Faecal Nitrogen Concentration Research Articles

360 Effect of Dietary Protein Levels and Growth Promotants in Dairy-Beef Cross Steers on Nitrogen Utilization Efficiency

Abstract Reducing nitrogen excretion of finishing beef cattle is needed to protect the environment but methods used to decrease nitrogen excretion need to have economic benefits as well. The objective of this experiment was to determine the potential of implant strategy and phase-feeding crude protein (CP) to reduce urinary nitrogen (UN) and fecal nitrogen excretion. Holstein × Angus steers (n = 72) were blocked by body weight (BW) and treatments were randomly assigned to pens (n = 4 per treatment). This experiment was a 2 × 2 factorial design, where cattle were fed a constant CP (control), or the CP content of the diet was reduced every 49 days (phase-fed) and cattle received either an aggressive or moderate implant strategy. All cattle were implanted on d-0 and d-98. Body weight was measured, and blood, urine, and fecal samples were collected on days 0, 49, 98, 147, and at shipping. Phase-feeding CP and implant strategy had no effect (P ≥ 0.47) on dry matter intake or average daily gain. There was a tendency (P = 0.10) for a diet × implant-strategy interaction for feed efficiency, indicating that phase-fed cattle were more efficient with the moderate implant strategy than the aggressive implant strategy. UN excretions decreased (P < 0.01), on day-147 among both implant treatments, indicating that re-implanting on d-98 may have reduced nitrogen excretion. There was a sampling-day × implant interaction (P ≤ 0.03) and a sampling-day × diet interaction (P < 0.01) for blood urea nitrogen concentrations (BUN) and total UN excretion, where BUN and total UN excretion were decreased among the moderate implant and the phase-fed groups on day-147 compared with the aggressive implant and control-fed groups, respectively. Overall, fecal nitrogen concentrations were less for the phase-fed treatment group compared with the control (P ≤ 0.05). These results suggest that phase-feeding CP can be an effective strategy to reduce nitrogen excretion from cattle in the feedlot without negatively affecting performance.

Differences in Faecal Nutritional Components in Three Species of Saharan Gazelles on Standard Diets in Relation to Species, Age and Sex.

Various environmental, individual, and species-specific factors may affect digestive efficiency in wild ruminants. The study of faecal nutritional components is a commonly used technique to understand these effects, assuming that faecal nitrogen and fibre contents reflect the diet's nutritional quality and digestibility. Recent studies have highlighted the relatively high influence of factors like sex, age, weight or body condition on digestive efficiency. This manuscript is focused on the inter-specific variability in faecal nutritional components under the same feeding regime, using three captive populations of closely related gazelles as model species. Faecal samples from 193 individuals were analysed through Near InfraRed Spectroscopy. Species, sex and age influence on faecal nitrogen and fibres (ADF and NDF) were investigated. We found inter-specific differences in the faecal content of the three studied nutritional components. Cuvier's gazelle showed lower faecal nitrogen content, suggesting lower digestive efficiency than dorcas and dama gazelles. Sex and age also had a moderate effect, especially in faecal nitrogen, but these effects were not constant across the three studied species. On the contrary, faecal fibres were highly constant (i.e., dependent on diet quality). These results confirm that individual factors affecting faecal nutritional components are also species-specific.

54 Impact of Ileal Indigestible Protein on Nitrogen Excretion and Fecal Microbiota may be Greater Compared with Total Protein Concentration of Diets in Growing Pigs

Abstract The effect of changes in dietary ileal indigestible protein concentration may be more influential in the amount of nitrogen flowing to the large intestine compared with changes in total dietary protein concentration. For this reason, we hypothesized that an increase in dietary ileal indigestible protein concentration induces an increase in hindgut nitrogen utilization and nitrogen excretion and a shift in fecal microbiota in growing pigs, when compared with pigs given a high total protein diet. Three diets were prepared: 1) standard protein diet based on corn and soybean meal, 2) high-indigestible protein diet in which autoclaved soybean meal replaced normal soybean meal in the first diet, and 3) high protein diet where the inclusion rate of soybean meal was greater than that of the other diets. T-cannulated barrows (n = 18; initial BW = 63.4 ± 8.0 kg) were allotted to the 3 diets in a randomized complete block design with BW as a blocking factor. Pigs were individually housed in pens and the experiment lasted for 23 days. On d 7 and 21, fecal samples were collected by rectal massage for microbiota analysis. Grab samples of feces were collected on d 20 and 21, and ileal digesta were collected on d 22 and 23 for the determination of energy and nitrogen utilization. Energy and nitrogen utilization data were analyzed using the MIXED procedure of SAS using a pig as the experimental unit and a model that included diet as a fixed variable and block as a random variable. For microbiome analysis, R was used. Alpha and beta diversity metrics were analyzed and the difference in abundance of the genus was determined using the DESeq2 function. The high-indigestible protein diet achieved decreased apparent ileal digestibility of nitrogen and resulted in greater ileal indigestible nitrogen concentration (P < 0.05). Apparent total tract digestibility of nitrogen was less (P < 0.05), and correspondingly fecal nitrogen concentration and daily fecal nitrogen output were greater (P < 0.05) in the high-indigestible protein diet. Apparent post-ileal digestibility and hindgut disappearance of nitrogen and gross energy were the greatest (P < 0.05) in the high protein diet. Beta diversity metrics of feces in the high-indigestible protein diet on d 21 were different (q < 0.05) from those in the other two diets, which indicates a shift in fecal microbiota. According to the DESeq2 results, the direction of the microbiota shift induced by the high-indigestible protein diet may have reduced hindgut fiber utilization. In conclusion, an increase in dietary ileal indigestible protein increased nitrogen excretion and shifted fecal microbial communities but did not increase hindgut nitrogen utilization.

