On two farms it was noted that after routine treatment with monepantel, fecal egg counts failed to drop. This was accompanied by lambs mortality due to Haemonchus contortus infection. The aim of this work was to evaluate the efficacy of monepantel to control gastrointestinal nematodes (GIN) in two sheep farms, in Uruguay. A Fecal Egg Count Reduction Test (FECRT) was subsequently performed at the Experimental Stations Glencoe of INIA Tacuarembó (Farm 1) and Sheep Unit of INIA La Estanzuela (Farm 2) using the World Association for the Advancement of Veterinary Parasitology guidelines. On Farm 1 the FECRT was performed using 6–8 month old Corriedale or Merino Dohne x Corriedale male lambs naturally infected with GIN. On day 0 pre-treatment, three groups of 15 lambs each were selected, blocked by fecal egg count level (FEC) and randomly assigned to one of the following: Group 0 = untreated control, Group 1 = treated with monepantel (Zolvix®, Novartis Animal Health Inc.) from stock previously purchased; Group 2 = treated with monepantel from stock provided by the supplier, at the recommended dose of 2.5 mg/kg of body weight. Fecal samples were collected directly from the rectum from each lamb on day 0 and on day 9 post-treatment. On Farm 2, the FECRT was conducted on a group of 8 month old male lambs Milchschaff x Finn. At this farm, 10 lambs were randomly allocated to be treated with monepantel (Group 1) and 10 lambs were randomly allocated to remain as untreated control (Group 0) using the same protocols as Farm 1. On farm 1 the FECR was 0.0% (95% CI = 0.0 – 49.0) and 42.0% (95% CI = 0.0 – 75.0) for Group 1 and Group 2 respectively. For Farm 2, the FECR was 82.1% (95% CI = 36.0 – 99.0). Haemonchus spp was the resistant genus. Poor effcicacy of monepantel in treating GIN parasites was demonstrated on both farms.

Extensive cattle production on native grasslands is vital to the sustainability of the South American Pampas, and the inclusion of tannin-containing legumes can increase farm profitability, improve nitrogen (N) use and reduce greenhouse gas (GHG) emissions. This study quantified the effects of adding tannin-containing legumes to native grasslands on enteric methane (CH₄) emissions, animal performance and N balance in cattle. A crossover design trial was conducted with 22 beef heifers under two treatments: native grassland (NG) and native grassland with the addition of Lotus uliginosus and L. angustissimus (NG+L). The results showed that forage mass disappearance was similar between treatments; however, 54% of the forage disappearance in the NG+L corresponded with legumes, indicating that the heifers in this treatment consumed a better-quality diet. While individual CH₄ emissions were similar between treatments, heifers grazing the NG+L showed a higher average daily gain (ADG) and lower emissions intensity than heifers grazing NGs (0.25 vs. 0.58 g CH₄/g ADG, p < 0.05). Additionally, they also ingested 20% more N and were more efficient in its utilization. Incorporating tannin-containing legumes into native grasslands can improve animal productivity and N use efficiency while reducing the intensity of enteric CH₄ emissions.

The effect of condensed tannins (CT) in the pasture (Lotus uliginosus cv. E-Tanin) and/or quebracho and chestnut extracts on lamb carcass and meat quality was evaluated. Two experiments were conducted in consecutive years with 60 crossbreed lambs each year. The animals were stratified by live weight (LW) and randomly assigned to the treatments: white clover grazing (WC); WC plus concentrate supplementation (WC + C); WC plus concentrate supplementation and quebracho and chestnut extract (WC + C + CT); Lotus uliginosus grazing (E-Tanin); E-Tanin plus concentrate supplementation (E-Tanin + C); E-Tanin plus concentrate supplementation plus quebracho and chestnut extract (E-Tanin + C + CT); with two repetitions each year. Pasture type affected loin weight, which was greater (P < 0.05) in lambs grazing WC than E-Tanin. Meat color redness (a*) was greater (P < 0.05) in supplemented treatments with C (with or without CT) than those exclusively grazing. Intramuscular fat content was not affected (P > 0.05) by the pasture, the supplementation, or the year. The proportion of dihomo-gamma-linolenic acid (C20:3-n6) was greater (P < 0.05) in lambs grazing E-Tanin compared to WC. Supplementation affected (P < 0.05) the saturated (SFA) and monounsaturated fatty acids (MUFA) proportions, and the omega 6:omega 3 ratio. Estimation of dry matter intake under grazing conditions would allow a better understanding of the effect of CT on carcass and meat quality.