Lamb Birth Research Articles

Comparative Phenotypic Traits and Performances of Native Sheep in Naikhongchhari Hilly Area of Bangladesh

Background: Many studies have been conducted to investigate the performance of native sheep in plains and coastal regions, but no studies have been conducted in hilly regions of Bangladesh. Considering this fact, Coastal, Barind and Jamuna River Basin sheep were evaluated for their phenotypic traits, productive and reproductive abilities to gain insights into their performance in the hilly region. Methods: The Coastal, Barind and Jamuna River Basin sheep were collected from Bangladesh Livestock Research Institute (BLRI), Savar, Dhaka for the first time to Regional Station, Naikhongchhari, BLRI and separated based on their phenotypic characteristics. A breeding program was established to ensure purity, using independent culling levels and selection indexes. Ewes were allowed to lamb throughout the year, mated with rams in a 15-20 to 1 ratio. The sheep were kept in a semi-intensive system. Result: The highest lamb birth weight was observed in coastal Region sheep, both male (1.43 kg) and female (1.22 kg), followed by Barind males (1.36 kg) and females (1.15 kg), respectively. The highest average daily gain was found in coastal region sheep (41.87 g/d), which was significantly higher compared to others. The lowest age at first heat, gestation length, age at first lambing, post-partum heat period, days open, lambing interval was observed in Barind sheep. Finally, the study offers valuable insights into the potentialities of native sheep in hilly regions, guiding future research and extension efforts for sheep farming in these areas.

288 Maternal fatty acid supplementation and its impact on dam and offspring performance

Abstract Fatty acid supplementation has multiple benefits to the offspring when supplemented to the dam during pregnancy; limited to no benefits to the dam have been documented. We hypothesized that maternal fatty acid supplementation during pregnancy would result in improved body weight (BW) and body condition score (BCS) in the ewes and improve lamb growth until weaning and male offspring growth following weaning when ewes were supplemented fatty acids. On d -8 of the study (35 d of gestation), all ewes were weighed, BCS was collected, and pregnancy status determined. Pregnant Targhee ewes (n = 83) were assigned to a treatment group based on age, BW, and BCS, to one of four treatment gr: 1) 22 g/ewe daily of Ca salts of saturated and monosaturated fatty acids based on palmitic and oleic acids (CON; EnerGII, Virtus Nutrition, LLC, Corcoran, CA); 2) 22 g/ewe daily of Ca salts of PUFA based on eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids (ɷ-3, Strata; Virtus Nutrition LLC); 3) 22 g/ewe daily of Ca salts of PUFA based on linoleic acids (ɷ-6, Prequel; Virtus Nutrition LLC); or 4) 11 g/ewe of Ca-salts enriched with EPA+DHA (Strata) and 11 g/ewe of Ca-salts enriched with linoleic acid (Strata) daily (ɷ-3 + 6; Virtus Nutrition LLC). Fatty acid supplementation occurred from d 0 until d 88 of the study, and all ewes were fed grass hay. Ewe BW and BCS were recorded at d -8, 51, 93, and 240 of the study. Twenty-four hours after birth, lamb sex was identified and weighed (n = 136 lamb; CON = 33; ɷ-3 = 32; ɷ-6 = 36; ɷ-3 + 6 = 35). Lambs were weighed at d 175 and 240 (weaning) of the study (n = 86; CON = 22; ɷ-3 = 22; ɷ-6 = 21; ɷ-3 + 6 = 21). Body weight, BCS, and scrotal circumference (SC) were collected on all ram lambs at d 352, 380, and 408. No differences were observed in ewe BW or BCS at d -8, 51, or 93 of the study (P ≥ 0.26) between the treatment groups (Table 1). A treatment × day interaction was observed at d 240 of the study when ɷ-6 ewes had a greater (P = 0.03) BCS compared with group cohorts. No differences in lamb birth weight, lamb weight or average daily gain at d 175 or 240 of the study between treatment groups (P ≥ 0.25; Table 2). No differences were reported in ram lamb BW, BCS, or SC at d 352, 380, and 408 (P ≥ 0.31; Table 3). These results indicate that maternal fatty acid supplementation alters ewe BCS at the time of weaning; however, supplementation does not impact lamb growth from birth until weaning or ram lamb growth and scrotal circumference.

