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The optimal protein intake for elderly individuals who exercise regularly has not yet been clearly defined. The aim of this study was to test the hypothesis that protein intake level is associated with muscle strength in elderly elite athletes. We evaluated 50 elite senior athletes (38 men and 12 women) participating in the European Master Games 2011 in an observational cross-sectional study. Participants were divided into two groups—lower (LPI) or higher (HPI) protein intake—according to the median value of their ratio of urinary urea nitrogen to urinary creatinine (i.e., 8.8 g/L), as a marker of protein intake. A dietary interview confirmed differences in protein consumption between the LPI and HPI groups. We also evaluated body composition (bioimpedance), muscle strength, and hematochemical indices. LPI and HPI groups were homogeneous for age (72 [68–74] and 71 [68–74] y, respectively), fat-free mass index (18.4 [17–19.4] and 18.2 [17–19.1] kg/m2), body fat (18.3% [12.3–20.7%] and 16.6% [13.6–21.2%]), and glomerular filtration rate (57.7 [53.8–64.9] and 62.7 [56.1–69.3] mL/min/1.73 m2). The HPI group showed greater leg and trunk muscle strength (N) compared with the LPI group (left leg extension, 339 [238–369] versus 454 [273–561], respectively, P < 0.05; right leg extension, 319 [249–417] versus 432 [334–635], P ≤ 0.05; trunk extension, 435 [370–467] versus 464 [390–568], P ≤ 0.05). Higher protein intake in elite senior athletes is associated with a greater muscle strength. •Optimal protein intake for elderly individuals who exercise regularly is examined in this study.•Master senior athletes are suitable models for the assessment of the effects of different levels of protein intake.•Protein intake was associated with physical performance and biochemical parameters.•A higher protein intake in elite senior athletes is associated with a greater muscle strength.

We assessed the interactive effects of gross feed use efficiency (FUE, milk yield/kg DMI) background (“high” = HEFF vs. “low” = LEFF) and graded levels of dietary CP (130, 145, 160, and 175 g/kg DM) on milk production, enteric methane (CH4) emission, and apparent nitrogen use efficiency (NUE, g milk protein nitrogen/g nitrogen intake) with Norwegian Red (NRF) dairy cows. Eight early- to mid-lactation cows were used in a 4 × 4 Latin square design experiment (2 efficiency backgrounds, 4 dietary treatments, and 4 periods each lasting 28 d). The diets were designed to be identical in physical nature and energy density, except for the planned changes in CP, which was a contribution of slight changes in other dietary constituents. We hypothesized that HEFF cows would partition more dietary energy and nitrogen into milk components and, as such, partition less energy in the form of methane and excrete less nitrogen in urine and feces compared with their LEFF contemporaries. We observed no interactions between dietary CP level and efficiency background on DMI, other nutrient intake, NUE, CH4 emission, and its intensity (g CH4/kg milk). Gradually decreasing dietary CP from 175 to 130 g/kg DM did not affect DMI, milk and energy-corrected milk yield, and milk component yields and daily CH4 emission. However, decreasing dietary CP increased NUE and reduced urinary nitrogen (UN) excretion both in quantitative terms and as proportion of nitrogen intake. The HEFF cows showed improved NUE and decreased CH4 emission intensity compared with the LEFF cows. In the absence of interaction effects between efficiency background and dietary CP level, our results suggest that CH4 emission intensity and UN excretions can be reduced by selecting dairy cows with higher FUE and reducing dietary CP level, respectively, independent of one another. Furthermore, UN excretion predictions based on milk urea nitrogen (MUN) and cow BW for NRF cows produced very close estimates to recorded values promising an inexpensive and useful tool for estimating UN excretion under the Nordic conditions where ordinary milk analysis comes with MUN estimates.

Nitrogen (N) leached into groundwater from urine patches of cattle grazing in situ is an environmental problem in pasture-based dairy industries. One potential mitigation is to breed cattle for lower urinary nitrogen (UN) excretion. Urinary nitrogen is difficult to measure, while milk urea nitrogen concentration (MUN) is relatively easy to measure. For animals fed diets of differing N content in confinement, MUN is moderately heritable and is positively related to UN. However, there is little information on the heritability of MUN, and its relationship with other traits such as milk yield and composition, for animals grazing fresh pasture. Milk urea nitrogen concentration data together with milk yield, fat, protein and lactose composition and somatic cell count was collected from 133 624 Holstein-Friesian (HF), Jersey (J) and HF×J (XBd) cows fed predominantly pasture over three full lactations and one part lactation. Mean MUN was 14.0; and 14.4, 13.2 and 13.9 mg/dl for HF, J and XBd cows, respectively. Estimates of heritability of MUN were 0.22 using a repeatability model that fitted year-of-lactation by month-of-lactation by cow-age with days-in-milk within month-of-lactation and cow-age, and 0.28 using a test-day model analysis with Gibbs sampling methods. Sire breeding values (BVs) ranged from −2.8 to +3.2 indicating that MUN could be changed by selection. The genetic correlation between MUN and percent true protein in milk was −0.22; −0.29 for J cows and −0.16 for HF cows. Should the relationship between MUN and UN observed in dietary manipulation studies hold similarly when MUN is manipulated by genetic selection, UN excretion could be reduced by 6.6 kg/cow per year in one generation of selection using sires with low MUN BVs. Although J cows had lower MUN than HF, total herd UN excretion may be similar for the same fixed feed supply because more J cows are required to utilise the available feed. The close relationship between blood plasma urea N concentration and MUN may enable early selection of bulls to breed progeny that excrete less UN.

