Exploring the cause of reduced production responses to feeding corn-dried distillers in lactating dairy cows
Journal of Dairy Science Vol. 107 No. 7, 2024
This article from researchers from Ohio State University describes an experiment conducted to identify the factors that cause reduced production of cows fed a diet with high content of corn distillers grain with solubles (DDGS). The authors hypothesized that the factors could be high sulphur content in DDGS which may directly, via sulphur toxicity, or indirectly, via low dietary cation-anion difference (DCAD), cause reduced production [DCAD means dietary cation-anion difference and is an index of the relative balance between the principal cations (potassium and sodium) and the principal anions (chloride and sulphur) in the cow's diet]. They also hypothesized that the content of polyunsaturated fatty acids (PUFA) in DDGS could be another major factor. For the study, 60 lactating Holstein cows (15 primiparous and 45 multiparous) averaging 44 kilograms of milk at the beginning of the trial and an average of 123 days in milk were used. The treatments consisted of five different diets: one diet where soybean meal (SBM) was the main source of protein; a diet where 30% of SBM was replaced with DDGS; a diet where SBM was the main source of protein but extra sulphur was added to the diet to mimic the higher amount of sulphur in DDGS diets; a diet with SBM and added corn oil, to mimic the extra unsaturated fat in DDGS diets; and a diet with DDGS plus extra cations (sodium bicarbonate and potassium carbonate) to mimic the DCAD index of the SBM diet.
The authors provide some background information explaining that DDGS, the most common byproduct derived from ethanol production, can be an economical substitution for soybean meal in lactating diets. However, reduced production responses are somewhat consistent when cows were fed a diet with high DDGS (greater than 20% in dietary DM). Studies have associated the high level of polyunsaturated fatty acids in DDGS diets with reduced production. Still, in studies where low-fat DDGS was fed at 30% of the total dry matter of the diet, variable and reduced production responses have been observed, which suggests that other dietary factors within DDGS may be causing the reduced production responses. The authors indicate that the relatively high sulphur content of DDGS may be part of the problem. The new NASEM book recommends a dietary concentration of sulphur of around 0.15% to 0.2% of the diet dry matter, to reach maximum fibre digestibility. In diets with high amounts of DDGS, the total sulphur level of the diet can increase to 0.41%. Excess sulphur can cause direct and indirect negative effects on dairy cows, as an oversupply of sulphur can directly reduce rumen pH and fibre digestibility and act as a trace mineral antagonist. Indirectly, sulphur decreases DCAD; therefore, adding DDGS to a diet decreases DCAD due to the high sulphur concentration.
The study concluded that milkfat depression occurs when high DDGS are included in a lactating cow diet (30% of dietary DM). Low dietary cation-anion differences in addition to polyunsaturated fatty acids were likely the major factors that caused milkfat depression when the DDGS diet was fed. The high sulphur content of DDGS did not appear to have a direct effect on the reduced production responses observed with the DDGS diet. However, it did have an indirect effect, contributing to milkfat depression. Adding DDGS to a diet decreased DCAD, impairing the acid-base balance of cows, which was likely associated with milkfat depression observed in cows fed the DDGS diet. The authors suggest that increasing DCAD in a high-DDGS (greater than 20%) diet can be a useful strategy to lower feed costs and increase income over feed costs without reduced production responses, such as milkfat depression.
Effect of oxytocin use during colostrum harvest and the association of cow characteristics with colostrum yield and immunoglobulin G concentration in Holstein dairy cows
Journal of Dairy Science Vol. 107 No. 9, 2024
This article is from researchers from Cornell and Bern universities, aimed at determining the effect of oxytocin use during colostrum harvest on colostrum yield and IgG concentration in Holstein dairy cows on a commercial dairy in New York and to describe associations of cow characteristics with these outcomes. The treatments were a control group of cows that didn’t receive any oxytocin, one group that received 40 international units (IU) of oxytocin and a third group that received 20 IU of oxytocin. The oxytocin was administered 45 seconds plus or minus before unit attachment in a rotary parlour. Colostrum concentration of IgGs, dry matter and individual cow characteristics such as parity, calf sex, weight, dystocia score, stillbirth and milk production in week four of lactation and, for multiparous cows, dry period length and previous lactation dry-off linear somatic cell score (SCS) were collected.
The authors provide some background information, explaining that colostrum management continues to represent a crucial factor in dairy calf preweaning health. Transfer of passive immunity is the typical measure by which colostrum feeding practices are evaluated, and providing sufficient amounts of high-quality colostrum containing nutrients, growth factors, immunoglobulin and other bioactive factors results in high transfer of passive immunity. Excellent transfer of passive immunity (25 grams per litre serum IgG or greater, 9.4% serum Brix or greater) has been shown to decrease preweaning disease probability and mortality, as well as increase average daily gain (ADG) in heifer calves. They say that the first step to achieve these goals is to have enough high-quality colostrum available to feed newborn calves. Different factors have been studied to evaluate how to improve the quality and quantity of colostrum in recent years. Still, less is known about the harvesting effects on colostrum yield and quality. The authors mention a recent study that included 19 herds in New York, where 57.9% of producers reported using oxytocin regularly for colostrum harvest. Oxytocin plays a fundamental role in obtaining the milk or colostrum stored in the alveolar component of the udder, and endogenous release of this hormone is facilitated by tactile stimulation, such as suckling of the calf, hand milking or contact of the teat with the teat cup liner. However, despite the widespread industry use of oxytocin at first milking, data to support the routine use of exogenous oxytocin for colostrum harvest are sparse, and the anticipated positive effect on colostrum yield is not documented.
The authors mention some limitations of the study, mainly that the study was conducted during the summer and fall months, with no data obtained during the winter and spring months. It is known that colostrum yield is seasonal. Therefore, they say that studies investigating the effect of oxytocin administration on colostrum quantity and quality in the future could consider enrolling dairies with different management and milking systems in different regions over the course of a year to study the possible interaction of oxytocin use with season on colostrum yield and quality. They also explain the two doses of oxytocin they used (20 and 40 IU), saying that one is the oxytocin label dose for milk letdown (20 IU), and the other dose (40 IU) was based on the study farm’s current protocol for colostrum harvest. They recommend that future research investigating different doses, routes of administration and timing of injection is needed to complement the other available studies on this topic.
The study showed that primiparous animals milked for the first time in a rotary parlour had greater colostrum yield when given 40 IU of oxytocin intramuscularly immediately before milking. It also showed that oxytocin did not affect colostrum IgG, Brix percentage or dry matter in primiparous or multiparous animals. Lower parity, male sex of the calf, greater milk production at week four of lactation and longer length of dry period were associated with colostrum yield in multiparous cows, and greater parity and shorter dry period length were associated with increased concentration of IgG. Other studies also showed that both heifers and cows giving birth to male calves produced greater quantities of colostrum than those giving birth to females, and that calf birthweight was also associated with increased yield. The study also confirmed that the relationship of Brix percentage and IgG concentration is sufficiently accurate, and 20.6% and 23.9% Brix were identified as cut-offs to best classify colostrum at a level of less than 50 or 100 grams per litre of IgG in this herd.
This column brings you information regarding some of the research being done around the world and published in the Journal of Dairy Science. The objective is to bring to light areas of research that may have an immediate practical application on a dairy farm, as well as research that, even though it may not have a practical impact now, could be interesting for its future potential application. The idea is to give a brief overview of select research studies but not go into detail on each topic. Those interested in further in-depth reading can use the citations to find each study.
