Nutritional requirements and productivity of single pregnant and lactating cows with twin or single calves.

Abstract

Proc. Aust. Soc. Anim. Prod. Vol. 18 NUTRITIONAL RIEQUI REMENTS AND PRODUCTIVITY OF SINGLE PREGNANT AND LACTATING COWS WITH TWIN OR SINGLE CALVES J.F. GRAHAM*, L.J. CUMMINS*, A.J. CLARK* and K.A. LANG'AT* In 1987 and 1988 single and twin bearing autumn calving Hereford and crossbred heifers were individually fed during the final two months of pregnancy and the first two months of lactation. The heifers, live weight 422 + 7.2 kg and 525 fi 11.2 kg (mean + s.e.) respectively were fed rations adjusted weekly according to blood ketone (BOH) levels. During pregnancy, cows carrying twins tended to have a higher energy requirement, in 1988 twin and single bearing cows In both years, consuming 91.3 and 80.9 MJ ME/cow/day respectively (P<O.O5). cows rearing twins were fed 21% more energy post calving than cows rearing single calves, 1.11, 0.92 and 0.99 and 0.82 MJ ME/kg LW''/day for 1987 and 1988 respectively (P<0.05). Whilst calf growth rate in both years was significantly lower for the twin calves, their combined growth rates were no worse than the single calves in 1987 and in 1988 their combined growth rates were significantly greater than In 1988 the combined weaning the single calves (1.03 and 0.72 kg/calf /day). weight of 456.8 kg for those twin calves was significantly greater than 243.5 kg for the single calves. Although there was no significant difference in milk production in 1987, in 1988 twin-rearing cows produced significantly more milk, 8.11 and 4.95 kg/cow/day respectively. INTRODUCTION Compared to other meat production inefficient. In U.S.A. over 50% of maintenance of the breeding cow. Under only 50 to 70% of her body weight as al. 1988). Thus, increasing the maintenance, should increase beef herd systems the beef herd is relatively the herd feed supply is required for normal conditions the beef cow produces marketable progeny per year (Gregory et cows reproductive rate, relative to efficiency. This paper reports preliminary experiments on the relative energy requirements of twin and single rearing cows and related production responses. The approach has been based on the assumption that elevated BOH concentration in the blood may provide a quantitative assessment of energy deficits. This has been well documented in sheep (Russel 1977) and also appears to be the case in cattle (Russel and Wright 1983). This approach was necessary because of uncertainty as to which cows would bear twins. MATERIALS AND KETHOD In 1987, 22 pregnant predominantly Hereford autumn calving heifers were selected from a group of 80 that were previously treated with pregnant mare serum gonadotrophin (PMSG). Nine cows pregnant to first service were treated as potential twin or multiple bearers. In 1988 embryo transfer and PMSG were used to produce twins and 21 predominantly crossbred heifers were selected, seven were initially diagnosed as having multiple pregnancies. 1% both years commencing in January all animals were individually fed by means * Department of Agriculture and Rural Affairs, P.R.X. Hamilton, Vic. 3300. 216 Proc, Aust. Soc. Anim. Prod. Vol. 18 of electronic doors. In 1987 a ration of wheat plus lucerne cubes was fed, with respective dry matter (DM) content 88.0 and 88-O%, crude protein (CP) 11.3 and 16.6% and estimated metabolizable energy content (ME)(MJ/kg DM) 13.0 and In 1988 lucerne cubes of similar chemical content were used with 8.4%. triticale, CP of 11.9%, DM of 87.1% and ME of 13.2 MJ/kg DM. All animals were fed daily rations, initially calculated using metabolic live weight (MAFF 1976), and subsequently were adjusted weekly according to the concentration of blood ketones as measured by serum B hydroxybutyrate concentration.(BOH). In 1987 the aim was to keep BOH between 0.4 and 0.7 mmol/l, while in 1988 a target Animals were randomly allocated to feed-lots and of 0.6 mmol/l was chosen. feeding doors, but after calving, twin rearing cows (T) were put into the same group to minimise cross suckling with single rearing cows (S). Milk production was measured using machine milking in 1987 and machine and the weigh-suckleMeans of results within years were compared using weigh technique in 1988. Student's t test. RESULTS Figures were calculated on a weekly basis with respect to the date of calving, so that comparisons could be made between animals at a similar stage of pregnancy or lactation. Results are presented in Table 1 and Fig. 1 for cows either bearing or rearing twin and single calves. Table 1 Production variables