Lamb Output Research Articles

Control of Strongyles in First-Season Grazing Ewe Lambs by Integrating Deworming and Thrice-Weekly Administration of Parasiticidal Fungal Spores.

Parasiticidal fungi have been used in several in vivo experiments in livestock farms worldwide, constituting an effective tool for the biocontrol of gastrointestinal parasites in grazing animals. In the first year of study, two groups of eight first-season pasturing ewe lambs infected by strongyles were dewormed with albendazole, and then, the test group received an oral dose of 106 chlamydospores of Mucor circinelloides and 106 Duddingtonia flagrans individually and thrice a week from mid-September to May (FS1), while the control group remained without fungi (CT1). In the second year, two new groups of first-season grazing ewe lambs were treated with ivermectin and subjected to the same experimental design (FS2 and CT2, respectively). The anthelmintic efficacy was 96.6% (CT1), 95.6% (FS1), 96.1% (CT2), and 95.1% (FS2). The counts of strongyle egg output increased in the control groups (CT1 and CT2) throughout the study and reached numbers higher than 600 eggs per gram of feces (EPG), while in FS1 and FS2, they were <250 EPG. The values of red blood cell parameters registered for CT1 and CT2 were lower than those of the reference standards, while a significant increment was recorded in FS1 and FS2, and values within the physiological range were attained. It is concluded that integrating efficient anthelminthic deworming with rotational pasturing and the regular intake of chlamydospores of M. circinelloides and D. flagrans provides a helpful strategy for maintaining low levels of strongyle egg output in first-season grazing ewe lambs and improves their health status.

Gestational High‐Altitude Hypoxia and Metabolomic Reprogramming in Pulmonary Arteries from Fetal Sheep

Gestational high‐altitude hypoxia increases the risk of myriad diseases in human infants including pulmonary hypertension of the newborn. Fetal sheep lungs are susceptible to long‐term intrauterine hypoxia, with the lung structure and function exhibiting characteristics associated with the development of pulmonary hypertension. Previous studies showed thickening of the pulmonary arterial medial wall, dysregulation of arterial reactivity, and reduced right ventricular output in fetal lambs following exposure to high altitude long‐term hypoxia. To further explore the mechanisms associated with hypoxia‐induced aberrations in the fetal sheep lung, we examined the premise that metabolomic and proteomic changes are associated with phenotypic transformation caused by intrauterine hypoxia. To address this hypothesis, we performed metabolomic and proteomic analysis on pulmonary arteries isolated from near term fetal lambs that were exposed to intrauterine high‐altitude hypoxia (3801 m) for the latter 110+ days of pregnancy or those gestated near sea level. The data demonstrated gestational hypoxia caused a glycolytic shift, reduced fatty acid oxidation, and elevated pentose phosphate metabolism along with increased histone expression, illustrative of increases in nucleotide synthesis. Increased nucleotide synthesis in response to gestational hypoxia is suggestive of a shift towards a proliferative and synthetic phenotype, providing insight into the mechanisms related to gestational hypoxia‐mediated pulmonary remodeling and hypertension. These studies begin to shed light on the mechanistic underpinnings associated with the phenotypic transformations to the pulmonary vasculature that occur with intrauterine hypoxia.Support or Funding InformationSupported in part by NIH grants HD083132 (LZ), 1U24DK097154 (OF ) through a pilot project grant to SMW and HD098477 (SMW). Additional support was provided by USDA Intramural projects #2032‐51530‐022‐00D and #2032‐51530‐025‐00D (J.W.N.). The USDA is an equal opportunity provider, and employer.

Differences in lamb production between ewe lambs and mature ewes

ABSTRACT Currently, comparisons of lamb output from either ewe lambs or mature ewes are confounded, as the age groups are bred to different sires, and lamb at different times. The aim of this experiment was to compare the reproductive performance of ewe lambs and mature ewes, bred at the same time to the same sires, and lambed in the same climatic conditions. The experiment included 1082 mature ewes and 1014 ewe lambs that gave birth to 2656 lambs. Birth weights of lambs were 3.92 ± 0.06 kg and 5.02 ± 0.06 kg, and weaning weights of lambs were 24.03 ± 0.24 kg and 26.68 ± 0.29 kg for ewe lambs and mature ewes, respectively. Lambs born to ewe lambs were less vigorous than lambs born to mature ewes, even when adjusted for their lighter birth weights. Lamb survival during the neonatal period was 92.2% and 97.3% for lambs born to ewe lambs or mature ewes, respectively. The effect of birth weight on survival within each dam age and lamb birth rank followed a quadratic form, and differed for each group. Farmers should preferentially allocate all ewe lambs and mature ewes bearing triplets to lamb in paddocks that provide better conditions for lambing.

