Lamb Crop Research Articles

397 Field Demonstration Analyzing the Implementation of Individual Animal Electronic Identification and Genetic Testing in Western Range Sheep Flocks

Abstract The lack of individual performance records derived from an extensively driven production system coupled with impracticality to utilize reproductive technologies makes commercial genetic improvement challenging in small ruminants. We collaborated with five producers throughout California to assess how Electronic ID (EID) and a genotyping panel can augment the productivity of a flock. We sought to study how the data collected from these technologies can hasten genetic improvement towards desirable operational objectives. Familiarity and use of EID tags on ranches at the start of the research varied; thus, allowing for a qualitative reflection on the perceptions of the participants of the usefulness of this technology. We partnered with Superior Farms, a slaughterhouse, to evaluate their targeted genotyping panel, Flock54. Flock54 is a single nucleotide polymorphism (SNP) panel containing 956 markers for assigning pedigree and includes markers linked to quantitative trait loci and/or known single gene causative markers to aid in disease management and fecundity scoring. Ear notch samples were collected from 2,963 animals for analysis. This included 305 total sires as well as their progeny, 989 female lambs and 1,669 male lambs, which were marketed. Nine lambs were positive at a fecundity marker. No other notable results were found from the Flock54 panel. Genomic data was used to ascertain prolific sires on every ranch; however, ram to ewe ratio altered the influence that a prolific sire had on a lamb crop. The lowest ram to ewe ratio was 1:10. Parentage results from this ranch reports the following progeny metrics: Average: 9.9 males (±12.5); Median: 4 males; Max: 61 males, minimum 1 male. In contrast, the greatest ram to ewe ratio was 1:50. Parentage results from this ranch reports the following progeny metrics: Average: 51.9 (± 41.7); Median: 43.5; Max: 135; Minimum: 4,524 carcass samples from terminal lambs at two ranches were processed at Superior Farms` plant and assessed with a USDA inspected camera grading system. Progeny contemporary group deviations were calculated for hot carcass weight, yield grade, ovine cutability calculation (OCC), and OCC yield. After coupling carcass metrics with USDA reported prices, we identified prolific sires within the flock that garnered significantly higher and lower dollar merit at slaughter. A two-tailed Student`s T-test was used on the dollar deviation of edible product sold to identify if there was a statistically significant difference (P-value < 0.05) between a given ram`s progeny and the rest of the progeny slaughtered. We found that twenty-three out of the forty-three rams with progeny from one ranch had a statistically significant dollar deviation difference with a T-value greater than 2.0167. For the other ranch, we found that nineteen out of the thirty-five rams with progeny had a statistically significant difference with a T-value greater than 2.0301.

36 Beyond Environmentally Adapted, Towards Ecologically Purposed: Sheep Production in the Us West

Abstract Consumer demand for sheep products is robust, the annual consumption of U.S. lamb is steadily rising, and the number of U.S. sheep farms is increasing. Nevertheless, the U.S. sheep industry continues to lose market share to foreign competitors and the breeding ewe inventory has declined 30% since 2002. This decline has been more drastic in the upper U.S. Mountain West states, where ewe inventories have declined 37% compared with the national average decline of 26%. This is problematic given the Mountain West generates one-third and one-half of the total U.S. lamb crop and wool revenue, respectively. This depopulation trend indicates obstacles unique to the Mountain West, which are not experienced elsewhere in the nation. Mountain West sheep production systems depend on both private and public rangelands for grazing, which must co-exist with many other goals for public lands, including species conservation and critical wildlife habitat. Extensive conversion of native rangeland to croplands, rural housing, and degraded grasslands has simultaneously resulted in a substantial loss of wildlife habitat, thus creating competing ideologies for how remaining rangelands should be managed. Accordingly, public land management agencies are constantly pressured to change land management plans to accommodate public agendas aimed at restricting or halting livestock grazing on public lands with the assumption wildlife habitat will automatically improve. Such exclusion of grazing from public lands has negatively impacted operational capacity of sheep ranches, thus posing serious threats to the U.S. sheep industry and its contributions towards national food security, rural communities, and rangeland conservation. Therefore, to maintain grazing access to public lands, sheep producers and land managers urgently need tools (e.g., management, genetic) to optimize both conservation and production outcomes synergistically. However, ecological and sheep genetic outcomes have thus far been considered separate rather than integrated goals. Traditional genetic improvements in sheep production are focused strictly on the sheep without regard to the ecological outcome. In other words, the “ecosystem” is only considered to achieve profitable production within that environment. With this in mind, can sheep research move beyond the traditional focus of “environmentally adapted” flocks to “ecologically purposed” flocks? We propose that heritable ecologically focused traits can be identified and used to complement the overall sheep genetic improvement goals of the industry while creating precision-based solutions for sustainable habitat management, such as mitigating catastrophic wildfire risk, halting noxious weed invasion, and shaping vegetative structure of native plant communities towards desirable rangeland and conservation goals. We believe such outcomes extend beyond shaping public opinion about sheep grazing but also towards introducing novel value-based marketable products from the sheep industry.

