Effects of parity, seasonal heat stress, and colostrum collection time postpartum on colostrum quality of Holstein cattle in an arid region.

The aim of this study was to determine effects of parity (primiparous vs. multiparous), seasonal heat stress at calving (summer vs. winter), and time postpartum on some parameters associated with colostrum quality in Holstein cows reared in the Sonoran Desert ecosystem. Forty-seven cows (11 primiparous and 36 multiparous) expected to calve during summer, and 46 cows during winter (14 primiparous and 32 multiparous) were randomly selected. Management and feeding before and after parturition were similar for cows in both seasons. After parturition, colostrum from all cows was evaluated for volume, weight, temperature, density, and content of fat, protein, solids non-fat (SNF), and immunoglobulins (IGG). Data were analyzed with a model that included effects of parity status, calving season, and time postpartum, as well as all interactions. Colostrum produced in summer was warmer (P < 0.01) by almost 6 °C than winter colostrum, while colostrum from multiparous was warmer (P = 0.02) by 1.2 °C than that produced by primiparous cows. Colostrum volume and weight were not impacted by parity, calving season or time postpartum. Density, protein, and SNF content in colostrum were higher (P < 0.01) in multiparous vs. primiparous cows, as well as at parturition (0 h postpartum) than at 12 h postpartum (P < 0.01). At calving (0 h), spring colostrum had higher fat content (P < 0.01) and lower (P < 0.01) IGG concentration than that collected in summer, and no difference (P > 0.05) between seasons was observed for these components at 12 h postpartum. Multiparous cows produced colostrum with higher (P < 0.01) IGG concentrations than primiparous cows. In conclusion, only 0-h colostrum and that from multiparous cows was categorized as "Excellent," meanwhile the colostrum produced under summer heat stress was characterized as "Good" with reduced fat content. While the lacteal secretion collected at 12 post-partum still classified as colostrum, substantially lower contents of IGG, protein, fat, and SNF decreased its classification to "Poor" from the classification of "Excellent" at 0 h postpartum.

Bioavailability of selenium in 'Jose' tall wheatgrass (Thinopyrum ponticum var 'Jose') hay as a substitute for sodium selenite in the diets of dairy cattle.

Due to its potential toxicity to wildlife, selenium (Se) is a highly regulated trace element in the San Joaquin Valley (SJV) of California. Tall wheatgrass (TWG) is a Se-accumulating, salt tolerant forage suitable for cropping systems which re-use agricultural drainage waters. Utilization of TWG hay as an alternative Se supplement for dairy cattle could reduce the importation of 'new' Se into the SJV in the form of sodium selenite (SS) diet supplements. Our study used Se-enriched (4.65 mg/kg DM) TWG hay as a Se source for lactating dairy cows and measured Se accumulation in milk, blood, urine and feces to assess its bioavailability using several indices. Using a 3×3 Latin Square design, three pens of ~310 cows each were fed a similar total mixed ration over 4 week periods, except for Se which was higher in TWG and SS diets (0.53 and 0.65 mg/kg DM) vs. Control diet (0.35 mg/kg DM). Feeding Se-enriched TWG increased blood Se by 6.4% over Control; whereas SS increased it by 4.8%, suggesting higher Se bioavailability for TWG vs. SS. Marginal Se outputs in milk, feces and urine were judged to be better indicators of bioavailability as they estimate Se specifically from supplemental SS or TWG hay. In milk, TWG cows expressed 3.0% of supplemented Se vs. 0.6% for SS cows, supporting higher Se bioavailability for TWG. In contrast, more supplemental Se was retained and not expressed in feces by the SS cows (72.5%) vs. TWG cows (55.1%) which suggested higher Se bioavailability for SS. Based on published guidelines, Se intakes were 'adequate' for cows in all treatment groups, but milk and fat production increased with Se supplementation suggesting that Control cows were Se-deficient to some extent. Collectively, results suggest that the Se in TWG hay had comparable bioavailability to Se in the base diet.