Influence of Exogenous Melatonin Treatment on the Ram Fertility of the North-east Bulgarian Fine-wool Sheep Breed

The potential of the epiphyseal hormone melatonin to effect on seasonally breeding species has been extensively studied, but the data remain inconclusive. Levels of reproductive parameters modulation are important to monitoring, given the breed affiliation, as example analyzed breed, which has a pronounced seasonal type of reproduction. The objective of this study was to determine whether application of exogenous melatonin has an effect on ram fertility of the North-east Bulgarian fine-wool sheep breed, as estimated by the reproductive performances of ewes, in the non-breeding season. In addition, the study quantified the effects of exogenous melatonin on ejaculate volume and concentration of sperm in rams with melatonin implants (n = 5) and per os treated rams (n = 5). The application of exogenous melatonin improves the fertility of rams of the studied breed. As a result of the current study, in the 2nd experimental group there was a positive trend on ejaculate volume and concentration of sperm throughout the experiment compared to control group. Although rams exhibited an improvement in sperm parameters, a significantly increased birth rate was found in sheep mating with male receiving melatonin both through implants (P < 0.05) and per os (P < 0.05). It was found to increase the total percentage of birth lambs in 1st (28%) and 2nd (29%) experimental groups compared to control. The results are guiding for North-east Bulgarian fine-wool sheep farmers and breeders, in terms of opportunities to improve the breeding process and obtain more lambs.

Least Squares, Simple Linear Regression, and Pearson Correlation Analysis between the Lactation Milk Yield of Norduz Ewes and Their Lambs’ Live Weight

This study aimed to determine the lactation milk yield of Norduz ewes and to determine the effects of milk yield on their lambs’ growth and development characteristics. Additionally, the correlations between the sheep’s milk yield, lambs’ live weight, and affecting factors were determined. The study was conducted at the Van University of Yüzüncü Yıl Agricultural Research Center. In the study, 61 Norduz ewes and 66 male and female lambs they bore were included. The sheep were milked at 30-day intervals until the 180th day. Similarly, the lambs were weighed at 30-day intervals from birth to 180th day. The means and standard errors of the milk yields were obtained on the 30, 60, 90, 120, 150th, and 180th days of milking. The live weight means and standard errors of the lambs on the 30th, 60th, 90th, 120th, 150th, and 180th days are given. According to the GLM analysis results, sex significantly influenced lactation length (p<0.05), and there was a difference in favor of female lambs. The impact of dam age was notably significant on live weight at days 60 and 90 (p<0.05). Additionally, birth type significantly affected live weight at day 30 and 60 (p<0.001), as well as at day 90 (p<0.01). Regarding the linear relationship between dam weight and live weight, a significant effect was observed at day 30 (p<0.001), day 60 (p<0.01), and day 90 (p<0.05). Notably, the linear effects of lamb birth weight on live weight remained significant across all control periods (p<0.001).

Influence of supplemental choline on milk yield, fatty acid profile, and weight changes in postpartum ewes and their offspring.

The most intensive nutritional requirements occur during milk production's peak. Ewe milk contains more protein and fat than cow milk. The nutritional factors significantly determine the composition. The liver undergoes high stress during lactation but is relieved by essential nutrients. Choline acts metabolically as a lipotrope. This compound functions in cell structure construction, maintenance, and acetylcholine synthesis. The animal nutrition industry provides choline from various sources, such as synthetic and natural kinds. This study evaluated the influence of two distinct choline sources on dairy ewes' peripartum and postpartum milk production, composition, and offspring growth. Twenty-four Rambouillet ewes, each weighing around 63.7 ± 1.7 kg, aged three with two previous births, spent 30-day pre-partum and post-partum in individual pens (2 × 2 m). They were given different experimental treatments 30 days before and after birth according to a randomized design; no choline (a), 4 g/day rumen-protected choline (RPC) (b), or 4 g/day thiocholine (c). Milk samples for milk composition and long-chain fatty acid (FA) analysis were taken every 30 days during milk collection. Significant differences (p < 0.05) in ewe body weight, lamb birth weight, and 30-day-old lamb body weight were observed at lambing and on day 30 of lactation due to choline treatment. Milk yield was significantly higher (1.57 kg/day) compared to the control (1.02 kg/day) and RPC (1.39 kg/day), due to the herbal choline source. There was no significant difference in the milk's protein, lactose, fat, non-fat solids, and total milk solids content between the treatments. Herbal choline lowers (p < 0.05) the concentrations of caproic, caprylic, capric, lauric, and myristic acids while boosting (p < 0.05) those of oleic and cis-11-eicosenoic acid, the changes influencing long-chain FA levels (p < 0.05). Providing choline from both sources to ewes enhanced milk production and body weight at lambing and on 30-day post-lambing. The herbal choline supplement altered short-chain milk FAs, while representative concentration pathways affected medium-chain ones.

Microelements Effect on the General Sheep Performance

Our research shows that the content of microelements (cobalt, copper, iodine) in local feed (alfalfa grass, corn silage, barley and wheat straw, etc.) is very low, and in some cases completely absent. This negatively affects animal productivity. Taking this into account, in 2022-2023 we studied the effect of microelements cobalt, iodine and copper on the overall productivity of sheep. During the experiments, each head of sheep was given daily 10 mg of cobalt chloride, 10 mg of potassium iodide and 10 mg of copper sulfate. The results of a 120-day experiment and our observations show that sheep receiving these microelements had 5,7% more wool and 10,3% greater lamb birth rate compared to sheep that did not receive microelements. Microelements had a positive effect on sheep wool yield, wool length, live weight of the animal, and the development of the lamb in the womb. In the sheep of the experimental group that received micronutrient nutrition, the wool yield was 78 g, and the length of the wool was 0,8 cm longer than in the control group. The live weight of sheep and lambs receiving micronutrients was 3,92 kg at birth and 26,55 kg at weaning, and the live weight of sheep lambs not receiving micronutrients was 3,70 kg and 24,65 kg. Thus, in the conditions of Nakhchivan AR, it is considered advisable to widely use microelements to increase the overall productivity of sheep.

