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PubMed1992

Impact of nutrition on pancreatic exocrine and endocrine secretion in ruminants: a review.

Because of the unique features of the ruminant digestive system, variations in diet composition and intake produce dramatic changes in ruminal fermentation. Optimizing nutritional management requires an understanding of how these variations and changes influence digestion and metabolism. Although the pancreas plays a central role in digestion and subsequent nutrient metabolism, relatively little is known about pancreatic adaptation to nutritional changes in the ruminant. Increasing starch intake has been suggested to increase pancreatic alpha-amylase; however, recent work suggests that dietary energy per se may drive these changes, and interactions with other nutrients, such as protein, may exist. Studies describing the influence of altered protein and lipid intakes on pancreatic adaptation in ruminants are lacking. Pancreatic secretion of both insulin and glucagon respond to the intravenous infusion of VFA in a dramatic fashion; however, feeding studies suggest that the influence of VFA on insulin and glucagon may be more subtle. Interactions exist between stimulatory signals and physiological state, such as lactation. Assessment of pancreatic endocrine secretion is further complicated by a variable removal of insulin and glucagon by hepatic tissues. These studies point out that pancreatic hormone secretion is controlled by integrated and complex mechanisms. Studies of these controlling mechanisms should consider the entire array to more fully understand hormone secretion.

Animal Nutritional Physiological Phenomena↗
PubMed1992

Ruminant placental lactogens: structure and biology.

Ruminant placental lactogens (PL) are members of the somatotropin, prolactin gene family that are synthesized by trophectodermal binucleate cells. The structure and biology of PL has been studied in the cow, sheep, and goat. Ruminant PL have greater structural identity to prolactin than somatotropin, although they bind to both lactogenic and somatogenic receptors. The molecular weights of ovine and caprine PL are approximately 23,000, whereas bovine PL is larger (31,000 to 34,000) due to glycosylation. Placental lactogen is secreted into both the fetal and maternal circulations. The concentration of PL in the fetus decreases with advancing gestation, whereas PL concentration peaks in the maternal circulation during the last third of pregnancy then reaches a plateau. Furthermore, the maternal concentration of PL is 100- to 1,000-fold higher in sheep and goats than in cows. The precise factors that modulate secretion of PL are unknown, although placental mass and nutrition seem to play a role. Ruminant PL have both lactogenic and somatogenic biological activities and may also have unique activities mediated through a specific receptor. There is circumstantial evidence to suggest that PL plays a role in stimulating mammogenesis. Placental lactogen secreted into the fetal compartment may also help regulate fetal growth. Direct experimental data indicate that PL can regulate maternal intermediary metabolism. Thus, it may act as a partitioning agent to regulate nutrient supply for fetal growth. The precise biological function of PL in ruminants, therefore, still needs to be defined.

Amino Acid Sequence↗
PubMed1996

Integration of regulatory signals controlling forage intake in ruminants.

Numerous factors have the potential to affect the amount of forage or pasture eaten by ruminant animals, including gut capacity, ability of tissues to metabolize nutrients, ruminal acidity, and osmolality. Much research into the control of food intake has tested one particular theory, often by applying greater degrees of stimulation than occur naturally, and is then unable to explain how physiological changes in that stimulus can be responsible for controlling intake. We have found that the effects of two or three stimuli (sodium acetate, sodium propionate, ruminal distension) applied together were additive. As to the site of this integration, receptors in the rumen wall are sensitive to both mechanical stimulation and acids, with transmission of impulses in vagal afferent fibers probably modulated by the osmolality of ruminal fluid. Thus, a certain degree of integration ("polymodal") is likely to have occurred at the level of the transceiving organ. A second level of integration is "polytopic." In this level stimulation of one visceral site modifies the effects of the same type of stimulus at another site. A third level of integration occurs in the central nervous system, whereby the effects of visceral stimulation might be balanced with signals from other stimuli (e.g., the special senses) to determine whether feeding should take place at any given moment. The thesis presented is that the central nervous system receives a nonspecific signal from the viscera; the animal might then learn to eat that amount of food that minimizes the competing discomforts of excessive abdominal visceral stimulation and shortage or imbalance of nutrients.

