Ruminal fermentation and degradation, kinetic flow of the digesta and milk fatty acid composition of cows fed chopped elephantgrass supplemented with soybean oil

Abstract

Ruminal fermentation and degradation, kinetic flow of the digesta and milk fatty acid composition of cows fed chopped elephantgrass supplemented with soybean oil Fermentação e degradação ruminal, cinética de fluxo da digesta e perfil de ácidos graxos do leite de vacas alimentadas com capimelefante picado suplementado com óleo de soja AbstractThe aim of this study was to evaluate the ruminal parameters of fermentation and degradation, kinetic flow of rumen digesta, and milk fatty acid composition of cows fed 52% chopped elephantgrass-based diets containing 0.0% (control), 1.5%, 3.0% and 4.5% soybean oil (SO) on a dry matter (DM) basis. Four rumen-cannulated Holstein x Gyr dairy cows with an average milk production of 15.6 ± 3.0 kg day -1 and 90 ± 25 days in milk were allocated in a 4 x 4 Latin square design. The results were analyzed by mixed models. Significant differences were declared at P≤0.05, and P-values from 0.05 < P ≤ 0.10 were considered as a trend. The inclusion of SO in the diet had no effect on the ruminal pH or total volatile fatty acid concentration, but there was a quadratic effect on the ruminal ammonia nitrogen content and a trend for a linear reduction (P=0.07) in the molar proportion of rumen acetate. Linear reductions were also observed in the DM and neutral detergent fiber (NDF) effective degradabilities of elephantgrass forage, but the fluid and particulate passage rates in the rumen and the DM and NDF intakes were unchanged by SO inclusion in the diet. Milk production, protein and lactose contents and yields were unaltered by dietary SO levels. There were linear reductions in the milk fat and total solids contents, but there was no effect of dietary treatments on their yields. The inclusion of soybean oil in the diet of Holstein x Gyr cows fed chopped elephantgrass improved the nutritional quality of milk fat as a result of increased contents of oleic, rumenic and vaccenic acids, which are beneficial to human health, and a concomitant reduction in hypercholesterolemic saturated fatty acids such as lauric, myristic and palmitic acids. ResumoO objetivo deste estudo foi avaliar os parâmetros de fermentação e degradação ruminal, a cinética de fluxo da digesta, e o perfil de ácidos graxos (AG) do leite de vacas alimentadas com 52% de capimelefante picado e inclusão de 0,0 (controle), 1,5, 3,0 e 4,5% de óleo de soja (OS) na matéria seca (MS) da dieta. Foram utilizadas quatro vacas Holandês x Gir com 90 ± 25 dias em lactação, produzindo 15,6 ± 3,0 kg dia -1 de leite, canuladas no rúmen, e alocadas em delineamento Quadrado Latino 4 x 4. Os resultados foram analisados por modelos mistos. Efeitos foram considerados significativos quando P <0,05, enquanto valores de P entre 0,05 e 0,10 foram considerados indicativos de tendência. A inclusão de OS na dieta não alterou o pH do rúmen, nem a concentração total de ácidos graxos voláteis, mas promoveu efeito quadrático sobre a concentração de N amoniacal, e tendência de redução linear (P=0,07) sobre a proporção molar de acetato. Foram observadas reduções...

Milk fatty acid composition of Holstein x Gyr dairy cows fed sugarcane-based diets containing citrus pulp supplemented with sunflower oil

“…Milk samples for FA analyses were collected on day 16 of each LS period. The FA composition was analyzed by gas chromatography according to the procedures of Ribeiro et al (2018).…”

“…The nutritional quality of milk fat was evaluated by the atherogenicity (AI) and thrombogenicity (TI) indices, by the omega-6 and omega-3 FA ratio (ω-6/ω-3 FA ratio) and by the hypo-and hypercholesterolemic FA ratio (h/H FA ratio), calculated according to Ribeiro et al (2018).…”

“…Another factor that may have contributed to the reduction in de novo FA synthesis in the mammary gland is lower plasma concentrations of the precursors acetate and β-hydroxybutyrate (SHINGFIELD et al, 2010;BERNARD et al, 2018) resulting from possible inhibition by SO of ruminal fermentation by fibrolytic microbiota of the fibrous carbohydrates present in the diet (RIBEIRO et al, 2018). According to Durand et al (1988), the fermentation of citrus pulp mainly produces acetate.…”

“…The shift from the trans-11 to the trans-10 alternative BH pathway of linoleic acid is typical of diets supplemented with vegetable oils (JENKINS;HARVATINE, 2014;RIBEIRO et al, 2018). Comparing the control diet with the diet containing 4.5% SO, increases of 395% and 708% in the milk content of rumenic acid and trans-10, cis-12 CLA, respectively, were observed (Table 6), demonstrating that these two pathways of BH of linoleic acid were concomitantly performed by the ruminal microbiota.…”

“…However, SO supplementation promoted a linear increase (P=0.0055) in the ω-6/ω-3 FA ratio (Table 9). Ribeiro et al (2018): AI = atherogenicity index; TI = thrombogenicity index; h/H fatty acid ratio = hypo/ hypercholesterolemic fatty acids ratio; ω-6/ω-3 FA ratio = omega-6/omega-3 fatty acids ratio.…”