Heat Stress Interactions with Protein Supplemental Fat, and Fungal Cultures

Abstract

Cows that were subjected to hot environmental temperatures yielded less milk (3.1 kg/d) on a diet high in CP (18.4%) and of medium degradability (65%) than on diets high in CP of low degradability (59%) or medium in CP (16.1%). The high CP diets were associated with decreased DMI and higher water intake, ruminal NH4, and blood urea. Negative effects on yield from the high CP, medium degradability diet were not observed at moderate temperatures. Evaporative cooling of cows in hot weather resulted in a greater milk yield response to low versus medium rumen-undegradabale protein diets than for uncooled cows. Evaporative cooling of cows also affected response to protein quality. For cooled cows, high Lys diet (soybean, fish, and blood meals) increased milk yield 14% over that with low Lys diet (corn gluten meal), but, for uncooled cows, a high Lys diet only increased yield by 9%. Percentage of CP, degradability, and protein quality had no effect on body temperatures or respiration rates of lactating cows. Some, but not other, reports showed that supplementation of 2 to 2.5% fat to diets fed under hot summer conditions resulted in less yield response than when fat was added at moderate temperatures. In several studies, fungal cultures (3 to 5 g/d) in the diet decreased body temperatures and respiration rates in hot, but not cool, weather. Increased milk yields and cellulose digestibility also resulted from dietary fungal cultures in some, but not all, trials. The mechanism of action exerted by fungal cultures on body temperature and respiration rate is unclear.

Efeito Da Utilização De Próbióticos Em Dietas Para Bovinos Nelore Terminados Em Confinamento.

“…No rúmen, leveduras vivas parecem elevar o consumo, por aumentarem a taxa de degradação da fibra, causando aumento expressivo no número de bactérias anaeróbias e maior estabilidade do ambiente ruminal, reduzindo-se as variações diurnas de pH, amônia e ácidos graxos voláteis (HUBER et al, 1994;WALLACE, 1994 Dietas com alta concentração energética, como a utilizada no presente experimento, podem promover queda do pH ruminal, o que deprime o crescimento de bactérias digestoras de fibra. Diante disso, a utilização de aditivos como o DBR ® Probiótico pode proporcionar a melhoria da digestibilidade da fração fibrosa da dieta.…”

The effects of sprinkler+fan, fish meal or dietary fat on milk yield and milk composition of dairy cows in mid lactation during summer

“…SF decreased rectal temperature and respiration rate in the present studies, but DMI, CPI, MEI were not improved by SF. Depending on the decrease in rectal temperature and respiration rate by SF, the reduced maintenance cost (Huber et al, 1994) of the cooled cows could be responsible from the limited improvement in milk yield. Similarly, DMI and nutrient supply for cooled and non-cooled cows may be, therefore, related to the ability of the cows suffering mild heat stress to compensate the decrease in feed intake by consuming more feed during cool time of the day.…”

Adaptation to hot climate and strategies to alleviate heat stress in livestock production

“…Reports of feeding excess rumen degradable protein during heat stress have been shown to decrease DMI and milk production (Huber et al, 1994). This reduction is because of the increase in maintenance requirements and decrease in energy being consumed.…”

“…This reduction is because of the increase in maintenance requirements and decrease in energy being consumed. To metabolize the excess protein, extra energy is required to convert protein into urea for excretion (Huber et al, 1994). An option to prevent this is to improve the quality of the protein being fed so that it may support increased milk levels in cows during heat stress (Huber et al, 1994).…”

“…To metabolize the excess protein, extra energy is required to convert protein into urea for excretion (Huber et al, 1994). An option to prevent this is to improve the quality of the protein being fed so that it may support increased milk levels in cows during heat stress (Huber et al, 1994). Researchers have found that supplementing with lysine led to increase in milk yields by 11% when fed to animals undergoing heat stress (Chen et al, 1993).…”