Effect of high versus low dietary energy immediately prepartum on the performance of the dairy cow early in lactation

Abstract

In a 2 x 2 factorial arrangement, 12 Holstein dry cows during the last 2 wk of gestation were assigned to diets containing (a) Coastal Bermuda hay plus 2 kg concentrate, or (b) the same diet as in (a) plus supplemented corn increased to 1% of body weight. After parturition cows were alternately assigned to 2 complete rations differing only in the potassium content (.74 and 1.21%) for 28 d postpartum. Total dry matter and energy intakes prepartum were higher for cows fed the higher energy diet. A greater depression of intake during the last day of gestation was observed in the cows fed the higher energy diet. Prepartum diets had no effect on postpartum dry matter intake, milk yield, or milk mineral composition; however, cows fed the lower energy diet prepartum had a tendency to consume more feed and produce more milk than cows fed the higher energy diet. In Trial 2, 30 multiparous Holstein pregnant dry cows were assigned 3 wk prepartum to diets similar to the preliminary trial and after parturition were fed a complete ration of 45% concentrate, 10% Coastal Bermuda hay 15% whole cottonseed, and 30% corn silage for 28 d. As in the preliminary trial, prepartum total dry matter and energy intakes were higher for cows fed the higher energy diet. No significant difference sin body weights due to higher energy consumption prepartum were noted, except for wk 4 postpartum where cows fed the higher energy diet prepartum displayed higher body weights. A tendency was noted in which cows receiving higher energy prepartum exhibited higher standard deviations of body weight than cows fed the lower energy diets. Body condition scores were similar buy a tendency was evident for all cows to decrease in condition as they advanced in lactation. Cow receiving supplemental corn prepartum had higher postpartum dry matter intakes and milk yields than cows receiving hay and concentrate only. Blood serum analysis of minerals, various blood metabolites, as well as blood cell constituents and blood gases, showed no particular trend for either prepartum treatments and no carry-over effect into early lactation. In Trial 3, a six-unit continuous culture in vitro study compared 6 treatments: (a) hay; hay plus concentrate, with (b) and without (c) NaHCO3; hay plus concentrate and corn, with (d) and without (e) NaHCO3; and (f) a lactation complete ration, before and after switching to a complete ration. As the energy content of the diet increased, a significant decrease in pH was seen...