Abstract
The objective of this experiment was to investigate the effects of substituting corn starch (CS) with barley starch (BS) on the growth performance, nutrient digestion, rumen fermentation, and bacterial community of fattening Hu sheep. Seventy-two Hu lambs with similar initial body weight (BW, 29.70 ± 1.70 kg) were randomly assigned to four treatments, with 18 lambs per group. The four experimental diets have identical starch contents but with different starch sources as 100% starch from corn (BS-0), 33% starch from barley and 67% starch from corn (BS-33), 67% starch form barley and 33% starch from corn (BS-67), and 100% starch from barley (BS-100). All lambs were reared in individual units and fed high-concentrate diets (85% concentrate in diets based on dry matter [DM]). The experimental period included 7 days for adaptation and 63 days for data collection. Sixteen ruminal cannulated Hu sheep were divided into 4 groups and received the four experimental diets to determine the dynamics of ruminal pH. The average daily gain (ADG), and BW gain of lambs linearly decreased (p < 0.05), whereas the feed to gain ratio linearly increased (p < 0.05) with increasing dietary proportions of BS. Digestibility of DM, organic matter, neutral detergent fiber, acid detergent fiber, starch, and gross energy (GE) decreased (p < 0.05) with increasing dietary BS contents. Ruminal mean pH decreased (p < 0.05) with increasing proportions of dietary BS, accompanied with linearly increased (p < 0.05) time and area of ruminal pH below 5.80 or 5.60. Increasing dietary proportions of BS linearly decreased (p < 0.05) the molar proportion of acetate, but linearly increased (p < 0.05) the molar proportion of propionate. Sheep of the BS-0 and BS-33 treatments had a less (p < 0.05) relative abundance of Selenomonas ruminantium than that of sheep of the BS-67 treatment, but a greater (p < 0.05) relative abundance of Ruminococcus albus than that of sheep of the BS-100 treatment (p < 0.05). In conclusion, feeding a high-concentrate corn-based diet for fattening Hu sheep improved the performance and rumen fermentation parameters when compared to the barley-based diet.
Highlights
Using cereal grain to increase the dietary starch contents is a commonly used strategy to improve the performance and feed efficiency of sheep [1], dairy cow [2], and beef cattle [3] under the modern intensive ruminant production systems
The final body weight (BW) of sheep had a tendency leading to a linear decrease (p = 0.09) with increasing dietary barley starch (BS); while the BW gain (BWG) linearly decreased (p < 0.05), with lower BWG (p < 0.05) during the experimental period in BS-100 than that in BS-0 and BS-33 (Table 3) The dry matter intake (DMI) did not differ among treatments; the average daily gain (ADG) linearly decreased (p < 0.05) with increasing dietary BS contents leading to a linearly increase (p < 0.05) for feed to gain ratio (F/G)
Lower (p < 0.05) ADG but greater (p < 0.05) F/G was observed in BS-100 than that in BS-0, which had similar BWG, ADG, and F/G with BS-33 and BS-67
Summary
Using cereal grain to increase the dietary starch contents is a commonly used strategy to improve the performance and feed efficiency of sheep [1], dairy cow [2], and beef cattle [3] under the modern intensive ruminant production systems. The degradation rate of starch in corn was lower than that in barley after dry-rolled [4, 5]. The lower degradation rate of corn starch (CS) compare to the other sources of starch in diets could decrease the risk of subacute ruminal acidosis (SARA) in high production ruminates [6, 7]. Corn grain is an important energy source and is widely used in the ruminant livestock industry in China. The price of corn grain raised nearly 50% in China from 2020 to 2021, resulting in a dramatic increase in feed costs for ruminant production. It is important to study alternative cereals such as barley or wheat to replace corn, so that to decrease the feed costs without affecting the performance of ruminants
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