Abstract:
In conditions where supplementation of poor quality diets is a major challenge, forage
legumes such as Sericea lespedeza can be a good alternative supplement for protein at lower
cost than most commercial concentrates. From studies done on Sericea lespedeza it is found
plausible and valuable to supplement urea with Sericea lespedeza to strategically combat the
deleterious effect of condensed tannins in the Sericea lespedeza and provide nitrogen in the
rumen. This study was aimed to evaluate the effect of replacing sunflower oilcake with urea
(a rumen degradable protein RDP source) or Sericea lespedeza (rumen undegradable protein
RUP source) mixed with urea as nitrogen/protein sources on nutrient utilization, milk yield
and milk composition of Saanen dairy goats. A digestibility and lactation study were
conducted at the University of Pretoria Research Farm and chemical analysis performed at
the University Nutrilab.
A 30 days digestibility study was conducted on male Saanen goats after the lactation
study, with 23 days adaptation and 7 days data collection period. Nine male goats were
randomised and allocated to the three treatments in metabolism cages. In the lactation study
36 dairy goats were blocked according to milk collected on first month of lactation into high,
medium and low milk yielders, then allocated to the three treatments of total mixed rations
containing sunflower oilcake (T1) at 7% main protein source, T2 (urea at 1%) and
T3- Sericea lespedeza at 12.5% mixed with urea according to a complete randomised block
design (CRBD). Milk samples were collected from individual goats monthly at two
consecutive milking’s. The samples were analysed for milk fat, protein, lactose, somatic cell
count and milk urea nitrogen using a Milko-Scan analyser (at Irene Lacto lab).
In the digestibility study, dry matter intake was significantly higher for goats fed on
Sericea lespedeza with urea (T3) diet than goats fed on T1 and T2 diet. Goats on T3 diet had
also significantly higher organic matter and crude protein intake than those goats fed on the
other two TMR diets. The results also shows that the mean daily milk yields for the goats in
the T1, T2 and T3 were 2.56, 2.46 and 2.52 kg per day respectively. T2 group had higher
milk fat % (3.61) and higher milk urea nitrogen (MUN - 25.70 mg N/dl) than the other two
treatments. T1 had significantly higher milk protein %. There was a great difference in milk
composition of the afternoon milk as compared to the morning milk. The three TMRs had no
significant difference in the nitrogen utilization and nitrogen excretion.
It is then concluded that Sericea lespedeza mixed with urea can be used as subsititutes
for sunflower oilcake in the diets of dairy goats since no negetive effect was found. However
further investigations are needed.
