Survival Rate Of Lambs Research Articles

Factors influencing Awassi lambs survivorship under fields conditions

The objective of this study was to investigate the pre-weaning survival rates of Awassi lambs and identify the causes of death in extensive and semi-extensive production systems. The study was designed to collect data under field conditions. Data were recorded on 29,290 lambs born alive during lambing seasons from 2011 to 2015. Postmortem autopsy findings were collected from 5448 lambs died during the pre-weaning period. About 63.5% of losses occurred during the first 7 days of life. The overall pre-weaning mortality rates were 19.7% and 16.9% in the extensive and semi-extensive production systems, respectively. Lamb birth weight had a strong effect (P<0.0001) on the pre-weaning mortality rate. The mean mortality rate in lambs weighed <2kg at birth was 45.1%. The proportion of autopsied lambs dying by category was starvation (28.6%), respiratory infections (19.2%), gastrointestinal infections (16.2%), birth injuries (10.2%), hypothermia (8.6%), enterotoxaemia (8.2%), dystocia (4.4%) and predation (2.1%). Explanatory variables best used by Weibull model to estimate the hazard ratio (HR) of lambs falling into a certain death category were production system, lamb sex, birth type, and lamb birth weight. Lambs born in extensive production system were more (P<0.0001) likely to die from starvation (HR=4.6), gastrointestinal infections (HR=3.2), and hypothermia (HR=2.2), compared with semi-extensive system. Lambs weighed <2kg at birth were more (P<0.0001) likely to die from starvation (HR=5.5), hypothermia (HR=3.6), gastrointestinal infections (HR=2.4) and respiratory infections (HR=2.2), compared with lambs weighed 3–4kg. Triplet lambs were 4.6 more (P<0.0001) likely to die from hypothermia and 4.3 more (P<0.0001) likely to die from starvation. Survival rates of Awassi lambs can be improved by applying appropriate management practices that target intermediate birth weights and minimize the infectious diseases, starvation and cold stress.

Sustainability of Meat Sheep Production in Relation to Health and Reproduction Traits

Meat sheep production in most countries relies on grazing and profitability (gross margin per ewe and per year) is low. Profitability is in part based on the level of numeric productivity (number of lambs produced per ewe and per year). Numeric productivity depends on fecundity and survival rates of ewes and lambs. These survival rates are extremely variable from one farm to another. These variations are detrimental to sustainability of the farms. We will study the mortality rates of ewes and lambs and other health related traits, taken as indicator in meat sheep farms in different locations-plain or semi-mountain areas (34 farms) in relation to gross margin taken as an indicator of economical sustainability as well as other markers of sustainability. We constructed a method for evaluating sustainability based on the above mentioned parameters in the field of production, animal health, and economics. It was based on two step procedure: first, selection of farm parameters using clustering methods, second ranking farms on sustainability using principal component analysis with an orientation obtained by the incorporation in the analysis of two virtual farms (high and low sustainability) constructed on a choice of sustainability for each parameter. This choice of sustainability is flexible and dependant on the views of stakeholders and may modify the ranking of farms. The scale of sustainability we proposed was tested in relation to the management of the farm (organic or conventional) and location (plain or semi-mountain areas): the semi-mountain farms were more sustainable than plain farms and organic farms were often, but not always, more sustainable than conventional farms. The method can be easily applied to any animal production.

