The study determined the performance of equations to predict enteric methane (CH 4 ) from beef cattle fed forage-and grain-based diets. Many equations are available to predict CH 4 from beef cattle and the predictions vary substantially among equations. The aims were to (1) construct a database of CH 4 emissions for beef cattle from published literature, and (2) identify the most precise and accurate extant CH 4 prediction models for beef cattle fed diets varying in forage content. The database was comprised of treatment means of CH 4 production from in vivo beef studies published from 2000 to 2015. Criteria to include data in the database were as follows: animal description, intakes, diet composition and CH 4 production. In all, 54 published equations that predict CH 4 production from diet composition were evaluated. Precision and accuracy of the equations were evaluated using the concordance correlation coefficient (r c ), root mean square prediction error (RMSPE), model efficiency and analysis of errors. Equations were ranked using a combined index of the various statistical assessments based on principal component analysis. The final database contained 53 studies and 207 treatment means that were divided into two data sets: diets containing ⩾400 g/kg dry matter (DM) forage (n = 116) and diets containing ⩽200 g/kg DM forage (n = 42). Diets containing between ⩽400 and ⩾200 g/kg DM forage were not included in the analysis because of their limited numbers (n = 6). Outliers, treatment means where feed was fed restrictively and diets with CH 4 mitigation additives were omitted (n = 43). Using the high-forage dataset the best-fit equations were the International Panel on Climate Change Tier 2 method, 3 equations for steers that considered gross energy intake (GEI) and body weight and an equation that considered dry matter intake and starch:neutral detergent fiber with r c ranging from 0.60 to 0.73 and RMSPE from 35.6 to 45.9 g/day. For the high-grain diets, the 5 best-fit equations considered intakes of metabolisable energy, cellulose, hemicellulose and fat, or for steers GEI and body weight, with r c ranging from 0.35 to 0.52 and RMSPE from 47.4 to 62.9 g/day. Ranking of extant CH 4 prediction equations for their accuracy and precision differed with forage content of the diet. When used for cattle fed high-grain diets, extant CH 4 prediction models were generally imprecise and lacked accuracy.

Haematobia irritans is an obligate bloodsucking ectoparasite of cattle and is the global major pest of livestock production. Currently, H. irritans management is largely dependent upon broad-spectrum pesticides, which lately has led to the development of insecticide resistance. Thus, alternative control methods are necessary. Endophyte-infected grasses have been studied as an alternative due to their capability to biosynthesize alkaloids associated with anti-insect activities. Thus, the main aim of this study was to evaluate the antifeedant and repellent activity of lolines obtained from endophyte-infected tall fescue against H. irritans adults in laboratory conditions. The alkaloid extract (ALKE) was obtained by acid–base extraction. N-formyl loline (NFL) and N-acetyl loline (NAL) were isolated by preparative thin layer chromatography (pTLC) and column chromatography (CC), and the loline was prepared by acid hydrolysis of a NFL/NAL mixture. Loline identification was performed by gas chromatography coupled to mass spectrometry (GC/MS). Feeding behavior was evaluated by a non-choice test, and olfactory response was evaluated using a Y-tube olfactometer. Accordingly, all samples showed antifeedant activities. NFL was the most antifeedant compound at 0.5 µg/µL and 1.0 µg/µL, and it was statistically equal to NAL but different to loline; however, NAL was not statistically different to loline. NFL and NAL at 0.25 µg/µL were more active than loline. All samples except loline exhibited spatial repellency in the olfactometer. Thus, the little or non-adverse effects for cattle and beneficial activities of those lolines make them suitable candidates for horn fly management.

Universally applicable empirical equations specific for high-and low-forage diets were developed to improve the prediction of enteric methane production (eCH 4) from beef cattle. A database built using treatment means from published beef studies conducted in numerous countries was divided into two datasets: high-forage diet [≥40% forage dry matter (DM), n = 123] and low-forage diet (≤20% forage DM, n = 34). Monte-Carlo techniques were used to overcome the limited numbers of observations in each dataset, and multiple regression analysis and cross validation were used to develop new eCH 4 prediction equations. Precision, accuracy, and analysis of errors were evaluated using concordance correlation (r c) and root mean square prediction error (RMSPE). The best-fit equations for high and low forage content included the following variables: body weight (kg) and intakes (kg d −1) of DM, fat, neutral detergent fiber (NDF), acid detergent fiber, crude protein to NDF ratio, and starch to NDF ratio. For high and low forages, best-fit equations had r c ≥ 0.70 and RMSPE ≤ 40 g eCH 4 d −1 and r c ≥ 0.90 and RMSPE ≤ 15 g eCH 4 d −1 , respectively. Use of equations specific to dietary forage proportion reduced the uncertainty of estimating beef cattle eCH 4 emission compared with the Intergovernmental Panel on Climate Change Tier 2 methodology.

Haematobia irritans is a cosmopolitan obligate blood-feeding ectoparasite of cattle and is the major global pest of livestock production. Currently, H. irritans management is largely dependent on broad-spectrum pesticides, which has led to the development of insecticide resistance. Thus, alternative control methods are needed. Essential oils have been studied as an alternative due to their wide spectrum of biological activities against insects. Thus, the main aim of this study was to evaluate the insecticidal, repellent and antifeedant activity of the essential oils from Blepharocalyx cruckshanksii leaves and Pilgerodendron uviferum heartwood against horn flies in laboratory conditions. The composition of the essential oils was analyzed using gas chromatography coupled to mass spectrometry. Accordingly, α-pinene (36.50%) and limonene (20.50%) were the principal components of the B. cruckchanksii essential oil, and δ-cadinol (24.16%), cubenol (22.64%), 15-copaenol (15.46%) and δ-cadinene (10.81%) were the most abundant compounds in the P. uviferum essential oil. Mortality of flies and feeding behavior were evaluated by non-choice tests, and olfactory response was evaluated using a Y-tube olfactometer. Both essential oils were toxic to horn flies, with LC50 values for B. cruckchanksii essential oil of 3.58 µL L−1 air at 4 h, and for P. uviferum essential oil of 9.41 µL L−1 air and 1.02 µL L−1 air at 1 and 4 h, respectively. Moreover, the essential oils exhibited spatial repellency in the olfactometer using only 10 µg of each oil, and these significantly reduced the horn fly feeding at all doses evaluated. Although further laboratory and field studies related to the insectistatic and insecticide properties of these essential oils against H. irritans are necessary, B. cruckshanksii leaves and P. uviferum heartwood essential oils are promising candidates for horn fly management.

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