The Rumen Degradation And Utilization Of Corn Starch And Growth Of Hu-sheep Fed On It As Influenced By Corn Processing

The starch digestion, absorption, and utilization of ruminants are-different to those of nonruminants, with their large pregastric fermentation compartment (rumen). Generally, strach is rapidly degraded and absorbed as VFA in the rumen, and less is digested and absorbed as glucose in the small intestine, which influences the transformation efficiency of energy and results in the decreased production performance. Furthermore, excessive starch degrated in rumen could reduce pH and result acidosis. Therefore, this study was conducted to investigate the effects of corn processing on the degradation and utilization of starch and the growth performance of huzhou sheep. The processing such as grinding and crushing were studied.Trial 1, the effect of different processing on the rumen degradation and fermentation of corn starch was investigated. The nine Hu-sheep equipmented with rumen cannulas, aged of 2 to3 months, were randomly divided into three groups and used to determine the disappearance rate of dry matter and starch of corn by using nylon bags technique, rumen pH, and the count of rumen protozoa. The ground corn (GC) had the highest disappearance rate of dry matter at every incubation time, which was significantly (P < 0.01) higher thanthat of crushed (CC) or whole com (WC). The disappearance rate of dry matter of GC, CC and WC was 92.8, 73.5 and 22.5% at 48h incubation in rumen, respectively. The disappearance rate of com starch was positively correlative to the disappearance rate of dry matter of com. Of three processing corns, the GC had the highest disappearance rate of starch at every incubation times.The rumen pH was decreased quickly after sheep fed on ground corn. The rumen pH was 5.95 at the 3 hours after Hu-sheep was fed on ground com, which was significantly (P<0.01) lower than that of sheep fed on crushed corn (6.63) or whole corn (7.05). Their pH values were decreased to 4.98, 5.97 and 6.82 after 12h feeding, respectively. The amount of rumen protozoa was significantly lower for sheep fed on ground corn (2.84 X 105/ml) than that of animals fed on crushed com (4.94 X 105/ml) and whole corn (5.22 X 105/ml) after 6h feeding (PO.01). However, there was no significant difference between that of CC and WC (P>0.05), except of the count at 12h feeding, which was 4.81 and 5.26 (X 105/ml), respectively.Trial 2, the effect of different com processing on the quantity of starch entering into the abomasums was investigated. The nine Hu-sheep with abomasum cannulas, aged of 2 to 3 months, were randomly divided into three groups and used to determine the content of residual corn starch in the abomasums of Hu-sheep. The result indicated that, although the degradability of starch in rumen was increased with the increase of crushed extent, but the content of residual starch was decreased in abomasum. At any time, the content of residual com starch in abomasum showed WC > CC > GC, with the values of 8.93%, 6.18% and 3.43% in turn after 48h feeding. However, there was no significant difference observed in the content of residual starch between different times for the same processed com.Trial 3, the growth of Hu-sheep fed on different processed corns was determined. The thirty-six Hu-sheep (18 males and 18 females) of 2 to 3 month age were randomly divided into 3 groups according to greement in sex. Each group had three cotes, one for four males, one for four females, and the other for two males and two females. The three different processed corns (ground, crushed or whole corn) were respectively fed to one of three groups and the growth of sheep was measured. After 90 days experimental period, the average daily gains were 47.3, 58.8 and 63.7 (g/d) for sheep fed on ground, crushed and whole corn, respectively. Sheep fed on whole corn had significantly (PO.05) higher dailygain than those fed on ground or crushed com did, with an obviously increasing trend on the daily gain for animals fed on crushed com over ground com (P>0.05).Based on the above-mentioned results, it was suggested that with the decrease of crushed extent of com, the rumen by-pass starch from maize can be greatly increased and the growth of Hu-sheep fed on com may be obviously improved. The Hu-sheep fed on whole com had greatly higher daily gain than those fed on ground or crushed com did, and also the animals fed on crushed corn tended to have obviously higher gain than those fed on ground com.