Characteristics of the Romanov Breed by the BMP-15 Locus Responsible for Prolificacy in Sheep

The actual problem in identifying a prolificacy gene in Romanov breed sheep is considered. The new diagnostic method to identify the polymorphic gene of the bone morphogenetic protein 15 (BMP-15) influencing prolificacy in the Romanov sheep has been proposed based on the surveys. The frequencies of occurrence of the normal (wild-type) and mutant alleles and the genotypes present at a locus responsible for prolificacy in sheep are revealed. The quantitative indicators, including the numbers of lambs at birth and at weaning and the barren and culled ewes, were recorded with taking into consideration the genotypes at the BMP-15 locus. The correlation between the frequency of occurrence and the number of the produced posterity and among the barren and culled Romanov ewes were ascertained. It was indicated that the highest percentage of the lamb output at birth and at weaning was typical for the ewes homozygous (MM) for a mutant allele. The animals referred to as heterozygous genotypes (WM) appeared in the second position. The highest percentage of the culled and barren ewes was recorded in the carriers of the WW homozygote. Based on the obtained results, it has been concluded that the genotypes at the BMP15 locus should be taken into consideration when selecting the ewes with regard to their fertility. However, further researches into the determined phenomenon in the Romanov sheep are required to improve this performance, since multifetal pregnancies in some WW-group ewes have been registered.

Characteristics of romanov breed locus bmp-15, responsible for prolificacy of the sheep

The article deals with the actual problem, the diagnostics of the prolificacy gene in sheep of the Romanov breed. The new method for the diagnostics of the polymorphic gene of the bone morphogenetic protein 15 (BMP-15), which causes the multiple pregnancy in the Romanov sheep, has been proposed based on the carried out surveys. The frequencies of occurrence of the normal (wild type) and mutant alleles responsible for the multiple pregnancy-related locus and the genotypes in the sheep are present. The economic indicators including the numbers of newborn lambs, the lambs at winning, and the dry and culled ewes were recorded with taking into consideration the genotypes of the BMP-15 locus. The relationships between the frequency of occurrence and the number of the produced posterity and between the dry and culled Romanov ewes were ascertained. It was proved that the highest percentage of the lamb output at birth to weaning was typical for the ewes homozygous (MM) for a mutant allele. The animals referred to as heterozygous genotypes (WM) appeared to be in the second position. With respect to the wild genotype, the highest percentage of the culled and dry ewes was recorded in the carriers of the WW homozygote. The obtained results allow us to conclude that the genotype frequency at the BMP-15 locus should be taken into account while estimating the fertility of the ewes. Therefore, the further researches into the determined phenomena in the Romanov sheep are required to improve this item, since the multi-fetal pregnancy is recorded in some ewes of group WW.

Seasonality in Saint Croix male lamb reproductive development in northern Mexico.

The aim of this study was to determine the influence of the season of birth on the body weight, testicular size, testosterone concentrations, semen output and sexual behaviour in Saint Croix male lambs. Thirty-three lambs were born in spring (n=10), summer (Sum; n=12) or autumn (n=11). Body weight and the scrotal circumference were weekly recorded; semen was also weekly collected by electroejaculation; and sexual behaviour towards oestrous ewes was weekly evaluated. Data were recorded from 15 to 33weeks of age. The reproductive development of Saint Croix male lambs differed according to the period in which they were born. More lambs born in spring than in summer and autumn achieved puberty during this study and were also more precocious in semen production and displayed sexual behaviour earlier. Lambs born in summer delayed their semen production; however, season-related negative effects were less pronounced at the end of the study than in autumn born lambs born. In conclusion, despite the apparently low seasonality of the breed, Saint Croix male lambs showed in this study a seasonal pattern in their reproductive development at least until they achieve the puberty.

