Virtual fencing technology to intensively graze lactating dairy cattle. I: Technology efficacy and pasture utilization

Virtual fencing is promoted as the next advancement for rotational grazing systems. This experiment compared the capacity of conventional temporary electric versus virtual fencing to contain a herd of 30 lactating dairy cows within the boundaries of their daily pasture allocation (inclusion zone). Cows were moved each day to a new rectangular paddock that was divided crosswise into an inclusion and exclusion zone by a single linear electric (first 10 d) or virtual (second 10 d) front-fence. A 3-d virtual fence training period separated the 2 treatments. Virtual fences were imposed using a pre-commercial prototype of the eShepherd virtual fencing system (Agersens Pty Ltd.). Neckband-mounted devices replaced the visual cue of an electric fence with benign audio cues, which if ignored were accompanied by an aversive electrical stimulus. Cows learned to respond to the audio cues to avoid receiving electrical stimuli, with the daily ratio of electrical to audio signals for individual cows averaging (± standard deviation) 0.18 ± 0.27 over the 10 d of virtual fence deployment. Unlike the electric fence, the virtual fence did not fully eliminate cow entry into the exclusion zone, but individual cows were generally contained within the inclusion zone ≥99% of the time. Pasture depletion within the inclusion zone reduced the efficacy of the virtual fence in preventing cows from entering the exclusion zone, but the magnitude of this effect was insignificant in practical terms (i.e., increased time spent in the exclusion zone by ≤28 s/h per cow). This highlights the potential for virtual fences to control grazing dairy cow movement even when pasture availability is limited (i.e., 1 kg of dry matter/cow above a target residual of 1,500 kg of dry matter/ha), but requires confirmation under longer and more complex virtual fencing applications. Within each treatment period, uniform daily pasture utilization (% of pasture consumed above a target residual of 1,500 kg of dry matter/ha) within inclusion zones indicates that cows did not avoid grazing near electric or virtual front-fences. Overall, this study demonstrated a successful simple application of this virtual fencing system to contain a herd of grazing lactating dairy cows within the boundaries of their daily pasture allocation.     

Milk production of fall-calving dairy cows during summer grazing of grass or grass-clover pasture

Milk production of fall-calving dairy cows during subsequent summer grazing was evaluated in two consecutive years using a total of 80 mid- to late-lactation Holsteins. Cows calved during September and October and grazed from April to August in the following year. In yr 1, 27 cows grazed a native grass pasture and 13 cows grazed a native grass-clover mixed pasture containing 26% red clover and white clover. In yr 2, 40 cows grazed native grass pasture as one group. Also, cows in yr 2 were administered bovine somatotropin, whereas in yr 1, no bST was used. Grazing cows also were fed concentrate supplements at 6.2 kg/d of dry matter (DM) in yr 1 and 7.9 kg/d of DM in yr 2 to provide 35 to 40% of total intake. Average daily milk during the grazing period decreased 3.6 kg in yr 1 and 7.7 kg in yr 2 when compared with milk yield extrapolated from the lactation curve established 10 wk before being turned out to pasture. Estimated DM intake during grazing was also less than what would have been expected had cows continued on a total mixed ration in confinement. Cows grazing the mixed pasture of grass and clover yielded 1.3 kg/d more milk than those grazing the grass pasture in yr 1. A decrease in milk resulting from the change from total mixed ration fed in confinement to grazing supplemented with concentrates was not avoided with these mid- to late-lactation cows, but the cumulative loss over the lactation was less than with early lactation cows in a companion study. Clover enhances the grazing value of pasture when grown with grasses.     

Use of monensin controlled-release capsules to reduce methane emissions and improve milk production of dairy cows offered pasture supplemented with grain

We examined the effects of monensin, provided by controlled-release capsules, on the enteric methane emissions and milk production of dairy cows receiving ryegrass pasture and grain. In a grazing experiment, 60 Holstein-Friesian cows were assigned randomly to 1 of 2 groups (control or monensin). Cows in the monensin group received 2 controlled-release capsules, with the second capsule administered 130 d after the first. Milk production was measured for 100 d following insertion of each capsule. The sulfur hexafluoride tracer gas technique was used to measure enteric methane emissions for 4 d starting on d 25 and 81 after insertion of the first capsule, and on d 83 after insertion of the second capsule. All cows grazed together as a single herd on a predominantly ryegrass sward and received 5 kg/d of grain (as-fed basis). In a second experiment, 7 pairs of lactating dairy cows (control and monensin) were used to determine the effects of monensin controlled-release capsules on methane emissions and dry matter intake. Methane emissions were measured on d 75 after capsule insertion by placing cows in respiration chambers for 3 d. Cows received fresh ryegrass pasture harvested daily and 5 kg/d of grain. The release rate of monensin from the capsules used in both experiments was 240 ± 0.072 mg/d, determined over a 100-d period in ruminally cannulated cows. The monensin dose was calculated to be 12 to 14.5 mg/kg of dry matter intake. There was no effect of monensin on methane production in either the grazing experiment (g/d, g/kg of milk solids) or the chamber experiment (g/d, g/kg of dry matter intake). In the grazing study, there was no effect of monensin on milk yield, but monensin increased milk fat yield by 51.5 g/d and tended to increase milk protein yield by 18.5 g/d. Monensin controlled-release capsules improved the efficiency of milk production of grazing dairy cows by increasing the yield of milk solids. However, a higher dose rate of monensin may be needed to reduce methane emissions from cows grazing pasture.     