Impacts of dietary fat level and saturation when feeding distillers grains to high producing dairy cows.

This experiment was conducted to determine whether increasing the net energy (NEL ) of a total mixed ration (TMR) with mainly unsaturated fat from corn distillers dried grains with solubles (DDGS) vs. rumen inert (RI)-saturated fat has similar impacts on animal performance. The experiment was an incomplete Youden square with three treatments and four 28-days periods, completed on a large commercial dairy using three early lactation pens each with approximately 380 multiparity cows. The TMR for all treatments was the same, except for 150 g/kg dry matter (DM) of each TMR which contained 90 g/kg high-protein DDGS (HPDDGS) and 60 g/kg beet pulp (i.e. low-fat control diet; LFC); 150 g/kg DDGS (i.e. high-fat diet with unsaturated fat; HFU); or 111 g/kg HPDDGS, 20 g/kg beet pulp and 19 g/kg RI fat (i.e. high-fat diet with saturated fat; HFS). The DM intake was highest (p < 0.05) for HFU-fed cows. Milk, fat and true protein yields, as well as milk energy output, were higher (p < 0.01) when cows were fed HFS vs. HFU and LFC diets. Milk true protein concentration was lowest (p < 0.01) for HFS-fed cows, but milk fat % was lowest (p < 0.01) for HFU and highest (p < 0.01) for HFS-fed cows. There were numerous differences (p < 0.01) in milk fatty acid levels amongst diets. The increase in body condition score was lowest (p < 0.01) for LFC. Whole tract digestibility of acid detergent fibre was lower (p < 0.01) for LFC vs. HFS cows, and fat digestion was lowest (p < 0.01) for LFC-fed cows. This DDGS, high in unsaturated fatty acids, was fed at high levels (i.e. 152 g/kg DM) with little impact on animal performance vs. a lower fat control diet, although addition of an RI-saturated fat to create a diet with a similarly higher fat level resulted in higher animal productivity.

Grazing as an alternative for utilization of saline-sodic soils in the San Joaquin Valley: selenium accretion and performance of beef heifers.

Two experiments were conducted to evaluate Se accumulation and health of non-pregnant, non-breeding beef cattle grazing on forages with a high Se content due to irrigation with saline drainage water. Heifers grazed experimental pastures of "Jose" tall wheatgrass (TWG; Thinopyrum ponticum var. "Jose") and creeping wildrye (CWR; Leymus triticoides var. "Rio") for 190 days in Experiment 1 (2007) and for 165 days in Experiment 2 (2008). In experiment 1, mean Se concentrations were similar in TWG and CWR herbage (4.0 versus 3.7 ± 0.26 mg/kg dry weight; p=0.34) as was crude protein (113 versus 114 ± 7.9 g/kg dry weight; p=0.94). Concentrations of Se in blood increased by 300% during the grazing period, and were similar for heifers grazing the TWG or CWR pastures (0.94 versus 0.87 ± 0.03 mg/kg; p=0.89). Heifers grazing on TWG gained more body weight than did heifers grazing on CWR (0.59 versus 0.27 ± 0.07 kg/days; p<0.01). In experiment 2, concentration of Se (4.0 versus 2.8 mg/kg ± 0.19 mg/kg dry weight; p<0.01) and crude protein (79 versus 90 ± 5.6 g/kg dry weight; p<0.01) differed, for TWG and CWR, respectively. Within 20 days, Se concentrations in blood had increased by 300% and by nearly 200% in heifers grazing on TWG or CWR. All data cited are least square means ± standard error of the mean. Data from our two grazing seasons are consistent in demonstrating the safety of grazing beef cattle for a period of up to 6 months on TWG and CWR forages having high levels of Se due to irrigation with saline drainage water. This suggests that forage production using saline drainage water is a viable alternative for saline soils with limited potential for producing high value, salt-sensitive, crops.

