Abstract
The objective of this study was to investigate the effect of cow genotype and parity on dry matter intake (DMI) and production efficiencies in pasture-based systems. Three dairy cow genotypes were evaluated over 3 yr; 40 Holstein-Friesian (HF), 40 Jersey × HF (JEX), and 40 Norwegian Red × JEX (3WAY) each year, with each genotype grazed in equal numbers on 1 of 4 grazing treatments in a 2 × 2 factorial arrangement of treatments [diploid or tetraploid perennial ryegrass (Lolium perenne L.) with or without white clover (Trifolium repens L.)]. A total of 208 individual cows were used during the experiment. The effect of parity (lactation 1, 2, and 3+) was also evaluated. Individual DMI was estimated 8 times during the study, 3 times in 2015 and in 2017, and twice in 2016, using the n-alkane technique. Days in milk at each DMI measurement period were 64, 110, and 189, corresponding to spring, summer, and autumn. Measures of milk production efficiency calculated were total DMI/100 kg of body weight (BW), milk solids (kg fat + protein; MSo)/100 kg of BW, solids-corrected milk (SCM)/100 kg of BW, and unité fourragère lait (net energy requirements for lactation equivalent of 1 kg of standard air-dry barley; UFL) available for standard (4.0% fat and 3.1% protein content) milk production after accounting for maintenance. During the DMI measurement periods HF had a greater milk yield (23.2 kg/cow per d) compared with JEX and 3WAY (22.0 and 21.9 kg/cow per d, respectively) but there was no difference in MSo yield. Holstein-Friesian and JEX, and JEX and 3WAY had similar DMI, but HF had greater total DMI than 3WAY (DMI was 17.2, 17.0, and 16.7 kg/cow per d for HF, JEX, and 3WAY, respectively). Jersey × Holstein-Friesian cows were the most efficient for total DMI/100 kg of BW, SCM/100 kg of BW, and MSo/100 kg of BW (3.63, 4.96, and 0.39 kg/kg of BW) compared with HF (3.36, 4.51, and 0.35 kg/kg of BW) and 3WAY (3.45, 4.63, and 0.37 kg/kg of BW), respectively. Unité fourragère lait available for standard milk production after accounting for maintenance was not different among genotypes. As expected, DMI differed significantly among parities with greater parity cows having higher DMI and subsequently higher milk and MSo yield. Although all 3 genotypes achieved high levels of DMI and production efficiency, JEX achieved the highest production efficiency. Some of the efficiency gains (SCM/100 kg of BW, MSo/100 kg of BW, and total DMI/100 kg of BW) achieved with JEX decreased when the third breed (Norwegian Red) was introduced.
Highlights
Within pasture-based grazing systems the efficient conversion of feed input into product is critical for economic profitability (Prendiville et al, 2009)
This leads to increased DMI per unit BW and greater production efficiencies for JEX cows compared with HF and make JEX cows uniquely suited for intensive grazing systems (Prendiville et al, 2009; Buckley et al, 2014; Coffey et al, 2017)
Our study indicates that 3-way cross of Norwegian Red × JEX (3WAY) had lower DMI, there was no disadvantage of 3WAY in terms of production efficiency compared with HF some of the efficiency gains achieved with JEX were reduced when a third breed (Norwegian Red) was introduced
Summary
Within pasture-based grazing systems the efficient conversion of feed input into product is critical for economic profitability (Prendiville et al, 2009). The suitability of JEX cows for pasture-based systems is due to their lower BW and greater gastrointestinal tract size relative to their BW compared with HF cows (Prendiville et al, 2009; Beecher et al, 2014). This leads to increased DMI per unit BW and greater production efficiencies for JEX cows compared with HF and make JEX cows uniquely suited for intensive grazing systems (Prendiville et al, 2009; Buckley et al, 2014; Coffey et al, 2017). There is a paucity of information regarding the effect of introducing a third genotype into a rotational crossing system on DMI and subsequent production efficiencies within pasture-based systems
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