Forage source (alfalfa hay vs wheat straw) and rumen undegradable to degradable protein ratio: Effects on growth performance, microbial protein yield, digestibility, blood metabolites, and behavior of Holstein dairy calves

Aim of the study: The effects forage source (alfalfa hay; AH vs. wheat straw; WS) with rumen undegradable to degradable protein ratio [low (LR) = 28:72; high (HR) 36:64] were evaluated in young dairy calves.Area Arak, Iran.Material and methods: Forty-eight 3-d old female Holstein calves (44.5 kg BW) allocated four treatments: (1) low dietary RUP:RDP (AH-LR); (2) (AH-HR); (3) WS (WS-LR); (4) (WS-HR), being RDP RUP proteins, respectively. weaned on d 53 experiment remained study until 73 age.Main results: average daily gain feed efficiency improved receiving HR diets compared LR during post-weaning period (p<0.05). fecal score (p=0.03) neutral detergent fiber digestibility (p=0.04) when fed diets. Feeding increased allantoin microbial yield, reduced blood urea nitrogen concentration Assessing interaction experimental factors resulted that greatest BW, wither height, beta-hydroxybutyrate, lowest urinary N observed WS-HR treatment (p<0.05).Research highlights: is recommendable due improvement efficiency.