Periconception and first trimester diet modifies appetite, hypothalamic gene expression, and carcass traits in bulls

Nulliparous yearling beef heifers (n=360) were used to evaluate the effects of maternal dietary protein during the periconception and first trimester periods of gestation on postnatal growth, feedlot performance, carcass characteristics, and the expression of genes associated with appetite in the arcuate nucleus of their male progeny. Heifers were individually fed a diet of 1.18g crude protein (CP)/day High protein (HPeri) or 0.62g CP/day Low protein (LPeri) beginning 60days before conception. From 24 to 98days post-conception (dpc), half of each treatment group changed to the alternative post-conception diet and were fed 1.49g CP/day (HPost) or 0.88g CP/day (LPost) yielding four treatment groups in a 2×2 factorial design. From day 98 of gestation, heifers received a common diet until parturition. Calves were weaned at 183days and developed on pasture before feedlot entry. Bulls underwent a 70-day Residual Feed Intake (RFI) feedlot test commencing at 528days of age. Feedlot entry and final body weight (BW), feedlot average daily gain (ADG) and RFI were not different (p>0.05). Progeny of dams that had a change in diet (LPeri/HPost and HPeri/LPost) had 9% higher daily dry matter intake (DMI) during the RFI test (p<0.05) than progeny of dams that received low diet throughout both the peri-conception period and first trimester (LPeri/LPost). Further, mRNA expression of the appetite-stimulating agouti-related protein (AGRP) was increased in the arcuate nucleus of High Peri/LPost bulls (p<0.05). Longissimus dorsi muscle cross sectional area, carcass dressing percentage, and estimated retail beef yield (RBY) were all higher (p<0.05), and rump (P8) fat tended to be lower (p=0.07), for bulls from HPost dams despite no difference in carcass weight (p<0.05). This study is of commercial importance to the livestock industry as specific periods of maternal dietary supplementation may increase feed intake, enhance progeny muscling, and alter fat deposition leading to improvement in efficiency of meat production in beef cattle.Katrina J. Copping, Matthew J. Callaghan, Geert H. Geesink, Jessica R. Gugusheff, I. Caroline McMillen, Raymond J. Rodgers, Beverly S. Muhlhausler, Mini A. Vithayathil and Viv E. A. Perr

Experimental nitrogen addition alters structure and function of a boreal poor fen: Implications for critical loads

Bogs and fens cover 6 and 21%, respectively, of the 140,329 km2 Oil Sands Administrative Area in northern Alberta. Regional background atmospheric N deposition is low (b2 kg N ha−1 yr−1 ), but oil sands development has led to increasing N deposition (as high as 17 kg N ha−1 yr−1 ). To examine responses to N deposition, over five years, we experimentally applied N (as NH4NO3) to a poor fen near Mariana Lake, Alberta, unaffected by oil sands activities, at rates of 0, 5, 10, 15, 20, and 25 kg N ha−1 yr−1 , plus controls (no water or N addition). At Mariana Lake Poor Fen (MLPF), increasing N addition: 1) progressively inhibited N2-fixation; 2) had no effect on net primary production (NPP) of Sphagnum fuscum or S. angustifolium, while stimulating S. magellanicum NPP; 3) led to decreased abundance of S. fuscum and increased abundance of S. angustifolium, S. magellanicum, Andromeda polifolia, Vaccinium oxycoccos, and of vascular plants in general; 4) led to an increase in stem N concentrations in S. angustifolium and S. magellanicum, and an increase in leaf N concentrations in Chamaedaphne calyculata, Andromeda polifolia, and Vaccinium oxycoccos; 5) stimulated root biomass and production;6) stimulated decomposition of cellulose, but not of Sphagnum or vascular plant litter; and 7) had no or minimal effects on net N mineralization in surface peat, NH4 +-N, NO3 −-N or DON concentrations in surface porewater, or peat microbial composition. Increasing N addition led to a switch from new N inputs being taken up primarily by Sphagnum to being taken up primarily by shrubs. MLPF responses to increasing N addition did not exhibit threshold triggers, but rather began as soon as N additions increased. Considering all responses to N addition, we recommend a critical load for poor fens in Alberta of 3 kg N ha−1 yr−1

Spatial autocorrelation or model misspecification? The help from RESET and the curse of small samples

In regression analysis, model misspecification can produce spurious spatial correlation in the residuals. By means of Monte Carlo simulations, I show that the RESET test can help to disentangle this conundrum in large samples. Small samples can pose a serious challenge to finding the correct model

Responses of rat substantia nigra dopamine-containing neurones to (–)-HA-966 in vitro

1. Extracellular single unit recording techniques were used to compare the effects of (-)-3-amino-1-hydroxypyrrolidin-2-one ((–)-HA-966) and (±)-baclofen on the activity of dopamine-containing neurones in 300 μm slices of rat substantia nigra. Electrophysiological data were compared with the outcome of in vitro binding experiments designed to assess the affinity of (–)-HA-966 for γ-aminobutyric acid (GABA(B)) receptors. 2. Bath application of (–)-HA-966 produced a concentration-dependent inhibition of dopaminergic neuronal firing (EC(50)=444.0 μM; 95% confidence interval: 277.6 μM–710.1 μM, n=27) which was fully reversible upon washout from the recording chamber. Although similar effects were observed in response to (±)-baclofen, the direct-acting GABA(B) receptor agonist proved to be considerably more potent than (–)-HA-966 (EC(50)=0.54 μM; 95% confidence interval: 0.44 μM–0.66 μM, n=29) in vitro. 3. Low concentrations of chloral hydrate (10 μM) were without effect on the basal firing rate of nigral dopaminergic neurones but significantly increased the inhibitory effects produced by concomitant application of (–)-HA-966. 4. The inhibitory effects of (–)-HA-966 were completely reversed in the presence of the GABA(B) receptor antagonists, CGP-35348 (100 μM) and 2-hydroxysaclofen (500 μM). Bath application of CGP-35348 alone increased basal firing rate. However, the magnitude of the excitation (9.2±0.3%) was not sufficient to account for the ability of the antagonist to reverse fully the inhibitory effects of (–)-HA-966. 5. (–)-HA-966 (0.1–1.0 mM) produced a concentration-dependent displacement of [(†)H]-GABA from synaptic membranes in the presence of isoguvacine (40 μM). However, the affinity of the drug for GABA(B) binding sites was significantly less than that of GABA (0.0005 potency ratio) and showed no apparent stereoselectivity. 6. These results indicate that while (–)-HA-966 appears to act as a direct GABA(B) receptor agonist in vitro, its affinity for this receptor site is substantially less than that of GABA or baclofen and unlikely to account for the depressant actions of this drug which occur at levels approximately ten fold lower in vivo