Residual feed intake phenotype and gender affect the expression of key genes of the lipogenesis pathway in subcutaneous adipose tissue of beef cattle

Background: Feed accounts for up to 75% of costs in beef production systems,thus any improvement in feed efficiency(FE) will benefit the profitability of this enterprise.Residual feed intake(RFI) is a measure of FE that is independent of level of production.Adipose tissue(AT) is a major endocrine organ and the primary metabolic energy reservoir.It modulates a variety of processes related to FE such as lipid metabolism and glucose homeostasis and thus measures of inter-animal variation in adiposity are frequently included in the calculation of the RFI index.The aim of this study was to determine the effect of phenotypic RFI status and gender on the expression of key candidate genes related to processes involved in energy metabolism within AT.Dry matter intake(DMI) and average daily gain(ADG) were measured over a period of 70 d for 52 purebred Simmental heifers(n = 24) and bulls(n = 28) with an initial BW±SD of 372±39.6 kg and 387±50.6 kg,respectively.Residual feed intake was calculated and animals were ranked within gender by RFI into high(inefficient; n = 9 heifers and n = 8 bulls)and low(efficient; n = 9 heifers and n = 8 bulls) groups.Results: Average daily gain ±SD and daily DMI ±SD for heifers and bul s were 1.2±0.4 kg and 9.1±0.5 kg,and 1.8±0.3 kg and 9.5±1 kg respectively.High RFI heifers and bulls consumed 10% and 15% more(P < 0.05) than their low RFI counterparts,respectively.Heifers had a higher expression of all genes measured than bulls(P < 0.05).A gender × RFI interaction was detected for HMGCS2(P < 0.05) in which high RFI bulls tended to have lower expression of HMGCS2 than low RFI bulls(P < 0.1),whereas high RFI heifers had higher expression than low RFI heifers(P < 0.05) and high RFI bulls(P < 0.05).SLC2 A4 expression was consistently higher in subcutaneous AT of low RFI animals across gender.Conclusion: The findings of this study indicate that low RFI cattle exhibit upregulation of the molecular mechanisms governing glucose metabolism in adipose tissue,in particular,glucose clearance.The decreased expression of SLC2 A4 in the inefficient cattle may result in less efficient glucose metabolism in these animals.We conclude that SLC2 A4 may be a potential biomarker for RFI in cattle.

Effect of supplementation with n-3 polyunsaturated fatty acids and/or β-glucans on performance, feeding behaviour and immune status of Holstein Friesian bull calves during the pre-and post-weaning periods

Background: Previous research in both calves and other species has suggested n-3 polyunsaturated fatty acids(PUFA) and β-glucans may have positive effects on immune function. This experiment measured performance,behaviour, metabolite and immunological responses to pre-weaning supplementation of dairy bull calves with n-3 PUFA in the form of fish oil and β-glucans derived from seaweed extract. 44 Holstein Friesian bull calves, aged 13.7± 2.5 d and weighing 48.0 ± 5.8 kg were artificially reared using an electronic feeding system. Each calf was offered5 L(120 g/L) per day of milk replacer(MR) and assigned to one of four treatments included in the MR,(1) Control(CON);(2) 40 g n-3 PUFA per day(FO);(3) 1 g β-glucans per day(GL) and(4) 40 g n-3 PUFA per day & 1 g/d β-glucans(FOGL) in a 2 × 2 factorial design. Milk replacer and concentrate was offered from d 0–62(pre-weaning),while concentrate provision continued for a further 31 d post-weaning period. Individual daily feed intake and feeding behaviour was recorded throughout, while bodyweight and blood analyte data were collected at regular intervals.Results: Overall mean concentrate DMI from d 0–93 was 1.39, 1.27, 1.00 and 0.72 kg/d for CON, FO, GL and FOGL calves, respectively(SEM = 0.037;P < 0.0001). Calves supplemented with GL were significantly lighter(P < 0.0001) at both weaning(d 62) and turnout to pasture(d 93) than un-supplemented calves, with a similar effect(P < 0.0001)evident for calves receiving FO compared to un-supplemented contemporaries. Supplementation with GL reduced the number of unrewarded visits where milk was not consumed(P < 0.0001) while supplementation with FO increased mean drinking speed(P < 0.0001). Supplementation with GL resulted in greater concentrations of haptoglobin(P = 0.034), greater serum osmolality(P = 0.021) and lower lymphocyte levels(P = 0.027). In addition,cells from GL supplemented calves exhibited a lower response than un-supplemented contemporaries to both Phytohaemagglutinin A stimulated IFN-γ(P = 0.019) and Concanavalin A stimulated IFN-γ(P = 0.012) following in vitro challenges.Conclusions: Pre-weaning supplementation of bull calves with either n-3 PUFA or β-glucan resulted in reduced voluntary feed intake of concentrate and consequently poorer pre-weaning calf performance. There was no evidence for any beneficial effect of either supplementation strategy on calves’ immune responses.

