Nutritional Strategies to Manipulate Milk Fat Synthesis and Fat Storage in Dairy Cows as a Means of Improving Animal Health, Production and Reproductive Performance at Various Stages of Lactation PDF Download

Author: Jillian Marie Havlin
Publisher:
ISBN: 9781321608830
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Languages : en
Pages :

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Book Description
Fat metabolism in dairy cows is highly variable over the course of lactation as well as among cows at a similar stage of lactation. Manipulating the ration of dairy cows is a useful tool for modifying fat metabolism, particularly how cows partition fat for milk fat synthesis versus storage as an energy source. Transition cows (i.e., cows approaching calving and beginning to lactate) experiences a negative energy balance (NEB), making them highly susceptible to a large range of post-partum health problems (e.g. ketosis, fatty liver, displaced abomasum) and reduced milk production. Therefore ability to abate severe NEB in transition cows through nutritional modifications would be a very efficacious. Ruminally-protected niacin (RPNi) is a lipolytic B-vitamin that may be able to block lipolysis during severe NEB, thereby reducing the incidence of ketosis and other post-partum diseases. To evaluate effects of feeding RPNi to post-partum cows, 997 fresh cows (i.e., cows between 1 and 28 days in milk (DIM)) were fed niacin, in the form of nicotinic acids (NA) for the first 14 to 28 DIM at one of 4 treatment levels (0, 3.5, 7, 14 g NA/cow/d). After 28 DIM cows were moved from fresh pens to early lactation pens where they remained until 150 DIM, and no RPNi was fed. At the lower dose of RPNi (i.e., 3.5 g NA) cows experienced an improvement in milk (P=0.10), fat (P=0.11), and energy yield (P=0.07) while on treatment, but when RPNi was removed from the ration milk (P=0.04), fat (P=0.10) and energy yields (P=0.06) decreased, compared to Control cows. Cows treated with low dose RPNi experienced a 16.3% decrease in prevalence of ketosis (P=0.06) and a 2.2 kg increase in dry matter (DM) intake (P=0.07) during the fresh period. The BCS of cows did not differ during the fresh period. Although the BCS of low dose RPNi cows decreased more (P=0.01) after moving to the high cow pen, BCS did not differ at 138 DIM. Conversely, cows treated with the higher dose PRNi (i.e., 14 g NA) experienced a decrease in milk (P=0.10), fat (P=0.11), and energy yields (P=0.07) while on treatment, but when RPNi treatment ended milk (P=0.04), fat (P=0.10), and milk energy (P=0.06) increased, with eventual convergence with Control cows. The high dose of RPNi did not affect ketosis prevalence, DM intake or BCS in the fresh pen. While Control cows began to regain BCS at the third sampling, high dose RPNi cows continued to lose BCS over the third (P=0.04) and fourth (P=0.10) BCS sampling in the high pens. The absence of change in BCS and blood NEFA levels indicates that the low dose of RPNi did not reduce lipolysis in adipose, but did aid in shifting the metabolism of NEFA away from ketogenesis towards the more efficient tricarboxylic acid (TCA) cycle, thereby reducing ketosis and increasing milk production yields. It is likely that high level RPNi feeding initially blocked lipolysis, but to an extent that cows were pushed in to very severe NEB, resulting in the decreased DM intake and maintained high ketosis prevalence. As feeding RPNi at any level had minimal effect on BCS and no effect on prevalence of NEB, no change in fertility parameters was as expected. After cows traverse the fresh pen, and progress through lactation, the metabolic focus shifts towards increasing and maintaining high productivity. One of the most common ways to improve milk production is by feeding fat to improve the NE density of the ration. Although not all dietary lipids have the same effects on fat utilization in the cow, particularly milk production and fat storage, two of the key components of dietary fat that have the greatest effect are the fat level of the ration and its saturation. To examine how these two parameters effect milk production metabolism, especially milk fat yield and BCS, three rations were fed to early lactation cows: A low fat control ration (LFC), and two isocaloric "high fat" rations, where one was high in polyunsaturated fatty acids (PUFA) from corn oil (HFU), and the second was high in saturated fat due to inclusion of a rumen-inert Ca-salt of fatty acids (HFS). Cows fed the HFS ration had increased milk, fat, protein, and milk energy yields (P