The effect of hCG treatment on Day 12 post-mating on ovarian function and reproductive performance of ewes and ewe lambs

The objectives of this study were to determine the effect of a single intramuscular injection of 200 IU hCG (Chorulon) on Day 12 post-mating on ovarian function and subsequent lambing performance in ewes and ewe lambs bred at synchronised oestrus during the breeding season and on the lambing performance of ewes induced to breed during late anoestrus. All animals were mated to rams at synchronised oestrus and on Day 12 post-mating given normal saline or 200 IU hCG.In Experiment 1, laparoscopic results showed that hCG treatment induced accessory corpora lutea in ewes (control = 0/7; hCG = 5/7) but not in ewe lambs (control = 0/7; hCG = 0/7).In Experiment 2, hCG treatment did not improve the lambing rate (control = 50; hCG = 57) or the litter size (control = 1.80; hCG = 1.96) in ewes (control = 100; hCG = 91). However, hCG treatment significantly (P > 0.05) improved the lambing rate (control = 29; hCG = 58; P < 0.05) in ewes conceiving at the first oestrus after treatment. hCG treatment (control = 42; hCG = 42) also failed to improve the lambing rate in ewe lambs (control = 48; hCG = 41).In Experiment 3, hCG treatment had no significant (P > 0.05) effect on the lambing rate (control = 72; hCG = 62) or the litter size (control = 1.59; hCG = 1.58) in ewes (control = 111; hCG = 115) induced to breed during anoestrus or on ewes returning to oestrus and conceiving after treatment (lambing rate: control = 86; hCG = 72; litter size: control = 1.44; hCG = 1.35). In conclusion, the data obtained in this study suggest that during the breeding season hCG may, by stimulating ovarian function, improve embryo survival in ewes conceiving at the first post-treatment oestrus. This effect, however was not observed in ewe lambs.     

Effects of shearing at housing, grass silage feed value and extended grazing herbage allowance on ewe and subsequent lamb performance

The study involved 120 crossbred ewes (sixty 1.5 years old animals and sixty 2.5 years old animals; initial liveweight 67.6 kg, condition score 3.7), that were mated in October. They were assigned to six treatments (two shearing treatments (shorn and unshorn) × two silage feed values (low and medium) and two extended grazed herbage allowances (1.0 and 1.8 kg dry matter (DM)/day)) designed to evaluate the effects of shearing at housing, grass silage feed value and extended-grazed herbage allowance on their performance and the performance of their progeny. Swards, which had silage harvested on 6 September, received fertiliser N (34 kg/ha) for extended (deferred) grazing between 19 December and lambing in mid-March. The herbage was allocated at DM allowances of 1.0 or 1.8 kg/ewe daily until 1 February. For the final 6 weeks of pregnancy, daily herbage DM allowances were 1.5, 1.6, 2.0, 2.0 and 2.0 kg for weeks 6, 5, 4, 3 and 2 to parturition, respectively. Two grass silages (low and medium feed value) were offered from housing on 19 December to lambing in mid-March. At housing, half the ewes were shorn whilst the remainder remained unshorn. Each ewe received 23.4 kg concentrate prior to lambing. For the extended-grazed herbage and the low and medium feed-value silages, DM concentrations were 132, 225 and 265 g/kg, and metabolisable energy (ME) concentrations were 10.0, 10.0 and 10.7 MJ/kg DM, respectively. Treatment did not alter (P > 0.05) litter size or number reared. Grass silage feed value did not significantly alter silage DM intake, or ewe and subsequent lamb performance. Increasing herbage allowance in mid-pregnancy decreased herbage utilisation (P < 0.05) and increased herbage intake (P < 0.05). Shearing increased silage intake (P < 0.05), lamb birth weight (P < 0.01) and tended to increase lamb weaning weight (P = 0.07). Relative to the housed shorn ewes, extended grazing did not alter (P > 0.05) ewe or subsequent lamb performance. It is concluded that shearing ewes at housing increased lamb birth weight due to increased silage intake probably associated with cold stress immediately post shearing and reduced heat stress in late pregnancy. Based on differences in lamb weight at weaning 0.8 kg of grass silage DM intake had the same feed value as a daily extended herbage DM allowance of 1.8 kg per ewe throughout the study. Neither silage feed value nor herbage allowance in mid-pregnancy affected lamb birth weight or subsequent growth rate.     