Stress and immunological response of heifers divergently ranked for residual feed intake following an adrenocorticotropic hormone challenge

Background： When an animal is exposed to a stressor, metabolic rate, energy consumption and utilisation increase primarily through activation of the hypothalamic-pituitary-adrenal（HPA） axis. Changes to partitioning of energy by an animal are likely to influence the efficiency with which it is utilised. Therefore, this study aimed to determine the physiological stress response to an exogenous adrenocorticotropic hormone（ACTH） challenge in beef heifers divergently ranked on phenotypic residual feed intake（RFI）.Results： Data were collected on 34 Simmental weaning beef heifers the progeny of a well characterized and divergently bred RFI suckler beef herd. Residual feed intake was determined on each animal during the postweaning stage over a 91-day feed intake measurement period during which they were individually offered adlibitum grass silage and 2 kg of concentrate per head once daily. The 12 highest [0.34 kg DM/d] and 12 lowest[-0.48 kg DM/d] ranking animals on RFI were selected for use in this study. For the physiological stress challenge heifers（mean age 605 ± 13 d; mean BW 518 ± 31.4 kg） were fitted aseptically with indwelling jugular catheters to facilitate intensive blood collection. The response of the adrenal cortex to a standardised dose of ACTH（1.98 IU/kg metabolic BW^（0.75）） was examined. Serial blood samples were analysed for plasma cortisol, ACTH and haematology variables. Heifers differing in RFI did not differ（P = 0.59） in ACTH concentrations. Concentration of ACTH peaked（P 〈 0.001） in both RFI groups at 20 min post-ACTH administration, following which concentration declined to baseline levels by 150 min. Similarly, cortisol systemic profile peaked at 60 min and concentrations remained continuously elevated for 150 min. A RFI × time interaction was detected for cortisol concentrations（P = 0.06） with high RFI heifers had a greater cortisol response than Low RFI from 40 min to 150 min relative to ACTH administration. Cortisol response was positively associated with RFI status（r = 0.32; P 〈 0.01）. No effect of RFI was evident for neutrophil, lymphocytes, monocyte, eosinophils and basophil count. Plasma red blood cell number（6.07 vs. 6.23; P = 0.02） and hematocrit percentage（23.2 vs. 24.5; P = 0.02） were greater for low than high RFI animals.Conclusions： Evidence is provided that feed efficiency is associated with HPA axis function and susceptibility to stress, and responsiveness of the HPA axis is likely to contribute to appreciable variation in the efficiency feed utilisation of cattle.

