C. T. Dougherty

Physiology and Morphology of Red Clover

Publisher Summary This chapter focuses on physiology and morphology of red clover. Red clover has long been an important forage legume in world agriculture. Through a symbiotic association with Rhizobium, red clover fixes nitrogen and contributes to the supply of N for companion grasses and subsequent crops. These characteristics have enabled red clover to be used for hay, silage, pasture, and soil improvement in many regions of the world. Stems originate from the crown and are hollow when fully developed. They have a trilacunar, three-trace nodal anatomy, and have about 10 vascular bundles in cross–section. Red clover has epigeal emergence. Germination begins about three days after imbibition of water by the seed. Imbibition rates are higher at 25 than at 6.7°C. The radical appears first and develops into a slender taproot. It grows in the range of temperature between 7 and 35–38°C, but the optimum temperature for growth is between 20 and 25°C.

Stable flies (Stomoxys calcitrans L. ) and the behavior of grazing beef cattle

Abstract A change-over design with complete balance for first residual effects was used with a tethered grazing technique to evaluate the effects of arthropod ectoparasites on the behavior of adult Angus beef cows ( Bos taurus ) (body weight (BW), 465 ± 30 kg) grazing vegetative tall fescue ( Festuca arundinacea Schreb. cultivar ‘Kentucky 31’). The three treatments were: T 1 , open grazing plots with exposure to natural ectoparasite populations; T 2 , grazing plots with exclosures (5 m × 5 m × 2 m) to minimize natural ectoparasite populations; T 3 , similar enclosures containing 2500 laboratory-reared adult stable flies ( Stomoxys calcitrans L.). At the start of grazing, herbage dry matter (DM) mass (> 5 cm) of the 25 cm sward was 2882 kg ha −1 and the herbage DM allowance (> 5 cm) was 1.0 kg (100 kg BW) −1 h −1 . Nine flies alighted on cows in open plots (T 1 ), very few ( 2 ) and 108 stable flies alighted on cows in the enclosures (T 3 ). Of the latter, there were 67 on front legs, 30 on hind legs and seven on the trunk. Stable fly populations on the body surfaces of cows declined logarithmically during grazing meals. During the first part of grazing meals, stable flies induced cows (in T 3 ) to move their heads (8 times per minute), and to lift their front legs (8 times per minute) and hind legs (3 times per minute). Stable flies also induced ear movements (12 per minute), tail movements (69 per minute) and skin twitches (25 per minute). Rates of stable fly-induced behavior declined logarithmically during grazing meals. Cows in T 1 , T 2 and T 3 visited 4.2, 3.9 and 3.1 feeding stations per minute, respectively, but rates of herbage DM intake were not affected by the presence of stable flies ( P > 0.05) and averaged 0.35 kg (100 kg BW) −1 h −1 . In the absence of stable flies (T 2 ), rates of biting of cows declined logarithmically from 46 to 30 bites min −1 . Cows subjected to stable flies (T 3 ), however, started grazing at 19 bites min −1 and ended grazing meals at 26 bites min −1 . Mean herbage DM intakes per bite were 833, 694 and 1011 mg for T 1 , T 2 and T 3 , respectively.

Behavior of grazing cattle exposed to small populations of stable flies (Stomoxys calcitrans L.)

Abstract Cattle grazing in the presence of low-level infestations of stable flies (Stomoxys calcitrans L.) may offset reductions of grazing time by increasing their rate of herbage intake, and this may contribute to the determination of economic threshold populations. On four consecutive days, we released four pulses of 50 or 100 laboratory-reared stable flies at 15 min intervals over 1 h in screened enclosures, according to a balanced change-over design. Within these enclosures, fasted, adult Angus cows (Bos taurus L.) (body weight (BW) 465 ± 30 kg) grazed vegetative tall fescue (Festuca arundinacea Schreb. cv. ‘Johnstone’) at herbage dry matter (DM) allowances of 1.4 kg (100 kg BW)−1 h−1. Alighted fly numbers on body surfaces of cows were similar during each quarter of grazing meals, and numbers of alighted flies increased linearly as more were released. Cows exposed to colonies of 100 stable flies had 16 alighted on fore legs, 5 on hind legs and 5 on trunks. Stable flies weighed 6.1 mg before and 17.7 mg after feeding. Fly-induced behavior of grazing cows did not vary significantly (p > 0.05) within grazing meals, and releases of up to 100 stable flies caused linear increases in movements of heads (to 3.3 min−1), ears (to 3.7 min−1), skin twitches (to 14 min−1 side−1) and tail swishes (to 36 min−1), but had little effect on movements of fore and hind legs (