Animals↗
PubMed1996

Modeling ruminant feed intake with protein, chemostatic, and distention feedbacks.

Little progress has been made in modeling intake regulation in spite of the many mechanisms identified as important. A model with relatively simple inputs was developed that included compartments for protein, soluble carbohydrate, digestible fiber, and very slowly digesting fiber. Distention and chemostatic feedbacks were combined using a previously published equation. The ratio of current ruminal fill to a modulating parameter for ruminal fill represented distention feedback. The ratio of the current flow of available energy to a modulating parameter for chemostatic demand represented chemostatic feedback. The modulating parameter for ruminal fill was based on literature reports of ruminal contents. Intake was adjusted based on current fill and energy flow relative to modulating parameters for fill and chemostatic feedback. The effect of the digestible organic matter (DOM) to CP ratio on DOM intake was modeled to adjust rates of digestion, rates of passage, and the chemostatic feedback. The model tested an integrated concept of intake regulation with only CP, IVDMD, and NDF as inputs. In spite of relatively simple inputs, the model behavior in response to variation in protein, digestibility, and fiber was similar to observations of animal responses.

Animals↗
PubMed1997

Starch utilization by ruminants: from basics to the bunk.

Starch is the major energy component of grains. Wheat contains 77% of DM as starch, corn and sorghum contain 72%, and barley and oats contain 57 to 58%. In vitro systems have provided valuable data on kinetic aspects of starch digestion. Molecular biological techniques have provided a clearer picture of the ruminal microbial milieu. Proportions of starch fermented in the rumen can be predicted satisfactorily for a variety of grains and processing methods. Compared with dry rolling, steam processing (flaking or rolling) increases ruminal digestibility of starch (percentage of intake) from 52 to 78% for sorghum, from 75 to 85% for corn, and six percentage units or less for other grains. Recent research provides new insight into pancreatic function and intestinal glucose transport systems. The capacity to digest starch in the intestine ranges from 45 to 85% of starch entering the duodenum, with that capacity apparently limited by the supply of pancreatic amylase. There is evidence that amylase secretion may be enhanced by increasing duodenal entry of protein. Capacity for active transport of glucose across of gut wall does not seem to limit the amount of starch digested that is absorbed as glucose. For ruminants eating medium- to high-concentrate diets, about 30% of their total glucose need comes from glucose absorption, 50% from organic acid absorption (substrates for hepatic gluconeogenesis), and 20% from other sources. When glucose absorption from the gut increases, ruminants generally adjust (decrease) gluconeogenesis to meet their need; that need is directly linked to DE intake. In terms of overall ME yield, grain starch is best used when it is fermented in the rumen. However, close coordination of protein and starch supply to the duodenum may improve capture of starch in the form of glucose.

Animals↗
PubMed1997

Current perspective on assessing site of digestion in ruminants.

The site of nutrient digestion in the gastrointestinal tract of ruminants affects nutrient availability and the nature of digestive end-products supplied to the host animal. Methods to study site of digestion in vivo provide a tool to obtain data that enhance the ability to interpret or predict animal responses to some feeding practices. Examples are discussed for which site of digestion data provided insights that might not have been evident from other approaches. The use of site of digestion techniques may provide interpretation regarding digestion of N by ruminants different from those derived from measurement of total tract N digestion. Site of digestion measurements have been particularly important in studying effects of heat processing of protein sources and in understanding the nature of digestion of N in high-quality, fresh forages. Moreover, site of digestion techniques have been instrumental in interpreting the influences of supplemental fat sources on ruminal digestion and ruminal biohydrogenation and small intestinal digestion of long-chain fatty acids.

Animals↗
PubMed1998

Standardization of in situ techniques for ruminant feedstuff evaluation.

