Intake, efficiency, and feeding behavior characteristics of Holstein-Friesian cows of divergent Economic Breeding Index evaluated under contrasting pasture-based feeding treatments

摘要

The objective of the current study was to explore differencesin dry matter intake, intake capacity, productionefficiency, energy balance, and grazing behavior, of2 divergent genetic groups (GG) of lactating Holstein-Friesian, selected using the Irish Economic BreedingIndex (EBI). The GG were evaluated across 3 springcalving pasture-based feeding treatments (FT) over 3yr. The 2 divergent GG were (1) high EBI, representativeof the top 5% nationally (elite), and (2) EBI representativeof the national average (NA). In each year90 elite and 45 NA cows were randomly allocated to 1of 3 FT: control, lower grass allowance, and high concentrate.Although FT did affect animal performance,there were few notable incidences of GG × FT interaction.The elite cows expressed lower daily milk yield(−1 kg) compared with NA. Elite cows did, however,express higher daily concentrations of milk fat (+3.7g/kg) and protein (+2.1 g/kg) compared with NA.Daily yield of milk solids and net energy of lactation(NEL) was similar for both GG. Body weight (BW) wasgreater for NA (+13 kg) compared with elite, whereasmean body condition score was greater (+0.14) for elitecompared with NA. Intake did not differ significantlybetween GG. Intake capacity, expressed as total drymatter intake/100 kg of BW, was greater with elitecompared with NA. Production efficiency expressed asyield of milk solids per 100 kg of BW was greater withelite compared with NA, although milk solids/total drymatter intake did not differ between GG. Expressedas NEL as a proportion of net energy intake minus netenergy of maintenance (NE_L/NE_I – NE_M) and NEI/milksolids kg, indicated a slight reduction in the utilizationof ingested energy for milk production with elite comparedwith NA. This is, however, suggested as favorableas it manifested as a more positive energy balance withelite compared with NA and so is likely to enhancerobustness, increase longevity, and increase overall lifetimeefficiency. Noteworthy was a consistent numericaltrend toward more intense grazing activity with elitecompared with NA cows, exhibited in the numericallygreater grazing time (+19 min) and total number ofbites per day (+2,591).