Ventilation Prior to Umbilical Cord Clamping Improves Cardiovascular Stability and Oxygenation in Preterm Lambs After Exposure to Intrauterine Inflammation.

Background: Delaying umbilical cord clamping until after aeration of the lung (physiological-based cord clamping; PBCC) maintains cardiac output and oxygenation in preterm lambs at birth, however, its efficacy after intrauterine inflammation is not known. Given the high incidence of chorioamnionitis in preterm infants, we investigated whether PBCC conferred any benefits compared to immediate cord clamping (ICC) in preterm lambs exposed antenatally to 7 days of intrauterine inflammation.Methods: Ultrasound guided intraamniotic injection of 20 mg Lipopolysaccharide (from E. coli:055:B5) was administered to pregnant ewes at 0.8 gestation. Seven days later, ewes were anesthetized, preterm fetuses exteriorised via cesarean section, and instrumented for continuous measurement of pulmonary, systemic and cerebral pressures and flows, and systemic, and cerebral oxygenation. Lambs were then randomized to either PBCC, whereupon ventilation was initiated and maintained for 3 min prior to umbilical cord clamping, or ICC where the umbilical cord was cut and ventilation initiated 30 s later. Ventilation was maintained for 30 min.Results: ICC caused a rapid fall in systemic (by 25%) and cerebral (by 11%) oxygen saturation in ICC lambs, concurrent with a rapid increase in carotid arterial pressure and heart rate. The overshoot in carotid arterial pressure was sustained in ICC lambs for the first 20 min of the study. PBCC maintained cardiac output and prevented the fall in cerebral oxygen delivery at birth. PBCC lambs had lower respiratory compliance and higher respiratory requirements throughout the study.Conclusion: PBCC mitigated the adverse effects of ICC on oxygenation and cardiac output, and therefore could be more beneficial in preterm babies exposed to antenatal inflammation as it maintains cardiac output and oxygen delivery. The increased respiratory requirements require further investigation in this sub-group of preterm infants.

English

Stagnant early growth and poor lamb survival are the major constraints of sheep production in Ethiopia. The aim of this study was to evaluate early growth and survival rate of crossbred lambs (Dorper &times; indigenous, Adilo) under semi-intensive conditions. Body weight (BW, kilograms) at 0-180 days, average daily gain (ADG, g/day), pre- (0-90), post (90-180) and overall (0-180 days), and pre-weaning survival rate (PSR) of crossbred (50%) lambs (n=305) were evaluated. The non-genetic factors (season, parity, sex of lambs, litter size) were also determined. The least squares means (&plusmn;SE) of BW at birth, 30, 60, 90, 120, 150 and 180 days of age were 2.6&plusmn; 0.63, 5.6&plusmn; 0.12, 8.7&plusmn; 0.18, 11.6&plusmn;0.23, 15.0&plusmn;0.46, 17.2&plusmn; 0.31, and 18.4&plusmn;0.26 kg, respectively. The crosses were higher by 11.9% and 9.3% at 90 and 150 days, respectively, than indigenous Adilo lambs. There was clearly evident effect of season on body weights at various ages, pre- and post-weaning and overall ADG. Parity influenced weight at 30, 60, and 90 days, and ADG (pre, post and overall). The litter size (1.68 &plusmn; 0.6) consistently affected BW at all ages, pre-weaning and overall ADG. Weight at birth, 30 and 90 days, and ADG from 30-60, 60-90 and 120-150 days were affected by parity-by-litter size interaction. The PSR rate (90.2%) was influenced by all non-genetic factors except sex. The improvement in litter size, body weight, and survival represents potentially significant economic advantage of crossbred over local sheep. Managing dam age through replacement ewes, and improving nutrition and litter size would improve lamb survival and growth that enhances total lamb output per ewe per year. &nbsp; Key words: Growth rate, market weight, crossbred lamb, fixed factors.

