| Popis: |
Water footprint (WF) of livestock can be manipulated to improve water use efficiency. The dynamics of water use by Holstein nursing bull calves (HBC) is not very well stablished. The physiological and anatomical status of HBC permits for precise-diet manipulation aiming to decreasing voluntary water intake (WI); however, WI mitigation raises concerns about potential adverse effects on hydration and health. The goals herein involve investigation of the effects of two isoenergetic supplements top-dressed on ad libitum non-medicated milk-replacer (MR) on health, hydration, and WF of HBC. A total of 23 HBC weighing 94.67 ± 12.07 kg, 2 months old, were distributed in a completely randomized design receiving one of three diets for 67 days: control (CON; n = 7) received MR only, the lipid (FAT; n = 8) received MR supplemented with fish oil (3%), and the carbohydrate (CHO; n = 8) received corn starch (7%). All animals were offered mineral mix and water ad libitum, and 120 g daily dried brewer’s spent grains. Data were analyzed with the GLMMIX procedure of SAS 9.4 with diets as fixed effect. The WF was significantly decreased for the CHO group (P < 0.01). When WF values were adjusted by cold carcass weight (CCW), the CHO and FAT groups displayed a 100 L decrease in WF values compared to the CON. Though statistically significant differences were observed for Neutrophil count, lymphocyte count, and their ratio (NLR, as well as for total protein and fecal fluidity score (P < 0.05), the observed ranges were within healthy thresholds for HBC. Skin hydration was assessed through use of a skin moisture meter which resulted in the CHO group having significantly higher skin capacitance of 5.30 compared to CON = 3.76, and FAT= 3.99. These results evidence the possibility of increasing water use efficiency with precision diet formulation without adverse health and hydration effects. |
