Microbial respiration and substrate weight loss—I: A general model of the influences of abiotic variables

A general model of the influences of abiotic variables on microbial respiration and substrate weight loss is presented. The model, a complex hypothesis relating microbial respiration to temperature. moisture, O₂ and substrate, “explains” 71–96% of the variation in aerobic respiration rates measured from a variety of natural substrates. The model can project seasonal patterns of weight loss and thus permits evaluation of laboratory respirometry against field measures using litter bags. Using data from several countries simulated losses due to microbial respiration are 70–90% of the measured litter bag loss.     

Prediction of retail product and trimmable fat yields from the four primal cuts in beef cattle using ultrasound or carcass data

The most widely used system to predict percentage of retail product from the four primal cuts of beef is USDA yield grade. The purpose of this study was to determine whether routine ultrasound measurements and additional rump measurements could be used in place of the carcass measurements used in the USDA yield grade equation to more accurately predict the percentage of saleable product from the four primals. This study used market cattle (n = 466) consisting of Angus bulls, Angus steers, and crossbred steers. Live animal ultrasound measures collected within 7 d of slaughter were 1) scan weight (SCANWT); 2) 12th- to 13th-rib s.c. fat thickness (UFAT); 3) 12th- to 13th-rib LM area (ULMA); 4) s.c. fat thickness over the termination of the biceps femoris in the rump (URFAT; reference point); 5) depth of gluteus medius under the reference point (URDEPTH); and 6) area of gluteus medius anterior to the reference point (URAREA). Traditional carcass measures collected included 1) HCW; 2) 12th-to 13th-rib s.c. fat thickness (CFAT); 3) 12th- to 13th-rib LM area (CLMA); and 4) estimated percentage of kidney, pelvic, and heart fat (CKPH). Right sides of carcasses were fabricated into subprimal cuts, lean trim, fat, and bone. Weights of each component were recorded, and percentage of retail product from the four primals was expressed as a percentage of side weight. A stepwise regression was performed using data from cattle (n = 328) to develop models to predict percentage of retail product from the four primals based on carcass measures or ultrasound measures, and comparisons were made between the models. The most accurate carcass prediction equation included CFAT, CKPH, and CLMA (R2 = 0.308), whereas the most accurate live prediction equation included UFAT, ULMA, SCANWT, and URAREA (R2 = 0.454). When these equations were applied to a validation set of cattle (n = 138), the carcass equation showed R2 = 0.350, whereas the ultrasound data showed R2 = 0.460. Ultrasound measures in the live animal were potentially more accurate predictors of retail product than measures collected on the carcass.     

Improving accuracy of genomic prediction in Brangus cattle by adding animals with imputed low‐density SNP genotypes

Reliable genomic prediction of breeding values for quantitative traits requires the availability of sufficient number of animals with genotypes and phenotypes in the training set. As of 31 October 2016, there were 3,797 Brangus animals with genotypes and phenotypes. These Brangus animals were genotyped using different commercial SNP chips. Of them, the largest group consisted of 1,535 animals genotyped by the GGP‐LDV4 SNP chip. The remaining 2,262 genotypes were imputed to the SNP content of the GGP‐LDV4 chip, so that the number of animals available for training the genomic prediction models was more than doubled. The present study showed that the pooling of animals with both original or imputed 40K SNP genotypes substantially increased genomic prediction accuracies on the ten traits. By supplementing imputed genotypes, the relative gains in genomic prediction accuracies on estimated breeding values (EBV) were from 12.60% to 31.27%, and the relative gain in genomic prediction accuracies on de‐regressed EBV was slightly small (i.e. 0.87%–18.75%). The present study also compared the performance of five genomic prediction models and two cross‐validation methods. The five genomic models predicted EBV and de‐regressed EBV of the ten traits similarly well. Of the two cross‐validation methods, leave‐one‐out cross‐validation maximized the number of animals at the stage of training for genomic prediction. Genomic prediction accuracy (GPA) on the ten quantitative traits was validated in 1,106 newly genotyped Brangus animals based on the SNP effects estimated in the previous set of 3,797 Brangus animals, and they were slightly lower than GPA in the original data. The present study was the first to leverage currently available genotype and phenotype resources in order to harness genomic prediction in Brangus beef cattle.     