Ingestive behavior of beef heifers within grazing sessions

Abstract Two field experiments were used to measure the net effects of changing hunger and satiety on the ingestive behavior of tethered beef cattle ( Bos taurus ) within grazing sessions that followed overnight fasts. Angus heifers [liveweight (LW), 364±8 kg] were grazed on a vegetative tall fescue ( Festuca arundinacea Schreb.) pasture with a herbage mass of 4.5 t ha −1 of dry matter (DM) and herbage DM allowances of 5.5 kg per heifer h −1 . During their first hour of grazing, heifers ingested herbage DM at 0.65% LW h −1 and took bites of 1 g DM at 41 bites min −1 . After 45 or 90 min of grazing, heifers were consuming herbage at 0.51% LW h −1 and forming bites of 0.9 g at 37 bites min −1 . In the second experiment with twice the herbage DM allowance (11 kg per heifer h −1 ) and slightly higher herbage DM mass (5.6 t ha −1 ), heifers ate herbage at 0.76% LW h −1 and took bites averaging 1.2 g (DM) at 36 bites min −1 during the first hour of grazing. Heifers in their second or third hour of grazing ate herbage at 0.48% LW h −1 and took bites of 1 g at 29 bites min −1 . The decline in rate of intake within grazing sesssions was attributed to declining hunger and increasing satiety. Rates of herbage intake of animals grazing temperate swards unrestricted by allowance and availability of herbage are ∼ 0.5% LW h −1 after hunger is alleviated.

Herbage allowance and intake of cattle

Rates of intake of herbage and grazing time of beef cattle are essential components of simulation models of grassland agroecosystems. We studied the effects of herbage allowance on rates of intake and ingestive behaviour of twelve 2-year-old Angus heifers ( Bos taurus )(364 ± 12 kg) grazing pastures of tall fescue ( Festuca arundinacea Schreb.). A balanced change-over design and a novel tethering technique were used to estimate direct, residual and permanent effects of three herbage allowances on intake per bite, rate of biting and rate of intake. Herbage dry matter (D.M.) allowances, which were established by varying tether lengths, were 5, 9 and 13 kg (1·4, 2·5 and 3·6 kg/100 kg of live weight) and made available in circular plots of 15, 27 and 38 m 2 , respectively, for a single measured 2 h grazing session each day. Heifers grazing Kenhy tall fescue swards, composed of vegetative tillers and free from the endophyte Acremonium coenophialum , with herbage D.M. masses (> 5 cm) of 2000 kg/ha and D.M. allowances of 9 and 13 kg/2 h per heifer, ingested D.M. at 1·9 kg/h by taking bites averaging 800 mg D.M. at 38 bites/min. Allowances of 5 kg/2 h per heifer slowed the rate of intake to 1·3 kg/h by limiting D.M. intake per bite to 654 mg and biting rate to 35/min. Rate of D.M. intake of cattle grazing vegetative temperate grass swards appears to be ca. 0.5% of live weight per hour when allowance and availability of herbage are not limiting.

Moderation of grazing behavior of beef cattle by stable flies (Stomoxys calcitrans L.)

