Heat- and lignosulfonate-treated canola meal as a source of ruminal undegradable protein for lactating dairy cows.

This experiment used 18 lactating Holstein cows in a 3 x 3 Latin square replicated 6 times to determine the effectiveness of processing with moist heat or moist heat combined with lignosulfonate (LSO3) for increasing the ruminal undegradable fraction of canola meal for use as a protein supplement for lactating dairy cows. Diets were formulated to be isonitrogenous and contained one of 3 forms of canola meal; untreated canola meal (UCM), heat-treated canola meal (HTCM) or heat-and LSO3-treated canola meal (LSO3CM). Total collection of urine and feces was taken from each cow during the last 5 d of each 42-d experimental period. Milk production was greater for cows fed the LSO3CM diet (36.6 kg/d) than for cows fed the UCM diet (34.8 kg/d) but did not differ from cows fed the HTCM diet (35.3 kg/d). Digestibility of crude protein was lower for cows supplemented with LSO3CM and they had reduced concentrations of ruminal ammonia N, blood urea N, and milk urea N compared with cows supplemented with UCM or HTCM. Dry matter intake and apparent digestibilities of neutral and acid detergent fiber were increased in cows fed the LSO3CM diet. Urinary N excretion (as % of N intake) was reduced in cows fed the LSO3CM diet. These results indicate that moist heat combined with LSO3 treatment of canola meal was effective in increasing the proportion of crude protein digested in the lower digestive tract of lactating cows and was therefore used more effectively as a source of protein than UCM or HTCM.

Bacterial populations on teat ends of dairy cows housed in free stalls and bedded with either sand or sawdust.

The main objectives of the experiment were: 1) to compare bacterial populations of mastitis-causing organisms on the teats of lactating dairy cattle housed on sand and sawdust bedding and, 2) to examine the relationship between bacterial counts present in the 2 bedding types with those on teat ends. Sixteen lactating Holstein cows were housed on either sand or sawdust-bedded free stalls using a crossover design with 3 wk per bedding type. Bedding samples were collected on d 0 (prior to animals lying on the bedding), 1, 2, and 6. Teat ends were sampled prior to the morning milking on d 1, 2, and 6. All samples were analyzed to determine coliform, Klebsiella spp., and Streptococcus spp. populations. There were 2 times more coliforms and 6 times more Klebsiella bacteria on teat ends of cows housed on sawdust compared with those housed on sand. In contrast, there were 10 times more Streptococcus spp. bacteria on teat ends of cows when housed on sand compared with sawdust. In both sawdust and sand bedding, coliforms, Klebsiella and Streptococcus counts increased over each experimental week, although patterns varied with bedding and bacteria type. Bacterial counts on teat ends were correlated with bacterial counts in sawdust (r = 0.47, 0.69, and 0.60 for coliforms, Klebsiella spp., and streptococci, respectively) and in sand (r = 0.35 for coliforms and r = 0.40 for Klebsiella spp.). In conclusion, coliforms and Klebsiella spp. on teat ends were more numerous when cows were housed on sawdust bedding, but Streptococcus spp. were more numerous on teat ends of cows housed on sand.

Fibrolytic enzymes and parity effects on feeding behavior, salivation, and ruminal pH of lactating dairy cows.

Four multiparous and four primiparous lactating dairy cows fitted with ruminal cannulas were used in a duplicated 4 x 4 Latin square design to study the effects of parity and inclusion of a fibrolytic enzyme product (Agribrands International, St. Louis, MO) on feeding and chewing behavior, salivation, and ruminal pH. Diets consisting of rolled barley, barley silage, and alfalfa haylage (55% forage, DM basis) differed in enzyme application: 1) control, 2) enzyme applied to concentrate (45% of TMR), 3) enzyme applied to supplement (4% of TMR), and enzyme applied to a premix (0.2% of TMR). Enzyme supplementation did not alter daily time spent eating or ruminating, but when enzymes were added to the ration daily, saliva production increased, with no difference among enzyme application treatments. Multiparous cows consumed a greater amount of feed, but spent a similar amount of time eating, compared to primiparous cows. Primiparous cows had shorter ruminating episodes, resulting in lower daily ruminating time compared with multiparous cows. Primiparous cows had lower daily saliva output compared with multiparous cows. These results indicate that application of this fibrolytic enzyme product did not alter the physical structure of the feed, as measured by feeding and chewing variables. The increase in total saliva production observed in cows fed enzyme-supplemented diets may be attributed to a physiological response to compensate for the increase in fermentation products during digestion. The increased intake for multiparous cows is attributed to increased eating rate and not to increased time spent eating. The higher DMI of multiparous cows resulted in increased rumination time needed to process the additional feed and increased salivation to buffer the greater production of VFA.