Developing farm-specific marginal abatement cost curves: Cost-effective greenhouse gas mitigation opportunities in sheep farming systems

Growing demand for agricultural produce, coupled with ambitious targets for greenhouse gas emissions reduction present the scientific, policy and agricultural sectors with a substantial mitigation challenge. Identification and implementation of suitable mitigation measures is driven by both the measures’ effectiveness and cost of implementation. Marginal abatement cost curves (MACCs) provide a simple graphical representation of the abatement potential and cost-effectiveness of mitigation measures to aid policy decision-making. Accounting for heterogeneity in farm conditions and subsequent abatement potentials in mitigation policy is problematic, and may be aided by the development of tailored MACCs. Robust MACC development is currently lacking for mitigation measures appropriate to sheep systems. This study constructed farm-specific MACCs for a lowland, upland and hill sheep farm in the UK. The stand-alone mitigation potential of six measures was modelled, against real farm baselines, according to assumed impacts on emissions and productivity. The MACCs revealed the potential for negative cost emissions’ abatement in the sheep industry. Improving ewe nutrition to increase lamb survival offered considerable abatement potential at a negative cost to the farmers across all farms while, lambing as yearlings offered negative cost abatement potential on lowland and upland farms. The results broadly advocate maximising lamb output from existing inputs on all farm categories, and highlight the importance of productivity and efficiency as influential drivers of emissions abatement in the sector. The abatement potentials and marginal costs of other measures (e.g. reducing mineral fertiliser use and selecting pasture plants bred to minimise dietary nitrogen losses) varied between farms, and this heterogeneity was more frequently attributable to differences in individual farm management than land classification. This has important implications for the high level policy sector as no two farms are likely to benefit from a generic one size fits all approach to mitigation. The construction of further case-study farm MACCs under varying farm conditions is required to define the biophysical and management conditions that each measure is most suited to, generating a more tailored set of sector-specific mitigation parameters.

Short communication. Effect of concentrate supplementation and prolificacy on the productive and economic performance of autochthonous sheep breeds fed forage-based diets

Sheep farming systems in Spain are experiencing an intensification process, characterised by a general selection criteria of enhancing prolificacy in ewes, and by increasing indoor feeding with concentrates to the detriment of grazing. This study evaluated the effects of concentrate supplementation and prolificacy on productive and economic performance of a local sheep breed in different price scenarios. Ewes were fed forage hay ad libitum, without (in pre-partum period, PRE-HAY; and in post-partum period, POST-HAY) or with concentrates (300 g/d in pre-partum period, PRE-CON; and 750 g/d in post-partum period, POST-CON). The inclusion of concentrate during the pre-partum period (last 10 weeks of pregnancy) had no effect on the productive performance of the ewes. In contrast, the inclusion of concentrate in the post-partum period (6 weeks), resulted in greater milk yield (1009 vs. 1275 ± 89 g/d), lamb average daily gain (151±12 vs. 225±19 g/d) and lamb output (kg of lamb LW weaned). However, the greater productivity thanks to the use of concentrates did not always turn into greatest profitability, since the economic margin was highly influenced by the cost of the diet and extremely subjected to variability in price of concentrates. Hence, the inclusion of concentrates in sheep meat production was not always justified in economic terms. In conclusion, the use of concentrates should only be considered as long as prices of commodities remain low, and inadvisable when prices reach a certain threshold or are subject to certain volatility in markets.

Effects of replacing grass silage with either maize silage or concentrates during late pregnancy on the performance of breeding ewes fed isonitrogenous diets

