Discipline: feed additive; Keywords: hindgut, prebiotic, milk fat.
The gastrointestinal tract is highly sensitive to a large number of internal variables in the lifecycle of dairy cows. The hindgut is susceptible to acidosis, much like the rumen, but due to a variety of physiological and structural differences, it is less capable of tolerating acidosis than the rumen, resulting in increased permeability to antagonistic compounds and repartitioning of energy to support an immune response. By improving gut integrity and function, less energy is repartitioned, thereby saving energy for productive purposes. Gluconic acid and its salts have previously shown prebiotic effects in the lower gut of non-ruminant animals, where they serve as a precursor for butyrate, but evidence in ruminants is limited. Therefore, in order to evaluate the response in the ruminant (in this instance the dairy cow), the objective of the study by Dr D.J. Seymour and colleagues was to evaluate changes in milk production, milk fatty acid composition, and faecal and blood parameters in lactating dairy cattle fed a hydrogenated fat-embedded calcium gluconate (HFCG) supplement designed to target the hindgut for calcium gluconate delivery. In addition, the effects of a compound feed processing method (i.e., incorporated into a mash or an extruded pellet) were tested to evaluate the effect of extrusion on product efficacy. The results were published in the Journal of Dairy Science, Volume 104 of 2021, page 7845 to 7855, the title being: Effects of supplemental calcium gluconate embedded in a hydrogenated fat matrix on lactation, digestive, and metabolic variables in dairy cattle.
Forty-five lactating Holstein cows at approximately 165 days in milk were used in a 3 × 3 Latin square design consisting of three 28-day periods, during which the cows were fed a basal ration mixed with three different compound feeds: a negative control in mash form containing no HFCG, or the HFCG supplement fed at a target rate of 16 g/day, delivered in either a mash or pelleted form.
Supplementation with the HFCG tended to increase yields of milk fat and fat- and energy-corrected milk. Total yields and concentrations of milk fatty acids with equal or more 18 carbons in length tended to increase in response to HFCG. Plasma non-esterified fatty acids and milk urea increased in HFCG treatments. No differences were observed in faecal pH or faecal concentrations of volatile fatty acids, with the exception of iso-butyrate, which decreased in HFCG-fed cows. Changes in milk fatty acid profile in response to HFCG supplementation suggest that increased milk fat yield was driven by increased incorporation of preformed fatty acids, supported by increased circulating non-esterified fatty acids. No major differences were observed between the two different processing methods used to incorporate the fat-embedded calcium gluconate supplement into the diet.
Future research investigating the mode of action of HFCG at the level of the hindgut epithelium is warranted, as measured faecal parameters showed no response to treatment, and therefore it was uncertain if there was an acidotic incidence.