142 Evaluation of Dietary Fiber in Health Challenged Nursery Pigs

Abstract Enteric pathogens often antagonize nursery pig health, growth performance, and scouring. Increased dietary fiber may alleviate bacterial pathogen burdens via improving intestinal health, fecal consistency, binding of pathogens, and improving early post-weaned growth performance. Therefore, our objective was to evaluate the effect of three dietary fiber sources on growth performance, digestibility, and fecal consistency in nursery pigs undergoing an F18 enterotoxigenic Escherichia coli (ETEC) challenge. The study was conducted with 541 newly weaned pigs (starting BW of 5.9 ± 1.25 kg) in a complete randomized design with four dietary treatments (n = 12 pens/treatment, 11to 12 pigs/pen), fed over three phases. Phase 1 (day 0 - 14) and 2 (day 15 - 28) treatments included: 1) corn-soybean meal-based diet with no addition of fiber source (CON); 2) corn-soybean meal-based diet + 15 and 7.50% oat groats (Phase 1 and 2, respectively; Oats); 3) corn-soybean meal-based diet + 5% soyhulls (Soyhulls); and 4) corn-soybean meal-based diet + 5% wheat bran (Wheat Bran). All pens were fed a common Phase 3 (day 29 - 48) corn-soybean meal-based diet. At placement, 12 pigs were sacrificed for baseline evaluation and pigs were confirmed positive for K88 E. coli and Rotavirus A. On day 14 (dpi = 0), all pigs were orally drenched with ~5 mL F18 ETEC inoculum suspended in Luria broth. On day 21 of the study (dpi 7), 1 pig/pen was euthanized to examine the effects of diet on intestinal health including histopathology assessment of attachment of E. coli, coccidia, villus atrophy, and colitis. Pig BW and pen feed disappearance were recorded weekly from day 0 – 28, and day 48 to calculate ADG, ADFI, and feed efficiency (G:F). Data were analyzed using PROC MIXED of SAS with pen as the experimental unit and the fixed effect of treatment. There were no differences in ADG, ADFI, or G:F in phase 1 or phase 2 when pigs were fed Oats, Soyhulls, or Wheat Bran compared with CON (P > 0.05). Overall nursery ADG (0.43 vs. 0.41, 0.42, 0.40 kg/d, respectively), ADFI (0.67 vs. 0.67, 0.68, 0.64 kg/d, respectively), and G:F (0.55 vs. 0.55, 0.55, 0.55, respectively) were not different from CON when pigs were fed either Oat, Soyhulls, or Wheat Bran (P > 0.05). Pigs fed Oats had a decreased fecal nitrogen content compared with CON, Soyhulls, and Wheat Bran (P < 0.05) and no differences in dry matter, organic matter, or gross energy (P > 0.05). Although scouring was observed, fecal consistency scores did not differ between dietary treatments. Growth performance and fecal score data from this study indicate no additional benefit of a diet containing oat groats, soyhulls, or wheat bran to nursery pigs undergoing naturally endemic and controlled enteric health challenges.

Genetic analyses of nutrient digestibility measured by fecal near-infrared spectroscopy in pigs.

