Browsing by Subject "Nitrogen utilization efficiency"

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Genomische und mikrobielle Analysen von Effizienzmerkmalen beim Schwein
(2022) Weishaar, Ramona Ribanna; Bennewitz, Jörn
Most traits in animal breeding, including efficiency traits in pigs, are influenced by many genes with small effect and have moderate heritabilities between 0.1 and 0.5, which enables efficient selection. These so-called quantitative traits are influenced by genetic factors and environmental factors. The use of next-generation sequencing methods, such as 16S rRNA sequencing to analyse the gut microbiome of livestock, allows identification and analysis of the gut microbiota. It has been shown that the composition of the microbiota in the gastrointestinal tract is heritable and has an influence on efficiency traits. Thus, the animal genome influences the phenotype not only directly by altering metabolic pathways, but also indirectly by changing the composition of the microbiota. This increases the interest in implementing gut microbiota into existing breeding strategies as an explanatory variable. The potential of an efficient utilization and absorption of nutrients varies between individuals. Differences in nutrient absorption depend on feed intake, digestion of dietary components in the stomach and intestine, and intake of digested nutrients from the gastrointestinal tract into blood and lymphatic vessels. Undigested nitrogen is excreted as urea and can be detected by blood urea nitrogen (BUN). The BUN is correlated with efficiency traits and there exist differences between pig breeds. Thus, therefore the BUN would be conceivable as an easier recordable trait for nitrogen utilisation efficiency in pig breeding. In the first chapter of this study, an existing data set of the Department for Animal Genetics and Breeding of the University of Hohenheim was used. This is a data set with 207 phenotyped and genotyped Piétrain sows. The relationship between gut microbial composition, efficiency traits and the porcine genome is investigated using quantitative genetic methods. The heritabilities of the traits FVW, RFI, TZ, and FI ranged from 0.11 to 0.47. The microbiabilities of the traits were significant and ranged from 0.16 to 0.45. In a further step, the previously generated microbial animal effects were used as observation vector for a genomic mixed model. Subsequently, heritabilities for the microbial animal effect were estimated, ranging from 0.20 to 0.61. The similarity of the heritabilities and microbiabilities suggests that the traits are influenced to a similar extent by both genetics and gut microbiota and that the microbial animal effect is determined by the host. These results are underlined by the identification of genera and phyla with significant effects on efficiency traits. The microbial architecture of the traits demonstrated a poly-microbial nature, there are many OTUs with small effects involved in the variation of the observed traits. Genomic Best Linear Unbiased Predictions (G-BLUP) and Microbial Best Linear Unbiased Predictions (M-BLUP) were performed to predict complex traits. The accuracies of M-BLUP and G-BLUP were all in a similar range between 0.14-0.41. This shows that gut microbiota could be used to predict performance traits or be included as a variable in the existing models of breeding value estimation to realize an increase in accuracies. The second part of the paper analysed a dataset from a research project called "ProtiPig". The data set included 475 sows and castrates of crossbreds of German Landrace x Piétrain and was analysed for protein utilization efficiency and nitrogen(N)-utilization efficiency. N-utilization efficiency is a trait that is difficult to record. Because conventional metabolic cage methods are a very complex procedure and difficult to integrate in the standard recording, it was tested whether the BUN is suitable as a proxy trait. Moderate to medium heritabilities could be estimated for all traits and ranged from 0.13 to 0.49. The genome-wide association studies showed that the traits were polygenic. For the BUN, SNPs could be detected that were above the genome-wide significance level. Significant genetic and phenotypic correlations were found between some traits. In particular, the heritabilities of BUNs and the significant genetic correlation between BUN and N-utilization efficiency indicate an opportunity to use the BUN to select for improved N-utilization efficiency. Before the research results generated here can be implemented in breeding practice, further questions must be clarified. In addition, a larger number of animals is needed to validate the results. The results presented here demonstrate the potential of microbial-assisted breeding value estimation and the use of BUN to identify selection candidates for breeding for increased efficiency.