Analysis of factors affecting the availability of air bubbles to subsurface drip irrigation emitters during oxygation

In this study, we sought to define system features that impact air delivery in subsurface drip irrigation systems. A 58 % decrease in emitter cross-sectional area caused a 71 % reduction in the water flow rate, but the 37 % decrease in emitter air flow rate was statistically non-significant. For emitters with symmetric connectors, delivery of air from the emitters depended on the length of the connector relative to the air layer flowing at the top of the pipe. Emitters with asymmetric connectors yielded greater air flow rates compared to those with symmetric connectors, a result ascribed to a low-pressure region at the tip of asymmetric connectors. When symmetric connectors were used, an increase in pipe diameter was directly related to an increase in the uniformity of emitter air flow rate distribution expressed by the Christiansen uniformity coefficient (CUC), and inversely related to the efficiency of air bubble delivery and mean emitter air flow rate. In contrast, when asymmetric connectors were used, an increase in pipe diameter was associated with a decrease in CUC, and an increase in the efficiency of air bubble delivery and mean emitter air flow rate.     

Vaccination of calves with an attenuated cell line of Theileria annulata and the sporozoite antigen SPAG-1 produces a synergistic effect

The sporozoite surface antigen, SPAG-1 and the attenuated schizont infected Tunisian line CL1 of Theileria annulata have been shown, in previous studies, to induce variable levels of protection against homologous and heterologous sporozoite challenge, respectively. We report here the result of a vaccination trial comparing the protection level induced by the SPAG-1 antigen (as a recombinant full length His tagged protein) and the attenuated cell line, used singly or in combination. The results, after challenge of immunised calves with a lethal dose of sporozoites, show that SPAG-1 provides limited protection (one out of seven calves surviving), while the attenuated cell line provides moderate protection (three out of seven calves recovered). The combination of SPAG-1 and the attenuated cell line induced the best protection as indicated by the survival of all the vaccinated calves. These results, together with a range of parasitological and clinical parameters, demonstrate the enhanced protection provided by combining sporozoite and schizont antigens in vaccination against tropical theileriosis.     

Reproduction, gamete supply and larval rearing of New Zealand turbot Colistium nudipinnis (Waite 1910) and brill Colistium guntheri (Hutton 1873): a potential new aquaculture species

New Zealand turbot Colistium nudipinnis (Waite 1910) and brill Colistium guntheri (Hutton 1873) were studied to assess their potential for aquaculture development. The reproductive cycle of wild fish showed a long spawning season from winter to summer, during which it is possible to obtain gametes. Both species have a diurnal ovulatory cycle, and gamete collection, by stripping and fertilizing at sea, was most successful within 2–3 h before and after sunset. Male reproductive anatomy suggests that these flatfish spawn in close proximity and that pair formation is highly likely. The eggs of both species have multiple oil droplets, turbot eggs being slightly larger (0.99 mm diameter) with more droplets (18–55) than brill eggs (0.97 mm, 13–26 droplets). Hatching occurred approximately 84 h after fertilization at 14 °C. Newly hatched turbot averaged 2.2 mm in length, and brill averaged 2.1 mm. First feeding began 4 days post-hatch (DPH). During larval rearing, rotifers were replaced by Artemia nauplii at 10 DPH. Metamorphosis commenced at 12–15 DPH and was completed and the larvae settled by 45 DPH. Weaning to inert foods began at 20–22 DPH (50 mg weight) and was completed by 57 DPH. Survival of turbot was 22.8% from fertilized egg to hatching, 7.3% through incubation to 22 DPH and 2.1% through incubation to fully weaned juveniles. Weaning success for turbot from metamorphosis to 57 DPH was 31.5%.