Molasses-based supplement improved the metabolic status of late-pregnant ewes bearing multiple fetuses

Metabolizable energy requirements rise dramatically at late gestation in ewes bearing multiple-fetuses; consequently, prolific ewes may suffer pregnancy toxemia and fetal intrauterine growth restriction. The present objectives of this study were to examine in ewes bearing ≥2 fetuses, the effects of dietary supplementation with a molasses-based product from 90 d of pregnancy until lambing on dams' metabolic status and perinatal lambs' performance. Fifty Afec-Assaf ewes, genetically bred to achieve multiple-fetus pregnancies, and bearing at least 2 fetuses were included in the study. The ewes were divided into two groups according to predicted number of fetuses, lambing time, parity number, and body weight (BW). The control group (CTL) was fed solely a basal diet; the treatment group (MLS) was fed the same diet supplemented with the molasses-based product ENERGILASS Sheep 15, in free-choice tubs. Blood samples were collected weekly. Average litter sizes were 3.06 and 3.19 for CTL and MLS groups, respectively. Fetal survival rates at birth differed insignificantly (P>0.05) at 0.82 and 0.84 in the CTL and MLS group, respectively, and the survival rate of lambs until weaning was insignificantly 6.8% higher in the MLS than in the CTL group (P>0.05). The CTL ewes lost 0.40 body condition score units from 90 d of pregnancy until lambing compared with only 0.15 by the MLS ewes (P<0.05). The average concentration of glucose in plasma during the last 3 wk of pregnancy was 17.3% higher in MLS than in CTL ewes (59.1 vs 50.4mg/dL, respectively; P<0.01), whereas the BHBA concentrations were 30.9% lower (0.67 vs 0.97mmol/L, respectively; P<0.03) and NEFA concentrations were 30.0% lower in the MLS than in the CTL ewes (P<0.007). During the last 3 wk of pregnancy glucose concentrations were ≤50mg/dL in 37/70 and 16/72 of the CTL and MLS blood samples, respectively (P<0.0002). Also, BHBA concentrations ≥1.4mmol/L were found in 19/70 and 6/72, respectively, of the CTL and MLS blood samples (P<0.003). In conclusion, molasses-based product supplementation to prolific ewes from 90 d in pregnancy until lambing greatly improved the metabolic status of dams but with minor effects on perinatal survival and growth of lambs, suggesting that the extra nutrients consumed were prioritized to dams rather than to the components of the gravid uterus.

Genetic analysis of Lori-Bakhtiari lamb survival rate up to yearling age for autosomal and sex-linked

The data set used in this study contained 8793 records of lamb survival rate from 320 sires and 2349 dams collected during 1989–2014, from the Lori-Bakhtiari flock at Shooli station in Shahrekord province, Iran. The data were analyzed using a linear mixed-model including fixed factors such as year and month of birth, sex of lamb, birth rank, age of dam, lambs birth weight as quadratic covariate and dam body weight as linear covariate and direct additive genetic (partitioned into autosomal and sex-linked), maternal additive genetic and residual random effects. Genetic parameters and breeding values of cumulative lamb survival rate from birth up to yearling age (at 1, 2, 3, 6, 9 and 12 months) were estimated using restricted maximum likelihood procedure. The results showed that the overall mean of the cumulative survival rate of lamb up to yearling (12 months of age) was 80.85%. The effect of fixed factors; year and month of birth, sex of lamb and lamb birth weight as quadratic were significant (p<0.05). The effect of age of dam and birth rank and dam body weight were not significant (p>0.05) on survival rate. The heritability estimates of survival rate were low and ranged from 0.04 to 0.08 for autosomal, 0.01 to 0.02 for sex-linked and 0.01 to 0.02 for maternal additive genetic effects. The estimates of autosomal, sex-linked and maternal genetic correlations of survival rate in different ages were high. The overall mean of autosomal and sex-linked breeding values of survival rate were greater than zero and increased by age of lamb. The Pearson and Spearman correlation coefficients between autosomal breeding values and sex linked breeding values in survival rate at different ages were 0.20–0.54 and 0.18–0.53 respectively.Thus, lamb survival rate up to yearling can be improved by farm management practices and improving environmental factors. Based on the genetic parameters estimated, the response to genetic selection would be slow, but would also be cumulative. However, genetic analysis using linear models which able to estimate genetic variation and breeding values in autosomal, sex-linked and maternal separately, could be more effective to improve survival rate in lambs.

