β-alanine has been shown to significantly improve nitrogen utilization efficiency in beef cattle, but its impact on growth performance remains unclear. This study involved 36 healthy 18-month-old Simmental crossbred bulls with similar weights (627 ± 41 kg). The cattle were divided into two groups, with each group comprising six replicates of three animals. While the control group received the basal diet, the treatment group was administered an additional 96 g/d/cattle rumen-protected β-alanine (RP-β-Ala). The study was conducted over a 35-day period, which included an initial 7 days for adaptation. At the end of the trial, body weight was recorded, and samples were collected. Results show that RP-β-Ala enhanced average daily gain (p = 0.065) and crude protein (CP) digestibility (p = 0.065) and reduced gain-to-feed ratio (p = 0.078). Analysis of rumen microbiota revealed that RP-β-Ala positively modulated the rumen microbiota by enriching beneficial genera such as Prevotella, Treponema, and Selenomonas. This enrichment increased volatile fatty acid production and nitrogen utilization efficiency, as evidenced by elevated ruminal ammonia-N and microbial CP levels, along with decreased serum urea nitrogen. Metabolomics identified key alterations in arachidonic acid metabolism, specifically the upregulation of metabolites 14,15-DiHETrE and prostaglandin D2, and enhanced antioxidative capability indicated by increased serum total antioxidant capacity (T-AOC). Concurrently, RP-β-Ala reduced serum TNF-α levels. This reduction was achieved by suppressing harmful bacteria like Thermoactinomyces and Saccharopolyspora, along with inhibiting their polyamine synthesis, specifically spermine and spermidine. Collectively, these effects alleviated oxidative stress and inflammation. These findings demonstrate that RP-β-Ala enhances beef cattle growth through improved energy supply and antioxidant capacity.

Preslaughter nutritional strategies that preserve energy reserves in transported beef cattle may help maintain normal post-mortem muscle metabolism and meat quality. β-alanine, a carnosine precursor, enhances glucose metabolism and glycogen reserves. This study evaluated the effects of rumen-protected β-alanine (RP-β-Ala) on meat quality, hepatic gluconeogenesis-related indices, and muscle energy metabolism in long-distance transported cattle. Thirty-six healthy 18-month-old Simmental crossbred bulls (627 ± 41 kg) were randomly assigned diets containing 0 (control) or 96 g/head/d RP-β-Ala. After 28 days of feeding, serum was sampled from six bulls per group. Following a 2-day rest (RP-β-Ala supplementation continued), these twelve bulls were transported, slaughtered, and sampled. Transport significantly increased serum lactate dehydrogenase (LDH) and creatine kinase (CK). The transport × RP-β-Ala interaction significantly affected serum superoxide dismutase (SOD). Post-slaughter tissue indices were analyzed solely for the effect of RP-β-Ala supplementation, as all slaughtered bulls underwent transportation. Compared to controls, the RP-β-Ala group exhibited significantly higher muscle pH_{45 min} and an accelerated pH decline rate within 24 h post-mortem in both M. longissimus dorsi (LD) and M. semitendinosus (ST) muscles. In LD muscle, hardness, shear force, gumminess, and chewiness significantly decreased, while ATP content and HK, PFK, PK, and LDH activities significantly increased. In ST muscle, lactate content and GP, HK, PFK, and LDH activities significantly increased. In the liver, glucose, lactate, ATP, and ADP contents significantly increased, alongside enhanced G-6-Pase and pyruvate carboxylase (PC) activities. Dietary RP-β-Ala supplementation may regulate energy metabolism in transported cattle by enhancing muscle glycolytic activity and indices associated with hepatic gluconeogenic capacity, thereby improving selected meat-quality traits.