Effects of prepartum shearing on metabolic and placental parameters of ewes: Impact on productive parameters of their lambs

Prepartum shearing has been associated with increased lamb survival under pastoral conditions. This research aimed to evaluate the effects of early and late prepartum shearing in gestating Corriedale ewes on the metabolic profile and placental parameters of the ewes and how these changes affect the productive parameters of their lambs. On day 70 of gestation, 37 ewes carrying a single foetus were randomly divided into three groups: ewes sheared at day 70 of gestation (early, PS70, n = 12), sheared at day 110 of gestation (late, PS110, n = 12), and ewes unsheared at prepartum (US, n = 13, control group). Energy metabolism (glycaemia, insulin, NEFA, and BHB) and placental parameters (placental weight, number, and characteristics of cotyledons, and placental efficiency) were evaluated in the ewes. Live weight, morphometric measurements, and body composition were determined in the lambs. Prepartum shearing performed on different days (early and late) caused changes in energy metabolism, leading to a decrease in serum insulin and an increase in NEFA and BHB blood values. Early prepartum shearing increased placental weight and the number and weight of the 2–3 cm-cotyledons, while late prepartum shearing increased placental weight and placental efficiency and only changed the weight of the 2–3 cm-cotyledons. Prepartum shearing on both days caused an increase in lamb birth weight. Therefore, prepartum shearing caused changes in the metabolic profile and placenta of the ewes, which resulted in increased weight and development of lambs at birth.

Effect of Maternal High Fat Diet on the Hypothalamus-Pituitary-Adrenal Gland (HPA) Axis of the Offspring in Sheep

Maternal consumption of a high fat diet (HFD) during pregnancy is associated with metabolic dysfunction and altered HPA axis function in the offspring. These effects are well established in species with short gestation length (e.g., rodents), but less established in species with longer gestation periods more comparable with humans. The objective of the study was to determine the effect of maternal HFD on basal and stimulated cortisol secretion in the offspring at 16 weeks of age in sheep. All experiments were approved by the Institutional Animal Care and Use Committee at Cal Poly Pomona. Pregnant ewes were assigned to control (n=3) and HFD (n=3) groups. The control group was fed farmers best complete ewe and ram pellets. The HFD group was fed the same diet with an additional 30% rumen protected fat (Megalac, Volac Wilmar Feed Ingredients Ltd). After birth lambs were weaned at 12 weeks of age and given free access to control pellet diet with grains. To assess adrenal cortisol secretion at 16 weeks, lambs were infused intravenously with adrenocorticotropic hormone (ACTH; 2 ug/kg cortrosyn in 1 mL saline). Blood samples (1 mL) were taken through the jugular catheter at −30, −15, and 0 min (immediately before) and 5, 15, 30, 60, 90, and 120 min after ACTH administration for measurement of plasma cortisol by ELISA. Data were analyzed by two-way repeated measures ANOVA with a Tukey posthoc test. Basal plasma cortisol tended to be higher in HFD (32±8 ng/mL) than control (13±3 ng/mL) lambs, but this did not reach statistical significance. Plasma cortisol was higher than baseline from 15 to 90 minutes after ACTH administration in all lambs (p&lt;0.05). The increment in plasma cortisol was higher in HFD than control lambs from 15-90 minutes (p&lt;0.05). Accordingly, the maximum increase in plasma cortisol at 60 minutes and was higher in HFD (245±8 ng/mL) than control lambs (121±50 ng/mL p&lt;0.05). These preliminary data suggest that maternal consumption of a high fat diet during pregnancy may increase basal and stimulated activity of the HPA axis in sheep. The study was funded by a Strategic Interdisciplinary Research Grant (SIRG) at California State Polytechnic University, Pomona. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Extended period of ventilation before delayed cord clamping augments left-to-right shunting and decreases systemic perfusion at birth in preterm lambs.