Nitrogen content in urine plays a crucial role in assessing the environmental impact of dairy farming. Urine acidifications avoid urine nitrogen volatilization, but potentially lead to a degradation of creatinine, the most dependable marker for quantifying total urine excretion volume, affecting its measurement. This study aimed to assess how acidifying urine samples affects the concentration and detection of creatinine in dairy cattle. In this trial, individual urine samples from 20 Holstein lactating dairy cows were divided into three subsamples, allocated to 1 of 3 groups consisting of 20 samples each. Samples were immediately treated as follows: acidification with H2SO4 (1 mL of acid in 30 mL of sample) to achieve a pH < 2 (Group 1)); addition of an equal volume of distilled water (1 mL of distilled water in 30 mL of sample) to investigate dilution effects (Group 2); or storage without any acid or water treatment (Group 3). An analysis of creatinine levels was carried out using the Jaffe method. The Friedman test was employed to compare urine groups across treatments, and the Bland–Altman test was used to assess the agreement between measurements in Group 1 and Group 3. Urinary creatinine values were statistically different (p < 0.001) between Group 1 (median 48.5 mg/dL; range 36.9–83 mg/dL), Group 2 (median 47.5 mg/dL; range 36.5–80.7 mg/dL), and Group 3 (median 48.9 mg/dL, range 37.2–84). Bland–Altman analysis demonstrates agreement between Group 3 and Group 1. The measurement of urinary creatinine using the Jaffe method is affected by sample acidification, but the use of creatinine as a marker for total urine output could remain a viable tool when urine samples are acidified.

ABSTRACT Evaluating impact of animal agriculture on air quality has been the focus of recent research. Ammonia (NH3) volatilization occurs when undigested protein in feces and urea in urine is broken down by bacteria and enzymes. Information regarding NH3 emission from equine facilities is limited, and effects of CP intake on NH3 emissions have not been investigated. Nine mature geldings were used in a 3 × 3 replicated Latin square design study to determine effects of dietary CP on potential NH3 losses from feces and urine. We hypothesized feeding horses above the CP requirement would result in an increase in NH3 emissions from urine and feces and different bedding materials would affect NH3 emissions from urine. Diets were formulated using different ratios of bahiagrass (Paspalum notatum) and Tifton-85 bermudagrass (Cynodon dactylon) hays, and a commercial vitamin mineral supplement to provide 3 different CP concentrations and labeled in relation to each other: LOW-CP, MED-CP, and HIGH-CP (10.6%, 11.5%, and 12%, respectively). Each study period consisted of an 11-d diet adaptation phase, followed by a 3-d total collection of urine and feces. To determine total nitrogen (TN) and urea-N concentrations, samples were pooled by period (n = 9). For in vitro determination of NH3 concentrations, urine and fecal samples were pooled within period by diet (n = 3) and mixed with either wheat straw or wood shavings. Ammonia emission of these samples was measured using a vessel system with an airflow rate (2.5 L/min) at 20°C over a 7-d period. Concentration of NH3 in each vessel was measured using a photoacoustic multigas analyzer. Temperature, airflow rate, and NH3 concentration in each vessel were used to calculate NH3 emission rate (ER). Data were analyzed using a mixed model ANOVA with repeated measures. Urinary TN and urea-N excretion increased as CP intake increased (P < 0.0001). Vessel urinary NH3 concentrations were not different across diets (P = 0.1225), ranging from 55.48 ppm (LOW-CP) to 101.14 ppm (HIGH-CP); however, they differed between bedding types (P < 0.0001), with straw higher than shavings (97 vs. 73.5 ppm, respectively). Cumulative urinary NH3 ER tended to be different across diets (P = 0.0550) ranging from 5.87 g/m2 to 9.97 g/m2 and bedding types (P = 0.0129), with straw being higher than shavings (11.1 vs. 6.9 g/m2, respectively). Overfeeding CP to horses can lead to increased urinary TN and urea-N excretion, which could lead to greater of NH3 in the atmosphere.

