In vivo performance of Italian Heavy Draft Horse weanlings fed two protein levels and slaughtered at two ages.

This research investigates the impact of two different protein levels in the diet of Italian Heavy Draft Horse (IHDH) weanlings and the subsequent effects on in vivo performance, growth parameters, food intake, dressing percentage, and blood parameters. The study concludes that moderate dietary protein restriction doesn’t significantly impact the performance of the weanlings up to 18 months of age.

Research Details

• The study involved 41 weanlings grouped in 8 pens according to factors such as sex, age and body weight (BW). After an adjustment period, the horses were assigned to one of two diets with different Crude Protein (CP) levels (low protein, LP: 10.6 and 11.2% CP in Dry Matter, DM; and high protein, HP: 13.2 and 14.7% CP in DM).
• About half the animals were slaughtered at 13 months (end of first phase), and the remaining ones at 18 months (end of the second phase).
• Growth parameters, like body weight and withers height, were recorded and blood samples were taken to analyze markers such as plasma protein, urea, glucose, hepatic enzymes, and minerals. The horses were measured and scored every 3 weeks for fleshiness and Body Condition Score (BCS). Feed intake for each pen was recorded weekly, and feed samples were analyzed every 2 months.
• Body weight changes with time were modelled using fourth-degree Legendre polynomials within each phase.

Research Findings

• During the first phase, females fed a high-protein diet showed slightly different body weight trends than those fed a low-protein diet, but average daily gains (ADG) were the same. Males showed some minor variations in the shape of their growth curve, but ADG again was statistically uniform between the diets.
• In the second phase, there were no significant differences observed in either sexes’ growth parameters or ADG for the different diet types.
• However, the high-protein diet led to greater dry matter intake in both the first and second phase compared to the low-protein diet.
• There were no differences noted in horses’ body condition or ‘dressing percentage’ (carcass yield) at slaughter due to their diet.
• Plasma urea levels were higher in animals on the high-protein diet but were within the normal range for healthy horses.

Conclusion

• The study concluded that a moderate dietary protein restriction (approximately 3% of DM difference) made no detectable change to the in vivo performance of IHDH weanlings up to 13 or 18 months of age.