A study was conducted to evaluate the effects of a direct-fed microbial (M) and dietary glycerol (G) on milk yield, efficiency of yield, and nutrient digestibility during hot weather. Sixty Holstein cows averaging 120 d in milk (DIM) and 36.2 kg/d of milk were used in a 12-wk 2×2 factorial design trial from June through September 2008. Cows were fed a common diet during the 2-wk standardization period and were blocked by milk yield, DIM, parity, and dry matter intake. Diets were based on corn and ryegrass silages and balanced to be isocaloric and isonitrogenous. Treatments included a negative control (M- or G-), 4 × 10(9) cfu/head of a combination of Lactobacillus acidophilus NP51 and Propionibacterium freudenreichii NP24 (M+), control plus 400 g/h per day of 99% pure food-grade glycerol (G+), and 4×10(9) cfu/h per day of a combination of Lactobacillus acidophilus NP51 and Propionibacterium freudenreichii NP24 plus 400 g/h per day of 99% pure food-grade glycerol (MG++). No interactions were observed between direct-fed microbials and dietary glycerol in the study except on apparent nutrient digestibility. No differences were observed in dry matter intake, which averaged 22.7, 23.1, 23.4, and 22.9 for M-, G-, M+, and G+, respectively. Milk yield was increased for M+ compared with M- at 34.1 and 31.7 kg/d, but G+ had no effect on yield. No treatment effect was noted for milk fat percentage or milk protein percentage among diets. Milk protein yield was higher for M+ compared with M- at 0.93 versus 0.87 kg/d. Energy-corrected milk was improved for the M+ versus M- groups at 33.5 and 31.6 kg/d, respectively. No differences in respiratory rate, skin temperature, body temperature, or concentrations of serum glucose or urea N were observed among treatments. Improvement in apparent digestibility was observed with M+ and G+ compared with M-/G- in this experiment. The addition of a direct-fed microbial alone improved milk and protein yield, energy-corrected milk, and apparent digestibility of crude protein, neutral detergent fiber, and acid detergent fiber, and the inclusion of glycerol (G+) had a positive effect on apparent dry matter and acid detergent fiber digestibility compared with M-/G-. The addition of a direct-fed microbial and dietary glycerol may improve yield and digestibility for cows subject to heat stress.

The water-soluble carbohydrates [glucose and fructose (reported together as total hexoses), sucrose and fructosan] in the leaf, stem and head portions of four grasses have been determined a t regular intervals throughout their growth cycle during two successive years.The concentration of sucrose varied with the stage of growth, rising to a peak in May-June, and the effect of the stage of growth on the amount of sucrose was similar in both leaf and stem. Fructosan was present in a much higher concentration in the stem than in the leaf, and stage of growth had a marked effect on the amount present. A relationship is suggested between these fluctuations in fructosan content and morphological changes, first in the development of the growing point from a vegetative to a floral state, and later in seed formation.Hexoses were a t all times present in only small amounts.It is well known that the stage of growth of grass is the major factor governing its chemical composition. The general trends and order of magnitude of the changes brought about by increasing age in such constituents as crude protein, crude fibre, ether extracts, ash and lignin are wellConsiderably less is known about the corresponding changes in the simpler carbohydrates, although, as ArchboldO mentions in his review, the fructosans of monocotyledons were extensively investigated during the period 1870-1900. Some account of the simpler sugars (glucose, fructose and sucrose) occurring in grasses was given by de C~g n a c ,~ but the fructosan content was obviously considered the most important. In a recent paper Laidlaw & Reida have suggested that melibiose, raffinose and stachyose are also present in small amounts. It is reasonable to suppose, moreover, that oligosaccharides intermediate in chain length between sucrose and fructosan may occur.Much of the earlier work on the carbohydrates of monocotyledons was concerned with cereals, and emphasis was naturally placed on the changes associated with emergence of the flower head and the setting of the seed. This attitude persisted somewhat when the carbohydrates in grasses were first investigated, and changes occurring in the early vegetative stages were neglected. Much of the work of the French school of Colin & de Cugnac' and de Cugnac5 thus deals mainly with the flowering and seed-setting stages of grasses. and Norman & RichardsonlO sampled both rye-grass (Lolium perenne) and cocksfoot (Dactylis glomerata) from a fairly early stage until after inflorescence and were impressed by the large amounts of fructosan present, particularly in rye-grass. Their method of drying the fresh material, however, was probably insufficient to stop enzyme action completely ; for this reason they discounted the free fructose found in many samples and apparently assumed sucrose to be absent, although they pointed out that some carbohydrate was unaccounted for. Thus it can be seen that the fructosan fraction received most attention and provided more purely chemical interest in the elucidation of its structurell? l2 than a consid...