Pasture forages,supplementation rate,and stocking rate effects on dairy cow performance

Objectives were to evaluate effects of forage species, stocking rate, and supplementation rate on performance and physiology of grazing lactating Holstein cows under intensive rotational stocking management during summer. Eight treatments were arranged in a 2 x 2 x 2 factorial design. Animals (n = 62) grazed pastures of Tifton 85 bermudagrass or Florigraze rhizoma peanut, a tropical legume. Low and high stocking rates were 7.5 and 10.0 cows/ha for bermudagrass and 5.0 and 7.5 cows/ha for rhizoma peanut. Within each forage-stocking rate combination, cows were fed supplement at 0.33 or 0.5 kg of supplement (as-fed basis)/kg daily milk production. Cows grazing rhizoma peanut pastures produced more milk (16.9 vs. 15.4 kg/d) but had higher rectal temperatures (39.4 vs. 39.1 degrees C). Milk production per cow was improved at the higher stocking rate for bermudagrass but was reduced at the higher stocking rate for peanuts. Increasing supplementation rate boosted plasma glucose, milk production, and milk protein percent. Increased supplementation rate had a greater positive impact on milk production of cows grazing bermudagrass compared to rhizoma peanut (21.9 vs. 10.6% increase) due to a lower substitution of grain for forage intake. Organic matter intakes of forage, supplement, and total diet were greatest by cows grazing rhizoma peanut pastures and averaged 12.4, 6.1, and 18.5 kg/d compared to 9.2, 5.4, and 14.6 kg/d for cows grazing bermudagrass. Despite lower individual feed intake and performance, production per unit land area was 29% greater (112 vs. 90 kg of milk/ha per d) for cows grazing bermudagrass due to the greater stocking rate possible with that forage. Only cows supplemented at the high rate and kept at the high stocking rate on bermudagrass maintained body weight. Cows on other treatments lost body weight. Tifton 85 bermudagrass appears to be an excellent summer forage for dairy cows grazing in the southeastern U.S. given its nutritive value characteristics and high yields. Optimum stocking rate may be as high as 10 cows/ha during times of peak growth of forage for low-to-moderately producing cows fed supplement. Furthermore, the positive milk production response to additional supplement when cows grazed Tifton 85 pastures (0.8 kg/kg of supplement), indicates the value of providing supplement to cows grazing this moderate quality forage.     

Utilization of three maturities of alfalfa by dairy cows fed rations that contain similar concentrations of fiber

The effect of alfalfa maturity on ration utilization and lactation performance by high producing dairy cows was measured in a 13-wk lactation study. Eighteen multiparous Holsteins were fed one of three rations containing first crop alfalfa hay harvested at early vegetative (36.1% NDF), late bud (51.7% NDF), or full bloom (51.7% NDF) maturity. Forage to concentrate ratios were 68:32, 53:47, and 45:55 for early vegetative, late bud, and full bloom rations, respectively. As offered, the late bud ration was higher in fiber (34.6% NDF) than either the early vegetative (31.8% NDF) or full bloom (30.6% NDF) rations. Cows fed the ration with early vegetative hay produced as much 4% FCM (32.5 kg) as cows fed the ration containing more fiber (late bud, 32.9 kg) or the later maturity hay (full bloom, 32.2 kg). Milk fat and protein composition were not affected by ration fiber concentration or forage maturity. Average dry matter intake per day and body weight change were similar across treatments. Time spent ruminating was similar for the three rations (6.8 h/d), but eating time was affected by forage maturity (early vegetative, 4.4 h/d vs. full bloom, 5.7 h/d). Cows receiving the higher fiber diet (late bud, 6.2 h/d) spent more time eating than cows receiving the lower fiber diets. Fiber concentration and forage maturity did not affect milk production, milk composition, or body weight change of high producing dairy cows in early lactation.     

