The objective of this experiment was to investigate the effects of different levels of alfalfa hay (AH) and sodium propionate (Pro) added to starter diets of Holstein calves on growth performance, rumen fermentation characteristics, and rumen development. Forty-two male Holstein calves (40±2kg of birth weight) were used in a complete randomized design with a 3×2 factorial arrangement of treatments. Dietary treatments were as follows: (1) control = concentrate only; (2) Pro = concentrate with 5% sodium propionate [dry matter (DM) basis]; (3) 5% AH = concentrate + 5% alfalfa hay (DM basis); (4) 5% AH + Pro = concentrate + 5% alfalfa hay + 5% sodium propionate (DM basis); (5) 10% AH = concentrate + 10% alfalfa hay (DM basis); and (6) 10% AH + Pro = concentrate + 10% alfalfa hay + 5% sodium propionate (DM basis). All calves were housed in individual pens bedded with sawdust until 10wk of age. They were given ad libitum access to water and starter throughout the experiment and were fed 2L of milk twice daily. Dry matter intake was recorded daily and body weight weekly. Calves from the control, 10% AH, and 10% AH + Pro treatments were euthanized after wk 10, and rumen wall samples were collected. Feeding of forage was found to increase overall dry matter intake, average daily gain, and final weight; supplementing sodium propionate had no effect on these parameters. Calves consuming forage had lower feed efficiency than those on the Pro diet. Rumen fluid in calves consuming forage had higher pH and greater concentrations of total volatile fatty acids and molar acetate. Morphometric parameters of the rumen wall substantiated the effect of AH supplementation, as plaque formation decreased macroscopically. Overall, the interaction between forage and sodium propionate did not affect calf performance parameters measured at the end of the experiment. Furthermore, inclusion of AH in starter diets positively enhanced the growth performance of male Holstein calves and influenced both the macroscopic and microscopic appearances of the rumen wall. These benefits, however, were small when only sodium propionate was offered.

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The objective of this study was to investigate the effect of feeding different levels of ruminally protected methionine and choline on the incidence of physiological and metabolic disorders, production, and some of the reproductive indices of Holstein dairy cows. Forty Holstein dairy cows in their first and second lactation were used from 4-week pre-partum through 20-week post-partum and randomly assigned to receive one of the following treatments: 18 g/day of rumen-protected methionine (RPM), 60 g/day of rumen-protected choline (RPC), 18 g/day of RPM + 60 g/day of RPC, and neither supplement (control). The treatments significantly affected services per conception and open days of lactating dairy cows (p < 0.05), but did not affect significantly on days to first oestrus and number of pregnant cows. RPM + RPC-fed cows had the lowest open days, days to first oestrus and services per conception compared with other groups. The effect of treatments was significant on the incidence of metabolic and physiological problems except for foot/leg problems. Cows fed RPM+RPC had the lowest health problems compared with other groups (p < 0.05). Results indicate that the supplementation of RPM and RPC can improve reproductive performance and health status of dairy cows.

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Effects of live yeast supplementation on mid-lactation dairy cows performances, milk composition, rumen digestion and plasma metabolites during hot seasonFifty-six Holstein cows (36 multiparous and 20 primiparous), that averaged 145923 days postpartum, were used to investigate the supplementing of live yeast (LY) on productivity during hot summer conditions, from July until August 2010. Cows were fed a control diet with or without 4 g of LY (15 )10 9 CFU/g) per cow daily during a five-week period. Cows were milked three times a day and milk yield was recorded daily. Milk samples were also taken weekly for milk composition analysis. Blood samples and rumen liquor samples were taken in two subsequent days during the last week of the experiment. Milk production, 3.5% fat-corrected milk, and DM intake were similar for cows fed on both diets. A greater milk fat percentage was observed for cows fed LY compared to the control (PB0.05). However, milk urea nitrogen concentration in cows fed LY was lower compared to the control (PB0.01). Cows fed LY had greater blood glucose compared to the control (P B0.01). Blood urea nitrogen was lower for cows fed LY compared to the control (P B0.05). Non-esterified fatty acids, bhydroxybutyrate (BHB), triglyceride, total protein, and total cholesterol were similar for both diets. The apparent digestibility of NDF was greater for cows fed LY compared to the control (PB0.05). Rumen parameters such as pH, N-NH 3 , and VFAs were also similar for both treatments. The present results suggested that feeding LY to mid-lactation Holstein cows during heat stress can increase diet cell wall digestibility and improve milk fat percentage.