Grazing Lambs Research Articles

Combining Pasture- and Animal-Based Factors to Predict Herbage or Dry Matter Intake of Lambs Grazing on Cocksfoot, Meadow Fescue and Tall Fescue Pastures

In this study, it was aimed to establish the correlations between actual dry matter intake (DMI) and some animal (body weight, (BW)) and pasture (crude protein (CP); neutral detergent fiber (NDF); in vitro dry matter digestibility (IVDMD); dry matter yield (DMY); herbage allowance (HA); herbage mass (HM); metabolizable energy (ME); relative forage quality (RFQ); total digestible nutrients (TDN)) based factors to formulate precise regression equations for DMI prediction. For this purpose, data (n = 36, 2 years × 3 blocks × 6 data collection) were utilized for two grazing seasons (2020–2021) on cocksfoot (Dactylis glomerata), meadow fescue (Festuca pratensis) and tall fescue (Festuca arundinacea) mixed pastures with Karayaka male lambs at an average age of 2 months for 60 days in each season. Positive correlations were determined between DMI and BW (0.777), HA (0.814), DMY (0.844), and NDF (0.609), while DMI had negative correlations with IVDMD (-0.738), RFQ (-0.357), CP (-0.209), TDN (-0.177) and ME (-0.039). In addition, animal and pasture–based factors were evaluated by principal component analysis to determine the in–cooperating variables in variance. As a result, equations were developed by using parameters with high correlation coefficient and the best–fit 3 equations for predicting DMI of lambs grazing cocksfoot, meadow fescue and tall fescue pastures: (I) -1224.09 + 39.90BW (kg) + 33.69HA (kg DM/ kg BW) + 8.22NDF (% of DM), r2=0.815, II) -701.47 + 18.96BW (kg) + 673.61DMY (kg/ per square meters) + 8.19NDF (% of DM), r2=0.807, III) -325.32 + 43.49HA (kg DM/kg BW)-2.21IVDMD (%) + 8.57NDF (%), r2=0.786).

Lambs Grazing With Adult Ewes Prefer Forbs With High-Nutrient Content in Native Grasslands Dominated by Leymus chinensis and Stipa grandis.

Grazing livestock in grasslands face the challenge of obtaining sufficient nutrition due to uneven distribution of plant species and fluctuating vegetation productivity and nutrient levels. In northern China, Leymus chinensis and Stipa grandis are the dominant perennial species in native grasslands, but they provide limited nutrition compared to forbs with higher crude protein (CP) content. While dietary ingredients can affect the nutritional intake of grazing livestock, the influence of different grazing strategies on dietary selection remains unclear. In this study, three sheep grazing strategies (lambs alone, mixed lambs and ewes, and ewes alone) were used to explore dietary selection. We investigated the influence of vegetation characteristic (above-ground biomass production, height, and species diversity) and foraging behavior (feed intake, organic matter digestibility, and daily grazing time) on the mechanisms of dietary selection (taxonomic family richness and composition). Forage consumption across the grazing strategies revealed that species from Poaceae, Rosaceae, and Cyperaceae families were frequently consumed. Both ewes and lambs in the mixed-grazing strategy preferentially consumed forbs with diverse species composition (Jacob's D > 0), which contained higher CP than those available in the overall vegetation (p < 0.05). In addition, dietary richness was significantly (p < 0.05) influenced by vegetation species diversity except for animals in the lambs alone strategy. Compared to lambs in mixed-grazing, lambs alone had both greater daily grazing time and consumption of grass with lower digestibility (p < 0.05). Our study is the first to demonstrate that lambs can develop a similar dietary selection and behavioral pattern when grazing with adult ewes in temperate grasslands. Our study indicates that the conservation of species diversity in native grasslands is critically beneficial to livestock nutrition.

