Effects of abomasally infused amylase and increasing amounts of corn starch on fecal excretion of starch, total and microbial nitrogen, and volatile fatty acids in heifers1.

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.

Prepartum supplementation of conjugated linoleic acids (CLA) increased milk energy output and decreased serum fatty acids and ß-hydroxybutyrate in early lactation dairy cows.

Prepartum supplementation with conjugated linoleic acid (CLA) may influence lipolysis and hyperketonemia in dairy cows. The objective of this study was to examine the effect of prepartum CLA supplementation on lactation performance and serum fatty acids (FA) and ß-hydroxybutyrate (BHB) in early lactation dairy cows, and secondarily on reproductive performance. Multiparous cows were enrolled in the study at 18 days prior to expected calving date, and randomly assigned 100 g/day of Lutrell Pure (BASF, Ludwigshafen, Germany; 75% FA), providing 10 g/day of each CLA isomer (trans-10 cis-12 and cis-9 trans-11 CLA) or equivalent amount of rumen inert fatty acids as control (78 g/day of Energy Booster 100; Milk Specialties Global, Eden Prairie, MN). Treatments were top dressed daily to individual cows from enrollment to calving and all cows were offered the same ration. Blood samples were collected on the first day of supplementation, 10 days prepartum, and 1, 7, 14, and 30 days postpartum. Hyperketonemia was defined as serum BHB ≥ 1.2 mM. Milk yield was recorded daily until 60 days postpartum and averaged weekly. Milk samples were obtained weekly for component analysis. Prepartum CLA supplementation tended to increase serum concentration of cis-9, trans-11 CLA and increased trans-10, cis-12 CLA prepartum. Cows supplemented with CLA had increased milk protein yield and tended to have increased milk fat yield and milk yield, which together resulted in greater energy content of milk. Cows supplemented with CLA had lower serum FA on day 1 and 7 postpartum and overall lower serum BHB postpartum, which resulted in decreased prevalence of hyperketonemia on day 14 postpartum. There were no differences in body condition score change, other health disorders, or reproductive outcomes by treatment. Together, these findings indicate that prepartum CLA supplementation may be a plausible strategy to positively influence postpartum performance.