High rumen degradable starch decreased goat milk fat via trans-10, cis-12 conjugated linoleic acid-mediated downregulation of lipogenesis genes, particularly, INSIG1

Abstract

Background: Starch is an important substance that supplies energy to ruminants. To provide sufficient energy for high-yielding dairy ruminants, they are typically fed starch-enriched diets. However, starch-enriched diets have been proven to increase the risk of milk fat depression (MFD) in dairy cows. The starch present in ruminant diets could be divided into rumen-degradable starch (RDS) and rumen escaped starch (RES) according to their different degradation sites (rumen or intestine). Goats and cows have different sensitivities to MFD. Data regarding the potential roles of RDS in milk fat synthesis in the mammary tissue of dairy goats and in regulating the occurrence of MFD are limited. Results: Eighteen Guanzhong dairy goats (day in milk = 185 ± 12 d) with similar parity, weight, and milk yield were selected and randomly assigned to one of three groups (n = 6), which were fed an LRDS diet (Low RDS = 20.52%), MRDS diet (Medium RDS = 22.15%), or HRDS diet (High RDS = 24.88%) for 5 weeks. Compared with that of the LRDS group, the milk fat contents in the MRDS and HRDS groups significantly decreased. The yields of short-, mediumand long-chain fatty acids decreased in the HRDS group. Furthermore, increased RDS significantly decreased ruminal B. fibrisolvens and Pseudobutyrivibrio abundances and increased the trans-10, cis-12 conjugated linoleic acid (CLA) and trans-10 C18:1 contents in the rumen fluid. A multiomics study revealed that the HRDS diet affected mammary lipid metabolism down-regulation of ACSS2, MVD, AGPS, SCD5, FADS2, CERCAM, SC5D, HSD17B7, HSD17B12, ATM, TP53RK, GDF1 and LOC102177400. Remarkably, the significant decrease of INSIG1, whose expression was depressed by trans-10, cis-12 CLA, could reduce the activity of SREBP and, consequently, downregulate the downstream gene expression of SREBF1. Conclusions: HRDS-induced goat MFD resulted from the downregulation of genes involved in lipogenesis, particularly, INSIG1. Specifically, even though the total starch content and the concentrate-to-fiber ratio were the same as those of the high-RDS diet, the low and medium RDS diets did not cause MFD in lactating goats.

A Metagenomic Insight Into the Hindgut Microbiota and Their Metabolites for Dairy Goats Fed Different Rumen Degradable Starch

“…Some investigations indicated that damage to the hindgut could also occur in association with ruminal acidosis ( Petri et al, 2019 ). In a previous study, we observed that the HRDS diet induced SARA in dairy goats ( Zheng et al, 2020 ). However, no difference in pH level was found in any segments of intestine we detected, and no animals had diarrhea or other digestive problems, suggesting that rumen acid accumulation and inflammation induced by systemic entry of endotoxins did not cause observable hindgut acidosis in the HRDS group.…”

Metagenomic Analyses of Microbial and Carbohydrate-Active Enzymes in the Rumen of Dairy Goats Fed Different Rumen Degradable Starch

“…In the current study, we conduct higher RDS by replacing corn with wheat. We have reported the effect of dietary RDS on milk production and found that high RDS diets significantly decreased the milk fat composition and yield in the dairy goats (Zheng et al, 2020). The milk fat synthesis in mammary gland can be affect by rumen metabolites that derived from rumen microorganisms, such as acetate, butyrate, trans fatty acids, and so on.…”

“…During the experimental period, the animals were fed separately twice daily at 0800 and 1630 h, and the water was available ad libitum. All goats were milked twice daily at 0800 and 1600 h. The feed intake and milk composition and yield for those goats have been published elsewhere (Zheng et al, 2020).…”

Ruminal Microbiota Determines the High-Fiber Utilization of Ruminants: Evidence from the Ruminal Microbiota Transplant

“…Expression of bacterial enzymes, such as CAZymes, could determine the utilization of nutrients and shape the intestinal microbiota ( 1 – 4 ). Ruminants exhibit strong abilities for fiber degradation and utilization by depending on the existence of numerous ruminal microorganisms to ferment structural carbohydrates, such as cellulose and hemicellulose, and transform them into volatile fatty acids (VFAs) absorbed by the host through the rumen wall for gluconeogenesis or by providing precursors for milk fat synthesis ( 5 – 7 ). Bacteria are the main components of rumen microorganisms.…”