Rumen fermentation characteristics and digestibility of cattle diets containing different whey:maize ratios

Impacts of whey protein on starch digestion in rumen and small intestine of steers

Four Korean native steers (511 ± 17.2 kg; 2 × 2 replicated crossover design) fitted with duodenal cannulas were used to investigate the influence of oral administration of soluble whey protein (WP; 82.29% crude protein) on ruminal fermentation, gastrointestinal (GI) hormone secretion in the blood, pancreatic α-amylase activity in the duodenum, and disappearance rate in each segment of the GI tract. Steers were orally fed the basal diet (control; TMR [total mixed ration] 9 kg/d) or the basal diet with enriched WP (400 g/d) for 14 days. The apparent crude protein disappearance rate in the rumen of the WP was higher than in control (p < 0.05). However, no difference between groups was observed in the apparent crude protein disappearance rate in the intestine and the apparent starch disappearance rates in the rumen, GI tract. The level of cholecystokinin, secretin, and ghrelin in serum and pancreatic α-amylase activity in the duodenum of the WP also did not change. The changes in the level of blood urea nitrogen related to protein metabolism were higher in the WP than in the control (p < 0.05). However, the levels of total protein, lipid, carbohydrate and mineral metabolites did not change. Consequently, we suggest that the oral administration of WP in steers assisted in ruminal fermentation due to the population increase of microbes in the rumen but did not improve the starch digestion rate in the small intestine because GI hormone secretion in the blood and pancreatic α-amylase activity did not change.

Efeito da adição de soro de leite sobre a digestibilidade aparente e os parâmetros sanguíneos de vacas secas

Avaliou-se o efeito da adição de soro de leite líquido à dieta sobre os parâmetros sanguíneos e sobre a digestibilidade aparente da matéria seca (DAMS), da proteína bruta (DAPB), da fibra em detergente neutro (DAFDN) e da fibra em detergente ácido (DAFDA) em 12 vacas Girolando, secas, que receberam feno de coastcross (Cynodon dactylon), suplementado com sal proteinado, e zero (controle), 15, 30 ou 45 litros de soro de leite/dia. A adição de soro na dieta afetou a DAMS e a DAPB (P<0,01) e não houve efeito sobre a DAFDN e a DAFDA. Quanto maior a quantidade de soro, maior o valor da DAMS e da DAPB. Os valores médios de glicose no plasma sanguíneo - 59,3; 64,0; 66,6 e 69.2mg/dL - variaram (P<0,01) entre os tratamentos, ajustando-se a regressões lineares positivas. A inclusão de soro afetou (P<0,01) a quantidade de ureia no sangue de maneira decrescente - 22,83; 20,17; 17,5 e 15,67. O soro de leite melhorou a eficiência de utilização de compostos nitrogenados no rúmen e pode ser utilizado para complementar suplementos proteicos com elevados teores de ureia.

Slow-Release Urea and Highly Fermentable Sugars in Diets Fed to Lactating Dairy Cows

This experiment was designed to test the inclusion of highly fermentable sugars (FS) in dairy rations and their interactions with a slow-release urea (SU) product. The FS are a blend of liquid coproducts from the corn milling and cheese industries, and the SU is calcium chloride urea. Eight multiparous and 4 primiparous Brown Swiss cows (117 +/- 46 d in milk) were blocked by parity and utilized in a multiple Latin square design. Basal diets were formulated for 16.6% crude protein and 1.55 Mcal/kg of net energy for lactation and contained 35% of dietary dry matter as corn silage, 15% alfalfa hay, 34% of a concentrate mix containing varying proportions of ground shelled corn and soybean meal, and 16% of a constant concentrate premix. The premix consisted of equal proportions of corn distillers grains, soybean hulls, expeller soybean meal, vitamins, and minerals across all diets. Diets contained either no supplemental FS (NFS) or FS (8.64% RationMate) and either no SU (NSU) or SU (0.61% Ruma Pro) in a 2 x 2 factorial arrangement of treatments. Feeding FS tended to decrease milk production compared with feeding NFS. Milk fat percentage was increased for cows fed FS compared with NFS. Feeding SU decreased dry matter intake and increased feed efficiency compared with cows fed NSU. Dietary treatment had no effect on energy-corrected milk, milk fat yield, milk protein percentage, or milk urea N. Feeding FS increased the molar proportion of ruminal butyrate and decreased the molar proportion of propionate; however, no other effects were observed on ruminal fermentation. No interactions between FS and SU were observed. It was concluded that the replacement of corn and soybean meal with dietary FS increased milk fat percentage and that the replacement of soybean meal with SU significantly improved feed efficiency.