Previous studies have suggested that an extended period of ventilation before delayed cord clamping (DCC) augments birth-related rises in pulmonary arterial (PA) blood flow. However, it is unknown whether this greater rise in PA flow is accompanied by increases in left ventricular (LV) output and systemic arterial perfusion or whether it reflects enhanced left-to-right shunting across the ductus arteriosus and/or foramen ovale (FO), with decreased systemic arterial perfusion. Using an established preterm lamb birth transition model, this study compared the effect of a short (∼40s, n=11), moderate (∼2min, n=11) or extended (∼5min, n=12) period of initial mechanical lung ventilation before DCC on flow probe-derived perinatal changes in PA flow, LV output, total systemic arterial blood flow, ductal shunting and FO shunting. The LV output was relatively stable during initial ventilation but increased after DCC, with similar responses in all groups. Systemic arterial flow patterns displayed only minor differences during brief and moderate periods of initial ventilation and were similar after DCC. However, an increase in PA flow was augmented with an extended initial ventilation (P < 0.001), owing to an earlier onset of left-to-right ductal and FO shunting (P < 0.001), and was accompanied by a pronounced reduction in total systemic arterial flow (P=0.005) that persisted for 4min after DCC (P ≤ 0.039). These findings suggest that, owing to increased left-to-right shunting and a greater reduction in systemic arterial perfusion, an extended period of ventilation before DCC does not result in greater perinatal circulatory benefits than shorter periods of initial ventilation in the birth transition. KEY POINTS: Previous studies suggest that an extended period of initial ventilation before delayed cord clamping (DCC) augments birth-related rises in pulmonary arterial (PA) blood flow. It is unknown whether this greater rise in PA flow is accompanied by an increased left ventricular output and systemic arterial perfusion or whether it reflects enhanced left-to-right shunting across the ductus arteriosus and/or foramen ovale, with decreased systemic arterial perfusion. Anaesthetized preterm fetal lambs instrumented with central arterial flow probes underwent a brief (∼40s), moderate (∼2min) or extended (∼5min) period of ventilation before DCC. Perinatal changes in left ventricular output were similar in all groups, but extended initial ventilation augmented both perinatal increases in PA flow, owing to earlier onset and greater left-to-right ductal and foramen ovale shunting, and perinatal reductions in total systemic arterial perfusion. Extended ventilation before DCC does not confer a greater perinatal circulatory benefit than shorter periods of initial ventilation.

Inactivated Flagellin-Containing Vaccine Efficacy against Ovine Enzootic Abortion.

Chlamydia abortus is the etiological agent of abortion and fetal loss in sheep, goats and bovine cattle in many countries. Even though commercially available vaccines can reduce the incidence in sheep, the development of new, safe, and effective vaccines remains high on the agenda. In this study, an evaluation was made of the efficacy of a vaccine candidate, an inactivated antigen based on the extract of outer membrane proteins of a C. abortus strain known as Chlamydia VNITIBP-21, in combination with recombinant flagellin as an adjuvant. Pregnant sheep (n = 43) were divided into three groups: an experimental vaccinated group, a control infected group and a control non-infected group. The sheep were vaccinated twice, with an interval of 3 weeks, then infected with the homologous virulent strain of Chlamydia abortus on pregnancy day 75. The vaccine candidate reduced C. abortus shedding in vaginal swabs considerably, in comparison with the control group. In addition, ewes in the experimental group experienced no abortions, while those in the control group experienced instances of abortion, as well as births of weak and nonviable lambs. The findings show that the vaccine candidate proved itself to be promising in combatting the agent of ovine abortion and fetal loss.

Effects of Elective Caesarean Sections in Healthy Near-Term Ewes on Subsequent Reproductive Performance.

Post-surgical reproductive performance following ovine caesarean section has not been well studied. To assess any direct effects of surgical delivery in the absence of confounders such as dystocia or underlying diseases, we studied elective surgery performed in healthy animals for teaching purposes. Four hundred and eleven paired breeding records following vaginal delivery (n = 233), elective caesarean section (n = 122), and subsequent further vaginal deliveries in animals with a history of one prior elective caesarean operation (n = 56) were evaluated retrospectively. The overall subsequent pregnancy rate was 95%. Multivariable statistical analyses did not reveal any significant influence of planned caesarean surgery on subsequent conception, stillbirth, perinatal lamb mortality, lamb birth weights, or the incidence of premature foetal death (mummification and abortion). A significantly higher number of mating attempts was, however, necessary. Also, a significant reduction in litter size was seen in the first pregnancy immediately following a surgical delivery in comparison to animals which had previously only delivered vaginally (p = 0.001), but litter size returned to pre-caesarean levels in further follow-up pregnancies in animals with a history of one elective caesarean section (p = 0.436). Subsequent long-term reproductive performance of sheep following elective caesarean section is thus excellent, and the results encourage retention for breeding.

