Location: Nutrition, Growth and Physiology2017 Annual Report
1a. Objectives (from AD-416):
Objective 1: Determine the nutrient value and environmental consequences of novel feed products. Component 1: Problem Statement 1A Objective 2: Improve determination of dynamic changes in nutrient requirements as the animal’s physiological status changes to allow for timed nutrient delivery. Component 1: Problem Statement 1A Objective 3: Determine the role of malnutrition during critical periods in developmental programming and epigenetic effects that alter lifetime production potential and product quality. Component 1: Problem Statement 1A Objective 4: Determine metabolic and physiological mechanisms responsible for variation in feed efficiency that is under genetic control. Component 1: Problem Statement 1A Objective 5: Determine age, gender, genetic, and environmental factors that account for variation in feeding activity and growth of swine Component 1: Problem Statement 1C Objective 6: Characterize the response of cattle to changes in environmental temperature with respect to various management strategies and animal risk factors. Component 1: Problem Statement 1C Obective 7: Determine the relationships between ruminal microbial communities, animal genotype, and/or methane production with feed/nutrient use efficiency and/or lactation performance in response to varying nutritional regimens in beef or dairy cattle. Component 1: Problem Statement 1A Component 2: Problem Statement 2B; Problem Statement 2D
1b. Approach (from AD-416):
Feed costs represent the single largest input in both beef and swine production; however, less than 20% of the feed energy is converted to edible product. Improving the efficiency that feed is converted to animal products has the potential to improve the economic efficiency of animal production while improving the sustainability of animal agriculture. To maximize feed efficiency the correct profile of nutrients are matched to meet an animal’s needs for its current biological status (growth, pregnancy, lactation, previous nutrient history, and disease). In order to provide the correct profile of nutrients, the nutrient composition of feeds and the dynamic nutrient requirements of the animal must both be identified and then synchronized. There is genetic variation amongst animals in their ability to utilize feed. Multiple genes are associated with the regulation of feed intake, and the utilization of ingested nutrients. Differential expression of these genes results in variation of feed efficiency amongst animals within populations, and these genetic differences potentially change the nutrient requirements of the animal. Nutrient status during critical periods of development (fetal and peripuberal) can permanently modify the expression of genes changing the lifetime feed efficiency of an animal. Identifying the role of nutrition in regulating gene expression is needed to develop nutrition management strategies across generations of animals in a production system.
3. Progress Report:
This is the final report for Project 3040-31000-092-00D, which has been replaced by new project 3040-31000-097-00D. During the life of this project, eight studies were conducted to address Objective 1: Determine the nutrient value and environmental consequences of novel feed products. Four of the studies included titrating the appropriate amount of fiber or the amount of coproducts on improving feed efficiency of beef cattle. A nutrient balance experiment using distillers grains was conducted to determine the interaction of distillers and grain processing on nutrient utilization. A nutrient balance trial was conducted to determine optimum inclusion levels of glycerol in diets. The other two studies combined a nutrient balance trial and a feeding trial that titrated fiber levels. These studies determined the optimum inclusion levels to improve nutrient utilization and production efficiency. The remaining studies investigated the use of feed additives on changes of nutrient utilization. Two feeding studies were conducted to determine the effect of beta-agonists on feed utilization and animal health of beef cattle. One study was conducted to determine the effect of beta-agonists on protein requirements of beef cattle and the other study determined the relationship between beta-agonist heat stress and use of shade to mitigate heat stress. Two additional studies were conducted in pigs (n = 1,000) to determine the efficacy of a naturally occurring antimicrobial as a substitute to antibiotics. The pig studies focused on mechanisms of improved nutrient utilization. The studies included studying gut morphology and effects on human pathogens. All of these studies have been reported in peer-reviewed publications. Two studies were conducted to address Objective 2: Improve determination of dynamic changes in nutrient requirements as the animal’s physiological status changes to allow for timed nutrient delivery. An ongoing study is being conducted in pigs to determine mechanisms that contribute to differences in body weight gain at common feed intakes. To date, individual feed intake and body weight gain have been measured on approximately 3,000 pigs. Approximately 750 pigs expressing extreme feed efficiency phenotypes have been sampled. Body composition is being determined. The gut size and morphology are being determined in these pigs. Efficiency of nutrient absorption across the jejunum has been determined using Ussing chambers. Mitochondrial activity has been determined in the muscle and liver. A two-year study was conducted on 168 mature cows to determine the effect of protein supplementation strategies on low quality forage utilization during pregnancy. Individual feed intake, body weight gain, body