dressing percentage, body wall thickness, kidney and pelvic fat, and ribeye area. Measures of carcass fat are less in the Polypay when compared to the Rambouillet and Targhee while qualitative leg scores for the Polypay were more favorable. Productive longevity under western range herded conditions does not differ among Polypay, Rambouillet, Targhee and Columbia sheep. In a farm flock production system, the average number of productive years for Polypay ewes exceeded that of most crossbred types. Wool characteristics are defined as a coarse to medium grade wool with a fiber diameter ranging from 24 to 33 μm. Fiber staple length ranges from 7.6 to 12.7 cm with a common mean of approximately 10 cm. Raw fleece weights are considered light and range from 2.7 to 4.5 kg. Yield of clean wool is approximately 57 percent. Economic evaluations favored the Polypay in all production systems considered with 15 to 36 percent increase in sales or profits compared to other US domestic breeds. When considering the Polypay breed for importation, some prudence should be exercised because it may not be suitable to all environments and production systems in the world, especially where nutritional and management resources are not sufficient to support lactating ewes rearing twins.

Comparison of five crossbreeding types involving Timahdit, D’man and improved terminal sire breeds of sheep: ewe reproduction, lamb survival and growth performance

AbstractA crossbreeding experiment involving Timahdit (T), D'man (D) and improved sire breeds (M) was conducted to compare lamb production in five crossbreeding types: D ✕ D, T ✕ T, D ✕ T (DT), M ✕ T, and M ✕ DT lambs. Reproductive and production traits were analysed in 1187 litters, 1586 lambs born and 1346 lambs weaned, progeny of 605 ewes. Effects of crossbreeding type, year of birth, sex of lamb, age of dam, and type of birth were significant on the majority of traits studied. The D ✕ D and M ✕ DT crossbreeding system showed the highest litter sizes at lambing and at weaning with respective values in D ✕ D (2·17, 1·34) and M ✕ DT (1·72, 1·39). Ewes bearing the M ✕ DT cross lambs showed the highest (P &lt; 0·05) litter weight at weaning (28·28 kg) followed by those with M ✕ T (23·14 kg), and D ✕ D (22·53 kg) lambs. M ✕ DT and M ✕ T lambs were heavier and grew faster than the other lambs. On the other hand, lamb survival rates and growth traits were the lowest in D ✕ D but those in T ✕ T and D ✕ T genetic types of lamb were intermediate. Results showed that D as a dam breed had a favourable effect on litter size (P &lt; 0·01) but unfavourable effect on lamb survival and birth weight. The reproductive performance of DT crossbred ewes, due to their high prolificacy and lamb survival, associated with the favourable effect of an improved terminal sire (M) for growth traits, indicated that the three breed cross (M ✕ DT) could enhance lamb production in Morocco.

Drug Treatment for Lungworm in Bighorn Sheep: Reevaluation of a 20-Year-Old Management Prescription

We conducted a 4-year management experiment to examine the annual effects of alternative management treatments, including anthelmintic administration, on lamb survival in Rocky Mountain bighorn sheep (Ovis canadensis canadensis) herds in southcentral Colorado. Beginning in December 1991, 4 bighorn herds were managed under alternative treatment regimes: baiting with alfalfa hay and apple pulp treated with fenbendazole (BT), baiting with alfalfa hay and apple pulp without fenbendazole (B), placing fenbendazole-treated salt blocks on winter ranges (T), and both withholding bait and fenbendazole (control; C). Treatments were rotated annually under a predetermined, randomly-selected schedule. Mean lamb production, survival, and recruitment rates did not differ among herds or years. None of the management treatments produced demonstrable improvements in lamb production, survival, or recruitment. Estimated effects (±SE) of treatments on lamb production and survival were small (≤0.09 ± 0.18). Annual recruitment rates (lambs/marked ewe) through October ranged from 0.13 to 0.88, but overall recruitment rates (mean; 95% CI) for B (0.72; 0.55-0.90), T (0.71; 0.47-0.95), and BT (0.52; 0.08-0.97) were indistinguishable from C (0.62; 0.19-1.0). Sick and coughing lambs were observed every summer in 1 herd and 1 summer in a second. Our results demonstrate that annual parasite treatment is not prerequisite for acceptable lamb survival among southcentral Colorado's wild bighorn populations, and that annual parasite treatment may not prevent catastrophic losses of lamb cohorts. Based on these data, we question the need for annual baiting and parasite treatment in the herds studied here and recommend such practices be reevaluated elsewhere.

Environmental impacts on offspring survival during the lambing period in central Patagonia.

Weather conditions are the main factors affecting the survival rate of newborn lambs. In the windy climate of Patagonia, the influence of weather conditions is exacerbated as the wind speed increases noticeably in spring. If the wind increases faster than the temperature rises, wind chill conditions worsen temporarily. This departure from the predictable improvement in bioclimatic conditions as the season moves towards summer may coincide with lambing, if this is not adequately regulated. This paper explores bioclimatic conditions during the 2-month period in which lambing may take place (i.e. mid-September to mid-November), and identifies the unfavourable period that occurs in the second fortnight of October. Starting from the Mount and Brown (Agric Meteorol 27:241-255, 1982) model to assess thermal stress in sheep by means of common meteorological records, a simpler model was developed employing in long-term records. For 2-week averages of temperature (Tf), wind speed (Vf) and total precipitation (Pf), the average heat loss in sheep (HLf) was 40.40 - 2.07Tf + 5.64Vf + 0.04Pf. (r2 = 0.95). A 24-year series of Tf, Vf and Pf data was employed in the calculation of HLf, and results showed this parameter was significantly higher in the second fortnight in October. HLf values were classified into four groups (from "very good" to "very bad" conditions); once again, significant differences appeared in the second fortnight in October. Finally, HLf during the lambing period was correlated to the percentage of lambs surviving 2 months later. Significant differences between the survival of lambs born under "very bad" and "very good" conditions were found, but intermediate HLf conditions did not show a clear pattern. The survival rate was best correlated to HLf in the fortnight preceding lambing (P < 0.05). This suggests that bioclimatic conditions during late pregnancy are at least as important as conditions during lambing in determining the survival lambs.

