Bj. Van Den Merwe et al., The effect of monensin on milk production, milk urea nitrogen and body condition score of grazing dairy cows, S AFR J AN, 31(1), 2001, pp. 49-55
Citations number
49
Categorie Soggetti
Animal Sciences
Journal title
SOUTH AFRICAN JOURNAL OF ANIMAL SCIENCE-SUID-AFRIKAANSE TYDSKRIF VIR VEEKUNDE
Twenty Holstein-Friesian cows, two to four months postpartum, were randomly
assigned to two groups. The control group received no monensin, whereas th
e treatment group received 300 mg monensin per cow per day. Cows grazed kik
uyu pasture and received maize-based concentrates (2% of body weight) in tw
o equal feeds after the morning and afternoon milkings. Monensin was supple
mented with the concentrates for six weeks. Monensin supplementation reduce
d the numbers (x 10(5)/cm(3)) of small protozoa (9.1 vs. 13.0) and large pr
otozoa (0.37 vs. 1.09) in the rumen. No significant difference was recorded
between control and treatment groups for average milk yield (21.6 +/- 0.7
vs. 22.1 +/- 0.7 kg/day), milk protein (2.91 +/- 0.05 vs. 2.84 +/- 0.04%) o
r milk fat (2.75 +/- 0.13 vs. 2.69 +/- 0.12%). The combined morning and aft
ernoon milk urea nitrogen concentrations of the monensin supplemented cows
(19.9 +/- 1.37 mg/dl) were lower than those of the control group (24.1 +/-
1.43 mg/dl). The average daily gain of the treatment group (471.4 +/- 87.5
g/day) was higher than that of the control group (193.9 +/- 52.8 g/day). No
significant difference was observed between the average condition score of
the control (1.4 +/- 0.1) and treatment (1.7 +/- 0.1) groups after six wee
ks. Although monensin supplementation reduced milk urea nitrogen concentrat
ions, these were still in the critical zone (> 18 mg/dl) which could negati
vely affect fertility. Monensin can play an important part in ensuring that
cows are in a stable or improving condition (i.e. gaining weight) at servi
ce time, this being an important prerequisite for improved reproductive eff
iciency.