The objective of this study was to evaluate colostrum IgG concentration harvested at first and second milking from multiparous Jersey cows, the dam's lactation number, colostrum yield, and time of first milking. In addition, we validated the use of a Brix refractometer to estimate IgG concentration in colostrum from multiparous Jersey cows using radial immunodiffusion as the reference method. Colostrum samples and total weight of colostrum harvested at first (n = 134) and second (n = 68) milking were collected from 134 multiparous Jersey cows housed in a California herd. Fresh colostrum samples were analyzed for IgG concentration with Brix refractometry and frozen samples by radial immunodiffusion. A total of 90.4 and 42.7% of the samples from first and second milking met industry standards of quality for IgG concentration (>50 g/L). Second and third lactation cows had similar colostrum IgG concentration but lower than cows on their fourth and greater lactation. At second milking, 56.4% of cows on their fourth or greater lactation had colostrum IgG concentrations >50 g/L. When colostrum yield increased from low (<3 kg), medium (3 to 6 kg), to high (>6 kg), IgG concentration decreased. Higher IgG concentration was observed on colostrum harvested at <6 h (short) versus 6 to 11 h (medium) after calving. However, IgG concentration in colostrum harvested after 11 h (long) was similar to that harvested at short and medium time. Readings of %Brix were highly correlated with IgG at first (r = 0.81) and second (r = 0.77) milking. The best Brix threshold to identify colostrum from first milking with >50 IgG g/L was 20.9% based on logit equations with Youden's index criterion and 18.0% based on accuracy criterion. For colostrum harvested at second milking, similar Brix thresholds were obtained, 19.2 and 19.0%, regardless of whether Youden's index or accuracy was used as the selection criterion. Our results indicate that the dam's lactation number, colostrum yield, and time of first milking relative to calving are associated with IgG concentration in colostrum from multiparous Jersey cows. Second milking colostrum from mature Jersey cows should be evaluated to extend colostrum supply on dairies especially during times of shortage. Readings of %Brix can be used to rapidly estimate IgG concentration in Jersey colostrum harvested at first and second milking.

A degree of negative energy balance is commonly experienced by cows during early lactation. This physiological state, if pronounced or prolonged, leads to partial oxidation of nonesterified fatty acids as an energy source and, consequently, increasing blood β-hydroxybutyrate (BHB) concentrations and potentially development of ketosis in postpartal dairy cows. Twenty-four multiparous Holstein cows received a common prepartal and postpartal diet. Cows were fitted with an accelerometer mounted laterally on the distal left hind leg using vet wrap from -30 to 15 d relative to parturition. A retrospective analysis was performed using the postpartal BHB data at 8 time points from 0 to 15 d in milk measured with the Precision Xtra (Abbott Diabetes Care, Alameda, CA). Cows with an average blood BHB <1.4 mmol/L were designated nonketotic (NONKET; n = 12), and those with ≥1.4 mmol/L were designated ketotic (KET; n = 12). A total of 8 samples per cow were used for this analysis. Subsequent analyses of behavioral patterns and blood biomarkers were performed using this group effect. On average, blood BHB reached subclinical levels (1.4 ± 0.3 mmol/L; mean ± standard error of the mean) at 3 d postpartum for all cows in this study. Behavioral patterns were obtained from accelerometer data, and correlation analysis was performed between these behaviors such as standing and lying time from -30 to 3 d relative to parturition and blood BHB concentration at 3 d postpartum. The strongest correlation was obtained between standing time at 3 d before calving and blood BHB at 3 d postpartum. Dry matter intake was greater (ca. 3 kg/d) in NONKET cows than in KET cows. An interaction of group × time for milk yield resulted in an overall increase of 5.7 kg/d in NONKET cows in comparison with KET. The blood concentrations of biomarkers for liver function (γ-glutamyltransferase and glutamic-oxaloacetic transaminase), inflammation (IL-6), and metabolism (nonesterified fatty acids) were increased at various time points in KET cows in comparison with NONKET during the transition period. Overall, lower bilirubin in NONKET cows than in KET further confirmed an impaired liver function in the latter group of cows. Our findings revealed the potential for establishing correlations between prepartal behavioral patterns derived from accelerometer data and postpartal subclinical ketosis, and further confirming the latter by physiological alterations in biomarkers related to inflammation and liver function. Our data also indicate that cows with a predisposition to postpartal subclinical or clinical ketosis will remain standing for fewer hours during the days leading to parturition, which decreased DMI, and this condition was further reflected in lower milk yield.

Objectives were to evaluate effects of supplemental zinc hydroxychloride (HYD; Micronutrients, Indianapolis, IN) on gut permeability, metabolism, and inflammation during feed restriction (FR). Holstein cows (n = 24; 159 ± 8 d in milk; parity 3 ± 0.2) were enrolled in a 2 × 2 factorial design and randomly assigned to 1 of 4 treatments: (1) ad libitum fed (AL) and control diet (ALCON; 75 mg/kg Zn from zinc sulfate; n = 6);(2) ad libitum fed and HYD diet (ALHYD; 75 mg/ kg Zn from HYD; n = 6); (3) 40% of ad libitum feed intake and control diet (FRCON; n = 6); or (4) 40% of ad libitum feed intake and HYD diet (FRHYD; n = 6). Prior to study initiation, cows were fed their respective diets for 21 d. The trial consisted of 2 experimental periods (P) during which cows continued to receive their respective dietary treatments. Period 1 (5 d) served as the baseline for P2 (5 d), during which cows were fed ad libitum or restricted to 40% of P1 feed intake. In vivo total-tract permeability was evaluated on d 4 of P1 and on d 2 and 5 of P2, using the paracellular permeability marker chromium (Cr)-EDTA. All cows were euthanized at the end of P2 to assess intestinal architecture. As anticipated, FR cows lost body weight (~46 kg), entered into calculated negative energy balance (−13.86 Mcal/d), and had decreased milk yield. Circulating glucose, insulin, and glucagon decreased, and nonesterified fatty acids and β-hydroxybutyrate increased in FR relative to AL cows. Relative to AL cows, FR increased lipopolysaccharide-binding protein, serum amyloid A (SAA), and haptoglobin (Hp) concentrations (2-, 4-, and 17-fold, respectively); and peak SAA and Hp concentrations were observed on d 5. Circulating SAA and Hp from FRHYD tended to be decreased (47 and 61%, respectively) on d 5 relative to FRCON. Plasma Cr area under the curve increased (32%) in FR treatments on d 2 and tended to be increased (17%) on d 5 of P2 relative to AL treatments. No effects of diet were observed on Cr appearance. Relative to AL cows, FR increased jejunum villus width and decreased jejunum crypt depth and ileum villus height and crypt depth. Relative to FRCON, ileum villus height tended to increase in FRHYD cows. Feed restriction tended to decrease jejunum and ileum mucosal surface area, but the decrease in the ileum was ameliorated by dietary HYD. In summary, FR induced gut hyperpermeability to Cr-EDTA, and feeding HYD appeared to benefit some key metrics of barrier integrity.

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