Over the last two decades, in situ techniques have been used extensively for measuring ruminal degradation of feedstuffs. Current predictive models put renewed emphasis on the need for quantitative information regarding rates and extents of ruminal degradation. However, in situ techniques suffer from tremendous variation, both within and among laboratories. A considerable number of studies have evaluated the influence of various factors on in situ-derived estimates of ruminal degradation. Factors that should be addressed in a standardized procedure include bag and sample sizes; bag material and pore size; sample processing; animal diet, feeding level, and frequency; bag insertion and removal procedures; location of bags within the rumen and containment procedures for the bags; rinsing procedures; microbial correction; incubation times; mathematical models; and numbers of replicate animals, days, and bags required to obtain repeatable estimates of ruminal degradation. Several recommendations that should increase the precision of in situ measurements are presented. Currently, the lack of standardization in rinsing techniques and the failure or inability to correct for microbial contamination of in situ residues seem to be the major sources of variability with in situ procedures.

Animal Feed↗
PubMed1998

Manipulating ruminal fermentation: a microbial ecological perspective.

The essential role of ruminal microflora in ruminant nutrition provides the potential for improvement in animal production via altering the numbers or activities of specific classes of microorganisms. Successful alterations will be facilitated by an understanding of the microbial ecology of the rumen based on its mechanistic underpinnings. Demonstrated improvements in ruminal fermentation can be traced to their consonance with well-established principles of microbial ecology (niche occupancy, selective pressure, adaptation, and interactions) and the thermodynamics and kinetics of substrate utilization. Application of these principles to several proposed alterations of the ruminal bacterial population allows a prediction of their relative feasibility. Improving fiber digestion, decreasing protein degradation, and detoxifying feed components that are present in low concentrations will be difficult to achieve in the rumen and are best approached by altering the feed, either genetically or with postharvest treatment. By contrast, the detoxification of feed components present in high concentration, and redirection of electron disposal away from methanogenesis, are more productive targets for microbiological research.

Animals↗
PubMed1998

Strategies that ruminal bacteria use to handle excess carbohydrate.

When ruminal bacteria have insufficient nitrogen and other nutrients, excess carbohydrate can be toxic. Pure cultures that are nitrogen-limited can convert only some of the excess carbohydrate to intracellular polysaccharide, but this pool can be quickly saturated. Fibrobacter succinogenes cultures that have excess cellobiose secrete glucose and cellotriose into the culture medium, and Prevotella ruminicola produces methylglyoxal, a highly toxic substance that causes a dramatic decrease in viability. Some ruminal bacteria (e.g., Streptococcus bovis and Selenomonas ruminantium) have mechanisms to decrease ATP production or spill the ATP that has already been produced. These mechanisms of decreasing intracellular ATP seem to protect the cell. Most ruminal bacteria can use ammonia as a nitrogen source, but amino nitrogen increases the growth efficiency of mixed ruminal bacteria. Amino nitrogen-dependent improvements in growth efficiency can be explained by an increase in growth rate and a decrease in energy spilling. Amino nitrogen is only beneficial if the rate of carbohydrate fermentation is rapid and carbohydrate is in excess.

Adenosine Triphosphate↗
PubMed2007

Heart rate measurements as an index of energy expenditure and energy balance in ruminants: a review.

A major part of the ME consumed by ruminants (MEI) is dissipated as heat. This fraction, called heat production or energy expenditure (EE), is assayed largely by measuring O2 consumption (VO2). Conventional measurement of EE in controlled conditions in chambers does not reflect the complexity of natural, environmental, and social conditions of free-ranging animals. In mammals, most of the measured VO2 is transferred to the tissues through the heart; therefore, regression of heart rate (HR) against VO2 can be used to estimate the EE of free-ranging animals. The present article reviews the current knowledge on the use of HR for estimating EE. Energy expenditure can be determined from HR measurements, recorded daily over the course of several days, multiplied by the VO2 per beat. When an animal does not perform significant exercise, a constant value of VO2 per beat [O2 pulse (O2P)] measured over a short period (10 to 15 min) is used; during exercise, O2P increases, and the regression equation of VO2 against HR is used. Under extreme heat load, HR increases to improve heat dissipation, and O2P decreases; therefore, the effect of heat load on O2P needs to be taken into account. Cold stress that doubles heat production does not affect O2P. Heart rate and EE are highly correlated with MEI, but there is significant individual variation in the relationship; therefore, the daily change in the HR of individual animals can be used as an indicator of changes in the individual energy status of a ruminant, and the average HR of the group can serve in the estimation of the energy status of the group. When O2P is measured, the average group EE is an indication of the energy balance of the whole group. Because the MEI of nondraft animals is the sum of EE and retained energy (RE), the MEI of free-ranging ruminants can be determined by measurement of EE by the HR method and adding the RE. Similarly, the RE can be determined without slaughtering the animals from measurements of EE and MEI. Soon when devices for automatic HR monitoring of domestic ruminants become available at a reasonable price, continuous monitoring of HR might provide producers with a sensitive tool for identifying changes in the energy status of their animals. This will also significantly help to shorten the time needed to identify health problems of individual animals.