Investigations on factors influencing the response of broiler chickens to low crude protein diets with specific regard to nonessential amino acids
(2020) Hofmann, Philipp; Rodehutscord, Markus
Nitrogen (N) excretion caused by animal husbandry can have negative effects on the environment. Lowering dietary crude protein (CP) concentrations can reduce these negative impacts by lowering the N excretion of the animals. However, reduction of dietary CP concentrations for broiler chickens may be accompanied by reduced growth. This thesis focused on the effects of dietary CP reduction on growth of broiler chickens and influencing factors that need to be considered in low CP diets. The first study was carried out to investigate to what extent dietary CP concentrations can be reduced when dietary glycine equivalent (Glyequi) and essential amino acid (AA) concentrations are adequately supplied. Further, it was the aim to determine the response of broiler chickens to dietary Glyequi concentrations at varying CP levels. Ten male broiler chickens each were housed in 1 of 84 metabolism units. Diets with three CP levels of 16.3% (CP16.3), 14.7% (CP14.7), and 13.2% (CP13.2) each containing four Glyequi concentrations of 12, 15, 18, and 21 g/kg were used. Quantitative excreta collection was carried out from days 18–21. The reduction of dietary CP concentrations decreased average daily gain (ADG) and gain:feed ratio (G:F) from days 7–21 and increased the nitrogen-utilization efficiency (NUE). Supplementation of Glyequi increased ADG and G:F at CP13.2. The ADG at CP14.7 and G:F at CP14.7 and CP16.3 increased up to 15 g Glyequi/kg. These results indicated that the minimum to which dietary CP concentrations can be reduced in broiler chickens up to three weeks of age is between 16.3 and 14.7% when dietary Glyequi and essential AA are adequately supplied. Further, these findings showed that the growth-response of broiler chickens to dietary Glyequi is influenced by dietary CP concentrations. The second study was conducted to determine whether supplementation of single nonessential AA (neAA) can diminish or overcome the growth-decreasing effect of a diet with reduced dietary CP and neAA concentrations. Further, the effect of non-protein nitrogen supplementation in a diet with insufficient neAA concentrations was investigated. Nine male broiler chickens each were kept in 1 of 81 metabolism units. Two diets with different neAA concentrations, except Glyequi, and adequate essential AA concentrations were mixed resulting in CP levels of 17.8% (CP17.8), and 15.6% (CP15.6). The dietary Glyequi concentration was 15 g/kg in each diet. Other diets were mixed by supplementing either L-Alanine, L-Proline, L-Aspartic acid, a mix of L-Aspartic acid and L-Asparagine·H2O, L-Glutamic acid, or a mix of L-Glutamic acid and L-Glutamine to CP15.6 to achieve the respective neAA concentration of CP17.8. Ammonium chloride (NH4Cl) was added to CP15.6 to achieve the CP concentration of CP17.8. Excreta were collected quantitatively from days 18–21. Highest ADG and G:F from days 7–21 were found at CP17.8 and decreased at CP15.6. Supplementation of aspartic acid and asparagine (Asp+Asn), glutamic acid (Glu), and glutamic acid and glutamine (Glu+Gln) increased ADG and G:F to a similar extent, but not to the level of CP17.8. The NUE was highest at CP15.6, and CP15.6 supplemented with alanine, proline, and Glu. Lower NUE was observed at CP17.8 than at CP15.6 without and with neAA supplementation. Overall lowest ADG, G:F, and NUE were found upon NH4Cl supplementation. These findings showed that individual supplementation of Asp+Asn, Glu, and Glu+Gln could partly overcome the growth-reducing effect of very low CP diets. NH4Cl was found unsuitable to increase growth. The aim of the third study was to investigate interactive effects among dietary Glyequi, cysteine (Cys), and choline (Cho) on the growth of broiler chickens. Ten male broiler chickens each were housed in 105 metabolism units. Excretion of N was determined from days 18–21. Five levels each of dietary Glyequi, Cys, and Cho were tested in 15 dietary treatments. Another diet was provided to 15 birds each in another 5 metabolism units to measure prececal AA digestibility. The G:F from days 7–21 increased with digestible Glyequi intake. Differences between low- and high-digestible Cys intake were low. Hardly any effect of Cho intake on G:F was found compared to digestible intake of Glyequi and Cys. The NUE was very high with low variation among treatments. These results showed that the interactive effects among dietary Glyequi, Cys, and Cho on growth were slightly pronounced. This was likely an effect of high NUE and its low variation that caused the Glyequi requirement to be low. In conclusion, the lowest level to which dietary CP for broiler chickens up to three weeks of age can be reduced is between 16.3 and 14.7%. The growth-decreasing effect of a diet with reduced neAA concentrations can be slightly overcome upon supplementation of Asp+Asn, Glu, and Glu+Gln. Moreover, dietary CP concentrations and the related amounts of excreted N influenced the response of broiler chickens to dietary Glyequi.