Improved nutrient digestibility is an important trait in genetic improvement in pigs due to global resource scarcity, increased human population and greenhouse gas emissions from pork production. Further, poor nutrient digestibility represents a direct nutrient loss, which affects the profit of the farmer. The aim of this study was to estimate genetic parameters for apparent total tract digestibility of nitrogen (ATTDn), crude fat (ATTDCfat), dry matter (ATTDdm), and organic matter (ATTDom) and to investigate their genetic relationship to other relevant production traits in pigs. Near-infrared spectroscopy was used for prediction of total nitrogen content and crude fat content in feces. The predicted content was used to estimate apparent total tract digestibility of the different nutrients by using an indicator method, where acid insoluble ash was used as an indigestible marker. Average ATTDdm, ATTDom, ATTDn, and ATTDCfat ranged from 61% to 75.3%. Moderate heritabilities was found for all digestibility traits and ranged from 0.15 to 0.22. The genetic correlations among the digestibility traits were high (>0.8), except for ATTDCfat, which had no significant genetic correlation to the other digestibility traits. Significant genetic correlations were found between ATTDn and feed consumption between 40 and 120 kg live weight (F40120) (-0.54 ± 0.11) and ATTDdm and F40120 (-0.35 ± 0.12) and ATTDom and F40120 (-0.28 ± 0.13). No significant genetic correlations were found between digestibility traits and loin depth at 100 kg, nor backfat thickness at 100 kg (BF), except between BF and ATTDn (-0.31 ± 0.14). These results suggested that selection for improved feed efficiency through reduced feed intake within a weight interval, also has led to improved ATTDdm, ATTDom, and ATTDn. Further, the digestibility traits are heritable, but mainly related to feed intake and general function of the intestines, as opposed to allocation of feed resources to different tissues in the body.

Parasite dilution improves lamb growth more than does the complementarity of forage niches in a mesic pasture grazed by sheep and cattle

Agroecological practices can improve the functioning of livestock farming systems by optimizing their underlying biological processes. Sheep/cattle mixed-grazing is an example of such a practice in which sheep grazing with cattle can achieve a higher liveweight gain (LWG), than sheep grazing alone. We conducted an experiment to assess the relative roles of parasite dilution and forage niche complementarity in improving sheep LWGs. We used continuous grazing and compared the LWGs of 5- to 9-month ewe lambs, grazing alone or with heifers, at two contrasting sheep/cattle ratios (~50/50% and 20/80% in livestock units). The animals were not treated for strongyles (gastrointestinal parasites) before or during the experiment. We assessed parasitism by counting the number of strongyle eggs excreted per gram of feces (EPG) and evaluated the forage niche complementarity through observations of feeding behavior, combined with measurements of fecal nitrogen content (N). We observed that i) the diet was moderately improved by mixed-grazing (+4% of dicots and +11% of young vegetative grass at most, but these improvement were not statistically significant (resp. P=0.28 and P=0.35); ii) N levels were not significantly different across treatments (~2%; P=0.75); iii) EPGs were ~50% lower for mixed-grazing than for monospecific grazing (545 and 716 vs. 1278, P<0.01), iv) LWGs were much higher for mixed-grazing than for monospecific grazing (~40 g per day higher, P<0.001); and v) LWGs and EPGs did not significantly differ between the two sheep/cattle ratios studied (resp. P=0.91 and P=0.56). We thus attributed most of the improved ewe lamb LWGs in our experiment to parasite dilution rather than to forage niche complementarity. In addition, the similar EPGs and LWGs observed in mixed-grazing suggest that the benefits of this practice can be obtained easily, i.e. over a wide range of sheep/cattle ratios. Based on the definition of the adjective operable (‘capable of being put into use, operation or practice’), we also conclude that mixed-grazing seems an operable practice from a biological viewpoint.

Forage quality of consecutive years interact to affect body condition, reproductive rate and rut phenology in Iberian red deer.

Body condition for reproduction in capital breeders such as the red deer (Cervus elaphus) is mostly determined by their stored energy reserves. Thus, environmental conditions and resource availability may affect reproductive performance and breeding success. In warm Mediterranean regions, current climate change is driving to a hotter and drier scenario that is expected to affect the biology and dynamics of many populations. We examined the impact of these local climate variations on red deer body condition and the relationship with female reproductive phenology and breeding success. We used satellite information of landscape vegetation along with a 22-year data series of direct field behavioural observations during the rutting season in Doñana National Park (SW Spain). We analyzed faecal nitrogen content (FN) from faeces collected during the rut. We found that poor vegetation availability in drier years was related to worse body condition of deer (measured by FN) and a delay in the rutting season, which associated with lower reproductive rates (measured by the proportion of females with calves observed the next year). We also evidenced an interesting interaction between environmental conditions in consecutive years on the timing of breeding season, with timing of breeding being more delayed when previous year resource availability was high and many females bred, and the consecutive one was poor, so females hardly recovered condition and the rut occurred later. These findings highlight the carry-over effect of reproduction in capital breeders and the potential impact of climate-change conditions on red deer breeding.

A skew in poo: Biases in primate fecal isotope analysis and recommendations for standardized sample preparation.