Gastro-intestinal nematode parasite populations in ewes and lambs and the origin and time course of infective larval availability in pastures

Changes in the numbers of infective larvae available on pasture and the development of helminth infection in spring-born lambs were studied in an environment with a mild winter and where pastures are grazed throughout the year. Prior contamination of pastures in autumn and early winter was compared with egg deposition by lambing ewes as sources of infection. Larvae derived from eggs deposited by lambing ewes did not appear on pasture until 8 weeks after the beginning of lambing but were present in increasing numbers for the last 7 weeks before weaning at 11–15 weeks of age. Lambs exposed to prior contamination became infected earlier than those exposed only to ewe contamination, but lamb egg output made no contribution to larval numbers on pasture before weaning. Lamb growth rates to weaning did not differ between groups exposed either to prior contamination alone, to ewe egg output alone or to both, but all groups carried appreciable infections at weaning. After weaning, lambs remained on the same pastures, and those exposed to ewe contamination suffered severe trichostrongylosis 5 weeks after weaning. Lambs exposed only to over-wintered contamination also developed severe trichostrongylosis 9 weeks after weaning. The results are compared with those of similar recent studies in Britain and their implications for control of infection are discussed.     

Nutritional status of adult ewes during early and mid-pregnancy. 1. Effects of plane of nutrition on ewe reproduction and offspring performance to weaning

The objective of this study was to determine the effects of plane of nutrition during early and mid-pregnancy on the performance of mature ewes and their offspring. From day 0 to day 39 post mating (early pregnancy, EP), 82 multiparous ewes were fed to provide either 60% (low, L), 100% (medium, M) or 200% (high, H) of predicted metabolisable energy (ME) requirements for maintenance, following a synchronised mating. From day 40 to day 90 (mid-pregnancy, MP), ewes were provided with either 80% (M) or 140% (H) of ME requirements. After 90 days of gestation, all ewes were fed to meet requirements for late pregnancy. During EP, mean live weight (LW) and body condition score (BCS) change of ewes were -6.3, -0.8 and +6.0 kg and -0.02, +0.10 and +0.22 units in the L-, M- and H-EP treatments, respectively. During MP, mean LW and BCS change were -0.8 and +4.9 kg and -0.09 and +0.09 units in the M- and H-MP treatments, respectively (P < 0.001). Treatments had no effect (P > 0.05) on conception rate, although there tended to be an inverse relationship (P = 0.085) between plane of nutrition in EP and plasma progesterone concentrations at day 42 of gestation. EP nutrition influenced foetal development with lambs from ewes offered diet L-EP being smaller (P < 0.01) at day 56 than M- or H-EP lambs. However, at parturition L-EP lambs were heavier (P < 0.05) and tended to have higher (P = 0.056) immunoglobulin status 24 h after birth. Mortality rates at weaning were reduced (P < 0.05) for lambs born from ewes offered diet L-EP compared with M- or H-EP lambs. Diet M during mid-pregnancy resulted in larger (P < 0.05) foetuses at day 80 of gestation. At parturition, these lambs had longer head and crown-rump lengths than H-MP lambs (P < 0.05). Lambs born to ewes offered diet M-MP tended to progress faster to attempting to suckle than H-MP lambs (P = 0.089). There was an interaction between plane of nutrition in early and mid-pregnancy, whereby the highest number of lambs weaned was a result of diet L-EP followed by diet M-MP. These results indicate that in adult ewes, temporary nutrient restriction during early pregnancy results in better lamb survival; and mild nutrient restriction in mid-pregnancy tends to improve neonatal behaviour and results in lambs with longer skeletal size.     