Comparison of red clover and ryegrass silage for dry cows and influence on subsequent lactation performance.

The objective of this study was to investigate the use of red clover (RC) silage as a forage for dry dairy cows, primarily relative to its impact on tissue mobilization and repletion during the transition period and performance during the first 10 wk of lactation. Forty multiparous lactating Holstein-Friesian dairy cows were divided into 2 paired groups at 70 d before predicted calving dates; a subset (n = 8) of the cows were used for N and P balance measurements twice during the study. From the start of the experiment until 4 wk before predicted calving date all cows were offered ad libitum access to a ryegrass (RG) silage with no concentrate. At 4 wk before predicted calving date, one group of cows remained on the same diet, and the other group was changed to a diet of ad libitum access to RC silage. There was no difference in feed intakes, but CP intake was higher in cows fed RC silage, whereas ME intake was higher in cows fed RG silage. Cows fed RG silage gained more weight over the last 4 wk of the dry period (DP) than those fed RC silage, but there was no treatment effect on BCS. During the DP fecal N excretion was higher for cows fed RC silage, and there were no treatment differences in urine N excretion or overall N balance. At birth, calves from cows fed the RC silage were heavier. After calving, all cows were offered the same diet of ad libitum access to the same RG silage and a standard lactation concentrate. During the first 10 wk of lactation there was no difference in feed intake between the 2 previous treatment groups, and feed intake reached a maximum at approximately 4 wk of lactation. Cows on the RG treatment during the DP gained more longissimus dorsi muscle depth during the DP and retained it during early lactation. Mobilization of this muscle occurred before calving, indicating repartitioning of amino acids to other body tissues. There were no carryover effects of DP treatment on apparent partitioning of N from diet to milk, urine, or feces at wk 3 of lactation. Feeding RC silage during the DP had almost no impact on subsequent performance of dairy cows in early lactation, probably because the 2 silages were nutritionally very similar.

Functional nerve recovery after bridging a 15 mm gap in rat sciatic nerve with a biodegradable nerve guide.

Recovery of nerve function was evaluated after bridging a 15 mm sciatic nerve gap in 51 rats with a biodegradable poly(DL-lactide-epsilon-caprolactone) nerve guide. Recovery of function was investigated by analysing the footprints, by analysing video recordings of gait, by electrically eliciting the withdrawal reflex, by nerve conduction velocity and by electromyography (EMG). Sensory nerve function recovered as measured by electrostimulation. Motor nerve function partly recovered but electromyograms remained abnormal throughout the study. We conclude that functional reinnervation by regenerating axons occurs after bridging a 15 mm nerve gap with a biodegradable poly(DL-lactide-epsilon-caprolactone) nerve guide, but the walking patterns remain abnormal. Video analysis is a useful tool to record and analyse the walking patterns of rats. Further studies are necessary to investigate the possibility of obtaining selective reinnervation of specific muscles.

Type of cottonseed and level of gossypol in diets of lactating dairy cows: plasma gossypol, health, and reproductive performance.

Objectives were to determine effects of altering gossypol intake by feeding whole linted Upland (WUP) or a 1:2 blend of WUP and cracked Pima (BUPCP) cottonseed on plasma gossypol (PG) concentrations, reproduction, and health of Holstein cows. Cows, 813, on three dairy farms were assigned to one of two diets starting at 13 +/- 11 d in milk for a 170-d experiment. Diets contained 717 and 951 mg of free gossypol/kg of dry matter from WUP and BUPCP, respectively. Concentrations of PG, as well as the proportion of total gossypol (TG) as the minus isomer were higher for cows fed BUPCP vs cows fed WUP. Conception rate at the first postpartum artificial insemination did not differ between treatments. However, cows consuming the higher gossypol diet had reduced subsequent conception rates and a lower pregnancy rate. Incidence of abortions increased in the higher gossypol diet, and cows that aborted or remained open had higher PG concentrations. Increasing PG concentrations resulted in reduced conception rates and extended days open. The probability of conception after the first artificial insemination declined at a decreasing rate as the plasma TG increased. Incidence of health disorders were unaffected by gossypol intake and PG concentrations. Similarly, gossypol intake and PG concentrations had no effect on culling or mortality. Six cows died in each diet, and none had postmortem signs compatible with gossypol toxicity. Consumption of a high gossypol diet for 170 d had no effect on health of lactating dairy cows, but it increased PG concentrations and impaired reproductive performance.

