Dry matter intake and digestion of alfalfa harvested at sunset and sunrise.

The preference exhibited by animals in selecting one feed over another is important only if the preferred diet is consumed daily in larger quantities, digested to a greater extent, or both. Six alfalfa (Medicago sativa L.) hays were harvested in pairs at sunset (PM) and sunrise (AM) on consecutive days at three harvest dates. A previous study of these hays demonstrated differences in ruminant preference favoring PM harvests. This study evaluated the effects of time of cutting and harvest date on voluntary DMI and nutrient digestibility. The hays were field-cured, baled, and chopped before evaluation for intake and digestibility. Studies were conducted for sheep (Ovis aries), goats (Capra hircus), and cattle (Bos taurus). Goats, but not steers or sheep, demonstrated differences in nutrient digestibility between PM- and AM-cut hays. Goats consumed more PM than AM hay (2.97 vs. 2.83 kg/100 kg of BW; P = 0.07) and digested it to a greater extent (0.710 vs. 0.696; P = 0.03), resulting in greater digestible DMI (2.11 vs. 1.97 kg/100 kg of BW; P = 0.03). Sheep consumed (mean = 2.52 kg/100 kg of BW; P = 0.59) and digested (mean = 0.681; P = 0.25) PM- and AM-cut hays similarly. Steers consumed larger quantities of PM-than AM-cut hay (2.90 vs. 2.62 kg/100 kg of BW; P = 0.11), but digestion did not differ with cutting time (mean = 0.660; P = 0.75). Difference values (composition of fed hay minus composition of orts) indicated that sheep and goats selected from the feed offered similarly, whereas steers selected differently. Difference values for CP averaged 94 and 101 g/kg for goats and sheep and 32 g/kg for steers (P < 0.01), and difference values for NDF averaged 185 and 196 g/kg for goats and sheep and 73 g/kg for steers (P

Beef cattle losses after grazing Lupinus argenteus (silvery lupine).

Ten yearling steers weighing 270-360 kg died acutely after eating early seed pod stage Lupinus argenteus (silvery lupine) containing high levels of piperidine alkaloids, including ammodendrine and N-methylammodendrine. Reduced availability of Quality feed from range moderately depleted of Quality grasses appeared a major factor in causing the cattle to graze lupine. Proximate analysis of whole plant, seed pods and seed showed high levels of crude protein ranging from 16.4 to 48% for whole plant and seed. Alkaloid analysis of the whole plant and individual plant parts such as seed and seed pods (30-40% seed shatter) showed total alkaloid levels ranging from 0.70 to 2.5% (0.70-2.5 mg/100 mg plant) dry weight. Ammodendrine levels ranged from 0.24% in seed pods with >70% seed loss to 1.35% in early growth plant with no seed. N-methylammodendrine levels ranged from 0.38% in seed pods with >70 % seed shatter to 1.04 % in pure seed. Other minor alkaloids totaled 0.08% in seed pods with >70% seed shatter to 0.60% in early growth plant before seed pod formation. These cattle ate an estimated 1.8 g/kg dry weight (486 g to 648 g) of lupine in 24 h. This appears the first report of acute death in cattle associated with piperidine alkaloid-containing Lupinus argenteus.

Preference by sheep and goats among hay of eight tall fescue cultivars.

Grazing ruminants use both visual cues and taste in selecting their diet. Preference during grazing may not be the same when forage is dried for hay and cut into lengths prior to feeding in confinement. Eight cultivars of tall fescue (Festuca arundinacea Schreb.), previously evaluated for preference while grazed, were harvested three times over a period of 2 yr. The hays were air-dried, baled, and passed through a hydraulic bale processor prior to feeding. Five experiments were conducted. All three harvests were evaluated with sheep and the last two also with goats, using six animals each time. During an adaptation phase, hays were offered alone as meals. In the experimental phase, every possible pair of hays (28 pairs) was presented for a meal. Data were analyzed by multidimensional scaling and by traditional analyses. Preference was significant among cultivars in all experiments. Multidimensional scaling showed that selection was based on two criteria with two dimensions being significant. Sheep preferred KENHY followed by KENTUCKY 31 and STARGRAZER but preferenced against BARCEL. HIMAG, MO-96, and C1 were intermediate and MOZARK was variable. Goats were similar to sheep in preferring KENHY followed by STARGRAZER and selected against MOZARK and BARCEL. KENTUCKY 31, HIMAG, MO-96, and C1 were intermediate. In all five experiments, the general association was positive for available carbohydrate fractions and negative for fiber fractions that contribute to cell wall rigidity.