Feces are a treasure trove in the study of animal behavior and ecology. Stable carbon and nitrogen isotope analysis allows to assessthe dietary niches of elusive primate species and primate breastfeeding behavior. However, some fecal isotope data may unwillingly be biased towardthe isotope ratios of undigested plant matter, requiring more consistent sample preparation protocols. We assess the impact of this potential data skew in 114 fecal samples of wild bonobos (Pan paniscus) by measuring the isotope differences (Δ13 C, Δ15 N) between bulk fecal samples containing larger particles (>1 mm) and filtered samples containing only small particles (<1 mm). We assess the influence of fecal carbon and nitrogen content (ΔC:N) and sample donor age (subadult, adult) on the resulting Δ13 C, Δ15 N values (n = 228). Additionally, we measure the isotope ratios in three systematically sieved fecal samples of chimpanzees (Pan troglodytes verus), with particle sizes ranging from 20 μm to 8 mm (n = 30). We found differences in fecal carbon and nitrogen content, with the smaller fecal fraction containing more nitrogen on average. While the Δ13 C values were small and not affected by age or ΔC:N, the Δ15 N values were significantly influenced by fecal ΔC:N, possibly resulting from the differing proportions of undigested plant macroparticles. Significant relationships between carbon stable isotope ratios (δ13 C) values and %C in large fecal fractions of both age groups corroborated this assessment. Δ15 N values were significantly larger in adults than subadults, which should be of concern in isotope studies comparing adult females with infants to assess breastfeeding. We found a random variation of up to 3.0‰ in δ13 C and 2.0‰ in nitrogen stable isotope ratios within the chimpanzee fecal samples separated by particle sizes. We show that particle size influences isotope ratios and propose a simple, cost-effective filtration method for primate feces to exclude larger undigested food particles from the analysis, which can easily be adopted by labs worldwide.

Predicting the Feed Intake of Artificially Reared Pre-Weaned Lambs from Faecal and Dietary Chemical Composition

Predicting feed intake in suckling lambs consuming both milk and pasture can be challenging, and thus intake values are often derived from solely milk or solid feed consumption. The present study investigated if dry matter (DM), organic matter (OM), and metabolisable energy (ME) intakes of lambs given a combination of milk and pellets under controlled conditions could be predicted with enough precision using dietary and faecal chemical composition. A total of 34 pre-weaned lambs bottle-fed milk replacer with or without access to pellets and kept in metabolic cages for four days were used. To develop the prediction equations, 54 faecal samples with detailed information on their chemical compositions, and the feed consumed by the lambs, were used. Pellet DMI was predicted from neutral detergent fibre concentration in faeces and pellets, pellets %DM, and live weight (LW) of lambs. Milk DMI was predicted from faecal Nitrogen concentration and LW. Milk and pellet DMI and their ME content were combined to predict DMI/d and ME intake/d. The equations developed were validated against 40 spot faecal samples randomly selected from the lambs. DM, OM, and ME intakes were predicted with high accuracy and precision. The results showed that the developed equations can be used with enough accuracy to predict ME, OM, and DM intakes in pre-weaned lambs ingesting milk and pellets concurrently, thus the results revealed that the established equations may be used to predict ME, OM, and DM intakes in pre-weaned lambs drinking milk and pellets at the same time, allowing feeding regimens for young lambs to be developed.

Effects of Protein Restriction and Succedent Realimentation on Jejunal Function and Bacterial Composition of Different Colonic Niches in Weaned Piglets.

Recent studies have proved that protein succedent realimentation could rescue the loss of growth performance in weaning piglets caused by a prior protein restriction. However, how the protein restriction and succedent realimentation influence the jejunal function and bacterial composition of different colonic niches microbiota in weaning piglets needs a further investigation. After protein succedent realimentation, we found that the treatment group (TRE) piglets had a higher IGF-1 content and IGF-1R gene expression level in jejunal mucosa than the control group (CON) piglets. The ZO-1 gene expression level was up-regulated in the jejunal mucosa of TRE piglets during protein restriction and succedent realimentation, while the jejunal permeability of TRE piglets was only decreased after protein succedent realimentation. In addition, we found that protein restriction and succedent realimentation increased the gene expression of Pept-1 and the fecal apparent digestibility of crude protein in TRE piglets, but decreased the fecal nitrogen content. After 16S rRNA MiSeq sequencing of bacteria in different colonic niches (mucosa and digesta), TRE piglets had a higher relative abundance of beneficial bacteria and a lower relative abundance of potential pathogens than CON piglets in different colonic niches after protein restriction and succedent realimentation. Our data showed that protein restriction and succedent realimentation decreased the concentrations of branch chain fatty acids and ammonia-N in the colon of TRE piglets. In addition, protein succedent realimentation increased the concentration of total short chain fatty acids in the colon of TRE piglets. All these findings demonstrated that the strategy of protein restriction and succedent realimentation is an effective way to improve intestinal health of weaning piglets, and provided new insights into the nutrition management of piglets during the weaning period.

