Factors controlling nutrient availability to the developing fetus in ruminants

Inadequate delivery of nutrients results in intrauterine growth restriction (IUGR), which is a leading cause of neonatal morbidity and mortality in livestock. In ruminants, inadequate nutrition during pregnancy is often prevalent due to frequent utilization of exensive forage based grazing systems, making them highly susceptible to changes in nutrient quality and availability. Delivery of nutrients to the fetus is dependent on a number of critical factors including placental growth and development, utero-placental blood flow, nutrient availability, and placental metabolism and transport capacity. Previous findings from our laboratory and others, highlight essential roles for amino acids and their metabolites in supporting normal fetal growth and development, as well as the critical role for amino acid transporters in nutrient delivery to the fetus. The focus of this review will be on the role of maternal nutrition on placental form and function as a regulator of fetal development in ruminants.     

Maternal selenium supplementation and timing of nutrient restriction in pregnant sheep: Impacts on nutrient availability to the fetus

To determine the effects of maternal Se intake and plane of nutrition during mid or late gestation or both on AA concentrations and metabolite concentrations in the dam and fetus, pregnant ewe lambs (n = 64) were assigned to 1 of 8 treatments arranged in a 2 × 2 × 2 factorial array: Se level [initiated at breeding; adequate (ASe; 3.05 μg/kg of BW) or high (HSe; 70.4 μg/kg of BW)] and nutritional level [100% (control; CON) or 60% (restricted; RES) of NRC recommendations] fed at different times of gestation [d 50 to 90 (mid) or d 91 to 132 (late)]. A blood sample was obtained from each ewe and fetus on d 132 of gestation and used to measure circulating concentrations of glucose, NEFA, blood urea N, and AA. The late RES ewes and their fetuses had less (P ≤ 0.03) circulating glucose compared with late CON ewes and fetuses at d 132; however, no effect (P ≥ 0.14) of diet on the fetal:maternal glucose concentration ratio was observed. Late RES ewes had a smaller (P = 0.01) fetal:maternal NEFA ratio compared with late CON ewes. Ewes fed ASe had a greater (P = 0.01) fetal:maternal blood urea N ratio compared with HSe ewes. Fetal:maternal ratios of total circulating AA, total essential AA, and total nonessential AA were each affected (P ≤ 0.03) by the combination of Se treatment and late gestation nutritional level.     

Mechanisms controlling feed intake in ruminants: a review

The purpose of this paper is to review our understanding of the involvement of central and peripheral factors in the control of feed intake in ruminants. The regulation of body weight under various states of energy need depends on an animal's ability to control feed intake to meet these needs. In the central nervous system (CNS), the ventromedial and lateral hypothalamus appear to be the areas involved in satiety and hunger, respectively; other important areas are the paraventricular nucleus and rostral brain areas. Intracerebroventricular injection of neurotransmitters, alpha- and beta-adrenergic agonists, 5-hydroxytryptamine and gamma aminobutyric acid (GABA) agonists, has stimulated feeding in ruminants; intravenous administration of benzodiazepines stimulated feed intake in sheep and cattle, possibly by increasing GABA levels in the brain. Neuropeptides of the opioid and cholecystokinin families have reciprocal hunger-stimulating and satiety-eliciting effects when administered centrally in sheep. Further, concentrations of these neuropeptides in specific areas of the hypothalamus have been shown to change with the state of hunger-satiety of sheep. In the periphery, none of the hormones associated with the pituitary, adrenal gland, pancreas or gastrointestinal tract has been shown to have significant effects on the control of feed intake. In addition, the physical properties of the ingested feed in the gastrointestinal tract, while possibly influencing the rate or pattern of feeding, do not appear to be primary factors in the control of feed intake under many feeding conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interactions between mild nutrient imbalance and taste preferences in young ruminants

