نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
Twenty-four dry Holstein cows were used in a 2×2 factorial arrangement with four dietary treatments during the transition period (21 days before calving and 21 days after calving). The two factors were grain type (barley vs. corn) and the inclusion of a glucogenic additive. The treatments were as follows: 1) Barley-based diet without glucogenic additive, 2) Barley-based diet with glucogenic additive, 3) Corn-based diet without glucogenic additive, 4) Corn-based diet with glucogenic additive. The prepartum and postpartum diets differed in composition. Milk yield was not affected by dietary treatments, nor were milk composition parameters (protein and fat content). However, dry matter intake (DMI) postpartum tended to increase in cows fed the barley-based diet without the glucogenic additive. Nutrient digestibility (dry matter, organic matter, crude protein, non-fibrous carbohydrates, neutral detergent fiber, and fat) did not differ significantly among treatments. Similarly, ruminal parameters postpartum were not significantly influenced by dietary treatments, except for ruminal pH, which was lower in cows fed barley-based diets compared to those fed corn-based diets (p < 0.05). Ruminal ammonia nitrogen (NH₃-N) concentration was not affected by the treatments.
کلیدواژهها English
Extended Abstract
Introduction
Intensive genetic selection in dairy cows has raised milk yields but also increased nutritional challenges, especially during the transition period (21 days before and after calving). This phase involves hormonal transformations, reduced feed intake, and high energy demands, often causing negative energy balance and metabolic disorders such as ketosis, fatty liver, and mastitis. To reduce negative energy balance, research has focused on boosting glucogenic precursors, like propionate from starch and intestinal glucose absorption. Grain type matters, barley ferments faster than corn, potentially lowering intake due to higher propionate, though effects vary with diet composition. Glycerol has also been considered as a glucogenic supplement. Glycerol is absorbed or fermented to propionate, with safe dietary levels up to 10.8%. Optimizing nutrition of transitional dairy cows is key to reducing metabolic disorders and enhancing productivity. Further research is needed to balance starch sources and glucogenic additives for better metabolic health.
Material and Methods
Twenty-four multiparous Holstein cows (parity of 2.4 ± 0.4; BW of 647 ± 52 kg; mean ± SD) were used in a 2×2 factorial design, evaluating two factors: grain type (barley vs. corn) and glucogenic additive (GlycoPersia®: glycerol, monopropylene glycol, and Krebs cycle intermediates on a corn cob carrier) inclusion. The trial spanned 21 days pre- to 21 days post-calving. The experimental treatments were: 1) Barley-based without additive, 2) Barley-based with additive, 3) Corn-based without additive, 4) Corn-based with additive. Feed samples were collected weekly for dry matter determination. Daily milk yield was recorded, with weekly samples were analyzed for fat, protein, and lactose analysis. Rumen fluid was collected on day 21 postpartum, and analyzed for pH, NH3-N, and VFA parameters. Daily feed intake was recorded by weighing feed refusals each morning before fresh feed provision. The data were analyzed using SAS statistical software (version 9.4) by mixed procedure. The significant differences were analyzed by Tukey test at a 0.05%.
Results and discussion
In pre-calving experiments, glucogenic additives and starch sources had no significant effect on dry matter or nutrient intake. Conflicting results across studies may stem from grain type and additive differences affecting propionate production. Post-calving, grain type tended to affect dry matter intake, with barley-based diets showing the highest intake. This contradicts theories on propionate's negative intake effects. Some attribute higher intake to glycerol fermentation increasing butyric acid, enhancing rumen epithelium development and nutrient absorption. Discrepancies may relate to dosage, basal diet, glycerol form (liquid/solid), and purity. One study found no milk production difference between cracked wheat and ground corn in postpartum diets. Possible explanations include forage filler effects, fermentability differences, and delayed energy supply from starch. Corn provides more post-ruminal glucose, reduces propionate, and supplies more energy for milk production—yet results were inconsistent. Glucogenic additives can increase glucose for lactose and milk synthesis, but during the transition period, glucose is prioritized for immunity and tissues over the mammary gland, possibly explaining the lack of milk yield response.
In early lactation, high energy demand and low intake cause tissue mobilization, elevated NEFA, ketosis risk, and metabolic disorders. Glycerol can supply glucose, improve energy balance, and enhance health and milk yield. No significant differences were observed in digestibility of dry matter, organic matter, NDF, or starch. Finer grinding increases microbial access and ruminal fermentation but reduces intestinal passage. Variable digestibility effects of glucogenic additives may reflect differences in glycerol level, basal diet, and purity. More research is needed on optimal glycerol use across basal diets. Rumen pH is closely linked to rumination. Reduced rumination from grain substitution may lower pH. Glycerol largely escapes rumen fermentation (~75%), which may explain its lack of effect on volatile fatty acids.
Conclusions
This study evaluated grain type (corn vs. barley) and glucogenic additives during transition period in Holstein dairy cows. Results showed no significant effects on milk production, composition, prepartum DMI, rumen parameters, or nutrient digestibility. However, postpartum DMI was significantly higher with barley-based diets. The glucogenic additive showed no negative impacts. Findings suggest both grains can be used in transition diets, with barley potentially supporting better postpartum intake. Further research should investigate effects on health and reproductive indices.
Author Contributions
All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.
Data Availability Statement
Access to data is available via Hosseinkazemi75@ut.ac.ir.
Acknowledgements
The study was approved by the Ethics Committee of Tehran University of Agricultural Sciences and Natural Resources. The authors avoided data fabrication, falsification, plagiarism, and misconduct.
Conflict of interest
The author declares no conflict of interest.