Increasing dietary levels of cracked pima cottonseed increase plasma gossypol but do not influence productive performance of lactating Holstein cows.

Lactating Holstein cows were fed diets with increasing levels of cracked Pima cottonseed to determine its effects on plasma gossypol concentrations as well as milk yield and composition and dry matter (DM) intake in a short-term study. All diets contained 12.8% cottonseed, 43.5% concentrate, and 43.7% chopped alfalfa hay on a DM basis. The proportion of whole Upland cottonseed to cracked Pima cottonseed in the four dietswas 100:0, 67:33, 33:67, and 0:100. Four primiparous cows were fed the diets in a 4 x 4 Latin square design, and three multiparous cows were fed the diets in a Youden square design with five periods. All periods were 35 d. Upland and cracked Pima cottonseed contained 0.64 and 1.00% total gossypol (DM) with 41 and 52% of gossypol as the (-) isomer, respectively. Gossypol is a natural defense compound in the plant that protects it against pests and diseases, but can have antinutritional quality effects when consumed by dairy cattle. Total plasma gossypol concentrations increased linearly with increasing proportions (100:0, 67:33, 33:67, and 0:100) of cracked Pima cottonseed in the diet for primiparous (4.4, 6.0, 7.7, and 8.9 microg/ml) and multiparous (4.3, 7.3, 9.7, and 11.4 microg/ml) cows, respectively. While primiparous cows responded similarly to gossypol intake, the response of plasma gossypol intake in multiparous cows differed among cows. This indicates the importance of animal variation when relating plasma gossypol levels with gossypol intake. Milk yield, as well as its components and DM intake, were not affected by increasing dietary inclusion levels of cracked Pima cottonseedup to 8.6% of DM intake for either primiparous or multiparous cows, even though plasma gossypol concentrations increased sharply over this dietary inclusion range. Although the highest dietary inclusion level of Pima cottonseed (i.e., 12.8%) numerically depressed performance of cows of both parities, these differences failed to reach statistical significance in these short-term trials with few cows.

Type of cottonseed and level of gossypol in diets of lactating dairy cows: effects on lactation performance and plasma gossypol.

Objectives were to determine the effects of feeding whole linted Upland (WUP) and cracked Pima cottonseed (BUPCP) to lactating cows on plasma gossypol concentrations and lactation performance. Holstein cows (n = 813) from three commercial dairies were assigned to one of two diets starting at 13+/-11 d in milk (DIM) for a 170-d experimental period. Cottonseed was included at 10% of the diet dry matter, and treatments consisted of replacing WUP with a 1:2 blend of BUPCP. Blood was collected from all cows at 61 and 91 DIM and from a subset of 56 cows on one dairy at 10, 33, 61, 91, 120, and 152 DIM. Intakes of free gossypol increased 32% in cows receiving the BUPCP diet, and concentrations of total gossypol (TG), as well as the proportion of TG as minus (-) isomer in plasma, were higher for cows fed BUPCP than WUP. Plasma TG increased linearly with increasing DIM, but cows fed the BUPCP, especially multiparous cows, had a higher increase in plasma TG over time. Yields of milk and milk components did not differ between the two treatments, although, yields of milk and milk components were greater in cows with higher plasma TG. Replacement of WUP cottonseed with BUPCP cottonseed increased plasma gossypol, but dry matter intake and yields of milk and milk components were not affected.

