Evaluation of Herbage Intake Estimation Methods for Dairy Cattle Grazing on Semi-Extensive Pastures

Available empirical and mechanistic models to estimate total dry matter intake (DMI) and pasture dry matter intake (PDMI) of grazing lactating dairy cows have mainly been developed under intensive grazing conditions. The objective was to evaluate the adequacy of such existent models for use under semi-extensive grazing conditions, characterised by semi-natural grassland and less intensive resource use. Feed intake of lactating cows was measured on three commercial organic dairy farms in South Germany during one or two 6-d-periods/farm in 2019. Each period, DMI was determined in 10 or 20 cows per farm from their daily faecal output measured using titanium dioxide as marker and the apparent total tract digestibility of ingested organic matter derived from faecal crude protein concentration. PDMI was then calculated by subtracting weighed DMI of supplement feeds from total DMI. Further, individual milk yield and body weight were recorded, and samples of milk, pasture forage, supplement feed, and faeces were taken. For further analysis, means of observed values per farm and period (n = 7) were used, resulting in a diverse dataset of grazing systems differing in supplement feeding, daily pasture allocation, cow breed, and PDMI. Two semi-mechanistic PDMI models and six empirical and two semi-mechanistic models to predict total DMI were evaluated by their Mean Squared Error of Prediction, Relative Prediction Error (RPE) and Concordance Correlation Coefficient. One PDMI model produced acceptable (RPE \u3c 20% of mean observed PDMI), and four total DMI models yielded satisfactory (RPE \u3c 10%) prediction accuracy, however yet at a moderate precision (greatest Pearson correlation coefficient = 0.73). To further specify the grazing conditions under which the models reach both, satisfactory precision and accuracy, and due to the low number of observations, data of the present study will be complemented with data gathered on more farms in Southwest Germany in 2020

Corrigendum to “A new approach for improving emission factors for enteric methane emissions of cattle in smallholder systems of East Africa – Results for Nyando, Western Kenya” [Agricultural systems volume (161) pp72–80]

The authors regret that a recent examination of our data for other purposes has led to the discovery of an error in the calculation of the Metabolic Energy Requirement for maintenance (MERm) in the original calculations of this article. This was occasioned by the application of an incorrect constant to the calculation of MERm to male animals >2 yrs., male animals 1-2 yrs. and calves and had the effect of increasing the Emission Factors (EF) for these classes of animals by 3–29%. The corrected table of EFs for all classes of animal is reproduced directly below

Seasonality and Grazing Management Effect on Growth and Nutritional Composition of Herbage on Semi-Natural Grasslands Grazed by Dairy Cows in Southwest Germany

Natural and semi-natural grasslands represent an attractive forage source for cows in organic dairy farming. Throughout the grazing season, however, diverse factors such as climatic conditions, botanical composition, as well as grazing and herd management, can influence growth and nutritive value of forage on grasslands. We aimed at investigating the influence of seasonality and grazing management in forage growth and nutritional quality in seven commercial organic dairy cattle farms during the grazing season 2019 in South Germany. Therefore, forty exclusion cages (1 m2) were installed on pastures, which were under three different grazing systems: rotational, short-grass, and continuous grazing. Pasture herbage within and outside the cages was harvested every 4-6 weeks. The botanical composition of the pasture vegetation was estimated by visual observation, its sward height measured by a rising plate meter, and the aboveground biomass accumulation determined gravimetrically. Besides, air temperature and relative humidity were monitored by climate logger. Pasture samples inside and outside the cages were measured for dry matter (DM) according to the Association of German Agricultural Analytic and Research Institutes (VDLUFA) methods. Crude protein (CP), neutral-detergent (NDF), and acid-detergent (ADF) fibre of the samples were determined by near-infrared spectroscopy (NIRS). The forage biomass yield reached the growth peak in the second sampling (30.4 dt DM/ha) after 52 days. The CP concentrations outside the cages were greatest in late summer (166 g/ kg DM). While the ADF content outside the cages were greatest at the beginning of the grazing season (274 g/ kg DM). Besides, the CP content of the pastures was greatest under the short-grass system (193 g/kg DM) compared to the others systems. In conclusion, the seasonality influences the nutritional characteristics of the herbage, as well as the grazing management. However, the grazing management is influenced by other factors that are difficult to statistically measure

Graded supplementation of chestnut tannins to dairy cows fed protein-rich spring pasture: effects on indicators of protein utilization

