| Sumario: | Insufficient feed supply is a major limiting factor for milk production in the tropics. The
aim of this study was to assess the effects of feeding level on live-weight and performance
of Zebu (Boran) and crossbred (Boran
×
Holstein, 50–75% Holstein) lactating cows.
Twenty-four heifers of each breed 20 to 36 months of age were allocated to three feeding
levels (1.0, 1.2 and 1.4 times of maintenance energy requirements) until the end of the
second lactation. The results of the two lactations are reported here. The diet consisted of
grass hay and wheat bran in a ratio 2:1. A mineral block and water were given ad libitum.
In both lactations, increasing feeding level resulted in higher daily milk yields by cross-
bred but not by Zebu cows. Milk composition was not affected by level of nutrition. How-
ever, the milk of Zebu cows contained more fat, protein and solids than that of crossbred
cows. Average live-weights during lactation increased with feeding level in both breeds but
the response was higher in crossbred cows. However, the effect of feeding level on weight
changes during the lactation was not significant. Lactation length significantly differed
between genotypes. Zebu cows ceased producing milk at less than 250 days after calving
whereas crossbred cows had more than 300 days of lactation. The calving interval did not
differ between genotypes. Compared to the first lactation, live-weight and milk yield were
maintained and lactation length slightly decreased in the second lactation.
These results suggest that the response to increased feeding level of crossbred cows is
higher than that of Zebu cows. Therefore, crossbreds would be an appropriate option in
those areas where more and better quality feed can be produced and with access to milk
markets.
|
|---|