L-Arginine Modulates Maternal Hormonal Profiles and Neonatal Traits during Two Stages of Pregnancy in Sheep

A 2 × 2 factorial arrangement was designed to test effects of supplementation of a low (L, 75 mg/kg BW) vs. high (H, 150 mg/kg BW) L-arginine given at early (first 56 days) vs. late (last 56 days) pregnancy on maternal hormones and neonatal traits. Thirty Najdi pregnant ewes were randomly allocated into 6 groups. Ewes in G1 and G2 served as controls (C), given 50 ml saline at either early (CE) or late (CL) pregnancy, respectively. G3 and G4 ewes in early pregnancy received low (LE) and high L-arginine (HE), respectively. G5 and G6 ewes in late pregnancy received low (LL) and high (HL) L-arginine, respectively. A weekly blood sample was collected from initiation of the treatment till parturition. Serum growth hormone (GH), insulin-like growth factor-I (IGF-I), insulin, progesterone (P4) and estradiol 17 β (E2) profiles were determined. Neonatal traits were also determined. Insulin was higher (P 0.05). Lamb survival rates at birth in LE ewes were highest (100%) compared to other treatments. In conclusion, supplementing pregnant ewes with low dosage of L-arginine at early stage of gestation increased lamb birth weight and survival, and improved maternal health.

The case for pre-parturient selenium and iodine supplementation of ewes for improving lamb survival

Lamb survival is an issue of high relevance to the Australian sheep industry, as lamb-survival rates have direct bearing on overall reproductive performance of the sheep, and also constitute a main concern from an animal welfare perspective (Mellor and Stafford 2004). Both genetic and management factors play an important role in this complex issue (Hinch and Brien 2014). Ewe nutrition is of particular relevance as the intrauterine growth conditions prepare the lamb for the crucial transition to life outside the uterus. Effects of body condition of the ewe during various stages of the pregnancy have been investigated in detail, yet much less is known about the critical role of micronutrient provision to the ewe. Although several risk factors for selenium (Se) and iodine (I) subclinical deficiencies exist for sheep on pasture in Australia, determining micronutrient status in sheep or pasture is not straightforward. Several studies have separately found effects of Se and I supplementation on lamb survival. Studies investigating the interaction of Se and I supplementation have been few but results have demonstrated an interaction between Se and I. With increased twinning rates as a result of increased selection of numbers of lambs weaned, nutritional demands during pregnancy across flocks are increasing, and effects of micronutrients on lamb health and survival have greater impact. New opportunities in nutritional research are encouraging new studies into the effects of Se and I supplementation on lamb survival.

Effects of ewe live weight and age on reproductive performance, lamb growth, and survival in Central Anatolian Merino sheep

&lt;p&gt;&lt;strong&gt;Abstract.&lt;/strong&gt; The aim of this study was to evaluate the effects of premating ewe weight and age on ewe reproductive performance, lamb growth and survival in Central Anatolian Merino (CAM) sheep. &lt;br&gt;&lt;br&gt; The trial included 4935 ewes and 5548 lambs from 23 breeder flocks in Eskişehir Province. The live weights (LWs) and ages of the ewes were recorded 1 week before the mating season. The number of lambs born, fertility rate, multiple birth rate (MBR), and lamb survival rate (SR) at days 75 and 120 were determined. The effects of the LW and age of the ewe were found to be important for the reproductive performance of ewes and for the lamb's growth rate (&lt;i&gt;P&lt;/i&gt; &lt; 0.05–0.001). Ewe MBRs and the birth weight (BW) and LW of the lambs at days 75 and 120 increased proportionally with the increase in LW in ewes prior to mating. The fertility rate and MBR were lower (&lt;i&gt;P&lt;/i&gt; &lt; 0.05–0.001) in 1.5-year-old ewes than in older ewes. However, lambs' SR at days 75 and 120 were not affected by the premating LW and age of the ewe. In summary, a better reproductive performance and lamb growth rate in CAM flocks may be achieved by the selection of breeding ewes from ewes weighing more than 60 kg.&lt;/p&gt;