Abstract Grazing beef cows ( Bos taurus L.) were exposed to stable fly ( Stomoxys calcitrans L.) and their reactions were related to ingestive behavior. Three concatenated latin squares (4 × 4) were used to evaluate the effects of stable flies on the behavior of Angus cows grazing vegetative tall fescue ( Festuca arundinacea Schreb. cv Johnstone) in screened enclosures. Four populations (0, 50, 100 and 150) of starved, laboratory-reared stable flies were released into each enclosure at 15 min intervals during 1 h grazing meals. Mean numbers of alighted stable flies increased linearly with treatment level up to 125 per animal and up to 46 on forelegs and up to 7 on hindlegs. Dorsal and ventral trunk surfaces each supported up to 35 alighted flies. Alighted fly numbers increased on all major body sectors as grazing meals progressed: when 150 stable flies were released, there were 25, 44, 56 and 63 flies on forelegs during successive quarters. Releases of up to 150 stable flies caused linear increases in fly-induced movements of heads (to 1.9 min −1 ), ears (to 4.5 min −1 ), skin twitches (to 18 min −1 per side), tail swishes (to 36 min −1 ), forelegs (to 1.4 min −1 ) and hindlegs (to 0.8 min −1 ). Stable flies caused linear increases in herbage dry matter (DM) intake (0.50–0.58 kg (100 kg body-weight (BW)) −1 h −1 ), and bite DM mass (from 1.0–1.4 g) and a linear decline in rate of biting (from 41-35 bites min −1 ). Cows visited 3.2, 3.9, 4.3 and 3.4 feeding stations min −1 ingesting 16.1, 12.6, 10.9 and 16.0 g DM per feeding station when four pulses of 0, 50, 100 and 150 stable flies were released, respectively. Blood intake of engorged stable flies declined from 9.3 to 8.1 mg, either indicating competition between flies for feeding stations or deterrent actions of their hosts disturbed their feeding. Moderation of ingestive behavior of cows was attributed to annoyance of low populations of alighted flies. In the presence of stable flies, cattle may accelerate herbage intake and reduce grazing times.

Face flies (Musca autumnalis De Geer) and the behavior of grazing beef cattle

Abstract Ectoparasites, at or above certain levels, usually reduce productivity of infested livestock, however the causative processes are often poorly defined. Irritation from non-biting flies may, for example, interfere with grazing behavior and reduce herbage intake while increasing the energy diverted to support fly-induced behavior. Zero, 400 or 800 laboratory-reared adult face flies ( Musca autumnalis De Geer), which had been deprived of nutrients and water for 12 h, were released in large (5 m×5 m×2 m) screened enclosures each containing one tethered adult Angus beef cow ( Bos taurus ) grazing tall fescue ( Festuca arundinacea Schreb. cultivar ‘Johnstone’). At the start of grazing, the herbage dry matter (DM) mass of the vegetative sward was 3861 kg ha −1 , sward surface was at 21 cm and the pseudostem surface plane was at 6 cm. The herbage DM allowance was 1.4 kg (100 kg) −1 h −1 . Surfaces of the heads of grazing cows supported about 30 alighted face flies. In addition, 20 and 30 flies alighted on the backs of cows grazing in the presence of 400 and 800 face flies per enclosure, respectively. Few face flies were present on other body surfaces. Heads of cows moved 0.0, 1.0 and 0.7 min −1 in response to the activity of 0, 400 and 800 face flies per cow, respectively. Ear movements were initiated 0.1, 22.2 and 14.3 min −1 per cow exposed to 0, 400 and 800 face flies, respectively. Panniculus reflexes (on one side of the cows body) were triggered 0.3, 3.5 and 4.1 min −1 per cow when exposed to 0, 400 and 800 face flies, respectively. Face flies (0, 400 and 800 per cow) activated cow tail movements 0.4, 3.2 and 10.1 min −1 , but did not induce movements of the front or hind legs. Rates of herbage DM intake increased linearly from 1.69 to 2.91 kg per cow h −1 (0.37–0.59 kg (100 kg) −1 h −1 ) as the numbers of face flies increased up to 800 per cow, largely because herbage DM intakes per bite increased from 0.74 to 1.36 g. Rates of biting in grazing cows (37 bites min −1 ) and the time spent at feeding stations (19 s per station) were not significantly affected by face flies. It appears that cows grazed deeper into the sward in an attempt to dislodge face flies from the muzzle and this resulted in heavier bites and, consequently, higher rates of herbage intake.

