Effect of Milk-Feeding Frequency and Calcium Gluconate Supplementation on Growth, Health, and Reproductive and Metabolic Features of Holstein Heifers at a Rearing Farm

Abstract

We compared the effects of milk-feeding in 288 Holstein calves (72 per group) which were fed twice (2F) or thrice (3F) daily, with or without the addition of hydrogenated fat-embedded calcium gluconate (G) supplemented in the starter food and in the daily diet up to the age of 9 months, on the calves' metabolism, growth, health, and reproductive efficiency up to first pregnancy. The calves received 6 L of milk replacer (130 g/L) and had ad libitum access to water and textured calf starter with or without gluconate. Gluconate supplementation promoted a "catch-up" in growth in supplemented calves compared to their counterparts that did not receive gluconate. Gluconate appeared to reduce animal metabolic stress during key events, such as weaning and transfer into open-door pens, reducing fructosamine (352.61 vs. 303.06 in 3FG and 3F, respectively; p = 0.028) and urea (3F revealed the highest values compared with the other three groups: 19.06 for 3F vs. 13.9 (2F), 13.7 (2FG), and 14.3 (3FG), respectively, p = 0.002) from weaning onwards. The feeding of dairy calves with milk replacer three rather than two times per day tended to be associated with better health from weaning to 4 months old; parameters such as ultrasound lung score and calf health score improved over time (p < 0.001). Thrice-daily feeding with milk replacer tended to reduce the number of artificial inseminations per pregnancy in heifers by 0.2 points (p = 0.092). We confirmed significant correlations between early health and growth parameters and reproductive efficiency and a positive correlation between body weight and average daily weight gain and the thickness of the back fat layer in young heifers (r = 0.245; p < 0.0001; r = 0.214; p < 0.0001 respectively). Our study was conducted on a commercial farm with reasonably effective animal management, so baseline welfare was likely satisfactory.

Keywords: dairy; first pregnancy; heifers; metabolites; stress; welfare.

Figure 1

Schematic description of the animal groups and procedures in this study. Analyses were conducted at weaning, transfer into open-door pens (ODPs), end of gluconate supplementation (E), and transfer into the reproductive herd (R). Animal age at different time points is given in parentheses. AI, artificial insemination; BF, backfat thickness as measured by ultrasonography; BW, body weight; HSc, health score; LSc, ultrasound lung score; MR, milk replacer; pre-W, preweaning period; post-W, postweaning period.

Figure 2

Energy-related metabolites of dairy calves at weaning (W), at the moment of transfer into open-door pens (ODPs), and at the end of gluconate supplementation (E): (a) β-hydroxybutyrate, (b) non-esterified fatty acids, (c) glucose, (d) lactate, and (e) fructosamine. Calves were randomized to be fed twice daily (2F) or three times a day (3F) with milk replacer, in both cases with ad libitum access to solid feed with or without the addition of calcium gluconate (G). Data are mean ± SD. a and b, significant differences among groups; α, significance of the effect of time in a mixed model; γ, significance of the effect of gluconate supplementation in a mixed model; β, significance of the effect of the interaction between time and gluconate; λ, significance of the effect of feeding times.

Figure 3

Lipid-related metabolites and urea of dairy calves at weaning (W), at the moment of transfer into open-door pens (ODPs), and at the end of gluconate supplementation (E): (a) triglycerides, (b) total cholesterol, (c) high-density lipoprotein cholesterol, (d) low-density lipoprotein cholesterol, and (e) urea. Data are mean ± SD. a, b, significant differences among groups; α, significance of the effect of time in a mixed model; ε, significance of the effect of the triple interaction of time, gluconate, and feeding frequency.

Figure 4

Growth parameters of dairy calves at the moment of weaning (W), at the moment of transfer into open-door pens (ODPs), at the end of gluconate supplementation (E), and at transfer into the reproductive herd (R) only in the case of body weight: (a) body weight in kg, (b) backfat thickness as measured by ultrasonography, and (c) average daily weight gain in three intervals. Calves were randomized to be fed twice daily (2F) or three times a day (3F) with milk replacer, in both cases with ad libitum access to solid feed with or without the addition of calcium gluconate (G). Data are mean ± SD. W-ODP: average daily weight gain from weaning to ODP transfer; ODP-E: average daily weight gain from ODP transfer to moment E; E-R: average daily weight gain from moment E to moment R. * in panel a indicates a significant difference between group 2FG and either group 2F or 3F at weaning (p < 0.05). a, b, c, d, significant differences among groups. α indicates a significant effect of time; γ, indicates a significant effect of gluconate supplementation.

Figure 5

Reproductive parameters of dairy heifers: (a) age at different moments of reproductive life, (b) artificial inseminations per pregnancy for first pregnancy, and (c) survival curve showing the hazard ratio associated with age at first pregnancy. Heifers were randomized to be fed twice daily (2F) or three times a day (3F) with milk replacer during lactation, in both cases with ad libitum access to solid feed with or without the addition of calcium gluconate (G). Data are mean ± SD. * in panel (b) indicates a tendency of difference between group 3FG and either group 2F, 3F and 2FG (p = 0.092).