Effects of reducing crude protein concentration in starter feed containing constant rumen undegradable protein on dairy calves performance.

This study aimed at investigating the effects of decreasing crude protein (CP) in diets with constant rumen undegradable protein (RUP) content on dry matter (DM) intake, growth, feed efficiency (FE) and blood parameters in calves in a randomized complete block design. Dietary treatments included: (a) a calf starter containing 200 g/kg CP (62 g/kg RUP, based on DM), (b) a starter containing 180 g/kg CP (65 g/kg RUP, based on DM) and (c) a starter containing 160 g/kg CP (65 g/kg RUP, based on DM). A total 42 newborn male and female Holstein calves were fed 8 L milk/day until day 45, after which they were weaned and continued the experiment until day 75. Solid feed intake and total DM intake were measured daily, and body weight and skeletal growth parameters including withers height and heart girth were recorded weekly. Blood samples were collected on days 45 and 75. Solid feed intake, total DM intake, weaning weight, average daily gain from birth to weaning and from birth to 75 days, final weight and FE were not affected by the experimental treatments. In addition, skeletal growth parameters were similar among groups. Glucose concentration was similar among treatments; however, calves fed the starter containing 160 g/kg CP had significantly lower plasma concentrations of albumin and urea nitrogen compared with those fed starters containing 180 and 200 g/kg CP. These results indicate that CP level in the calf starter could be decreased to 160 g/kg DM if RUP levels stay at 65 g/kg DM, without negatively affecting feed intake and calf performance.

Encapsulation of soybean meal with fats enriched in palmitic and stearic acids: effects on rumen-undegraded protein and in vitro intestinal digestibility.

Fat coating of soybean meal (SBM) can reduce its protein degradability in the rumen, but the encapsulation of SBM with palmitic (PA) and stearic acids (SA) has not yet been investigated, despite both fatty acids are common energy sources in dairy cow diets. This study aimed to evaluate the effects of applying a novel method, using either 400 or 500 g fat/kg (treatments FL40 and FL50, respectively), which was enriched in PA and SA at different ratios (100:0, 75:25, 50:50, 25:75 and 0:100), on physical and chemical characteristics, ruminal degradability, solubility and in vitro intestinal protein digestibility (IVIPD) of the obtained products. Encapsulation of SBM in fat resulted in greater mean particle size and lower bulk density and protein solubility than unprotected SBM (USBM). Treatment FL50 resulted in increased (p < 0.01) rumen-undegraded protein (RUP) compared to USBM. There were no differences in RUP of SBM when different PA: SA ratios were used. The mean RUP content of treatments FL40 and FL50 (306 and 349 g/kg, respectively) was greater compared to USBM (262 g/kg, p < 0.05), but lower than that for a standard heat-treated SBM (431 g/kg). Values of IVIPD did not differ among SBM, heat-treated SBM and FL40 and FL50 samples, all being greater than 97.8%. In conclusion, encapsulation of SBM with fats enriched in PA and SA proved to be effective in reducing protein solubility and increasing RUP without depressing protein digestibility in the intestine. For validation of the method, in vivo research to investigate the effects of these products on the production of dairy cows is warranted.