Use of COSREEL, a computerised recording system, for herd health management of two dairy herds

Comparison of reproductive performance in Belgian dairy and beef cattle

A computerized program was written to collect, evaluate and compare reproductive performance data of 2004 beef (Belgian Blue breed) and 1649 dairy (Friesian Holstein and German Red) cattle in 35 Belgian herds (6 suckler beef herds, 9 milked beef herds and 20 dairy herds). Reproduction data were collected at monthly herd health visits. No difference in age at first calving was observed. Significant differences were observed among the 3 kinds of herds, and the best results were obtained in dairy herds for the calving interval, interval from calving to the first estrus, interval from calving to the first service and average number of days open. Concerning these parameters, first calvers had lower results than multiparous cows, mainly in suckler and milked beef herds. Significant differences were noted in the number of services per pregnancy. Heifers that had never calved presented the highest fertility. Primiparous beef cows had higher fertility than pluriparous cows. In dairy herds, pluriparous cows had higher fertility than primiparous cows. Estrus detection was better in milked beef herds than in suckled beef and dairy herds. Suckled beef herds had the lowest incidence of metritis and ovarian cysts of the three types of herds. Rates of abortion, overall culling and retained fetal membranes were similar in all the herds. The percentage of animals removed for infertility was highest in milked beef herds and lowest in dairy herds. Because 90% of the 1159 calvings recorded in the beef herds required a caesarean section, the reproductive performance of beef cattle represent results after caesarean section.

The association between clinical mastitis and milk yield in dairy cows

A study of 1514 lactations that occurred between 1977 and 1982 in 790 Friesian, Ayrshire and Holstein crossbred cows was undertaken. One thousand and eighty-four of these lactations were used to consider the association between the occurrence of clinical mastitis and changes in milk yield, and to illustrate a technique that enables the previous lactation history of a cow to be used for estimating changes associated with the disease.

The lactation curves were described using the model y(n) = anbe−cn from which values for peak yield, persistency, rate of decline at week 25, and recorded and extrapolated 305-day yield were calculated. A significant correlation between successive lactations of the same animal was observed for each of these variables. Pairs of successive lactations free from clinical mastitis were then compared by regression analysis with lactations in which the preceding lactation was free from the disease whilst the second lactation of the pair was infected.

Significant reductions in peak yield, recorded and extrapolated 305-day yield were found when mastitis occurred before the week of peak yield. A reduction in recorded 305-day yield was also observed when the disease occurred between peak and 10 weeks after peak. Mastitis later in the lactation had no significant effect.

The mean reduction in recorded 305-day yield of 540 kg when mastitis occurred before peak for a cow with a mean yield of 4830 kg, was higher than previous estimates. No evidence of recovery was observed in subsequent lactations that were free of clinical infection, indicating that once a cow has contracted mastitis it may not achieve its full milk-yield potential in the next lactation.

Factors affecting days of discarded milk due to clinical mastitis and subsequent cost of discarded milk

Records of clinical mastitis for 6.5 yr from one Florida dairy with 1050 to 1350 cows milking per month were used to predict duration of occurrence of clinical mastitis and to estimate dollar value of discarded milk per lactation with occurrences of clinical mastitis. Only 6.1% of lactations accrued more than 28 d of discarded milk and were responsible for 52.7% of days of discarded milk. Accurate maintenance of herd mastitis records enables calculation of actual days of milk available for sale and provides a useful tool for culling and treating decisions. Duration of each occurrence of clinical mastitis was modeled by fixed effects of breed, season of occurrence, current lactation history of mastitis, number of quarters with clinical signs, and average maximum temperature-humidity index for the 2 d prior to the occurrence (to second order). These effects explained 1.8% of observed variation in duration of occurrence. Random effects of cow explained 5 to 6% of variation. Prediction of duration of occurrence had a mean value of 6.6 d. When economic status of individual animals is evaluated, comparison of days of milk production available for sale is preferable to total days of milk production. Estimated average cost of discarded milk for parities 1, 2, 3, 4, and 5 ranged from $29.73 to 223.98 per lactation.