Effect of Protein Quality and Evaporative Cooling on Lactational Performance of Holstein Cows in Hot Weather

Abstract

Twenty-four Holstein cows in midlactation during summer in southern Arizona were fed diets supplemented with a combination of blood, fish, and soybean meals (high quality protein) or corn gluten meal (low quality protein). Diets were balanced for CP content and estimated ruminal protein degradability, but they differed in Lys concentration (.98 vs. .59% of DM). Milk yield for the 56-d trial was higher by 11% for cows fed high than for cows fed low quality protein and higher by 9% for cows receiving evaporative cooling plus shade than for cows receiving shade alone. Milk fat and protein yields also were greater for high than for low quality protein and for evaporatively cooled plus shade than for shade treatments. Intake of DM tended to be higher for cooled cows but was unaffected by protein source. Cooled cows had lower rectal temperatures (38.6 vs. 39.1 degrees C) and respiration rates (64 vs. 82/min) than noncooled cows. Interactions between protein quality and cooling method were not statistically significant; however, cooled cows fed high quality protein had higher milk yield than noncooled cows. Digestibility of DM was higher for the low than for the high quality diet, but CP digestibilities were not different. Cows fed supplemental protein of higher Lys content were more productive.

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

“…However, Taylor et al (1991) reported that the cooled cows fed on low degradable protein produced more milk than the noncooled cows on high degradable protein or than either the cooled or the non-cooled cows on high degradable protein when thermal stress was high. Similar trend was also reported by Chen et al (1993). The relatively high protein content in the diets and enough rumen undegradable protein supply from all diets may have masked probable FM effect and protein sources × SF interaction on milk yield and DMI in the present study.…”

“…The results reported in the literature with regard to the effect of FM on milk yield were inconsistent. Some studies (e.g., Chen et al, 1993) showed that FM improved milk yield due to supplying high amount of essential amino acids to the small intestine, but others (e.g., Santos et al, 1998) showed no positive effects. Furthermore, all diets used in the present studies were formulated with higher CP content than the requirements of the cows in mid lactation to alleviate the potential decrease in DMI during heat stress (Hassan and Roussel, 1975).…”

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

“…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). During periods of heat stress, the effects of decreased DMI and increased maintenance requirements resulted in the animal metabolizing more protein in order to meet energy requirements compared with cows under moderate temperature environments (Beede and Collier, 1986).…”

Determinação da digestibilidade intestinal de alimentos pela técnica de três estágios

“…Embora alimentos como o farelo de soja, casca de soja, farinha de carne e farinha de peixe tenham apresentado alta digestibilidade intestinal, alguns autores, citados por Cabral et al (2001), sugerem que a melhora no desempenho de vacas leiteiras de alta produção, adicionalmente à digestão intestinal, depende do perfil de aminoácidos dessas fontes, o qual deve complementar o perfil da proteína microbiana (CHEN et al, 1993;CLARK;KLUSMEYER;CAMERON, 1992;SCHWAB et al, 1992;BRODERICK, 1995). Figura 2.…”