Abstract
To explore whether or not the gossypol varied in cottonseed by-products affect rumen degradability and fermentation efficiency, an in vitro cumulative gas production experiment was applied with mixed rumen microorganism to compare rumen fermentation characteristics of whole cottonseed (WCS, n = 3 samples), cottonseed meal (CSM, n = 3 samples), and cottonseed hull (CSH, n = 2 samples). The five-replicate fermentation per sample per incubation time continuously lasted for 0.5, 1.5, 3, 6, 12, 24, 36, and 48 h with an automated gas production recording system. Regardless of distinct nutrient differences, the free gossypol level in these cottonseed by-products ranked: WCS > CSH > CSM. After 48 h of incubation, the in vitro dry matter degradability and ammonia N concentration ranked as: CSM > WCS > CSH. The cumulative gas production and total volatile fatty acid (VFA) levels in the culture fluids ranked: CSM > CSH > WCS, in which the average production rate ranked: CSM > WCS > CSH. Regarding the molar VFA pattern, WCS in comparison with CSH and CSM presented the lowest production of non-glucogenic acids (e.g., acetate) and exhibited the highest fermentation efficiency of energy from carbohydrates to VFAs. There was a significant negative correlation between the gossypol content and cumulative gas and total VFA production, suggesting that the greater gossypol in cottonseed by-products, the more detrimental effect occurred for rumen fermentation. In a brief, WCS exhibited mediocre rumen degradability and less microbial fermentation efficiency than CSH and CSM, depending on their gossypol levels.
Highlights
Cottonseed and its by-products are frequently used as an energy and protein feed resource in dairy cows, though they contain free gossypol (FG), a polyphenolic compound produced by cotton [1]
We investigated the rumen degradation characteristics and bacteria colonization of different cottonseeds and their by-products by in situ incubation; it revealed that the level of neutral detergent fiber, ether extract, and FG in cotton by-products were significantly related with the composition of the attached bacteria; the rumen fermentation efficiency of these cottonseed by-products was not determined due to the fluidity of the rumen environment [16]
The results of the present study revealed that there was a poor correlation between the gossypol content and ammonia N production, and we speculated that the promoting effect of protein in the current samples was greater than the inhibitory effect of gossypol on proteolytic bacteria, which may weaken the detrimental effect of gossypol on ammonia
Summary
Cottonseed and its by-products are frequently used as an energy and protein feed resource in dairy cows, though they contain free gossypol (FG), a polyphenolic compound produced by cotton [1]. Rumen microbes have been demonstrated to be capable of gossypol biodegradation ability [2–5], excessive intake of FG from rations will be toxic to animal [6–9]; many studies have shown that feed ruminants with cottonseed and its by-products containing a high content of gossypol would increase the incidence of abortion and somatic cell score in milk and decrease the quantity of viable ovarian follicles, semen quality, milk production, and milk protein [10–15]. All of these studies on cottonseed and its by-products were mainly based on their feeding effect on the production and reproduction performance of ruminants, but there is limited information about their gas production kinetics and rumen microbial fermentation characteristics. There has been no research conducted to investigate whether or not the gossypol varied in cottonseed by-products affect rumen degradability and fermentation efficiency
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