Animals↗
PubMed1986

Starch digestion and utilization in ruminants.

For most grain, except corn and sorghum, 90% or more of starch is normally fermented in the rumen. With corn, up to 30% or more could escape ruminal fermentation; most of the starch escaping fermentation would be digested in the small intestine or fermented in the large intestine. The capacity for digestion of raw starch in the small intestine is limited to 100 to 200 g/d in sheep. Gelled starch could be digested in quantities up to 200 to 300 g/d. The capacity would ultimately be limited by lack of enzymes involved in hydrolysis of short chain di- and oligosaccharides and also by capacity for absorption of glucose. Starch fermented in the cecum leads to an increase of N loss in the feces. In some instances, the high propionic acid proportion arising from fermentation of starch exceeds the capacity of the liver for metabolism. In growing lambs and goats, this creates problems of synthesis of branched-chain fatty acids in adipose tissue and, in dairy cows, problems of low milk yield and milk fat production. The low ruminal pH that often occurs when starchy grain is included in diets for ruminants can cause depression in fiber digestion. Some of these problems can be overcome by reducing extent of cereal processing and other methods that prevent low ruminal pH. It is concluded that due to limited capacity for starch digestion postruminally and high animal variability, deliberate attempts to increase postruminal digestion of starch are unlikely to be beneficial and are likely to create potential digestive problems.

Animal Feed↗
PubMed1988

Comparison of estimates of ruminal protein degradation by in vitro and in situ methods.

Ruminal degradation of eight soluble proteins and 10 protein meals was determined using three methods: 1) an inhibitor in vitro system (IIV), to which inhibitors are added to prevent metabolism of protein degradation products, 2) in situ incubations in nylon bags and 3) in vitro NH3 production in typical ruminal inoculum. In vitro NH3 production rate from different proteins was not related to in situ or IIV degradation rate. Degradation rates for soluble proteins by IIV ranged from .103 to .813/h, yielding estimated extents of degradation that ranged from 73 to 94% (assuming ruminal passage of .05/h). For seven of the protein meals, degradation rates measured by IIV were threefold greater than in situ rates. However, mean degraded fractions estimated from zero-time intercepts were twofold greater using the in situ method, and calculated extents of degradation averaged 83% of IIV values. Extents of degradation estimated (assuming ruminal passage of .05/h) for fish meal, soybean meal, linseed meal, sunflower meal, rapeseed meal, copra meal and meat and bone meal were, respectively; 55, 79, 84, 59, 75, 54 and 58% (IIV) and 46, 63, 69, 51, 52, 43 and 55% (in situ). These values were generally similar to those reported in the literature. The extent of degradation of feather meal was 28% by in situ determination. Neither the IIV nor in situ method gave significant regressions for blood meal; neither method yields reliable data for very slowly degraded proteins. The IIV procedure has the advantage over the in situ method because it can yield degradation estimates for soluble as well as insoluble proteins.

Animals↗
PubMed2006

[Detection of fish DNA in ruminant feed by PCR amplification].

The Japanese Government has prohibited the use of seafood protein, as well as mammalian protein, in ruminant feed. There is an official method to detect meat and bone meal, but no method is yet available to detect fishmeal in ruminant feed. We tried to develop a suitable method to detect fishmeal in ruminant feed, similar to the official method "PCR detection of animal-derived DNA in feed". Our previously reported primers (fishcon5 and fishcon3-1) showed low sensitivity, so we designed new primers based on a DNA sequence from yellowfin tuna mitchondrial DNA. Among the primers, FM5 and FM3 specifically detected fish DNA (sardine, yellowfin tuna, skipjack tuna, chub mackerel, Pacific saury, salmon, rainbow trout, Japanese anchovy, codfish and Japanese horse mackerel) from fish meat, and did not amplify DNA from animals and plants. The sensitivity for detection of the presence of fishmeal in ruminant feed was 0.01-0.001%.