46 Use of soy hull as a supplement during late gestation and lactation for landrace hair sheep ewes in a forage-based system

Abstract Forage-based production systems can be limiting in providing adequate nutrition as the result of seasonal fluctuations in forage quality and quantity, especially during periods of increased nutritional demands such as late gestation and lactation. This study evaluated the use of an agro-byproduct supplementation (soy hull) to fill these demands. Barbados Blackbelly (BB) and St. Croix (STX) hair sheep ewes were bred November 1 in a 25-d breeding season in two single-sire groups to like breed sires, and initially managed as one group. Pregnant ewes (n = 36) were allocated, balanced by breed, parity and fetal numbers to either a corn/soybean (CS) or soy hull (SH) supplementation starting the last trimester of pregnancy. Ewes rotationally grazed predominantly fescue pastures subdivided into 6 sections (0.13 ha) using electro-netting (3 sections of 6 ewes per supplement type). Ewes were supplemented at either 0.75% BW (late gestation) or 1.5% BW (lactation) using a single group feeder per section. Ewes lambed on pasture and lambs were weaned at approximately 63 d. Lambs had access to the supplement provided to their dams. Data were collected on ewe BW changes and reproductive performance, and analyzed in a model with supplement type and breed as main effects. Results are presented as LSM. Supplement type had no effect on ewe prepartum (54.7 kg), postpartum (47.3 kg) and weaning BW (44.7 kg), whereas BW was consistently heavier in STX than BB ewes. Ewe late gestation (61 g/d) and lactation ADG (-51 g/d) were not affected by supplement type though breeds differed (P &amp;lt; 0.01) in lactation ADG (BB: -14 vs STX: -78 g/d). Lambing performance was also not affected by supplement type with 1.97 lambs born live, and 1.69 lambs weaned per ewe. There was a supplement type by breed interaction (P &amp;lt; 0.05) for number of lambs weaned with STX ewes receiving SH having a larger litter size at weaning than ewes receiving CS (1.40 vs. 2.10 lambs per ewe) with no difference in BB ewes (1.71 vs. 1.50 lambs per ewe, respectively). Neither litter birth (6.14 kg) and weaning weights (19.9 kg) nor litter ADG (233 g/d) were affected by supplement type. Litter BW was significantly greater (P &amp;lt; 0.01) in STX than BB (6.85 vs 5.18 kg), but not different at weaning. Lamb birth and weaning weights were not affected by supplement type, though preweaning ADG tended (P &amp;lt; 0.1) to be greater in CS than SH (162 vs. 142 g/d). Data indicate that substituting SH for a more traditional corn-based supplement in landrace hair sheep ewes managed in a pasture-based system did not affect ewe growth, reproductive performance, and lamb performance. Agro-byproduct supplementation should be explored further for use in sustainable, forage-based sheep production systems.

57 Impact of Cache Valley Virus in an Arkansas sheep flock

Abstract Cache Valley Virus (CVV) is an arbovirus transmitted between mosquitos and several vertebrate species, including small ruminants. Infections in adult sheep and goats is generally subclinical, but infection during pregnancy is a growing animal welfare issue as it can result in embryo or pregnancy loss, fetal malformation, and dystocia. Diagnosis in fetal tissue or neonates is made using serologic or molecular testing. Serologic diagnosis in the dam can indicate past infection but does not confirm CVV infection in the fetus. ARS first noted clinical signs of possible CVV during the Nov/Dec 2015 lambing; first seropositive dam was identified in Jan 2021. To estimate incidence of CVV infections among ewes bred from 2019-2023 and lambing in Jan/Feb (n = 185), adverse pregnancy outcome such as embryo loss, birth of dead, deformed, or weak lambs, were used as surrogate markers. The relationship of animal BW (ewes at breeding and post-breeding; lambs at birth and ~60 d of age), dam age, lamb outcome, and breeding year were compared by likely CVV infection status. To estimate seroprevalence in ewes and correlate serology results with pregnancy outcomes, serum was collected from ewes (n = 46) exposed to rams in Aug 2022 at 0 (first day of ram exposure) and ~60 d later. Tissue from aborted or dead lambs and serum from live lambs exhibiting signs of CVV (swollen joints, parrot mouth, deformities) were collected. Serum was screened for neutralizing antibodies using a CVV-specific plaque reduction neutralization test using a 50% cut-off (PRNT50). For this preliminary analysis, specimens with PRNT50 antibody titers ≥ 10 were considered positive. Tissue specimens were tested using bunyavirus and CVV RT-PCR. Data were analyzed by GLM (SAS). Using surrogate markers, an estimate of incidence of CVV during pregnancy was 26.5 ± 2.9% without year differences (P = 0.16) or age (yearling vs older ewes, P = 0.44). There was no association between CVV and dam BW (P &amp;gt; 0.10), number of live+dead lambs born, but CVV possibly reduced number of live lambs by 18% (P = 0.02) and those weaned by 27% (P = 0.002). Live litter birth (CVV, P &amp;lt; 0.001) and weaning BW (CVV × year, P = 0.04) were reduced by CVV. Of 42 ewes bred in Aug 2022, 9 (21%) had a positive titer in Aug (pre-pregnancy) indicating possible past infection, 3 (11%) seroconverted in Oct, indicating possible infection during pregnancy. Of those, 2 (6.7%) had adverse pregnancy outcomes, including one stillbirth with deformities that had a positive RT-PCR on kidney tissue. Further studies are needed to determine whether CVV is becoming more widely prevalent in small ruminants, as are new technologies for early detection and prevention.