Exploring seasonal variation in the faecal glucocorticoid concentrations of African elephants (

Context The wide-ranging movement of African elephants (Loxodonta africana) is largely driven by the spatio-temporal distribution of water and forage, and often leads to their travelling outside of formally protected areas. With an increase in drier periods predicted across Africa due to climate change, it is critically important to understand how elephants physiologically respond to alterations in the availability and distribution of resources. Aims We assessed variation in the adrenal activity of elephants living in Kenya’s Tsavo East National Park between wet and dry seasons, as well as among individuals found in Tsavo East National Park and privately protected Rukinga Wildlife Sanctuary (part of the Kasigau REDD+ wildlife corridor) in the dry season, when the area experiences an influx of elephants in search of alternative resources. Methods We opportunistically collected fresh elephant faecal samples across the two seasons and locations for analysis of faecal glucocorticoid metabolite (fGCM, a proxy for stress) and nitrogen (Nf, an indirect measure of diet quality) concentrations. The Normalised Difference Vegetation Index (NDVI) was employed as an additional indicator of habitat quality. Key results In Tsavo East N.P. Nf and NDVI were both significantly lower during the dry season, indicating poorer habitat quality compared with the wet season. Although elephant fGCM concentrations tended to be higher in the dry season than the wet, the differences were not significant. There was no difference between elephant fGCMs measured in Tsavo East N.P. and Rukinga W.S. during the dry season, nor in habitat quality between the two locations. Conclusions Elephants living in Tsavo may be physiologically unaffected by (or adapt to) typical seasonal changes in habitat quality that could lead to nutritional stress; however, whether this is the case during extended periods of severe drought requires further investigation. Rukinga W.S. provides a safe haven of sufficient habitat quality for elephants searching for alternative resources during this period. Implications Extended dry periods are likely to become increasingly common in semiarid savannahs, and implications for wildlife must be closely monitored. Privately protected land outside formally protected areas plays an important role in conservation efforts, which should be considered when making land management plans.

Effects of Different Dietary Protein Levels on the Growth Performance, Serum Biochemical Parameters, Fecal Nitrogen, and Carcass Traits of Huanjiang Mini-Pigs.

The Huanjiang mini-pig is a Chinese local breed and, the optimal dietary crude protein (CP) level for this breed is still unknown. Therefore, the present study was conducted to investigate its optimum dietary CP level upon the growth performance, serum biochemical parameters, fecal nitrogen content, and carcass traits. Three independent trials with 360 pigs were included. A total of 220 pigs (5.32 ± 0.46 kg) were fed ad libitum, either a 14, 16, 18, 20, or 22% CP diet from about 5- to 10-kg (trial 1); 84 pigs (11.27 ± 1.43 kg) were fed either a 12, 14, 16, 18, or 20% CP diet from about 10- to 20-kg (trial 2); and 56 pigs (18.80 ± 2.21 kg) were fed either a 10, 12, 14, 16, or 18% CP diet from about 20- to 30-kg (trial 3). In trial 1, as dietary CP levels increased, the feed-to-gain ratio (F/G) quadratically decreased (p < 0.05) and was minimal at the 18.42% CP level. The average daily feed intake (ADFI) and final body weight (BW) were not affected by dietary CP levels while the fat percentage decreased (p < 0.05). Besides, a linear decrease in slaughter rate (p = 0.06) and a linear increase in bone percentage (p < 0.05), serum urea nitrogen (UN) (P < 0.05), and fecal nitrogen content (p = 0.07) of pigs were observed. In trial 2, as dietary CP levels increased, the average daily gain quadratically increased (p < 0.05) and was maximum at the 16.70% CP level. The slaughter rate linearly decreased (p < 0.05) whereas the skin rate, serum UN, and NH3-N increased (p < 0.05) linearly, as well as fecal nitrogen content (p = 0.06). In trial 3, as dietary CP levels increased, the F/G increased (p < 0.05), while the ADFI and ADG quadratically decreased (p < 0.05) and was maximum at nearly 14.00% CP level. The bone percentage and serum UN increased (p < 0.05) linearly but the slaughter rate decreased (P < 0.05) linearly, and the fecal nitrogen content quadratically decreased (p = 0.07) whereas the albumin increased (p < 0.05) quadratically. Taken together, the optimal dietary CP levels for growth performance of Huanjiang mini-pigs from 5- to 10-kg, 10- to 20-kg, and 20- to 30-kg were 18.42, 16.70, and 14.00%, respectively.

