Progressive inclusion of pearl millet herbage as a supplement for dairy cows fed mixed rations: Effects on methane emissions, dry matter intake, and milk production

Strategies of maize silage supplementation of grazing dairy cows: Effects on milk production, pasture intake, grazing behaviour and methane emissions

Supplementation strategy and grazing management can strongly influence dairy cow feeding behaviour, herbage intake, milk production and methane emissions. Two studies were conducted to investigate (1) the level of supplementation with partial mixed rations (PMR) and (2) the timing of maize silage feeding (morning vs. evening) for cows that have access to pasture either only during the day or day and night. A dataset was built that includes all individual cow measurements from both studies. It consists of 18 Microsoft® Excel files that correspond to several scales of information. The main file, "GrASTech_04_CowMeasurements", contains individual weekly measurements of milk production and composition, body weight, supplement and herbage dry matter intake measured using the n-alkane method and grazing behaviour measured using Lifecorder Plus, for a total of 168 cow × week datapoints. Five Excel files provide supplementary information at larger scales: periods, experimental treatments, feeds offered and their chemical composition, pasture characteristics and grazing management, and cow characteristics. The remaining 12 Excel files provide information at the daily scale on weather (1 file), methane concentrations and emissions (1 file), the grazing schedule (1 file) and grazing behaviour (9 files). The files related to grazing behaviour include the daily pattern of grazing time every 2 min as determined by Lifecorder Plus, as well as the daily pattern of grazing time, rumination, overactivity, other activity, rest and standing every 5 min as determined by Feed'Live. This dataset can be used to better understand and investigate relations among and the influence of animal characteristics, grazing management, the supplementation strategy and weather conditions on daily herbage intake, grazing behaviour, milk production and methane emissions at a weekly scale. The detailed information on feeding and grazing behaviour can also be used to study between-cow and between-day variability in daily cow activities.

Including 8 hours of access to alfalfa in 1 or 2 grazing sessions in dairy cows fed a partial mixed ration: Effects on intake, behavior, digestion, and milk production and composition

The aim of this study was to evaluate the inclusion of alfalfa grazing during 8 h continuous or partitioned in 2 separated sessions of 4 h after each milking, on nutrient intake, digestibility, ruminal fermentation, feeding behavior, milk production, milk composition, and milk fatty acid profile, in late-lactation cows fed a partial mixed ration (PMR). Twelve dairy cows (193 ± 83 d in milk, 584 ± 71 kg of body weight) were housed in individual outdoor pens and assigned to treatments according to a 3 × 3 Latin square design replicated 4 times. The treatments were as follows: (1) control (T0), cows were fed a total mixed ration (TMR) provided ad libitum 20.0% crude protein (CP), 32.2% neutral detergent fiber (NDF); (2) fed a diet combining a PMR which had the same ingredient composition as the TMR (60% of ad libitum intake) + 1 session of 8 h of pasture (T8), continuous grazing alfalfa (Medicago sativa; 20.6% CP, 35.8% NDF) after the p.m. milking; and (3) PMR (60% of ad libitum intake) + 2 daily sessions of 4 h of access to pasture after each milking (T4+4). The experiment lasted 57 d and was divided into 3 periods of 19 d each. The first 12 d of each period was used for diet adaptation, and the last 7 d was used for data collection. No differences among treatments were observed for any of the productive variables, feeding efficiency, or purine derivatives excretion. Cows in T0 had greater intake and apparent digestibility of dry matter, organic matter, and nonfibrous carbohydrates compared with T4+4 and T8. Compared with T0, alfalfa grazing increased the concentration of C18:1 trans-11 and decreased those of C16:0 and C17:0 in milk fat. Cows in T4+4 consumed 1.1 more kg DM/d of alfalfa and N provided by alfalfa in the diet was 3 percentage points higher compared with T8 cows (266 vs. 229 g/d, respectively). In addition, T4+4 cows had a greater daily range of ruminal pH than T8 (0.73 vs. 0.93), and the highest concentrations of NH3-N were recorded during the a.m. grazing session while in T8 cows it occurred during the night. In conclusion, including 8 h of alfalfa grazing in T8 and T4+4 treatments allowed the substitution between 35.8 and 38.7% of the total dry matter intake (DMI) of a PMR (with a similar CP concentration to alfalfa) for pasture, maintaining milk solids production and increasing the C18:1 trans-11 of milk fat compared with a TMR in mid late-lactation cows. In an herbage plus PMR diet, splitting the 1 continuous grazing session of 8 h into 2 sessions of 4 h increased the proportion of energy and N provided by alfalfa pasture and reduced PMR intake, without modifying the total nutrient intake or productive performance of cows.

