Evaluating the inclusion of alfalfa hay in diets fed to pregnant and non-lactating Holstein cows during the prepartum period
Thompson, Ahmerah Unique
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The study objectives were to determine the dry matter intake, urine pH, Ca concentration in blood, Ca output in urine, and incidence of hypocalcemia from pregnant, non-lactating dairy cows during the prepartum period consuming diets containing either grass hay (GH) or alfalfa hay (AH) with the inclusion of either calcium chloride (CL) or polyhalite mineral (PO). Eighty Holstein cows in their 2nd parity or greater were fed an experimental diet according to a 2 2 factorial arrangement of treatments during the prepartum period (21 d before calving). All diets had a dietary cation-anion difference (DCAD) below -190 mEq/kg/DM. Grass hay contained 7.5% CP, 74.9% NDF, 0.36% Ca, 0.02% Na, 1.88% K, 0.38% Cl, and 0.15% S. Alfalfa hay contained 19.6% CP, 45.6% NDF, 1.52% Ca, 0.16% Na, 2.5% K, 0.77% Cl, and 0.32% S. Cows consuming grass hay tended to consume more dry matter than cows consuming alfalfa hay (11.6 vs 10.8 kg/d), but dry matter intake (DMI) was not affected by the acidogenic products. Urine pH decreased below 6.5 for all diets and was greatest for cows consuming the GHPO diet. The concentration of calcium in plasma decreased significantly (P < 0.01) around calving but neither the hay type (P=0.86) nor the acidogenic product (P =0.81) affected it. Urinary calcium output was less for cows consuming the GHPO diet. Cows consuming diets containing alfalfa hay had a greater incidence of normocalcemia (37 and 40% for AHCL and AHPO, respectively) than cows consuming diets containing grass hay (20 and 25% for GHCL and GHPO, respectively). In conclusion, alfalfa hay can be included in prepartum diets without necessarily increasing the incidence of hypocalcemia, and the cation-anion difference of alfalfa hay is a determinant of whether it can be included in the prepartum diet.
General Audience Abstract
Hypocalcemia, low concentrations of calcium in the blood, is more prevalent during the transition from pregnancy to post-pregnancy and can be diagnosed through blood analysis or by observing physical symptoms. The dietary cation-anion difference (DCAD) is the acid-base regulation of the diet and has been used to prevent hypocalcemia during the pre-calving period. The objective of this study was to feed 2 types of hay and 2 types of acidogenic products (Grass Hay/Calcium Chloride, Grass Hay/POlyhalite, Alfalfa Hay/Calcium Chloride, and Alfalfa Hay/POlyhalite) to non-lactating cows in their pre-calving period and observe variables in relation to the incidence of periparturient hypocalcemia. The variables included plasma and urine calcium concentrations pre-calving (21 days) and post-calving (3 days), dry matter intake (DMI) during the pre-calving period, and urine pH. Cows decreased in their dry matter intake toward calving and consumed more grass hay than alfalfa hay (11.6 vs. 10.8 kg/d). All four diets were in a negative DCAD and successfully decreased urine pH for all cows. Calcium concentrations in plasma decreased around calving, but this was not affected by hay type or acidogenic product. Urinary calcium output was greatest in the GHCL-fed cows. The study resulted in further differentiation of cows with plasma calcium concentrations ≤ 5.5 mg/dL without physical symptoms and an animal with ≤ 5.5 mg/dL and a loss of muscle function. Only one cow had a loss of muscle function; however, 13 out of 79 cows had calcium concentrations that according to past research, should've resulted in this. Additionally, 44 out of 79 cows had calcium concentrations between 5.5 and 8.0 mg/dL at least once after calving. In conclusion, alfalfa can be included in pre-calving diets as long as the DCAD is negative.
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