Automatic milking and grazing--effects of distance to pasture and level of supplements on milk yield and cow behavior

In an automatic milking system, 45 cows were divided into groups that grazed on a mixed grass sward (Poa Pratensis and Festuca Pratensis) at different distances from the barn: near pasture (NP) at 50 m between the barn and the pasture and distant pasture (DP) at 260 m between the barn and the pasture. For both of these treatments, 3 kg of dry matter (DM) from supplementary grass silage were offered in the barn. The third treatment group grazed together under the DP treatment but was offered an ad libitum supply of grass silage in the barn (DP + S). Cows were also fed concentrates in relation to requirements (average 7 kg/d per cow). During the period from June 5 to July 13 (Period 1), cows in the NP group had a higher milk yield (29.1 kg) than did cows in the DP group (26.4 kg) and had a higher milking frequency compared with the other groups, 2.5 vs. 2.3 and 2.3 milkings/d, respectively. During August, cows in group DP + S had a lower milking frequency (2.1 milkings/d) compared with the two groups on lower supplementation (2.5 milkings/d). In Period 1, all groups spent approximately 20% of their time grazing, but after mid July groups DP and DP + S decreased the time they spent grazing to around 10%; cows in group NP continued to graze as before. Thus, longer distances to pasture may lead to decreases in milk yield, milking frequency, and grazing time of cows in an automatic milking system. The higher level of silage supplementation (group DP + S) did not result in a significantly higher milk yield compared with herd-mates (DP) also grazing the more distant pasture.     

Short-term increases in stocking density affect the lying and social behavior, but not the productivity, of lactating Holstein dairy cows

Reduced access to resources because of increased stocking density may have a detrimental effect on the behavior of the lactating dairy cow. The objective of this study was to determine the short-term responses in behavior, productivity, fecal cortisol metabolites, and udder and leg hygiene of lactating Holstein dairy cows housed at stocking densities of 100 (1 cow per freestall and headlock), 113, 131, and 142%. Multiparous cows (n=92) and primiparous cows (n=44) were assigned to 1 of 4 pens (34 cows per pen) in a 4-row freestall barn. Pens were balanced for parity, milk production, and days in milk. Stocking densities were imposed for 14 d using a 4 × 4 Latin square design. Time spent feeding and time spent ruminating were quantified by 24 h of direct observation of focal cows (n=12 per pen) beginning at 0800 h on d 11 of each period. Data loggers recorded lying behavior (time and bouts) from the same focal cows per pen at 1-min intervals during the final 5 d of each period. Fecal cortisol metabolites were quantified from samples collected on d 13 and 14 of each period from the same focal cows. Displacements from the feed barrier were recorded on a pen basis after 9 milkings over the last 4 d of each period. Productivity was assessed on a pen basis from milk yield (recorded from d 10 to 14 of each period) and milk components (quantified from composite samples collected on d 12 of each period). Milk composition was further analyzed for milk fatty acid profiles, which were determined from a subset (n=6 per pen) of the focal cows. Data were analyzed using the MIXED procedure of SAS, with the pen (n=4 per treatment, except displacements where n=3 per treatment) as the experimental unit. Feeding and ruminating (h/d) did not differ among treatments. Lying time was reduced at stocking densities of 131 and 142%, relative to 100 or 113%. Lying bouts were not affected by treatment. Stocking densities of 131 and 142% reduced the percentage of time cows spent ruminating within a freestall relative to 100%. Displacements from the feed bunk increased linearly across treatments. Fecal cortisol metabolites, udder hygiene score, milk yields, milk composition, and milk fatty acids did not differ among treatments. Decreased lying time and increased aggression at the feed bunk suggest that an alteration of the time budgets of lactating dairy cows may occur at higher stocking densities, but it is unclear at what point these changes might have further biological consequences.     

The effect of a commercial probiotic product on the milk quality of dairy cows

Probiotics intended to improve plant health and productivity of pastures grazed by dairy cow are becoming commercially available in Australia. Great Land (GL; Terragen Biotech Pty Ltd., Coolum Beach, QLD, Australia) is one such biologic soil conditioner and spray-on probiotic with a label claim of “acting to improve plant health and productivity.” The objective of this study was to quantify the effect of GL on the milk quality of cows grazing pasture top-dressed with GL. Lactating dairy cows of mixed age and breed (primarily Holstein-Friesian), in their second lactation or greater, and at least 80 d in milk were enrolled and randomly allocated into 1 of 2 study groups: a treatment cow group (n = 98; cows grazed pasture that was top-dressed with GL according to the product label) and a control cow group (n = 114; cows grazed untreated pasture). As required, both groups were supplemented at the same rate with a mixed ration during the grazing period. Composite milk samples were collected weekly from each cow during the study and analyzed to determine milk components. Milk volumes were recorded at each milking using the herd management software of the study farm. Mean differences in the milk component variables were compared using mixed-effects linear regression models. After controlling for the effect of days in milk, cow lactation, and time since a cow entered the study, the treatment cows produced an average of 1.21 L/cow per day more milk (95% confidence interval: 0.34–2.08 L/cow per day) and more milk protein (0.03 kg/d; 95% confidence interval: 0.01–0.05 kg/d) than the control cows. Pasture cover and pasture consumption did not differ between the GL-treated and the untreated study paddocks grazed by the treatment or control cows. A limited amount of published data have examined the effect of probiotic pasture treatment on the milk quality of dairy cows. This study suggests that application of such products may be beneficial. The mechanisms associated with this type of outcome remain to be investigated.     