The proportion of the diet to which fibrolytic enzymes are added affects nutrient digestion by lactating dairy cows.

Eight lactating Holstein cows, four with ruminal cannulas, were used in a duplicated 4 x 4 Latin square design to investigate a fibrolytic enzyme product characterized by xylanase and cellulase activities (Promote N.E.T. Agribrands International, St. Louis, MO). The diet consisted of concentrate containing rolled barley and supplement, barley silage and alfalfa haylage (55% to 45% DM basis, forage to concentrate ratio) and differed in enzyme application: 1) control, 2) enzyme applied to concentrate (45% of TMR), 3) enzyme applied to supplement (4% of TMR), and 4) enzyme applied to premix (0.2% of TMR). All diets that were supplemented with the enzyme product delivered about 1.0 grams per cow per day. Digestibility of OM, NDF and ADF in the total tract was increased in comparison to the control when enzymes were added to the entire concentrate. Enzyme treatments that were applied to a smaller portion of the diet showed only numerical increases in digestibility over the control. However, there was an increase in microbial N synthesis for cows fed enzymes added to the premix. The effects of enzyme supplementation on milk production and composition were not statistically significant, but cows receiving the enzyme product added to the concentrate had a numerically higher FCM compared to the control cows. These results indicate that enzyme supplementation increases total tract digestibility of organic matter and fiber. The proportion of the diet to which the enzyme is applied must be maximized to ensure a beneficial response.

Effects of Tween 60 and Tween 80 on protease activity, thiol group reactivity, protein adsorption, and cellulose degradation by rumen microbial enzymes.

Microbial enzymes extracted from mixed ruminal microorganisms were incubated for 2 h with casein and Tween 60 or Tween 80 at 10 concentrations ranging from 0 to 2.0% (vol/vol) to determine the effects of these nonionic surfactants on protease activation and thiol reactivity (unmasking of thiol groups). Rate and extent of protein adsorption to cellulosic substrate (barley straw) was measured in the presence of 0, 0.05, 0.10, 0.25, and 0.50% (vol/vol) Tween 80. Degradation of cellulose by a rumen bacterial fraction was measured over 48 h of incubation with and without Tween 60 or Tween 80 at 0.25% (vol/vol). Maximum accelerations of protease activity achievable with Tween 60 and Tween 80 (calculated from a Michaelis-Menten kinetics model) were 99.2 and 166.8%, respectively. Concentrations of Tween 60 and Tween 80 at which half the maximal velocities were attained were 0.28 and 0.20% (vol/vol), respectively. Tween 80 increased (P < 0.05) the rate and extent of adsorption of microbial protein to barley straw, and the effect was related to concentration of Tween 80 up to 0.10% (vol/vol). Initial rates of cellulose degradation with no surfactant, 0.25% Tween 60, or 0.25% Tween 80 were 0.60, 0.87, and 1.04 micrograms/ml per h, respectively. These nonionic surfactants were effective for enhancing rumen microbial protease and cellulase activities. Thus, further study is warranted to determine their potential for improving ruminant feeding.

In situ disappearance of amino acids from grass silages in the rumen and intestine of cattle.

Nineteen grass silages were evaluated using the in situ rumen and mobile nylon bag techniques to determine the amino acid (AA) composition of rumen-undegradable protein and the possibility of predicting the concentrations of individual AA presented to the duodenum from the dietary AA profiles. All feeds and residues from the nylon bags were analyzed for diaminopimelic acid to correct for contamination by microbial proteins. All essential AA behaved similarly; the initial feed had the highest concentrations, and the material remaining in the mobile nylon bag had the lowest concentrations. The reduction in the concentration of methionine between the 12-h rumen residue and the residue in the mobile nylon bag was significant. With the exception of arginine (r2 = 0.76) and serine (r2 = 0.82), the relationship was poor between the concentrations of AA in the grass silage and those in the residue in the nylon bag following 12 h of rumen incubation. The lack of reliable relationships between concentrations of individual AA in the silages and concentrations of AA in the 12-h rumen residue indicated that degradability characteristics of AA in grass silage were not alike. This poor relationship was likely the reason that prediction equations could not be developed between the AA composition of the initial feed and the pattern of AA presented to the duodenum following 12 h of rumen incubation. The AA composition of the rumen-undegradable portion of grass silages differs from the AA composition of grass silages.

Use of the Cornell net carbohydrate and protein system and rumen-protected lysine and methionine to reduce nitrogen excretion from lactating dairy cows.