Phenotypic Characterization and Reproductive Performance of Blackhead Somali Sheep in Fafen Zone of Somali Regional State, Ethiopia

Objective. The study aimed to characterize the reproductive performances and physical characteristics of Blackhead Somali indigenous sheep breeds. Methods. The data from 460 sheep were used for the determination of morphometric characterization while 110 male sheep and 150 females were used to characterize the reproductive performance of Blackhead Somali sheep breeds. Results. Accordingly, about 86% of sheep have a white body with a blackhead as the dominant coat color and about 81% of sheep have a straight facial head profile. Dewlap was present in 92.7% (91.8% for males and 92.7% for females). The overall average body weight, body length, height at wither, height at the rump, heart girth, chest depth, pelvic width, and tail circumference differs significantly (p<0.05) among males and females with the advancement of age. The average age at first service, age at first lambing, lambing interval, and life lamb crop in ewe were 13.75 ± 2.44, 19.12 ± 2.41, 9.66 ± 1.56, and 6.18 ± 2.01, respectively. The average reproductive life span of ewe and ram was 6.04 ± 1.43 and 6.63 ± 1.49 years, respectively. On average Blackhead Somali ewe delivers 13.1 ± 4.3 lambs in her lifetime. The twinning and triplet rate were recorded to be 12.30% and 1.90%, respectively. Conclusion. In conclusion, shorter lambing intervals, higher adult body weight, and frequent twinning are the most desirable features which may also be used as selection criteria. It is recommended to do further detailed analyses to determine the genetic variation between and within these small populations to develop an effective conservation and utilization program.

Impact of genetic selection and enhanced feeding on growth rate of Nilagiri and Sandyno sheep and their lambs

Weaned ewe lambs born during 2009-2014 were ranked according to their breeding value ascertained by BLUP analysis for weaning weight. Ten weaned ewe lambs each in Nilagiri and Sandyno breeds, on the top of the ranking were selected each year and placed as a separate elite group and were supplemented with increased level of concentrate feed from weaning with 8 h of routine grazing. Weight at 6, 9 and 12 months was recorded. Weight at birth, weaning, 6th and 12th months of lambs born to elite ewes were recorded up to February 2020 lambing. The data were analyzed by least square analysis. The body weight at 6, 9 and 12 months of age were significantly higher in elite ewes (17.22±0.21, 22.17±0.24, 26.19±0.27 vs 14.29±0.10, 18.09±0.13, 21.38±0.14). Elite Sandyno lambs weighed significantly higher than elite Nilagiri lambs at all stages. Highest ADG was observed in Sandyno elite ewe lambs during 6 months to 9 months period (62.98±2.80 g). The ADG was significantly higher in elite ewes during this period and from 9 months to 12 months (54.79±1.85 and 44.38±1.61 vs 37.52±0.98 and 33.70±0.87). The average birth weight, weaning weight and weaning percentage of born elite Nilagiri lambs (2.88±0.15, 11.52±0.77 and 93.54% vs 2.63±0.15, 10.02±0.76 and 90.82%) and Sandyno lambs (3.41±0.17, 12.91±0.86 and 94.69% vs 3.04±0.17, 11.31±0.84 and 91.73%) were significantly higher. The survivability of twin lambs was significantly higher in born elite lambs. The findings will help in promoting genetic selection and improved nutritional management in sheep farms from weaning to improve growth rate, better lamb crop and good survivability. Marginal increase in the feed would bring a substantial improvement in the performance of the sheep.

Schmallenberg virus infection suspected in a calf born to an imported heifer.

Schmallenberg virus infection suspected in a calf born to an imported heifer.

