Effects of encapsulated niacin on evaporative heat loss and body temperature in moderately heat-stressed lactating Holstein cows

Abstract

Twelve multiparous Holstein cows (145+/-9 d in milk) were randomly assigned to receive either 0 g/d of encapsulated niacin (control diet; C) or 12 g/d of encapsulated niacin (NI) and were exposed to thermoneutral (TN; 7 d) or heat stress (HS; 7 d) conditions in climate-controlled chambers. The temperature-humidity index during TN conditions never exceeded 72, whereas HS conditions consisted of a circadian temperature range in which the temperature-humidity index exceeded 72 for 12 h/d. Measures of thermal status obtained 4 times/d included respiration rate (RR); rectal temperature; surface temperature of both shaved and unshaved areas at the rump, shoulder, and tail head; vaginal temperature; and evaporative heat loss (EVHL) of the shoulder shaved and unshaved areas. Cows fed NI had increased free plasma niacin concentrations in both the TN and HS periods (1.70 vs. 1.47+/-0.17 microg/mL). Milk yield did not differ between dietary groups or periods. Dry matter intake was not affected by NI, but decreased (3%) for both C and NI treatments during HS. Water intake was increased during HS in both treatments (C: 40.4 vs. 57.7+/-0.8L/d for TN and HS, respectively; NI: 52.7 vs. 57.7+/-0.8 L/d for TN and HS, respectively). Average EVHL for shaved and unshaved skin for C and NI treatments was higher during HS (90.1 vs. 108.1 g/m(2) per hour) than TN (20.7 vs. 15.7+/-4.9 g/m(2) per hour). Between 1000 and 1600 h, mean EVHL for shaved and unshaved areas for NI fed cows was higher than for C fed cows (106.9 vs. 94.4+/-4.9 g/m(2) per hour). The NI fed cows had decreased rectal temperatures during HS compared with the C fed cows (38.17 vs. 38.34+/-0.07 degrees C) and had lower vaginal temperatures (38.0 vs. 38.4+/-0.02 degrees C). Calculated metabolic rate decreased during HS regardless of diet (50.25 and 49.70+/-0.48 kcal/kg of body weight per day for TN and HS, respectively). Feeding NI increased free plasma NI levels, increased EVHL during peak thermal load, and was associated with a small but detectable reduction in rectal and vaginal temperatures in lactating dairy cows experiencing a mild thermal load.

The Effect of Live Yeast Supplementation on Beef Cattle Performance: A Systematic Review and Meta-Analysis

“…Salvati et al (2015) observed that cows supplemented with yeast had a reduced heart rate and an increase in plasma niacin. The stimulus to dilatation of arterial blood vessels (Benyó, Gille, Bennett, Clausen, & Offermanns, 2006) acts with prostaglandin vascular receptors (Cheng et al, 2006) and increases the peripheral heat loss in dairy cattle (Zimbelman, Baumgard, & Collier, 2010). This might be the cause of this effect.…”

Future consequences and challenges for dairy cow production systems arising from climate change in Central Europe – a review

“…Niacin has been tested for its potential to reduce heat stress in dairy cows. In experiments conducted by Zimbelman et al (2010), cows fed 12 g encapsulated niacin per day showed decreased rectal and vaginal temperatures compared with controls during moderate thermal stress (THI .72 for 12 h/day). Similar results have been reported by Di Costanzo et al (1997).…”

Determining in vivo ruminal stability of three ruminally protected nutrients in lactating Jersey cows

“…Animal requirements for some nutrients may be much higher than previous estimates based upon concentrations in their diets and microbial biomass (Santschi et al, 2005). As most supplemental AA and water soluble vitamins have been shown to be extensively degraded in the rumen (Niehoff et al, 2009;Zimbelman et al, 2010), dietary supplementation without rumen protection is a very inefficient nutrient delivery mechanism to the intestinal absorptive site.…”