An on-farm experiment was conducted in order to evaluate effects of graded supplementation with chestnut tannin extract to cows in situations of excessive dietary protein supply on a low-input organic dairy farm. Respectively 10 Swiss Fleckvieh cows received twice per day 1 kg of experimental pellets containing either 0, 50 or 100 g/kg of chestnut extract (targeted at approximately 0, 5 and 10 g extract/kg of total dietary dry matter). Experimental feeding lasted for 21 days. Measurements and collection of milk, faeces and urine spot samples were performed in weeks 0 (baseline), 1 and 3. All cows were kept in one herd on pasture; fresh grass and grass hay were provided in the barn during night. Milk yield was recorded and cows wore sensor halters for recording chewing activity. In urine, total nitrogen and purine derivatives were measured; faeces were analyzed for protein, fibre and particle fractions; in milk, solid concentrations were determined. The data was analyzed with a general linear model. Cows did not show differences in general eating and rumination behaviour, but needed time to accept the tannin-containing pellets. Milk yield and composition were not affected by treatment, except for lactose content. No relevant differences between treatments were found for urinary and faecal parameters. In conclusion, although technically easy to supplement, pellets containing chestnut tannin extract were not readily accepted by the cows and effects on protein digestion and metabolism were not found. Successful on-farm application of chestnut extract in order to improve nitrogen efficiency therefore seems questionable

Forage Production and Grazing Behaviour of Beef Cattle in Agrosilvopastoral Systems in Brazil during the Dry Season

We aimed at evaluating the microclimate, canopy structure, and grazing behaviour of cattle on Brachiaria sp. pastures within continuous pasture (CON), integrated crop-livestock (ICL), and crop-livestock-forestry (ICLF) systems in Brazilian dry season. Forage accumulation was monthly assessed in four paddocks per system from May to August 2019. To characterize the microclimate, air temperature and relative humidity were measured every hour and temperature-humidity index calculated. Grazing behaviour of 12 Nellore heifers per system (mean bodyweight 355 standard deviation±32.6 kg) was recorded by chewing sensors on nine continuous days (1 d adaptation + 8 d measurement) of three 15-d periods. Four animals per system were evaluated per period (n=3 systems x 3 animals x 3 periods x 8 d). Data were analysed by mixed model using SAS v9.4. Statistical significances were tested at P\u3c 0.05. Across the whole dry season, heifers were exposed to 343 hours of moderate heat stress and 76 hours of severe heat stress in CON and ICL. Instead, 342 hours of moderate heat stress but no severe heat stress conditions were observed in ICLF. Forage accumulation rate was greater in CON than ICLF, with no differences between ICLF and ICL. There were no differences between the systems for proportions of green leaf and dead plant material, although dead material accounted for 73% of total forage biomass on dry matter basis. Pasture in ICL was taller and had greater stem proportion than CON and ICLF. Forage canopy structure likely reduced bite mass in CON and ICL. As a compensatory mechanism, heifers in CON and ICL increased their number of grazing bites and prolonged their daily grazing time (in CON) as compared to animals in ICLF. In summary, under conditions of Brazilian dry season, grazing behaviour of Nellore heifers seems to be more influenced by canopy structure than by microclimatic factors

Weight gain and enteric methane production of cattle fed on tropical grasses

Context: Planted grasses are becoming an increasingly important feed resource for tropical smallholder ruminant production; yet, limited research has been conducted to quantify productivity or enteric methane (CH$_4$) production of animals consuming these grasses. Aim: An experiment was conducted to assess yields and nutritional attributes of the following three tropical grasses: Cenchrus purpureus var. Kakamega 1 (Napier), Chloris gayana var. Boma (Rhodes) and Urochloa brizantha var. Xaeres (Brachiaria), and quantify enteric CH$_4$ production of cattle fed on them. Methods: Yearling Boran steers (n:18; initial liveweight 216 ± 5.8 kg (mean ± s.e.m.) were allocated to one of three grasses, in a completely randomised design and fed ad libitum for two feeding periods, each period lasting for 70 days. Intake, liveweight (LW), apparent total-tract digestibility and enteric CH$_4$ production were assessed. The grasses used were grown on site and biomass yields were monitored over a 2-year period. Animal growth was also simulated to a final weight of 350 kg, and the amount of feed and size of land required to produce, and days to reach final weight, were estimated. Key results: Mean voluntary dry-matter intake (DMI) and ADG were higher (P 0.05) within period. Methane yield (MY; CH$_4$ g/DMI kg) was similar among treatments (26.7–28.5, P = 0.26) but Napier had a higher CH$_4$ conversion factor [Ym; CH$_4$ (MJ)/gross energy intake (MJ)] than did Rhodes and Brachiaria (0.0987 vs 0.0873 and 0.0903 respectively; P = 0.013). Our modelling indicated that steers consuming Rhodes took at least 30 more days to reach the target LW, required larger land area for feed production and produced more enteric CH$_4$ than did the other two diets. Conclusion: Even though animal performance and MY among treatments did not differ, the animals had higher MY and Y$_m$ than currently estimated by the Intergovernmental Panel on Climate Change. Implication: The three grasses supported similar animal growth rate, implying that growing of higher-yielding grasses such as Napier offers an opportunity to optimise land productivity in the tropics. However, suitable feeding practices such as protein supplementation need to be explored to enhance ruminant production and reduce enteric CH$_4$ production