Feeding Lactose to Increase Ruminal Butyrate and the Metabolic Status of Transition Dairy Cows

Twenty-four multiparous Holstein cows (775 +/- 24 kg body weight; 3.4 +/- 0.11 body condition score) were used in a randomized complete block design experiment to determine the impact of increased ruminal butyrate from the fermentation of lactose on metabolism and lactation. Dietary treatments were either a corn-based control diet (CON) or a diet containing lactose at 15.7% of diet dry matter (LAC). Experimental diets were fed from 21 d before expected calving through 21 d in milk (DIM). Blood was sampled at -21, -14, -7, -2, 2, 7, 14, and 21 DIM, rumen fluid at -21, -7, and 7 DIM, and liver tissue via biopsy at 7 and 14 DIM. Pre- and postpartum dry matter intake (DMI) through 28 DIM averaged 12.8 and 17.7 kg/d, respectively, and did not differ between treatments; however, cows fed LAC did not exhibit a prepartum decrease in DMI. Milk yield was unaffected by treatments and averaged 45.7 kg/d during the first 70 DIM. Plasma glucose, insulin, and non-esterified fatty acids were not affected by dietary treatments. Feeding LAC increased the ruminal proportion of butyrate both pre- (11.3 vs. 9.2 +/- 0.45%) and postpartum (13.0 vs. 10.3 +/- 0.67%). Likewise, circulating plasma beta-hydroxybutyrate was increased both pre- (6.1 vs. 4.2 +/- 0.31 mg/dL) and postpartum (14.6 vs. 8.34 +/- 1.7 mg/dL) when feeding LAC compared with CON. Liver lipid content was decreased (8.6. vs. 14.7 +/- 1.5% of wet weight) in cows fed LAC relative to those fed CON, whereas liver glycogen was not affected by dietary treatments. Feeding lactose to transition dairy cows increased the proportion of butyrate in the rumen and beta-hydroxybutyrate in plasma and decreased liver lipid but did not affect lactation performance.

Feeding lactose increases ruminal butyrate and plasma beta-hydroxybutyrate in lactating dairy cows

Ruminal fermentation of lactose increases molar proportions of butyrate, which is metabolized by the ruminal epithelium to beta-hydroxybutyrate (BHBA). To determine the effects of dietary whey, and specifically lactose, on concentrations of ruminal and blood volatile fatty acids (VFA) and blood BHBA, 8 Holstein and 4 Brown Swiss multiparous cows (210 +/- 33 d in milk) were blocked by breed and randomly assigned to one of three 4 x 4 Latin squares. Treatments were control (CON; 7.1% of dietary dry matter [DM] as cornstarch), liquid whey (WHEY; 9.4% of diet DM) containing 70% lactose on a DM basis, low lactose (LOLAC; 7.1% lactose), or high lactose (HILAC; 14.3% lactose). Diets contained 53% forage as corn silage, alfalfa hay, and grass hay (DM basis) and a corn and soybean meal-based concentrate. Average dietary percentage of crude protein and energy density (Mcal/kg net energy for lactation) were 16.8 and 1.47, respectively. Feeding lactose increased DM intake. Milk production and composition were not affected by diet with the exception of decreased urea nitrogen in milk from cows fed lactose. Greater proportions of ruminal propionate were observed in cows fed CON relative to those fed WHEY and LOLAC. Increasing dietary lactose increased proportions of ruminal butyrate and decreased acetate and branched-chain VFA. Concurrent with the increase in ruminal butyrate concentrations, there was an increase in plasma BHBA as lactose in the diet increased. Concentrations of VFA in plasma were not affected by diet with the exception of the branched-chain VFA, which were increased in cows fed LOLAC compared with WHEY. These data indicate lactose fermentation increases proportions of ruminal butyrate and plasma BHBA in lactating dairy cows; however, the observed increase in plasma BHBA is not sufficient to subject cows to ketosis.

Using artificial neural networks to model the urinary excretion of total and purine derivative nitrogen fractions in cows

A dataset of 177 individual nitrogen balances from dry and lactating cows was split in two independent groups: training dataset (n = 130) and challenge dataset (n = 47). The training dataset was used to develop multiple linear regressions (MLR) and artificial neural networks (ANN) aimed at predicting the urinary excretion of total (NURI) and that of purine derivative nitrogen (PDN). Input variables for the prediction of NURI were crude protein (CP) intake, effective degradability of non-protein dry matter (DM), neutral detergent fiber (NDF) content of the diet, live weight and milk yield. Live weight, total carbohydrate intake, the ratio of non-protein DM degraded to CP degraded and milk yield corrected for DM intake were entered to predict PDN. The regression between predicted and observed values for the training dataset showed a better statistical accuracy of ANN than did MLR models, especially for PDN. The evaluation of the two models on the challenge dataset showed similar determination coefficients, either when predicting total nitrogen excretion (0.623 and 0.614 for ANN and MLR, respectively) or PDN (0.688 and 0.666, for ANN and MLR, respectively). Moreover, both approaches were affected by a tendency to under-predict both targets at high levels of NURI and PDN. However, with the ANN approach, it is possible to study the response of the model to modifications of individual inputs by the so-called response analysis. This unique feature could be used to study the effect of different physiological situations as well as providing hypotheses for additional research.