Animals connect plant species and resources in a meta-ecosystem

Movement of individuals and resources among habitat patches are key processes at the landscape scale. While these subsidies are primarily studied separately, coupled movement of species and resources, for example by animal vectors, may reinforce or dilute natural landscape heterogeneity, with consequences for the spatial distribution of biodiversity. We examine how transport of nutrients and seed by consumers’ feces corresponds to productivity gradients in the landscape, and whether herbivores and carnivores differ in the types of seeds they transport. In California, we surveyed fecal deposition by vertebrates in 10 serpentine grassland fragments of varying productivities. We analyzed nitrogen content of feces before performing a germination assay to identify species transported therein. Herbivores deposited substantial amounts of nitrogen in serpentine grasslands via their feces, while carnivore scat was a high-quality but less predictable resource subsidy. Neither trophic group’s fecal deposition reinforced or diluted productivity gradients in the landscape. Rather, unproductive fragments received minimal nutrients, while more productive fragments had the chance of receiving higher resource inputs. Feces from both types of consumers contained viable seeds, but herbivores and carnivores transported non-overlapping subsets of plant species. Consumers play different roles connecting plant communities in the landscape according to trophic level. Small herbivores are a continuous source of nutrient cycling, and their feces contains serpentine-adapted plant species, potentially serving as vectors for stepping-stone dispersal. While carnivores may be important vectors for long-distance seed dispersal, their movement patterns also make them more likely to deposit seeds in unsuitable environments.

Relationship between feed protein content and faeces nitrogen content in early lactation dairy cows

Submitted 2020-07-26 | Accepted 2020-09-02 | Available 2020-12-01 https://doi.org/10.15414/afz.2020.23.mi-fpap.313-318 The increase of milk production at the farm level requires an accurate balancing of the diet and the nitrogen supply also to minimise the possible environmental pollution deriving from dairy farming. The aim of this study was to evaluate dietary protein utilization at different crude protein (CP) levels and to predict nitrogen content in faeces on the basis of nutritional parameters and milk urea nitrogen content (MUN, mg dL -1 ). The study was conducted on three groups (A, B, C) of lactating dairy cows (8 cows per group, including Latvian Brown and Holstein Black and White breeds) from 10 to 30 days in milk. Total mixed rations containing different levels of CP (approximately 18.0%, 17.5% and 17.0% for A, B and C, respectively) were fed. The amount of feed consumed by each cow was measured and feed samples collected during the trial. Milk yield (kg d-1 -1 ) and faeces amount were recorded, and samples were collected at day 21 of the study for further analysis. Feed samples were analysed for CP, net energy for lactation (NEL, MJ kg -1 ) and other parameters. Milk samples were analysed for fat (%), total protein (%), casein (%) and urea content (mg dL -1 ). The statistical investigation was conducted using ANOVA, and correlation and regression analyses. The results showed that milk yield, fat, total protein, casein, urea, and MUN were not significantly different among groups being not affected by the dietary CP levels. The correlation between faecal nitrogen content and CP content in feed was moderately positive and statistically significant (r=0.44, P=0.03), while the correlation between faecal nitrogen content and MUN was moderately negative and showed tendency towards significance (r=-0.39, P=0.06). The regression analysis showed that feed CP explained approximately 20% of faeces nitrogen content. 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Feeding strategy, nitrogen cycling, and profitability of dairy farms. Journal of Dairy Science, 82, 2841-2855. https://doi.org/10.3168/jds.S0022-0302(99)75542-6 Spiekers, H. and Obermaier, A. (2007). Milchhrnstoffgehalt und N-Aussheidung.L SuB Heft 4-5/07, 2007. S. III-4 bis III-8. Straalen, W. M. (1995). Modelling of nitrogen flow and extraction in dairy cows. PhD thesis. Landbouw Universiteit Wageningen. ISBN 90-5485-475-8.

Determination of energy and protein requirements for maintenance and lactation of Dorper × Hu crossbred sheep

Abstract This study set out to define the energy and protein requirements for maintenance and lactation of Dorper☓Hu crossbred lactating ewes. Eighteen ewes of similar weight (53.37 ± 1.18 kg) were randomly divided into three groups after parturition: ad libitum (AL), IR70 % (intake restricted to 70 % of AL), and IR50 % groups (intake restricted to 50 % of AL). Energy, nitrogen, and carbon balance were calculated by determining the carbon or nitrogen content of orts, feces, urine, milk, CH4, and CO2 samples in digestibility and respiratory trials. Maintenance requirements of net energy [NEm; 257.04 ± 1.15, 252.35 ± 1.08, 244.34 ± 1.15 kJ/kg body weight (BW)0.75/day]; metabolizable energy (MEm; 353.29 ± 3.27, 352.16 ± 3.54, 354.97 ± 2.67 kJ/kg BW0.75/day); net nitrogen (NNm; 326 ± 110, 306 ± 81, 285 ± 77 mg/kg BW0.75/day); and net protein (NPm; 2.03 ± 0.17, 1.91 ± 0.28, 1.78 ± 0.28 g/kg BW0.75/day) were observed on 20th, 50th and 80th day of lactation. Compared with these results, the Wood’s model showed adequate estimates of peak yield (0.88 vs. 0.87 kg/day), but an overestimation of milk yield either side of the peak, and an underestimation of the timing of peak yield compared with the observed milk curve in the current study (4th vs. 3rd week of lactation, respectively). The corresponding NE requirements for lactation (NEL; MJ/kg milk) linearly increased with progressing lactation and were scaled from 3.76 to 4.19 (MJ/kg milk). Additionally, milk yield varied from 1–3 kg daily, and, from 20th to 80th day of lactation, the daily metabolizable protein (MP) requirement for lactation ranged from 141.14–283.43 g/day. The combined results suggest that the estimated MP and ME requirements for lactating Dorper and Hu crossbred sheep fell between the NRC recommendations for lactating ewes suckling a singleton and twin lambs.