Genetic parameters for ewe lifetime productivity traits in Central Anatolian Merino sheep

Rapidly increasing population size, recent breaks in production and supply chains, due to pandemics, and those further expected because of climate change emphasize the compelling importance of animal productivity. Traits associated with the productivity of ewes have a direct impact on the overall productivity, profitability and efficiency of sheep farms. Therefore, the objective of the current study was to estimate the variance components, heritabilities as well as genetic and phenotypic correlations, for traits associated with the lifetime productivity of Central Anatolian Merino ewes. Birth and weaning records of lambs for each ewe as well as environmental factors such as sex and birth type were utilized for deriving ewe lifetime productivity traits. Genetic parameter estimations involved observations from 3101 Central Anatolian Merino ewes, encompassing mean and total lamb birth weight per ewe (MBW and TBW), mean and total lamb weaning weight per ewe (MWW and TWW), and the mean and total number of lambs weaned (MNLW and TNLW). This analysis utilized a pedigree comprising 13229 animals. Average Information Restricted Maximum Likelihood (AIREML) based Animal Linear Mixed Model estimations for the decomposition of (co)variance components were implemented based on pedigree-derived numerator relationship matrix by also accounting for the number of parities as a fixed factor. Low to moderate heritability estimates, ranging between 0.29 and 0.42, were observed for the lifetime productivity traits of the breed. A wide range of genetic and phenotypic correlations (between −0.56 and 0.99) was observed among the traits of interest. The outcomes of the study are anticipated to significantly enhance the global sheep production systems by uncovering the essential parameters for incorporating ewe’s lifetime reproductive performance and productivity into the selection indices. This will also benefit Central Anatolian Merino farmers, who form a large proportion of sheep producers in Turkey.

Influence of the chest wall on respiratory function at birth in near-term lambs.

Airway liquid is cleared into lung tissue after birth, which becomes edematous and forces the chest wall to expand to accommodate both the cleared liquid and incoming air. This study investigated how changing chest wall mechanics affects respiratory function after birth in near-term lambs with different airway liquid volumes. Surgically instrumented near-term lambs (139 ± 2 days) were randomized into Control (n = 7) or Elevated Liquid (EL; n = 6) groups. Control lambs had lung liquid drained to simulate expected volumes following vaginal delivery. EL lambs had airway liquid drained and 30 mL/kg liquid returned to simulate expected airway liquid volumes after elective cesarean section. Lambs were delivered, transferred to a Perspex box, and ventilated (30 min). Pressure in the box was adjusted to apply positive (7-8 cmH2O above atmospheric pressure) or negative (7-8 cmH2O below atmospheric pressure) pressures for 30 min before pressures were reversed. External negative pressures expanded the chest wall, reduced chest wall compliance (CCW) and increased lung compliance (CL) in Control and EL lambs. External positive pressures compressed the chest wall, increased CCW and reduced CL in Control and EL lambs. External negative pressure improved pulmonary oxygen exchange, reducing the alveolar-arterial difference in oxygen (AaDO2) by 69 mmHg (95% CI [13, 125]; P = 0.016) in Control lambs and by 300 mmHg (95% CI [233, 367]; P < 0.001) in EL lambs. In contrast, external positive pressures impaired pulmonary gas exchange, increasing the AaDO2 by 179 mmHg (95% CI [73, 285]; P = 0.002) in Control and by 215 mmHg (95% CI [89, 343]; P < 0.001) in EL lambs. The application of external thoracic pressures influences respiratory function after birth.NEW & NOTEWORTHY This study investigated how changes in chest wall mechanics influence respiratory function after birth. Our data indicate that the application of continuous external subatmospheric pressure greatly improves respiratory function in near-term lambs with respiratory distress, whereas external positive pressures impair respiratory function. Our findings indicate that, during neonatal resuscitation at birth, the forces applied to the chest wall should not be ignored as they can have a major impact on neonatal respiratory function.

Mating Season Influences Placental Characteristics, Plasma IGF Concentration, and mRNA Expression without Affecting Lamb Birth Weight in Akkaraman Ewes

