Diurnal shifts in nutritive value of alfalfa harvested as hay and evaluated by animal intake and digestion

Forages accumulate nonstructural carbohydrates during the day, with animals showing preference and improved daily responses from afternoon compared with morning cut hays. This study evaluated alfalfa (Medicago sativa L.) hay harvested at 0700, 1000, 1300, 1600, and 1900 h to determine how nutritive value changes during the day and to assess the impact of these changes on animal preference using cattle (Bos taurus L.), sheep (Ovis aries L.), and goat (Capra hircus L.) responses. Total nonstructural carbohydrates were altered by time of cut (cubic contrast, P < 0.01) ranging from 85 g kg?1 at 0700 h to 83 g kg?1 at 1000 h, then increasing to 97 g kg?1 by 1600 h with little change at 1900 h (96 g kg?1). Fiber fractions also varied diurnally, with a quadratic decrease from 418 g kg?1 at 0700 h to 387 g kg?1 by 1900 h in neutral detergent fiber. A combined analysis of three animal trials showed a linear increase in dry matter intake (DMI) with later hay harvest, a cubic response for dry matter digestion (DMD), and a linear increase in digestible DMI. Mean DMI increased from 27.5 g kg?1 body weight at 0700 h to a maximum of 30.8 g kg?1 body weight at 1600 h, whereas DMD decreased from 658 g kg?1 at 0700 to 647 g kg?1 at 1300 h and peaked at 664 g kg?1 at 1600 h. Digestible DMI increased from 18.1 g kg?1 body weight at 0700 h to a maximum of 20.5 g kg?1 body weight at 1600 h. No additional advantages in animal responses were noted by cutting after 1600 h

Dry matter uptake 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 <or= 0.01). Steer DMI and digestible DMI were associated with preference (r = +0.83, P <or= 0.05; and r = +0.89, P <or= 0.05) and with coordinates for preference criteria (dimension 1; r = +0.90, P <or= 0.05; and r = +0.89, P <or= 0.05) from a previous preference trial. Intake and digestion responses for goats and sheep showed no relationship with the previous preference trial measurements. For cattle and goats, the management strategy of mowing in the afternoon seems to take advantage of small, but influential diurnal changes in the soluble carbohydrate fraction and offers the potential to improve forage quality

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 Cl 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

Ruminant selection among switchgrass hays cut at either sundown or sunup

As a result of photosynthesis, plants typically have greater concentrations of nonstructural carbohydrates at the end of the photoperiod. The preference of ruminants for hays harvested within the same 24-h period can be greater for plants harvested late in the photoperiod with increased soluble carbohydrate. To test for variation in ruminant preference for afternoon versus morning harvested hays in a C4 grass harvested in the humid east, established fields of 'Kanlow' and 'Alamo' switchgrass (Panicum virgatum L.) were used to produce hays in 1998, 1999, and 2000 near Raleigh, NC. Harvests were paired so that each cutting in the evening (PM) was followed by a cutting the next morning (AM). We harvested in this manner three times in 1998 to produce six Kanlow hays; twice with Kanlow and once with Alamo at two levels of nitrogen fertility in 1999 to produce eight hays; and three times in 2000 to produce six Alamo hays. The hays were field-dried, baled, and passed through a hydraulic bale processor. Hays from each year were tested with cattle (Bos taurus L.), goats (Capra hircus L.), and sheep (Ovis aries L.). During an adaptation phase, hays were offered individually. In the experimental phase, all possible pairs of hays were presented. Data were analyzed by multidimensional scaling and by traditional analyses. Multidimensional scaling indicated that selection was based on multiple criteria. The suite of improvements associated with PM-harvested hays in fiber content, digestibility, and nonstructural carbohydrate observed for alfalfa and fescue hays in the western USA was difficult to reproduce with switchgrass hay in the southeastern USA. This difficulty is likely related to the less favorable environment for haymaking as well as the physiology, anatomy, and morphology of this C4 grass

Herbivore preference for afternoon- and morning-cut forages and adoption of cutting management strategies

Photosynthesizing forage plants accumulate total nonstructural carbohydrates (TNC) during daylight, but then TNC concentrations are reduced during the night. Afternoon-cut forage (PM) has greater TNC value and thus economic value, than morning-cut (AM). Livestock prefer PM-cut hay and this can be readily demonstrated by offering animals a choice of hays cut in PM and AM. Alfalfa growers in the western United States are readily adopting PM-cutting technology to increase profits

