Effects of partial or full replacement of soybean meal with urea or coated urea on intake, performance, and plasma urea concentrations in lactating dairy cows.

We expected mitigation of the hypophagic effects of urea (U) with a coated urea (CU) product that aimed to partially shift urea supply to the post-ruminal gastrointestinal tract. Ruminal release and post-ruminal digestibility of CU was evaluated in vitro, followed by a randomised complete block experiment (54 Holstein-Friesian cows; 177 ± 72 days in milk). Soybean meal (SBM) was partially (PR) or fully (FR) replaced on an isonitrogenous basis by beet pulp and U or CU.

Characterization of a model of hindgut acidosis in mid-lactation cows: A pilot study.

The objective of this pilot study was to generate data to support the development of an experimental model of hindgut acidosis to further understand its systemic consequences independently of rumen acidosis. Four ruminally fistulated multiparous Holstein cows (213 ± 11 d in milk) were subjected to 2 consecutive experimental periods (P1 and P2), separated by a 3-d washout. Experimental periods were 96 h long from the baseline to the final measurements but expanded over 5 calendar days (d 0-4).

Zinc, Copper, and Manganese Homeostasis and Potential Trace Metal Accumulation in Dairy Cows: Longitudinal Study from Late Lactation to Subsequent Mid-Lactation.

Background: Trace metals are supplemented in cattle to prevent nutrient deficiencies. Levels supplemented to mitigate worst-case basal supply and availability scenarios can, however, result in trace metal intakes far above the nutritional requirements of dairy cows with high feed intakes.

Objectives: We evaluated Zn, Mn, and Cu balance in dairy cows from late lactation through the subsequent mid-lactation, a period of 24 wk characterized by large changes in dry matter intake.

Dietary protein oscillation: effects on digestibility, nutrient balance and estimated microbial protein synthesis in lactating dairy cows.

Various studies with growing ruminants report increases in nitrogen use efficiency (NUE) when feeding oscillating (OS) dietary CP, whereas limited research with lactating dairy cows demonstrates a lack of improvement in NUE when feeding OS diets. We hypothesised that a total mixed ration (TMR) delivering OS CP (48-h phases of 134 and 171 g CP/kg DM, respectively) compared to a static CP TMR (ST; 152 g CP/kg DM) would result in similar or increased urinary purine derivative excretion (as a marker of microbial protein synthesis (MPS)) and greater urinary nitrogen excretion in lactating dairy cows. Responses in intake, production, apparent total tract digestibility (ATTD), nutrient balance, and estimated MPS were evaluated using faecal and urine collection in 12 multiparous cows (172 ± 39 d in milk) in a randomised complete block design, where total urinary output was estimated indirectly.

Digestive and metabolic efficiency of energy and nitrogen during lactation and the dry period in dairy cows.

The objective of this study was to characterize total-tract nutrient digestibility, energy balance, and N balance in the critical dietary and metabolic transitions of the lactation cycle. Twelve dairy cows were housed in tiestalls from 10 wk before to 16 wk after parturition. After 2 wk of adaptation to the facility and diet, digestibility of organic matter (OM), neutral detergent fiber (NDF), starch, and N were measured, and energy and N balances determined at weekly intervals by total collection of feces, urine, and milk over 48 h.

Blood calcium dynamics in cows receiving an aqueous calcium suspension for voluntary consumption or a calcium bolus following parturition.

The form of oral calcium (Ca) supplement and the Ca source influence Ca absorption dynamics resulting in different postpartum calcemia. The objective of this study was to investigate whether an oral Ca supplement (mainly CaCO3) offered for voluntary consumption would maintain or increase postpartum blood Ca to the same degree as a Ca bolus (mainly CaCl2) providing an equivalent dose of a Ca. A total of 72 Holstein cows were blocked by expected parturition date and parity.

Dietary protein oscillation: Effects on feed intake, lactation performance, and milk nitrogen efficiency in lactating dairy cows.

Limited research with growing ruminants indicates that oscillating (OS) dietary crude protein (CP) concentration may improve nitrogen use efficiency (NUE). Our aim was to determine if a total mixed ration (TMR) based on OS CP (48-h phases of 13.4% and 16.

Effect of a calcium-energy supplement drink at calving on lactation performance: Milk yield and composition, odds to reach a next lactation, and calving interval.

Supplementation of Ca products to cows after calving is common in calving protocols. This study evaluated the effect of a Ca-energy drink voluntarily consumed on milk yield and composition, odds to reach a next lactation, and calving interval. This prospective randomized study included a blinded placebo and was conducted in 10 commercial dairy farms that included 504 Holstein dairy cows.

Targeting the Hindgut to Improve Health and Performance in Cattle.

An adequate gastrointestinal barrier function is essential to preserve animal health and well-being. Suboptimal gut health results in the translocation of contents from the gastrointestinal lumen across the epithelium, inducing local and systemic inflammatory responses. Inflammation is characterized by high energetic and nutrient requirements, which diverts resources away from production.