Examination of the molecular control of ruminal epithelial function in response to dietary restriction and subsequent compensatory growth in cattle

Background： The objective of this study was to investigate the effect of dietary restriction and subsequent compensatory growth on the relative expression of genes involved in volatile fatty acid transport, metabolism and cell proliferation in ruminal epithelial tissue of beef cattle. Sixty Holstein Friesian bulls（mean liveweight 370 ± 35 kg;mean age 479 ± 15 d） were assigned to one of two groups：（i） restricted feed allowance（RES; n = 30） for 125 d（Period 1） followed by ad libitum access to feed for 55 d（Period 2） or（ii） ad libitum access to feed throughout（ADLIB; n = 30）. Target growth rate for RES was 0.6 kg/d during Period 1. At the end of each dietary period, 15 animals from each treatment group were slaughtered and ruminal epithelial tissue and liquid digesta harvested from the ventral sac of the rumen. Real-time q PCR was used to quantify m RNA transcripts of 26 genes associated with ruminal epithelial function. Volatile fatty acid analysis of rumen fluid from individual animals was conducted using gas chromatography.Results： Diet × period interactions were evident for genes involved in ketogenesis（BDH2, P = 0.017）, pyruvate metabolism（LDHa, P = 0.048; PDHA1, P = 0.015） and cellular transport and structure（DSG1, P = 0.019; CACT, P = 0.027）. Ruminal concentrations of propionic acid（P = 0.018） and n-valeric acid（P = 0.029） were lower in RES animals, compared with ADLIB, throughout the experiment. There was also a strong tendency（P = 0.064）toward a diet × period interaction for n-butyric with higher concentrations in RES animals, compared with ADLIB, during Period 1.Conclusions： These data suggest that following nutrient restriction, the structural integrity of the rumen wall is compromised and there is upregulation of genes involved in the production of ketone bodies and breakdown of pyruvate for cellular energy. These results provide an insight into the potential molecular mechanisms regulating ruminal epithelial absorptive metabolism and growth following nutrient restriction and subsequent compensatory growth.

Application of a simplified ADM1 for full-scale anaerobic co-digestion of cattle slurry and grass silage:assessment of input variability

Mathematical modeling of anaerobic digestion is a powerful tool to predict gas yields and optimize the process.The Anaerobic Digestion Model No.1(ADM1)is a widely implemented model for this purpose.However,modeling full-scale biogas plants is challenging due to the extensive substrate and parameter characterization required.This study describes the modification of the ADM1 through a simplification of individual process phases,characteristic components and required parameters.Consequently,the ability of the simplified model to simulate the co-digestion of grass silage and cattle slurry was evaluated using data from a full-scale biogas plant.The impacts of substrate composition(crude carbohydrate,protein and lipid concentration)and variability of carbohydrate degradability on simulation results were assessed to identify the most influential parameters.Results indicated that the simplified version was able to depict biogas and biomethane production with average model efficiencies,according to the Nash-Sutcliffe efficiency(NSE)coefficient,of 0.70 and 0.67,respectively,and was comparable to the original ADM1(average model efficiencies of 0.71 and 0.63,respectively).The variability of crude carbohydrate,protein and lipid concentration did not significantly impact biogas and biomethane output for the data sets explored.In contrast,carbohydrate degradability seemed to explain much more of the variability in the biogas and methane production.Thus,the application of simplified models provides a reliable basis for the process simulation and optimization of full-scale agricultural biogas plants.

Quantitative analysis of ruminal methanogenic microbial populations in beef cattle divergent in phenotypic residual feed intake(RFI)offered contrasting diets

Background：Methane（CH_4） emissions in cattle are an undesirable end product of rumen methanogenic fermentative activity as they are associated not only with negative environmental impacts but also with reduced host feed efficiency.The aim of this study was to quantify total and specific rumen microbial methanogenic populations in beef cattle divergently selected for residual feed intake（RFI） while offered（i） a low energy high forage（HF） diet followed by（ii） a high energy low forage（LF） diet.Ruminal fluid was collected from 14 high（H）and 14 low（L） RFI animals across both dietary periods.Quantitative real time PCR（qRT-PCR） analysis was conducted to quantify the abundance of total and specific rumen methanogenic microbes.Spearman correlation analysis was used to investigate the association between the relative abundance of methanogens and animal performance,rumen fermentation variables and diet digestibility.Results：Abundance of methanogens,did not differ between RFI phenotypes.However,relative abundance of total and specific methanogen species was affected（P〈 0.05） by diet type,with greater abundance observed while animals were offered the LF compared to the HF diet.Conclusions：These findings suggest that differences in abundance of specific rumen methanogen species may not contribute to variation in CH_4 emissions between efficient and inefficient animals,however dietary manipulation can influence the abundance of total and specific methanogen species.