Nutritional Quality Evaluation of a Pea Protein Isolate in Rats with or Without Amino Acid Supplementation (P08-064-19)

Abstract Objectives The global demand for protein is growing and it seems necessary to find new alternatives for animal proteins. Legumes are good candidates, as their indispensable amino acid (IAA) profile is relatively balanced. The aim of the study is to evaluate the nutritional quality of a pea protein isolate (NUTRALYS® pea protein), with or without methionine (Met) supplementation, using various indexes. We measured the Protein Efficiency Ratio (PER), the Digestible Indispensable Amino Acid Score (DIAAS) and the nitrogen balance in rats. Methods Study 1: 40 Wistar male rats weighing ∼50 g were fed ad libitum for 28 days with a diet containing 10% protein with variation in protein sources only. 5 groups (n = 8) were included: pea, casein, wheat gluten, pea-gluten combination, pea supplemented with Met. PER is obtained by the ratio between weight gain and protein intake throughout the experimental period. Study 2: 45 Wistar male rats weighing ∼250 g were housed in metabolic cages for 2 days and fed with a diet containing 14% protein of different sources. 5 groups (n = 9) were included: pea, casein, gluten, pea supplemented with Met, and protein-free diet for endogenous losses. Nitrogen content of diets, feces and urines was measured with an elementary analyzer for nitrogen balance (N ingested – N excreted). Then, rats were given a calibrated meal containing an indigestible marker and were euthanized 6 h later. Stomach, intestine, ileum, cecum, and colon contents were collected. DIAAS was calculated as follows: mg digestible IAA in 1 g of test protein*100/mg of IAA in 1 g of reference protein. IAA in ileum contents and diets were assayed by UPLC. Results Values are means ± SD. Met supplementation allows pea protein to reach the PER of casein, but association with gluten is not sufficient. Nitrogen balance values are higher for casein and pea + Met. Fecal digestibility of pea protein is higher than casein in our conditions. Analysis for DIAAS calculation are ongoing. Conclusions Pea protein is highly digestible in our conditions and Met supplementation can improve its capacity to insure growth. Funding Sources Roquette.

Linking diet quality and energy demand in free‐living guanacos: an eco‐physiological innovative approach

AbstractIn adaptive terms, animals are subject to challenges imposed by their environment. To address physiological patterns in wild mammals, the non‐invasive study of glucocorticoid hormones has become the main approach through two well‐defined conceptual frameworks: one is related to stress responses, whereas another refers to the glucocorticoids as physiological mediators of the allostatic load, necessary for the maintenance of homeostasis. A key factor to analyse the physiology of wild animals is to understand the relationship between energetic demands and nutritional attributes. The objective of this study was to assess the influence of diet quality on physiological mediators of energy mobilization in two populations of wild guanacos (Lama guanicoe) from Northern Patagonia. In order to evaluate energy mobilization and its relationship with diet quality, we quantified nitrogen content and cortisol metabolite concentrations in fresh faeces. Samples were collected in two contrasting seasons (summer and winter, representing the breeding and non‐breeding seasons respectively). Summer was identified as the period of highest diet quality and energy mobilization, in both sexes and populations. We found quadratic relationships between cortisol levels and nitrogen percentage, which we hypothesize corresponds to two different factors: one of an energetic‐nutritional nature (during winter, the non‐reproductive season), and the other of an energetic‐reproductive nature (during summer, the reproductive season). Our evidence suggests variation in the administration of energy resources in guanacos in response to internal and external stimuli, giving rise to a novel Biphasic Model of energy demand. Our results reinforce the knowledge of the adaptive eco‐physiological attributes of guanaco, and we describe a new conceptual model which explains the energy management patterns for this species and possibly for other ungulates, within the breeding and non‐breeding seasons.

