Effect of varying periods of pre-calving nutrition upon the calving performance of Hereford heifers.

Abstract

Proc. Aust. Soc. Anim. Prod. (1974) 10; 59 EFFECT OF VARYING PERIODS OF PRE-CALVING NUTRITION UPON THE CALVING PERFORMANCE OF HEREFORD HEIFERS P.B. HODGE* and JANET STOKOE** Summary Calving performance of 84 two-year-old Hereford heifers was studied following three regimes of pre-calving nutrition. The criterion for superior calving performance was minimal incidence of dystokia and stillbirth. Treatments A (hay-fed for final 16 weeks of pregnancy) and B (hayfed for final-8 weeks of pregnancy) involved once daily feeding of rye grass/ clover hay at 5 kg per head until calving. This diet provided a submaintenance intake of both crude protein and energy. Treatment C heifers grazed a grass pasture throughout pregnancy until commencement of the calving The three treatperiod, when hay feeding at the 5 kg level was implemented. ments calved under identical conditions. There were no between treatment differences in pre-calving body condition and body weight changes of heifers, calf birth weights or calf body measurements. There was a significant correlation between calf birth weight and the incidence of either dystokia or stillbirth. When data were corrected for this birth weight correlation, the number of calves either involved in dystokia or stillbirth was significantly greater in Treatment A than Treatment B. There was also a significant correlation between calf birth weight and the incidence of dystokia alone. . It is inferred that illthrift factors associated with prolonged confinement and undernutrition were mainly responsible for this inferior A significantly smaller calving performance by the longer-fed heifers. pelvic area in the Treatment A heifers may also have contributed, although there was no statistical correlation between pelvic area and incidence of dystokia. I. INTRODUCTION the calving performance of pre-calving nutrition this paper was conducted October and November of of two(Hodge on the the An earlier investigation determined year-old Hereford heifers fed at three levels and Rowan 1970). The experiment reported in same property using similar heifers calving in following year. Three regimes of pre-calving feeding, namely hay feeding for the final 16 weeks and 8 weeks of pregnancy, and normal grazing throughout pregnancy, were examined for their effects upon calving performance. Dietary restriction of pregnant heifers has been proposed as a method Acceptof improving calving performance (Hodge and Rowan 1970; Young 1970). ing this hypothesis, this experiment aimed at defining which of two periods The of restricted hay feeding would give the better calving performance. criterion for superior calving performance was minimal incidence of dystokia and stillbirth. * ** Department of Primary Industries, Brigalow Research Station, Theodore, Qld. Department of Primary Industries, Animal Research Institute, Brisbane, Qld. 59 II. MATERIALS AND METHODS The property was located 60 km south-west of Miles in southern Eighty-four Hereford heifers Queensland (mean annual rainfall 660 mm). which had been paddock-mated to four Hereford bulls were allocated to the three treatments by stratified randomization based on fasted body weight Prior to hay feeding and pregnancy status during the first trimester. commencement, heifers shared common grazing. (a) Treatments Treatment A - 16 weeks of hay feeding - nil grazing. Two groups of 14 heifers were confined in 2 ha paddocks and groupfed once daily for the final 16 weeks of pregnancy on 5 kg of rye grass/clover hay per head. Treatment B - 8 weeks of hay feeding - nil grazing. Two groups of 14 heifers were confined in 2 ha paddocks and groupfed once daily for the final 8 weeks of pregnancy on 5 kg of rye grassjclover hay per head. Treatment C - normal grazing. One group of 28 heifers grazed a grass pasture of Bothriochloa, Dichanthium and Chloris species with Treatment A and B heifers until hay feeding commencement. Thereafter, Treatment C heifers continued to graze They were then confined the same pasture until the calving period commenced. in a 4 ha paddock and group-fed once daily on 5 kg of rye grass/clover hay per head to ensure that calving occurred under identical conditions in all treatments. lb) Observations The 8 and 16 week pre-calving feeding periods were calculated