What makes a host profitable? Parasites balance host nutritive resources against immunity

Numerous host qualities can modulate parasite fitness, and among these, host nutritive resources and immunity are of prime importance. Indeed, parasite fitness increases with the amount of nutritive resources extracted from the host body and decreases with host immune response. To maximize fitness, parasites have therefore to balance these two host components. Yet, because host nutritive resources and immunity both increase with host body condition, it is unclear whether parasites perform better on hosts in prime, intermediate, or poor condition. We investigated blood meal size and survival of the ectoparasitic louse fly Crataerina melbae in relation to body condition and cutaneous immune response of their Alpine swift (Apus melba) nestling hosts. Louse flies took a smaller blood meal and lived a shorter period of time when feeding on nestlings that were experimentally food deprived or had their cutaneous immune response boosted with methionine. Consistent with these results, louse fly survival was the highest when feeding on nonexperimental nestlings in intermediate body condition. Our findings emphasize that although hosts in poor condition had a reduced immunocompetence, parasites may have avoided them because individuals in poor condition did not provide adequate resources. These findings highlight the fact that giving host immunocompetence primary consideration can result in a biased appraisal of host-parasite interactions

Tense and Aspect Constructions Among Arabic L1 Learners of English

With English as an increasingly common second language for native Arabic speakers, there is a growing need for scholarly attention to the language transfer patterns among this group of English language learners. This thesis aims to assess commonly recurring errors in one area of language, tense and aspect construction, in order to contribute to the existing literature on tense and aspect production among Arabic learners of English and to analyze whether language transfer can serve as a plausible explanation for these patterns. Drawing on a sample of 93 student essays produced by native Arabic speakers (included in the appendix) and bostered by an analysis of tense-aspect construction in the Arabic language, this research builds on previous studies of commonly occurring errors as well as presents new observations on errors patterns. Significantly, this research found copula deletion to occur before noun phrases, prepositional phrases, and adjective phrases alike. Also, this study documents challenges students faced in correctly forming progressive aspect verbs, as well as speculating about potential causes and remedies for this phenomenon. Furthermore, a preliminary investigation into unnatural tense shifts within and between clauses among this group of students was included. Where possible, descriptions and analyses of these errors have been followed with pedagogical suggestions

The Intelligibility of the Onset Cluster [pl] and the Coda Cluster [ƞz] in Arabic-Accented English

This paper analyzes two specific instances of English consonant-cluster production among native Arabic speakers of English. We analyze the onset cluster /pl/ and the coda cluster /ŋz/. These clusters are of interest because the first segment in each cluster does not exist in Arabic but the second is shared by both Arabic and English. Five Arabic-speaking subjects were selected based on a number of shared features, including a shared city of origin, beginning their acquisition of English after the critical period, and having spent no more than one year in an English-speaking environment at the time of the recordings. The findings give us the opportunity to assess the participants’ pronunciations of these clusters in light of the two syllable phonotactic constraints: Sonority Sequencing Principle (SSP) and the Minimal Sonority Distance Parameter (MSDP). Other issues investigated have to do with the segmental transfer hierarchy and ranking

Effect of Pen Cleaning Frequency and Feeding Distillers Grains and Wheat Straw on Nutrient Mass Balance and Performance of Feedlot Steers

Two experiments, calves fed November to May (WINTER) and yearlings fed May to September (SUMMER), were conducted to evaluate the effects of feeding a high level of wet distillers grains plus soluble (WDGS) and wheat straw or a corn control diet (CON) on average daily gain (ADG), feed-to-gain (F:G), manure nitrogen (N), and N losses. In both experiments, the CON treatment had greater dry matter intake(DMI), ADG hot carcass weight (HCW), marbling and fat depth. There was greater N intake and N excretion for both the WINTER and SUMMER experiments on the WDGS. However, for the WINTER experiment there was no difference in the amount of N in the manure due to diet or pen cleaning frequency. In the SUMMER experiment, cleaning pens monthly almost doubled dry matter (DM), organic matter (OM), and N removed in manure. There was a tendency for the WDGS treatment to have greater N loss than the control treatment in the WINTER experiment and a significant increase in N losses for the WDGS treatment in the SUMMER experiment, despite the greater amount of manure N removed

Composting of Feedlot Waste-Update of Research Activities

Composting of feedlot manure is an alternative waste management system that is environmentally sound, provides flexibility in application as a nutrient source, and is economically feasible

