Nine hybrids (three maturity groups, dry matter 343 ± 5.6 g/kg) of whole‐crop maize were ensiled in eight replicates in laboratory‐scale silos. Each hybrid was sampled at harvest and after 30, 60, 90 and 120 days (d) of ensiling. Samples were analysed for chemical composition (proximate constituents, fermentation products and pH), starch, non‐protein N (NPN) and NH3‐N. Each sample and its neutral detergent fibre (NDF) fraction were incubated in the Hohenheim gas test system. In vitro gas production was measured after 0, 2, 4, 8, 12, 16, 24, 36, 48, 72 and 96 hr of incubation. Gas production of the neutral detergent soluble (NDS) fraction (mainly starch) was calculated using a curve subtraction method. Gas production dynamics over time were estimated using a nonlinear regression equation; afterwards, a two‐factorial analysis of variance (storage length, maturity group and their interaction) using the general linear models procedure was conducted. After 30 d, all silages were well fermented. Most fermentation products and proximate constituents only changed until 30 or maximum 60 d of ensiling. Only few changes in in vitro nutrient degradability were detected after the first 30 d or as influenced by maturity group. Ensiling per se increased the ruminal degradability of the NDS, but there was no further increase caused by a prolonged duration of storage. However, extensive changes in crude protein fractions occurred with a linear increase in NPN and NH3‐N compounds from 0 to 120 d of storage, indicating continual protein and amino acid degradation.

The objectives of this study were to analyze whether dry matter intake (DMI), water intake (WI) and BW were influenced by estrus. A second objective was to determine whether correlations exist among these traits in non-estrous days. Data collection included 34 Holstein-Friesian cows from the research farm 'Haus Riswick' of the Agricultural Chamber North Rhine-Westphalia, Germany. On an individual basis, daily DMI and daily WI were measured automatically by a scale in the feeding trough and a WI monitoring system, respectively. BW was determined by a walk-through scale fitted with two gates -one in front and one behind the scale floor. Data were analyzed around cow's estrus with day 0 (the day of artificial insemination leading to conception). Means during the reference period, defined as days − 3 to − 1 and 1 to 3, were compared with the means during estrus (day 0). DMI, WI and BW were affected by estrus. Of all cows, 85.3% and 66.7% had reduced DMI and WI, respectively, on day 0 compared with the reference period. Lower BW was detected in 69.2% of all cows relative to the reference period. During the reference period, average DMI, WI and BW were 23.0, 86.6 and 654.8 kg. A minimum DMI of 20.4 kg and a minimum BW of 644.2 kg were detected on the day of estrus, whereas the minimum WI occurred on the day before estrus. After estrus, DMI, WI and BW returned to baseline values. Intake of concentrated feed did not seem to be influenced by estrus. Positive correlations existed between daily DMI and daily WI (r = 0.63) as well as between cows' daily BW and daily WI (r = 0.23). The results warrant further investigations to determine whether monitoring of DMI, WI and BW may assist in predicting estrus.

The objective of this study was to evaluate the effect of supplemented condensed tannins (CT) from the bark of the Black Wattle tree (Acacia mearnsii) on production variables and N use efficiency in high yielding dairy cows. A feeding trial with 96 lactating German Holstein cows was conducted for a total of 169 days, divided into four periods. The animals were allotted to two groups (control (CON) and experimental (EXP) group) according to milk yield in previous lactation, days in milk (98), number of lactations and BW. The trial started and finished with a period (period 1 and 4) where both groups received the same ration (total-mixed ration based on grass and maize silage, ensiled sugar beet pulp, lucerne hay, mineral premix and concentrate, calculated for 37 kg energy-corrected milk). In between, the ration of EXP cows was supplemented with 1% (CT1, period 2) and 3% of dry matter (DM) (CT3, period 3) of a commercial A. mearnsii extract (containing 0.203 g CT/g DM) which was mixed into the concentrate. In period 3, samples of urine and faeces were collected from 10 cows of each group and analyzed to estimate N excretion. Except for a tendency for a reduced milk urea concentration with CT1, there was no difference between groups in period 2 (CON v. CT1; P>0.05). The CT3 significantly reduced (P<0.05) milk protein yield, the apparent N efficiency (kg milk N/k feed N) and milk urea concentration; but total milk yield and energy-corrected milk yield were not affected by treatment. Furthermore, as estimated from 10 cows per group and using urinary K as a marker to estimate the daily amount of urine voided, CT3 caused a minor shift of N compounds from urine to faeces, as urea-N in urine was reduced, whereas the N concentration in faeces increased. As an improvement in productivity was not achieved and N use efficiency was decreased by adding the CT product it can be concluded that under current circumstances the use in high yielding dairy cows is not advantageous.