Two treatment protocols for induction of preterm parturition in ewes—Evaluation of the effects on lung maturation and lamb survival

Lambs born prematurely are often unable to breathe due to pulmonary immaturity and a lack of surfactant production. Attempts to deliver live, moderately preterm lambs from critically ill ewes in late pregnancy are therefore often unsuccessful. The objective of this study was to evaluate the potential benefits of repeated administration of dexamethasone (DEXA) to final-stage pregnant ewes on subsequent perinatal lamb survival and respiratory and metabolic disorders associated with neonatal asphyxia. Two different treatment protocols with dexamethasone were used to induce parturition on days 137 and 138 of pregnancy (full term 149 days).In group LTP (long-term protocol, n=12) low doses of dexamethasone were administered repeatedly starting with 2mg once daily on days 130–133, followed by a single dose of 4mg on day 134. For the final induction of parturition 16mg of the drug were administered on day 135 and this dose was then repeated every 12h until lambing. In group STP (short-term protocol) 15 ewes received 16mg DEXA on day 135, followed by the same dose every 12h until lambing. The vitality and laboratory parameters of the lambs born to these dams were compared to lambs delivered by caesarean section (group CS) on day 147 or 148 of gestation whose dams (n=23) had received a single injection of 10mg dexamethasone 12h prior to surgery, and to lambs born naturally to 19 ewes at full term (group FT) after an average of 149 days of gestation.Lambs from groups LTP and STP were born between day 137 and 139 of gestation, showing characteristics of immaturity. Of 18 lambs in group LTP, 16 survived without critical care (88.9%; 95% confidence interval (CI)=67.2–96.9%). Group STP comprised 24 lambs, 18 of which survived without critical care (75%; 95% CI=55.1–88.0%). Out of 39 lambs in group CS, 37 survived (94.9%; 95% confidence interval (CI)=83.1–98.6%), and 27 of the 28 lambs in group FT, respectively (96.4%; 95% CI=82.3–99.4%). There was no statistically significant difference in the survival rates between the four groups. In all four groups there was a significant increase of pH, BE and HCO3− values within the first 24h post natum, and a significant decrease in pCO2(v) values.Compared to previous studies which indicated high mortality rates in moderately preterm lambs the results indicate that repeated exogenous administration of DEXA has a positive effect on the survival rates of lambs born after induced parturition at around 92% of the full pregnancy term.

Calculating economic weights for growth, reproduction and wool traits in Makui sheep breed by Ecoweight software

Production, reproduction, management and economical parameters obtained from data collected from 1993 to 2012 Makui sheep research station of West Azerbaijan province in Iran were evaluated in the present study. Traits included of fertility, pregnancy rate, lamb weights from birth to the end of period, survival rate of lambs, wool production weight, average daily gain and milk production. The present value of profit computed as the difference between total revenues and total costs per ewe per year. The numeric derivation of each considered trait is calculated by increasing and decreasing the average value of the trait while was kept the other characters in the average. First all costs, revenues, profits and flock structure determined then interned input files and running the software ECOWEIGHT. The results showed that economic values per unit increase in the traits of birth weight, daily gain from birth until weaning, daily gain from weaning until end of period, conception rates ewes, little size, lamb survival, lifetime for ewes, milk yield and wool yield were 0.66, 0.51, 0.03, 0.66, 0.25, 0.85, 0.93, 0.53 and 1, respectively. Breeding objective in Makui sheep breed were productive wool yield, lifetime, lamb survival at weaning, conception rates ewes, birth weight, milk yield, daily gain from birth until weaning, little size, daily gain from weaning until end of period.