Modification of Ingestive Behavior due to Exercise in Yearling Horses Grazing Orchardgrass

Abstract Eight yearling horses were used in a balanced change-over design to determine: (1) voluntary herbage dry matter (DM) intake during a 3-h grazing session; (2) whether ingestive behavior is modified by exercise. The exercise treatments were either no forced exercise (NEX) or 30-min forced exercise (EX) at a rate of 3.6 m s −1 on a mechanical horse-walker. Following exercise treatments, the yearlings were tethered and allowed to graze a plot of orchardgrass ( Dactylis glomerata L.) during a closely monitored 3-h morning grazing session. Intake (DM) was estimated by subtracting the harvested residual herbage from the calculated herbage mass allowance. Voluntary herbage DM intake was not significantly different between NEX (1.81 kg) and EX (1.75 kg) horses during the 3-h grazing session. The biting rate during the first 20 min of grazing was higher ( P −1 ) than for EX (12.6 bites min −1 ) yearlings. Mean biting rate, calculated for the 3-h session, was higher ( P −1 , respectively). Estimated herbage intake per bite tended to be smaller for NEX (861 mg/bite) than for EX (865 mg/bite) yearlings. Since forage intake during the grazing session was not significantly different between treatment groups, these data indicate that the 30 min of forced exercise given in this experiment did not alter intake. Apparently the EX horses modified their grazing behavior by taking fewer, but larger, bites.

Accessibility of Herbage Allowance and Ingestive Behavior of Beef Cattle

Rate of intake may be accelerated when grazing cattle (Bos taurus) are given access to fresh pasture. Two experiments using a balanced change-over design and tethered adult cows of 471±18 kg liveweight were used to measure the effect of accessibility of alfalfa (Medicago sativa L.) on ingestive behavior. In the first experiment, herbage dry matter (DM) allowances of 10.5 kg were available for 90 min in one, two or three equal portions by area and time. These treatments had little effect on ingestive behavior and cattle ate DM at a mean rate of 2.25 kg h−1 by taking bites of 1.5 g DM at 25 bites min−1. In a second experiment, cows had access to 8.8 kg herbage DM allowances as a whole (T1), in two equal portions (T2) in time and area within the same plot, or in two separate plots (T3). A mean rate of DM intake of 2.2 kg h−1 was attained by forming bites of 1.6 g at 23 bites min−1. Accessibility of allowance had no significant (P<0.05) effect on ingestive behavior. Rates of biting immediately before and after the change-over were 26 and 20, 17 and 33, and 16 and 28 for T1, T2, and T3, respectively. It was apparent that rates of biting accelerated when cows were exposed to fresh swards but the effects were transitory and contributed little to overall rates of DM intake.

Intake of cattle offered normal and lodged tall fescue swards.

Grazing behavior of livestock may be altered when grass swards are lodged by trampling or wind and rain. We used a balanced change-over design to investigate the effects of lodging on the ingestive behavior of Angus cows (Bos taurus L.)(mass (M): 344 kg) grazing swards of vegetative endophytefree ‘Kenhy’ tall fescue ( Festuca arundinacea Schreb.). Animals were offered normal swards (T1), lodged swards (T2), or swards with one half of their area lodged (T 3 ). To simulate lodging, swards were covered overnight with weighted plywood sheets that compressed sward surface height (SSH) from 34 to 14 cm and elevated sward dry matter (DM) density from 151 to 499 kg ha -1 cm -1 for herbage > 5 cm. Mean herbage DM intake per bite was 561 mg for T1, 713 mg for T2 and 792 mg for T 3 . Cattle grazed at 28 bites min -1 for T 1 , and 25 bites min 1 for both T 2 and T3. Herbage DM intake rates were 0.27, 0.31, and 0.33 kg 100 kg -1 (M) hour -1 for T 1 , T 2 , and T 3 , respectively. In another experiment, cattle were offered equal areas of normal swards (SSH: 27 cm) and lodged swards (SSH: 16 cm), normal and partially defoliated swards (SSH: 20 cm) swards, or lodged and partially defoliated swards. When offered normal and lodged swards, 64% of DM intake came from normal swards. When offered normal and partially defoliated swards about 60% of DM intake came from normal swards. Cattle grazed equally on lodged and partially defoliated sward segments when offered that choice.