Angus-cross cows (n = 13; 8 pregnant, BW 610 ± 24 kg, and 5 nonpregnant, BW 571 ± 23 kg) and heifers (n = 13; 8 pregnant, BW 511 ± 40 kg, and 5 nonpregnant, BW 451 ± 60 kg) were individually fed chopped warm-season grass hay (5.5% CP, 67% NDF) for ad libitum intake and soybean meal (46% CP) at 450 g/d. Intake was measured daily, and DM digestibility, digesta passage rate, and plasma glucose and β-hydroxybutyrate (BHBA) concentrations were measured every 14 d from 49 d prepartum to 49 d postpartum. Prepartum DMI (% of BW) increased over time for pregnant heifers through 2 wk prepartum before declining but did not change over time for pregnant cows. Dry matter digestibility decreased with advancing gestation (P < 0.001); pregnant animals had greater digestibility than nonpregnant cows and heifers (P = 0.02). Digestibility was not influenced by age (P = 0.99). Pregnant cows and heifers had faster digesta passage rates than their nonpregnant counterparts (P = 0.02). Pregnant animals had lower plasma glucose (P < 0.001). Plasma BHBA concentrations were greater in pregnant animals than in nonpregnant animals (P < 0.001) but were not influenced by age (P = 0.27) or time prepartum (P = 0.98). Postpartum DMI (% of BW) was greater for lactating heifers than other groups (age × lactation status; P = 0.05) and increased over time (P < 0.001). Diet digestibility increased with time postpartum (P < 0.001), and heifers had greater digestibility than cows from 3 to 7 wk postpartum but not at 1 wk postpartum (age × time; P = 0.02). Postpartum passage rate was not influenced by age or lactation status (P > 0.23). Lactating animals had lower plasma glucose and greater plasma BHBA concentrations postpartum than nonlactating animals (P < 0.001). Calves from mature cows grew faster than calves from heifers (age × time; P < 0.001). These data show that although primiparous beef heifers have similar DM digestibility, passage rates, and plasma glucose and BHBA concentrations, intake patterns differ between heifers and cows. Although DMI (% of BW) and digestibility did not differ between pregnant beef heifers and pregnant mature cows, the DMI (% of BW) was greater for lactating primiparous cows (heifers) than for lactating multiparous cows. Even with their postpartum increase in DMI, primiparous beef heifers were not able to consume adequate amounts of the warm-season forage to support their requirements for maintenance, growth, and lactation.

The effects of mineral-supplement delivery system on patterns of supplement use by grazing beef cows were measured in 2 studies. Study 1 was conducted on 4 pastures grazed by pregnant, mature beef cows (BW = 562 ± 38 kg) from February to May. Study 2 was conducted on 4 pastures grazed by lactating beef cows (BW = 579 ± 54 kg) and their calves from May to September. Treatments were mineral delivered in salt-based, granular form (salty) or mineral provided in a low-protein, cooked, molasses-based block (sweet); both were fed ad libitum. The salty supplement was supplied to cattle via a covered mineral feeder; the sweet supplement was supplied via an open-topped barrel. Both salty and sweet supplements were deployed in each pasture. No additional salt was supplied to cattle. Forage use in the vicinity of each supplement-deployment site and the frequency and duration of herd visits to each supplement-deployment site were measured during four 14-d periods during study 1 and seven 14-d periods during study 2. Supplements were moved to new locations within pastures at the beginning of each period. Consumption of the sweet supplement was greater than salty during each data-collection period in study 1; however, relative differences in consumption diminished over time (treatment × time, P = 0.03). In study 2, sweet consumption was greater than salty in periods 1, 6, and 7 but was not different from salty during periods 2, 3, 4, and 5 (treatment × time, P < 0.01). Increased consumption of the sweet supplement in study 1 translated to greater frequency of herd visits to supplement-deployment sites compared with the salty sites (2.82 vs. 2.47 herd visits/d; P = 0.02) and longer herd visits to supplement-deployment sites compared with the salty sites (125.7 vs. 54.9 min/herd visit; P < 0.01). The frequency of herd visits to mineral feeding sites in study 2 was similar (P > 0.10) between treatments for periods 1 through 6; however, herds visited the sweet sites more often than salty during period 7 (P < 0.01). Herd visits to the sweet sites were longer than those to the salty sites in study 2 (83.8 vs. 51.4 min/herd visit; P < 0.01). Forage disappearance within 100 m of supplement-deployment sites was not influenced (P ≥ 0.54) by treatment in either study. Results were interpreted to suggest that the sweet supplement influenced the location of grazing cattle more strongly than the salty supplement and may be more effective for luring cattle into specific areas of pasture during the winter, spring, and early fall but not during summer.

High-performance liquid chromatography and liquid chromatography-mass spectrometry were suitable methods for determination of plasma caffeine concentrations in alpacas and llamas. Plasma caffeine concentration-time curves were best described by a 2-compartment model. Elimination half-lives, plasma clearance, volume of distribution at steady state, and mean residence time were not significantly different between alpacas and llamas. Intravenous administration of caffeine at a dose of 3 mg/kg did not induce clinical signs of excitement.

The objective of this study was to determine plasma pharmacokinetics and bioavailability of fenbendazole (FBZ) and oxfendazole (OFZ) after intravenous (iv) and oral administrations of FBZ (5 mg/kg) to alpacas. Plasma concentrations of FBZ and OFZ after administration of FBZ iv and orally (5 mg/kg) were determined by high-performance liquid chromatography with ultraviolet detection. Total clearance (CL) of FBZ was 16.5±4 mL/kg/min (range: 4–31 mL/kg/min), and steady-state volume of distribution (Vdss) was 3.3±1 L/kg (range: 1.7–7.4 L/kg). The terminal phase half-life of FBZ after iv administration was 5.9±3.8 hours (range: 0.8–20 hours). After oral administration, the FBZ terminal phase half-life was 23±5 hours (range: 9–37 hours) and the systemic bioavailability of FBZ was 16%±6% (range: 1%–41%). Peak FBZ concentrations after oral administration were 0.13±0.05 µg/mL (range: 0.05–0.28 µg/mL) at 10 hours (range: 8–12 hours). Peak plasma OFZ concentrations after oral dosing with FBZ (5 mg/kg) were 0.14±0.05 µg/mL (0.05–0.3 µg/mL) at 24±7 hours (range: 12–48 hours). FBZ clearance is lower in comparison to that of other species. Systemic availability of FBZ after oral administration is low after oral dosing. Metabolites of FBZ produced by alpacas are similar to those observed in other species.

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