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Dry matter intake (DMI) is a primary determinant of milk production in grazing dairy cows and an ability to measure the DMI of individual cows would allow herd managers to formulate supplementary rations that consider the amount of nutrients ingested from grass. The 2 related aims of this experiment were to define the mean number of swallowed boli and mass of the swallowed boli in Holstein-Friesian dairy cattle offered a variety of forages commonly fed in the dairy industry of southeastern Australia, and to evaluate 2 indirect methods for counting the number of swallows. Twelve ruminally-fistulated, lactating Holstein-Friesian cows were randomly assigned to 3 replicated 4 × 4 Latin square designs and offered 4 forages: fresh chicory (FC), fresh perennial ryegrass (RP), alfalfa hay (AH), and perennial ryegrass silage (RS). The experiment was conducted over 28 d with each of 4 periods consisting of 7 d with 3 d of measurement. Forage diets were offered to individual cows following the partial evacuation of the rumen. The first 20 min after forage was offered constituted the measurement period, during which all swallowed boli were manually captured by samplers who placed their hand through the ruminal fistula and over the cardia entrance of the rumen of each cow. Concurrently, microphones and video cameras were used for the indirect measurement of swallows. The average swallowed bolus mass overall was 17.4 g dry matter (DM) per bolus with the lowest mass observed in cows offered FC (8.9 g DM/bolus), followed by RP (14.9 g DM/bolus), compared with cows offered AH (23.6 g DM/bolus) and RS (22.3 g DM/bolus). The swallowing rate was greater in cows offered FC (78 swallows/20 min) than in cows offered RP, AH, and RS (62.3 swallows/20 min). The audio recording method showed greater concordance (Lin's concordance correlation coefficient = 0.90) with the physical capturing of the boli through the rumen, than the video recording method did (Lin's concordance correlation coefficient = 0.54). It is concluded that the mass of the swallowed boli is related to forage type and that using a microphone attached to the cow's forehead can provide an accurate measure of the number of swallows when verified against the actual number of swallows counted by manual interception of the boli at the rumen cardia. [ABSTRACT FROM AUTHOR]

Bite mass is the dry matter ingested per prehension bite. It has previously been reported that sward characteristics such as herbage height, density and allowance can affect bite mass in grazing cows. Animal characteristics such as liveweight and incisor arcade breadth may also affect bite mass. Understanding factors that influence bite mass can lead to an improvement in the estimate of dry matter intake of grazed herbage. The aim of this study was to determine the effects of liveweight and incisor arcade breadth on average daily bite mass of grazing dairy cows. The research consisted of two parts. In Part I, 113 multiparous lactating Holstein-Friesian cows were assessed for their 7-d average liveweight and incisor arcade breadth. In Part II, from the 113 cows screened in Part I, 32 cows were selected for use in a grazing experiment. The 32 cows were allocated to one of four groups of 8 cows based on the following factors: light cows (mean liveweight of 542 kg) with narrow incisor arcade (mean of 8.2 cm) (L-N), light cows (mean liveweight of 581 kg) with wide incisor arcade (mean of 9.5 cm) (L-W), heavy cows (mean liveweight of 658 kg) with narrow incisor arcade (mean of 8.2 cm) (H-N) and heavy cows (mean liveweight of 660 kg) with wide incisor arcade (mean of 9.5 cm) (H-W). Each cow grazed in an individual plot and herbage intake was calculated as the difference between estimated pre-and post-grazing herbage mass in each plot, as measured with a rising plate metre. Prehension bites were counted using jaw movement sensors. In Part I, incisor arcade breadth of the cows was between 7.0 and 9.8 cm and liveweight was between 490 and 745 kg. There was no relationship (P = 0.30) between liveweight and incisor arcade breadth of these cows. In Part II, mean bite masses were 0.46, 0.50, 0.50 and 0.49 g DM/bite for LN, LW, HN and HW, respectively and the differences between them were not significant (P = 0.30, SED = 0.03). There was also no effect of liveweight category (P ≥ 0.68) or incisor arcade breadth category (P ≥ 0.72) or their interaction (P ≥ 0.78) on prehension bites, mastication chews or total eating bites. These findings suggest that mechanistic models for estimating bite mass and herbage intake may not need to include liveweight or incisor arcade breadth. • Incisor arcade breadth of cows showed no effect on bite mass. • Liveweight of cows showed no effect on bite mass. • There was no relationship between liveweight and incisor arcade breadth of cows. [ABSTRACT FROM AUTHOR]

