@article {3672,
	title = {The effects of substituting autumn nitrogen fertiliser with gibberellic acid on feed supply and milk production},
	journal = {New Zealand Journal of Animal Science and Production},
	volume = {81},
	year = {2021},
	month = {01/2022},
	pages = {190-195},
	address = {Online},
	abstract = {The aim of this study was to investigate the use of gibberellic acid (GA) to improve feed supply and milk yield in late lactation. A grazing study at Lincoln used 36 lactating, mixed-age, Friesian-Jersey cross dairy cows balanced over three un-replicated treatments of perennial-ryegrass and white-clover pasture treated with nitrogen (N) fertiliser as urea (50 kg N/ha), GA as ProGibb{\textregistered} SG (8 g GA/ha) or untreated (Control). Treatments were applied in late March 2014 and grazed over 12 days in May. There was no effect of treatment on herbage pre-grazing pasture mass (2058{\textpm}6.9 kg DM/ha, P=0.20), clover (3.6{\textpm}0.86\%, P=0.53), ryegrass (88.0{\textpm}2.33\%, P=0.24) or crude protein (CP) content (17.8{\textpm}1.60\%, P=0.31). All milk yield components: 14.6{\textpm}0.40 L/day, 1.4{\textpm}0.09 kg MS/cow/day, 5.4{\textpm}0.33\% fat and 4.4{\textpm}0.21\% protein were similar among treatment groups (P=0.71, 0.14, 0.16 and 0.06, respectively). Although faecal-N content of cows on GA pasture (3.72\% N) was higher (P<0.001) than cows on N-fertilised pasture (3.45\% N) there was no treatment effect (P>0.05) on urinary-N content (0.4 {\textpm} 0.02\% N) or N excretion in milk (101{\textpm}4.4 g N/cow/d). The lack of response to GA or N fertiliser highlights the importance of timing of growth promotants for late lactation.

Keywords: perennial ryegrass; white clover; urea; growth promotants; dairy cow; milk production},
	issn = {1176-5283},
	author = {Miller ME and Edwards GR and Hague H and Bryant RH}
}