A study was undertaken to investigate the performance of breeding ewes fed a range of forage and concentrate-based diets in late pregnancy, balanced for supply of metabolizable protein (MP). For the final 6 weeks before lambing, 104 twin-bearing multiparous ewes were offered one of four diets: ad libitum precision-chop grass silage + 0.55 kg/day concentrates (GS); ad libitum maize silage + 0.55 kg/day concentrates (MS); a 1 : 1 mixture (on a dry matter (DM) basis) of grass silage and maize silage fed ad libitum + 0.55 kg/day (GSMS); or 1.55 kg/day concentrates + 50 g/day chopped barley straw (C). The CP content of the concentrates was varied between treatments (157 to 296 g/kg DM) with the aim of achieving a daily intake of 130 g/day MP across all treatments. Compared with ewes fed GS, forage DM intake was higher (P < 0.05) in ewes fed MS (+0.21 kg/day) and GSMS (+0.16 kg/day), resulting in higher (P < 0.001) total DM intakes with these treatments. C ewes had the lowest total DM intake of all the treatments examined (P < 0.001). C ewes lost more live weight (LW; P < 0.001) and body condition score (BCS; P < 0.05) during the first 3 weeks of the study but there were no dietary effects on ewe LW or BCS thereafter. The incidence of dystocia was lower (P < 0.01) in C ewes compared with those offered silage-based diets (7.5% v. 37.4% ewes), and was higher (P < 0.01) in ewes fed MS compared with GS or GSMS (50.7%, 34.7% and 26.9%, respectively). There were no significant dietary effects on the plasma metabolite concentrations of ewes in late pregnancy, pre-weaning lamb mortality, weaned lamb output per ewe or on lamb growth rate. The results of this study demonstrate that both maize silage and all-concentrate diets can replace grass silage in pregnant ewe rations without impacting on performance, provided the supply of MP is non-limiting. The higher incidence of dystocia in ewes fed maize silage as the sole forage is a concern.

Effects of breed and age on the performance of crossbred hill ewes sourced from Scottish Blackface dams

The aim of this study was to evaluate the effects of age and breed on the reproductive performance and lamb output of crossbred hill ewes relative to purebred Scottish Blackface (BF). BF ewes were compared alongside Swaledale (SW) × BF, North Country Cheviot (CH) × BF, Lleyn (LL) × BF and Texel (T) × BF ewes on six commercial hill farms across Northern Ireland, on which all the ewes were born and reared. Ewes were mated to a range of sire breeds, balanced across breeds, for up to five successive breeding seasons. Mature live weight of adult BF, SW × BF, CH × BF, LL × BF and T × BF ewes was 52.8, 54.9, 60.3, 55.6 and 58.6 kg (P < 0.001), respectively. Compared with the pure BF, the number of lambs born per ewe lambed was higher with LL × BF and SW × BF (P < 0.05), whereas the number of lambs weaned per ewe lambed was greater for LL × BF and T × BF (P < 0.01). Total litter weight at birth of all the crossbred ewes was heavier (P < 0.01) than the pure BF, except in primiparous 2-year-old ewes. Lambs born to CH × BF and T × BF dams were 0.24 to 0.35 kg heavier at birth (P < 0.01) than the other ewe breeds, whereas lambs born to CH × BF, LL × BF and T × BF dams were, on average, 1.7, 1.3 and 1.5 kg, respectively, heavier (P < 0.01) at weaning than those from BF dams due to their higher (P < 0.05) average daily gain. Compared with the pure BF, total weaned lamb output per ewe lambed was 3.7, 4.8, 6.7 and 5.4 kg heavier (P < 0.05) for SW × BF, CH × BF, LL × BF and T × BF, respectively. However, as a result of the heavier live weight of the crossbred ewes, production efficiency (lamb output per kilogram live weight (W) and lamb output per kilogram metabolic live weight (W0.75)) was higher (P < 0.001) for LL × BF ewes only. For all ewe breeds, litter size at birth per ewe lambed, total lamb birth weight per ewe lambed and litter size at weaning increased (P < 0.001) with age up to 5 years, but decreased in 6-year-old ewes. Average lamb weaning weight and total weaned lamb output per ewe lambed increased (P < 0.001) with age up to 4 years. Production efficiency of the 6-year-old ewes was lower (P < 0.01) than the younger ewes. This study shows that adopting a flock replacement policy based on crossing BF ewes with LL, SW, T and CH sires can lead to significant improvements in the productivity of hill flocks.