Seasonal variations significantly impact lambs’ birth weight and post-natal growth of lambs, yet the underlying physiological mechanisms remain insufficiently explored. Therefore, this study examined the effects of mating season on lamb birth weight, placental characteristics, maternal concentrations of insulin-like growth factors (IGFs) in plasma, and placental mRNA expression levels of IGFs in Akkaraman ewes reared under extensive conditions. Ewes were mated in the breeding season (September; n = 35) and out-of-breeding season (April; n = 27). Blood samples were taken from the jugular vein of all ewes using a vacutainer in sterile heparin tubes every month from mating to parturition. Post-lambing, both dam and lamb weights were recorded, and placental characteristics were documented within 12 hours of parturition in both seasons. The number and weight of cotyledons were higher (P&lt;0.05) in ewes mated during the breeding season than those mated during the out-of-breeding season. Also, ewes mated during the breeding season demonstrated thicker large cotyledons (P&lt;0.05). Although placental and cotyledonal efficiencies were similar in both mating seasons, volumetric cotyledon efficiency was higher (P&lt;0.05) in ewes mated during the out-of-breeding season than in those bred during the breeding season. Additionally, ewes mated in the breeding season exhibited higher plasma concentration of IGF-I at three months of gestation than ewes mated in the out-of-breeding season (123.8 ± 9.8 vs. 99.3 ± 11.4 ng/ml, respectively; P&lt;0.05). Although the mating season did not affect the IGF-I gene’s placental mRNA expression levels, the IGF-II gene’s expression level was notably higher (P&lt;0.05; fold change: 2.84) in ewes mated during the breeding season. The results suggest that mating season influences placental characteristics, maternal plasma IGF-I concentrations, and IGF-II gene expression levels of cotyledons due to alterations in cotyledon numbers and size on the surface of the placenta.

The effect of repeated lipopolysaccharide endotoxin challenge on immune response of breeding ewes and subsequent lamb performance.

Infectious disease caused by exposure to Gram-negative bacterial endotoxin lipopolysaccharide (LPS) is recognized to suppress female fertility. However, the effect of varying low-dose endotoxin exposure during distinct stages of follicle development on immune response, reproductive performance, and lamb performance has yet to be elucidated. Therefore, the objective of this study was to evaluate acute phase response, mRNA abundance of inflammatory markers, reproductive performance and lamb growth characteristics of ewes challenged with subclinical doses of LPS. Rambouillet ewes (n = 36; 68.2±1.1kg; age 3 to 7 yr) stratified by body weight (BW) and age were assigned to treatment groups. Ewes received subcutaneous injections of saline (CON, n = 12), 1.5 µg/kg BW LPS (LOW, n = 12), or 3.0 µg/kg BW LPS (HIGH, n = 12) on days 5, 10, and 15 of a synchronized follicular wave. Ewes were subsequently placed with a raddle-painted ram on day 16 for a 35-d breeding season. On treatment days 5 and 15, blood samples, peripheral blood leukocytes, and rectal temperature were collected before and at regular intervals for 12h after LPS challenge. Immune response to LPS was confirmed by increased temperature and serum cortisol concentrations on days 5 and 15. Endotoxin increased circulating plasma concentration of the acute phase protein, haptoglobin by greater than 15%, in both LPS-treated groups on days 5 and 15 at 12h compared with control (P≤ 0.05). Pro- and anti-inflammatory mRNA gene expression demonstrated no differences in expression for tumor necrosis factor-α or peroxisome proliferator-activated receptor gamma among treatment groups (P > 0.10). Likewise, Toll-like receptor 4 (TLR4), interleukin-8 (IL-8), and superoxide dismutase 2 (SOD2) expression was similar among treatment groups on day 5. However, ewes challenged with LPS on day 15 displayed greater mRNA expression for TLR4 from 2 to 6h (P < 0.05), a 7-fold increase for IL-8 from 1.5 to 2.5h (P < 0.05), and 8-fold induction for SOD2 from 2 to 6h (P < 0.05) as compared with controls. First service conception rates were 90% for control ewes and 75% for both treated groups (P = 0.84). Treated ewes demonstrated a reduction in lamb birth weight compared with controls (P ≤ 0.05) and a tendency for reduction of 60-d adjusted weaning weight (P = 0.09). Data suggest that subacute endotoxin exposure aligning with key follicle and oocyte maturation events results in detrimental growth performance of the subsequent lamb.

