Feeding Management for Dry Cows

Dr. Timothy R. Johnson
Purdue NE Dairy Specialist

On many dairy farms nutrition of the dry cow receives less attention than it deserves. As Dr. Eastridge will address, nutritional management of the high producing fresh cow is the most critical time of nutrient demands. Lactational performance can also dramatically influenced by the diet  and nutritional management during the later stages of the previous lactation and dry period. Incidence of several metabolic diseases can also be influenced by or reduced by careful dry cow nutritional management.

Regaining of body tissue energy and protein stores during late lactation should occur and can be a challenge to control on a herd basis (Fronk et al., 1980). All herds have cows going dry at a range of body condition scores but field experience has shown that metabolic problems during the next lactation tend to be lowest in those herds which are able to minimize the variation in body condition of cows going dry. The common recommendation is to dry cows off at the desired body condition and maintain this condition score during the dry period. Some people advising producers have recommended further modification of body condition during the dry period. Often this occurs when a group of cows has gained excessive condition in late lactation due to a reproductive or nutritional problem. A study performed at the University of Guelph, Ontario, with Holstein cows, demonstrated the positive effects of a transition ration and hinted at negative effects on lactational performance when cows are forced to loose weight during the dry period (Table 1.) This data and our personal experiences should lead us to question the advisability of recommending drastic weight loss of dry cows during the dry period.

In the last several years a lot of attention has been directed towards the positive response many producers have experienced from instituting a dry cow transition ration containing 7 to 12 lbs grain/day and slightly higher protein concentrations. Increases in production of 1000 to 2000 lbs in the subsequent lactation have been reported ( Univ. of  Illinois, Dairy Report, 1992). The positive responses observed by using transition rations have commonly been attributed to an adaptation of the rumen microbial environment to a high grain lactation ration. Another possibility exists. Recent research at the University of Wisconsin (Skarr and Grummer, 1989) and at Michigan State University has demonstrated that liver accumulation of fat (fatty livers) can occur before calving. This can be easily understood if we consider the pregnant ewe as a model animal. Negative energy balance often occurs prior to lambing as rapid growth of the fetus (es) spur the irreversible loss of blood glucose prior to the time of full glucose demands for milk production. I propose that feeding a transition diet may give positive results in some cases by delaying the onset of hypoglycemia, fat mobilization and the metabolic problems that can result.

It has been proposed that addition of 12 grams niacin/day, known for its anti-lipolytic action, during the last two weeks of the dry cow diet may prevent excessive fat mobilization and fatty liver problems. The research of Skarr and Grummer, which involved intensive blood sampling and serial liver biopsy, has not shown a reduction in fatty infiltration of the liver by niacin treatment and did not support earlier work which suggested a dramatic improvement in prevention of ketosis by niacin supplementation (Illinois data).

Another area of research, which has provided more consistent and exciting results in dry cows, is the reduction of milk fever incidence achieved by addition of mineral salts changing the cation/anion balance of the dry cow ration. Some of the earliest work with prevention of milk fever by hormone treatment and more recently by modification of the dry cow ration cation/anion balance was performed by Ron Horst and Jessy Goff's group at USDA's National Animal Disease Center in Ames, Iowa. Some of these studies were done with Jersey cows fed a diet high in a calcium:phosphorus ratio (4:1) which should promote milk fever problems. Basically what we need to remember is that anions are acidogenic and promote release of calcium stored in the bone, or intestinal calcium absorption, while cations are alkalogenic and may reduce release of calcium from the bone or intentional absorption (Gaynor et al., 1989). Cation/anion balance of a ration can be calculated as meq (Na+K-Cl) per 100 gr ration DM. Ammonium chloride and ammonium sulfate are two anionic salts which are often used to adjust the anion/cation balance. It should be noted that in many of these studies more than 120 gr calcium/d was supplied. While in a research mode this is good designed to put control cows at a high risk of developing milk fever, simple reduction of the calcium content to 100 gr or less/d has been shown to elevate many post calving milk fever problems with out modification of the diets anion:cation ratio (Romo et al.).

Table 1. Effect of dry cow diet on milk production during the first 12 weeks of lactation.
Dry cow diet,
% of enery requirements
DMI, lbs. Milk, lbs. Fat, % Protein, %
64% 38.5 71.9 3.3 3.1
90% 39.6 72.8 3.5 3.1
150% 39.4 79.1 3.2 3.1
Boisclair et al. 1986 (8 cow/treatment)

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