Seasonal Influences on the Productive Performance of Horro Cows at Bako, Ethiopia

Abstract

Ten years’ data of milk production and reproduction from 473 Horro cows at Bako Agricultural Research Center was investigated if there was seasonal variation in milk production and reproductive parameters (days open and services per conception) of Horro cows. Cows grazed on natural pasture for about 7 hours by day and kept in barns at night. Supplementary feeds (hay, silage, concentrate) were provided to cows from 7 months of pregnancy until parturition and only concentrate meal during milking. Multiple regression analysis from SAS was used to investigate the relationship of milk production, days open and services per conception with mean temperature, relative humidity, sunshine hours and wind speed. Stepwise selection procedure was used to examine the different regression equations. Mean temperatures and Temperature Humidity Index remained higher in February to April, after which they declined. Milk yield was affected by daily mean temperature (P<0.001), sunshine hour
(P<0.001) and wind speed (P<0.05). The over all mean (±SE) milk yield (kg) of the cows was 402.86±19.31 over a mean lactation length of 185±4.77 days. Production did not vary significantly (P>0.05) among seasons, but was higher for cows calved in the spring and summer. Milk production was
found to be significantly (P<0.01) influenced by parity; yields increasing from parity one to parity four where it peaked. Services per conception were significantly (P<0.01) affected by only relative humidity. Significant (P<0.05) differences were observed in days open with the highest days open being in February (224 days). Days open was significantly affected (P<0.001) by daily mean temperature.