Effect of grain type and processing method on rumen fermentation and milk rumenic acid production

Abstract

It was hypothesized that differences in starch degradability account for observed differences in rumen vaccenic acid (t11-18:1) and milk rumenic acid (RA) concentrations. To test this hypothesis, starch degradability was varied through grain source and by processing. Eight Holstein cows in mid-lactation were assigned to two 4 3 4 Latin squares with four 21-day periods and four diets: dry rolled barley, ground barley, dry rolled corn and ground corn. Diets contained similar starch content and were supplemented with whole sunflower seed to provide similar total polyunsaturated fatty acid (PUFA) (18:2n-6 1 18:3n-3) contents. Forage/ concentrate ratios of all diets were 42 : 58. Rumen, plasma and milk samples were collected in the third week of each period. In situ degradation rates (%/h) for rolled corn, ground corn, rolled barley and ground barley were 5.4, 8.9, 17.0 and 19.4, respectively, for dry matter (DM) and 6.3, 10.8, 25.3 and 43.8, respectively, for starch. DM intakes were greater for corn-based diets (CBD) than for barley-based diets (BBD) with no difference between rolled and ground diets. Daily minimum rumen pH was less (5.2 v. 5.5) and pH duration ,5.8 (h/d) was greater (7.4 v. 4.3) for BBD than for CBD. Milk fat content and yield were less for BBD than for CBD with greater values observed for rolling compared with grinding. Variability in milk fat yield was strongly related (R 2 5 0.55; P , 0.01) to total starch intake (45%) and milk c9t11-CLA (10%) and none of the t-18:1 isomers or CLA isomers that are typically associated with milk fat depression entered the model. The concentrations (%) of t10-18:1 and t11-18:1 were greater for BBD than for CBD in rumen contents (t10-18:1, 3.5 v. 1.3; t11-18:1, 3.2 v. 1.9), plasma (t10-18:1, 1.2 v. 0.2; t11-18:1, 0.97 v. 0.58) and milk (t10-18:1, 3.8 v. 1.0; t11-18:1, 2.6 v. 1.7) despite greater total PUFA intakes for CBD. Milk RA concentration was greater for BBD than for CBD (1.46 v. 0.89) but was not influenced by the method of grain processing. This study clearly demonstrated that the milk content and profile of t-18:1 and CLA isomers were more strongly influenced by the source of grain starch (barley . corn) than by the method of grain processing indicating that factors inherent in the source of starch were responsible for the observed differences and these factors could not be modified by the processing methods used in this study.Keywords: grain processing, vaccenic acid, conjugated linoleic acid, corn, barley ImplicationsConjugated linoleic acid (CLA) is a component of milk fat with demonstrated health benefits. It was hypothesized that a difference in rate of starch digestion, varied through source of grain and processing method (rolling v. grinding), would influence rumen PUFA digestion and thus milk CLA. Concentrations of ruminal CLA precursors and milk CLA were greater for barley-based diets than corn-based diets but were not different between rolling and grinding indicating that factors inherent in the source of starch were responsible for the observed ...

Effect of grinding or pelleting high grain maize- or barley-based concentrates on rumen environment and microbiota of beef cattle

“…The greater proportions of 18:3n-3 and its BH intermediates (e.g., trans-13 + 14 and -15 18:1, and trans-9 cis-12 and trans-11 cis-15 18:2) in steers fed barley compared with those fed maize are consistent with previous results examining the effects of these cereal grains on the composition of rumen BH-derived FA (Mohammed et al, 2010;Toral et al, 2014). However, unlike reported in these studies, the starch source had no effect on the concentration of 18:2n-6 and total trans 18:1, which might exclude a general inhibition of BH by the lower ruminal pH values (Fuentes et al, 2011).…”

“…The meat and milk from ruminants contain a high proportion of saturated FA but also some BH intermediates, such as cis-9 trans-11 conjugated linoleic acid (CLA), with potentially health-promoting properties for consumers (Shingfield et al, 2008). Low pH has been shown to reduce BH of linoleic and linolenic acids in continuous culture of ruminal fluid (Fuentes et al, 2011) and a limited saturation of trans 18:1 intermediates to 18:0 because of a more acute rumen pH drop with barley than maize starch has been observed (Mohammed et al, 2010). Heating treatments may also restrain the BH of dietary FA, although results are not always consistent (e.g., Privé et al, 2010;TroegelerMeynadier et al, 2014).…”

Effect of concentrate supplementation on performance, ovarian response, and some biochemical profile of Malpura ewes

“…Ingredient composition of the concentrate mixture in the present study contained 97% barley. Barley is more fermentable in the rumen in comparison to other diets like corn (Granzin 2004;Lanzas et al 2007;Mohammed et al 2010) and therefore increased ruminal TVFA concentration (Khorasani et al 2001;Au et al 2010;Julien et al 2010) was observed. Higher concentration of TVFA production in group 2 is due to concentrate feeding, and this led to a decrease in ruminal pH both at 0 and 4 h of feeding concentrate.…”

Finishing strategies for steers based on pasture or silage plus grain and time on feed and their effects on beef quality

“…In this respect, wheat had a lower proportion of NDF (Table 1), and it is well documented that wheat has higher starch content than oats (Shewry, 2009). However, the pH of the rumen is primarily influenced by the fermentable carbohydrate in the diet, and the amount and source of starch and/or the rate of ruminal degradation of starch affects biohydrogenation in the rumen (Mohammed et al, 2010). Wheat grain reduces the ruminal pH and is used to induce subacute ruminal acidosis (SARA); subacute ruminal acidosis results in changes of the fermentation pattern in the rumen, with possible changes in the production of fatty acids (Enjalbert et al, 2008).…”