Effect Of Herbage Mass Research Articles

Effects of herbage mass and herbage allowance on bite mass of grazing dairy cows

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.

Effect of pregrazing herbage mass on methane production, dry matter intake, and milk production of grazing dairy cows during the mid-season period

Increasing milk production from pasture while increasing grass dry matter intake (GDMI) and lowering methane (CH4) emissions are key objectives of low-cost dairy production systems. It was hypothesized that offering swards of low herbage mass with increased digestibility leads to increased milk output. A grazing experiment was undertaken to investigate the effects of varying levels of HM on CH4 emissions, GDMI and milk production of grazing dairy cows during the mid-season grazing period (June to July). Prior to the experiment, 46 Holstein-Friesian dairy cows (46 d in milk) were randomly assigned to 1 of 2 treatments (n=23) in a randomized block design. The 2 treatments consisted of 2 target pregrazing HM: 1,000kg of dry matter (DM)/ha (low herbage mass, LHM) or 2,200kg of DM/ha (high herbage mass, HHM). The experimental period lasted 2 mo from June 1 until July 31. Within the experimental period, there were 2 measurement periods, measurement 1 (M1) and measurement 2 (M2), where CH4 emissions, GDMI, and milk production were measured. Mean herbage mass throughout the measurement periods was 1,075kg of DM/ha and 1,993kg of DM/ha for the LHM and HHM treatments, respectively. Grass quality in terms of organic matter digestibility was significantly higher for the LHM treatment in M2 (+12g/kg of DM). In M1, the effect of herbage mass on grass quality was approaching significance in favor of the LHM treatment. Herbage mass did not significantly affect milk production during the measurement periods. Cows grazing the LHM swards had increased GDMI in M1 (+1.5kg of DM) compared with cows grazing the HHM swards; no difference in GDMI was observed in M2. Grazing HHM swards increased CH4 production per cow per day (+42g), per kilogram of milk yield (+3.5g/kg of milk), per kilogram of milk solids (+47g/kg of milk solids), and per kilogram of GDMI (+3.1g/kg of GDMI) in M2. Cows grazing the HHM swards lost a greater proportion of their gross energy intake as CH4 during both measurement periods (+0.9% and +1% for M1 and M2, respectively). It was concluded that grazing LHM swards would increase grass quality with a concurrent reduction in CH4 emissions.

Effect of herbage mass on the selection and use by cattle of fine‐scale locations in a progressively grazed tropical grass pasture

AbstractThis study quantified herbage mass and feeding behavior by animals at a fine spatial scale, in a 1.1‐ha bahiagrass (Paspalum notatum Flügge) pasture progressively (4 or 5 days) grazed by a herd of 32–33 beef cows and 8–13 calves in three seasons (spring, summer and autumn). Herbage mass was nondestructively estimated every day, using an electronic capacitance probe, at 91 fixed locations (50 cm × 50 cm; approximating a feeding station scale) along a permanent line transect. At the same time, selection and use of the individual locations by cows were measured every day, in terms of the number of visits, number of bites and residence time. Vegetation of the pasture created a trade‐off between availability (herbage mass) and quality (nitrogen concentration, dry matter digestibility) in summer and autumn but not in spring. There were always considerable location‐to‐location variations in the feeding behavior of animals; that is, some locations were not visited and bitten at all or were visited infrequently (once or twice daily) and grazed only for a short time (&lt;10 s daily) receiving relatively few bites (&lt;10 bites daily), whereas some locations were frequently visited (5–10 times daily) and utilized for a long period (&gt;30 s daily) receiving many bites (&gt;30 bites daily). Although regression analysis showed a tendency for animals to select and use locations with higher herbage mass in spring and those with lower or intermediate herbage mass in autumn as a result of the seasonally different availability–quality relationships, neither herbage mass nor herbage quality was an absolute factor determining the choice and use of locations by animals. The results show that the choice and use of fine‐scale locations by animals foraging in actual grasslands are not fully explained by major forage factors such as mass, nitrogen and digestibility.

