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Titolo:
Reproductive performance in Holstein-Friesian cows in relation to genetic merit and level of feeding when grazing pasture
Autore:
Fulkerson, WJ; Wilkins, J; Dobos, RC; Hough, GM; Goddard, ME; Davison, T;
Indirizzi:
Univ Sydney, Camden, NSW 2570, Australia Univ Sydney Camden NSW Australia2570 Sydney, Camden, NSW 2570, Australia Agr Res Inst, Wagga Wagga, NSW 2650, Australia Agr Res Inst Wagga Wagga NSW Australia 2650 ga Wagga, NSW 2650, Australia NSW Agr, Armidale, NSW 2351, Australia NSW Agr Armidale NSW Australia 2351 SW Agr, Armidale, NSW 2351, Australia Univ Melbourne, Dairy Res & Dev Corp, Melbourne, Vic 3000, Australia Univ Melbourne Melbourne Vic Australia 3000 elbourne, Vic 3000, Australia
Titolo Testata:
ANIMAL SCIENCE
, volume: 73, anno: 2001,
parte:, 3
pagine: 397 - 406
SICI:
1357-7298(200112)73:<397:RPIHCI>2.0.ZU;2-M
Fonte:
ISI
Lingua:
ENG
Soggetto:
DAIRY-COWS; MILK-YIELD; FERTILITY; CATTLE; LACTATION; CONCEPTION; EFFICIENCY; SELECTION; GENOTYPE; WEIGHT;
Keywords:
concentrates; cows; genetic merit; Holstein-Friesian; reproduction;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Citazioni:
37
Recensione:
Indirizzi per estratti:
Indirizzo: Fulkerson, WJ Univ Sydney, Camden, NSW 2570, Australia Univ Sydney CamdenNSW Australia 2570 , NSW 2570, Australia
Citazione:
W.J. Fulkerson et al., "Reproductive performance in Holstein-Friesian cows in relation to genetic merit and level of feeding when grazing pasture", ANIM SCI, 73, 2001, pp. 397-406

Abstract

One hundred and eight Holstein-Friesian cows in six herds were run on six separate farmlets over a 5-year period from 1995 to 1999 at Wollongbar Agricultural Institute, on the subtropical north coast of New South Wales, Australia. Three of the herds comprised high genetic merit (HGM) cows - Australian breeding value (ABV) of +49.1 kg for milk fat (F) plus protein (Pr) andthree herds comprised low genetic merit (LGM) cows-ABV of 2.3 kg. Within genetic merit groupings, one herd was given 0(.)34 t (l), one herd was given0(.)84 t (m) and one herd 1(.)71 t (h), of concentrate per cow per lactation. Within each genetic merit group, cows were matched for milk yield and live weight, and over all groups for time of calving and age at the commencement of the study. The 30 paddocks within each farmlet were matched betweenfarmlets for pasture type and pasture growth rate and soil fertility. Halfthe cows within each herd calved over a 3-Pnonth period in spring and the other half in autumn. Strict management criteria ensured that there was no bias towards particular treatment groups. HGM cows were 'open' (days from calving to conception) for 8 days longer than the LGM cows (99 v. 91 days). The lHGM cows took 11 days longer to commence luteal phase activity and 21 days longer to first observed oestrus post calving than hLGM cows (P < 0.001), with the other groups being intermediate. After 24 days of mating, 22% of lHGM cows were pregnant, and this was lessthan half of the rate of the best herd-mLGM. After 9 weeks of mating, the chances of an LGM cow being pregnant was 87% greater than an HGM cow. After12 weeks of mating, 70% of lHGM cows were pregnant compared with a mean pregnancy rate of 87% for the LGM cows. The number of cows treated for abnormal ovarian activity (anoestrus, cystic) was highest (P < 0.001) in the HGM herds given 'l' and 'm' levels of concentrate compared with the remaining herds (0(.)24 v. 0(.)12 treatments percow mated, respectively). There was a significant positive relationship between live-weight change from 4 weeks before, to the start of, the mating period and the chances of acow being pregnant at 24 days (P < 0(.)05) and at 6 and 9 weeks after the commencement of mating. There was a significant negative relationship (P < 0.001) between the change in daily F plus Pr yield,from the start to 4 weeks after mating began, and pregnancy rate at 9 weeks. The change in F plus Pr yield was +63 g/day for cows pregnant at nine weeks as opposed to +154 g/day for cows not pregnant. The results of the present study indicate that the reproductive performance of HGM cows, with a mean of 61% North American (NA) genes, is lower than LGM cows (22% NA genes) under a predominantly pasture-based system of farming. The influence on reproduction was possibly due to genes favouring partitioning of energy to milk, yield rather than body-condition maintenance in the HGM cows and when food intake was inadequate, then being more willing to use body reserves. These reproductive problems may be reduced by more intensive reproductive management. However, such practices are costly and time consuming, Another approach may be to ensure that live-weight loss over the mating period is minimized by strategic supplementary feeding.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 22/09/20 alle ore 17:23:13