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This study aimed to evaluate the effect of replacing maize silage plus soybean meal with red clover silage (RCS) plus wheat on the fatty acid (FA) profile in the milk fat of cows. Forty-four lactating German Holstein cows were used in a 4 × 4 Latin square design with 21-d periods composed of 13 d of adaptation to diets followed by an 8-d sampling phase. Experimental diets offered as total mixed ration consisted of a constant forage-to-concentrate ratio (75:25) with target proportions of RCS to maize silage of 15:60 (RCS 15 ), 30:45 (RCS 30 ), 45:30 (RCS 45 ), and 60:15 (RCS 60 ) on a dry matter basis. Increasing the level of RCS in the diet was accompanied by a reduction of linoleic acid content in the diet and decreased linearly the proportions of linoleic acid in the milk up to 4%. Proportions of α-linolenic acid in milk increased 2-fold with RCS 60 compared with RCS 15 , which resulted from the linear increase in α-linolenic acid intake with incremental levels of RCS. Vaccenic acid in the milk fat was reduced by 24%. Rumenic acid, a conjugated linoleic acid (cis-9,trans-11 conjugated linoleic acid) considered to be a human health promoter, was also decreased by 22%. Reduced rumenic acid in the milk fat was probably due to a reduced amount of vaccenic acid produced in the rumen and, consequently, to the low amount of vaccenic acid to be desaturated to rumenic acid in the mammary gland by Δ 9 -desaturase. Oleic acid was enriched in the milk fat, although the dietary concentration of oleic acid decreased. Stearic acid proportions remained constant with increasing levels of RCS. The proportions of total polyunsaturated FA were increased by 12%, and the long-chain FA proportions increased linearly with increasing levels of RCS. Myristic acid was reduced linearly, but palmitic acid remained constant. Saturated FA was reduced linearly by 2%. Branched-chain FA, which are presumed to possess anticarcinogenic properties, were reduced to a small extent only (quadratic effect). We conclude that replacing maize silage with RCS appears to alter milk FA composition by reducing linoleic acid intake and ruminal biohydrogenation. Feeding RCS represents a strategy to increase intake of α-linolenic acid in dairy cows. However, because changes in the FA profile show positive as well as negative effects, no distinct conclusions can be drawn with regard to human health benefits., (Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The aim of the present study was to study the effect of exogenous amylase on postruminal disappearance of increasing amounts of corn starch being infused into the abomasum of heifers, and to detect a possible limitation of starch digestion in the small intestine. Four rumen-fistulated heifers (2 German Black Pied and 2 Jersey × German Black Pied) with an initial BW of 565 ± 6 kg were fed 5.6 kg DM/d of a diet targeted to contain only a negligible amount of starch. Animals were assigned randomly to a crossover trial with 2 experimental periods lasting 35 d each with 10 d of diet adaption followed by 25 d of sample collection. During the sampling period, each animal was abomasally infused with native corn starch at 5 levels (953, 1,213, 1,425, 1,733, and 1,993 g DM/d) each for a 5-d period with and without exogenous amylase, respectively. At days 6 to 10 the heifers received an abomasal infusion of starch in amounts of 724 g/d. Feces were sampled 4 times a day during the collection periods. Titanium dioxide was ruminally administered (10 g/d) to estimate fecal excretion. Purine bases in feces were determined and used as a marker for microbial N excretion. Fecal excretion of microbial N increased linearly with increasing level of starch infusion (P < 0.001), indicating a constant proportion of the infused starch being fermented in the hindgut. In contrast, the apparent digestibility of starch from the total postruminal tract decreased linearly from 90% to 80% (P < 0.001) when the intestinal starch supply increased from 1 to 2 kg/d. There is strong evidence based on the increasing starch excretion with feces and the indication of a constant proportion of infused starch being fermented in the hindgut for a decreasing efficiency of starch digestion in the small intestine with increasing intestinal supply. Amylase administration increased fecal excretion of butyrate (P = 0.04) and tended to increase isovalerate excretion (P = 0.06). However, amylase did not affect fecal excretion of microbial N or starch, suggesting that pancreatic amylase activity may not be the primarily limiting factor of postruminal starch digestion in heifers when corn starch is abomasally infused in amounts up to 2 kg/d. [ABSTRACT FROM AUTHOR]

The aim of the present study was to study the effect of exogenous amylase on postruminal disappearance of increasing amounts of corn starch being infused into the abomasum of heifers, and to detect a possible limitation of starch digestion in the small intestine. Four rumen-fistulated heifers (2 German Black Pied and 2 Jersey × German Black Pied) with an initial BW of 565 ± 6 kg were fed 5.6 kg DM/d of a diet targeted to contain only a negligible amount of starch. Animals were assigned randomly to a crossover trial with 2 experimental periods lasting 35 d each with 10 d of diet adaption followed by 25 d of sample collection. During the sampling period, each animal was abomasally infused with native corn starch at 5 levels (953, 1,213, 1,425, 1,733, and 1,993 g DM/d) each for a 5-d period with and without exogenous amylase, respectively. At days 6 to 10 the heifers received an abomasal infusion of starch in amounts of 724 g/d. Feces were sampled 4 times a day during the collection periods. Titanium dioxide was ruminally administered (10 g/d) to estimate fecal excretion. Purine bases in feces were determined and used as a marker for microbial N excretion. Fecal excretion of microbial N increased linearly with increasing level of starch infusion (P < 0.001), indicating a constant proportion of the infused starch being fermented in the hindgut. In contrast, the apparent digestibility of starch from the total postruminal tract decreased linearly from 90% to 80% (P < 0.001) when the intestinal starch supply increased from 1 to 2 kg/d. There is strong evidence based on the increasing starch excretion with feces and the indication of a constant proportion of infused starch being fermented in the hindgut for a decreasing efficiency of starch digestion in the small intestine with increasing intestinal supply. Amylase administration increased fecal excretion of butyrate (P = 0.04) and tended to increase isovalerate excretion (P = 0.06). However, amylase did not affect fecal excretion of microbial N or starch, suggesting that pancreatic amylase activity may not be the primarily limiting factor of postruminal starch digestion in heifers when corn starch is abomasally infused in amounts up to 2 kg/d. [ABSTRACT FROM AUTHOR]