Thirty-two crossbred lambs (BW = 31.2 ± 4.7 kg; 16 females, 16 males) housed in individual pens were used to investigate the relationship between nutrient supply and taste preferences in ruminants. Experiment 1 determined whether an imbalanced CP supply would alter preferences for feeds containing flavors designed to elicit either umami (U) or a mixture (1/3:1/3:1/3) of umami, sweet, and bitter (M) tastes. Lambs were randomly allocated to either a low (LP; 10.9% CP) or a high (HP; 20.4% CP) CP diet for 21 d. Afterward, lambs were presented during 21 d with a choice of the same LP or HP diet unflavored (LPC or HPC, respectively) or flavored (0.1% as fed) with U (LPU or HPU, respectively) or M (LPM or HPM). Experiment 2 determined the influence of CP status on preference for dietary CP, bitter taste, and sweet taste elicited by sucrose or a noncaloric sweetener. In test 1, sixteen lambs previously fed LP or HP for 42 d in Exp. 1 could choose between the HP and LP diets. In test 2, the remaining 16 lambs from Exp. 1 were offered a choice between unflavored LP or HP diets or the same diets flavored (0.066% as fed) with a bitter flavor. In test 3, the 16 lambs from test 1 were offered a choice between an unflavored diet (LP or HP) and the same diet flavored with sucrose (0.2%) or a noncaloric sweetener (0.066%). In Exp. 1, when offered a choice, all lambs showed a preference (P < 0.05) for the unflavored diet except for LP lambs, who clearly preferred (P < 0.05) LPU (72% of total DMI) over LPC. However, preference for LPU progressively decreased (P < 0.05) as time of exposure to the choice increased. In Exp. 2 (test 1), lambs previously fed LP progressively increased (P < 0.05) total DMI when presented with LP and HP, whereas consumption was constant for lambs previously fed HP and offered a choice of LP and HP diets. At the onset of test 2, lambs fed LP progressively reduced (P < 0.05) preference for the bitter flavor from 53 to 34%. In test 3, lambs previously fed LP diets consumed less (P < 0.05) sweetener- than sucrose-supplemented diet, whereas lambs previously offered HP diets consumed more sweetener- than sucrose-supplemented diet. In summary, protein-restricted lambs were able to differentiate and increase consumption of U-flavored feeds. However, this increase disappeared over time. These results indicate that lambs are able to sense dietary CP content and modulate short-term consumption of flavored feeds based on their nutrient requirements.     

影响反刍动物硒、铜生物利用率的因素

日粮中微量元素的生物利用率(bioavailability)及其影响因素在反刍动物与非反刍动物间差别很大。通常，反刍动物日粮中纤维含量高，其中大部分经瘤胃微生物发酵而被消化。但是，微量元素和饲料中的纤维络合及和消化道中未消化完全的纤维粘附影响了其在反刍动物体内的生物利用率。并且，饲料中也存在多种拮抗物质干扰了它的吸收代谢。另外，在弱酸性(pH6．0～6．8)的瘤胃环境中多种微量元素及形成的金属络合物以不溶形式存在。硒、铜是反刍动物机体内多种酶的组成成分，但其吸收代谢受诸多因素影响。本文简要分析硒、铜为反刍动物利用的影响因素，并比较了它们的无机形式和有机形式在生物利用率匕的差异。     

Factors influencing magnesium absorption and metabolism in ruminants

Magnesium is a nutrient required for all animals, but it is especially critical for ruminants. A physiological deficiency of Mg results in hypomagnesemic tetany. Typically, only female ruminants are affected, and the disturbance usually occurs during the early stages of lactation. Magnesium functions at three biochemical levels, as a cofactor at the enzymatic level, at the structural level in assembly of ribosomes, and at the whole cell level as a stabilizing force in membranes. Parathyroid hormone (PTH) can affect Mg metabolism by decreasing urinary Mg excretion and stimulating bone resorption, thus releasing Mg into the extracellular fluid. Renal excretion of Mg and Mg absorption from the gastrointestinal tract both are increased by 1,25-dihydroxyvitamin D3. A number of dietary factors depress Mg absorption in ruminants. Of these, high dietary K has the greatest and most consistent effect. Feeding substantial quantities of readily digested carbohydrates increases Mg absorption, but the mode of action is not clear. High concentrations of Al in forage sometimes are associated with a high incidence of grass tetany, but this effect does not appear to be related to Mg absorption. Interrelationships of Al with Mg, Ca, P and PTH are implicated.     