Milk production and composition, rumen fermentation parameters, and grazing behavior of dairy cows supplemented with different forms and amounts of corn grain

The objectives were to compare milk production and composition, change in body weight and body condition score, rumen fermentation parameters and grazing patterns by cows when supplemented with different forms and amounts of corn grain. In experiment 1, 36 Holstein cows were supplemented with either 6, 6, 6, or 4 kg/d of dry matter of high moisture corn, coarsely ground corn, finely ground corn, or high moisture corn in two equal daily feedings, respectively. Milk yield (30.3 kg/d), milk protein (2.97%), and milk urea N (14.7 mg/dl) were not different among treatments. Body weight change and body condition score change were similar (23.1 kg and -0.24) for the 10-wk study. During experiment 2, four rumen cannulated cows in midlactation were supplemented with 6 kg/d of dry matter from either coarsely ground corn or high moisture corn in two equal feedings after milking. After the p.m. milking, ruminal pH was measured and rumen fluid samples, were collected from cows to determine ammonia N and volatile fatty acids at 0.5, 1, 2, 3, ...8 h post-corn feeding during grazing. Ruminal pH values were similar for corn supplements, and, with one exception, were 6.0 or below between 5 and 8 h. Ruminal ammonia-N concentrations reached a maximum at 7 h also. In experiment 3, 40 cows were observed for grazing behavior every 30 min for two consecutive days. Cows grazed an average of 6.4 h/d, 4.1 h in the afternoon and 2.3 h in the morning. Milk yield, milk composition, change in body weight, and body condition were similar regardless of the type or amount of corn supplemented.     

Effects of abomasal infusion of long-chain fatty acids on intake, feeding behavior and milk production in dairy cows

Fat is often fed to dairy cows to increase the energy concentration of their diet; however, feeding fat often reduces dry matter intake (DMI), which limits its impact on metabolizable energy (ME) intake. To investigate the effects of postruminal fat infusion on intake, feeding behavior, and milk production of dairy cows at two stages of lactation (55 and 111 d postpartum), six Holstein x British Friesian cows were infused into the abomasum, with a mixture of rapeseed and sunflower oils supplying predominantly unsaturated long-chain fatty acids (LCFA). Dry matter intake was significantly depressed by oil infusion, but estimated ME intake was unchanged, and thus there was no effect of oil infusion on milk yield. There was no effect of stage of lactation on the DM or ME intake response to oil infusion. Milk fat concentration was increased by oil infusion in mid-lactation but not in early lactation, suggesting that the infused LCFA were utilized differently in early compared with midlactation. Cows spent an average of 654 min idling, 462 min ruminating, and 248 min eating during the last 22.8 h of each infusion. There were no significant effects of oil infusion or stage of lactation on the total time spent engaged in these activities. An assessment of the circadian pattern of feeding behavior suggested that the depression in DMI in response to oil infusion occurred after the 1630 and 2230 h feeding times. This may reflect differences in mechanisms regulating feed intake behavior and appetite during the day. Comparison of the results of the present study with the results of other trials involving postruminal fat infusion suggests that polyunsaturated nonesterified fatty acids have the most potent effect on DMI intake.     

Effect of spring grazing date and stocking rate on sward characteristics and dairy cow production during midlactation

The objective of this study was to investigate the effect of initial spring grazing date and subsequent stocking rate on sward characteristics, grazing behavior, milk yield, and dry matter intake of spring-calving dairy cows during the main grazing season. Sixty-four spring-calving Holstein-Friesian dairy cows (58 ± 9 d in milk) were balanced and randomly assigned to 1 of 4 grazing treatments (n = 16) between April 12, and July 3, 2004. Two swards, an early-grazed (E) sward and a late-grazed (L) sward had 2 stocking rates, high and medium, imposed across them. Cows grazing the E swards were stocked at 4.5 cows/ha (E4.5) and 5.5 cows/ha (E5.5), whereas cows grazing the L sward were stocked at 5.5 cows/ha (L5.5) and 6.4 cows/ha (L6.4). Sward characteristics, grazing behavior, and grass dry matter intake (GDMI) were investigated during the second (R2) and fourth grazing rotations (R4). Total dry matter yield was greater on L swards in R2. In R2, the E swards had a greater proportion of leaf as well as a lesser stem and dead dry matter yield. During R2, organic matter digestibility and crude protein content were greater on the E sward than the L sward. Pre-and postgrazing heights were greater for the L swards in R2 and R4. In R4, there was a larger leaf allowance on the E swards. Grazing time was greater and ruminating time lesser for animals grazing the E sward in R2. During R4, intake per bite was greater for the E5.5 and E4.5 treatments. Milk and solids-corrected milk yields as well as GDMI were greater for animals grazing the E sward in both R2 and R4. The results of the present study suggest that early grazing initially had a positive effect on sward quality and structure, which resulted in improved grazing behavior characteristics, increased GDMI, and increased milk production. During R4, sward quality and structure were similar between swards; thus, differences in grazing behavior were due to divergent daily herbage allowances. These results suggest that sward structure and quality as well as daily herbage allowance are important factors that influence animal performance and grazing behavior.     