Influence of close-up dry period protein supplementation on productive and reproductive performance of Holstein cows in their subsequent lactation.

Holstein cows on a commercial dairy were assigned to close-up dry groups and offered an 11.7% crude protein (CP) ration based on corn silage, alfalfa cubes, oat hay, corn, and barley grain without (Control; C) or with (Supplemented; S) 0.8 kg/d per cow of a high CP supplement of SoyPass, distillers dried grains, ring dried blood meal, feather meal, and corn gluten meal. Heifers (C: 37, S: 44) and mature cows (C: 96, S: 81) were allocated to one of four groups based upon their time in the close-up groups (i.e., 1 to 4, 5 to 8, 9 to 12, and 13 to 19 d) within parity (i.e., heifers or mature) for statistical analysis. Full lactation means of all response parameters for cows confirmed to be pregnant that completed a lactation (i.e., lactating at 305 d in milk or dried off before 305 d in milk but not culled; C: 28, S: 23 for heifers and C: 48, S: 43 for mature cows) were analyzed by ANOVA. Lactation curves were evaluated by parallel curve analysis to assess differences in lactation curve shape, and curve separation, due to treatments. Protein supplementation had no impact on full-lactation milk or milk component yields of heifers, determined by ANOVA, although parallel curve analysis showed higher milk and milk protein yield with protein supplementation. As the number of days cows spent consuming their assigned close-up dry rations increased, heifers produced more milk, milk fat and milk protein, although the maximum yield for milk and milk protein occurred for those fed close-up rations for 9 to 12 d. For mature cows, neither time close up or close-up period protein supplementation influenced any mean response parameter, by ANOVA, although parallel curve analysis showed higher milk and protein yield for supplemented cows as time close up increased. Overall, results suggest the optimum close-up period length was 9 to 12 d, with a protein content intermediate between 11.7 and 14.4% of DM, for heifers. In contrast, results do not support any substantive benefit of a close up period, or protein contents above 11.7%, for mature cows.

Influence of abomasal infusion of high levels of lysine or methionine, or both, on ruminal fermentation, eating behavior, and performance of lactating dairy cows.

Four multiparous late-lactation Holstein cows were fed a basal ration designed to be co-limiting in intestinally absorbable supplies of methionine and lysine. Cows were supplemented with no amino acids, lysine by abomasal infusion to 140% of the calculated intestinally absorbable requirement, methionine by abomasal infusion to 140% of requirement, or both amino acids in a 4 x 4 Latin square design with 28-d periods. Unsupplemented cows consumed 23.8 kg/d of dry matter and produced 36.9 kg/d of milk containing 3.70% fat, 3.22% protein, and 4.82% lactose. Cows ate less dry matter and produced less milk and milk lactose, and tended (P = .06 or .08) to produce less milk protein when abomasally infused with methionine alone or together with lysine. Infusion of lysine alone resulted in production values numerically between those of unsupplemented cows and those cows supplemented with methionine alone or together with lysine. Evaluation of the results with two metabolic models of dairy cows indicated that performance of unsupplemented cows may have been limited by delivery of metabolizable or digestible protein, or intestinally absorbable lysine, isoleucine, or histidine, depending on the metabolic model used to evaluate animal performance. Regardless, results are consistent with those using nonruminant species, which have shown that imbalanced profiles of intestinally absorbable amino acids are associated with reduced dry matter intake and animal performance. Results also show that negative effects on performance of lactating dairy cows can occur if methionine is supplied at levels substantially in excess of calculated intestinally absorbable requirements, either alone or together with lysine.

Functional assessment of sciatic nerve reconstruction: biodegradable poly (DLLA-epsilon-CL) nerve guides versus autologous nerve grafts.