Performance, Meat Quality and Gene Expression of Grazing Lambs Supplemented with Macadamia Oil and Vitamin E

Macadamia oil has high concentrations of oleic and palmitoleic fatty acids, which can increase tissue sensitivity to insulin, improving glucose absorption efficiency, and reducing lipogenesis through gene modulation. The objective of this study was to evaluate the effects of macadamia oil associated with vitamin E supplementation on performance, blood parameters, meat quality and sensory characteristics, meat fatty acid profile, and expression of genes associated with lipid metabolism in grazing lambs. The experimental treatments were control diet (Control), Control + 0.1% of body weight of macadamia oil (MO), MO + 745 IU of vitamin E/dry matter (MOVE). Macadamia oil improved feed efficiency, reflecting a lower dry matter intake, as the average daily weight gain did not differ from Control. Meat quality parameters were not affected by macadamia oil or vitamin E supplementation. Supplementation with macadamia oil improved meat appearance, flavor, and overall liking. Supplementation with macadamia oil provided a higher proportion of C18:3 n3 and a lower proportion of CLA. The expression of SREBP-1c, PPAR-α, SCD1, and ELOVL6 genes were not modified with the supplementation of macadamia oil and vitamin E. In conclusion, supplementation with macadamia oil improves feed efficiency and meat quality; and the inclusion of 745 IU of vitamin E/kg of dry matter for grazing lambs reduces 36% of lipid oxidation of the meat.

Physical and biochemical characteristics of tropical grass and legume pastures grazed by lambs

AbstractLarge areas of tropical grass pastures are not grazed by lambs because of the difficulties in managing high growth rate swards with high selective animals. The objective of this study was to evaluate the physical and biochemical characteristics of tropical pastures offered to lambs in continuous grazing. An upright grass and a shrub legume were set out in three pasture types and grazed by lambs: (1) aruana grass monoculture (AG—Panicum maximum Jacq. cv. IZ‐5), (2) pigeon pea monoculture (PP—Cajanus cajan [L.] Millsp. cv. Anão) and (3) contiguous swards (CS), half of the paddock with AG (CSAG) and half with PP (CSPP). The pastures were evaluated for structural characteristics, production, nutritional composition and antioxidant concentrations in four periods over 92 days of continuous grazing by lambs. Hand plucking samples, similar to animal diet, were collected for chemical analysis. Regarding height, the PP legume monoculture after 42 days of grazing had uncontrollable growth by the lambs, reaching 1.2 m in height. This same legume but as a CS beside AG (CSPP) was maintained at a lower and similar height throughout the experimental periods. In general, the leaf:stem ratio of the different pastures decreased over the experimental periods from 0.7 to 0.2. In most periods, the CS showed intermediary nutritional quality compared to AG and PP. The alpha‐tocopherol content was similar among swards, with an average of 137.2 ± 13.67 mg/kg of green matter (p &gt; .05). Pigeon pea showed the highest levels of total tannin and condensed tannin at 63 and 92 days (p &lt; .05). The use of tropical grass together with a legume provides a better physical structure of the pigeon pea for grazing lambs than when monoculture of this species.

Review of Feeding Systems Affecting Production, Carcass Attributes, and Meat Quality of Ovine and Caprine Species.

Growth rate, carcass attributes, and meat quality traits of small ruminants (i.e., sheep and goats) depend on various factors, among which the feeding system is one of the most important factors. However, how feeding systems affect these parameters differ between sheep and goats. Therefore, this review aimed to evaluate the differences in how different feeding systems affect the growth performance, carcass characteristics, and meat quality of sheep and goats. It also explored the effects of a new finishing strategy-time-limited grazing with supplements on these traits. Compared with stalled feeding, finishing lambs/kids on pasture-only feed reduced the average daily gain (ADG) and carcass yield, while supplemented-grazing lambs/kids had near-equivalent or higher ADG and carcass attributes. Pasture-grazing increased the meat flavor intensity and healthy fatty acid content (HFAC) of lamb/kid meat. Supplemental grazing lambs had comparable or superior meat sensory attributes and increased meat protein and HFAC compared to stall-fed ones. In contrast, supplemental grazing only improved the meat color of kids but had little effect on other meat qualities. Moreover, time-limited grazing with supplemental concentrates increased the carcass yield and meat quality in lamb meat. Overall, the effects of different feeding systems on growth performance and carcass traits were comparable between sheep and goats but differed in terms of the meat quality.