Production Objectives, Reproductive Performance and Selection Criteria of Indigenous Sheep Types in Meket and Gidan Districts, North Wollo Zone, Ethiopia

This study was aimed to generate comprehensive information on production objectives, reproductive performance and selection criteria of indigenous sheep types under farmer’s management condition in Meket and Gidan districts, North Wollo Zone. Ethiopia. Multistage purposive sampling was employed based on the potential of sheep production. Accordingly 6 rural kebeles (3 from each district) were considered purposively. About 240 households (120 from each district) were used for household survey. Statistical package for social sciences (SPSS 16.0 2007) was used to analyze data. The main objectives of keeping sheep were for income generation followed by meat consumption across the districts compared. Sexual maturity age of Meket ram was 9.04 months whereas Gidan ram was 8.51 months. The average age at first lambing, lambing interval and lifetime lamb crop of Meket Sheep were 16.04 months, 9.14 months and 8.92 lambs, respectively. The corresponding values for Gidan Sheep were 15.57 months, 8.66 months and 9.77 lambs, respectively. Color, growth character and appearance were the most important traits considered by farmers to select breeding rams in both study districts. Ages at first sexual maturity, color, lamb growth and pedigree were the most important trait in choosing of breeding ewes in Meket district. Whereas Ages at first sexual maturity, color, tail type/length and pedigree were the most important trait in choosing of breeding ewes in Gidan district. Therefore, this finding was put baseline for understanding about production objective, Reproductive performance and selection criteria of Sheep and serve as a base for designing a sustainable breeding programme and selection strategies in the study area.

PSX-38 Reproductive performance of Dorper ewes with varying days post-partum to ram introduction in the non-breeding season

Abstract With the decrease of a wool favored market, hair type sheep have become increasingly popular for lamb markets. In Texas, the most popular hair type breed of sheep is the Dorper. Various breed characteristics make the Dorper sheep an excellent candidate for an accelerated lambing system. Reproductive performance of Dorper ewes with various lengths of post-partum interval, during the traditional non-breeding season, was determined. During May (13L:11D), 2+ yr-old multiparous ewes (n = 28) were joined with a fertile ram for 30 d. Weekly blood samples were taken for progesterone analysis. Ewes were blocked according to length of post-partum interval (lamb to ram): short (SPP; n = 10, 100 ± 2.7 d), mid (MPP; n = 11, 130 ± 0.68 d) and long (LPP; n = 7, >200 d). Weaning age of lamb(s) from previous parturition was similar for SPP (62 ± 3.2 d) and MPP (67 ± 0.6 d). Interestingly, 11% of the ewes had a functional CL at initiation of the study (P4 > 1.5 ng/mL). Mean body condition score for SPP, MPP, and LPP ewes were 2.8 ± 0.08, 3.1 ± 0.09, and 3.7 ± 0.08, respectively. Pregnancy rates were similar between MPP (100%), LPP (100%) and SPP (60%). Overall, pregnancy rate was 87% and a lamb crop (lambs per ewe exposed) was 1.3 ± 0.09. Twinning rate for SPP, MPP, and LPP was 20%, 73%, and 43%, respectively. Pregnancy rate in SPP ewes may indicate carryover of the suppressive effects of lactation and suckling. Results suggest a lamb to ram interval of >100 d is sufficient for response to the ram effect and resumption of estrous cycles in a majority of ewes during photoperiod of 13L:11D. We conclude Dorper sheep have the reproductive capacity to successfully meet the production goals of accelerated lambing systems and thus, the potential for optimized lamb production.

Reproductive Qualities of Romanov Sheep with Regard to the Paratypic Factors

The article discusses the results of own studies of the authors, the literature data, and the best practices of Romanov sheep breeding. The research was performed at the two Romanov sheep pedigree breeding units in the Tver region, LLC Rassvet and LLC PF Pokrov. This breed has several advantages, such as the possibility of insemination in any season, early maturing, multiparity, the quality of sheepskin, and the taste of the lamb meat. The authors studied the productivity and the reproductive ability of ewes depending on the season, the age of insemination, the live weight, the birth type of the lamb crop. More lambs are obtained in the lambings during the autumn and winter from the ewes after three and more lambings. The survival rate is higher in the winter and summer lambings. The optimal time of insemination is 12 – 13 months. At these farms, three lambings were obtained in two years.