The effect of an exogenous amylase on postruminal digestion of starch infused into the abomasum of cattle was studied. Four rumen-cannulated heifers were fed 5.5 kg DM/d of a diet without starch, and assigned randomly to a crossover design. The experiment consisted of 2 periods lasting 23 d each with 10 d for adaptation to the diet followed by 13 d of abomasal infusion and sample collection. During the first 3 d of each infusion phase, isotonic saline solution was infused (1 liter/h) for measurement of baseline values in feces, followed by daily infusions of 880 g DM corn starch (1 kg/10 liters of water) without or with the addition of 2% of amylase. Titanium dioxide (10 g/d) was ruminally administered for estimation of fecal excretion. Digestion of starch in small intestine was calculated as the difference between the amounts of infused starch, disappeared from hindgut and fecal excretion. The apparent disappearance of starch from the hindgut was estimated based on the increment of microbial nitrogen (N) excretion due to starch infusion (1 g microbial N/100 g fermented starch) compared to baseline values. The concentration of purine bases in feces was used to estimate excretion of microbial N. Microbial N excretion increased with starch infusion (P < 0.05) but was not influenced by amylase (P = 0.81). Starch disappearance from the small intestine was not improved by amylase (P = 0.78) and averaged 85%. Amylase affected neither blood concentration of glucose (P = 0.80) nor of insulin (P = 0.26), but glucagon was lower without (P < 0.0001) than with amylase. The infusion of starch increased fecal excretion of total VFA (acetate, propionate, and butyrate) by 53% (P < 0.05), which indicates increased carbohydrate fermentation in the hindgut and incomplete digestion of starch in the small intestine. However, the excretion of total VFA was not affected by amylase (P = 0.66). Lactate excretion was higher at the second day of starch infusion (P < 0.05) without than with amylase, which suggests lower flow of starch from the small intestine to the hindgut due to a possible effect of amylase addition in animals not adapted to starch digestion. However, lactate excretion returned near to baseline values within 2 d, which was probably due to increase of lactate-utilizing bacteria and the adaptation of the microbial population in the hindgut. Further studies with higher starch levels and addition of amylase are recommended. [ABSTRACT FROM AUTHOR]

Simple Summary: The purpose of this study is to assess the relationship of milk odd- and branched-chain fatty acids (OBCFA) with urinary purine derivates (PD) and estimated ruminal microbial crude protein (MCP). The correlations and regressions demonstrate that yields and concentrations of individual or total OBCFA are weakly related to urinary PD and are low to moderate markers of MCP synthesis. Nevertheless, milk OBCFA can still be seen as a promising method for predicting rumen function and microbial protein supply to the duodenum in dairy cows because MCP flow was not directly measured in this study but instead indirectly estimated probably comprising considerable deviations of the assumed values from the true ones. The aim of this study was to evaluate the relationship of milk odd- and branched-chain fatty acids (OBCFA) with urinary purine derivates and estimated ruminal microbial crude protein (MCP) synthesis. Forty-four lactating Holstein cows were used in a 4 × 4 Latin square design with 21-day periods comprised of a 13-day adaptation phase to diet followed by an 8-day sampling phase. Differences in estimated MCP yield and milk OBCFA composition were found by feeding total mixed rations containing forage (maize silage, MS; red clover silage, RCS) and concentrates (0.75:0.25) with targeted proportions of RCS to MS of 0.15:0.60, 0.30:0.45, 0.45:0.30, and 0.60:0.15 on a dry matter basis. The MCP was estimated from the total urinary purine derivate (PD) excretion (MCPPD) and intakes of metabolizable energy (MCPME) or digestible organic matter (MCPdOM). The Pearson correlations of individual OBCFA with urinary parameters (uric acid, allantoin, PD and nitrogen) were generally weak (r = −0.37 to 0.55). Yields of individual OBCFA correlated positively with MCPME and MCPdOM (r = 0.21 to 0.55). The prediction of urinary PD concentration was moderate (R2 = 0.64) when including the proportion of iso-C17:0. The prediction of total PD excretion was low (R2 = 0.21) with yields of iso-C15:0, anteiso-C17:0, and iso-C16:0. The prediction of MCPPD was high (R2 = 0.99) when including the iso-C16:0 and cis-9 C17:1 concentrations, while those of MCPME and MCPdOM were low (R2 = 0.37 and 0.36, respectively) when including yields of iso-C15:0, cis-9 C17:1, and iso-C18:0. The correlations and regression analyses demonstrate that the estimated MCP synthesis and urinary PD excretion can be only moderately predicted by yields and concentrations of individual or total OBCFA in cow's milk. However, milk OBCFA can still be seen as a promising, non-invasive method for predicting rumen function and microbial protein supply in dairy cows because MCP flow was not directly measured in this study but instead indirectly estimated probably comprising considerable deviations of the assumed values from the true ones. [ABSTRACT FROM AUTHOR]