Effect of live weight and age of Akkaraman ewes at mating on multiple birth rate, growth traits, and survival rate of lambs

This study was performed in order to determine the effect of live weight (LW) and age of Akkaraman ('White Karaman', WK) ewes at mating on the multiple birth rate (MBR), growth traits, and survival rate (SR) of lambs in breeder flocks. In the trial, data of 4452 head of ewes and 5324 head of lambs obtained from 16 WK breeder flocks in Konya Province were used. One week before the mating season ewes were weighed and separated into 5 groups according to their LW. In the research, the differences of MBR, the SR of lambs until days 60 and 120, the birth weight (BW), and the average LWs at days 60 and 120 between the groups were found to be statistically significant. It was determined that the MBR, the SR of lambs, the BW, and the average LWs at days 60 and 120 increased directly proportional to the LW increase of WK ewes at mating. Ewe's age affected MBR significantly and the MBR of ewes of ages 2 and 3 was lower (P < 0.01) than those of other age groups. However, ewe's age did not affect SR up to days 60 and 120, BW, or growth of lambs.

Growth traits and survival rates of Akkaraman lambs in breeder flocks in Konya Province

This trial was carried out to determine the growth traits and survival rates of Akkaraman (‘White Karaman’ in Turkish, WK) lambs in breeder flocks in Konya Province. In this study, the effects of birth year, lamb’s sex, birth type, dam’s age, and farm on the birth weight (BW), weaning weight (WW) at day 75, live weight (LW) at day 120, and average daily weight gain (ADWG) of lambs were investigated. Survival rates of lambs up to weaning were determined based on years. Data were collected from 19,207 lambs born between the years of 2007 and 2010 in 2 different villages of Konya Province in Turkey. The overall BW, WW, LW at day 120, ADWG, and survival rate of lambs were found as 4.05 kg, 19.5 kg, 31.7 kg, 231 g, and 91.4%, respectively. All of the investigated factors had significant effects on the BW, WW, and LW at day 120 and ADWG of lambs (P < 0.01). Differences between the survival rates of lambs were significant (P < 0.01). These results showed that birth year, sex of lamb, birth type, dam’s age, and farm have important effects on the growth of WK lambs. It can also be said that the genetic capacity for rapid growth and ADWG of WK lambs is not low.

Reproductive Performances of Indigenous Ewes in Bangladesh

The ewes were randomly divided into controlled and supplemented group to determine the reproductive performances of indigenous ewes in Bangladesh. Ewe lambs on supplemented group was growing faster and reached puberty at significantly (p 0.05) different between the two groups. The stage of the estrous cycle was determined by observing exfoliated vaginal cells in both the groups. Average progesterone concentration was significantly different (p<0.01) among days of the oestrous cycle. Progesterone concentration was <1.0 ng/ml on day of estrus, rose steadily to peak on days 10 and followed by a rapid decline on day 15 in both group. The nutritional supplement did not improve sexual behaviors. The pregnancy rates were 83.33 and 100% in controlled and supplemented groups. The gestation length varied from 141 to 145 days. The post partum onset of estrus was significantly shorter in supplemented group than controlled group (p<0.05). The lambing rates, litter size and lamb survival rate were 75 and 100%, 1.22±0.44 and .1.58±0.67 and 91.67 and 100%, in controlled and supplemented group, respectively. Mean birth weights of lambs were 1.00±0.30 and 1.33±0.25kg in controlled and supplemented group, respectively. The pre-weaning average daily gain of lambs were significantly different (p<0.01) between two groups. The present study indicates the influence of nutrition on reproductive performances of ewes that may increase and improve the sheep production.