from pregnancy status estimations. Two veterinarians made independent estimates of pregnancy status and agreement between operators was of a high order. Hay feeding commencement was staggered by a fortnight between groups to ensure that actual duration of feeding was as near as possible to that intended. Treatment A groups commenced feeding on June 30 and July 14, while Samples of hay Treatment B groups commenced on August 25 and September 8. were analysed for dry matter and crude protein content (A.O.A.C. 1960). Fasted body weights of heifers were recorded at each feed change The after June 30 using the method described by Wiltbank et al. (1962). -m final body weights were recorded eight days prior to the onset of the calving period on October 6. Body condition scores were recorded in the first (April 22) and final (October 6) trimester of pregnancy according to the method of Winks and Lamberth (1968). Horizontal and vertical pelvic dimensions were measured with a Pelvic area was calculated from the product rectal calliper on October 6. of the horizontal and vertical measurements (Young 1968). Heifers were inspected at least three times daily to detect calving difficulty. Veterinary assistance was rendered if a heifer had not successfully calved within four hours of the appearance of the amniotic sac or a oetal extremity. Such cases were t.ermed dystok ias. Incidence of sti llbirths, heifer and calf mortality and retain ed pla cental membranes was recorded . As soon as possible after parturition calves were identified with their dams and measured for birth weight, head width, chest circumference, chest depth and body length. The heifers and their calves were then depastured on good quality feed. III. (a) RESULTS Hay analyses The rye grass/clover hay had a mean dry matter content of 88.3 per cent and a crude protein content of 12. 5 per cent on a dry matter basis. (b) Pre-calving data During the final 16 weeks of pregnancy there was a trend for Treatment A heifers to gain less body weight than the Treatment B. Treatment B gained at the lowest daily rate during the final 8 weeks of pregnancy although treatment differences were non-significant. Final pre-calving body weights were similar (Table 1). Although treatment differences in body condition at each observation were not apparent, there was a loss in body condition as pregnancy progressed (PxO.01): Treatment A heifers had a smaller mean pelvic area (WO.01) than either Treatment B ,or C heifers. Daily observation indicated that a proportion of the Treatment A heifers became listless and disinterested in their surroundings as hay feeding progressed. (c) Calving performance The calving period was 59 days in duration. Heifers calved a mean 5 days earlier than their estimated calving date based on pregnancy diagnosis. Treatment A heifers that had become listless and depressed during prolonged hay feeding appeared to calve with insufficient effort and endurance. Calf birth weights and body measurements for the three treatments Dystokia incidence was 17.9 were not significantly different (Table 1). per cent, 3.6 per cent and 10.7 per cent for Treatments A, B and C respectively. Stillbirth was also highest in Treatment A with 21.4 per cent, compared with 7.1 per cent for Treatment B and 3.6 per cent for Treatment C. Although there was a strong trend towards a higher incidence of dystokia and stillbirth in Treatment A, treatment differences for each of these criteria were not significant. Calf birth weight was significantly correlated with the delivery of calves which were either involved in dystokia,or stillborn (b = 0.027 + When data was corrected for this birth weight - SEb 0.013) (P<O.O5). correlation, the number of calves either involved in dystokia or still born was greater in Treatment A than Treatment B (P<O.O5). Calf birth weight was significantly correlated with dystokia incidence (b = 0.034 2 SEb 0.013) (P<0.05). Calves with heavier birth. weights required more assistance. However, calf birth weight was not Calf birth weight was also related to the likelihood of stillbirth. However, correlated with pelvic area (b = 0.104 + Ss 0.023) (P<O.Ol). there was no significant correlation between pelvic area and the incidence of dystokia. 