The RumiWatch System (Itin+Hoch GmbH, Liestal, Switzerland) is a sensor system that enables quantification of ingestive behaviors of cattle that may be useful, amongst other things, for estimating dry matter intake. There are currently multiple versions of the RumiWatch Converter software used to convert the recorded data into specific animal behaviors through the use of algorithms. The objective of this research was to evaluate the use of RumiWatch System noseband sensors for quantifying the number of prehension bites and mastication chews in grazing and stall-fed dairy cows using RumiWatch Converter software versions 0.7.3.36 (RWC36) and 0.7.4.13 (RWC13). Two experiments using lactating Holstein-Friesian dairy cattle were conducted. In Experiment I, ten cows grazed perennial ryegrass pasture (Lolium perenne L.) in individual plots that measured 35 m2, with a pasture mass of 2500 kg DM/ha and pasture allowance of 28 kg DM/d. In Experiment II, 14 cows were offered 16 kg DM/d of perennial ryegrass pasture silage in individual indoor feed stalls. In both experiments, ingestive behaviors were quantified with the jaw movement halters and through visual observation using video recordings. The performance of the RumiWatch Converter software was evaluated through Lin's concordance correlation coefficients with video observation. For grazing cows, there was greater concordance between the RumiWatch System and video observation for the number of prehension bites (0.94 for RWC36 and 0.75 for RWC13) than for the number of mastication chews (0.20 for RWC36 and 0.14 for RWC13). In cows fed in stalls, there was also greater concordance for the number of prehension bites (0.54 for RWC36 and 0.64 for RWC13) than for the number of mastication chews (0.46 for RWC36 and 0.58 for RWC13). However, the RWC36 was more accurate for quantifying feeding behaviors of grazing cows than the RWC13, while for stall fed cows the reverse was true. Overall, both RumiWatch Converters were better at quantifying prehension bites in grazing cows than in stall fed cows, but better at quantifying mastication chews in stall fed cows than grazing cows. These data enable a new understanding of the how these RumiWatch sensors should best be used for measuring cows' feeding behaviors in different feeding systems. • The RumiWatch System is accurate for identifying prehension bites in grazing and stall-fed cows. • Both RumiWatch converters were better at identifying ingestive behaviors in grazing cows than stall fed cows. • In grazing cows, RumiWatch Converter 0.7.3.36 was more accurate than RumiWatch Converter 0.7.4.13. • In stall fed cows, RumiWatch Converter 0.7.4.13 was more accurate than RumiWatch Converter 0.7.3.36. [ABSTRACT FROM AUTHOR]

• Average bite mass was greater when pasture allowance was greater. • Bite mass was greatest in the first hour of grazing and then declined. • No difference in bite mass was found when cows grazed low and medium pasture mass. Dry matter intake (DMI) of herbage is a product of bite rate and bite mass and is a determinant of the performance of grazing ruminants. This research tested the effect of herbage allowance and herbage mass on average bite mass of individual dairy cows grazing perennial ryegrass herbage (Lolium perenne L.). Two experiments were conducted, one in each of winter (Experiment 1) and spring (Experiment 2). In each experiment, 24 Holstein-Friesian dairy cows grazed individual perennial ryegrass plots over 10 d. In each experiment cows grazed one of six treatments: low or medium herbage mass (1900 or 2200 kg DM.ha−1 in Experiment 1 and 2200 or 3000 kg DM.ha−1 in Experiment 2) combined with either low, medium or high herbage allowance (15, 25 or 40 kg DM.cow−1.d−1 in Experiment 1 and 20, 30 or 40 kg DM.cow−1.d-1 in Experiment 2). Grazing behaviour was measured with jaw movement sensors and DMI was determined by herbage disappearance measured with a rising plate meter daily, and at hourly intervals during the first 4 h of grazing after the morning milking. Average bite mass (g DM.bite−1) per day and per hour was determined as the mass of herbage that had disappeared in each period (g.d−1 or g. h−1) divided by number of prehension bites in that period. The combined data from two experiments was analysed by Linear Mixed Model and it was found there was no effect of herbage mass (P = 0.686) on bite mass per day. However, cows offered high herbage allowance had greater (P < 0.001) bite mass per day (0.62 g DM.bite-1) than cows offered the lowest herbage allowance (0.38 g DM.bite-1) across both experiments. The effect of herbage allowance was similar across both herbage masses. Bite mass per hour was the highest (P < 0.001) in the first hour of grazing in both experiments with average bite mass per hour across two experiments in the first hour of grazing (0.69 g DM.bite−1) greater than in the second (0.40 g DM.bite−1), third (0.35 g DM.bite−1) and fourth (0.32 g DM.bite−1) hours of grazing. We conclude that herbage allowance is a significant factor in determining bite mass and should be included in models aimed at predicting bite mass and hence daily herbage intake of grazing dairy cows. [ABSTRACT FROM AUTHOR]