The effects of frequency of feeding a total mixed ration on the production and behavior of dairy cows

Two experiments were conducted to examine the response of Friesian dairy cows to different frequencies of feeding a total mixed ration. The first compared alternate day with daily feeding. Cows fed on alternate days spent longer feeding, had increased dry matter intakes, and produced more milk, but with reduced protein content, compared with cows fed daily. Those fed daily increased feeding greatly after the food was offered to them. Those fed on alternate days had a smaller increase in feeding when food was offered, and their feeding pattern was similar on feeding and nonfeeding days, suggesting that they could not anticipate the time that food would be offered. However, on days when no food was provided they were less aggressive than cows fed daily. Cows fed daily spent less time grooming themselves and more time standing, suggesting that the extra feeding caused disturbance. A second experiment compared frequent feeding (four times per day) with infrequent feeding (once daily), with the cows fed infrequently being either housed with or apart from the cows fed frequently, to determine whether the disturbance of feeding other cows would affect cows housed in the same building but not fed frequently. Both groups of frequently fed cows spent less time feeding in the morning and more in the evening and had less circadian variation in sleeping and lying ruminating, compared with both groups of cows fed infrequently. Cows fed infrequently and housed by themselves produced more milk but with reduced milk protein concentration, compared with the infrequently and frequently fed cows that were housed together. They also spent more time standing in the feeding passage, not ruminating, and more time grooming themselves, indicating less disturbance. Thus cows fed infrequently had reduced milk yield if they were housed with frequently fed cows, and it is concluded that in both experiments frequent feeding disturbed the cows and reduced milk production.     

The effect of by-product inclusion and concentrate feeding rate on milk production and composition,pasture dry matter intake,and nitrogen excretion of mid-late lactation spring-calving cows grazing a perennial ryegrass-based pasture

Interest is growing in the use of by-products as economical sources of nutrients that complement grazed grass, particularly at times when grass supply is insufficient to meet the nutritional demands of lactating dairy cattle. The objective of this research was to assess the effect of the amount of by-product inclusion and concentrate feeding rate on pasture dry matter intake, milk production and composition, and N excretion from spring-calving cows grazing summer pasture during mid-late lactation. Forty-eight Holstein Friesian dairy cows were randomly assigned to 1 of 4 dietary treatments in a 2 × 2 factorial design. Cows were grazed in one group on a perennial ryegrass-based sward, with pelleted concentrates offered twice daily during milking over a 63-d experimental period. The dietary treatments were 3 kg of concentrate containing 35% by-products; 6 kg of concentrate containing 35% by-products; 3 kg of concentrate containing 95% by-products; and 6 kg of concentrate containing 95% by-products on a fresh matter basis. The by-products used were soybean hulls, palm kernel expeller, and maize dried distillers grains with solubles, included in equal proportions on a dry matter basis. Pasture dry matter intake (14.5 kg/d) was not affected by the amount of by-product inclusion or feeding rate. By-product inclusion had no effect on milk yield (27.1 kg/d) or milk solids (MS) yield (2.0 kg/d). Cows offered 6 kg of concentrate had a greater milk (+1.6 kg/d) and MS (+0.13 kg/d) yield, consumed more N (+0.08 kg/d), and excreted a lower proportion of N in the milk (0.25 vs. 0.27) and feces (0.39 vs. 0.41) and a higher proportion in the urine (0.39 vs. 0.32) compared with cows offered 3 kg of by-product-based concentrate. In conclusion, by-products can be included at up to 95% of the concentrate fed to cows grazing pasture without affecting pasture dry matter intake, milk production or composition, or N excretion. Cows offered 6 kg of concentrates produced more milk and MS than cows offered 3 kg but had higher urinary N excretion. Economics of this yield response will depend on milk and concentrate prices.     