Effect of genotype on duodenal expression of nutrient transporter genes in dairy cows

Background： Studies have shown clear differences between dairy breeds in their feed intake and production efficiencies. The duodenum is critical in the coordination of digestion and absorption of nutrients. This study examined gene transcript abundance of important classes of nutrient transporters in the duodenum of non lactating dairy cows of different feed efficiency potential, namely Holstein-Friesian （HF）, Jersey （JE） and their F1 hybrid. Duodenal epithelial tissue was collected at slaughter and stored at -80℃. Total RNA was extracted from tissue and reverse transcribed to generate cDNA. Gene expression of the following transporters, namely nucleoside amino acid; sugar; mineral; and lipid transporters was measured using quantitative real-time RT-PCR. Data were statistically analysed using mixed models ANOVA in SAS. Orthogonal contrasts were used to test for potential heterotic effects and spearman correlation coefficients calculated to determine potential associations amongst gen, expression values and production efficiency variables. Results： While there were no direct effects of genotype on expression values for any of the genes examined, there was evidence for a heterotic effect （P 〈 0.05） on ABCGS, in the form of increased expression in the F1 genotype compared to either of the two parent breeds. Additionally, a tendency for increased expression of the amino acid transporters, SLC3A1 （P= 0.072）, SLC3A2 （P= 0.081） and SLC6A 14 （P= 0.072） was also evident in the F1 genotype. A negative （P 〈 0.05） association was identified between the expression of the glucose transporter gene SLCSA1 and total lactational milk solids yield, corrected for body weight. Positive correlations （P 〈 0.05） were also observed between the expression values of genes involved in common transporter roles. Conclusion： This study suggests that differences in the expression of sterol and amino acid transporters in the duodenum could contribute towards the documented differences in feed efficiency between HF, JE and their F1 hybrid. Furthermore, positive associations between the expression of genes involved in common transporter roles suggest that these may be co-regulated. The study identifies potential candidates for investigation of genetic variants regulating nutrient transport and absorption in the duodenum in dairy cows, which may be incorporated into future breeding programmes.

Process stability and microbial community composition in pig manure and food waste anaerobic co-digesters operated at low HRTs

这研究估计了猪粪肥和食物浪费的从 21 天把水力的保留时间(HRT ) 归结为厌氧地共同消化的 10.5 天的效果。3.75 L 的连续地搅动的坦克反应堆工作体积被操作在在 42 瑮 ? 湡 ? 潭畤楬眠牥 ?潣灭瑵摥愠摮愠慮祬敺 d

Localization of urea transporter B in the developing bovine rumen

Urea nitrogen secreted from blood to rumen is a crucial factor shaping the symbiotic relationship between host ruminants and their microbial populations.Passage of urea across rumen epithelia is facilitated by urea transporter B(UT-B),but the long-term regulation of these proteins remains unclear.As ruminal function develops over a period of months,the developing rumen is an excellent model with which to investigate this regulation.Using rumen epithelium samples of calves from birth to 96 d of age,this study performed immunolocalization studies to localize and semi-quantify UT-B protein development.As expected,preliminary experiments confirmed that ruminal monocarboxylate transporter 1(MCT1)short chain fatty acid transporter protein abundance increased with age(P<0.01,n=4).Further investigation revealed that ruminal UT-B was present in the first few weeks of life and initially detected in the basolateral membrane of stratum basale cells.Over the next 2 months,UT-B staining spread to other epithelial layers and semi-quantification indicated that UT-B abundance significantly increased with age(P<0.01,n=4 or 6).These changes were in line with the development of rumen function after the advent of solid feed intake and weaning,exhibiting a similar pattern to both MCT1 transporters and papillae growth.This study therefore confirmed age-dependent changes of in situ ruminal UT-B protein,adding to our understanding of the long-term regulation of ruminal urea transporters.