The aim of this study was to compare functional nerve recovery after reconstruction with a biodegradable p(DLLA-epsilon-CL) nerve guide filled with modified denatured muscle tissue (MDMT), or an autologous nerve graft. We evaluated nerve recovery using walking track analysis (measurement of the sciatic function index [SFI]) and electrostimulation tests. Functional nerve recovery after reconstruction with a biodegradable p(DLLA-epsilon-CL) nerve guide filled with MDMT was faster when compared with nerve reconstruction using an autologous nerve graft. We conclude that in case of a short nerve gap in the rat, reconstruction can best be carried out using a p(DLLA-epsilon-CL) biodegradable nerve guide filled with MDMT.

Influence of postruminal supplementation of methionine and lysine, isoleucine, or all three amino acids on intake and chewing behavior, ruminal fermentation, and milk and milk component production.

Four multiparous Holstein cows were fed a basal diet balanced with the Cornell Net Protein and Carbohydrate System (CNCPS). Diets were formulated to be co-limiting in intestinally absorbable supplies of methionine, lysine, and isoleucine. Cows were supplemented with no amino acids (control); lysine and methionine in a ruminally protected form; isoleucine by abomasal infusion; or lysine, methionine, and isoleucine in a 4x4 Latin square arrangement of treatments with 28-d periods. Performance of cows on all treatments was lower than expected due to low intake of DM that could have been caused by the high fiber level of the basal diet. This high fiber level was likely responsible for the high daily chewing times for cows fed all diets, which was consistent with the high ruminal pH values. Intake of DM and its components were not influenced by any treatment. Milk protein percentage tended to be higher when cows were fed diets supplemented with ruminally protected lysine and methionine; however, production of milk, milk fat, and milk lactose were not affected by any treatment. Cows tended to have a higher milk lactose proportion and tended to produce more milk and milk lactose when they were abomasally infused with isoleucine alone. However, when cows were supplemented with all three amino acids, milk production and composition did not differ from that of cows fed the unsupplemented diet. Use of the CNCPS to evaluate the performance of the cows fed the unsupplemented diet suggested that these cows may have been colimited by intestinally absorbable supplies of lysine, isoleucine, and methionine in addition to metabolizable protein. Evaluation of the unsupplemented diet with an alternate model, Shield, suggested that cows fed the unsupplemented diet may have been colimited by intestinally absorbable supplies of lysine, isoleucine, and arginine. Results suggest that enhanced delivery of intestinally absorbable isoleucine may stimulate milk lactose synthesis.

Long-term evaluation of functional nerve recovery after reconstruction with a thin-walled biodegradable poly (DL-lactide-epsilon-caprolactone) nerve guide, using walking track analysis and electrostimulation tests.

This study was performed to evaluate the long-term functional nerve recovery after reconstruction of a 10-mm gap in the sciatic nerve of the rat, with a thin-walled nerve guide, composed of a biodegradable copolymer of DL-lactide and epsilon-caprolactone [p(DLLA-epsilon-CL)]. To evaluate both motor and sensory nerve recovery, walking track analysis and electrostimulation tests were carried out after implantation periods ranging from 3 to 52 weeks postoperatively. The first signs of both motor and sensory nerve recovery could be observed after 5 weeks. After 15 weeks, 70% of the sciatic function and 90% of the sensory nerve function had been recovered. After this period, the sciatic function index (SFI) did not improve further, whereas the sensory nerve function appeared to return to normal. When the results of the SFI measurements, minus those obtained from rats with severe automutilation, are extrapolated, further improvement of the SFI might be expected after 52 weeks. The fact that 100% sensory nerve recovery was obtained, as measured by the electrostimulation test, could be explained by sensory reinnervation from surrounding areas. The SFI was not fully reestablished because automutilation had a great impact on the use of walking track assessment.

Ruminally protected lysine or lysine and methionine for lactating dairy cows fed a ration designed to meet requirements for microbial and postruminal protein.