Physiology of reproductive seasonality in sheep – an update

ABSTRACTThe seasonal breeding in sheep poses a challenge in improving productivity, owing to the incomplete knowledge of the mechanics of seasonal breeding, effective strategies for increasing the lamb crop are restricted. A major mechanism responsible for seasonal reproduction is a striking increase in the responsiveness of gonadotropin-releasing hormone (GnRH) neurons to the negative feedback effects of estradiol that peaks during anestrous and decreases in the breeding season. Melatonin does not directly drive seasonal changes in reproduction; rather it appears to synchronize an endogenous circannual rhythm. The Pars Tuberalis (PT) is a single common region across species that shows strongest MT1 expression. Melatonin acts through high affinity, G-protein coupled receptors located in thyrotroph cells in PT of the pituitary, controlling the production of the hormone, thyrotropin (TSH). Probably, the thyroid hormones serve as a connecting link between environmental cues and reproductive activity. Two very important peptides viz. kisspeptins and RFamide relative peptide appear to be key targets of thyroid hormones. Kisspeptin has been demonstrated as a potent GnRH stimulator and RFRP as an inhibitor which gets modulated with the season and controls reproductive activity in sheep.

Carbon and blue water footprints of California sheep production.

While the environmental impacts of livestock production, such as greenhouse gas emissions and water usage, have been studied for a variety of US livestock production systems, the environmental impact of US sheep production is still unknown. A cradle-to-farm gate life cycle assessment (LCA) was conducted according to international standards (ISO 14040/44), analyzing the impacts of CS representing five different meat sheep production systems in California, and focusing on carbon footprint (carbon dioxide equivalents, CO2e) and irrigated water usage (metric ton, MT). This study is the first to look specifically at the carbon footprint of the California sheep industry and consider both wool and meat production across the diverse sheep production systems within California. This study also explicitly examined the carbon footprint of hair sheep as compared with wooled sheep production. Data were derived from producer interviews and literature values, and California-specific emission factors were used wherever possible. Flock outputs studied included market lamb meat, breeding stock, 2-d-old lambs, cull adult meat, and wool. Four different methane prediction models were examined, including the current IPCC tier 1 and 2 equations, and an additional sensitivity analysis was conducted to examine the effect of a fixed vs. flexible coefficient of gain (kg) in mature ewes on carbon footprint per ewe. Mass, economic, and protein mass allocation were used to examine the impact of allocation method on carbon footprint and water usage, while sensitivity analyses were used to examine the impact of ewe replacement rate (% of ewe flock per year) and lamb crop (lambs born per ewe bred) on carbon footprint per kilogram market lamb. The carbon footprint of market lamb production ranged from 13.9 to 30.6 kg CO2e/kg market lamb production on a mass basis, 10.4 to 18.1 kg CO2e/kg market lamb on an economic basis, and 6.6 to 10.1 kg CO2e/kg market lamb on a protein mass basis. Enteric methane (CH4) production was the largest single source of emissions for all CS, averaging 72% of total emissions. Emissions from feed production averaged 22% in total, primarily from manure emissions credited to feed. Whole-ranch water usage ranged from 2.1 to 44.8 MT/kg market lamb, almost entirely from feed production. Overall results were in agreement with those from meat-focused sheep systems in the United Kingdom as well as beef raised under similar conditions in California.

ASAS-SSR Triennial Reproduction Symposium: Looking Back And Moving Forward-How Reproductive Physiology Has Evolved: Male reproductive behavior: sensory signaling in the brain of low-performing domestic rams.

Rams are selected for genetic traits a producer desires to propagate in his flock. Even though practically all sheep are naturally bred, rams are rarely evaluated for expression of sexual interest or behavior. Research at the U.S. Sheep Experiment Station reported that the proportion of rams with limited interest in ewes was nearly 30% of the total number of breeding rams. Breeding soundness tested rams with low sexual interest sire less than 16% of the lamb crop. Although producers recognize the problem, their usual solution is to increase the number of rams in breeding flocks decreasing the risk of open ewes. Increased costs and a lack of genetic progress are clearly important considerations, but the biological question as to what controls sexual interest remains intriguing. Circulating concentrations of testosterone do not differ by sexual interest among rams. However, following exposure to estrous ewes, sexually active, but not inactive, rams exhibit an increase in LH pulsatile activity, a biological response to sexual stimuli. This begs the question as to whether sexually inactive rams recognize sexual cues. Using c fos activity as an indicator of neural activity, differences in the olfactory pathway were compared among sexually active and inactive rams. Differences in fos activity were not detected in the olfactory bulb or medial amygdala. However, sexually inactive rams had lower fos activity in the central amygdala, bed nucleus of the stria terminalis, and medial preoptic area of the hypothalamus following exposure to sexual evocative olfactory stimuli. This suggests sexually inactive rams detect olfactory cues but have decreased vigilance to sensory stimuli and a muted response to sexual signals in areas of the brain required for the execution of sexual performance. With the amygdala receiving and integrating sensory signals from many areas of the brain, sexually inactive rams may lack normal reward mechanisms contributing to their lack of sexual interest. Rams with limited sexual interest have decreased dopamine synthesis and a lower expression of dopamine D2 receptors following exposure to sexual stimuli. Thus, a tempered reward pathway in combination with decreased vigilance and sensory processing in the amygdala may reduce stimulation and/or responsiveness in areas of the brain required for expression of sexual behavior.