The Effects of Supplementing Wet Distillers Grains Mixed With Wheat Straw to Growing Steers

A growing study compared feeding wet distillers grains, dried distillers grains, and a mix of 66% wet distillers grains and 33% wheat straw as supplements to a forage-based diet. Steers were supplemented 0, 2, 4, or 6 lb distillers grains/head daily. Wet distillers grains and dried distillers grains produced higher final body weight and dry matter intake compared to the mix. Increasing levels of distillers grains increased performance in forage based diets and wet grains mixed with straw reduced forage intake

Effects of Ingestion and Collection Bag Type on Nutrient Composition of Forage Samples from Esophageally Fistulated Cattle

Ingestion and mastication of forage samples adds ash. Generally, levels of CP were lower and NDF and IVOMD were similar for post-ingested versus pre-ingestedforage. Bag type (screen vs. solid) generally did not affect ash, NDF, or IVOMD. Bag did not affect CP of alfalfabut CP of grass samples from screen bags was lower than solid bags. More fresh than dry forage was recovered through the esophageal opening

Effects of Dried Distillers Grains and Equivalent Undegradable Intake Protein or Ether Extract on Performance and Forage Intake of Heifers Grazing Smooth Bromegrass Pastures

Crossbred heifers (n = 120; BW = 368 kg, SD = 39 kg) were used to determine effects of dried distillers grains (DDG) and relative contributions of undegradable intake protein (UIP) and fat (ether extract, EE) in DDG on ADG and forage intake (FI). Heifers rotationally grazed six 3.5-ha, smooth bromegrass paddocks (IVDMD = 65.7%, CP = 20.8%, UIP = 2.17%, DM basis). Heifers were blocked by previous ADG and allotted to treatments in a 3 × 3 + 1 factorial design. Factors were source and level of supplementation. Supplements were as follows: 1) DDG (UIP = 15.8%, EE = 9.67%), 2) corn gluten meal (CGM; UIP = 31.6%, EE = 0.83%), or 3) corn oil (OIL; UIP = 0.74%, EE = 19.3%). Amounts of DDG were 750, 1,500, or 2,250 g/d, whereas amounts of CGM and OIL were 375, 750, or 1,125 g/ d. Supplements containing CGM and OIL were fed in amounts that provided UIP and EE, respectively, equivalent to those of the DDG. Contrasts of interest were DDG vs. CGM and DDG vs. OIL. Control heifers were fed 250 g/d of a supplement containing corn bran and molasses (UIP = 0.92%, EE = 1.13%). Heifers were supplemented individually. Treatments were separated by regressing the response variables on grams of nutrient (DM, UIP, or EE) intake per kilogram of BW, because not all heifers consumed their allotment of supplement. Supplemental DDG resulted in a linear increase in ADG (P \u3c 0.01), whereas CGM tended to increase ADG (P = 0.14) but at a rate that was 39% of that for DDG, representing a response to MP. Supplementation of OIL did not affect ADG (P = 0.25) and tended to result in ADG less than that of DDG (P = 0.09). Supplementation with DDG had no effect (P = 0.63) on FI when predicted by the use of chromic oxide but tended (P = 0.07) to decrease FI when it was predicted from ADG using NE equations. Despite the differences between methods in the significance of the effect of DDG, the rates of substitution agreed (−0.50 and −0.45 for chromic oxide and NE equations, respectively), suggesting that the chromic oxide method was less sensitive in assessing FI. Supplementation with CGM decreased FI (P \u3c 0.01), but FI for CGM did not differ from that of DDG when the chromic oxide method was used (P = 0.19). Corn oil had no effect on FI (P = 0.42). Increased ADG and decreased FI observed from DDG supplementation is not independently explained by UIP or EE contained in DDG

The Effects of Supplementing Wet Distillers Grains Mixed With Wheat Straw to Growing Steers

A growing study compared feeding wet distillers grains, dried distillers grains, and a mix of 66% wet distillers grains and 33% wheat straw as supplements to a forage-based diet. Steers were supplemented 0, 2, 4, or 6 lb distillers grains/head daily. Wet distillers grains and dried distillers grains produced higher final body weight and dry matter intake compared to the mix. Increasing levels of distillers grains increased performance in forage based diets and wet grains mixed with straw reduced forage intake