Forty Holstein dairy calves were blocked by birth date and sex, and randomly assigned to 1 of 4 treatments within each block to elucidate the effect of feeding regimen and sodium bicarbonate (NaHCO₃) supplementation on absorption of IgG from colostrum replacer (CR). Calves received CR containing 191.4 g of IgG fed either in 1 feeding at 0 h (within 45 min of birth), with or without 30 g of NaHCO₃, or in 2 feedings (127.6 g of IgG at 0 h, with or without 20 g of NaHCO₃, and 63.8 g of IgG at 6 h, with or without 10 g of NaHCO₃). The treatments were (1) 1 feeding of CR+0 g of NaHCO₃; (2) 1 feeding of CR+30 g of NaHCO₃; (3) 2 feedings of CR+0 g of NaHCO₃; and (4) 2 feedings of CR+30 g total of NaHCO₃. Only calves born with no dystocia were used on this study. Blood samples were taken at 0, 6, 12, 18, and 24h postpartum and were analyzed for IgG using a radial immunoassay. Results indicated that, individually, feeding regimen and NaHCO₃ treatments had no effect. However, the interaction was significant for 24-h IgG and area under the curve, and showed a trend for apparent efficiency of absorption. Absorption rate data indicated that, for calves fed within 45 min of birth, most IgG absorption occurred in the first 6 h after birth. From 6 to 12 h postpartum, IgG absorption started to decrease; however, IgG absorption remained higher for calves fed in a single feeding than in 2 feedings. These data indicated that NaHCO₃ may increase IgG absorption when calves are fed colostrum in a single feeding but is not beneficial when colostrum is fed in 2 feedings.

Eighty Holstein and Holstein cross dairy calves were blocked by birth date and randomly assigned to 1 of 8 treatments within each block to examine the effect of a colostrum replacer (CR) feeding regimen, supplementation of CR with sodium bicarbonate (NaHCO3), and provision of a milk replacer (MR) feeding on IgG absorption. Calves were offered a CR containing 184.5g/L of IgG in either 1 feeding at 0h (within 30 min of birth), with or without 30g of NaHCO3, with or without a feeding of MR at 6h of age, or 2 feedings of CR (123g of IgG at 0h with or without 20g of NaHCO3 and 61.5g of IgG at 6h with or without 10g of NaHCO3), with or without a MR feeding at 12h. Therefore, treatments were (1) 1 feeding of CR; (2) 2 feedings of CR; (3) 1 feeding of CR + 30g of NaHCO3; (4) 2 feedings of CR + 30g of NaHCO3; (5) 1 feeding of CR + MR feeding; (6) 2 feedings of CR + MR feeding; (7) 1 feeding of CR + 30g NaHCO3 + MR feeding; and (8) 2 feedings of CR + 30g NaHCO3 + MR feeding. Blood samples were obtained at 0, 6, 12, 18, and 24h after birth and were analyzed for IgG via radial immunoassay. Results indicated that CR feeding schedule, MR feeding, and the interactions CR × Na, CR × MR, and CR × Na × MR were similar for 24-h serum IgG, apparent efficiency of absorption, or area under the curve. Serum IgG at 24h, apparent efficiency of absorption, and area under the curve were decreased with addition of NaHCO3 compared with calves not supplemented with NaHCO3. These data indicate that supplementation of CR with NaHCO3 is not beneficial to IgG absorption and feeding MR within 6h of CR feeding does not affect IgG absorption.