Carcass characteristics and meat quality of Texel lambs finished in Brachiaria spp. pastures with different levels of extruded urea (200S) supplementation

ABSTRACT The objective was to investigate the effects of increasing levels of extruded urea (EU) in the supplementation of lambs grazing. Crossbred Texel lambs (n = 45) were used and kept in continuous grazing in paddocks with Brachiaria spp. The design used was completely randomised, with five of EU replacing soybean meal (0; 6; 12; 18 and 24 g/kg) and two sexes (male and female). The animals were slaughtered, and qualitative and quantitative evaluations of the carcass, non-carcass components, meat quality and chemical composition were carried out. There was an interaction between level*sex for ether extract (EE) and crude protein (CP), so than the meat of the females from the treatment without EU had a higher content of EE than that used EU and the meat of the males from the treatments with 12 g and 24 g 100 kg−1 LW higher levels of CP than other treatments. For all measurements performed up to 18 g 100 kg−1 LW of EU replacing bran and soy, the results were promising, and can be fed to finishing lambs under grazing, without negatively influencing most of the carcass characteristics, components non-carcass, meat quality and chemical composition.

Disease surveillance in England and Wales, June 2022.

Disease surveillance in England and Wales, June 2022.

Different Nutritional Systems at Suckling and Finishing Phases of Lambs Grazing on Tropical Pasture

The objective of the study was to evaluate the lambs' performance in the suckling and finishing phases in different nutritional systems. The study was carried out in two phases: suckling (from birth to weaning) and finishing (from weaning to slaughter). Each phase was evaluated in two experimental periods (characterized by year). The suckling phase used 76 lambs divided into two groups: control (without supplementation) and creep feeding (with creep feeder supplementation of 20 g/kg of body weight). The lambs were distributed in the treatments according to sex and type of delivery (single or twin). The finishing phase was characterized from weaning to slaughter. Sixty-two lambs were used, 28 females and 34 males, average age of 85 days and an average weight of 19 kg, and the animals were distributed in treatments according to weight and sex. Five treatments were evaluated, animals in Brachiaria spp. receiving increasing levels of supplementation (0%, 0.8%, 1.6%, and 2.4% of BW) and confinement as a positive performance control. The creep feeding treatment presented superior performance with an average daily gain of 64.85 g more than the control treatment, which anticipated the shorter age at weaning with higher weaning weight (weaning in 64 days for supplemented lambs and 77 days for animals without supplementation). In the finishing phases, the lambs of the treatments 1.6%BW and 2.4%BW presented average daily gain similar to the confined animals and higher (p<0.05) than the treatments 0.8%BW and 0%BW. We recommend that ad libitum supplementation of creep feeding during the suckling phase is a nutritional strategy to wean heavier lambs and consequently reduce time in the finishing phase. For fattening the lambs, we recommend the inclusion of protein-energy supplementation of 1.6% BW for lambs produced in the tropical pasture.

Characterization of the Flavor Precursors and Flavor Fingerprints in Grazing Lambs by Foodomics.