Comparison of the longevity and lifetime performance of Scottish Blackface ewes and their crosses within hill sheep flocks

A study was undertaken to compare the longevity and lifetime lamb output of purebred Scottish Blackface (BF) ewes with a range of crossbred genotypes from Scottish BF dams. For up to five successive breeding seasons, 1143 Scottish BF, Swaledale × BF (SW × BF), North Country Cheviot × BF (CH × BF), Lleyn × BF (LL × BF) and Texel × BF (T × BF) ewes were mated to a range of sire breeds on six hill farms across Northern Ireland. Dentition and lamb output were recorded annually until completion of the study or until the ewe was removed due to death or culling. Timing of mortality and the main reason for culling were also recorded. When survival analysis was undertaken, SW × BF and CH × BF ewes had better longevity (P < 0.05) than BF ewes due to their lower culling rate (P < 0.01) and lower mortality rate (P = 0.06), respectively. The relative proportion of LL × BF and T × BF culled due to infertility was lower (P < 0.05) than SW × BF and CH × BF, while a higher (P < 0.05) proportion of LL × BF and T × BF ewes were culled for prolapses compared with the other breed crosses. SW × BF ewes had consistently higher bite scores (P < 0.001) compared with BF, LL × BF and T × BF, indicating a greater prevalence and degree of overshoot. In ewes aged 5.5 years old, SW × BF also had a higher incidence of tooth loss (P < 0.01) compared with the other breeds. However, the proportion of SW × BF culled due to poor teeth condition was lower (P < 0.05) than BF. Across all breeds, the chances of surviving to their next mating were influenced by ewe breed (P < 0.05), age at mating (P < 0.001), body condition score at weaning (P < 0.001), number of missing teeth (P < 0.001) and average daily live weight gain per litter (P < 0.05). The cumulative number and weight of lambs weaned per ewe over five successive matings was higher (P < 0.05) for crossbred compared with pure BF ewes; however there were no differences in lifetime output between the different crossbred ewes studied. This study demonstrates that the higher lamb output of crossbred hill ewes does not compromise their longevity compared with pure Blackface, resulting in greater total lifetime production. When the crossbred ewes are sired by a second hill breed, longevity may be improved.

Effects of supplementation with digestible undegradable protein in late pregnancy on ewe colostrums production and lamb output to weaning

The aim of this study was to investigate the effects of supplementation with digestible undegradable protein (DUP) in diet during late pregnancy on colostrum production, lamb survival and growth. For 3 weeks prior to lambing, 41 Afshari ewes were assigned at random to three dietary treatments, namely a control (CDUP), moderate (MDUP) and high (HDUP) DUP group. The ewes (n = 14) in CDUP group were fed a protein maintenance level for pregnant ewes [83 g metabolizable protein (MP)/kg dry matter (DM)], while ewes in the MDUP (n = 13) and HDUP (n = 14) groups were fed diets provided 14% (94.7 g MP/kg DM) and 24% (104.3 g MP/kg DM) MP in excess of these requirements respectively, which this increment was coming from DUP (DUP/MP ratio 43.8; 51.0% and 57.6% respectively). All diets were isoenergetic (12 MJ ME/kg DM). All ewes received the same lactation diet after lambing. Ewes in HDUP tend to produce more colostrums (p < 0.1) and had higher protein, fat, and solids non-fat content (p < 0.05) in colostrums during the first 24 h after lambing. MDUP group had higher colostrum yield compared to CDUP (p < 0.1). The changes in body weight and body condition score of ewes were similar for all diets but placenta weight was higher in MDUP group (p < 0.05) than for HDUP and CDUP ewes. Lamb body weight at weaning was higher for males compared to females (p < 0.05), but was not different between treatments. HDUP ewes had higher blood glucose concentration in the pre-lambing period than other treatments (p < 0.05). In this period, increasing the level of DUP in diet increased the content of blood urea nitrogen (p < 0.05). It was concluded that increasing the DUP content of diet for 3 weeks prior to lambing above the standard requirements resulted in an increase in colostrums production but had no effect on lamb outcome to weaning.

