Performance, metabolic and hormonal responses of grazing Nellore cows to an energy-protein supplementation during the pre-partum phase

Abstract

Background: Supplementation programs for prepartum beef cows are usually adopted because the nutritional status of the cows upon calving is a main factor impacting reproductive performance of the next production cycle. This study evaluated the effects of 60-d pre-partum energy-protein supplementation on performance, metabolic and hormonal responses during the peripartum phase of grazing beef cows. Thirty-eight pregnant multiparous Nellore cows were assigned to a completely randomized design with two treatments: control (no supplement) and supplementation (1.5 kg of energy-protein per d with 30% crude protein, dry matter basis). Results: The supplemented cows had higher ADG pre-partum (P < 0.10), but postpartum ADG did not differ between treatments. Supplementation did not affect BCS and calf BW upon calving, on days 45 and 90, milk yield and composition (P > 0.10). No differences were found for forage intake and neutral detergent fiber digestibility (P > 0.10). The intake and digestibility of CP and OM increased in response to supplementation (P < 0.10). An interaction occurred between supplementation and peripartum days for BUN, βHB, T3 and T4, which had higher concentrations for supplemented cows at pre-partum period (P < 0.10). Concentration of others blood parameters significantly changed along peripartum days (P < 0.10). There was no difference in pregnancy rates and days from calving to conception between treatments (P > 0.10). Conclusions: Providing an energy and protein supplement to grazing Nellore cows over the last 60 d of gestation improved their pre-partum energy balance. However, no post-partum carryover effects were detected.

Effects of parity order on performance, metabolic, and hormonal parameters of grazing beef cows during pre-calving and lactation periods

“…A high blood glucose variance is not expected since homeostatic mechanisms control blood glucose concentration [ 15 ]. However, during parturition, cortisol and epinephrine levels increase, leading to glycogenolysis [ 16 ] and thus increased blood glucose [ 9 , 17 ]. In this study, nulliparous cows displayed higher glucose concentrations at calving, possibly due to more excitable temperament, stress, and fear experienced during calving than the other parities [ 18 ].…”

“…So, both cortisol and epinephrine, which are released during stress, can also influence lipid and muscle metabolism [ 16 , 19 ]. Previous experiments with Nellore cows have often shown high NEFA and glucose upon calving regardless of supplementation levels [ 9 , 17 ]. Besides acting as a potent lipolytic factor, epinephrine stimulates muscular glycogenolysis and amino acid output [ 20 ], which would also explain high levels of blood urea upon calving.…”

“…Cholesterol levels progressively increased on all postpartum days regardless of the category, a response to an increase in dry matter intake and homeorhetic changes of lactation [ 21 ]. Cholesterol levels also follow this pattern regardless of the nutritional plan in beef cows [ 9 , 22 ] due to the higher need for lipoproteins to carry triglycerides to the mammary gland. Especially during this period, HDL concentrations are higher than the other lipoproteins, possibly due to either increased synthesis or VLDL catabolism by mammary tissue [ 23 ].…”

“…Elevated levels of βHB concentration pre-calving are correlated to BCS loss, and thus to delayed luteal activity [ 5 , 33 ]. The levels of βHB of all parities are within the normal range for beef cows [ 9 , 34 ] and do not suggest a very severe energy deficit. Rather than that, it shows that nulliparous had worst energy balance pre-calving compared to other parities, which could impact future reproduction performance.…”

“…Metabolic profile evaluation is a tool widely used in ruminant nutrition as metabolic cues that relate nutrition to physiology [ 6 ]. It helps to accurately indicate the effects of a diet [ 7 , 8 ] or supplementation on animal metabolism, as well as understand homeorhetic states such as gestation and lactation [ 9 – 11 ] in which changes in metabolism occur to establish a new physiological state.…”