Tan sheep are greatly preferred by consumers in China because of their nutritional value and unique flavor. However, the meat quality of Tan sheep has decreased due to the change in feeding systems from grazing to indoor. Studies investigating the mechanisms for the decrease in meat quality are limited. A total of 28 Tan sheep were randomly allocated to two treatments, receiving a concentrated diet, or pasture. Flavor precursors and volatile compounds were analyzed with foodomics. E-nose and E-tongue analyses suggested that the aroma and taste profiles differed between the feeding systems. The grazing lambs had higher levels of linoleic acid and n-3 polyunsaturated fatty acids (p < 0.01). Metabolomics indicated that 25 hydrophilic metabolites active in glycolipid and amino acid metabolisms were changed by the feeding system. Among the 57 volatile compounds identified, methional, γ-butyrolactone, benzaldehyde, and ethyl acetate were at concentrations significantly higher in the grazing lambs than the indoor-fed lambs (p < 0.01). These results reveal key changes in flavor precursors and flavor profiles affected by the feeding system, which may provide an initial view of the reason for consumer preference for the grazing Tan sheep.

Performance and Carcass Characteristics of Australian Prime Lambs Grazing Lucerne and Cocksfoot Pastures Are Enhanced by Supplementation with Plant Oil Infused Pellets

The aim of this study was to determine the effects of pasture (cocksfoot cv. porto (CFP) and lucerne) and supplementation of grazing lambs with pellets with or without plant oil infusion on performance and carcass characteristics. Forty-eight White Suffolk x Corriedale first-cross weaners were randomly assigned to one of four treatments in a split-plot experimental design: (1) CFP or lucerne pastures only (control); CFP or lucerne pastures supplemented with pellets infused with oil from (2) canola (CO); (3) rice bran (RBO) and (4) no oil pellets (NOP). Lucerne and CFP pastures were considered as the main plot effect, and played the role of basal pastures. Lambs grazing lucerne or CFP pastures with pellet supplementation achieved carcass weights of &gt;22 kg at 9 weeks, which met the specific requirements of Asian and United States of America export markets. Pellet supplementation did not affect final liveweight, average daily gain, body length, withers height and chest girth of grazing lambs. Dressing percentage of lambs grazing CFP pasture with pellet supplementation and lambs grazing lucerne pasture with RBO supplementation increased compared with lambs on pasture grazing only. Although supplementing lambs on CFP pasture with CO had relatively negligible impact on feed conversion efficiency, it significantly increased over the hook trade value compared with lambs grazing CFP pasture only. In conclusion, lucerne or CFP pasture plus pellet supplementation produced lamb carcasses &gt;22 kg suitable for the export market. CO had relatively low feed cost per unit daily gain (0.9 $AU/kg on CFP pasture and 0.6 $AU/kg on lucerne pasture) and could also be used as a tactical supplementation tool for increasing the carcass weight of lambs grazing CFP pasture.

Influence of tropical upright pasture structural and chemical characteristics on lamb grazing time.

Tropical pasture canopy characteristics can alter lamb ingestive behavior. Our study evaluated the ingestive behavior of young lambs in different tropical pastures to identify which variables interfere in their grazing activity. Two years of study were carried out with 54 weaned lambs distributed in three different pasture canopies: 1) monoculture of an upright grass, guinea grass (Panicum maximum; GG); 2) monoculture of a shrubby legume pigeon pea (Cajanus cajan; PP) and 3) contiguous paddock with half GG and half PP (GP). The experiment was set out in a randomized complete block design (3 blocks). Lamb ingestive behavior was observed from sunrise to sunset with records every 5 minutes. To identify the main variables that affected lamb grazing activity, a multivariate analysis of the Decision Tree was performed. Our results showed that there was no difference in the ingestive behavior parameters of young lambs in different canopies (P > 0.05). There was interaction among the canopies and the experimental periods for the variables idleness time and biting rate (P ≤ 0.05). Lambs in all canopies showed more idleness time in the first evaluation period. Lambs in canopies containing grass (GG and GP) exhibited greater bites per minute throughout the experimental period. Lamb grazing time increased 40% as experimental period progressed and plants matured. The Decision Tree identified leaf:stem ratio as the variable that most influenced lamb grazing time in GG and GP canopies while in the PP, grazing time was directly related to canopy height. The behavior of young lambs on tropical pasture is variable as there is a change in the behavioral response to canopy characteristics over time. In addition, the grazing time of these animals can be estimated by means of variables related to canopy structural characteristics (leaf:stem ratio and height) together with chemical variables.

