Milk yield depression and its economic loss due to production diseases: Iran's large dairy herds

Incidences of production and metabolic diseases in dairy cows have increased over the last few decades because of the increasing trends in milk production. Production diseases cause different and distinct depressions in milk production that lead to different and major economic losses in large dairy herds.

The objective of this study was to determine milk production depression and its economic losses due to different production diseases in selected large dairy herds of Iran.

Production and health data from 17 large dairy herds with a total of 146464 observations across three parities were obtained. Milk yield depressions were estimated for three phases of lactation including 1) 5-60, 2) 61-120, and 3) 121-180 days in milk. Data were analyzed using Mixed Models of SAS program (v. 9.3) with fixed effects of the diseases, calving year, calving month, parity, and herd with cow age at calving as covariates.

The data demonstrated significant effects of different production diseases on milk production depression during 5-60, 61-120, and 121-180 days in milk (P<0.05). During 5-60 days in milk, ketosis, displaced abomasums (DAs), laminitis, mastitis, metritis, retained placenta (RP), and dystocia resulted in, respectively, 253, 682, 39, 38, 110, 215, and 55 kg of milk yield depressions that were equivalent to 38.5, 103.7, 6.0, 5.8, 16.7, 32.6, and 8.4 U.S. Dollars (USD) economic losses. Milk yield depressions due to laminitis and mastitis over the 180 days in milk were, respectively, 207 and 404 kg equivalent to 31.5 and 63.0 USD economic losses. Since the milk yield depression constitutes about 20-35% of total costs of production and metabolic disorders, the total economic losses would be 3-5 times the above values.

Displaced abomasum and laminitis caused the highest and lowest depressions in milk yield, respectively. The findings suggest that commercial dairy production management strategies in Iran require reassessment and refinement. Overfeeding of concentrates should be ceased. Future economic and reproductive studies are needed to enable developing effective strategies for optimizing modern and postmodern dairy production in Iran.