Factors affecting methane production and mitigation in ruminants

Methane (CH₄) is the second most important greenhouse gas (GHG) and that emitted from enteric fermentation in livestock is the single largest source of emissions in Japan. Many factors influence ruminant CH₄ production, including level of intake, type and quality of feeds and environmental temperature. The objectives of this review are to identify the factors affecting CH₄ production in ruminants, to examine technologies for the mitigation of CH₄ emissions from ruminants, and to identify areas requiring further research. The following equation for CH₄ prediction was formulated using only dry matter intake (DMI) and has been adopted in Japan to estimate emissions from ruminant livestock for the National GHG Inventory Report: Y = −17.766 + 42.793X − 0.849X², where Y is CH₄ production (L/day) and X is DMI (kg/day). Technologies for the mitigation of CH₄ emissions from ruminants include increasing productivity by improving nutritional management, the manipulation of ruminal fermentation by changing feed composition, the addition of CH₄ inhibitors, and defaunation. Considering the importance of ruminant livestock, it is essential to establish economically feasible ways of reducing ruminant CH₄ production while improving productivity; it is therefore critical to conduct a full system analysis to select the best combination of approaches or new technologies to be applied under long-term field conditions.     

Developments and hurdles in generating vaccines for controlling helminth parasites of grazing ruminants

As a direct consequence of rising drug resistance among common nematodes of grazing animals, efforts toward state-of-the-art vaccine development have clearly intensified in recent years, fuelled primarily by the advent of newer technologies in gene discovery, by advancements in antigen identification, characterisation and production. In this regard, it is appropriate to review progress that has been made in generating helminth vaccines and in particular, vaccines against common nematodes of production animals for consumption. In like manner, it is prudent to evaluate barriers that have hindered progress in the past and continue to present obstacles that must be solved when utilizing and depending on host immunity to attenuate parasitic infections.     

A comparison of two integrated approaches of controlling nematode parasites in small ruminants

Control of gastrointestinal nematodes (GIN) in small ruminants in regions of the world where anthelmintic resistance is prevalent must rely on more than just chemical deworming strategies. The objective of this experiment was to compare two integrated treatment protocols for control of GIN (primarily Haemonchus contortus in this region) using anthelmintics, copper oxide wire particles (COWP) and FAMACHA(?), compared to traditional anthelmintic use only. Three separate trials were conducted on mature ewes, weaned goats, and weaned lambs in which three deworming management strategies were applied: 1) all animals were dewormed with levamisole at four week intervals (LEV), 2) individual animals were dewormed with moxidectin when scored≥4 (ewes) or ≥3 (kids and lambs) using FAMACHA(?) (FAM/MOX), 3) all animals were dewormed with moxidectin initially and again with COWP (2g) when group mean FEC exceeded 500 (ewes), 3000 (kids), or 1000 (lambs) eggs/g (MOX/COWP). In this final group, during periods between group treatments, individual animals were dewormed with albendazole and levamisole according to FAMACHA(?) score. Fecal egg counts (FEC) and blood packed cell volume (PCV) were determined every 7 days and body weight every 28 days for 30, 20, or 16 weeks in ewes, goats, and lambs, respectively. Efficacy of levamisole was 83.4-86.4%, efficacy of moxidectin was 93.5-100%, and efficacy of COWP was 10.8-98.1% among the three trials. The mean number of deworming treatments per animal that occurred for the LEV, FAM/MOX, and MOX/COWP groups, respectively, was 7.9, 0.6, and 2.5±0.4 (P<0.001) for ewes, 5.2, 1.6, and 3.4±0.3 (P<0.001) for goats, and 4.0, 1.7, and 3.6±0.2 (P<0.001) for lambs. Production (body weight of lambs weaned from ewes or final body weight of kids and lambs) was similar among management strategy groups for ewes and kids, but FAM/MOX lambs were lighter by the end of the trial (P<0.003). While more time and labor was required to use the FAMACHA(?) system, a more conservative use of anthelmintics occurred in the FAM/MOX group.     

