Fifty-two multiparous Holstein cows were randomly assigned to receive 0 or 20 mg of biotin/d starting at an average of 16 d prepartum and then switched to 0 or 30 mg of biotin/d from calving through 70 d postpartum to determine whether supplemental biotin would affect cow performance, hepatic lipidosis, and plasma metabolites. Mean concentration of biotin in plasma sampled weekly was greater in cows fed biotin (4.3 vs. 9.4 nmol/L). Postpartum dry matter intake as a percentage of body weight (3.9% vs. 4.0%), milk production (35.8 vs. 34.8 kg/d), and milk fat concentrations (3.59% vs. 3.69%) were similar between treatment groups. Milk from biotin-supplemented cows tended to have a greater concentration of protein (2.73% vs. 2.83%). Concentrations of plasma nonesterified fatty acids were lower at wk 2 (652 vs. 413 microEq/mL) and 4 (381 vs. 196 microEq/mL) postpartum in cows fed supplemental biotin. However, mean plasma concentrations of beta-hydroxybutyric acid were not affected by biotin supplementation. Mean concentration of plasma glucose was greater for lactating cows fed supplemental biotin (63.4 vs. 66.6 mg/dL). Biopsies of liver were taken at 2, 16, and 30 d postpartum. The triacylglycerol concentration in liver (wet basis) tended to decrease at a faster rate after d 2 postpartum with biotin supplementation compared with control cows. The potential mechanisms that link improved glucose status and decreased lipid mobilization in cows supplemented with biotin warrant further investigation.

Rosendo O., L. R. McDowell: Liver Dry Matter and Liver Lipids in Periparturient DairyCows. Acta Vet. Brno 2003, 72: 541-546. One hundred and fifty liver samples were collected from forty multiparous Holstein cows at an average of 16 d prepartum to 30 d postpartum. The objectives of this study were to determine the statistical relationship between liver percentages of dry matter (LDM) and total lipids (TL) and triacylglycerols (TAG) on a wet basis and to develop predictive equations of TL and TAG from LDM that could be used for the diagnosis of fatty liver in transition cows. Estimates of LDM changed slightly with time to calving. The best-fitting models to describe the inverse relationship between LDM and liver lipids using the entire data set (LDM: 20.0 to 36.2%, TL: 2.9 to 14.9%; TAG: 0.7 to 10.4%) were the following second-order polynomial derived equations. For TL = 44.268 -(3.3625 x LDM) + (0.0717 x LDM 2 ) (R 2 = 0.53%; P < 0.0001) and for TAG = 39.983 -(3.2370 x LDM) + (0.0678 x LDM 2 ) (R 2 = 0.58%; P < 0.0001). The precision of equation for TAG (R 2 = 0.61) slightly improved with a third-order polynomial equation after reducing data to LDM greater than 25% because of less variability in liver TAG with higher LDM. Time to calving did not influence the relationship between LDM and liver lipids. For practical applications, these predictive equations could be used as an approximation of a mild to moderate (up to 10% TAG, wet weight) fatty liver in multiparous periparturient dairy cows when the chemical analysis to quantify liver lipids is not affordable.

In in vitro true dry matter degradability (IVTDMD), in situ dry matter degradability, and neutral detergent fiber degradability, both in vitro (IVNDFD) and in situ (ISNDFD) techniques were used with crossbred goats to determine dry matter and neutral detergent fiber (NDF) ruminal degradability in eight forages and four industrial byproducts. Total digestible nutrients (TDN) content obtained with five different summative models (summative equations) were studied to compare the precision of estimates. All these models included digestible fractions of crude protein, ether extract, and nonfiber carbohydrates that were calculated from chemical composition, but digestible NDF (dNDF) was obtained from IVNDFD (IVdNDF), ISNDFD (ISdNDF), or by using the Surface Law approach. On the basis of the coefficient of determination (R 2) of the simple lineal regression of predicted TDN (y-axes) and observed IVTDMD (x-axes), the precision of models was tested. The predicted TDN by the National Research Council model exclusively based on chemical composition only explains up to 41% of observed IVTDMD values, whereas the model based on IVdNDF had a high precision (96%) to predict TDN from forage and byproducts fiber when used in goats.

The present on-farm research evaluated the occurrence of fatty liver syndrome and its predisposing risk factors for multiparous dairy cows from a commercial herd in Venezuela. Liver biopsy samples were collected at 35 days (d) prepartum (Holstein, n = 14; Holstein × Carora crossbred, n = 17) as well as 1 to 7 d (Holstein, n = 8; Holstein × Carora crossbred, n = 11) and 28 to 35 d (Holstein, n = 6; Holstein × Carora crossbred, n = 14) postpartum in order to analyse hepatic triacylglycerols (TAG, % wet basis) and glycogen concentrations. At postpartum, an occurrence of 72.0% for severe fatty liver along with 73.5% of subclinical ketosis (SCK) was found. The multiple regression model that best explained the association between milk production in the previous lactation (MYP) and TAG at first week postpartum was as follows: TAG, % = −11.2 + 3.16 (prepartum body condition) + 0.0009176 (MYP) (R² = 0.36, P < 0.05). Logistic regression indicated that Holstein × Carora crossbred cows tended to have 27% higher relative risk than Holstein to experience SCK, whereas prepartum liver TAG greater than 3% tended to be associated with a higher relative risk for SCK compared to cows with TAG ≤3%.