Volatiles in raw and cooked meat from lambs fed olive cake and linseed

This study was conducted to determine the effects of feeding olive cake and linseed to lambs on the volatile organic compounds (VOCs) in raw and cooked meat. Four groups of eight male Appenninica lambs each were fed: conventional cereal-based concentrates (diet C), concentrates containing 20% on a dry matter (DM) basis of rolled linseed (diet L), concentrates containing 35% DM of stoned olive cake (diet OC), or concentrates containing both rolled linseed (10% DM) and stoned olive cake (17% DM; diet OCL). The longissimus dorsi muscle of each lamb was sampled at slaughter and was subjected to VOC profiling through the use of SPME-GC-MS. In the raw meat, the concentration of 3-methylpentanoic acid was higher in treatment C as compared with treatments L, OC and OCL (P<0.01). Moreover the level of nonanoic acid was greater in treatments C and OC than in treatment L (P<0.05). With respect to alcohols, in raw meat the amount of 2-phenoxyethanol in treatment OCL was lower than in treatments C (P<0.01) and OC (P<0.05), while in cooked meat the amount of 1-pentanol was higher in treatment C than in treatment OC (P<0.05). Apart from these compounds, none of the lipid oxidation-derived volatiles was significantly affected by the dietary treatment. Therefore, the results suggest that the replacement of cereal concentrates with linseed and/or olive cake did not cause appreciable changes in the production of volatile organic compounds in lamb meat.     

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.     

Influence of vitamin E supplementation and basal diet on the vitamin E status, performance and tissue fatty acid concentration in lambs

In order to determine the effect of dietary vitamin E level and basal diet on vitamin E status, performance and tissue fatty acid content, five groups of eight Suffolk × Charollais wether lambs with an initial live weight of 28.4 (s.d. 1.6) kg were allocated to one of five concentrate-based diets supplemented with all-rac-α-tocopheryl acetate to contain 30 mg (C-30), 60 mg (C-60), 120 mg (C-120), 250 mg (C-250) or 500 mg (C-500) α-tocopheryl acetate/kg dry matter (DM), for 63 days. Two additional groups of eight lambs entered the study at 31.2 (s.d. 3.3) kg and were fed grass silage and 400 g/day concentrate for 56 days, with the whole diet providing the equivalent of 60 mg (S-60) or 500 mg (S-500) α-tocopheryl acetate/kg DM. Lambs were weighed and blood samples obtained by venipuncture weekly. Dietary vitamin E level did not affect performance (P > 0.05), but lambs fed grass silage grew more slowly (P < 0.001) and had a higher (P < 0.001) feed conversion ratio (kg feed/kg gain) than those fed concentrates. At day 0 plasma α-tocopherol concentrations were 0.8 μg/ml and did not differ between treatments (P > 0.05). Plasma α-tocopherol concentrations then decreased in all lambs except for those fed S-500, which increased, and at slaughter were (μg/ml) 0.07, 0.23, 0.39, 0.76 and 1.57 in C-30, C-60, C-120, C-250 and C-500 and 1.18 and 1.93 in S-60 and S-500, respectively. At slaughter, muscle and liver α-tocopherol concentrations were in the deficiency range for lambs fed C-30, C-60 or C-120, whereas plasma creatine kinase and tissue polyunsaturated fatty acids were unaffected by dietary vitamin E level, but creatine kinase levels were higher (P < 0.05) and glutathione peroxidise levels lower (P < 0.001) in lambs fed grass silage than concentrates alone. Muscle and liver α-tocopherol concentrations were 1.8- and 4.1-fold higher in lambs fed S-60 than C-60, but there was less of a difference between lambs fed S-500 or C-500 with muscle and liver differences of 0.4- and 0.7-fold, respectively. Tissue n-3 polyunsaturated fatty acid concentrations were higher (P < 0.05) and n-6 fatty acids lower in lambs receiving the grass silage compared to concentrate-based diets, but were not affected by dietary vitamin E level. It is concluded that lower plasma and tissue levels of α-tocopherol are present in lambs supplemented with all-rac-α-tocopheryl acetate on a concentrate compared to a mixed diet of silage and concentrates, and that normal growth can be achieved at tissue levels previously considered to represent deficiency.     

