Abstract
Simple SummaryPrevious study revealed that the rumen bacterial community was in temporal dynamics, even after an adaptation of three months when diet shifted, while the dynamic rumen bacterial community is not necessarily in accord with varied rumen fermentation characteristics. Thus, no proper time for practical sampling frequency is available for conducting basal nutritional research in the long-term fattening stage of steers. This study aimed to evaluate the proper time for nutrient apparent digestibility, serum metabolic parameters, and rumen fermentation characteristics to stabilize when diet shifts. Results showed that nutrient apparent digestibility and serum metabolic parameters were stable across each collection month, while most rumen fermentation characteristics were affected by the interaction effects between collection period and dietary density. These results indicate that rumen fermentation characteristics require more time to stabilize when diet shifts, and it is recommended to collect ruminal digesta monthly to evaluate rumen fermentation characteristics.This study was conducted to explore the proper time required to achieve stabilization in digestibility, serum metabolism, and rumen fermentation characteristics when different diets shift, thus providing decision-making of practical sampling frequency for basal nutritional research. For these purposes, 12 Holstein steers (body weight 467 ± 34 kg, age 14 ± 0.5 months) were equally assigned to two dietary treatments: high-density (metabolizable energy (ME) = 2.53 Mcal/kg and crude protein (CP) = 119 g/kg; both ME and CP were expressed on a dry matter basis) or low-density (ME = 2.35 Mcal/kg and CP = 105 g/kg). The samples of feces, serum, and rumen contents were collected with a 30-day interval. All data involved in this study were analyzed using the repeated measures in mixed model of SPSS. Results showed that nutrient apparent digestibility and serum metabolic parameters were stable across each monthly collection, while most rumen fermentation characteristics, namely concentrations of acetate, propionate, isobutyrate, and valerate, were affected by the interaction effects between collection period and dietary density. These findings indicate that rumen fermentation characteristics require more time to stabilize when diet shifts. It is recommended to collect ruminal digesta monthly to evaluate rumen fermentation characteristics, while unnecessary to sample monthly for digestion trials and blood tests in the long-term fattening of Holstein steers. This study may provide insights into exploring the associations between detected parameters and stabilization time, and between diet type and stabilization time when diet shifts.
Highlights
Nutritional studies with cattle are time-consuming and costly [1]
No interactions between dietary nutrient density and collection period were observed in the apparent digestibility of Dry matter (DM), Organic matter (OM), Crude protein (CP), Ether extract (EE), Neutral detergent fiber (NDF), and Acid detergent fiber (ADF) (p > 0.10)
No differences were observed in nutrient apparent digestibility due to collection period, except for an increase in the apparent digestibility of OM (p = 0.003)
Summary
Nutritional studies with cattle are time-consuming and costly [1]. Health and biological functioning of livestock are often prioritized, and adaptation is necessary for animals to maintain metabolic balance when they are in a transition period [2,3]. An adaptation period is needed in order to obtain representative samples for determination of nutrient apparent digestibility, serum metabolic parameters, and rumen fermentation characteristics, and is widely used in practical research of ruminants [4,5]. Evaluation of the acceptable sampling frequency in each fattening stage could save both time and labor without detriment to the representativeness of detected samples, and assessment of the minimum time to achieve stability is an intuitive approach to determine the adaptation period. Basal nutritional research with finishing cattle generally involves digestion trials to evaluate digestibility, blood tests to assess nutrition and health status, and ruminal digesta determination to monitor fermentation. Machado et al [1] reported that the required time for stabilization varied with detected parameters when diet shifted, such as 9–13 days for voluntary intake, 6–13 days for ruminal digesta composition, and
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