Effects of Source and Amount of Starch on Peripartum Diet, Milk Production and Blood Parameters of Holstein Heifers

Introduction Peripartum heifer feeding and management can have a substantial effect on her health and profitability. Suboptimal transition from late gestation to early lactation diet can decrease milk production, lactation persistency, and reproduction performance. Many nutritional innovations for the transition cow have been developed and deployed within the dairy industry. In the most previous studies, dietary treatments were imposed during the prepartum period and then the cows were fed a common diet during the post-calving period. In our study, we focused on the interaction of pre- and early post-partum diet of heifers. The aim of this study was to know the interaction effects between the prepartum diet starch degradability and postpartum diet starch amount in iso- energetic diets. Materials and Methods Forty heifers (BW, 600 ± 80 kg; BCS, 3.5± 0.25) were used in a completely randomized design and assigned randomly in to a 1 of 2 dietary treatments (ground barley vs. corn grain) in pre-partum period (24 ± 3 d relative to expected calving until calving) and then the cows in each group were randomly assigned in to a 1 of 2 lactation diets with high or low starch amount from + 1 to +28 d of calving. Then all the cows received the same high energy lactation diet until d 270. All diets were offered as total mixed ration (TMR) with similar crude protein and energy (low energy diets) content. Blood samples were taken at −20, +1 and +21 d relative to calving. Data were separately analyzed for pre- and post-partum periods by Proc Mixed of SAS with diet and time as fixed effect and animal nested in diet as random effect.Results and Discussion There were no significant differences in milk production and content except milk lactose in heifers fed prepartum diets during 28 days after calving. The prepartum barley diet increased milk lactose content compared to corn diet (P < 0.05). After calving, high starch diet increased milk lactose content compared to low starch diet (P < 0.05). There was an interaction between pre- and post-partum diet on milk production and fat and lactose content (P < 0.1) of heifers in 28 d post-partum and during 28 to 280 d of lactation. Our data showed the heifers had been fed corn diet in pre-partum and high starch diet in post-partum had lower milk production compared to other treatments. Heifers fed barley diet in pre-partum period had greater plasma triglyceride and cholesterol concentration compared with corn fed diet at calving day (P < 0.1). Heifers fed corn diet in pre-partum period had greater concentration of plasma, non-esterified fatty acid on d 21. Heifers fed high starch diet in post-partum period had greater concentration of plasma total protein and lower plasma beta hydroxy butyric acid than heifers fed low starch diet. Although there is scare data on peripartum heifers’ diet and metabolic status, it seems that acidosis prevalence in heifers increase immediately after calving. One study showed that cows fed low starch (15 % of DM) in pre-partum and high starch diet (27 % of DM) compared with low starch diet (21 % of DM) in post-partum with controlled energy diet had lower rumen pH and greater acute phase proteins. They found lower changes between starch concentration in pre- and post-partum diets and its ferment ability may decrease SARA occurring in the cows. There is a conflict between recent studies in recommendation of starch content in fresh cow diet. Conclusion The results of this study showed production and metabolic responses of fresh and lactating heifer to high or low starch diet depends on starch ferment ability in low energy prepartum diets. Heifers fed high or low fermentable starch diet in prepartm period had more smooth transition to high or low starch diet in postpartum period respectively. Transition from low fermentable starch diet to high starch diet can compromise milk production and health of heifers after calving.