fatness, and calf birth weights were determined. In addition, uterine blood flow rates were determined on a subset of these cows. Four studies were conducted to address Objective 3: Determine the role of malnutrition during critical periods in developmental programming and epigenetic effects that alter lifetime production potential and product quality. Two were lifetime production studies. These studies are still in the evaluation phase. One of the studies altered the nutrient environment to fetuses. Production performance and longevity of 400 females from these different environments are being evaluated. A peer-reviewed publication reporting their performance as heifers and cows are continuing to be evaluated at older ages. The other study altered nutrient availability of 672 heifers around puberty. Production performance and longevity continue to be evaluated. Two additional studies were conducted to determine the mechanisms associated with differences in fertility between heifers aggressively fed and moderately fed near puberty. These studies resulted in two peer-reviewed publications. Nine studies were conducted to address Objective 4: Determine metabolic and physiological mechanisms responsible for variation in feed efficiency that is under genetic control. In one study individual feed intake was determined on 845 pedigreed heifers. Feed intake was subsequently determined on the same females as 5-year-old cows. Heritability estimates and genetic correlations between heifer and cow intake, and intake and production traits were determined. Data are currently being analyzed. A study was conducted in mature cows to determine the effect of level of nutrition and ability to gain body weight on the transcriptome of adipose and muscle of mature cows. Data has been analyzed. Two studies were conducted in cattle to determine the relationship between metabolic/hormone profiles and feed efficiency. In each study, approximately 140 head of cattle were fed and the 8 animals with the greatest and least body weight gain were selected to conduct targeted metabolomics studies. In one of these feeding studies, non-targeted metabolomics was used to determine the metabolite differences in the rumen of steers differing in feed efficiency. In one of these studies, a targeted transcriptome study of immune products was conducted to determine differences in cattle ranked greater or less for feed efficiency. Results from these studies have been reported in peer-reviewed publications. Five feeding trials (with 200 animals per trial) were conducted to determine genomic differences in cattle that differed in feed intake and body weight gain. Differential gene expression was determined throughout the gastro-intestinal tract and the mesenteric fat pad. Results from these studies have been reported in peer-reviewed publications. Feed intake data and plasma samples are being collected on growing pigs to conduct a non-targeted metabolomics analyses of pigs that differ in feed efficiency. Four studies were conducted to address Objective 5: Determine age, gender, genetic, and environmental factors that account for variation in feeding activity and growth of swine. These studies focused on understanding the influences of environment on swine behavior and thermal regulation. Feeding behavior was evaluated on 1,920 grow-finish pigs. Evaluations of genetics, gender, age, and environment were conducted. Publications have been submitted to describe these effects on feeding behavior. In addition, publications have been prepared to describe the effects of temperature on surface temperature and huddling changes at three different ages of growing and finishing pigs. An experiment was conducted to address Objective 6: Characterize the response of cattle to changes in environmental temperature respect to various management strategies and animal risk factors. They evaluated the impact of shade on a group of cattle differing in coat color but with similar genetic backgrounds. One hundred and eighty head of cattle influenced by the Angus, Hereford, Simmental, Charolais, Limousin, Red Angus, and Gelbvieh breeds were used. Solar load on the pens was reduced when shade was provided with both ground temperature and black globe temperature showing reductions. Cattle showed nominally better performance; however, no significant differences were found with gain or feed intake. Panting scores were not significantly lower with shade provided; however, slopes of cattle respiration rate versus ambient temperature were significantly lower with shade. It was hypothesized that the shade, constructed out of snow fence, did not offer enough of a reduction in solar radiation to have much of an impact on reducing stress. This research resulted in a peer-reviewed publication. Four studies were conducted to address Objective 7: Determine the relationships between ruminal microbial communities, animal genotype, and/or methane production with feed/nutrient use efficiency and/or lactation performance in response to varying nutritional regimens in beef or dairy cattle. Two feeding studies were conducted to determine individual feed intake and body weight gain. Cattle that had extreme feed intakes and body weight gains were selected to determine if they differed in their microbiota. Sequencing of the 1 to 3 variate regions on the 16sr was used to sequence bacteria in the rumen, jejunum, duodenum, cecum, and colon. In a study classifying eight steers into least and eight steers into greatest feed efficiency, enteric methane production was determined. Rumen and cecum methane in vivo production was determined as well as methanogen profiles through 16s sequencing. A study was conducted feeding oil to steers to determine its effect on methane production in steers.