A study was carried out to determine whether the addition of rumen-protected Lys and Met to ration formulations allowed a reduction in dietary crude protein (CP) without jeopardizing total milk or milk protein yields. Eighteen multiparous Holstein cows were randomly assigned to treatment sequences in a replicated 3 x 3 Latin square design. Total mixed rations were balanced according to degradation and rates of passage of protein and carbohydrates using the Cornell Net Carbohydrate and Protein System. Rations differed in percentages of CP (18.3, 16.7, and 15.3% for rations 1, 2, and 3, respectively), but energy was held constant. Rations 2 and 3 were supplemented with rumen-protected Lys and Met. Milk, blood, and rumen fluid samples were taken during the 2nd and 3rd wk of each 28-d experimental period. Total collection of urine and feces occurred during the last 5 d of each experimental period. Cows fed ration 1 had a higher milk yield (34.2 vs. 32.8 kg/d) and DMI than did cows fed rations 2 or 3, but milk protein output was not different among groups. Nitrogen efficiency, milk N as a percentage of intake N, improved as percentages of CP in the rations were reduced. Blood urea N values were 15.9, 12.9, and 10.0 mg/dl for cows fed rations 1, 2, and 3, respectively. Apparent digestibilities of CP and urinary N excretion decreased as the percentages of CP in the rations decreased. Results indicated that it is possible to make more efficient use of CP by using rumen-protected amino acids. This procedure may result in less than maximum milk yield, but milk protein output can be maintained.

Initial rates of degradation of protein fractions from fresh, wilted, and ensiled alfalfa.

Initial rates of in vitro degradation of alfalfa proteins were studied. Fresh, 24-h wilted, and ensiled forages were homogenized before analysis for total proteins. Some of the homogenates were fractionated by differential solubility in 10 and 40% ammonium sulfate, followed by ultrafiltration of the 40% salt-saturated solution. The protein fractions obtained were chloroplast membrane proteins (fraction 3), soluble proteins from plant cell cytoplasm and the chloroplast (fraction 2), and proteins remaining soluble in the extracted 40% salt-saturated solution (fraction 2B), respectively. Total and fraction 3 silage proteins were degraded faster than the respective fresh and wilted proteins. There were no treatment effects on the rates of degradation of the soluble proteins of fractions 2 and 2B. Protein fractions from fresh and 24-h wilted alfalfa degraded, from greatest to least, in the following order: fractions 2, 2B, and 3. Degradation rates for fractions 2 and 2B of ensiled forages were similar but greater than that of fraction 3. Alfalfa proteins were degraded rapidly in the rumen, and soluble proteins were degraded faster than the chloroplast membrane proteins. Ensiling of alfalfa increased the rate of degradation of chloroplast membrane proteins, but neither wilting nor ensiling affected degradation rates of the soluble protein fractions 2 and 2B.

Asbestos fibers and trace metals in the blood of cattle grazing in fields inundated by asbestos-rich sediments.

During a major storm in 1975, a pasture was inundated with serpentinitic sediments which are rich in asbestos fibers and trace metals. Little natural revegetation has occurred at the site and dairy and beef cattle which continue to graze in and around the contaminated site are exposed to asbestos fibers by inhalation and ingestion. The effect of this material on the cattle was investigated in this study by analyzing blood samples from exposed and control animals for asbestos fibers, trace metals, and general blood chemistry. The analysis showed that at the time of exposure Ni and Mn values were significantly higher in the exposed animals than in the controls, and in six out of seven samples asbestos fibers were present as determined by STEM analysis. Once the animals were removed from the site, trace metal levels returned to normal but asbestos fibers were still present in three out of seven animals. Two of the control animals unaffected by the sediments also showed asbestos fibers and there were no relationships between the magnitude of fibers and trace metal content. This suggests that the sediments influence the blood chemistry of animals but the presence and magnitude of asbestos fibers in the blood can be influenced by other factors as well.

Two housing systems for calves.

Thirty-six male Holstein calves were in an experiment with 2 X 2 factorial design with the objective of comparing management systems and milk feeding. Housing systems were similar except calves on A system were housed in pens .66 m wide with grated floors whereas calves on B system were in pens that were 1.36 m wide with solid floors bedded with straw. Within each management system nine calves were fed milk at 8% of body weight and nine calves at 12% of body weight. There was no interaction between management system and feeding percent. Preweaning calves fed more milk gained faster (.64 versus .50 kg/day) compared with calves fed less. Management system did not influence body weight gain or feed conversion prior to weaning, but postweaning A system resulted in slower gains (.74 versus .90 kg/day) and less favorable feed conversion (2.00 versus 1.77 kg dry matter intake/kg body weight gain) than calves housed under the B system. Eosinophil count was higher during 5th and 7th wk of the experiment for calves housed in A compared with B system. Measurements of body weight gain and feed conversion were effective in differentiating between two housing systems for calves.