Milk secretion rate in tropical dual purpose cows (B. taurus x B. indicus)

Abstract

Cumulative milk volume (CMV) and milk secretion rate were estimated in eight B. taurus × B. indicus cows. Cows were in peak lactation (∼45 days), routinely milked twice a day, supplemented at each milking with about 3 kg DM in concentrate and grazing star grass (Cynodon nlemfluensis) with the main herd as to cover the AFRC (1993) energy and protein requirements. CMV and secretion rate were estimated by milking each cow at 3,6,9,15 and 24 h intervals. Each milking interval measurement was on different days within the same week. Measurements were performed four times for each time interval in four weeks. Empty udder volume (EUV) was measured during the 2nd week of the experiment. Ten IU i.m. oxytocin was used both at previous and scheduled milking interval as well as for the EUV measurement to ensure complete udder emptiness. For 3, 6, 9, 15 and 24 h milking intervals, CMV (L) were 0.38, 0.74, 1.237, 1.69 and 2.40±0.041 per L EUV, while, milk secretion rate (L·h-1) were 0.125,0.123,0.137,0.113 and 0.100±0.004 per L EUV, respectively. A significant relationship was found between milk yield (MY) and EUV (MY=4.136 (±2.259) + 2.129 EUV (±0.396); R 2=0.491). The MY loss as result of having a 24 h milking interval in comparison with having 15+9 h intervals was on average 17±1.9% (MY=2.69(± 1.16)-0.349 MY (±0.071 ); R2=0.449). Udder productivity of B. taurus × B. indicus cows is similar to dairy cattle. CMV and milk secretion rate must be taken in consideration when designing milking and restricted suckling regimes for this type of cattle.