PRESERVATION AND THERMOREGULATION PECULIARITIES OF LAMBS OF DIFFERENT TYPES OF BIRTH AND BODY WEIGHT

The research was carried out on 1421 lambs of different genders and types of birth (singles, twins and triplets) of the Kharkiv intrabreed type of the Precos breed, as well as the aboriginal Sokolska breed (19 heads). It had lasted for two adjacent years, while ewes were lambing in January-February at the experimental farm of the institute “Hontarivka” in the Kharkiv oblast, the following parameters were measured: the body weight of the lambs (BW), their type of birth (TB) and the character of the hair cover (HC), the age on the mortality date (MA), rectal body temperature (RT), body surface temperature in the chest area (ST), temperature (T) and air humidity (H) and other indicators of the microclimate in the premises. Research has established that the year of birth is an influential factor in relation to (BW) and homogeneity of lambs. The average (BW) of all newborn lambs differed by 6.2% in the compared years for a statistically highly probable difference. There were more than 12% of differences in this trait among single lambs. The indicators of the phenotypic variation of this trait in the herd also differed significantly by year. In general, the level (MA) of lambs in the period from birth to weaning was 6.2-7.9%, and the lambs that died had lower body weight than the average of the sample for the years of evaluation, from 7.7% to 14.2% (р&lt;0.001 in both cases). Although most lambs (from 20 to 38%) died in the first three days after birth, research has not established the probable repeatability of the structure (MA) of lambs in adjacent years, r±mrs=+0.714±0.350 (p&gt;0.5). It is more natural that the total number of lambs that died falls on the first 30 days of their life – 39% (2020) and 57.5% (2021). Studies of changes (ST) during the first hour of life of lambs revealed features related to the type of their birth. Twins and triplets had a relatively greater decrease (ST), namely 3.9 0C (14.2%, p&lt;0.01) in twins and 3.7 0C (13.1%, p&lt;0.001) in triplets, while in singles it was only 1.1 0C (4.1%). The change in body temperature during the first hour of life has a correlation of +0.445 with (BW) of lambs. At the age of 20-25 days, lambs of the Precos breed with a typical merino type of wool cover prevailed in (BW) from 4.3% to 13.7% with an improbable difference and in (ST) 11.6% and 16.7% (p&lt;0.001 in ram lambs and (p&lt;0.01 in ewe lambs) over the peers, who had a wool cover of the “doghair” type. The obtained results of this work are important for the further selection of sheep regarding the increase of body weight at the birth of lambs and the homogeneity of the wool cover.

Combined purebred and crossbred genetic evaluation of Columbia, Suffolk, and crossbred lamb birth and weaning weights: systematic effects and heterogeneous variances.

Despite the benefits of crossbreeding on animal performance, genetic evaluation of sheep in the U.S. does not directly incorporate records from crossbred lambs. Crossbred animals may be raised in different environments as compared to purebreds. Systemic factors such as age of dam and birth and rearing type may, therefore, affect purebred and crossbred performance differently. Furthermore, crossbred performance may benefit from heterozygosity, and genetic and environmental variances may be heterogeneous in different breeds and their crosses. Such issues must be accounted for in a combined (purebred and crossbred) genetic evaluation. The objectives of this study were to i) determine the effect of dam age and birth type on birth weight, and dam age and birth-rearing type on weaning weight, in purebred and crossbred lambs, ii) test for heterogeneous genetic and environmental variances in those weights, and iii) assess the impact of including weights on crossbred progeny on sire estimated breeding values (EBV). Performance records were available on purebred Columbia and Suffolk lambs. Crossbred information was available on lambs sired by Suffolk, Columbia or Texel rams mated to Columbia, Suffolk, or crossbred ewes. A multiple-trait animal model was fitted in which weights from Columbia, Suffolk, or crossbred lambs were considered different traits. At birth, there were 4,160, 2,356, and 5,273 Columbia, Suffolk, and crossbred records, respectively, with means (SD) of 5.14 (1.04), 5.32 (1.14), and 5.43 (1.23) kg, respectively. At weaning, on average at 122 (12) d, there were 2,557, 980, and 3,876 Columbia, Suffolk, and crossbred records, respectively, with corresponding means of 39.8 (7.2), 40.3 (7.9), and 39.6 (8.0) kg. Dam age had a large positive effect on birth and weaning weight in pure and crossbred lambs. At birth, however, the predicted effect was larger in crossbred and Suffolk lambs. While an increase in a number of lambs born and reared had a strong and negative influence on birth and weaning weight, the size of the effect did not differ across-breed types. Environmental variances were similar at birth and weaning, but additive variances differed among breed types for both weights. Combining purebred and crossbred information in the evaluation not only improved predictions of genetic merit in purebred sires but also allowed for direct comparisons of sires of different breeds. Breeders thus can benefit from an additional tool for making selection decisions.

Effects of Dam and Sire Breeds on Lamb Carcass Quality and Composition in Pasture-Based Systems.

This study explored the impacts of sire and dam breed on carcass quality and composition in a pasture-based system and the use of DXA to rapidly rank carcasses for leanness. Southdown (SD) and Suffolk (SF) ewes were mated to Texel (TX) or SD rams to produce seventy-nine lambs. Lambs were raised on pasture-based systems with limited grain supplementation. Lamb birth weight was greater (p < 0.01) for TX, regardless of dam breed. Lambing rate was lower (p < 0.01) for SD than SF ewes. Circulating myostatin concentrations were greater (p < 0.05) on d 42 than d 75 or d 110 but did not differ by sire breed. Texel-sired lambs had greater (p < 0.01) carcass weight, ribeye area and quality grade compared to SD-sired. Total and primal fat mass as predicted from DXA was higher (p < 0.05) in carcasses from SD than TX sires. Muscles from TX lambs had greater (p < 0.05) polyunsaturated fatty acid (PUFA) composition than SD-sired. Shear force values were influenced (p < 0.01) by dam breed, muscle cut and postmortem age but not by sire breed. The use of TX sires in pasture-based systems improved carcass leanness and muscle PUFA concentrations without altering tenderness.