Effect of Non-Genetic Factors on Reproductive and Growth Performance of Abera Sheep under Community Based Breeding Program in SNNPRS Ethiopia

The study was conducted in Sidama Zone, Dara District Southern Ethiopia. The intention was to investigate the effect of non-genetic factors on reproductive and growth performance of Abera sheep in the District. For this study three years (2013-2015) performance data were obtained from Hawassa research center, Dara sub-site. Study identified age at first lambing (AFL) and lambing interval (LI) of the sheep were 9.6 and 12.9 months, respectively; while annual reproductive rate and litter size of the ewes were 1.9 and 1.5 heads. Average birth weight, weaning weight and 6 month weight of Abera sheep were 2.8, 12.3 and 18.5 kg, respectively; while pre and post weaning average daily weight gains were 106 and 40 g/day, respectively. Birth type, sex and year had significant (p<0.05) effect on birth weight (BWT), weaning weight (WWT) and six-months weight; whereas season and parity had significant (P<0.05) effect on BWT and WWT only. Sex and birth type had significant (p<0.01) effect on pre-weaning average daily gain whereas year, season and parity had significant effect on both pre and post-weaning average daily gain. There was within breed variability in growth traits, which were significantly influenced by non-genetic factors like birth type, sex, year, season and parity. Selection for further improvement to achieve higher lamb crop with superior growth performance should be prioritized as within population variability is raw material for improvement through selection. Molecular characterization should also be carried out to identify uniqueness of Abera sheep.

Lifetime Reproductive and Lamb Crop Yields of Fat-tailed Naeemi and Imported Border Leicester Merino Ewes in Intensive System of Production

Local fat-tailed and imported thin-tailed sheep breeds are used for lamb production in hot arid zones. These animals are exposed to an extended summer (seven months) and shorter autumn, winter and spring seasons. The present study examined relative reproductive and lamb crop yields of low and high prolific Naeemi (N) and Border Leicester Merino (BLM) ewes under the intensive management system respectively. Mating systems used were N×N pure breeding and BLM×N rams in three-way crossing. The BLM ewes gave birth to 1.48 lambs per ewe per year as compared to 0.78 lambs per ewe per year for N. The weight of lambs born per ewe was 35% higher and weight weaned 45% higher for BLM ewes compared to N ewes.The lamb mortality was 10% with no significant differences between breeds. The parity significantly (P≤0.05) affected all reproductive traits in both the BLM and the N ewes, except the litter size in N, which was unaffected by parity. The N showed maximum reproduction at second parity (1.08 lambs/ewes) and BLM at third parity (1.63 lambs per ewe). While the lambs from BLM ewes’ first parity showed the highest mortality (21%), lambs from fifth parity showed the lowest mortality (4.5%). The weight of lambs born and weaned was significantly higher (P≤0.05) in autumn-mated than summer-mated BLM ewes. For BLM ewes, mortality was significantly higher (P≤0.05) in summer-born lambs than the lambs born in autumn, winter or spring. This study has demonstrated a moderate lifetime productivity of local N ewes and marked superiority of BLM to N for ewe reproduction and lamb crop yields under the intensive management system.

