Improving Milk Quality and Animal Health By Efficient Pasture Management
Three grazing systems: intensively managed rotational grazing (IMRG), traditional continuous grazing (TCG), and confinement housing (CH), were compared on seventeen Vermont dairy farms to determine if grazing systems had an effect on milk quality, animal health and reproductive efficiency. Analysis of variance, using a general linear means procedure, on monthly bulk tank milk samples for standard plate count were not significant at P,.05; however, differences indicated trends towards improved milk quality during the grazing season in pastured herds compared with confined herds. Mean standard plate count during May through October for IMRG herds and TCG herds (4.28 X 103 cfu/ml) and (4.97 X 103 cfu/ml) were lower compared with CH herds (12.67 X 103 cfu/ml).
Samples cultured on trypticase blood-esculin agar to determine total bacteria count and distribution of specific bacterial types and species, and somatic cell count (SCC) indicated differences during the grazing season towards lower mean counts of streptococci other than Streptococcus agalactiae in herds using IMPG (996 cfu/ml) compared with TCG and CH (2,242 and 1,416 cfu/ml). Mean CH (2.15 X 105 cells/ml) than either TCG or CH (2.15 X 105 cells/ml) during the grazing season.
Animal health and reproductive efficiency were evaluated by analyzing monthly reports by veterinarians incorporating barn records, DHIA test reports, and biweekly or monthly herd clinics. Mean occurrence of diseases, disease incidence densities, and estimates of risk were similar in all treatments for metabolic disorders, lameness and reproductive disorders. Udder disease, including clinical mastitis, udder edema, and teat injuries, were consistently less in herds managed on pasture compared with herds managed in confinement. When herds with fewer than 60 lactating cows were compared, incidence density of udder diseases was .09 cases/animal month in IMPG, .03 cases/animal month in TCG, and .16 cases/animal month in CH.
A LISA dairy seminar by participants informed the northeast dairy industry of project results. The seminar summarized results of grazing management on milk quality and animal health. Topics included monitoring of milk quality and herd health; incentive payments and milk pricing; summer forage feeding and protein quality in forage; and economics of grazing management. A highlight of the seminar was a small group discussion by participants expressing views on information they need for agriculture to be sustainable.
(1) Compare economic effects of Voisin grazing, continuous grazing and confined housing systems on milk quality parameters.
(2) Determine incidence of mastitis in dairy cows managed under Voisin grazing and confined housing systems.
(3) Compare effects of Voisin grazing, continuous grazing and confinement on reproduction.
(4) Compare effects of these systems on animal health.
(5) Determine economic implications for farms when applying these systems.
(6) Disseminate results to the northeast dairy industry.