| Summary: | 碩士 === 國立嘉義大學 === 動物科學系研究所 === 106 === Feeding high-protein diets with unbalance amino acids in animals can lead to a decrease of nitrogen utilization efficiency, and then promote the environmental pollution. Lowering the dietary protein level and modifying amino acids (AAs) balance can reduce the emission of nitrogen, which is largely responsible for the environmental issues. Meanwhile, a number of studies have shown that several dysfunctions such as intestinal dysfunction in weaning mammals can be induced by high protein diets. Nevertheless, lowering the dietary protein level might
lead to the deficiency of some crucial EAAs that cannot be synthesized in vivo. Recently, more reports have demonstrated that lowering protein level in diets supplemented with specific amino acids can address these
problems. Replacing a portion of the dietary crude protein content by supplementing synthetic AA is an useful approach to improve feed efficiency, reduce feed cost and also to obtain environmental benefits. For growing goats fed a corn grain and soybean meal diet, methionine (Met) was likely the first limiting amino acid, followed by lysine (Lys). So we use Met to Lys ratio as an indicator of AA balance. However, there were
few studies related to AA balance in goat kids starter. Therefore, the aim of this study was to estimate the effect of Met to Lys ratio under low protein level (17%) starter on goat kids growth, blood, digestive and
carcass traits. Treatment assigned 30 four-week-old (L block) and 15 six-week-old (H block) goat kids into three different Met to Lys ratio starter groups, as A (0.29), B (0.31), and C (0.33). In two-month trial, treatment collected growth performance and blood parameters every two weeks, and collected 5 goat kids’ digestive traits per group in L block in the 0-14 days of the treatment. Then slaughtered 3 goat kids per group from H block and measured their carcass traits after the treatment
finished. The results showed that in L block goat kids, there were no significant differences among different Met to Lys ratios, each blood parameter was in normal range without existing significant differences, only the concentration of albumin in the 6th and 8th week were lower in B group (P<0.05), with a quadratic effect (P<0.05). Otherwise, in H block goat kids, C group had a tendency of final weight, higher body weight gain and feed intake (P<0.1), but there was no significant difference in feed conversion ratio among three groups; in addition, all blood parameters were in normal ranges and didn’t have significant differences, only the concentration of γ-GT was lowest in B group. There were no significant difference between three groups’ dry matter and crude protein intake and their apparent digestibility. Then mentioned to carcass traits, C
group had significantly highest carcass weight and heart weight (P<0.05), with a quadratic effect (P<0.05), while its hair weight and lung weight also tend to be heavier (P<0.1). There were no significant differences in
the remaining carcass traits among the groups. In conclusion, goat kids relied on the nutrition of milk replacer rather than starter before weaning, however, providing Met to Lys ratio 0.33 starter could increase growth and carcass performance in H block goat kids, but had no significant differences on blood parameters. Hence, adjusting amino acid ratio from 0.29 to 0.33 under 17% CP starter had no significant effect on growth, blood, digestive and carcass traits, and it could not only decrease feed cost, have benefits to environment, but also increase feeding efficiency.
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