Animal Feed↗
PubMed1999

Comparative patterns of follicle development and selection in ruminants.

Expanding technological capabilities, particularly in ultrasonography and molecular endocrinology, have bridged the gap between form and function of the ovary, and have been a catalyst for intense research activity in this area during the last decade. However, the study of follicular dynamics is still in its infancy in ruminant species other than cattle, and controversy persists regarding the pattern of follicular growth and the existence of follicular dominance. The bovine model of ovarian function is presented as a foundation for concepts surrounding the control of follicular development in ruminants, and to place in context the results of recent studies in sheep, goats, muskoxen, cervids and camelids. This comparative approach is used to determine important generalities that appear to be applicable, as fundamental physiological phenomena, to all ruminant species. Although clear differences in follicular dynamics are evident, differences appear to be specific rather than general, and the following conclusions are consistent with results reported in ruminant species to date: (1) follicles grow in a wave-like fashion; (2) periodic surges in circulating FSH are associated with follicular wave emergence; (3) selection of a dominant follicle involves a decline in FSH and acquisition of LH responsiveness; (4) periodic anovulatory follicular waves continue to emerge until occurrence of an LH surge (that is, at the time of luteolysis during the ovulatory season or during transition from the anovulatory season); (5) within species, there is a positive relationship between the duration of the oestrous cycle and the number of follicular waves; (6) progesterone suppresses LH secretion and growth of the dominant follicle; (7) the duration of the interwave interval is a function of follicular dominance, and is negatively correlated with circulating FSH; (8) follicular dominance in all species is more pronounced during the first and last follicular waves of the oestrous cycle; and (9) pregnancy, the prepubertal period and seasonal anoestrus are characterized by regular, periodic surges in FSH and emergence of anovulatory follicular waves.

Animals↗
PubMed1999

Tick species infesting ruminants in Italy: ecological and bio-climatic factors affecting the different regional distribution.

The distribution of tick species able to infest ruminants in Italy is briefly reviewed on the basis of published records and new data obtained in several surveys carried out mainly in northern Italy. The most frequent and abundant tick species found on ruminants throughout Italy are Ixodes ricinus and Dermacentor marginatus, the first gradually replacing its association with sheep by the association with wild ruminants. Rhipicephalus bursa was mainly found on cattle while R. turanicus, which is considered one of the most sheep-associated species, was found only on wild boar. Haemaphysalis punctata, H. sulcata and H. parva are the other tick species quite frequently found on small ruminants when they are reared on pastures mainly in central-southern Italy. However, the land exploitation of these last decades has dramatically reduced the diversity of Italian environment and significantly modified the distribution and the abundance of ticks causing a heavy spread of the tick species characterized by a strong adaptability such as I. ricinus and R. sanguineus. If this trend continues, it is possible to hypothesise that few "resistant" tick species will gradually replace most of the others. This hypothesis seems to be confirmed by the high percentage observed for I. ricinus (57.4%) and R. sanguineus (35.73%) out of 8,712 specimens collected from several different hosts and from the environment.

Animals↗
PubMed2002

Interferon tau and its immunobiological role in ruminant reproduction.

Interferon tau (IFN-tau) is an key cytokine in maintaining pregnancy in ruminants. It is produced by the ruminant conceptus around the time of implantation. IFN-tau belongs to the type I interferon family but, unlike the other members of this group, it is not virus inducible and its expression is temporal and restricted to the trophoblast cells of the ruminant conceptus. The main target of the paracrine action of this cytokine is the endometrium. It changes the prostaglandin metabolism and secretory function of the cells by upregulating the secretion of several proteins. It also presents immunomodulatory action towards leukocytes by changing their proliferative responses and cytokine production. This cytokine activity in reproductive biology and immunology has been intensively explored for the last ten years. It has been regarded as a potential tool in improving the performance and biotechnological processes in ruminant reproduction. Additionally, its high antiviral potency and low cytotoxicity in comparison with IFN-alpha has placed this cytokine in the group of possible therapeutics in human and animal medicine.