A high dose of monensin does not reduce methane emissions of dairy cows offered pasture supplemented with grain

The primary objective of our research was to determine the effect of a high dose of monensin supplementation on enteric CH₄ emissions of dairy cows offered a ryegrass pasture diet supplemented with grain. An additional objective was to evaluate effects on milk production and rumen function, because a commensurate improvement in milk production could lead to adoption of monensin as a profitable strategy for methane abatement. Two experiments were conducted (grazing and respiratory chambers) and in both experiments monensin (471 mg/d) was topdressed on 4 kg (dry matter)/d of rolled barley grain offered in a feed trough twice daily at milking times. In the grazing experiment, 50 Holstein-Friesian cows were assigned randomly to 1 of 2 groups (control or monensin). Cows grazed together as a single herd on a predominantly ryegrass sward and received monensin over a 12-wk period, during which time measurements of milk production and body weight change were made. The SF₆ tracer technique was used to estimate methane production of 30 of the 50 cows (15 control cows and 15 monensin cows) for 3 consecutive days in wk 3, 5, 8, and 12 of treatment. Samples of rumen fluid were collected per fistula from 8 of the 50 cows (4 per diet) on 2 consecutive days in wk 3, 5, 8, and 12 of treatment and analyzed for volatile fatty acids and ammonia-N. In the metabolic chamber experiment, 10 pairs of lactating dairy cows (control and monensin) were used to determine the effects of monensin on methane emissions, dry matter intake, milk production, and body weight change over a 10-wk period. Methane emissions were measured by placing cows in respiration chambers for 2 d at wk 5 and 10 of treatment. Cows received fresh ryegrass pasture harvested daily. Monensin did not affect methane production in either the grazing experiment (g/d, g/kg of milk) or the chamber experiment (g/d, g/kg of dry matter intake, g/kg of milk). In both experiments, milk production did not increase with addition of monensin to the diet. Monensin had no effect on body weight changes in either experiment. Monensin did not affect volatile fatty acids or ammonia-N in rumen fluid, but the acetate to propionate ratio tended to decrease. Monensin did not improve milk production of grazing dairy cows and no effect on enteric methane emissions was observed, indicating that monensin cannot be promoted as a viable mitigation strategy for dairy cows grazing ryegrass pasture supplemented with grain.     

Toward on-farm measurement of personality traits and their relationships to behavior and productivity of grazing dairy cattle

There is growing evidence that animal personality is linked to a range of productivity traits in farm animals, including dairy cattle. To date, the methodology for assessing personality traits of dairy cattle is time consuming and often requires a test arena, which limits the opportunity for commercial farms to use personality traits of dairy cattle for individualized management. This study investigated whether personality traits of pastured dairy cattle, scored in short behavioral tests, are associated with daily behavioral patterns and milk production. Cows (n = 87) were exposed twice to each of 5 behavioral tests, where their responses to novel or putatively stressful situations were scored on an ordinal scale for investigative and reactive behavior toward a novel object and a novel human after exiting the milking parlor, response to restraint in a crush, avoidance distance from an approaching human in the paddock, and response to milking (step-kick behavior). Most behavior test scores were consistent over the 2 test repeats (using repeatability estimates, Mann-Whitney U test of difference between repeats, and Spearman rank correlation). Behavior test scores were subjected to a principal components analysis that revealed intertest relationships in 3 factors of correlated sets of test scores, interpreted as personality traits (fearful of humans, calm-investigative, and reactive to milking). Regression analyses determined how these traits were associated with daily grazing, ruminating, and lying behaviors, and milk production (after controlling for cow age, breed, lactation status, group, and climate variables). Cows that were more fearful of humans (high avoidance distance, reactive toward the novel human) had reduced lying time compared with cows that scored low on this trait. Cows that were more calm (during restraint) and investigative (toward the novel object) had greater grazing time, which likely contributed to their greater milk production compared with cows that scored low on this trait. Cows that were more reactive to milking produced less milk than cows that scored low on this trait. These results indicate that individual differences in daily behavior patterns and milk production of dairy cattle are associated with personality traits of cows, measured using several short behavioral tests. These methods may be useful for characterizing grazing dairy cattle on commercial farms, which could aid in understanding individual behavior patterns and provide opportunities for individualized management.     

Comparative grazing behavior of lactating Holstein-Friesian, Jersey, and Jersey × Holstein-Friesian dairy cows and its association with intake capacity and production efficiency