PSX-15 Fall grazing of annual forages with fall born lambs may improve animal growth and total protein concentrations when compared to stockpiled pastures

Abstract There is a consistent demand for grass-fed livestock products in the domestic market. Alternative grazing strategies should be considered to sustain the year-round production of grass-fed products that meet consumer demand and support animal health and performance. The objective of this study was to evaluate the effect of annual forages on the growth and parasite resilience of growing lambs. We hypothesized that lambs grazing annual forages would increase their body weight at a greater rate when compared to lambs grazing stockpiled pasture. A total of 54, 60-day-old lambs (24 kg ± 4.9 kg) were stratified by weight, sex, and randomly assigned to one of three grazing treatments: 1) oats (O); 2) turnips (T); and 3) stockpiled tall fescue pasture (F). Lamb body weight and indices of parasitism were measured every 14 days. Data were analyzed using PROC MIXED in SAS. There was a treatment × day effect for body weight such that T lambs were heavier on days 42 and 56 than O and F lambs (P &amp;lt; 0.03). Furthermore, there was a treatment × day effect for average daily gain (ADG) whereas T lambs had a greater ADG on days 28 and 42 than O and F lambs (P &amp;lt; 0.0001). In addition, on day 42, F lambs had a greater ADG when compared to O lambs (P &amp;lt; 0.003). For the indices of parasitism, T lambs demonstrated lesser total plasma protein concentration on days 28 and 42 when compared with O lambs (P &amp;lt; 0.05). Forage type plays a critical role in lamb resilience to gastrointestinal parasites and body weight gain whereas T lambs showed a greater liveweight gain. However, T lambs also demonstrated lesser concentrations of total plasma protein when compared to O lambs. Under these conditions, annual forages adequately sustained the growth of fall grazing lambs.

Microbial functional traits are sensitive indicators of mild disturbance by lamb grazing.

Mild disturbances are prevalent in the environment, which may not be easily notable but could have considerable ecological consequences over prolonged periods. To evaluate this, a field study was designed to examine the effects of very light-intensity lamb grazing on grassland soil microbiomes with different soil backgrounds. No significant change (P > 0.05) was observed in any vegetation and soil variables. Nonetheless, hundreds of microbial functional gene families, but not bacterial taxonomy, were significantly (P < 0.05) shifted. The relative abundances of both taxonomic markers and functional genes related to nitrifying bacteria were also changed. The observation highlighted herein, showing a high level of sensitivity with respect to functional traits (functionally categorized taxa or genes) in differentiating mild environmental disturbance, suggests that the key level at which to address microbial responses may not be "species" (by means of rRNA taxonomy), but rather at the functional gene level.

How does barley supplementation in lambs grazing alfalfa affect meat sensory quality and authentication?