Comparison of haymaking strategies for cow‐calf systems in the Salado Region of Argentina using a simulation model. 1. Effect of herbage mass at cutting and cow stocking rate under a rigid system of management

AbstractA simulation model was used to compare the long‐term performance of cow‐calf farm systems under different haymaking strategies on a 100‐ha farm. In the simulation, farm management was based on that which had been developed on Reserva 6, an experimental cow‐calf farm established in 1966 at Instituto Nacional de Tecnología Agropecuaria‐Balcarce Experimental Station, Argentina, where different technologies, including haymaking, have been adapted and applied in order to increase productivity of cow‐calf systems in the Salado Region of Argentina. The management of the system is based on a restricted mating season (2 months), early weaning (5–7 months of age) and forage conservation. The simulations showed that the effect of using hay with respect to the strategy without hay, in terms of calf liveweight (LW) production per hectare, was greatest at the cow numbers that maximized production (290–320 cows) with a proportionate increase of 0.25. On the other hand, the advantage of using hay was smallest when the herbage mass at cutting for hay was 6 t dry matter (DM) ha−1, particularly when more than 0.50 of the farm area was allocated to haymaking. The differences among the haymaking policies increased with cow numbers, especially at high herbage masses at cutting for hay. The analysis also suggested that the LW production per hectare of cow‐calf farms would be maximized by harvesting 0.40–0.50 of the total farm area and aiming to cut hay at a herbage mass of 4 t DM ha−1 and with medium quality.

Effect of herbage mass per unit area and conditioning treatment on herbage drying rate

The rates of drying of herbage, cut from perennial ryegrass (Lolium perenne L.) – dominant swards and subjected to different treatments, were investigated under field conditions by changes in weight of herbage in wire mesh trays in 1995 and 1996. A series of replicated factorial experiments studied the effects, in different combinations, of intensity of conditioning achieved by passing the cut herbage through a laboratory‐scale macerator zero (0C), once (1C), three (3C) or six (6C) times; weight of herbage per unit area equivalent to 450, 675 and 900 g dry matter (DM) m−2. In one experiment, pressing the herbage to form a mat was incorporated into the experimental design. A further experiment investigated the effect of varying the proportion of conditioned herbage in the herbage mass from 0·00, 0·25, 0·50, 0·75 and 1·00 on drying rate. On each occasion the trays plus herbage were weighed at hourly intervals over an ≈6‐h period and the DM content of the herbage estimated from the change in weight. On all occasions, conditioning and weight of herbage per unit area significantly (P &lt; 0·001) influenced herbage drying rate. Lowering the weight per unit area of both unconditioned and conditioned herbage increased the rate of moisture loss. Unconditioned herbage at the equivalent of a herbage mass of 450 g DM m−2 had a total moisture loss that was on average 1·5–1·8 times greater than unconditioned herbage at the equivalent of a herbage mass of 900 g DM m−2. Similarly, conditioned herbage at the equivalent of a herbage mass of 450 g DM m−2 had a total moisture loss that was 1·8–2·3 times greater than unconditioned herbage at the equivalent of a herbage mass of 900 g DM m−2. Increasing the level of conditioning produced a non‐linear response in rate of moisture loss, consequently 3 passes through the macerator produced &gt;0·95 of the total moisture loss that was produced by 6 passes through the macerator. Increasing the proportion of conditioned herbage in the herbage mass increased rate of moisture loss and consequently final DM content (P &lt; 0·001) although there was little effect from increasing the proportion of conditioned herbage above 0·75. The effects of conditioning and weight of herbage per unit area treatments on total nitrogen , water‐soluble carbohydrate and acid‐detergent fibre concentration of the herbage were small.

The relationship between herbage mass and pasture accumulation rate in winter

Herbage mass of rotationally grazed paddocks was measured by pasture plate meter on Massey No. 4 Dairy Farm in the Manawatu and at Limestone Downs, a sheep and beef property near Port Waikato, in the North Island, New Zealand. Data were collated and pasture accumulation rates calculated. A quadratic regression model was fitted to both farm data sets to investigate the relationship between herbage mass and pasture accumulation rate for the May to August period over two years. Although the data sets contained a large amount of unexplained variation, the effect of herbage mass on pasture accumulation rate was found to be significant (P < 0.01). The estimate for herbage mass which maximised pasture accumulation rate was 2500 kg DM ha−1 for No. 4 Dairy Farm. The optimum could not be estimated for Limestone Downs because of substantial data variability. Because the confidence interval for the dairy farm estimate of optimum is wide, it can not be concluded unequivocally that optimum herbage mass for New Zealand conditions is higher than the figure of 1250 kg DM ha−1 identified in Britain. However, there is indication that management that results in higher post‐grazing residuals will enable higher pasture accumulation rates on at least some New Zealand dairy farms. This question of optimum pasture cover should be the focus of further research on a range of New Zealand farm types.