Abbas Rajaeerad

This study investigated the effects of low potassium diets with different levels of Ca compared to two diets low in dietary cation–anion difference (DCAD) fed prepartum as a strategy to prevent hypocalcemia on sorting behaviour, total tract digestibility, oxidative status and energy and protein metabolism of transition cows. Forty‐eight pregnant dairy cows were assigned to 4 treatment groups: Low Ca, low K (LCLK), High Ca, low K (HCLK), Supplementation with anionic mineral mixture (AMS) supplementation with SoyChlor (CAS). After parturition, all animals were fed a standard postpartum diet. Data were collected until 21 DIM. Prepartum urinary pH was significantly reduced by the low DCAD diets, while postpartum Ca homeostasis was affected by the HCLK ration. Feeding AMS induced sorting against particles 19 mm prepartum. In contrast, cows fed CAS showed an increase in selective consumption of fine particles and sorted against longer particles similar to the HCLK and LCLK groups. Postpartum sorting activity was not affected by the dietary treatments. After calving, apparent digestibility of NDF was significantly reduced in the HCLK group. Prepartum, we observed effects on serum concentrations of non‐esterified fatty acids were higher and insulin sensitivity was lower in the AMS group. Blood urea nitrogen (BUN) was decreased in cows fed the CAS ration. Postpartum, we found serum protein to be decreased with the low DCAD diets while BUN was decreased in the CAS group. The low DCAD rations increased prepartum serum malondialdehyde concentrations, while postpartum total antioxidant capacity was lower in the HCLK and the AMS group. From these data, we conclude that AMS decreased prepartum intake due to compromised palatability. Intermediate protein metabolism was affected by the low DCAD diets, while parameters of oxidative stress were probably affected by acid–base balance and Ca homeostasis.

This study investigated the effect of diets negative in dietary cation–anion difference (DCAD) or restricted in Ca fed prepartum to dairy cows for three weeks on colostrum yield and composition, and the health and growth performance of their calves. Thirty-six pregnant non-lactating Holstein-Friesian cows were randomly assigned to three isoenergetic diets: (1) low Ca: 0.24% Ca, DCAD: +86 mEq/kg; (2) high Ca: 1.23% Ca, DCAD: +95 mEq/kg; and (3) low DCAD: 1.28% Ca, DCAD: −115 mEq/kg (all dry matter (DM) basis). While colostrum quality was not affected, low Ca supply prepartum tended to increase the colostrum yield compared to high Ca (low Ca = 8.81 vs. high Ca = 5.39 kg). However, calves from cows fed low DCAD showed higher serum concentrations of K, lower body weight (BW), starter feed intake and average daily weight gain before weaning compared to low Ca and high Ca calves (53.12 vs. 57.68 and 57.32 kg) but BW was similar postweaning (d 70). In addition, calves from dams fed low DCAD were more likely to develop diarrhea and had increased number of days with abnormal fecal scores. Consequently, calves from low DCAD dams had to be treated more frequently.