The societal pressure on intensive pastoral dairying demands the search for strategies to reduce the amount of N flowing through and excreted by dairy cows. One of the strategies that is being currently explored focuses on the animal as a solution, as there are differences in N metabolism between cows even within the same herd. This work was conducted to explore such an approach in A1PF herds in New Zealand and the possibility of identifying A1PF cows that are divergent for milk urea nitrogen (MUN) concentration through phenotyping as a potential viable strategy to reduce N leaching and emissions from temperate dairy systems. Three herd tests were conducted to select a population sample of 200 cows (exhibiting the lowest 100 and highest 100 MUN concentrations). Milk samples were collected from the 200 cows during mid and late lactation to test for milk solids content and MUN. From the 200 cows, urine for urinary N concentration (UN), blood for plasma urea N, total antioxidants (TAS), and glutathione peroxidase (GPx) were collected from the 20 extremes (the lowest 10 and highest 10 MUN concentrations). Milk urea N was greater in cows selected as high-MUN cows (16.2 vs. 14.32 ± 0.23 mg/dL) and greater during late lactation (16.9 vs. 13.0 ± 0.19 mg/dL). Milk solids and fat content were 38% and 20% greater in cows selected as low-MUN cows than in high-MUN cows during mid lactation (p < 0.001). Low-MUN cows had lower UN than high-MUN cows during mid lactation (0.64 vs. 0.88 ± 0.11%). The N concentration in the plasma (p = 0.01) and Tas (p = 0.06) were greater during late lactation. There was a positive relationship between the MUN concentration phenotype used for selection and the MUN concentration for the trial period and MUN concentration and UN concentration during mid and late lactation (p < 0.001). Our results suggest that A1PF cows within a commercial herd can be phenotyped and selected for low-MUN, which may be potentially a viable strategy to reduce N losses to the environment and create healthier systems. Following genetic tracking, those cows can be bred to further promote low-MUN A1PF herds.

Improving sustainability in agricultural systems depends on increasing the efficiency of nitrogen (N) use and recycling. This study evaluated whether animal supplementation and legume-based pastures can enhance N balance and residual N availability in an integrated crop-livestock system (ICLS). The experiment was conducted in two phases—livestock and cropping—using three treatments: a control pasture (oat + ryegrass), a legume mixture (oat + ryegrass + arrowleaf clover), and a supplementation treatment (oat + ryegrass with concentrate supplementation at 1% of live weight), each replicated three times. Soybeans were grown during the cropping phase. Supplementation increased the stocking rate by 21%, while both supplementation and legumes led to a 30% increase in residual N returned via feces and urine, without negatively affecting soybean yield (~4.1 Mg ha−1). N off-take by soybean grain was approximately 9% higher in these treatments, while N exported via cattle carcasses remained unchanged across treatments, averaging 8.2 kg ha−1. Overall, soybeans accounted for 96–97% of total N export, and animals for only 3–4%. These results demonstrate that animal supplementation and legume integration enhance N use efficiency and contribute to nutrient recycling in ICLS, offering a viable strategy to reduce dependence on synthetic fertilizers. The findings support the development of more sustainable livestock and crop systems by maximizing nutrient retention, maintaining yield, and improving soil fertility. Furthermore, the implications for soybean yield and the sustainability of livestock systems indicate a potential positive economic and environmental impact for producers and policymakers.

Objective: The study aimed to quantify milk production and urinary nitrogen (UN) excretion of dairy cows grazing pastures containing varying amounts of plantain (Plantago lanceolata) in different seasons, under a typical farm practice.Methods: Four pasture treatments: perennial ryegrass (Lolium perenne) – white clover (Trifolium repens) (RGWC), RGWC + low plantain rate, RGWC + medium plantain rate, and RGWC + high plantain rate, were established in four adaptation areas (1 ha each) and 20 experimental plots (800 m2 each), and rotationally grazed by dairy cows over 14 grazing events during two lactation years. In each grazing (8 to 9 days), 60 or 80 Jersey-Friesian lactation cows were assigned to their pasture treatments, adapted to their pastures over the first six days, then each group of 15 or 20 cows were randomly allocated for grazing in five treatment plots over a two or three-day measurement period. Milk, urine, and faecal samples were collected from individual cows during the measurement period.Results: The pasture treatments did not affect milk production, the yield and composition of milk solids, protein, fat, and lactose. However, cows grazing pastures containing between 17% and 28% dietary plantain reduced UN concentration by 15% to 27%, decreased UN excretion by 4% to 9%, and increased urine volume by 22% to 40%, compared to grazing the RGWC pasture. The change in UN concentration, and urine volume were associated with plantain proportion in the diet and were greater during late summer and autumn than during early summer.Conclusion: Incorporating 17% to 28% dietary plantain with RGWC pastures can reduce the risk of nitrogen losses from pastoral systems, while maintaining the milk production of dairy cows.

