TITLE:
Comparison of Brown Midrib Sorghum with Conventional Sorghum Forage for Grazing Dairy Cows
AUTHORS:
Laura Astigarraga, Ana Bianco, Ricardo Mello, Dana Montedónico
KEYWORDS:
Brown Midrib; Forage Sorghum; Digestibility; Milk Production; Dairy Cows
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.5 No.7,
March
26,
2014
ABSTRACT: A brown midrib (BMR)
sorghum pasture was compared with normal sorghum for its effects on performance
of Holstein cows in midlactation in terms of milk production and composition at
grazing over three periods (Period 1: 20/01 to 31/01, Period 2: 17/02 to 28/02,
Period 3: 19/03 to 30/03). Forty Holstein cows were grouped according to pre-experimental
milk production (22.4 ± 4.2 kg/d milk), live weight (530 ± 25 kg) and lactation
stage (127 ± 63 days) and assigned randomly to one of the two experimental pasture.
Pasture was assigned on equal basis at an allowance 25 kg DM/cow/day (above 10 cm),
assuming a 65% forage utilization and cows received 4 kg of concentrate per day.
Simultaneously, both pastures were evaluated with sheep, to analyze digestibility
at every grazing period. The BMR sorghum supported higher FCM than normal sorghum
(18.5 vs. 17.8 l/day, P 0.05),
with fewer intake of concentrate (-0.4 kg/day/cow, P 0.05)
when compared with cows grazing normal sorghum. Those results are in accordance
with greater (P 0.05)
total digestive tract DM, OM and NDF in vivo digestibilities for BMR sorghum (65.0,
67.1, 65.9 respectively) than for normal sorghum (60.3, 62.0, 61.3 respectively).
The increased digestibility of BMR sorghum must be associated with the compositional
differences on fiber which allowed a higher cell wall digestion. Results of this
study indicate that the BMR sorghum hybrid outperformed the normal sorghum hybrid
resulting in a higher performance per cow with lower concentrate consumption compared
with normal sorghum.