Abstract:
Proc. Aust. Soc. Anim. Prod. 1996 Vol. 2 I EFFECTS OF DRY SEASON AND WET SEASON SUPPLEMENTATION ON FERTILITY OF Bos indicus CROSS COWS R.M. DIXON A, I.K. PORCHA, M. D' OCCHIOB and G. FORDYCE * Swan's Lagoon Research Station, Millaroo, Ayr, Qld 4807 * Tropical Beef Centre, Rockhampton, Qld 4702 Supplements providing principally inorganic N and/or P are often fed to breeder cows in the harsher environments of northern Australia to reduce breeder mortality and increase productivity (McCosker and Winks 1994). However, the responses to such supplements fed at various times of the year are not well understood. The present experiment examined the liveweight (LW) and fertility responses of Bos indicus cross breeders to dry lick supplements fed during the dry season (DS) and/or during the later part of the wet season (WS). First-calf (FCC) and second-calf (SCC) Bos indicus x Shorthorn females were grazed in 8 x 100 ha paddocks at Swan' Lagoon from June 1994 until weaning in May 1995. The animals calved between late s October 1994 and mid-January 1995, and were mated from December 1994 to April 1995. Four treatments were imposed in a replicated 2x2 factorial design consisting of dry lick supplements fed ad libitum during the DS from July to November 1994, and/or during the late WS from March to May 1995. DS supplements contained 32% cottonseed meal, 27% urea, 18% salt, 14% calcium phosphates and 9% ammonium sulphate. WS supplements contained 33% cottonseed meal, 30% salt, 21% calcium phosphates, 15% urea and 1% sulphur. Measurements were made each 6-8 weeks of LW and body condition score (CS). Pregnancy status and time of conception were determined by rectal palpation. Data were analysed for main effects and interaction effects by AOV. Table 1. LW change (kg) from June 1994 to the early wet season (January- 1995) or weaning (May 1995), and -. pregnancy rate at weaning (%) for first-calf (FCC) (n 139) and second-calf (SCC) (n 45) cows not supplemented (Con), fed supplements only during the wet season (WS), only during the dry season (DS), or during both the dry and wet seasons (DS+WS) A In June 1994 FCC were 408 (SEM f 3) kg and CS 7.2 (SEM k O.l), while SCC were 350 (SEM + 7) kg and CS 5.2 (SEM f 0.1). Intake of DS supplement averaged 175 g/h.day, and intake of WS supplement averaged 116 g/h.day. On average DS supplement reduced LW loss of FCC from 120 kg to 95 kg, and LW loss of SCC from 85 kg to 49 kg (Table 1; PcO.01). WS supplement tended (P>O.O5) to increase LW gain from 19 kg to 29 kg. DS supplement increased pregnancy rate at (P<O.O5), and there was a tendency (P>O.O5) for WS supplement to increase pregnancy rate. The higher pregnancy rates when supplements were fed could be explained in terms of higher post-partum LW of these cows. The experiment demonstrated that dry lick supplements providing predominantly inorganic nutrients can have large effects to reduce LW loss of breeders during the dry season, increase LW gain during the later part of the wet season and to increase the pregnancy rate of lactating breeders. McCOSKER, T. and WINKS, L. (1994). 'Phosphorus Nutrition of Beef Cattle in Northern Australia' (Qld Dept of Primary Industries: Brisbane). 441