Introduction of corriedale rams for improving meat and wool quality in hilly regions of Jammu and Kashmir

Sheep is one of the most important source of livelihood and a sustainable sourceof wool and meat for farmers in hilly areas. Sheep farming plays an important role for the upliftment of livelihood security and also improves socio-economic status of farmers in J&K hills. Sheep is a good source of wool and fibre but due to poor genetic trait for wool quality of local non-descript breeds and consequent less returns, farmers in Doda and Kishtwar have now stopped rearing sheep for wool purpose. A good breeding program is required whichresults in a flock of sheep that has a high reproductive rate, good lamb survival and good lamb growth rates. So with these points in mind pure breed Corriedale rams were introduced for breeding purpose in these hilly areas of Jammu under NAIP-Doda. Near about 20 pure bred Corriedale breeding rams were distributed among different farmers in all the three clusters near about 18 villages. Breeding in these hilly areas is mostly done twice in a year. These lambs were then used for wool or meat purpose depending on the need of farmer. Shearing of wool is done twice in a year. Wool is sold at a rate of Rs. 40-50 per Kg and meat can be sold at a rate of Rs. 230-240 per Kg. These lambs attain weight of approximately 20-25kg in a period of 1.5 to 2 years. So introduction of Corriedale ram was a great success in improving the livelihood security and generating a sustainable source of income among the farmers. Moreover it was also seen farmers were now more interested in meat production then wool production.

The comparison of some reproduction traits and lambs growth performance of ex situ and in situ conserved Kivircik sheep

The objective of this study is to compare the reproductive performance of the ewes, the lambs’ growth characteristics, and the variable costs in the sheep enterprises for ex situ and in situ conserved Kivircik sheep flocks. In total, 1841 ewes were included in the study. The ex situ Kivircik sheep flock had 929 ewes and the in situ Kivircik sheep flock had 912 ewes and their l864 lambs were born in the months of January and February from 2007 to 2011. The lambing rates of the in situ and the ex situ flocks were 83.9% and 74.7% (P<0.01), respectively, the differences in the results were significant between the conservation types. The fecundity of the in situ and the ex situ flocks was 1.1 and 1.0 lambs (P<0.01), and litter size was the same (1.3, P>0.05). The least squares means of the birth weight, the weaning weight at the 90th day of the lambs, and the post-weaning daily live weight gain of the in situ and ex situ conserved lambs were 4.2 and 3.7kg (P<0.01), 25.4 and 24.9kg (P<0.01), and 234 and 234.3g/day (P>0.05), respectively. The average mean survival rate of the in situ and the ex situ conserved lambs were 96.2% and 90.0%, respectively, and differences were significant (P<0.01) between the conservation types. In the ex situ sheep enterprises, proportional profit was 0.62, in other words, each 100€ expense corresponds to a loss of 38€. However, for the in situ sheep enterprise, this ratio was 1.17, meaning that each 100€ expense corresponds to a profit of 17€. The present study demonstrated that the in situ conserved Kivircik sheep had higher growth performance, higher lamb survival rate and was more profitable than the ex situ conserved Kivircik sheep.

Growth Performance and Survival Rates of Un-Weaned F1 German Blackheaded Mutton X Turcana Crossbred Lambs Under Organic Production System

The current research aimed to evaluate the effects of crossbreeding the Romanian native Turcana (TA) sheep breed ewes with meat specialized German Blackheaded Mutton (GB) rams on growth and survival rates in un-weaned F1 crossb red lambs reared under organic production system. At the age of 28 days the crossbred lambs registere d average body weights of 10.1±0.21 kg, while the TA purebreds achieved weights of 8.0±0.147 kg, differences between the two groups being significant (p ≤0.001). Survival rate of the lambs was not affected by genotype (p ≥0.05), both crossbred and purebreds have registered values of 9 1.6±0.04% and 93.9±0.04%, respectively. Throughout crossbreeding the indigenous Turcana ewes with German Blackheaded Mutton rams under organic production system the performance for meat production is significantly improved.

