ARTICLE 76 FEED & ADDITIVE MAGAZINE November 2023 and late lactation stages (average days in lactation, 240 days, average number of lactations, 3.58). All of the cows were provided with partial mixed ration (PMR) ad libitum and each cow was allocated a concentrate ration based on milk production. The concentrate was supplied by a commercial animal feed company (Browns Stockfeed). The composition of the concentrate is as follows: crude protein 12.79%, starch 60.94%, metabolizable energy 12.92 mj/Kg, calcium 1.81%, phosphorous, 0.34%, magnesium 0.47%, dry matter 88.55%, neutral detergent fibre 10.17%, rumen undegraded protein 26.46%, fat 2.33%, Cu 5.83 mg/kg, magnesium 36.29 mg/kg, selenium 0.14 mg/kg, zinc 25.90 mg/kg. The concentrate was provided to the animals during milking time in the feed bin and this was also the location of the methane sampling and measurement. Three weeks of baseline measurements were recorded, followed by a 3-week intervention period of the sugarcane extract (Polygain™). During the baseline period, the daily average temperature ranged from a minimum of 10 °C to a maximum 16.7 °C and 3.4 mm of rainfall. This is compared to the climactic conditions in the intervention phase with a daily average temperature ranging between 13.05 °C and a maximum of 15.05 °C and 3.7 mm of rainfall. 2. Polygain Feeding The sugarcane extract (Polygain™) was included in the animal’s diet at 0.25% of total estimated dry matter intake (DMI). This was based on previous work in earlier ruminant studies [18]. Based on an estimation of the average combined intake of pasture and concentrate of 20 kg per animal, 50 g of sugarcane extract (Polygain™) was required to be delivered via the concentrate. Animals were on average consuming 5 kg of concentrate per day and therefore the sugarcane extract (Polygain™) was added at 10 g/kg of feed for the dietary intervention phase of the trial. Polygain™ is a dark brown liquid that consists of a complex mixture of natural phytochemicals. 3. Methane Data Collection Methane concentration in feed bins during milking was determined by the “Sniffer method” as described in [19,20,21]. Briefly, an infrared methane analyzer (Guardian Plus; Edinburgh Instruments Ltd., Livingstone, UK) was outside the feed bin of each milking robot with a sampling tube extended into the feed bin. The methane analyzer had a measurement range of 0–1% or 0–10,000 ppm. A 3 m length of polyethylene tube with an 8 mm diameter was connected to the inlet port of the gas analyzer. Air was continuously sampled from the feed bins of robots during the trial at a flow rate of 1 L/min. The sampling point was positioned approximately l5cm from the rim of the feed bin, opposite to the side of feed dispensing. A 50 mm inline filter was installed in the tube between the air sampling point in the feed bin and second filter inside the gas analyzer inlet to avoid feed particles, dust and moisture from entering the gas analyzer and causing measurement interference and damage. A 3 m length of tube was used to vent the captured methane away from the methane sampling point to avoid recirculation of methane gases. The methane analyzer was calibrated as per the manufacturer’s guideline at weekly intervals. Briefly, this calibration involved flushing of the unit with nitrogen gas to determine a true reading of 0% methane. Following this procedure standardized methane gas canisters at concentrations of 1%, 0.5% and 0.25% were used to calibrate and validate accurate measures were recorded by the instrument. Methane concentrations were recorded via a data logger (AEMC instruments, 4–20 m ADC, simple logger model SL20). The data logger was configured with 1 s measurement intervals. 4. Milk Quantity and Quality Measurements This study was conducted on a commercial dairy farm with a robotic milking system installed which was capable of recording individual animal milk production data during the trial. Milk composition for individual cows was determined by the robot via the MQC sensors installed in the robot that generate an indication for protein and fat. This included daily milking history (average milk/day), milk composition data (fat indication, protein indication), and Bulk Milk Somatic Cell Count (BMCC), which was monitored via the routine analysis of the milk bulk tank at each collection.
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