Effects of molasses-based liquid feed supplementation to a high-straw dry cow diet on feed intake, health, and performance of dairy cows across the transition period
C. D. Havekes, Department of Animal Biosciences, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
T. F. Duffield, Department of Population Medicine, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
A. J. Carpenter, and T. J. DeVries * Department of Animal Biosciences, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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Introduction
In the weeks leading up to calving and in early lactation, various metabolic and behavioral challenges are imposed on the dairy cow (Drackley, 1999). One of the greatest stressors the cow will face is the sudden and dramatic demand for nutrients, which is commonly followed by a lag in DMI. As a result of not being able to consume sufficient DM to meet the high nutrient demand for milk production, cows fall into an energy- deficient state referred to as negative energy balance (Herdt, 2000). During periods of excessive negative energy balance, cows become more susceptible to developing metabolic disease such as ketosis, metritis, displaced abomasum, and mastitis (Ingvartsen, 2006).To minimize the severity of negative energy balance and thereby reduce the risk of metabolic disease, considerable research has focused on transition cow feeding strategies. Much recent research has focused on the dry cow diet, with a particular recent focus on the concept of controlling energy consumption during the dry period in an attempt to maintain BCS while promoting consistent intake (Dann et al., 2006; Janovick et al., 2011). From a physiological standpoint, these diets, which often contain a large proportion of straw, are successful in promoting energy balance by reducing body fat mobilization. From a feeding behavior standpoint, one limitation to these diets is that the high straw content may be filling and may also increase the risk of feed sorting. Recent research has focused on manipulating the physical characteristics of these drycow diets to promote consistency in intake and reduce sorting (Havekes et al., 2020a,b). That research demon- strated that using a smaller screen size (2.54-cm screen vs. 10.16-cm screen) to chop wheat straw in a high-straw (29%) dry diet increased DMI, reduced sorting, and improved metabolic health post-calving (Havekes et al., 2020a). Similarly, adding water to a high-straw dry diet (36% wheat straw), with straw chopped with a 2.54-cm screen, also increased DMI and reduced sorting during the dry period compared with the diet with no water added, and improved rumen pH around the time of calving (Havekes et al., 2020b). Despite reductions in sorting and improvements in DMI, approximately 5 to 10% refusals against the long forage particles still occurred in those studies, and cows still experienced a reduction in DMI as they approached calving. Thus, room still exists for improving consistency in intake of high-straw dry cow diets, both within and across days, as cows approach calving.
Conclusions
Supplementing high-straw dry cow diets with a molasses-based liquid feed was demonstrated to be an effective strategy for increasing DMI, reducing feed sorting, and promoting more consistent intake in the period leading up to calving. Furthermore, molasses supplementation during the dry period resulted in im- proved rumen health, as demonstrated by higher mean reticulorumen pH in the dry period and more consistent mean reticulorumen pH in the first week after calving.
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