1. Improving production efficiency of cattle by increasing beef produced per amount of feed offered would result in economic and environmental benefits. Digestion and nutrient absorption is considered one of the most important sources of variation in cattle growth efficiency. Hence, differences in feed efficiency might be related to changes in the chemical profile in the cattle stomach (rumen). In a joint project between the ARS location at Clay Center, Nebraska, and the University of Nebraska researchers used a distinct ruminal profiling method, identifying 33 biomarkers related to differences in feed efficiency. Metabolites associated with fatty acid metabolism (linoleic and alpha-linolenic) and synthesis of protein (aromatic amino acid), were the most different metabolites associated with differences in feed efficiency. The combination of ruminal pentadecanoic acid, palmitic acid, linoleic acid and alpha-linolenic acid, and the combination of plasma arachidonic:docahexanoic ratio and alpha-linolenic acid, were able to distinguish lower and higher feed efficiency animals in rumen fluid and blood, respectively. The use of biomarkers in blood or rumen fluid could allow for the prediction of feed efficiency in cattle and also provide insight into physiological mechanisms that contribute to variation in feed efficiency.
2. Feeding beta-agonist zilpaterol hydrochloride increases protein accretion. The influence of shade while feeding this compound was evaluated. ARS scientists at Clay Center, Nebraska, determined blood lactate concentration was not different between zilpaterol hydrochloride and control fed cattle fed in open or shaded pens. Cortisol, a measure of acute stress, was less in cattle after they had been fed zilpaterol hydrochloride. Blood glucose levels were greater for cattle fed the control diet than those fed zilpaterol hydrochloride for 21 days. Plasma urea nitrogen was not different across any treatments. Lung scores measured using a digital stethoscope were increased (worse) after zilpaterol hydrochloride was fed. From these data, we interpret that metabolic profiles change in response to feeding zilpaterol hydrochloride. Cattle fed zilpaterol hydrochloride are less glucose dependent and likely more dependent on fatty acid breakdown. The lack of differences in cortisol and lactate concentrations indicate that there was not an acute stress response associated with cattle fed control or zilpaterol hydrochloride diets in shade or open pens.
3. There is variation in feed efficiency of beef cattle, but the sources of that variation are poorly understood. The liver typically consumes at least 25% of the daily oxygen. ARS scientists at Clay Center, Nebraska, determined a total of 729 genes in the liver that were differentially expressed between cattle classified as low or high in feed efficiency. These genes were analyzed for representation among pathways or biological processes. Pathways related to protein turnover, transport, and immune function/inflammatory response were identified. The pathways identified suggest that immune response, transporter activity, and protein degradation within the liver may be contributing to cattle feed intake and gain phenotypes. The genes differentially expressed will aid in selecting cattle with superior feed efficiency phenotypes and help further understand the underlying biological mechanisms associated with feed efficiency.
4. Feed is the single largest cost associated with beef production. Efficient absorption and utilization of nutrients by the gastrointestinal tract of animals are important in efficient conversion of feed to body growth of animals. The use of natural compounds such as butyrate has the potential to improve nutrient absorption and utilization by gastrointestinal tract of ruminants. ARS scientist at Clay Center, Nebraska, determined that butyrate treatment increased the rate of uptake of glucose, glutamate, glutamine, and oxygen. Nutrient metabolism by the liver was not affected by the butyrate treatment. It is possible that the butyrate treatment stimulated glycolysis in the gastrointestinal tract. It is more likely that the butyrate treatment stimulated growth of the gastrointestinal tissue which increased the utilization of glucose, glutamate, glutamine, and oxygen. Supplying targeted nutrients to the small intestine could improve gut health, and therefore improve feed efficiency.
5. There is a lack of data about the physiological mechanisms that control feed intake in beef cattle. Feed intake of cattle given unlimited access to feed is a large contributor to the efficiency with which cattle use nutrients for growth. Little is currently known about factors that contribute to differences in feed intake of cattle. Ghrelin is a hormone that has been associated with feed intake in rodents and humans. ARS scientist at Clay Center, Nebraska, has determined steers had greater initial acyl ghrelin concentrations than heifers, but decreased over time to be similar to concentrations in heifers. Total ghrelin concentrations were initially lower in heifers but increased to be similar to steers. Greater initial concentrations of acyl ghrelin were associated with greater feed intake, growth rates, and feed efficiency. This indicates that ghrelin is likely involved in the regulation of feed intake of cattle with unlimited access to feed, and could be a promising candidate for a marker for feed intake in beef cattle.