The effect of late pregnancy supplementation of ewes with vitamin E on lamb vigour

The experiment measured lamb responses to supplementation of the pregnant ewe diet with vitamin E above requirement. Crossbred ewes were mated with either Suffolk or Texel rams. Twin-bearing ewes were randomly allocated (approximately 21 months of age at allocation) to one of four treatment groups (20 ewes per group, 10 mated with Suffolk and 10 with Texel rams). Treatments imposed were 50, 100, 150 or 250 IU supplementary vitamin E per ewe per day to give a four treatment by two sire-type factorial experimental design. Ewes were fed concentrates to meet energy requirements for stage of pregnancy and hay ad libitum. Diets were introduced approximately 6 weeks before lambing. Blood samples were obtained prior to introduction of diets, 17 days after introduction of diets and within 24 h of lambing from a subset of eight ewes per treatment (32 total). Colostrum samples were obtained from 10 ewes per treatment, 12 h after birth of the first lamb. All births were observed and a lamb vigour score was assigned to each lamb 5 min after birth. At 1 and 12 h after birth, rectal temperature, and at 12 h after birth, sex, crown-rump length and BW of each lamb were recorded. Mean ewe plasma α-tocopherol concentration prior to introduction of the diets was 1.5 μg/ml (s.e.m. 0.09) and did not differ between groups. There were positive linear (P < 0.001) effects of dietary vitamin E on plasma (17 days after introduction of diets) and colostrum (12 h after birth) α-tocopherol concentrations. Lamb vigour scores were superior (P < 0.001) for lambs sired by Texel rather than Suffolk rams but there were no differences as a result of vitamin E supplementation. Lamb mortality was low and unrelated to either sire or supplementary vitamin E. Lamb birth and weaning weights were also unaffected by vitamin E supplementation. Supplementing the ewe with vitamin E therefore had no effect on any lamb measurements.     

Effects of a quantitative trait locus for increased muscularity on carcass traits measured by subjective conformation and fat class scores and video image analysis in crossbred lambs

A quantitative trait locus (QTL) for increased loin muscularity (TM-QTL) has previously been identified in purebred Texel sheep. Crossbred lambs born out of Mule ewes mated to heterozygous Texel sires for the TM-QTL were evaluated for a range of carcass traits. Lambs were genotyped and classified as carriers (n = 62) of a single copy of the TM-QTL and non-carriers (n = 49). In this study, the effects of the TM-QTL on carcass attributes were investigated using subjective classification scores for conformation and fatness, and measurements from a video image analysis (VIA) system. In addition, refined prediction equations to estimate weights of primal joints (leg, chump, loin, breast and shoulder) were obtained by calibrating the VIA system against computer tomography (CT) measurements in the loin region. The new refined prediction models increased the accuracy of prediction of all primal cuts on an average of 16% compared to previously derived standard VIA prediction equations. The coefficient of determination (R2) of the VIA system to predict in vivo CT measurements ranged from 0.39 to 0.72 for measurements of Musculus longissimus lumborum (MLL) area, width and depth, lumbar spine length, loin muscle volume and loin muscularity index. Using VIA estimates of CT-measured loin muscle traits, a significant increase in depth (+2.7%) of the MLL was found to be associated with the TM-QTL. Conformation and fatness scores and the shape of the carcass measured as individual lengths, widths and areas by VIA were not significantly influenced by the TM-QTL. Primal meat yields estimated using both standard and refined VIA prediction equations were not significantly affected by the TM-QTL. However, carcass 'compactness' was found to have significantly increased in carrier lambs. The weight of the dissected MLL estimated using VIA information was greater (+2.6%) for carriers compared to non-carriers. To conclude, neither the current industry carcass evaluation system for conformation and fatness nor the standard VIA system is able to identify the effect of the TM-QTL in the loin region in the moment. However, the calibration of the VIA system against CT measurements resulted in improved VIA prediction equations for primal meat yields and also showed moderate potential to estimate loin muscle traits measured by CT and to detect, partially, the effect of the TM-QTL on these traits.