Absorption and distribution of selenium in animals consuming canola grown for selenium phytoremediation.

Canola (Brassica napus) grown as a selected plant species for field phytoremediation of selenium (Se) may be harvested and utilized as Se-enriched forage for marginally Se-deficient lambs and cows. Two field studies were conducted under controlled conditions to evaluate the accumulation of Se into different animal tissues, including blood, excreta, and milk. In Study 1, treatments consisted of feeding lambs freshly cut Se-enriched canola (containing approximately 4 mg Se kg(-1) DM) or control canola (containing <0.1 mg Se kg(-1) DM), respectively, for 64 days. In Study 2, treatments consisted of feeding cows dried Se-enriched canola (containing approximately 3.5 mg Se kg(-1) DM) as part of their daily ration for 20 days. In Study 1 at postmortem, Se concentrations were significantly greater in all tested tissues and in excreta from lambs fed Se-enriched canola. In Study 2, Se values were slightly higher in blood and excreta, but not significantly higher in milk from cows sampled throughout the study. Significant differences in total live animal weight were not observed between treatments in either study. Based on these results, canola plants (not including seeds) used for field phytoremediation of Se may be harvested and safely fed to lambs and cows to help meet normal Se intake requirements.

Variation in ruminants' preference for tall fescue hays cut either at sundown or at sunup.

Plants vary diurnally in concentrations of nonstructural carbohydrates. If ruminants prefer forages with higher total nonstructural carbohydrates (TNC), then the preference for hays harvested within the same 24-h period may vary. An established field of tall fescue (Festuca arundinacea Schreb.) was harvested six times in the vegetative stage. Harvests were paired such that each cutting at sundown (PM) was followed by a cutting the next morning at sunup (AM). We harvested in this manner three times, resulting in six hays. The hays were field-dried, baled, and passed through a hydraulic bale processor prior to feeding. Experiments were conducted with sheep, goats, and cattle, using six animals in each case. During an adaptation phase, hays were offered alone as meals. In the experimental phase, every possible pair of hays (15 pairs) was presented for a meal. Data were analyzed by multidimensional scaling and by traditional analyses. Multidimensional scaling indicated that selection was based on a single criterion. Preference for PM hays was greater than for AM hays (P < .01) in all experiments. Increased preference was associated with increased TNC (P < .01) and in vitro true DM disappearance (P < .01) and decreased fiber concentration (P < .01; NDF, ADF, cellulose, and ADL). Mowing hay late in the day was effective in increasing forage preference.

Comparative toxicity of selenium from seleno-DL-methionine, sodium selenate, and Astragalus bisulcatus in pigs.

Selenium is an essential micronutrient, although ingestion in excess in pigs can cause disease conditions including neurological dysfunction and chronic skin and hoof lesions. Controlled feeding trials in growing swine, using the same Se content in feed sources, resulted in higher concentrations (p < or = 0.05) of Se in blood and organs of pigs fed seleno-DL-methionine compared with those receiving Astragalus bisulcatus or sodium selenate. Clinical signs of Se toxicity including neurological signs of paralysis were more severe and occurred sooner in the A. bisulcatus group than in the sodium selenate or seleno-DL-methionine groups. All five pigs fed A. bisulcatus developed neurological signs of paralysis, and in four the signs occurred within 5 days of the start of treatment. Four of five pigs fed sodium selenate also developed paralysis, but this occurred 4 to 21 days after treatment began. The fifth pig in the group developed signs of chronic selenosis. Two of five pigs fed seleno-DL-methionine developed paralysis on 9 and 24 days, respectively, and the remaining three developed chronic selenosis. Selenium fed to pigs in three forms [plant (A. bisulcatus), sodium selenate, or seleno-DL-methionine] resulted in neurological dysfunction and lesions of symmetrical poliomyelomalacia. These were most severe in the A. bisulcatus group, which also had polioencephalomalacia. Although seleno-DL-methionine caused the greater increase in tissue and blood Se concentrations, this did not correlate with severity of pathological changes, since animals fed A. bisulcatus developed more severe and disseminated lesions.

Reproductive response of ewes fed alfalfa pellets containing sodium selenate or Astragalus bisulcatus as a selenium source.