The objectives of this study were two-fold. Firstly, to estimate the likely correlated responses in milk urea nitrogen (MUN) concentration, lactation yields of milk (MY), fat (FY) and crude protein (CPY) and mature cow liveweight (LWT) under three selection scenarios which varied in relative emphasis for MUN; 0% relative emphasis (MUN0%: equivalent to current New Zealand breeding worth index), and sign of the economic value; 20% relative emphasis positive selection (MUN+20%), and 20% relative emphasis negative selection (MUN−20%). Secondly, to estimate for these three scenarios the likely change in urinary nitrogen (UN) excretion under pasture based grazing conditions. The predicted genetic responses per cow per year for the current index were 16.4 kg MY, 2.0 kg FY, 1.4 kg CPY, −0.4 kg LWT and −0.05 mg/dL MUN. Positive selection on MUN in the index resulted in annual responses of 23.7 kg MY, 2.0 kg FY, 1.4 kg CPY, 0.6 kg LWT and 0.10 mg/dL MUN, while negative selection on MUN in the index resulted in annual responses of 5.4 kg MY, 1.6 kg FY, 1.0 kg CPY, −1.1 kg LWT and −0.17 mg/dL MUN. The MUN−20% reduced both MUN and cow productivity, whereas the MUN+20% increased MUN, milk production and LWT per cow. Per cow dry matter intake (DMI) was increased in all three scenarios as milk production increased compared to base year, therefore stocking rate (SR) was adjusted to control pasture cover. Paradoxically, ten years of selection with SR adjusted to maintain annual feed demand under the MUN+20% actually reduced per ha UN excretion by 3.54 kg, along with increases of 63 kg MY, 26 kg FY and 16 kg CPY compared to the base year. Ten years of selection on the MUN0% index generated a greater reductions of 10.45 kg UN and 30 kg MY, and increases of 32 kg FY and 21 kg CPY per ha, whereas the MUN−20% index reduced 14.06 kg UN and 136 kg MY with increases of 32 kg FY and 18 kg CPY compared to base year. All three scenarios increased partitioning of nitrogen excreted as feces. The selection index that excluded MUN was economically beneficial in the current economic circumstances over selection indices including MUN regardless of whether selection was either for or against MUN. There was no substantial benefit from an environmental point of view from including MUN in the Breeding Worth index, because N leaching is more a function of SR rather than of individual cow UN excretion. This study demonstrates that attention needs to be paid to the whole system consequences of selection for environmental outcomes in pastoral grazing circumstances.

Urinary nitrogen (N) excretion (UN) as a proportion of N intake (NI; UN/NI) is a major determinant of N excretion from ruminants and could be predicted from the N isotopic discrimination occurring between dietary and animal proteins (Δ 15 N). This study investigated the usefulness of Δ 15 N and other plasma biomarkers to reflect changes in UN/NI from sheep offered different levels of dietary urea. Eighteen Merino rams (age, 1–2 years; live weight, 41 ± 3 kg) were allocated to three dietary N treatments for a N balance study. Treatments were control (C), control + 0.5% urea (C+0.5%), and control + 1.2% urea (C+1.2%) and designed to provide maintenance, maintenance plus an additional 15%, and maintenance plus an additional 33% NI, respectively. The urea effect term was used for one-way ANOVA and regression analysis. As NI increased, the UN and retained N (RN) increased linearly ( p < 0.001), but UN/NI only increased in treatment C+1.2% compared with C ( p < 0.05). Plasma Δ 15 N was positively and significantly correlated with UN and UN/NI ( r = 0.52, p = 0.028; and r = 0.68, p = 0.002, respectively) and increased linearly ( p < 0.001) with the highest values observed in C+1.2%. Urine δ 15 N changed linearly between C and C+1.2%, but plasma δ 15 N increased quadratically ( p < 0.05). Plasma urea N increased in a linear way across dietary urea levels ( p < 0.001). The N isotopic difference between plasma and urine (plasma δ 15 N–urine δ 15 N) of C did not vary from either of the other treatments; however, it differed between C+0.5% and C+1.2% ( p < 0.05). The study confirmed the potential usefulness of plasma Δ 15 N to estimate UN/NI from sheep. Moreover, plasma δ 15 N–urine δ 15 N can be proposed as a new biomarker of N excretion from small ruminants. These approaches, however, need to be tested in various study conditions.