1727 Contribution of hair sheep to small ruminant profitability

Hair sheep numbers in the United States have increased dramatically in the past twenty years as documented by breed registry data. Characteristics promoted by hair sheep producers include: moderate or small framed, easy care, parasite resistant, twinning, productivity in extensive systems, aseasonal breeders, and adapted to heat and humidity. These descriptors suggest that hair sheep have the potential to add to the profitability of small ruminant production in the USA. Two hair sheep breeds rank among the top six breeds for numbers of sheep registered in the USA from 2002 to 2015. The increase in hair sheep registrations occurred while the vast majority of wool sheep registries experienced declines of 25–75% in their registration numbers from 1990 to 2015. Research results from three research stations will be discussed since they document productivity of hair sheep and hair sheep crosses. These stations include USDA ARS Meat Animal Research Center in Nebraska, USDA ARS Small Farm Research Center in Arkansas, and Texas A&M Agrilife Research Center in San Angelo, Texas. Data from these stations and other university studies find that the weights of weaned and finished hair sheep lambs are well suited to markets and regions of the country that reward the non-traditional or light lamb market. In the Nebraska and Arkansas production systems, hair sheep genetics produced 150–200% lamb crops in forage-based systems compared to annual NASS reports of 110% for the United States. In west Texas, research results indicate that lamb markets differentially impact hair sheep (Dorper) and wool sheep (Rambouillet) producers based on corn prices and weather (Sheep and Goat Research Journal, In Press). During drought years, Dorpers wean significantly more lambs. When corn prices are high, Dorpers bring premium prices for the light lamb, non-traditional markets. When corn prices are low, wool feeder lambs bring premium prices. A significant percentage of the hair sheep operations, using breed association membership, are located in regions of the country where sheep numbers have traditionally been low, especially the Southeastern region. It is suggested that lack of shearers, decreased quality and quantify of wool, resistance to parasites (documented by Virginia Tech, LSU, USDA Booneville, among others) and adapted to heat and humidity help with popularity of these breeds in this region.

Effects of breed, parity and post-mating nutrition on reproductive wastage and pregnancy outcomes of Egyptian sheep

The aim of this work was to investigate the effects of breed, parity and post-mating nutrition on reproductive wastage and pregnancy outcomes in subtropical sheep. The experimental design was completely randomized and different groups of ewes were arranged factorially (2×2×3) according to the breed (Rahmani or Barki), parity of the ewes (nulliparous or parous) and post-mating nutritional regimen through the first 45 days of pregnancy (70%, 100% and 130% of maintenance requirements). Barki ewes had higher ability to store back fat through the last third of pregnancy compared to Rahmani ewes. The parous ewes had higher body weight gain and higher body condition score through pregnancy, while they lost lower body weight and body condition score through suckling. The under-nourished ewes had lower body weight, body condition score, back fat and back muscle throughout the whole reproductive cycle. Higher reproductive wastage at weaning was observed in the nulliparous ewes (70%) compared to the parous ones (42%). The under- and the over-nourished groups had a double-fold reproductive wastage through different times of reproductive cycle compared to those fed the maintenance requirements. The parous and the moderately-fed sheep had higher proportion of lambs born, kilograms born, lambs weaned, kilograms weaned and ewes weaned to ewes conceived. Therefore, to maximize lamb crop at weaning, it is important to control the feeding allowance of ewes in early pregnancy to be similar to the maintenance requirements.

Fasciola hepatica: A comparative survey of adult fluke resistance to triclabendazole, nitroxynil and closantel on selected upland and lowland sheep farms in Northern Ireland using faecal egg counting, coproantigen ELISA testing and fluke histology

In order to investigate the incidence and distribution of adult fluke resistance to the fasciolicide tricalbendazole (TCBZ) amongst populations of Fasciola hepatica in sheep flocks in Northern Ireland (NI), individual rectal faeces samples were collected from 3 groups of 20 sheep, before (pre-dose), and 21 days after (post-dose) treatment of the animals with TCBZ, nitroxynil or closantel, on each of 13 well-managed sheep farms distributed across the province. The efficacy of each flukicide was determined for each farm, using faecal egg count reduction (FECRT) and F. hepatica coproantigen ELISA testing. In certain flocks, 2 sheep with high pre-dose faecal egg counts (FEC) were killed 3 days and 21 days respectively after TCBZ treatment, and the histology of the fluke reproductive organs was compared with that of flukes from untreated sheep, and from sheep treated with nitroxynil or closantel 2 days prior to death, using haematoxylin and eosin (H&E) staining and an in situ hybridisation method (TdT-mediated dUDP nick end labelling [TUNEL]) to demonstrate apoptosis. Results from FECRT revealed that in all flocks with a high fluke burden, TCBZ was ineffective in treating chronic fasciolosis, and this finding was generally supported by the results of the coproantigen reduction test (CRT). The histology of reproductive organs of flukes from TCBZ-treated sheep in these flocks was normal, when compared with untreated flukes, and this, together with the FECRT and CRT findings, indicated a likely diagnosis of TCBZ resistance in all the flocks with a high fluke burden. In contrast, nitroxynil and closantel were found to be fully effective against TCBZ-resistant flukes in each of the flocks bearing a high chronic fluke burden. All of the flocks with a high fluke burden and TCBZ resistance were managed on lowland in the South and East of NI. Upland flocks, in the North and West, had low fluke burdens, or were clear of infection; and FECs were too low to allow valid resistance testing. The study highlights the high level of penetration of TCBZ resistance throughout F. hepatica populations in areas of intensively managed sheep production with a high level of fluke challenge. Further, it emphasises the importance of pre-emptive chemotherapeutic action against chronic fasciolosis, using flukicides effective against the egg-producing adult flukes to minimise pasture contamination for the next season's lamb crop. This study also exemplifies the use of several complementary methods (FECRT; CRT; fluke histology; comparative anthelmintic efficacy testing) for confirmation of a diagnosis of fluke drug resistance.