蒸汽压片对玉米在肉仔鸡的养分生物学效价的影响

本试验旨在研究蒸汽压片对玉米在肉仔鸡的养分生物学效价的改善作用。选96只21日龄AA肉仔鸡,按体重均匀分成4组,每组6个重复,每个重复4只鸡,采用全收粪法进行代谢试验,测定蒸汽压片玉米和粉碎玉米在淀粉消化率、干物质消化率、氮存留率、代谢能以及氨基酸利用率上的差异。试验结果表明,蒸汽压片能够显著改善玉米常规养分利用率、代谢能值及氨基酸利用率;应用蒸汽压片玉米配制日粮还可以显著减少肉仔鸡粪便及其中氮的排泄量,减轻环境污染。     

Rearing conditions influence nutrient availability of plant extracts supplemented diets when fed to broiler chickens

The effects of a standardised mixture of essential oils, including 5% carvacrol, 3% cinnamaldehyde and 2% capsicum (XT 6930; Pancosma S.A), on dietary apparent metabolisable energy corrected for nitrogen retention (AMEn), nutrient digestibility and mucin secretions, measured as sialic acid (SA) were investigated in broilers fed on the same diet but reared under different conditions, that is, cages and floor pens littered with wood shavings used in previous broiler study. The use of XT reduced (p < 0.05) nitrogen digestibility (0.585 vs. 0.544) and tended (p = 0.072) to reduce dry matter digestibility (0.733 vs. 0.717) of the diet when fed to birds reared in cages. However, XT supplementation improved (p < 0.05) fat digestibility (0.844 vs. 0.862) and tended (p = 0.093) to increase AMEn (14.01 vs. 14.25 MJ/kg DM) of the same diet when fed to broilers reared in floor pens. Essential oils supplementation tended (p = 0.059) to increase the secretion of SA, when fed to birds reared in cages (11.24 vs. 14.18 μg), but did not influence (p > 0.05) the SA secretion from birds reared in floor pens. The results obtained from the cage study tend to be the opposite of those obtained from the floor pen study. This suggests that the efficiency of dietary plant extracts may be influenced by the rearing/hygienic conditions of poultry. Based on the overall results, it can be concluded that information on rearing conditions should be taken into account for more complete interpretation of the experimental data emanating from experiments involving use of essential oils typified by those considered in this study.     

热应激对反刍动物营养物质消化、瘤胃发酵、甲烷生成的影响及缓解热应激的措施

热应激是影响动物生产的重要因素.正常的瘤胃功能是反刍动物健康生产的重要保证.了解热应激对瘤胃功能的影响,有利于针对性地采取营养措施缓解热应激造成的对反刍动物的不利影响.文章主要综述热应激对反刍动物营养物质消化、瘤胃发酵、甲烷生成的影响及缓解热应激的措施.     

Estimation of the relative biological availability of inorganic selenium sources for ruminants using tissue uptake of selenium