Effects of sire breed on ewe dystocia, lamb survival and weaned lamb output in hill sheep systems

A study was carried out on six hill farms, located in the main hill regions of Northern Ireland, over three breeding seasons to investigate the effect of sire breed on ewe dystocia, lamb survival and weaned lamb output. On each farm, groups of 26 to 40 purebred Scottish Blackface ewes (n = 3174) were crossed with Blackface, Swaledale, North Country Cheviot, Lleyn and Texel sires by natural service (year 1) and artificial insemination (years 2 and 3). Each of the mating groups was initially balanced for ewe age, live weight and condition score, and a total of 15 sires of each breed were used over the 3 years. In total, 2272 ewes were recorded at lambing, producing 3451 lambs, over the 3 years. Sire breed had a significant effect (P < 0.001) on lamb birth weight with Blackface and Swaledale the lowest and Texel the highest. The proportion of ewes with dystocia was higher with Texel sires compared with Lleyn, Swaledale and Blackface sires (P < 0.05). Ewes mated to Cheviot sires had more dystocia than those mated to Blackface and Swaledale sires (P < 0.05), while ewes mated to Lleyn sire breed had more dystocia (P < 0.05) than those mated to Blackface sire breed. Most of the incidence of dystocia was attributable to increased lamb birth weight (P < 0.001), and some to litter size (P < 0.05). Swaledale, Cheviot, Lleyn and Texel sire breeds increased the incidence of malpresentations (P < 0.05). Lamb live weight at weaning was higher with Texel- and Cheviot- and Lleyn-sired lambs compared with Blackface- and Swaledale-sired lambs (P < 0.01). The level of lamb mortality at birth was not affected by sire breed. However, lamb mortality at weaning was lower for Lleyn-sired lambs compared with the other lamb genotypes (P < 0.05). These results indicate that the use of sires from larger breeds, such as Lleyn and Texel, within the Blackface ewe flocks can increase lamb output, with no apparent detrimental effects on lamb mortality or ewe survival, but increased assistance at lambing will be required.

Effects of source and level of fish oil supplementation in late pregnancy on feed intake, colostrum production and lamb output of ewes

Supplementing pregnant ewes with fish oil to enhance the dietary supply of 20:4 n-6 and 22:6 n-3 has the potential to improve neonatal vigour and increase lamb survival rates. However, dietary fish oil has been shown to reduce colostrum production of ewes which can adversely affect lamb survival. To investigate the effects of source and level of fish oil in this response, 55 twin-bearing ewes were offered grass silage (0.5 kg dry matter per day) plus concentrates (0.5 kg/d) and supplemented with 0, 20 or 40 g/d herring (H) or salmon oil (S) during the final 6 weeks of pregnancy, giving a total of 5 treatments being control, H20, H40, S20 and S40. Salmon oil increased the supply of 18:2 n-6 (2.37) and 22:4 n-6 (1.98) but reduced the supply of 22:6 n-3 (0.84) relative to herring oil. Silage DM intake was marginally lower for S40 ewes ( P<0.05) but there were no dietary effects on ewe live weight or body condition score. Plasma non-esterified fatty acids (NEFA) ( P<0.05) and urea ( P<0.001) concentrations were elevated in ewes fed fish oil. Lambs born to control ewes had higher serum IgG concentrations than those fed herring oil ( P<0.01). Colostrum output at 10 h ( P<0.01) and total yield of colostrum ( P<0.05) were lower for fish oil-supplemented ewes. Concentrations of 10 h IgG ( P<0.05), 18 h fat ( P<0.001), 18 h total solids ( P<0.05) as well as outputs of fat ( P<0.05), protein ( P<0.01), casein ( P<0.05), IgG ( P<0.001) and total solids ( P<0.05) were reduced by feeding fish oil. Compared with controls, ewes fed herring oil had a higher 10 h lactose concentration ( P<0.05) while those fed salmon oil had lower outputs of 18 h protein ( P<0.05) and 18 h casein ( P<0.05). Offering 20 g/d, but not 40 g/d, fish oil increased the number of lambs weaned (+0.55 lambs/ewe; P=0.06) and the total output of weaned lamb (19.4 kg; P<0.05), but otherwise there were no effects of fish oil level and source on ewe or lamb performance. Results indicate that low levels of crude fish oil supplementation (up to 20 g/d) during late pregnancy improved lamb survival and output at weaning, but these benefits disappeared at higher inclusion rates.