Variation and estimation of nitrogen utilization efficiency in a crossbred pig population
(2022) Berghaus, Daniel; Rodehutscord, Markus
Efficient utilization of dietary nitrogen (N) in pork production is of increasing concern. Previous studies revealed that a genetic basis for N utilization efficiency (NUE) might exist, but to assess the potential of breeding for improved NUE, the between-animal variation of a large number of animals needs to be known. The standard method to determine N retention (NR) in balance trails is laborious and not feasible for the required numbers of animals. However, correlations between protein utilization and blood urea nitrogen (BUN) concentration have been shown to exist and body protein turnover is subject to hormonal control. Hence, the objective of the present thesis was to quantify NR of growing pigs at two different growth stages by N balance and to determine the impact of body protein turnover on NUE. In addition, equations for the estimation of NR were established, using performance data and blood metabolite concentrations, which were applied to evaluate the variation in NUE of a F1 crossbred population. Over a period of 2.5 years, a total of 508 crossbred pigs (German Landrace x Pietrain) from 20 different boars was investigated from the 11th week of life until slaughter. The pigs were housed individually throughout the experimental period and a two-phase fattening was performed. All animals received the same diet for ad libitum intake which was formulated to contain 90% of the recommended lysine concentration so that marginal lysine supply was the limiting factor for protein retention and pigs were allowed to express their full genetic potential of NUE. In both fattening phases, daily feed intake was recorded for each animal in a five-day sampling period (SP), and blood samples were taken from the jugular vein at around 13:00 h on three consecutive days for determination of BUN, cortisol, and insulin-like growth factor 1 (IGF-I) concentration. Additionally, in both SP, N balance was performed in the same experimental barn on a randomly selected subsample of 56 barrows. The barrows were housed in metabolism crates for six days, two days for adaption and four days for quantitative collection of feces and urine. Simultaneously, their body protein turnover was determined using the end-product method after a single oral dose of 15N-labeled glycine. Based on the N balance results, models for estimation of NR were obtained by multiple regression of performance data and blood metabolite concentrations. The significance of the variables was validated using a bootstrapping method to avoid overfitting the models to the observed data. The goodness of fit of the equations was assessed using the coefficient of determination and the root mean square error. The N balance results revealed a high protein retention potential of the animals, which did not differ on average between the two SP. However, large differences in NR were observed between individuals and NR was strongly correlated with N and lysine intake. NUE was also at a high level and varied considerably between individuals. The mean NUE was significantly higher in SP1 than in SP2 and a moderate correlation was observed between NR and NUE. The mean body protein turnover did not differ between the SP and no correlation with NUE was observed. In estimating NR, the model with the best goodness of fit included the variables initial body weight, average daily gain, average daily feed intake, N intake, BUN, cortisol, and IGF-I concentration. This model was used to estimate NR for all animals and subsequently calculate their NUE. Describing NR as a linear function of lysine intake across both SP showed an average marginal efficiency of lysine utilization for protein retention of 67%. Despite a wide variation in NUE within the offspring of the same boars, significant differences were found between the offspring groups of the boars. Under the prevailing circumstances of marginal lysine supply, the NR of fattening pigs could be estimated from performance data and blood metabolite concentrations with satisfying accuracy. This provides a fast and reliable alternative to performing N balance studies, reducing the experimental effort considerably in studies with large numbers of animals. Although lysine supply was the limiting factor for protein retention, only about 70% of the variation in NR could be explained by the level of lysine intake. The remaining part of the variation was likely caused by differences in the intermediary lysine utilization or differences in the lysine content of the retained body protein between individuals. About 50% of the variation in NUE could be explained by differences in the level of NR, implying that pigs with higher protein retention potential utilized dietary N more efficiently. However, this was not accompanied by differences in body protein turnover. Phenotyping of the F1 crossbred population revealed a large variation between individuals and a significant boar effect, indicating the possibility of improving NUE through breeding measures.