61 TABLE1 Pre-calving and calving performance in three treatments In Treatment A two dystokias were considered to be due to foetopelvic disproportionx one due to foetal malpresentation and two due to maternal uterine inertia. The single dystokia in Treatment B was due to foetal malpresentation. All three dystokias in Treatment C were attributed to foeto-pelvic disproportion. One heifer in Treatment A gave birth naturally to fraternal twins, one of which was stillborn. This stillborn calf was omitted from the statistical analysis. Its dam was the only heifer in the experiment to retain membranes longer than twenty-four hours. Two heifers in Treatment A suffered from calving paralysis following the use of a Nicholson foetal extractor. One such heifer was recumbent for 10 days prior to recovery. Another heifer in Treatment A produced a grossly undersized dead calf at term which weighed 17.7 kg. Two heifers, one from Treatment B and one from Treatment C, died during parturition as a result of dystokia. Following dystokia, one calf in Treatment A and one calf in Treatment C perished at 4 and 2 days of age respectively. IV. DISCUSSION The hay level used was based on observation of heifer calving performance on different hay levels in the 1968 experiment (Hodge and Rowan 1970). The daily 5 kg of hay yielded 0.55 kg of crude protein and an estimated 2.75 kg T.D.N., supplying 80 per cent of protein requirements and 60.5 per cent of T.D.N. requirements (N-A.& - N.R.C. 1968). This T-D-N. estimate is based on levels quoted by Morrison for grass-legume hays of comparable quality (Morrison 1959). The pre-calving body weight performance of the grazing controls was inferior to that recorded on this property earlier (Hodge and Rowan 1970). This was attributed to the negligible herbage component in the pasture associated with below-average 1969 rainfall. It is considered that the similarity of pre-calving body condition and body weight movements accounted for the Similar mean calf birth sizes . between treatments. In spite of this similarity of calf birth sizes there was a higher incidence of both dystokia and stillbirth in the longer-fed heifers. Although these individual incidence differences between treatments were non-significant, Treatment A produced more dead or difficult births than Treatment B when data were corrected for birth weight (P<O.O5). Heavier calves were more prone to dystokia occurrence. The same result was demonstrated on this property in 1967 (Rowan, unpublished data) and 1968 (Ho.dge and Rowan 1970). It is inferred that the inferior calving performance of the Treatment A heifers can be mainly attributed to illthrift factors associated with prolonged confinement and under-nutrition. For instance, there may well have been prolonged partial restriction of exercise during the hay feeding period. Perhaps under-exercised heifers subsequently calve with less endurance. It seems unlikely that interference at calving was responsible for this inferior calving performance since all treatments calved under identical conditions (Dufty 1972). The smaller pelvic area of the Treatment A heifers may have been a contributing factor, although pelvic area was not correlated with dystokia incidence. The results of this experiment suggest that prolonged confinement and hay feeding of pregnant heifers, in order to restrict their diet, could be detrimental to calving performance. 63 V. ACKNOWLEDGEMENTS The authors wish to thank the staff of the Animal Research Institute for analysing the hay samples, and Mr M.R. Durand of the Department of Primary Thanks are also due to Industries for his assistance in paper preparation. This Mr W.D.S. Harpham who kindly made heifers and facilities available. experiment was conducted with financial support of the Commonwealth Extension Services Grant. VI. REFERENCES (Association of 'Official Methods of Analysis' 9th Ed. A.O.A.C. (1960). Official Agricultural Chemists: Washington). Aust. vet. J. 48: 1. DUFTY, J.S. (1972). Proc. Aust. Soc. Anim. Prod. g: 410. HODGE, P.B:, and ROWAN, K.J. (1970). (Morrison Publishing 'Feeds and Feeding'. MORRISON, F.B. (1959). Company: Clinton, Iowa). National Academy of Sciences - National Research. N.A.S. - N.R.C. (1968). Council Publ. 1137. WILTBANK, J.N., ROWDEN, W.W., INGALIS, J.E., GREGORY, K-E., and KOCH, R.M. (1962). J. Anim. Sci. & 219. Proc. Aust. Soc. Anim. Prod. 2: 159. WINKS, L., and LAMBERTH, F. (1968). Aust. vet. J. 24: 550. YOUNG, J.S. (1968). Proc. Beef Prod. Refresher Course, Sydney, 1970. YOUNG, J.S. (1970).