Exercise during early, but not late abstinence, attenuates subsequent relapse vulnerability in a rat model.

Exercise has shown promise as a nonpharmacological intervention for addiction, with evidence suggesting a potential utility for relapse prevention. In humans, exercise as an intervention is typically introduced well after the initiation of abstinence, yet neurobiological data from preclinical studies suggest that it may be more effective if initiated during early abstinence. Here, using rat models, we determined whether the beneficial effects of exercise on relapse vulnerability depends on when exercise is first initiated, during early versus late abstinence. Once rats (n=47) acquired cocaine self-administration, they were given 24-h access to cocaine (1.5 mg/kg per infusion) under a discrete trial procedure (four infusions per hour) for 10 days. The rats then began a 14-day abstinence period in which they had access (2 h per day) to a locked wheel throughout abstinence (sedentary) or an unlocked wheel during early (days 1-7), late (days 8-14) or throughout (days 1-14) abstinence (n=10-14 per group). Cocaine seeking, as assessed under an extinction/cued-induced reinstatement procedure, was examined on day 15 of abstinence. Exercise beginning during early abstinence robustly attenuated subsequent cocaine seeking, and this effect persisted even when exercise ended on the seventh day of abstinence. In contrast, exercise during late abstinence was not effective and these animals displayed high levels of cocaine seeking similar to those observed in sedentary animals. These results indicate that the timing of exercise availability differentially impacts cocaine seeking with results suggesting that exercise during early, but not late, abstinence may provide long-term protection against cocaine relapse.

Periparturient responses of multiparous Holstein cows fed different dietary phosphorus concentrations prepartum.

Our objective was to compare the effects of different prepartum dietary phosphorus concentrations on periparturient metabolism and performance. Forty-two late pregnant multiparous Holstein cows were fed 0.21, 0.31, or 0.44% P (dry basis) for 4 wk before expected calving. After parturition, all cows were fed a common lactation diet (0.40% P). In the prepartum period, cows fed 0.21% P had lower blood serum P concentrations compared with cows fed 0.31 or 0.44% P. However, serum P concentrations of all cows were within the normal range (4 to 8 mg/dL) until the day of calving when average concentrations dropped below 4 mg/dL. From 3 to 14 d postpartum, serum P of cows fed 0.21% P was greater than that of cows fed 0.31 or 0.44% P. No cows presented with or were treated for clinical hypophosphatemia in the periparturient period. Total serum Ca was lower before calving through 2 d postpartum for cows fed 0.44% P compared with those fed 0.21 or 0.31%. Prepartum dietary P treatments did not alter blood osteocalcin, hydroxyproline, and deoxypyridinoline, indicators of bone metabolism, or concentrations of parathyroid hormone or 1,25-dihydroxyvitamin D3. Energy-corrected milk yield and milk composition (first 28 d of lactation) were not affected by prepartum dietary P concentrations. It is concluded that feeding 0.21% P (34 g of P/cow daily) prepartum is adequate for periparturient multiparous Holstein cows with high metabolic demands and genetic potential for milk production. No adverse effects on periparturient health, dry matter intake, or 28-d lactation performance resulted.

Comparison of analytical methods and the influence of milk components on milk urea nitrogen recovery.

The objectives of this study were to compare analytical instruments used in independent laboratories to measure milk urea nitrogen (MUN) and determine whether any components in milk affect the recovery of MUN. Milk samples were collected from 100 Holstein cows fed one ration in a commercial dairy herd with a rolling herd average of 9500 kg. Half of each sample was spiked with 4 mg/dL of urea N, while the other half was not, to determine recovery. Both milk samples (spiked and not spiked) were sent to 14 independent laboratories involved in the MUN Quality Control Program through National Dairy Herd Improvement Association and analyzed for MUN, fat, protein, lactose, somatic cell count (SCC), and total solids. The laboratories analyzed MUN using CL-10 (n = 3), Skalar (n = 2), Bentley (n = 3), Foss 4000 (n = 3) or Foss 6000 (n = 3) systems. When recovery of MUN was evaluated among the 5 analytical methods, the mean recoveries for the Bentley, Foss 6000, and Skalar systems were 92.1 (SE = 2.76%), 95.4 (SE = 10.1%), and 95.1% (SE = 7.61%), respectively, and did not differ from each other. However, MUN recovery was 85.0% (SE = 2.8%) for the CL-10 system and 47.1% (SE = 9.9%) for the Foss 4000 system, both of which differed from the other 3 systems. Recoveries from Foss 4000, Foss 6000, and Skalar varied among laboratories using the same instrument. As initial MUN concentration increased, recovery decreased using the Bentley and CL-10 systems. Increasing milk fat resulted in a decrease in recovery using the Foss 6000 system. For 4 of the 5 methods, recovery of MUN was not associated with specific milk components. Recovery of MUN was inconsistent for laboratories using the Foss 4000 and the Foss 6000 method and using these systems may result in an overestimation or underestimation of MUN.

Phosphorus feeding levels and critical control points on dairy farms.

A viable and cost-effective approach to managing P on dairy farms is to minimize excess P in diets, which in turn leads to less excretion of P in manure without impairing animal performance. A questionnaire survey was conducted, coupled with on-site feed and fecal sample collection and analysis on dairy farms in New York, Pennsylvania, Delaware, Maryland, and Virginia. The purpose was to assess dietary P levels and to identify critical control points pertaining to P feeding management. Survey responses, 612 out of 2500 randomly selected farms, revealed a wide range of dietary P concentrations for lactating cows, from 3.6 to 7.0 g/kg of feed DM. The mean was 4.4 g/kg, which was 34% above the level recommended by the NRC for 27.9 kg milk/d, the mean milk yield in the survey. Higher P concentrations in diets were not associated with higher milk yields (n = 98, R2 = 0.057 for the survey farms; n = 92, R2 = 0.043 for farms selected for on-site sampling). However, higher dietary P led to higher P excretion in feces (n = 75, R2 = 0.429), with much of the increased fecal P being water soluble. Phosphorus concentrations in diet samples matched closely with P concentrations in formulated rations, with 67% of the feed samples deviating <10% from the formulations. On 84% of the survey farms, ration formulation was provided by professionals rather than producers themselves. Most producers were feeding more P than cows needed because it was recommended in the rations by these consultants. In conclusion, P fed to lactating cows averaged 34% above NRC recommendations; to reduce excess dietary P, ration formulation is the critical control point.