6. Methane loss from finishing cattle is important as it represents an energy loss that could be used for maintenance and growth, and methane is a greenhouse gas with a global warming potential much greater than that of carbon dioxide. The use of added fat source is common in high-concentrate finishing diets. Scientists at Clay Center, Nebraska, determined that corn oil does not affect intake across dietary treatments, but methane production decreased as corn oil increased in the diet. From these data, we interpret that adding dietary fat decreases enteric methane production in addition to increasing the amount of energy retained as fat and carbohydrate instead of protein.
7. Feed is the single largest cost associated with beef production. There is variation in feed intake and efficiency in feed utilization by cattle. Endocannabinoids, including anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are a class of lipids that activate cannabinoids receptors and may be involved in the control of feed intake and energy metabolism. Blood concentrations of AEA and 2-AG in nonruminants have been considered as indicators of obesity and metabolic disorders. In a joint project between the ARS scientists at Clay Center, Nebraska, and the University of Nebraska researchers determined that blood concentration of AEA was positively associated with gain:feed ratio, indicating that more efficient animals had greater AEA plasma concentrations. In addition, greater AEA concentration was associated with less 12th rib fat thickness; but not associated with USDA–calculated yield grade or marbling score. The concentration of 2-AG was positively associated with AEA; however, 2-AG concentration was not associated with parameters of feed efficiency or carcass composition. These results provide evidence that plasma concentration of a key endocannabinoid, AEA, might be a useful indicator of feed efficiency and fat thickness in finishing steers.
8. There is variation in feed efficiency of beef cattle, but the sources of that variation are poorly understood. The spleen is a major lymph organ that lies near the digestive tract. We had previously identified that beef steers with differences in gain and feed intake also had differences in levels of gene transcripts in digestive tract organs that were related to immune responses. Scientist at Clay Center, Nebraska, evaluated the transcript levels of over 24,000 genes in the spleen. A total of 1,216 genes were identified as differentially expressed. Of the genes differentially expressed, there were an over-abundance of genes that belong to pathways that included antigen processing and presentation, olfactory transduction, and nucleotide metabolism. Several stress response genes were also identified as a gene cluster identified by function. These genes were identified by increased expression in animals with low gain and low feed intake. An analysis of genes that were expressed and have additional numbers of gene copies in the spleen produced some of the same genes and gene families that were differentially expressed. Our data suggests the splenic contribution to some of the underlying variation among gain and intake within this group of animals may be a result of immune function and stress response. In addition, some of the differences in immune response functions may be related to the number of gene copies.
9. The ability to identify animals that consume less feed yet perform well in terms of weight gain could benefit producers. A previous study of the genes transcribed by the rumen papillae tissue in beef steers produced genes that were differentially expressed in animals with variation in weight gain and feed intake. Some of the genes identified as differing between animals with high gain-low feed intake and those with low gain-high feed intake were examined for association with a related trait, residual feed intake (RFI), in a separate population of Angus x Hereford steers. ARS scientist at Clay Center, Nebraska, tested 17 genes and determined 2 were differentially expressed by residual feed intake classification. These genes included NAD(P)H dehydrogenase, quinone 1 and, regulator of G-protein signaling 5. A third gene, acetyl-CoA acetyltransferase 1, displayed a trend towards association with residual feed intake. This suggests that some of the genes identified in a previous rumen transcriptome study may have utility for identifying or selecting for animals with superior feed efficiency phenotypes across cattle breeds and populations. Identifying genes expressed may assist with the identification of cattle with more efficient phenotypes.
10. Methane loss from finishing cattle is important as it represents an energy loss that could be used for maintenance and growth, and methane is a greenhouse gas with a global warming potential much greater than that of carbon dioxide. ARS scientist at Clay Center, Nebraska, determined that in general the greatest methane production occurred 5 to 6 hours after feeding with a secondary peak in methane production occurring 9 to 11 hours after feeding in steers fed above maintenance intake. In steers fed at a maintenance level of intake, there was only one peak in methane production usually four to seven hours after feeding. Caution should be exercised when using a single time point measure of methane production and extrapolating it to an estimate of 24-hour methane production.
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