The purpose of this study was to separate the effects of ruminally protected Lys from effects of ruminally protected Met on the performance of lactating dairy cows fed a ration calculated to be first-limiting in intestinally delivered Lys and second-limiting in intestinally delivered Met. Thirty multiparous Holstein cows were examined in a 20-wk study that started on wk 5 postpartum. Rations contained timothy silage, corn silage, barley, corn, corn gluten meal, and soybean meal. Treatments were 1) no supplemental amino acids, 2) 21 g/d of intestinally available Lys, and 3) 22 g/d of intestinally available Lys and 6 g/d of intestinally available Met. Post-experimental calculations suggested that, in contrast to the objective, the unsupplemented ration was colimiting in intestinally available His (0.96 of requirement), followed by Lys (1.00), digestible ruminally undegraded protein (1.01), Ile (1.03), Arg (1.04), Val (1.10), and Met (1.14). In this context, the virtually identical performance of cows fed the unsupplemented ration and cows fed the ration supplemented with ruminally protected Lys demonstrated that dairy cows did not respond to enhanced intestinal supplies of Lys when Lys was not calculated to be the first-limiting nutrient. In contrast, for cows fed rations supplemented with both ruminally protected Lys and ruminally protected Met, the production of both milk protein (40 g/d) and fat (40 g/d) was numerically increased to an extent that was consistent with earlier reported studies, although calculations did not indicate that performance was limited by intestinal supplies of Lys or Met. This result, which may be disputed because of a lack of statistical significance, suggests that Met, apparently unlike Lys, may enhance the production of milk components beyond an enhancement expected because of its role as a limiting amino acid.

Evaluation of functional nerve recovery after reconstruction with a new biodegradable poly (DL-lactide-epsilon-caprolactone) nerve guide.

The aim of this study was to evaluate functional nerve recovery following reconstruction of a 1 cm gap in the sciatic nerve of a rat, using a new biodegradable p (DLLA-epsilon-CL) nerve guide. To evaluate both motor and sensory nerve recovery, walking track analysis and electrostimulation tests were carried out after implantation periods, ranging from 3 to 15 weeks post-operatively. The first signs of functional nerve recovery were observed after 3 weeks. After 15 weeks, 70% of the motor- and 90% of the sensory nerve function was re-established. Return of nerve function was better, in comparison with results from other studies. This study demonstrated successful functional nerve recovery after the reconstruction of a 1 cm nerve gap with a biodegradable p(DLLA-epsilon-CL) nerve guide.

Digestion and passage kinetics of forage fiber in dairy cows as affected by fiber-free concentrate in the diet.

Four ruminally and duodenally cannulated Holstein cows in early lactation were fed alfalfa [47% neutral detergent fiber (NDF)] or timothy silage (49% NDF) for ad libitum intake in a 4 x 4 Latin square experiment. Forages were supplemented with 8 or 12 kg/d of an essentially fiber-free concentrate to study digestion and passage kinetics of forage fiber in high producing dairy cows. Fractional digestion and passage rates of NDF in the rumen were derived from ruminal pool sizes. Alfalfa had a potentially digestible NDF fraction with a faster rate of digestion but a larger indigestible NDF fraction and, consequently, higher physical fill in the rumen than did timothy. However, dry matter intake did not differ between forages, primarily because of the higher fractional passage rates of alfalfa NDF. Although dry matter intake was 23.2 kg/d, fractional passage rates of forage NDF were generally lower than those usually assumed. Fractional rates of NDF digestion decreased equally for both forages as concentrate in the diet increased, but diets with alfalfa forage had the smallest quantitative reduction because of the markedly smaller ruminal pool size of potentially digestible NDF. The fractional passage rate of NDF decreased as concentrate in the diet increased for diets containing alfalfa but did not change for diets containing timothy. Consequently, as concentrate in the diet increased, digestibilities of NDF in the rumen and whole tract increased with alfalfa and decreased with timothy. Results suggest that fiber-free concentrate is useful when digestion and passage kinetics of specific forage fibers are being measured in high producing dairy cows.