Performance of purebred Welsh Mountain and crossbred ewes in a hill environment

The aim of this study was to compare the body weights, body condition scores, survival and litter weights of lamb produced by pure Welsh Mountain ewes with those of crossbred Cheviot, Lleyn, Poll Dorset and Texel ewes in a hill environment. Ewes were mated to Suffolk rams and recorded over the first 3 seasons of production. Between lambing and weaning, ewes rearing single lambs grazed semi-natural hill swards (1.5ewes/ha) and those rearing twins grazed improved enclosures (10ewes/ha). Crossbreeding significantly (P<0.001) increased body weights at all ages, with values for four-year old ewes of 45.9, 57.2, 51.6, 57.8 and 58.5kg in purebred Welsh Mountain and Cheviot, Lleyn, Poll Dorset and Texel crossbred ewes respectively. Individual lamb growth rates from birth to 8 weeks and from 8 weeks to weaning were significantly higher in the progeny of crossbred ewes (P<0.001) with highest growth rates for lambs reared by Poll Dorset and Texel cross ewes. Individual lamb weaning weights were 27.0, 29.4, 29.2, 30.4 and 30.7kg for lambs reared by purebred Welsh Mountain and Cheviot, Lleyn, Poll Dorset and Texel crossbred ewes respectively. Survival rates to third mating were 0.73, 0.77, 0.83, 0.72 and 0.75 (P<0.05), litter size reared was 1.22, 1.33, 1.49, 1.43 and 1.25 (P<0.001) and litter weights at weaning were 37.1, 43.5, 46.1, 46.5 and 44.2 (P<0.001) for purebred Welsh Mountain and Cheviot, Lleyn, Poll Dorset and Texel crossbred ewes respectively. Efficiency expressed as kg litter weight/kg ewe pre-tupping weight0.75 was significantly improved (P<0.001) by crossbreeding. Total litter weight at weaning over three lamb crops per ewe entering the flock was increased from 78.4kg in purebred Welsh Mountain ewes to between 97.1kg in Cheviot and 109.7kg in Lleyn crossbred ewes. It is concluded that where feed resources are adequate, the retention of crossbred ewes in the hill flock can give significant improvements in productivity.

Reproductive performance of rams in three producer range flocks: Evidence of poor sexual behavior in the field

Poor mating behavior increases ram costs and extends the lambing season while decreasing genetic progress. Producers recognize the importance of ram libido; however, time, labor, and facility constraints limit routine evaluation of males for libido. The current experiment determined the incidence of low- and high-sexually performing rams based on the number of lambs sired by each ram in three range flocks. Rams were evaluated for breeding soundness prior to joining with females. Genomic DNA was extracted from blood samples collected from all rams, and approximately one-third of the lambs and their dams. Microsatellite markers were used to determine parentage. Number of lambs expected to be sired by each ram was established by calculating 99% confidence intervals, based on the expectation that each ram would have equal number of lambs. Rams siring more or less lambs than expected were categorized as high or low sexually performing rams, respectively. Paternity was established for >80% of the lambs sampled. Rams which had higher than expected numbers of lambs made up 23–29% of the ram population but sired from 39.4% to 70% of the lamb crop. Low performing rams (23–43% of the ram population) sired from 3.2% to 16.2% of the lamb crop. Since fertility was evaluated prior to mating, differences in ram fecundity may reflect the expression of sexual behavior in a multi-sire range flock setting. Rams are generally selected for breed characteristics and potential influence on flock genetics will be greater for high- than low-sexually performing rams.