Maternal and neonatal behaviors of Ouled Djellal sheep breed and their effects on production parameters

Our study evaluated maternal and neonatal behaviors of the Algerian Ouled Djellal native sheep breed, their effects on growth and mortality of lambs from birth to weaning, and the influence of biotic factors related to mother or lamb on variation of their behaviors. Maternal behavior was scored (MBS) for 200 ewes on the day of lambing on a 5-points scale, based on the distance a ewe retreats from her lambs when lambs were handled, while neonatal behavior (NLB) was recorded for 52 lambs. The MBS for Ouled Djellal ewes indicated that 31.5% were good and 44% were excellent mothers. Multiparous ewes showed improved MBS compared to primiparous (P<0.05), and single born lambs were quicker to stand (P<0.05), to reach the udder (P<0.05) and to suckle (P<0.01) than twins, whereas both MBS and neonatal behaviors were not related to ewes age or sex of lamb. Interestingly, lamb birth weight was positively correlated to MBS (r=0.21, P<0.01) and negatively correlated to all neonatal behaviors (r=−0.70, P<0.01). Lamb weight and mortality were recorded through weaning (90 days of age). Lamb growth was not related to MBS, while there was a negative correlation between lamb growth until weaning age and the time spent by lambs immediately following birth to stand, to locate the udder and to suckle (P<0.01). Lamb mortality rates between birth and weaning decreased with an increase in MBS (P<0.01). Likewise, lamb mortality to weaning was higher among lambs who were slow to stand, to reach the udder or to suckle (P<0.01). Scoring maternal and lamb behaviors can help formulate appropriate management programs to improve lamb growth and survival rates of Ouled Djellal breed.

A comparison of the reproductive performance of ewe lambs and mature ewes

This work compared the reproductive performance of ewe lambs and mature ewes and the growth of their lambs from birth to weaning under conditions in which they had been managed as a single group. Two studies were conducted; the first study, conducted in 2007, included 307 multiparous mature ewes and 297 primiparous ewe lambs and the second study, conducted in 2009, included 399 multiparous mature ewes and 400 primiparous ewe lambs. Physical measures of ewes and lambs were recorded as was their behaviour within 12h of birth in study one. Ewe lambs were lighter (P<0.05) than mature ewes throughout pregnancy and lactation. However, the total live weight gained during pregnancy was similar (P>0.05). Lambs born to ewe lambs were smaller (P<0.05) and lighter (P<0.05) than their birth rank contemporaries born to mature ewes. However, single lambs born to ewe lambs and twin lambs born to mature ewes had similar birth weights and growth to weaning. Lamb survival rates were lowest (P<0.05) for lambs born to ewe lambs although in study two, singleton lambs born to ewe lambs had similar survival rates to both singleton and twin lambs born to mature ewes. This study identified that the limitations to ewe lamb breeding were that they produced smaller, lighter lambs with lower survival rates to weaning and maternal behaviour indicating a lack of experience compared to mature ewes. Therefore future research should be directed at alleviating these constraints.

Productive and reproductive performance of Dorper and its crossbreds under a Romanian semi-intensive management system

The overall objectives of the research were to evaluate the effect of cross-breeding Dorper (DO) rams with Turcana (TA) ewes on growth and reproductive performances of F1 DOxTA and R1 DOx(DOxTA) crossbred lambs reared under a semi-intensive management system; to study the adaptability of the DO breed to Romanian farming conditions; and to evaluate the effects of melatonin implants outside the breeding season on reproductive performances in DO ewes. Animals were managed on cultivated pastures, with an average stocking rate of 12 head/ha. Additional 200 g concentrates/day were given for 90 days during the winter season and a three lambings per two years system was practised with the use melatonin implants for oestrous induction outside the natural breeding season. Dorper and F1 crossbreds were found to be highly precocious when put to the ram as ewe lambs, with an average fertility rate of 84.2% and 79.3%, respectively, compared with 19.3% in the TA controls (CG). The litter size in adult DO ewes was 136.6% versus 118.8% for the TA (CG). Dorper-sired progeny had significantly higher body weights of lambs at weaning (90 days) compared with TA purebreds (23.8 kg, 23.5 kg, 21.5 kg, 19.4 kg for DO, R1, F1 and TA, respectively). At the age of 8 months, all three DO genotypes were significantly heavier (46.1 kg, 40.7 kg and 43.5 kg for DO, F1 and R1, respectively) compared with the TA females, who reached 32.3 kg. Average daily gain from birth to 28 days of age was significantly higher in DO purebreds and F1 and R1 crossbreds compared with TA lambs (266.4 g, 253.8 g, 223.4 g and 157.3 g, respectively). Lamb survival rates until weaning were not affected by the genotype. When using melatonin implants in the DO ewes, the fertility rate increased to 88%, compared with a fertility of 41.6% in non-treated DO ewes. Out-of-season prolificacy was not affected by melatonin treatment, with litter size being 127% and 120% in treated and non-treated DO ewes, respectively. The DO breed performed well under Romanian semi-intensive management, and proved to be a highly adaptable breed to the new rearing conditions.Keywords: Sheep, heterosis, growth, fertility rates, melatonin implants