The aim of this study was to assess the relationships of hepatic triacylglycerol (TAG), plasma glucose, plasma cholesterol, and plasma urea nitrogen (PUN) concentrations with the morphological quality of oocytes obtained from 20 Carora breed lactating cows at days 20 and 35 postpartum in a commercial farm. Oocytes were obtained through the technique of transvaginal ultrasound-guided follicle aspiration. Change in body condition score (0.35 vs. 0.44, P = 0.02) and mean plasma cholesterol (3.59 vs. 4.35 mmol/L, P = 0.01) significantly differed between the 2 periods, whereas mean TAG tended to be higher at day 35 after calving (2.29 vs. 2.54%, fresh basis, P = 0.06) and indicated moderately fatty liver. At day 35 postpartum, both plasma cholesterol and TAG tended to have a positive correlation with oocyte quality (%), at r = 0.44 (P = 0.08) and 0.40 (P = 0.05), respectively, but no associations between glucose or PUN and oocyte recovery traits were found at any time. The percentage of oocytes with high quality was found higher (86.7 vs. 52%, P = 0.04) in those cows with more than 4 oocytes recovered. In conclusion, there was a positive relationship among hepatic TAG, plasma cholesterol, and quality of oocytes in Carora breed lactating cows.

The objective of this study was to test the hypothesis that serum biotin concentration and biotin balance (consumed - [urinary output + fecal output]) measured as total avidin-binding substances (biotin + biotin metabolites) are responsive to changes in the proportions of dietary alfalfa meal and concentrate fed to sheep. Eight sheep (initial BW = 40 kg) consumed a pelleted alfalfa meal-based diet that had 95:5, 48:52, 23:77, or 9:91% alfalfa meal:concentrate ratios (DM basis) in a replicated 4 x 4 Latin square design with 20-d periods (10 d of acclimation, 7 d of adaptation, and a 3-d collection period with jugular blood drawn on the last day). Replacing alfalfa meal with concentrate in the pelleted diets decreased dietary concentrations of biotin proportionally. As the percentage of alfalfa meal in the diet decreased, there was a linear decrease in daily DM intake (1,128 to 901 g of DMI/d; P < 0.01), with a linear (P < 0.01) and quadratic (P < 0.01) increase in the apparent total-tract DM digestibility of diets (51.0 to 80.0%). The biotin consumed decreased with alfalfa meal proportion in the diet (linear, P < 0.01). Both fecal biotin concentration (linear, P < 0.01) and fecal biotin output (quadratic, P < 0.05) increased, reaching peaks at 23% alfalfa meal. Fecal biotin output was not correlated with biotin intake, DMI, or intake of digestible DM. Mean urinary output, urinary biotin concentration, urinary biotin output, and serum biotin concentration were not affected by treatments. Means of biotin balance were negative and revealed the same trends among treatments as did fecal output. Biotin balance was a quadratic (P < 0.05) function of decreasing alfalfa meal in the diet, with more negative values at the alfalfa meal:concentrate ratio of 23:77. Results suggest that the greatest synthesis of biotin in the total digestive tract occurs with diets of either 52 or 77% concentrate for sheep; however, research addressing the significance of biotin metabolites on biotin balance and plasma biotin pool is needed.

The objective of this study was to test the hypothesis that serum biotin concentration and biotin balance (consumed - [urinary output + fecal output]) measured as total avidin-binding substances (biotin + biotin metabolites) are responsive to changes in the proportions of dietary alfalfa meal and concentrate fed to sheep. Eight sheep (initial BW = 40 kg) consumed a pelleted alfalfa meal-based diet that had 95:5, 48:52, 23:77, or 9:91% alfalfa meal:concentrate ratios (DM basis) in a replicated 4 x 4 Latin square design with 20-d periods (10 d of acclimation, 7 d of adaptation, and a 3-d collection period with jugular blood drawn on the last day). Replacing alfalfa meal with concentrate in the pelleted diets decreased dietary concentrations of biotin proportionally. As the percentage of alfalfa meal in the diet decreased, there was a linear decrease in daily DM intake (1,128 to 901 g of DMI/d; P < 0.01), with a linear (P < 0.01) and quadratic (P < 0.01) increase in the apparent total-tract DM digestibility of diets (51.0 to 80.0%). The biotin consumed decreased with alfalfa meal proportion in the diet (linear, P < 0.01). Both fecal biotin concentration (linear, P < 0.01) and fecal biotin output (quadratic, P < 0.05) increased, reaching peaks at 23% alfalfa meal. Fecal biotin output was not correlated with biotin intake, DMI, or intake of digestible DM. Mean urinary output, urinary biotin concentration, urinary biotin output, and serum biotin concentration were not affected by treatments. Means of biotin balance were negative and revealed the same trends among treatments as did fecal output. Biotin balance was a quadratic (P < 0.05) function of decreasing alfalfa meal in the diet, with more negative values at the alfalfa meal:concentrate ratio of 23:77. Results suggest that the greatest synthesis of biotin in the total digestive tract occurs with diets of either 52 or 77% concentrate for sheep; however, research addressing the significance of biotin metabolites on biotin balance and plasma biotin pool is needed.