Influence of end-grazing forage residual and grazing management on lamb growth performance and crop yield from irrigated dual-purpose winter wheat

The effects of end-grazing forage residual and continuous v. rotational grazing systems on prime lamb performance, grain yield and quality were examined in an irrigated dual-purpose winter wheat (cv. Mackellar) crop in Tasmania. The design was a two end-grazing residual (400 and 800 kg/ha of dry matter (DM) at Zadoks Growth Stage 30, Low and High respectively, 0.2 ha plots) × two grazing system (continuously, or rotationally grazed in four subplots) factorial, replicated three times. Mixed-sex, second-cross lambs [37 kg liveweight (LW), 2.5 body condition score, 45 kg DM/head initial feed allowance] grazed for a total of 46 days before removal. Initial feed availability was 1875 kg DM/ha, with final residuals of 520 ± 57 and 940 ± 70 kg DM/ha for the Low and High treatments respectively. Particularly for the Low residual, in vitro DM digestibility and crude protein at stem elongation were reduced (P &lt; 0.05) by rotational compared with continuous grazing. The weekly lamb growth rate (g/day) during the first 5 weeks of grazing was linearly related to average weekly available DM in kg/ha (GR = 0.35 ± 0.041 × DM – 194 ± 49.0, P &lt; 0.01, R2 = 0.56). Total LW produced (336 ± 11.7 kg/ha), and grain yield (6.9 ± 0.21 t/ha), protein (11.4%), screenings &lt;2.2 mm (10.9%) and 100 grain weights (3.82 g DM) were not different between treatments. There were no advantages of rotational grazing compared with continuous grazing. Irrigated dual-purpose winter wheat can be continuously grazed by lambs up to a 500 kg DM/ha residual at stem elongation without compromising total LW produced, grain yields or grain quality.

Effects of plane of nutrition of ewes in early and mid-pregnancy on performance of the offspring: Female reproduction and male carcass characteristics1

This study investigated the effects of different planes of nutrition in early pregnancy (EP) and mid-pregnancy (MP) of crossbred ewes on carcass characteristics of male offspring and reproductive performance of female offspring. During EP (d 1 to 39 after synchronized mating) ewes were allocated 60% (low, L-EP), 100% (medium, M-EP), or 200% (high, H-EP) of their energy requirements for maintenance. Between d 40 and 90 (MP), ewes were then allocated 80% (M-MP) or 140% (H-MP) of their maintenance energy requirement. After d 90, all ewes were fed to fully meet energy requirements for late pregnancy. Male offspring (n = 83) were reared on a grass-based system and slaughtered at 42, 46, or 50 kg of BW. Female offspring (n = 60) were reared on a grass-based system, mated at 8 mo, and performance recorded until weaning of their first lamb crop. Concentrations of leptin, an adiposity indicator, in female offspring varied with the plane of maternal nutrition in early pregnancy. The L-EP offspring had greater leptin concentrations than H-EP offspring (P = 0.04), with M-EP offspring showing intermediate concentrations. Reproductive performance of female offspring was not affected by maternal plane of nutrition (P > or = 0.16). Female H-EP offspring gave birth to heavier lambs (generation 2 offspring) than M-EP (P = 0.006) with L-EP offspring intermediate. Male offspring of L-EP dams showed a trend toward poorer carcass conformation (P = 0.06) and increased fat classification (P = 0.07), consistent with increased fat depths over the loin (P = 0.02). There was a significant interaction between plane of nutrition in early pregnancy and mid-pregnancy for female offspring BW at 2 mo postmating and 16 wk postlambing (P < or = 0.04), and for male offspring perinephric and retroperitoneal fat and tissue depth (P < or = 0.02). For dams offered diet L-EP during early pregnancy, diet H-MP gave heavier offspring with more perinephric and retroperitoneal fat. In contrast, for dams offered diet H-EP during EP, diet M-MP gave offspring that were heavier or fatter or both. Maintenance level of nutrition in EP followed by M-MP or H-MP treatments resulted in offspring intermediate in fatness and BW. The data indicate that adaptations in EP and MP to compensate for nutritional deprivation or nutritional excess can alter the BW, adiposity, conformation, and leptin concentrations of offspring. Such changes have potential to alter health and lifetime productive performance.