Selenium fed to open cycling ewes in the form of sodium selenate or Astragalus bisulcatus (a selenium accumulator plant) at 24 or 29 ppm selenium, respectively, in alfalfa hay pellets did not alter the estrous cycle length, estrus behavior, progesterone or estrogen profiles, pregnancy rate or outcome of parturition (P > 0.05). There was wool loss in some ewes fed seleniferous pellets and the mean whole blood selenium levels were 0.45, 1.3 and 2.4 ppm, respectively, for control, A bisulcatus and sodium selenate; however, ewe condition and appearance remained good. All lambs appeared normal and the number of lambs born and the individual and total lamb weight averages were not significantly (P > 0.05) different between treatment groups and control group.

Using plant breeding and genetics to overcome the incidence of grass tetany.

Plant breeders developing cultivars to minimize the hazards of grass tetany are concentrating largely on increasing herbage Mg concentrations in cool-season (C3) grasses. Significant genetic variation has been found for Mg, Ca and K concentrations within C3 grass species studied to date. For most C3 forage grass species, heritability estimates are highest for Mg, slightly lower for Ca and lowest for K concentrations. The largest genotype x environmental interactions are found for K values, whereas small environmental effects have been observed for Mg and Ca values. No C3 forage grass cultivar has been developed to date that would eliminate hypomagnesemia. Grass breeders need to develop more experimental C3 plant populations that have high Mg and Ca concentrations. These experimental synthetics with genetically altered mineral concentrations need to be fed to ruminants susceptible to grass tetany to determine whether grass tetany can be eliminated or reduced. Limited feeding trials using ruminants show that improved animal performance can be expected when feeding forage grasses bred for higher Mg concentrations.

Effects of excess dietary selenite on lead toxicity in sheep.

The hypothesis that excess dietary selenite ameliorates lead (Pb) toxicosis in domestic sheep was tested. Twenty 6-8-yr-old ewes fed alfalfa pellets were assigned to the following treatments: (1) control; (2) 9.8 mg Pb/kg body weight (b.w.)/d as PbCO3; (3) 3 mg Se/animal/d as Na2SeO3·5H2O; or (4) a combination of treatments 2 and 3. The gelatin-encapsulated salts were given orally. The study was terminated on d 104, by which time three animals in the Pb group and all five animals in the Pb+Se group had died. All remaining animals were slaughtered on d 104. Lead and Se concentrations were determined in six biweekly-collected blood samples and in soft tissues and bone. Sheep on the control and Se treatments had similar feed intakes, body weights, and tissue Pb levels. Those in the Pb+Se group had lower feed intake, but higher blood Pb values compared with the Pb group. Feeding either element increased (P<0.05) the concentration of that element in blood, kidney, liver, spleen, and bone. Muscle-Pb concentrations were not affected (P<0.05) by treatment. Selenium concentrations in kidney, liver, and muscle were greater (P<0.05), whereas those in heart were less (P<0.05) for the Pb+Se group than for the Se Group. Clinical signs associated with Pb toxicosis noted in other animals were not observed in the poisoned sheep in this study. Selenite did not protect sheep against Pb toxicity and likely served as a synergistic factor.

Grazing cow and calf responses to zinc supplementation.

This experiment evaluated weight gain responses to supplemental Zn by cows and calves grazing forage containing less than 20 ppm Zn. One hundred cow-calf pairs in each of 2 years and 120 paird in a third year were pastured together over a 63- to 77-day preliminary period during which cows were exposed to bulls. Each experimental period began in mid-June after bulls were removed and continued for 125 to 154 days. During this period, cattle grazed mature dry forage containing less than 20 ppm Zn and were fed protein supplements with or without added Zn. Estimated Zn intake by each cow-calf pair in the control group ranged from about 140 to 260 mg/pair/day. Daily Zn intake was supplied by forage (100 to 200 mg), basal supplement (32 to 57 mg), water (4 mg), iodized block salt (1 mg) an soil (1 mg). Each cow-calf pair fed the supplement with added Zn received an additional 860 to 900 mg Zn/day. Calves fed Zn gained 6% more (P less than .05) weight (.04 kg/day) between the two groups. Clinical signs of Zn deficiency were not observed in any animals. Conception which occurred before the experimental period, and subsequent calving rates were not affected by Zn supplementation.