The investigation of non-genetic factors affecting survival of Karakul lambs from birth to one year of age using linear and nonlinear models

The data used in this study were 6426 records of Karakul lambs’ length of life and survival rate from 228 sires and 1894 dams collected from year 1992 to 2009. Linear and hazard ratio models with Weibull function were used in the analyses. Factors included in the models were non-genetic factors of year and month of birth, sex of lamb, type of birth and age of dam and lambs’ birth weight fitted as linear and quadratic covariate. Results showed that the overall mean of lamb's life length and cumulative survival rate up to yearling were 274.32 days and 85.43%, respectively. The effect of year, month and type of birth, sex of lamb and lamb's birth weight as linear and quadratic covariates were significant (P<0.01). However, the effect of age of dam on length of lamb's life and survival rate was not significant (P>0.05). The survival rate and hazard ratio of lambs born in the first and second lambing month were higher and lower than the third month, respectively. The male lambs had lower survival rate and higher hazard ratio compared with females. Lambs with average birth weight had higher survival rate and lower hazard ratio than lambs with low and high birth weight. Although, lambs born from younger and older dams tended to have lower survival rate and higher hazard ratio, but they had not any significant differences with lambs born from middle age dams. Twin lambs had lower survival rate and higher hazard ratio than single lambs. According to the results obtained in this study, analyzing the effect of non-genetic factors on length of life and survival rate of lambs with linear and survival models produced the same result and these models can be used interchangeably.

MAIN PRODUCTIVE PERFORMANCE OF AWASSI SHEEP IN CENTRAL ANATOLIAN REGION OF TURKEY

This study aimed to determine milk yield, fertility, lamb growth, survival rate, and the effect of environmental factors on these parameters in the Awassi sheep of the Central Anatolian Region. The fertility parameters were determined to be as follows: heat rate, pregnancy rate, parturition rate, single-born rate, twinning rate, abortion rate, lamb rate, and number of lambs per parturition, based on the number of ewes assigned for mating, were 100%, 93.8%, 90.5%, 79.7%, 20.3%, 1.4%, 108.8%, and 1.20%, respectively. The survival rates of lambs at 60 and 120 days of age were 88.3% and 84.5%, respectively. The average lactation milk yield and lactation period of the Awassi ewes were 196.5 ± 5.60 kg and 184.3 ± 2.11 days, respectively. The general death and slaughter rate of the stock was 8.2% throughout the research period. The lactation milk yield was affected by the production year (P < 0.01) and the age of the ewe (P < 0.01), but the lactation length was not affected by the same environmental factors (P > 0.05). The results of this study have shown that the Awassi sheep raised in the Central Anatolian Region had similar lactation milk yield, fertility parameters, and survival rates as the Awassi sheep’s original race. In addition, since there were no epidemic health problems observed during the 2-year research period, Awassi sheep were shown to be adapted to being raised in this region.