نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
Effects of Ground versus Moist Barley and Corn Grains and Rumen-Protected L-Carnitine Supplementation in Transition Diets on Productive Performance and Inflammatory Responses of Holstein Dairy Cows
Introduction: The transition period, spanning approximately three weeks before to three weeks after parturition, represents the most physiologically demanding phase of the lactation cycle in high-producing dairy cows. During this period, cows simultaneously confront negative energy balance, extensive adipose tissue mobilization, oxidative stress, and a transient systemic inflammatory response, all of which can compromise metabolic adaptation, animal welfare, and subsequent lactational performance. Nutritional strategies capable of improving ruminal starch fermentability and hepatic fatty acid oxidation during this critical window are therefore of considerable practical interest. Among such strategies, moisture-based grain processing (as opposed to conventional dry grinding) and dietary supplementation with rumen-protected L-carnitine have each been shown, independently, to influence starch digestibility, energy metabolism, and inflammatory status; however, information regarding their combined and potentially interactive effects remains limited. The present study was therefore designed to evaluate the effects of two barley and corn grain processing methods (dry-ground versus moistened) combined with rumen-protected L-carnitine supplementation (unsupplemented versus supplemented) on productive performance, milk composition, milk fatty acid profile, blood biochemical parameters, and inflammatory biomarkers in transition Holstein dairy cows.
Materials and Methods: Sixty multiparous Holstein cows, with an average previous 305-day milk yield of 10,800 kg, body weight of 727 ± 40 kg, and parity of 3 ± 0.2, were enrolled in a 2 × 2 factorial arrangement of treatments from four weeks before to four weeks after calving. The four dietary treatments consisted of: (1) dry-ground barley and corn without L-carnitine, (2) dry-ground barley and corn with L-carnitine, (3) moistened barley and corn without L-carnitine, and (4) moistened barley and corn with L-carnitine. Rumen-protected L-carnitine (Carneon 20 Rumen Pro) was top-dressed at 100 g/cow/day. Data on dry matter intake, milk yield, milk composition, milk fatty acid concentrations, and weekly blood biochemical profiles were collected throughout the trial, while blood samples for inflammatory and gene-expression analyses were obtained on days −7, +7, and +14 relative to calving. All repeated-measures data were analyzed using the MIXED procedure of SAS with cow nested within treatment as the random effect and time as the repeated factor.
Results and Discussion: Cows fed moistened grains, particularly in combination with L-carnitine, exhibited significantly higher concentrations of milk protein, casein, non-protein nitrogen, lactose, total solids, and solids-not-fat than those fed dry-ground grains (P < 0.05). Daily yields of fat, protein, lactose, total solids, and solids-not-fat, as well as 3.5% fat-corrected milk (FCM) and energy-corrected milk (ECM), were all greatest in cows receiving moistened grains plus L-carnitine, reflecting the combined benefits of enhanced ruminal starch fermentation and improved energy utilization efficiency. Although the main effect of treatment did not significantly alter the concentrations of trans, cis, saturated, or monounsaturated milk fatty acids, all fatty acid groups displayed significant treatment × time interactions, indicating that the ruminal biohydrogenation response evolved dynamically over the course of the trial rather than differing consistently between treatments. Blood glucose and cholesterol concentrations were highest in cows fed moistened grains, consistent with increased ruminal propionate production and enhanced hepatic gluconeogenesis, whereas L-carnitine supplementation reduced circulating VLDL and ALT activity, suggesting improved hepatic lipid handling and reduced hepatocellular stress. Importantly, cows fed moistened grains combined with L-carnitine exhibited the lowest circulating concentrations of tumor necrosis factor-alpha, interleukin-1 beta, haptoglobin, and serum amyloid A, indicating an attenuated systemic inflammatory response, likely mediated through improved energy status, reduced non-esterified fatty acid mobilization, and enhanced mitochondrial fatty acid oxidation capacity. Notably, milk somatic cell count remained unaffected by treatment, confirming that the observed improvements in milk composition and yield were attributable to metabolic and nutritional factors rather than changes in mammary gland health status.
Conclusion: these findings demonstrate that combining moisture-based grain processing with rumen-protected L-carnitine supplementation exerts complementary, and in several respects synergistic, effects on lactational performance, energy metabolism, and inflammatory status of transition Holstein dairy cows. This nutritional strategy may represent a practical and cost-effective approach for improving milk yield and mitigating metabolic and inflammatory disorders commonly encountered during the transition period, warranting further investigation into its long-term effects on reproductive performance and overall herd health.
Keywords: Transition period; Grain processing; L-carnitine; Milk composition; Inflammatory response; Holstein dairy cow
کلیدواژهها English