Influence of time of feeding a protein meal on ruminal fermentation and forestomach digestion in dairy cows.

Four ruminally and duodenally cannulated dairy cows in midlactation were fed twice daily a mixed diet of alfalfa silage and whole-crop oat silage and a concentrate consisting of primarily barley grain. A high protein supplement was fed at approximately 15% of the estimated dry matter intake of the mixed diet once daily at 0830 h, 0.5 h after the morning meal (day), or at 0030 h, 7.5 h after the evening meal (night). Cows fed the protein supplement during the night had higher apparent forestomach digestion of organic matter and crude protein. Ruminal concentrations of all volatile fatty acids, except isobutyrate, were higher for cows fed the protein supplement during the night. Although ruminal pH and concentrations of ammonia N did not differ between treatments, time by treatment interactions indicated that the feeding times of the protein supplement influenced diurnal patterns of ruminal fermentation. The flow of nonbacterial nonammonia N at the duodenum, as a proportion of N intake, was lower for cows fed the protein supplement during the night, but production of milk fat was higher. Results were consistent with a mechanism whereby protein fed during the night stimulated ruminal fermentation, particularly during the night, resulting in greater forestomach digestion of organic matter and less escape of dietary protein from the forestomach. Clearly, the different feeding times of this protein supplement changed the nutritional value of the overall diet.

Effect of yeast culture (Saccharomyces cerevisiae) on adaptation of cows to diets postpartum.

For approximately 14 d prepartum and exactly 14 d postpartum, 20 multiparous Holstein cows were fed different basal diets that were supplemented, or not supplemented, with a yeast culture preparation. Cows supplemented with yeast culture lost less body condition prepartum, which was consistent with numerically higher body weight gain. No treatment differences were found in prepartum or postpartum dry matter intakes (DMI) or components of DMI. In addition, the extent of the depression in DMI prepartum and the rate of increase in DMI postpartum were not influenced by yeast culture supplementation. Milk and milk component yields were not influenced by yeast culture supplementation. Cows in both groups had higher calculated net energy for lactation for the diets postpartum than would have been expected based on values of the National Research Council for feedstuffs. The increased net energy for lactation seemed to be related to higher than expected metabolic efficiency during early lactation. Results of both the prepartum and postpartum periods were consistent with the hypothesis that supplementation of yeast culture in the diet increased net digestion in the forestomach, particularly of fiber, leading to increased energy output. However, there was no evidence to suggest that supplementation of yeast culture prepartum alleviated the reduction in DMI prepartum or improved the rate of increase in DMI postpartum.

Evaluation of functional nerve recovery after reconstruction with a poly (DL-lactide-epsilon-caprolactone) nerve guide, filled with modified denatured muscle tissue.

The aim of this study was to compare the speed of functional nerve recovery after reconstruction with a biodegradable p(DLLA-epsilon-CL) nerve guide, as filled with either modified denatured muscle tissue (MDMT) or phosphate-buffered saline (PBS). To evaluate both motor and sensory nerve recovery, walking-track analysis and electrostimulation tests were carried out after implantation periods, ranging from 3-15 weeks. Functional nerve recovery after reconstruction of a 15-mm nerve gap, with a biodegradable p(DLLA-epsilon-CL) nerve guide filled with modified denatured muscle tissue, was slightly faster, compared with nerve reconstruction of a 10-mm gap with a biodegradable p(DLLA-epsilon-CL) nerve guide filled with PBS. We conclude that our experiments have demonstrated that the use of MDMT increases the speed of recovery after reconstruction of a nerve gap with a p(DLLA-epsilon-CL) biodegradable nerve guide. Furthermore, the use of MDMT might open perspectives for repair of longer nerve gaps.