The objectives of this study were to investigate differences in grazing behavior among Holstein-Friesian (HF), Jersey (JE), and Jersey × Holstein-Friesian (F₁) cows under an intensive, seasonal, grass-based environment and to determine whether associations exist among grazing behavior, intake capacity, and production efficiency. Data from a total of 108 animals (37 HF, 34 JE, and 37 F₁) were available for analysis. Measurements included milk production, body weight (BW), intake, and grazing behavior. Breed group had a significant effect on all of the production, grass dry matter intake, and efficiency parameters investigated. No differences were observed among the breeds for grazing time, number of grazing bouts, grazing bout duration, and total number of bites. Grazing mastications were higher for the JE cows compared with the HF cows. Grass dry matter intake per bite and rate of intake per minute were higher for the HF cows compared with the JE cows. Large differences between the breeds were apparent when grazing behavior measurements were expressed per unit of BW and per unit of intake. In absolute terms, the HF cows spent more time ruminating and had more mastications during rumination than the JE cows. However, when expressed per unit of BW, ruminating time was greater for the JE cows and they tended to have more ruminating mastications compared with the HF cows. Despite these differences, ruminating time and ruminating mastications per unit of intake were similar for the 2 breeds. For the most part, the F₁ cows tended to be similar to the mid-parent mean, but results showed an increase in biting rate, lower grazing duration per bout, and a tendency to achieve a high intake per bite compared with the average of the parent breeds. The results obtained also indicate that inherent grazing and ruminating differences exist between cows varying in intake capacity and production efficiency. Cows with higher intake capacities have increased grazing time and rate of intake per unit of BW. Increased production efficiency, on the other hand, appears to be aided, in particular by improvements in mastication behavior during grazing.     

Energy expenditure of grazing cows and cows fed grass indoors as determined by the 13C bicarbonate dilution technique using an automatic blood sampling system

The objectives of the study were to assess the ¹³C bicarbonate dilution technique using an automatic blood sampling system and to use this technique to estimate energy expenditure (EE) based on the CO₂ production of 14 lactating Holstein cows on pasture or in a freestall barn. The effects of physical activity and eating behavior on EE were also assessed. Cows were exposed to each feeding system in a crossover design with two 14-d experimental periods, each consisting of an adaptation period and a 7-d data collection period. Cows either grazed on pasture or had ad libitum access, in the freestall barn, to grass cut daily from the same paddock. All cows were supplemented with a cereal-based concentrate. The EE of each cow was determined from 0700 to 1300 h on 1 d of each collection period. Blood samples for the ¹³C bicarbonate dilution technique were taken either manually in the barn or using an automatic blood sampling system on pasture. Eating pattern and physical activity were recorded from 0700 to 1300 h using a behavior recorder and an activity meter, respectively. Milk yield was recorded daily. Individual feed intake was estimated using the alkane double-indicator technique. Two preceding experiments confirmed that the sampling technique (manual or automatic) and the following storage of the blood samples (frozen directly after withdrawal or first cooled on ice and then frozen 6 h later) had no effect on ¹³CO₂ enrichment in the extracted blood CO₂ or on the subsequent calculation of CO₂ production. During the 6-h measurement period, the EE of cows on pasture was higher than that of cows in the freestall barn. Daily feed intake and milk production were not affected by the feeding treatment. Grazing cows spent more time walking and less time standing and lying than did cows fed indoors. Time spent eating was greater and time spent ruminating was lower for cows on pasture compared with grass-fed cows in the barn. In conclusion, the ¹³C bicarbonate dilution technique, combined with an automatic blood sampling system, is a suitable method to determine the EE of lactating dairy cows on pasture. Positive correlations between EE and walking and eating time indicate that the higher energy requirements of dairy cows on pasture may be at least partly caused by a higher level of physical activity. However, before specific recommendations about additional energy supply can be given, it must be determined whether EE measured over 6 h can be extrapolated to 24 h. Furthermore, the apparent inconsistency between EE, feed intake, and milk production needs to be resolved.     

Intake and performance of lactating cows grazing diverse forage mixtures

Twenty multiparous Holstein cows in midlactation grazed pastures of 4 forage mixtures in a 12-wk study repeated during 2 grazing seasons to determine if forage mixture complexity affected intake and productivity of lactating dairy cows. The forage mixtures were 1) orchardgrass plus white clover [2 species (SP)]; 2) orchardgrass, white clover, and chicory (3SP); 3) orchardgrass, tall fescue, perennial ryegrass, red clover, birdsfoot trefoil, and chicory (6SP); and 4) 6SP mixture plus white clover, alfalfa, and Kentucky bluegrass (9SP). Total herbage intake was similar among forage mixtures, averaging 12.0 kg/d across all forage mixtures and years. Milk production and composition were not affected by forage mixture or year, and averaged 34.6 kg/d, 3.4%, and 2.8% for milk production, milk fat percentage, and milk protein percentage, respectively. The conjugated linoleic acid content of milk fat was higher for cows that grazed the 3SP, 6SP, and 9SP mixtures than from cows that grazed the 2SP mixture (1.02 vs. 0.87 g of conjugated linoleic acid/100 g of fatty acids, respectively). Blood glucose, blood urea nitrogen, and nonesterified fatty acids were not affected by forage mixture and averaged 69.2 mg/dL, 13.4 mg/dL, and 277.5 μEq/L, respectively. The results of this study indicate that altering the forage mixture in pastures did not affect dry matter intake, milk production, or blood metabolite profiles of lactating cows. The use of complex mixtures of forages in grazing systems should not affect dairy cow performance.     