Effects of replacing grass silage with maize silage or concentrates on lamb output from housed pregnant ewes

Rations for pregnant ewes in the UK are often based on grass silage. However, due to a number of factors, the cost of producing high quality grass silage has increased significantly in recent years so lower cost alternatives need to be investigated. Production of forage maize has the potential to reduce forage costs on mixed beef/sheep farms, with high dry-matter yields (comparable to that of a 3-cut silage system) of high quality maize silage possible from a single harvesting operation (Easson and Fearnehough, 2000). However there is limited information on the effects of feeding maize silage to pregnant ewes. Alternatively, grass silage could be eliminated from rations by feeding high grain diets. The aims of this study were to evaluate the effects of replacing grass silage with either maize silage or concentrates on the performance of housed pregnant ewes and their lambs.

Lifetime performance of crossbred ewes in the hill sheep sector

Hill sheep flocks in the UK are dominated by purebred ewe genotypes, with the Scottish Blackface being the most common. However a long term decline in economic returns, combined with recent changes to the Common Agricultural Policy, has lead many hill sheep producers to consider keeping crossbred ewes to exploit the benefits of hybrid vigour for lamb survival and to introduce beneficial traits for prolificacy, ease of lambing and carcass quality. In 2001, a major on-farm research programme was initiated to evaluate the performance of a range of crossbred ewe genotypes for the Northern Ireland hill sheep sector. Provisional data has already identified that retaining Lleyn X Blackface and Texel X Blackface ewes can improve lamb output at weaning by up to 10% relative to purebred Blackface ewes (Speijerset al., 2007). However, ewe longevity is a major issue for hill flocks, where the annual replacement rate often exceeds 20%. Therefore it is inappropriate to evaluate crossbred ewe genotypes based on average annual performance alone, and the aims of this study were to investigate the lifetime performance of a range of crossbred genotypes under hill conditions.

The effect of genotype and diet on lamb meat quality from hill sheep systems

Crossbreeding can be used in the hill sector to improve the efficiency of production. Carsonet al. (2001) showed that ram breed substitution increased lamb output per ewe by 24% with concomitant improvements in carcass quality. However, information is required for a range of crossing sire breeds for the hill sector to enable the most effective crossbreeding programmes to be developed. Therefore, the primary aim of this study was to evaluate the effects of a range of lamb genotypes on lamb meat quality. Furthermore, a range of production systems (long-keep grass-based systems to short-keep concentrate-based systems) are used to finish hill lambs. Diet type (i.e. roughage-versus concentrate-based) can also affect lamb growth rates and carcass characteristics (Carsonet al., 2001). Consequently, a secondary aim of this study was to evaluate the effects of diet and its interaction with lamb genotype on lamb meat quality.

Analysis of PrP genotypes in relation to reproductive and production traits in Chios sheep

The study describes the changes with time in gene and genotype frequencies of a closed Chios herd. Genomic DNA was isolated and purified from peripheral blood leucocytes using standard procedures. The identification of the allelic variants present in the DNA samples, was performed in a simple multiplex PCR reaction and melting curve analysis of the PrP gene. Only ARR/ARR female genotypes were kept for breeding, and only males of the same genotype were used following year 2 of the study. As a result of planned individual matings and selection, the susceptible ARQ/ARQ genotype was eliminated from the flock in 4 years. The gene frequency of the R allele from a low 0.056 at year 1 reached a high 0.911 at year 6 of the study. Data from first lactation ewes of known genotypes were used to examine possible associations between PrP genotypes and ewe reproductive (litter size at birth and at weaning) and production traits (litter weight at birth and at weaning and 60-day milk yield after weaning). No effects of the sire genotype (ARR/ARR and ARR/ARQ) were found for any of the traits studied. The ewe genotype was associated with performance for reproductive traits but not with total weight of lamb output at birth or at weaning. ARR/ARR ewes had a higher litter size at birth (2.09) compared to ARQ/ARQ ewes (1.79) and higher litter size at weaning (1.84) compared to ARR/ARQ ewes (1.59). 60-day milk yield after weaning was not influenced by genotype (114.8, 105.8 and 114.8 kg for ARR/ARR, ARR/ARQ and ARQ/ARQ genotypes, respectively). Birth weight and 98-day weight were not influenced by the lamb genotype. ARQ/ARQ lambs were slightly heavier ( P < 0.05) than ARR/ARR lambs at weaning as a result of faster pre-weaning growth. Post weaning growth was similar for the homozygous genotypes.