Lower levels of glucocorticoids in crop‐raiders: diet quality as a potential ‘pacifier’ against stress in free‐ranging Asian elephants in a human‐production habitat

AbstractOverlapping habitats and sharing of resources between elephants and people has led to intense elephant‐human conflicts, especially crop depredation by elephants, across elephant‐range countries. While raiding agricultural crops, elephants face numerous threats from people through chase, injury and the risk of death which could enhance the associated energetic costs, ultimately elevating their stress levels. We hypothesized that crop‐raiders (in the human‐production habitat) would show higher faecal glucocorticoid metabolite (fGCM) levels, a proxy of stress‐response, as compared to nonraiders (in protected forests). To study this, 208 faecal samples were collected from crop‐raiding elephants in a human‐production habitat and 394 samples from nonraiding elephants in protected forests during 2013 and 2015. Contrary to our expectation, fGCM levels were significantly higher in nonraiding than in crop‐raiding elephants of both sexes. As one of the possible factors for lower fGCM in elephants inhabiting the human‐production habitat, the influence of benefits obtained from foraging here was assessed. For this, the difference in vegetation greenness (standing biomass) between the human‐production habitat and the protected forests was analysed from remotely‐sensed Normalized Differential Vegetation Index (NDVI), and further confirmed by measuring dietary quality (faecal nitrogen (N) content and C:N ratio as proxies for crude protein). Interestingly, higher NDVI values (greater biomass availability), higher N content and lower faecal C:N ratio (indicating higher protein content in the diet) of elephants in the human‐production habitat suggested enhanced nutritional levels here as compared to protected forests. Further, there were significant correlations between faecal C:N ratio (positive) or N content (negative) and fGCM levels. These findings suggest that crop‐raiding comes with the benefits of a superior quality diet which may help in reducing human‐induced stress‐response in elephants inhabiting or foraging within human‐production habitats.

Determining changes in the nutritional condition of red deer in Mediterranean ecosystems: Effects of environmental, management and demographic factors

Monitoring changes in the nutritional status of wild populations is crucial to understanding how species respond to natural or human-mediated variations in food availability and quality. It is a fundamental step for decision-making in wildlife management. Many studies on nutritional ecology still tend to rely on the use of single indicators. Nonetheless, nutrition has multiple interdependent facets that should be combined to better understand how organisms interact with their environment through feeding. Here, data from a large-scale cross-sectional survey conducted between 2010 and 2013 were used to examine the influence of environmental conditions and management practices on the variation of faecal nitrogen content (FN, index of dietary quality) and kidney fat index (KFI, indicator of nutritional condition) in red deer Cervus elaphus in the Mediterranean ecosystems of Iberia. Variations in the nutritional indicators in relation to sex, age, faecal fibre contents and faecal counts of lungworm larvae were also analysed. Our results showed that FN levels were statistically and positively correlated with vegetation primary productivity (P = 0.003). In contrast, faecal fibre fractions were significantly and negatively correlated with FN concentrations (P = 0.024 for hemicellulose, P < 0.0001 for cellulose and lignin). Moreover, a negative, marginally significant relationship was found between FN and the average altitude of the study areas (P = 0.055). The KFI was statistically higher in females than in males (P < 0.0001) and increased with increasing FN levels (P = 0.01). Fat stores were also statistically and positively correlated with vegetation productivity (P = 0.001) and with the amount of supplementary food provided (P = 0.04). The effect of high-quality diets on deer kidney fat deposits was gradually lower as the population density increased (P = 0.02). This result was more marked in non-food-supplemented populations. Both FN and KFI were statistically higher during the winter in relation to the autumn (P < 0.0001 and P = 0.005, respectively). This study shows that FN can be used to monitor and predict changes in the dietary quality, and the KFI in the nutritional status, in red deer in Mediterranean environments, reliably. Since both indicators showed different sensitivity to intrinsic, ecological and management determinants, this research also highlights their value and complementary use when studying populations of large wild herbivores.

Low-protein diets with balanced amino acids reduce nitrogen excretion and foot pad dermatitis without affecting the growth performance and meat quality of free-range yellow broilers

An experiment was conducted to evaluate the effects of crude protein (CP) levels on growth performance, carcase quality, meat quality, immune indices, litter and faeces quality, as well as welfare quality, in free-range yellow broilers using balanced amino acid technology. In total, 600 one-d-old Suqin yellow broilers were raised for 21 d. On d 22, 540 birds with similar BW (390 ± 7 g SD) were randomly selected and placed into 9 pens (3 groups with 3 replicates per group and 60 birds each replicate) and then reared to 56 d of age. The birds were fed a diet containing CP 19% (control), 18% or 17% (measured value: 18.878%, 17.881%, 17.052%, respectively), in three groups for 35 d. The results revealed that decreasing dietary CP levels from 19% to 17% had no impact on broiler growth performance, carcase quality and meat quality (p > .05). The relative immune organ weights also showed no change to the lowering of dietary CP levels (p > .05), whereas serum albumin was significantly influenced by decreasing dietary CP levels (p = .042). Furthermore, nitrogen content in litter and faeces, as well as the footpad dermatitis score for welfare indices, were decreased with decreased dietary CP levels (p = .009, p = .014, p = .045, respectively). The results of this study suggest that low-protein diets with balanced amino acids reduce nitrogen excretion and footpad dermatitis without effecting the performance, carcase quality, and meat quality of free-range yellow broilers.