Production performance, nutrient use efficiency, and predicted enteric methane emissions in dairy cows under confinement or grazing management system

There has been an intense debate regarding the economic, social, and environmental sustainability of confinement versus grazing dairy systems. Our goal was to conduct a meta-analysis to compare dry matter intake, milk yield and composition, nutrient use efficiency (i.e., feed efficiency, milk N efficiency), and predicted enteric CH₄ emissions using studies that simultaneously evaluated confinement and grazing. We were able to include in the meta-analysis 8 peer-reviewed articles that met the following selection criteria: (1) publication between 1991 and 2021 in English language, (2) report either SEM or SD, (3) inclusion of at least 1 confinement [total mixed ration or fresh cut herbage fed indoors (i.e., zero-grazing)] and 1 grazing treatment in the same study, and (4) use of markers (internal or external) to estimate herbage dry matter intake. Two unpublished experiments were added to the data set resulting in a total of 10 studies for comparing confinement and grazing. The magnitude of the effect (i.e., effect size) was evaluated using weighted raw mean differences between grazing and confinement systems for a random effect model. Enteric CH₄ production was predicted as follows: CH₄ (g/d) = 33.2 (13.54) + 13.6 (0.33) × dry matter intake + 2.43 (0.245) × neutral detergent fiber. Dry matter intake (–9.5%), milk yield (–9.3%), milk fat yield (–5.8%), milk protein yield (–10%), and energy-corrected milk (–12%) all decreased in grazing versus confined dairy cows. In contrast, concentration of milk fat and feed efficiency (energy-corrected milk/dry matter intake) were not affected by management system. Whereas milk protein concentration increased, milk nitrogen (N) efficiency (milk N/N intake) tended to decrease in grazing compared with confinement. Predicted enteric CH₄ production was 6.1% lower in grazing than confined dairy cows. However, CH₄ yield (g/kg of dry matter intake) and CH₄ intensity (g/kg of energy-corrected milk) did not change between confinement and grazing. In conclusion, while production performance decreased in grazing dairy cows, nutrient use efficiency and predicted enteric CH₄ emissions were relatively similar in both management systems. Results of our meta-analysis should be interpreted with caution due to the small number of studies that met our inclusion criteria leading to a limited number of treatment mean comparisons.

Productive, economic, and environmental effects of sunflower (Helianthus annuus) silage for dairy cows in small-scale systems in central Mexico

Small-scale dairy systems (SSDS) are important source of livelihood and socio-economic wellbeing for the rearers in general. The reduction of methane emissions with the inclusion of sunflower seed or seed-meal in rations for dairy cows has been reported in several studies. However, studies pertaining to the use of sunflower silage in dairy cattle feeding are lacking. The present study was conducted to assess the productive, economic, and environmental effects of the inclusion of graded levels of sunflower silage at 0%, 20%, 40%, and 60% (SFSL) along with maize silage (MZSL) on a dry matter basis. The silage was provided to eight Holstein cows in two 4×4 Latin-squares with 14-day periods. The study encompassed the productive performance of the cows, composition of feeds, besides the feeding costs, and enteric methane emissions estimated. The study indicated that inclusion of SFSL in the diet enhanced (P<0.001) the FCM by 3.5% and milk-fat content. SFSL increased feeding costs, but income/feeding costs ratios did not differ across the treatments. The higher inclusion of SFSL reduced methane emissions/kg of DM intake, / kg of milk, and in energy lost as methane. The inclusion of sunflower silage in feeding strategies for cows may be a viable alternative by increasing their milk yields and milk fat content and reducing methane emissions without affecting the income/feeding costs ratios.