A replicated 3×3 Latin square study was conducted to evaluate the effects of replacing a portion of ground corn in the diet with dietary glycerol on rumen environment, blood metabolites, and nutrient digestibility. Six rumen-cannulated Holstein cows, averaging 56±18 DIM and 38.0±8.2 kg of milk/d, were used in the study. Experimental periods included 3 wk for treatment adjustment period followed by 1 wk for data collection. Diets were corn silage based and balanced to be isocaloric and isonitrogenous. Treatments were 0 g of glycerol/d (control, CON), 200 g of glycerol/d (G2), and 400 g of glycerol/d (G4). Dry matter intake (DMI) decreased as the amount of glycerol fed increased. Milk yield was higher for CON and G2 cows in comparison with G4 cows. Milk fat percentage and yield were reduced when glycerol was fed compared with CON cows but increased the milk protein percentage at the highest concentration of dietary glycerol. These changes resulted in decreased energy-corrected milk yield and efficiency (milk/DMI) in diets supplemented with G4 compared with CON. No differences were observed in ruminal pH and ammonia concentrations. Molar proportions of acetate, valerate, and acetate:propionate ratio decreased, whereas propionate increased as the amount glycerol fed increased. Molar proportions of butyrate were greatest when glycerol was included in the diet compared with CON. Nutrient intake and digestion were not different among treatments. Results of this trial suggest that feeding increasing amounts of glycerol may decrease DMI and alters ruminal fermentation, resulting in reduced yield of milk, fat, and energy-corrected milk.

Four perennial grasses were cut with a motor mower each time they reached a height of about 8-10 in. during the growing seasons of 1951 and 1952. The water-soluble carbohydrates, glucose and fructose (reported together as free hexoses), sucrose and fructosan were determined in each cut. Grasses in which the growing point had recently changed to a floral development (in May or June) contained more carbohydrate than grass grown and cut later in the season. The primary reason for this was that the later grasses were more leafy, and, secondly, that their stems contained much less fructosan than those of the earlier cuts.In Part 11 the changes in the amounts of the water-soluble carbohydrates in four perennial grasses during their normal growth-cycle from April to October were described. These grasses passed through the flowering and seed-setting phases, and it was suggested that these physiological changes were probably responsible for the fluctuations jn the content of the major carbohydrate fraction, the fructosan, most of which was present in the stem. The content of free hexoses and sucrose varied with the stage of growth, but there was little difference either between the values for the different species or the values in the two successive years. The value of the free hexoses was low at all times of the season, whereas the sucrose content rose appreciably in May-June.Having thus established the trend of the carbohydrate changes associated with the continuous growth of grasses, we wished to investigate the composition of the soluble carbohydrates in grass such as would be used for grazing dairy cows. The present paper deals with the same four grasses used previously, but in the present experiments they were cut with a motor-mower whenever they had grown to a height of about 8-10 in. I t is realized that this did not closely resemble defoliation by animals on the widely used system of continuous grazing, but it would bear a fair resemblance to the removal of herbage by close-folded animals or in well-managed rotational grazing. ExperimentalThe grass plots used were part of those described in Part I, and consisted of rye-grass (Lolium perenne, strain S23), cocksfoot (Dactylis glomerata, strain sI43), meadow fescue (Festuca pratensis, strain S53) and timothy (Phleum pratense, strain S48) in their first and second harvest years (1951 and 1952). The plots received 2 cwt./acre each of potash (60% K,O) and superphosphate (18% P,O,) in February of each year, and a further I cwt./acre of each fertilizer in June. ' Nitro-Chalk ' (15.5% N) was applied as follows : z cwt./acre in April and 3 cwt./acre after each cut until August, when the amount was reduced to I cwt./acre after each cut. The plots had been divided into two ; one half of each grew on without check (as described in the previous experiment'), but the other half was cut whenever it reached a height of about 8-10 in. The grass was cut between 9 and 10 a.m. with an Allen motor-scythe. I t was considered that the height of the stubble left by this machine, 1-2 in.,...