Animals↗
PubMed2003

Indirect enzyme-linked immunosorbent assay for the detection of antibody against Rift Valley fever virus in domestic and wild ruminant sera.

An indirect enzyme-linked immunosorbent assay (I-ELISA) for the detection of specific IgG immunoglobulins against Rift Valley fever virus (RVFV) was validated in-house. A total of 3055 sera from sheep (n = 1159), goats (n = 636), cattle (n = 203), African buffalo (n = 928), and other wild ruminants (n = 129), including eland, kudu, and black wildebeest, was used. Sera from domestic ruminants were collected in West (n = 10), South (n = 1654) and East Africa (n = 334), and sera from wild ruminants (n = 1064) were collected in South Africa. In addition, 136 sera from eight experimentally RVFV-infected sheep, taken during a period of 28 days post infection (dpi), were used to study the kinetics of RVFV antibody production. Field sera were tested by the serum neutralization (VN) test and experimental sera by VN and haemagglutination-inhibition (HI) test. Based on VN test results, negative sera were regarded as reference controls from RVFV-free, and positive sera were regarded as reference controls from RVFV-infected subpopulations of animals. ELISA data were expressed as the percentage positivity (PP) of an internal high positive control. The two-graph receiver operating characteristics approach was used for the selection and optimization of I-ELISA cut-offs including the misclassification costs term and Youden index (J). In addition, cut-off values were determined as the mean plus two-fold standard deviation of the result observed with the RVFV-free subpopulations. Established optimal cut-offs were different for each of the data sets analyzed, and ranged from 1.65 PP (buffalo) to 9.1 PP (goats). At the cut-off giving the highest estimate of combined measure of diagnostic accuracy (highest J value), the I-ELISA test parameters were determined as follows: (1) Diagnostic sensitivity (%): cattle--84.31, buffalo--94.44, sheep--98.91, goats--99.18. (2) Diagnostic specificity (%): cattle--99.34, buffalo--98.28, sheep--99.16, goats--99.23 and other game ruminants--99.26. In the group of RVFV-experimentally infected sheep, seroconversion In all individuals was detected by VN on 4-6 dpi, by HI on 5-7 dpi, and by I-ELISA on 6-7 dpi. All tests showed the same kinetic pattern of immunological response. Antibody levels were low for a very short period before increasing to high titres, after which it was easily detectable by all tests. Compared to traditional tests, the lower sensitivity of I-ELISA in the detection of the earliest stage of immunological response may be practically insignificant, particularily when this assay is used in population-based, disease-surveillance programmes. The high sensitivity and specificity of I-ELISA established in this study, especially for the statistically more representative subpopulations of animals tested, seem to support this prediction. Test parameters determined in this study should, however, be regarded as in-house diagnostic decision limits, for which further updating is recommended, particularly for specimens from other countries, and preferably by applying a standardized method for sampling of new subpopulations of animals to be targeted by the assay.

Animals↗
PubMed1991

Effect of gamma irradiation on alpha-tocopherol levels in ruminant blood samples.

Quantification of circulating levels of vitamin E in free-ranging species can provide useful guidelines for evaluating nutrient status in captive exotic animals. Under current USDA regulations, ruminant plasma or serum samples must be subjected to 1) live-animal testing and viral screening, or 2) gamma (gamma-) irradiation prior to importation. Because irradiation is known to promote free radical formation and destruction of alpha-tocopherol in various tissues, these studies were conducted to evaluate the effect of irradiation on ruminant blood fractions with and without added antioxidant. alpha-tocopherol levels were measured in paired (irradiated vs. unirradiated) plasma or serum samples collected from zoo ruminants (n = 8 spp.). Irradiation caused highly significant (P less than 0.001) but inconsistent destruction of alpha-tocopherol. Addition of 10% volume of a 1% pyrogallol solution to plasma or serum protected against alpha-tocopherol deterioration during gamma-irradiation. In order to ensure valid comparative values for vitamin E studies while complying with USDA regulations, it is recommended that plasma or serum samples collected from ruminants outside the US be treated with antioxidant prior to importation.

Animals↗