Excessive flavour in lamb meat is undesirable for consumers and can prompt purchase resistance. Volatile indoles responsible for off-flavours accumulate more in the fat of lambs on pasture than on grain and are enhanced when lambs graze alfalfa. Here, we investigated whether barley supplementation of lambs grazing alfalfa influences meat sensory quality. Using three groups of 12 male Romane lambs, we compared three feeding regimes: alfalfa grazing (AG), alfalfa grazing + daily supplementation with barley (29 g/kg live weight0.75, AGS) and stall feeding with concentrate and hay (SF). As some of the compounds involved in meat sensory traits may act as dietary biomarkers, we also investigated potential implications for meat authentication. Although barley represented 38% of the diet in AGS lambs, it did not offer any advantage for animal average daily gain or parasitism level. Animal performance, carcass weight and fatness did not differ between feeding regimes. Dorsal fat firmness tended to be greater in AG than AGS and greater in AGS than SF. Skatole and indole concentrations in perirenal and dorsal fat were lower in SF lambs than in AG and AGS lambs (P<0.01 to P<0.0001), but did not differ between AG and AGS lambs. Yellowness, chroma and hue angle of perirenal fat were lower in SF lambs than in AG and AGS lambs (P<0.001), but did not differ between AG and AGS lambs. Absolute value of the mean integral for both perirenal fat and subcutaneous caudal fat (AVMIPF and AVMISC), quantifying the intensity of light absorption by carotenoids in perirenal and subcutaneous caudal fat, respectively, were lower in SF lambs than in AG and AGS lambs (P<0.0001 for both comparisons), but did not differ between AG and AGS lambs. Meat colour was unaffected by the treatment. We confirm that lambs grazing alfalfa accumulate high levels of volatile indoles in their fat, but we show that barley supplementation to lambs grazing alfalfa is not effective in reducing fat volatile indoles concentration and excessive odour/flavour in the meat. We also confirm that both perirenal fat skatole concentration and AVMIPF are of interest for discriminating lambs that grazed alfalfa from lambs that were stall-fed, and we show that they are not effective for discriminating supplemented from non-supplemented grazing lambs.

Model Predicted DMI, Nitrogen (N) Excretion and N Use Efficiency Utilizing Plasma Urea Nitrogen (PUN) Versus Values Estimated in Conjunction with Viable Dry Matter Intake Estimates in Lambs Grazing Pasture

Model Predicted DMI, Nitrogen (N) Excretion and N Use Efficiency Utilizing Plasma Urea Nitrogen (PUN) Versus Values Estimated in Conjunction with Viable Dry Matter Intake Estimates in Lambs Grazing Pasture

Enhanced Omega-3 Polyunsaturated Fatty Acid Contents in Muscle and Edible Organs of Australian Prime Lambs Grazing Lucerne and Cocksfoot Pastures.

The enhancement of health-beneficial omega-3 long–chain (≥C20) polyunsaturated fatty acid (n-3 LC-PUFA) contents in the muscle, liver, heart, and kidney of Australian prime lambs through pasture grazing and supplementation with oil infused pellets was investigated. Forty-eight first-cross prime lambs were randomly assigned into a split-plot design with pasture type as the main plot effect and pellet supplementation as a sub-plot effect in a feeding trial that lasted for nine weeks. The n-3 LC-PUFA content in Longissimus dorsi muscle of all lambs was well above the 30 mg threshold for “omega-3 source” nutrition claim under the Australian Food Standards and Guidelines. Pasture type impacted the fatty acid contents in muscle, heart, and kidney of prime lambs. Lambs grazing cocksfoot grass only had high 18:3n-3 (ALA) and n-3 LC-PUFA contents (67.1 mg/100 g and 55.2 mg/100 g, respectively) in the Longissimus dorsi muscle, which was not significantly different (p > 0.8990) from the contents of lambs grazing only lucerne. Supplementation of pellets with or without oil infusion to grazing lambs generally decreased the ALA and n-3 LC-PUFA contents and increased the n-6/n-3 ratio in the Longissimus dorsi muscle. The fatty acid content in the internal organs of grazing lambs was also affected by pellet supplementation. The liver and kidney of grazing lambs were both “good sources” (60 mg/100 g) of omega-3. The cocksfoot grass showed considerable potential for producing healthy, premium quality meat with high contents of n-3 and n-3 LC-PUFA, which may consequently enhance the omega-3 intake of Australian lamb consumers.

