Effects of Dietary Fiber on Intake, Milk Yield, and Digestion by Lactating Dairy Cows During Cool or Hot, Humid Weather

Abstract

Lactating cows were offered diets with increasing neutral detergent fiber concentrations to determine the effects on intake, milk yield and composition, blood hormones, and nutrient digestion during cool or hot weather conditions. Tifton 85 bermudagrass hay was substituted for corn silage so that the forage portion of diets were: 1) 40% corn silage (control), 2) 32.4% corn silage, 7.6% bermudagrass, 3) 24.8% corn silage, 15.2% bermudagrass, or 4) 17.2% corn silage, 22.8% bermudagrass (dry basis). Dietary neutral detergent fiber concentrations (% dry matter) were 30.2, 33.8, 37.7, and 42.0, respectively. Intake of dry matter declined with increasing dietary neutral detergent fiber during cool and hot periods, but intake adjusted for cool weather treatment differences did not change further during hot weather. Milk yield declined linearly with increasing neutral detergent fiber during cool weather and changed quadratically during hot weather. Milk temperature declined with increasing dietary neutral detergent fiber for the p.m. milking during the cool period and declined with increasing dietary neutral detergent fiber for the a.m. and p.m. milkings during the hot period. Digestibility of neutral detergent fiber improved and ruminal turnover of particulate digesta was increased with greater dietary neutral detergent fiber content. No dietary fiber level by hot weather interaction was observed, suggesting that total energy intake may have and a greater effect on milk yield than dietary fiber content during hot, humid weather.

Heat production, eating behavior and milk yield of lactating cows fed two rations differing in roughage content and digestibility under heat load conditions

“…These data are in accord with results from earlier studies that used soy hulls as corn silage replacer in TMR for lactating cows (Halachmi et al, 2004;Miron et al, 2003). However, other studies that employed starchy grain (Cummins, 1992;West et al, 1999) or fat supplementation (Chan et al, 1997;Huber et al, 1994;Serbester et al, 2005) used to increase the energy content of TMR, failed to enrich DMI, milk and milk protein production up to the levels obtained in the present study.…”

“…Under heat stress conditions, lactating cows tend to reduce their dry matter intake (DMI) and milk production (West et al, 1999). Voluntary DMI can decrease by as much as 6% when ambient temperatures rise above 30°C (Eastridge et al, 1998).…”

“…They suggested to reduce it to 12-15% of total mixed rations (TMRs) fed to high producing lactating cows that are exposed to hot weather conditions. Partial replacement of forage by starchy grain (Cummins, 1992;West et al, 1999) and addition of fat or protected fat to the diet (Chan et al, 1997;Huber et al, 1994;Serbester et al, 2005) have been tried as approaches to increase the energy consumption of cows under heat load conditions. These strategies have proven ineffective at increasing DMI, milk and milk fat production.…”

Effect of season on physiological, biochemical, hormonal, and oxidative stress parameters of indigenous sheep

“…Heat stress has been of major concern in reducing animal’s productivity in tropical, subtropical, and arid areas among the stressors [1]. Sweating, high respiration rate (RR), vasodilation with increased blood flow to skin surface, high rectal temperature, reduced metabolic rate, decreased dry matter intake, efficiency of feed utilization, and altered water metabolism are the physiological responses those are associated with negative impacts of heat stress on production and reproduction in sheep [2]. These physiological adjustments are essential to maintain normal body temperature and prevent hyperthermia [3-5].…”

The differences in heat stress resistance due to dairy cattle breed

“…The combination of high temperature and high relative humidity was proven to have the most detrimental effect through inducing heat stress in cows. Under heat stress conditions, lactating cows tend to reduce their dry matter intake (DMI) and milk production (West et al, 1999). Moreover, heat stress is associated with changes in milk composition, increase in somatic cell counts (SCC) and mastitis frequencies (Bouraoui et West, 2003).…”