An experiment was conducted to estimate the relative bioavailability of inorganic Se sources based on tissue Se deposition following supplementation at high dietary levels. Twenty-eight crossbred wethers averaging 50 kg initial weight were assigned randomly to seven treatments that were fed for 10 d. The basal diet contained .18 mg/kg Se (DM basis). Dietary Se was added at 0, 3, 6 or 9 mg/kg as reagent grade sodium selenite (Na2SeO3) and 6 mg/kg from either calcium selenite (CaSeO3), Na2SeO3 + fumed amorphous carrier or sodium selenate (Na2SeO4). There were four sheep per treatment group, housed in individual, raised pens with slatted floors. Daily feed intake was restricted to 1,200 g and tap water was available ad libitum. The basal diet was fed for a 10-d adjustment period, then sheep were fed experimental diets for 10 d. At the termination of the experiment, blood samples were taken; sheep were stunned and killed, and livers and kidneys were removed and frozen for Se analysis. There was a linear (P less than .001) uptake of Se in liver, kidney and serum. The CaSeO3 and Na2SeO4 sources resulted in greater (P less than .05) Se concentrations in liver and kidney than did Na2SeO3, but these differences were not significant when the analyzed dietary Se concentrations were used as a covariate in the statistical model. Based on linear and multiple linear regression slopes and average increases in serum, liver and kidney Se concentrations, estimated relative bioavailability values corrected for analyzed dietary concentration, were 100, 101, 90 and 133 for Na2SeO3, CaSeO3, Na2SeO3 + carrier and Na2SeO4, respectively.     

Blood flow and steroid and nutrient uptake of the gravid uterus and fetus of sows

Uterine and umbilical blood samples and blood flow (BF) measurements were obtained from one uterine horn and a single fetus of sows at d 70, 90 and 110 of gestation. Concentrations of O2 in blood and of estrogen (E), progesterone (P), glucose, alpha-amino nitrogen (N) and urea N in plasma were determined. Fetal weights were .267 +/- .018, .633 +/- .019 and 1.208 +/- .073 kg on d 70, 90 and 110, respectively. Uterine and umbilical BF remained constant with day of gestation, averaging 1.51 +/- .06 and .31 +/- .02 liters/min. Uptake of P by a uterine horn and fetus remained constant, but secretion of E by a uterine horn and uptake of E by a fetus increased (P less than .05) with stage of gestation. Uterine and fetal uptake of O2, glucose and alpha-amino N did not change and uptake of O2, glucose and alpha-amino N per kg fetus decreased (P less than .01) as gestation advanced. Secretion of urea N from the uterus was observed, with a concentration gradient from the fetal to the uterine circulations. Uterine and fetal respiratory quotients for glucose were .79 and .38, respectively. Thus, although glucose potentially served as a major energy source, a large portion of the energy requirements of the fetal pig were met by catabolism of other substrates. The decrease in umbilical BF and uptake of nutrients per kg fetus with day of gestation suggested that porcine fetal metabolism declined as pregnancy advanced.     

不同光照和褪黑激素对獭兔生产性能和营养物质利用率的影响

选取4月龄体重相近的健康獭兔96只随机分成12组,每组8只,采用3×4随机区组试验设计,研究不同光照和褪黑激素对獭兔生产性能和营养物质利用率的影响。结果表明:①不同光照及褪黑激素对獭兔平均日增重均有显著(P<0.05)或极显著(P<0.01)影响,光照与褪黑激素对獭兔平均日增重存在显著互作效应(P<0.05);②不同光照对獭兔粗蛋白消化率、粗脂肪消化率无显著影响(P>0.05),褪黑激素对獭兔粗蛋白消化率、粗脂肪消化率有极显著影响(P<0.01),光照与褪黑激素对獭兔粗蛋白消化率存在显著互作效应(P<0.05);③不同光照对獭兔血清GH无显著影响(P>0.05),褪黑激素对獭兔血清GH有极显著影响(P<0.01),光照与褪黑激素对獭兔血清GH存在显著互作效应(P<0.05);不同光照及褪黑激素对獭兔血清TP均有显著影响(P<0.05),光照与褪黑激素对獭兔血清TP无显著互作效应(P>0.05);不同光照对獭兔血清BUN无显著影响(P>0.05),褪黑激素对獭兔血清BUN有显著影响(P<0.05),光照与褪黑激素对獭兔血清BUN无显著互作效应(P>0.05)。本研究结果显示,褪黑激素能提高獭兔生产性能和各种营养物质的消化率,建议在獭兔生产中采取自然光照条件下饲喂36 mg/只褪黑激素。