Production and marginal analysis of lactating cows subjected to dietary cation-anion balances

ABSTRACT. The objective of this study was to evaluate productive, nutritional, and economic traits in lactating cows on pasture fed diets with different cation-anion balances (DCAB). Ten lactating – Holstein × ¼ Dairy Gyr cows in the middle third of lactation, at an average age of 70 ± 4.6 months and an average body weight of 400 ± 55.2 kg, were distributed into five treatments in a 5 × 5 Latin square experimental design with two simultaneous squares. Treatments consisted of diets with DCAB of +237, +258, +294, +347, or +419 mEq dry matter (DM). No effects of intake were observed. There was no significant effect of DCAB on milk yield. The milk protein content was not influenced by the DCAB. Body condition score was not significantly affected by the DCAB. The apparent digestibilities of dry matter and nutrients (crude protein, neutral detergent fiber, ether extract, non-fibrous carbohydrates, and total digestible nutrients) were not affected by the DCAB. Marginal rate of return did not show significant differences. Under good conditions of pasture, forage availability, and quality associated with the lactation phases of the cows, all diets were efficient in milk production, dry matter intake, and digestibility. However, in economic terms, the most attractive DCAB was +237 mEq kg-1 DM.

摘要。本研究旨在评估放牧泌乳奶牛饲喂不同阴阳离子平衡（DCAB）日粮时的生产性能、营养特性与经济性状。选取10头荷斯坦×1/4吉尔乳用牛（Holstein × ¼ Dairy Gyr），处于泌乳中期，平均月龄为70±4.6个月，平均体重400±55.2 kg，采用5×5拉丁方试验设计，设置2个平行重复区组，分为5个处理组。各处理组日粮的阴阳离子平衡（DCAB）分别为+237、+258、+294、+347及+419 mEq/干物质（DM）。试验结果显示：采食量未受显著影响；DCAB对产奶量无显著作用；乳蛋白含量不受DCAB影响；体况评分亦未受DCAB显著影响；干物质及各营养物质（粗蛋白、中性洗涤纤维、乙醚提取物、非结构性碳水化合物及总可消化养分）的表观消化率均不受DCAB影响；边际收益率未表现出显著差异。在牧场条件良好、饲草可获得性与品质优良且匹配奶牛泌乳阶段的前提下，所有日粮在产奶性能、干物质采食量及消化率方面均表现高效。但从经济维度考量，最优阴阳离子平衡水平为+237 mEq·kg⁻¹ DM。