Whether use of hormone-replacement therapy (HRT) influences menopause-related changes in body weight is unclear. HRT may affect energy balance by influencing synthesis of the adipocyte-derived hormone leptin. The objectives of this study were to: 1) identify factors influencing circulating leptin in postmenopausal women; 2) determine whether HRT influences serum leptin after adjusting for confounding factors; and, 3) identify potential independent effects of HRT or leptin on resting energy expenditure (REE). Subjects were 54 postmenopausal women, 45-55 yr old, 35 of whom used HRT (estrogen plus progestin). Total and regional body composition and fat distribution were determined by dual-energy x-ray absorptiometry and computed tomography; fasting serum leptin and insulin, by RIA; and REE, by indirect calorimetry. Stepwise multiple linear regression analysis indicated that serum leptin could best be predicted from total fat mass, fasting serum insulin, and total lean mass [log leptin = 1.08 x log fat mass) + (0.46 x log insulin) + (-1.25 x log lean mass) + 1.88; model R2 = 0.78, P < 0.001]. Multiple linear regression analysis indicated that visceral fat was independently related to leptin (parameter estimate = 0.23, P < 0.05), after adjusting for s.c. abdominal fat and leg fat, as well as lean mass and insulin. After adjusting for total fat mass, total lean mass, and fasting insulin, serum leptin did not differ between users and nonusers of HRT (21.7 +/- 1.0 vs. 20.2 +/- 1.3 ng/mL, P = 0.369, adjusted mean +/- SE, respectively). Serum estradiol was inversely correlated with (adjusted) leptin in non-HRT users (r = -0.50), suggesting that ovarian senescence may lead to an increase in leptin. Multiple linear regression analysis indicated that REE (adjusted for fat mass, fat-free mass, and ethnicity) was not associated with leptin (P = 0.298) or hormone use status (P = 0.999; 1323 +/- 31 vs. 1316 +/- 42 kcal/day, adjusted mean +/- SE for users and nonusers, respectively). These results indicate that, in postmenopausal women: 1) total fat mass, lean mass, and fasting insulin, but not HRT, are significant determinants of serum leptin; 2) visceral and s.c. fat contribute to serum leptin; and, 3) neither HRT nor leptin is independently related to REE.

Forty Holstein heifers entered the 12-wk study at approximately 12 wk of age. At enrollment, heifers were blocked by birth date and assigned to 1 of 4 treatments: (1) carrier (30 g; control); (2) lasalocid + carrier (1 mg/kg of body weight; L); (3) chlortetracycline + carrier (22 mg/kg of body weight; CTC); (4) L + CTC + carrier (CTCL). Heifers on CTC and CTCL were provided treatment Monday through Friday and carrier only on Saturday and Sunday. These heifers were provided their respective treatment during wk 1 to 4, 6, and 10; wk 5, 7 to 9, and 11 to 12 heifers were provided the nonmedicated carrier. Heifers were individually fed a total mixed ration with treatments top-dressed at 1200 h daily. Dry matter intake was monitored for each heifer and feed provided was adjusted according to individual intakes. Skeletal measurements were taken weekly and blood samples were obtained every Monday, Wednesday, and Friday. Blood samples were analyzed for thyroxine concentration via radial immunoassay. Heifers supplemented with L had lower average daily gain , overall body weight gain, and trends for lower daily body length gain and overall girth gain compared with CTC heifers, but similar to control and CTCL heifers. Heifers fed L had lower hip height gain and overall hip height gain compared with CTCL heifers, but similar to control and CTC heifers. Heifers fed L had lower overall withers height gain compared with control heifers, but similar to CTC and CTCL heifers. No treatment effect on thyroxine concentrations was observed. These data indicate that L did not increase growth. Results from this experiment indicate that supplementing heifers with L was not beneficial and no benefits to supplementing heifers with CTC or the combination of CTC and L were evident compared with control heifers. Heifers in this study experienced minimal health problems and were regarded to be under low stress levels. Supplementing CTC and L may be beneficial to growing heifers under conditions where disease exposure and stressors are greater.

S. 2015. Estimating plasma volume in neonatal Holstein calves fed one or two feedings of a lacteal-based colostrum replacer using Evans blue dye and hematocrit values at various time points. Can. J. Anim. Sci. 95: 293Á298. Twenty-eight Holstein calves were blocked by birth date and randomly assigned to one of two treatments to investigate the effect of colostrum replacer (CR) feeding regimen on plasma volume (PV). Treatments were: (1) one feeding of CR (C 1 ; 3 L of reconstituted CR 675 g of powder providing 184.5 g of IgG at birth) or (2) two feedings of CR (C 2 ; 2 L of reconstituted CR at birth and 1 L of reconstituted CR at 6 h). By 6 h of age, all calves had received 3 L of CR providing 184.5 g of IgG. Plasma volume was estimated at 6, 12, 18, and 24 h after birth using Evans blue dye. No treatment effects were noted at any time points (P!0.05). Mean PV for all calves regardless of treatment at 6, 12, 18, and 24 h were 78.6, 89.2, 83.9, and 90.7 mL kg(1 of body weight, respectively. Plasma volume was correlated with hematocrit (HCT), initial HCT, and treatment. Hematocrit was correlated with PV, initial HCT, and body weight. Hematocrit for 6, 12, 18 and 24 h after birth can be predicted with an initial precolostral HCT determination.