Effects of corn silage supplementation strategy and grazing intensity on herbage intake,milk production,and behavior of dairy cows

Effects of corn silage supplementation on milk production of grazing dairy cows depend in part on the substitution rate between the 2 forages, which may be influenced by grazing management. The aim of this study was to compare 2 grazing management strategies for measuring substitution rate between herbage and corn silage, in interaction with grazing intensity. Six treatments were compared, with 2 grazing intensities and 3 supplementation strategies investigated at both grazing intensities. The 2 grazing intensities were severe and light grazing, defined by either (1) herbage allowance (HA) of 15 (severe) or 30 (light) kg dry matter (DM)/cow per d at 3 cm above ground level or (2) postgrazing sward height, depending on the supplementation strategy. The 3 supplementation strategies were as follows: (U) an unsupplemented treatment, (A) 5 kg DM/d of corn silage offered at a similar HA as in U, and (H) 5 kg DM/d of corn silage offered at a similar postgrazing sward height as in U. Thirty-six multiparous Holstein cows were used in a randomized complete block design and divided in 2 groups for the entire experiment, one for each grazing intensity. Within each grazing intensity group, the corn silage supplementation strategy was studied using a 3 × 3 Greco-Latin square design, with 3 periods of 14 d. Supplementing cows with corn silage increased total DM intake only for severe grazing by 1.7 kg DM/d. The substitution rate between corn silage and grazed herbage was lower for severe than for light grazing, averaging 0.63 and 1.23, respectively. Herbage dry matter intake was lower by 1.2 kg/d for strategy H than A, leading to lower substitution rates (0.81 vs. 0.99, respectively), irrespective of grazing intensity. Milk production increased with silage supplementation for severe grazing (+1.0 kg/d milk) and was unaffected by silage supplementation for light grazing (?0.4 kg/d milk). The milk production response to corn silage supplementation averaged +0.23 and ?0.08 kg of milk per kg DM of silage for severe and light grazing, respectively. Fat-corrected milk production tended to be lower by 0.4 kg/d for strategy H than A, leading to lower milk production response (+0.00 vs. +0.12 kg of milk per kg DM of silage, respectively). Milk protein concentration increased with silage supplementation for severe grazing (+1.0 g/kg) but decreased with silage supplementation for light grazing (?0.6 g/kg). Milk fat concentration did not differ among treatments. On average, daily grazing time (?47 min/d, i.e., ?9%) and herbage intake rate (?4.9 g of DM/min, i.e., ?14%) decreased when cows were supplemented, with greater grazing time reduction at severe than light grazing, and greater herbage intake rate reduction at light than severe grazing. In conclusion, the greater substitution rate and the lower 4% fat-corrected milk production when corn silage was provided at a similar postgrazing sward height rather than at a similar HA to those of unsupplemented cows explain why supplementing grazing dairy cows with conserved forages has no strong effect in practice from a production point of view.     

Effects of feeding virginiamycin and sodium bicarbonate to grazing lactating dairy cows.

The effects of virginiamycin, an agent active against Gram-positive lactic acid-producing bacteria, and NaHCO3 on ruminal and fecal pH, rumen volatile fatty acid proportions, blood metabolites, and milk production and composition were assessed. This study was conducted over 28 d and involved 71 dairy cows that grazed predominantly ryegrass, oats, and clover, and that were fed 10 kg of concentrate pellets/d per head. The pellets contained (per kilogram) no dietary additive, 30 mg of virginiamycin, 20 g of NaHCO3, or 30 mg of virginiamycin and 20 g of NaHCO3 on a DM basis. Ruminal pH tended to be higher in cows fed pellets containing virginiamycin (7.0 vs. 6.9; SED = 0.16). The results of in vitro incubation of ruminal fluid with glucose found the potential for L-lactic acid accumulation in ruminal fluid to be significantly lower in cows fed virginiamycin (15.5 vs. 35.3 mmol/L; SED = 2.98). Cows fed virginiamycin had significantly higher fecal pH (6.72 vs. 6.57; SED = 0.08) and produced more milk (23.94 vs. 23.32 kg/d) and more lactose than those not fed virginiamycin. No effects of NaHCO3 on fecal pH, in vitro potential for L-lactic acid accumulation in ruminal fluid, or milk production were observed, but ruminal pH tended to be higher and ruminal acetate proportion was greater for cows fed NaHCO3. Milk fat and milk protein percentage did not differ significantly as a result of dietary treatment. These data suggest that the inclusion of virginiamycin in the diet will reduce L-lactic acid accumulation in ruminal fluid and increase fecal pH in grazing dairy cattle fed concentrate supplements.