In vitro and in vivo activities of NS-718, a new lipid nanosphere incorporating amphotericin B, against Aspergillus fumigatus.

We evaluated the in vitro and in vivo potencies of a new lipid nanosphere that incorporates amphotericin B (AmB), NS-718, against Aspergillus fumigatus. The in vitro activity of NS-718 (the MIC at which 90% of strains are inhibited [MIC90], 0.25 microgram/ml) against 18 isolates of A. fumigatus was similar to that of deoxycholate AmB (D-AmB; Fungizone; MIC90, 0.25 microgram/ml), but NS-718 was more potent than liposomal AmB (L-AmB; AmBi-some; MIC90, 1.0 microgram/ml). The in vivo efficacy of NS-718 in a rat model of invasive pulmonary aspergillosis was compared with those of D-AmB and L-AmB. A low dose (1 mg/kg of body weight) of L-AmB was ineffective (survival rate, 0%), although equivalent doses of D-AmB and NS-718 were more effective (survival rate, 17%). However, a higher dose of NS-718 (3 mg/kg) was more effective (survival rate, 100%) than equivalent doses of D-AmB and L-AmB (survival rate, 0%). To explain these differences, pharmacokinetic studies showed higher concentrations of AmB in the plasma of rats treated with NS-718 than in the plasma of those treated with D-AmB. Our results suggest that NS-718, a new preparation of AmB, is a promising antifungal agent with activity against pulmonary aspergillosis.

Economic values for ewe prolificacy and lamb survival in New Zealand sheep

Economic values of changes in ewe prolificacy (EP) and two lamb survival traits were quantified for situations where each trait is changed by either quantitative genetic selection or the introduction of major genes for prolificacy. The economic value of EP was shown to be highly variable ($11.55 to $24.26 for lambs born per ewe lambing) across farm types. The economic values of the Booroola and Inverdale genes which affect EP also varied substantially from farm to farm. Values ranged from $5.24 to $16.23 per ewe lambing for a single allele of the Booroola gene and from $4.69 to $12.53 for a single allele of the Inverdale gene. The additional value of a second allele of the Booroola gene was relatively small or negative (−$0.76 to $2.29). The key factors influencing variability in economic values for EP were shown to be: 1, the current average level of flock prolificacy; 2, the relative survival rates of lambs born in alternative litter sizes and 3; slaughter of lambs at fixed age versus fixed weight. The economic values for survival until 24 hours post-partum per lamb born and for survival from 24 hours post-partum until weaning per lamb alive at 24 hours were moderately variable across farm types ($0.22 to $0.28 and $0.31 to $0.36 respectively for an improvement of 1%).

Breed Genetic Components of Ewe Reproductive Performance and Lamb Survival Rates for Egyptian Rahmani and Ossimi Breeds and Their Crosses With Finnsheep

Breed Genetic Components of Ewe Reproductive Performance and Lamb Survival Rates for Egyptian Rahmani and Ossimi Breeds and Their Crosses With Finnsheep

Factors affecting preweaning lamb survival in continuously housed sheep

Summary. Preweaning lamb survival for intervals of up to 8 weeks was studied in the progeny of the local fat-tailed Naeemi and imported Border Leicester × Merino ewes mated to Naeemi rams. An intensive system of management with zero grazing was used to conform to the most probable type of production system to be used in Kuwait. The effects of year and season of lambing, litter size, sex, genetic group and birth weight were determined. Lamb survival rates from birth to 1 week, from 1 to 4 weeks and from 4 to 8 weeks were 96, 99 and 97% respectively. Overall survival from birth to weaning at 8 weeks was 91%. Genetic group, litter size, sex of lamb and year of lambing had no significant effects on survival. Season was significant from birth to 1 week, from 4 to 8 weeks and from birth to 8 weeks. Lamb birth weight was the most important factor affecting lamb survival, through a quadratic relationship between weight and survival.

Induction of Twinning in Merino and Akkaraman Ewes

The present study was carried out on a total of 80 ewes, 40 Merino, 40 Akkaraman and 12 intact rams. Both group of ewes belong to Merino and Akkaraman breeds were divided in to two groups as treatment and control. In the breeding season, 500 IU PMSG (Choronogest PMSG - intervet) were injected to the treatment groups on the day 13 of their sexual cycle. All ewes detected into oestrus in treatment and the control groups were allowed for mating. Treatment and control groups of the two breeds of ewes were compaired for their pregnancy rates in first service, pregnancy periods, pregnancy problems, lambing types, incidence of retained placenta, birth weights and survival rates of lambs in end of the first month. Pregnancy rates in the treatment groups after first service increased at a rate of 20 and 25 percent for the Akkaraman and Merino ewes, respectively. Lambing rates (lambs/100 lambing ewes) also increase at a rate of 50 and 52.7 percent for the same groups. Although toxemia and abortion rate were in the acceptable limits, retained placenta cases were 15 percent higher than controls. The ewes suffering from retained placenta were observed during the next season and all of them concevied after first service. Average duration pregnancy was noted approximately a week shorter than controls in Merino treatment group. Some of the lambs which are twin or triplets needed to additional feed. As as results; pregnancy rates after first service and lambing percentages can be increased by PMSG injection on the day 13 of the sexual cycle without pregnancy problems and postpartum disorders expect from retained placenta.