Simple SummaryDefined criteria for the application of the CO2 balance method in a naturally ventilated barn provided reliable data. This specification enabled the acquisition and quantification of CH4 and NH3 in a naturally ventilated dairy barn, as well as detecting decreasing NH3 emissions affected by supplementing an Acacia mearnsii condensed tannin extract to a dairy cattle ration. Moreover, long-term measurements were possible and can be used to examine feed-related mitigation strategies at a barn level in the future.AbstractExtensive experimentation on individual animals in respiration chambers has already been carried out to evaluate the potential of dietary changes and opportunities to mitigate CH4 emissions from ruminants. Although it is difficult to determine the air exchange rate of open barn spaces, measurements at the herd level should provide similarly reliable and robust results. The primary objective of this study was (1) to define a validity range (data classification criteria (DCC)) for the variables of wind velocity and wind direction during long-term measurements at barn level; and (2) to apply this validity range to a feeding trial in a naturally cross-flow ventilated dairy barn. The application of the DCC permitted quantification of CH4 and NH3 emissions during a feeding trial consisting of four periods. Differences between the control group (no supplement) and the experimental group fed a ration supplemented with condensed Acacia mearnsii tannins (CT) became apparent. Notably, CT concentrations of 1% and 3% of ration dry matter did not reduce CH4 emissions. In contrast, NH3 emissions decreased 34.5% when 3% CT was supplemented. The data confirm that quantification of trace gases in a naturally ventilated barn at the herd level is possible.

This study elucidated the effects of limited concentrate feeding on growth, nutrient digestibility, blood profile and gene expression of gluconeogenic enzymes in the liver of dairy calves. The study utilized 36 German Holstein dairy calves (5-7 days of age) divided into two groups of 18 calves each for 150 days. Control group calves received 2 kg/(calf × day) of concentrate, whereas calves in the restricted group received only 1 kg/(calf × day). Good quality forage (mixture of maize and grass silages) was available for ad libitum consumption to both groups. The intake of milk replacer before weaning, and of concentrate were recorded daily per calf; however, the consumption of forages was quantified as daily average of the group. Body weights (BW) were recorded at start and on days 35, 70, 112 and 150. Blood and serum samples and spot urinary and faecal samples were also collected at similar time points. On days 70 and 150, liver biopsies were collected from seven animals in each group. The BW was not different between the groups at all times. Total BW gain in the control group was 124 kg as opposed to 111 kg in restricted group that led to average BW gain of 827 g/day and 739 g/day in respective groups, and the differences were significant (p = 0.018). As planned, the control group had higher concentrate and lower forage intake than the restricted group. The blood haemoglobin, haematocrit and serum variables (glucose, total protein, albumin and urea) were within the normal range in both groups, but serum glucose was higher (p < 0.05) in control than in restricted group at 70 days. There was no difference between groups in organic matter (OM) digestibility which declined (p < 0.001) with increasing age in both groups. Microbial crude protein (MCP) synthesis estimated from urinary allantoin excretion increased (p < 0.001) in both groups with increasing age but was not different between groups. The mRNA expressions for the gluconeogenic enzymes, cytosolic and mitochondrial phosphoenol pyruvate carboxykinase (EC 4.1.1.32) and pyruvate carboxylase (EC 6.4.1.1) measured by quantitative real-time PCR in liver biopsies showed no differences between groups. Overall, restricting concentrate moderately reduced the growth intensity without affecting the normal serum and blood indices, and MCP synthesis and OM digestibility showed no differences between groups, indicating that both concentrate feeding schemes can be successfully applied.

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Techniques that allow direct measurements on animals to quantify methane (CH4) emissions are costly and difficult to transfer to herd level. Mathematical approaches have been developed to predict methane emissions of cattle based on diet and intake characteristics, which were calibrated against largely varying calorimetry data. In this study, nine CH4 prediction equations were applied to five typical Central European dairy cow diets in order to compare their applicability. The five diets differed in respect of forage proportion and type. In a first attempt, regression equations were selected containing easily accessible data such as dry matter intake (DMI, kg/d) forage proportion, as well as neutral and acid detergent fibre that can also be extracted from on-farm datasets. Smallest differences to mean values were observed with the application of equations using neutral detergent fibre, while standard deviations were highest. Therefore, the best capability to differentiate between diets was shown, when using equations that operated with forage proportion and DMI. Nevertheless, the role of CH4 prediction equations should not be overestimated. The differences in CH4 estimates show that frequently used equations are still inaccurate and may only serve as implications to locate trends. It should be taken into consideration to expand datasets, involving future CH4 measurements, on animal and herd level, feeding typical, up-to-date regional diets in order to get more precise equations, suitable for a greater range of estimations. To ease and simplify the future applications, the prediction equations could be classified into groups, clearly stating by which data they were derived, for example, regional origin and diet composition.

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