Multiple country and breed genomic prediction of tick resistance in beef cattle

Ticks cause substantial production losses for beef and dairy cattle. Cattle resistance to ticks is one of the most important factors affecting tick control, but largely neglected due to the challenge of phenotyping. In this study, we evaluate the pooling of tick resistance phenotyped reference populations from multi-country beef cattle breeds to assess the possibility of improving host resistance through multi-trait genomic selection. Data consisted of tick counts or scores assessing the number of female ticks at least 4.5 mm length and derived from seven populations, with breed, country, number of records and genotyped/phenotyped animals being respectively: Angus (AN), Brazil, 2,263, 921/1,156, Hereford (HH), Brazil, 6,615, 1,910/2,802, Brangus (BN), Brazil, 2,441, 851/851, Braford (BO), Brazil, 9,523, 3,062/4,095, Tropical Composite (TC), Australia, 229, 229/229, Brahman (BR), Australia, 675, 675/675, and Nguni (NG), South Africa, 490, 490/490. All populations were genotyped using medium density Illumina SNP BeadChips and imputed to a common high-density panel of 332,468 markers. The mean linkage disequilibrium (LD) between adjacent SNPs varied from 0.24 to 0.37 across populations and so was sufficient to allow genomic breeding values (GEBV) prediction. Correlations of LD phase between breeds were higher between composites and their founder breeds (0.81 to 0.95) and lower between NG and the other breeds (0.27 and 0.35). There was wide range of estimated heritability (0.05 and 0.42) and genetic correlation (-0.01 and 0.87) for tick resistance across the studied populations, with the largest genetic correlation observed between BN and BO. Predictive ability was improved under the old-young validation for three of the seven populations using a multi-trait approach compared to a single trait within-population prediction, while whole and partial data GEBV correlations increased in all cases, with relative improvements ranging from 3% for BO to 64% for TC. Moreover, the multi-trait analysis was useful to correct typical over-dispersion of the GEBV. Results from this study indicate that a joint genomic evaluation of AN, HH, BN, BO and BR can be readily implemented to improve tick resistance of these populations using selection on GEBV. For NG and TC additional phenotyping will be required to obtain accurate GEBV

Pupas de Chrysomya megacephala (Fabricius, 1794) (Diptera, Calliphoridae) crioconservadas em soluções de glicerol e dimetil sulfóxido como substrato de criação de Nasonia vitripennis (Walker, 1836) (Hymenoptera, Pteromalidae)

Substances glycerol and dimethyl sulfoxide (DMSO) were evaluated as cryoprotective in the storage of the Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae) pupae at low temperatures. It were investigated five concentrations (0.1, 1, 2, 3 and 4 mol.) at -20 oC (freezer) and –196 oC (fase liquid of the liquid nitrogen- LN). Control groups were constituted by non-frozen pupae (fresh) and pupae freezing only with phosfate buffer saline (PBS). Information was obtained about the reproductive performance of Nasonia vitripennis(Walker, 1836) matrices reared on these pupae. These analyses revealed rates of parasitoidism efficiency lower than 3 % at glycerol NL (3 and 4 mol) and DMSO Freezer (0.1, 2, 3 and 4 mol). There were not emergence in the frozen pupae belong to DMSO NL and glycerol NL – PBS; 0.1, 1 and 2 mol. The freezing with glycerol at – 20 oC showed better rates of parasitoidism efficiency than others groups. Methods used in this work with cryoprotectivesglycerol and DMSO were ineffective in the cryopreservation of C. megacephala pupae when compared with others works. The influency of biotics and non-biotics facts were discussed

Desempenho reprodutivo de Nasonia vitripennis Walker (Hymenoptera: Pteromalidae) em pupas crioconservadas de Chrysomya megacephala Fabricius (Diptera: Calliphoridae): avaliação preliminar Reproductive performance of Nasonia vitripennis Walker (Hymenoptera: Pteromalidae) on Chrysomya megacephala Fabricius (Diptera: Calliphoridae) cryopreserved pupae: preliminary evaluation

Avaliou-se o desempenho reprodutivo de Nasonia vitripennis Walker (Hymenoptera: Pteromalidae) em pupas de Chrysomya megacephala Fabricius (Diptera: Calliphoridae) previamente armazenadas a - 20ºC de temperatura, durante 77 dias, com e sem passagem prévia em nitrogênio líquido (NL) por um, três e 15 minutos. O grupo controle foi caracterizado por pupas hospedeiras frescas. Os muscóides foram expostos aos parasitóides durante 72 horas. Utilizou-se a relação de uma pupa muscóide por fêmea parasitóide. A amostra de pupas frescas permitiu a emergência de 15 parasitóides/ pupa, em média, enquanto 10 parasitóides / pupa emergiram dos espécimens prévia e diretamente armazenados em freezer (-20ºC). Observou-se um acentuado decréscimo do desempenho reprodutivo dos microhimenópteros que exploraram os substratos previamente submetidos ao NL durante um, três e 15 minutos (<img border=0 id="_x0000_i1026" src="../../../../img/revistas/cr/v34n1/n1a32fr01.gif">: 6,1; 5,5 e 5,7, respectivamente). A dissecação das pupas hospedeiras revelou um expressivo número de pteromalídeos imaturos, nas amostras que foram expostas ao NL, e de adultos faratos, em todos os tratamentos<br>The reproductive performance of Nasonia vitripennis Walker (Hymenoptera: Pteromalidae) was evaluated on pupae of Chrysomya megacephala Fabricius (Diptera: Calliphoridae) kept at -20ºC, during 77 days, with and no previous passage for liquid nitrogen (NL) by one, three and 15 minutes. Control groups were characterized for fresh pupae hosts. There was one pupa for each parasitoid. The sample of fresh pupae exhibited average of 15 emergent parasitoids / pupa while pupae stored directly at freezer (-20ºC) presented an average of 10 emergent parasitoids / pupa. In the samples exposed at one, three and 15 minutes in NL, accentuated decrease was observed on emergent hymenopterans reproductive performance (<img border=0 id="_x0000_i1028" src="../../../../img/revistas/cr/v34n1/n1a32fr01.gif">: 6.1; 5.5 and 5.7 respectively). The dissection of pupae revealed a large number of immature pteromalid in the groups with liquid nitrogen passage and farate adults in all the groups