of single and twin bearing cows before and after calving in two years 217 Proc. Aust. Soc. Anim. Prod. Vol. 18 Cow liveweight changes Liveweight change pre-calving was These are shown in Table 1 and Fig. l(a). similar in both years for both groups, the T cows in 1987 gaining slightly more. Post-calving, the T cows in 1987 gained significantly more weight than In 1988 the weight loss of the T cows was only marginally the S cows (P~0.1). greater. In both years calving weight loss was higher in the T groups, being highly significant in 1988 (P~0.01). Energy intake Pre-calving ME intake tended to be higher for the T cows, but a significant Energy intake post-calving was difference was detected only in 1988 (P<O.OS). 21% higher with the T cows in both years (P<O.OS) - Fig. 1 (b). BOH levels In 1987 BOH levels largely fell within Levels of BOH are shown in Fig. l(c). However in 1988 levels measured in the the target range of 0.7 to 0.4 mmol/l. T-cows were higher in the period six weeks until two weeks prior to calving Just prior to calving BOH levels were similar in (P~0.05 weeks six and two). During week four of lactation in 1988 BOH levels of the T cows both groups. were also elevated (P<O.OS). 218 Proc. Aust. Soc. Anim. Prod. Vol. 18 Calf gro&h rate and milk production In both years the P<O.OS, Fig. l(d). total progeny live significantly more was no significant milk production of produced 63.8% more single calves grew significantly faster than the twins, However in 1987 there was no significant difference in weight at six weeks, and in 1988 the twin cows produced At weaning in 1988 there live weight at six weeks (P<O.Ol). difference in live weight of the individual calves. In 1987 However in 1988 the twin group the two groups was similar. milk (8.11 v 4.95 kg/24 h, P~0.01). DISCUSSION The BOH levels responded quickly to changes in energy intake. In both years the pattern of cow liveweight change was similar for both groups. However after examining 1988 BOH levels, and the pre-calving liveweight change in relation to total calf birthweight, it seems that the T cows may have been energy deficient Had pre-calving, and should have received a higher allowance at that stage. feeding been increased to decrease BOH to levels similar to that of the S cows, the differences in ME intake between the two groups would have been greater, and would have resulted in greater liveweight changes pre calving for the twinproducing cows in 1988, Although ME intake post-calving was significantly greater with the twin-rearing compared to the single rearing cows, the energy was partitioned differently in In 1987 the extra energy consumed by the T cows seemed to be both years. partitioned towards cow weight gain and not towards increased milk production Fig. 1 (a)- The extra energy intake of the T cows in 1988 could be attributed The extra 15 MJ ME/day is to the extra milk production of that group. equivalent to 3-11 kg milk (1 kg milk = 4.94 MJ ME, MAFF 1976), and these cows The cows in 1988 had a higher produced 3.16 kg more milk than the singles. milking potential than those in 1987. The BOH concentrations of the T cows in 1988 were raised slightly in weeks three to six post-calving compared to those This indicates that they should have had a higher energy of the S group, intake for that period, which would have increased the extra energy required by these cows beyond the 21% shown in these figures, even though they lost less weight post-calving. Even though the calf growth years, when total progeny rearing dams was favourable. in 1988, the twin calves significant differences in produced by one dam. rates of the twins were significantly lower in both live weight was examined, production from twinWhen looking at the weaning weights of the calves compensated, so that by weaning there were no live weight, resulting in twice the live weight used, this study does the twin-rearing cows, and providing the dams dams) twinning should In spite of the small number of twin rearing cows indicate that providing adequate nutrition is given to (approximately 20% extra needed pre- and post-calving) chosen have a high milking potential (e.g. crossbred result in increased efficiency of meat production. ACKNOWLEDGEMENTS The AMLRDC provided financial support. REFERENCES GREGORY, K-E., ECHTERNKAMP, SE., DICKERSON G-E., CUNDIFF, L.V. and KOSCH, R-M. (Clay Centre: Nebraska). (1988). Beef Research Progress Report 3:2X M,A,F,F, (1976). Technical Bulletin 33. (H.M.S.O.: London). RUSSEL, A.J. (1977). Livest. Prod. Sci. 11: 429. RUSSEL, A-J, and WRIGHT, A. (1983). Anim. Prod. 37~335. 219