Evaluación de la rentabilidad y competitividad de los sistemas de producción de ovinos en la región de Libres, Puebla

Con el objetivo de evaluar el grado en que los sistemas de producción de ovinos son competitivos y presentan ventajas comparativas, se entrevistaron a 139 productores, y se dio seguimiento a seis rebaños de tres sistemas de producción durante siete meses, en la región de Libres, Puebla. Se registró información de costos, infraestructura, actividad agrícola, mano de obra, producción y venta de ovinos. Para determinar la rentabilidad y la competitividad se utilizó la Matriz de Análisis de Política. El sistema de producción con alimentación en corral fue el más rentable y competitivo de acuerdo con los indicadores de rentabilidad privada, Relación del Costo Privado, Coeficiente de Rentabilidad Privada y la Relación del Costo-Beneficio Privado. El costo de los factores de producción fue mayor en el sistema de producción de corderos en pastoreo y fue el de menor competitividad. La Relación Costo-Beneficio Social indicó ineficiencia para reemplazar las importaciones. La producción de ovinos tuvo una estructura de mercado oligopsónica, producto de las deficiencias institucionales y ausencia de políticas de protección. Los productores utilizaron como criterio de venta el peso adulto, aunque la venta de los corderos inició entre los 30 y 90 días. Es recomendable realizar el análisis de la función de producción, para determinar la viabilidad de la venta de cordero destetado, como una opción para aumentar las ganancias de los productores y la competitividad de estos sistemas.

Diet selection and n-3 polyunsaturated fatty acid deposition in lambs as affected by restricted time at pasture

This study investigates the effects of restricted grazing time on forage selectivity and meat fatty acid deposition of lambs compared to a traditional grazing system. Results showed that the animals preferred to graze pasture species that were more palatable and lower in fibre, while demonstrating a partial preference for species with high protein levels. Leymus chinensis was more preferentially selected by lambs grazing pasture for shorter periods than longer periods. Lambs that grazed for 4 h per day had a high LNA (α-linolenic acid) intake. The accumulation of LNA and its elongation products in tissue was closely related to the LNA level in diet. Therefore, allowing lambs to graze for at least 4 h per day resulted in a meat fatty acid profile that is richer in health-promoting fatty acids. In particular, the highest DHA (docosahexaenoic acid) was observed in meat from lambs which grazed pasture for 4-h versus 8- and 12-h. It can be concluded that, in grassland systems, a healthier meat fatty acid profile for humans and the potential for better pasture management is achieved by limiting the grazing of lambs to 4 h per day rather than grazing over longer time periods.

Development of Haemonchus contortus resistance in sheep under suppressive or targeted selective treatment with monepantel

This study examined the development of resistance to anthelmintics in Haemonchus contortus in lambs under suppressive or selective treatment regimens that included monepantel. Twenty Ile de France and 20 Santa Ines lambs were allocated to two anthelmintic treatment regimens, based on body weight and nematode faecal egg counts (FEC): targeted selective treatment (TST) or suppressive treatment, both with monepantel. Lambs of the TST group were treated individually when they presented with a packed cell volume (PCV) ≤20%. On 7 October 2016, the lambs were allocated to clean pastures, where they grazed in separated paddocks by group until late February 2017. The experimental area was contaminated with nematodes that were introduced with the experimental Ile de France and Santa Ines lambs, naturally infected with gastrointestinal nematodes. To maintain the grazing lambs in the suppressive treatment group and their pasture as free of worms as possible, these lambs were treated with anthelmintics before being allocated to their paddock and then were periodically treated with monepantel. However, the use of a suppressive treatment regimen that included monepantel over a period of 3 months resulted in the emergence of a population of resistant H. contortus. In the TST group, there was a rapid and progressive reduction in the efficacy of monepantel, which at the end of the experiment was only 76%. The Ile de France lambs were all treated one or more times during the experiment, whereas only two Santa Ines lambs in the TST required treatment. In conclusion, a population of H. contortus resistant to monepantel emerged quickly during the rainy season, even when sheep were submitted to selective treatment.

865 Audio and time-lapse imagery analysis of lamb grazing behavior in silvopasture systems

865 Audio and time-lapse imagery analysis of lamb grazing behavior in silvopasture systems