Morning and evening harvest effects on animal performance

Plants vary diurnally in concentrations of nonstructural carbohydrates (TNC). Delaying forage harvest until mid to late afternoon could result in increased TNC in forage. Ruminants can differentiate between PM-harvested and AM-harvested grass and alfalfa hays and eat more PM-harvested versus AM-harvested hay. In a related study, dairy cows ate about 10% more total mixed ration containing 40% PM-harvested alfalfa hay versus the same ration containing AM-harvested hay, produced more milk, and gained rather than lost body weight. Afternoon harvest management could add $15/ton of alfalfa compared with morning harvesting

Diurnal variation in forage quality affects animal preference and production

In 1993. we began to evaluate animal grazing preferences among eight tall fescue cultivars, including HiMag which had been selected to reduce risk of grass tetany. Two years of preference studies indicated that some cultivars were better liked by heifers than other cultivars (Shewmaker et al., 1997). One of us (jcb) and others asked WHY. This led to quantifying various chemical and physical characteristics of these cultivars and determining their relationship to grazing preference. It also led to an evaluation of animal preference among these same tall fescues when harvested in late afternoon and conserved as hay (Burns et al., 'a', submitted J. Anim. Sci.). In the grazing study. we had found a close relationship between total nonstructural carbohydrate (TNC) levels and animal grazing preferences among the cultivars (Mayland et al.. `c', revised for Agron. J.). However, TNC values change during the day. What effect might variation in harvest time have on TNC concentration and ultimately animal preference? This diurnal cycling of forage sugars had been known for many years, but had been dismissed as not affecting feed value or animal behavior. We checked the literature (August 1996) but found no documentation of animal responses to diurnal changes in forage composition. The challenge seemed obvious and the potential impack seemed great; so we decided to test ruminant animals' ability to differentiate between hays harvested in afternoon and subsequent morning. We completed several studies and will share some exciting results with you. Animals demonstrated strong preference for afternoon-harvested compared to morning-harvested forage. This led to questions concerning 1) animal preferences among other forage types and cultivars, 2) more detailed characterization of diurnal changes occurring in forages, 3) affects on energy and crude protein digestibility, and 4) affects on animal production? Could ruminants distinguish between evening- and morning-cut hay and did this occur over a range of conditions? If they could, then we needed to know what was going on in the plant. We would then need to determine management strategies to take advantage of possible benefits. We first discuss the animal studies and then close with plant studies

Near infra-red measurement of nonstructural carbohydrates in alfalfa hay

Recently documented benefits from afternoon versus morning cut forage have encouraged laboratory reporting of total nonstructural carbohydrate (TNC) values as part of forage quality testing. Our objective was to determine if infra-red spectroscopy (NIRS), which is being used in many forage testing labs, could be reliably used to quantify forage sugars in hay samples. We used two alfalfa (Medicago sativa L.) sample populations that were analyzed by wet chemistry for sugars and scanned by NIRS. The first set consisted of field-dried hay samples that were oven dried at 70°C and the second consisted of fresh, freeze-dried samples. TNC values were determined more precisely with NIRS than by wet chemistr

Forage volatiles as cues for ruminants

Forage volatiles may provide cues that affect animal food choices. Collecting and identifying these compounds is challenging. The authors briefly describe the methodology and report several volatile compounds that relate to animal preference

A glassy contribution to the heat capacity of hcp 4^4He solids

We model the low-temperature specific heat of solid $^4$He in the hexagonal closed packed structure by invoking two-level tunneling states in addition to the usual phonon contribution of a Debye crystal for temperatures far below the Debye temperature, $T < \Theta_D/50$. By introducing a cutoff energy in the two-level tunneling density of states, we can describe the excess specific heat observed in solid hcp $^4$He, as well as the low-temperature linear term in the specific heat. Agreement is found with recent measurements of the temperature behavior of both specific heat and pressure. These results suggest the presence of a very small fraction, at the parts-per-million (ppm) level, of two-level tunneling systems in solid $^4$He, irrespective of the existence of supersolidity.Comment: 11 pages, 4 figure