A retrospective study on the effects of dry period length on milk yield and postpartum health in Holstein dairy cows.

We retrospectively analyzed the effects of dry period length (DPL) on milk yield and postpartum health using 152 commercial dairy farm data, including 46,228 dairy cows in Hokkaido, Japan, and examined the optimal DPL. The DPL was divided into eight categories: ≤25, 26-35, 36-45, 46-55, 56-65 (reference), 66-75, 76-85, and ≥86 d. The total milk yields (the sum of milk yield during the 55 d before and the 305 d milk yield after calving) of cows with DPL of ≤55 d did not differ from the reference group. Cows with DPL of ≤55 d had lower odds ratios (OR) of a displaced abomasum (DA), ketosis, milk fever (MF), and abnormal milk fat-to-protein ratio but had higher puerperal fever (PF) and stillbirth ORs than the reference group. Cows with a DPL of 46-55 d had the lowest PF and stillbirth ORs among the short DPL categories. The extremely short (≤25 d) and long (≥86 d) DPL increased the ORs of mastitis and abnormal liner score of somatic cell counts (SCCs) compared with the reference group. We conclude that shortening DPL can reduce postpartum health problems without reducing milk yield and that the optimal DPL is 46-55 d.

Dynamic changes and importance of plasma concentrations of ether phospholipids, of which the majority are plasmalogens, in postpartum Holstein dairy cows.

CONTEXT: Ethanolamine plasmalogens (EPls) and choline plasmalogens (CPls) are classes of ethanolamine ether phospholipids (ePE) and choline ether phospholipids (ePC), respectively. EPls play crucial roles in maternal and breastfed infant bodies and stimulate gonadotropin secretion by gonadotrophs. AIMS: To estimate changes in and importance of plasma concentrations of EPls and CPls, utilising newly developed enzymatic fluorometric assays for ePE and ePC in postpartum Holstein cows. METHODS: Plasma samples were collected from 3weeks before expected parturition until approximately 8weeks after parturition (16 primiparous and 38 multiparous cows) for analysis. KEY RESULTS: Plasma concentrations of ePE and ePC, most of which are plasmalogens, declined before and increased after parturition and stabilised near the day of the first postpartum ovulation (1stOV). From weeks 2 to 3 after parturition, third-parity cows exhibited ePE concentrations that were higher than those of other parity cows. The days from parturition to 1stOV correlated with days from parturition to conception. On the day of 1stOV, milk yield correlated with plasma concentration of both ePE and ePC, while ePC concentration correlated negatively with milk fat percentage. At the early luteal phase after 1stOV, plasma ePE concentration correlated with plasma anti-Müllerian hormone concentration (r =0.39, P <0.01), and plasma ePC concentration correlated with plasma follicle-stimulating hormone concentration (r =0.43, P <0.01). CONCLUSION: The concentrations of ePE and ePC changed dramatically around parturition and 1stOV, and the concentrations correlated with important parameters for milk production and reproduction. IMPLICATIONS: The blood plasmalogen may play important roles in postpartum dairy cows.

Prediction of energy balance from milk traits of Holsteins in Japan.

We predicted the energy balance (EB) of Holstein cows in Japan from milk traits obtained by herd testing. Records covered 156 lactations of 102 cows. The number of artificial inseminations was highest, and the first conception rate was lowest in the low-EB group. Four prediction models were developed-for the whole lactation and for the early, middle, and late stages of lactation-with 20 variables, covering days in milk (DIM), milk yield, and milk composition traits. The actual and predicted EB means agreed well within DIM classes; the means of the residuals were smaller in the lactation stage models than in the all-lactation model, but the standard deviations (SDs) of the residuals were similar among models. After data reduction, the SDs of the residuals for 100 iterations were <1 throughout lactation in both types of models when n = 100. After model reduction, including the daily change of milk yield as a variable minimized the SDs of the residuals. Our equations for herd-level EB prediction have potential for use in genetic evaluation.

Effect of roll clearance of mechanical processing of corn silage harvested at the black-line stage of maturity on carbohydrate and protein utilization in dairy cows.

The experiment was conducted to evaluate the effect of roll clearance of mechanical processing of whole plant corn silage (CS) on carbohydrate and protein utilization in dairy cows. Treated CS was harvested at the black-line stage of maturity and chopped at a theoretical length of cut (TLC) of 9.5 mm without processing or at a TLC of 19 mm with processing at a roll clearance of 1, 3 and 5 mm. Four ruminally and duodenally cannulated dry cows were assigned to a 4 × 4 Latin square design for 14-day periods. Cows were fed diets containing 77% CS and 23% soybean meal (dry matter basis) to equalize the crude protein supply. Mechanical processing had no significant effect on dry matter intake and neutral detergent fiber digestibility. Ruminal and total tract starch digestibility and total digestible nutrients tended to be higher with processing at a roll clearance of 1 or 3 mm than at 5 mm. Microbial nitrogen efficiency in cows did not differ among all treatment groups. These results suggest that when CS is harvested at the black-line stage of maturity, roll clearance should be 3 mm or less with a TLC of 19 mm.

Effects of length of cut and mechanical processing on utilization of corn silage harvested at the black line stage of maturity by lactating dairy cows.

The effects of length of cut and mechanical processing on corn silage utilization by dairy cows were evaluated. Corn silage treatments were harvested at the black line stage of maturity and chopped at a theoretical length (TLC) of 9.5 mm without processing (Control) or at a TLC of 19 mm with processing at roller clearances of 1, 3, or 5 mm. Eight multiparous Holstein cows were assigned in a replicated 4 x 4 Latin square design with 21-day periods. Corn silage treatments were fed in diets containing 78.3% corn silage and 21.7% soybean meal (DM basis). Treatments had no significant effects on DMI, milk and 4% FCM production. The efficiency of converting DMI to FCM tended to be greater with processing at a roller clearance of 1 and 3 mm than at other clearances. Apparent total tract digestibility of starch tended to be lowest for cows fed control silage, and increased as roller clearance decreased. Ruminal ammonia concentrations in cows fed control silage were numerically higher than in cows fed proccesed silages. These results suggest that when corn silage is harvested at the black line of maturity, roller clearance should be 3 mm or less with a TLC of 19 mm.