Abstract:
Animal Production in Australia Vol. 15 PRODUCTION CHARACTERISTICS OF RAMS GIVEN SUPPLEMENTS CONTAINING DIFFERENT LEVELS OF PROTEIN AND METABOLISABLE ENERGY J.B. Rowe* and P.J. Murray* SUMMARY A series of three trials was conducted to investigate the nutritional requirements for optimal testicular growth in rams. Measurements were made of liveweight, wool growth and scrotal circumference in rams given a range of dietary treatments (n = 5 per treatment, in individual pens). In all experiments there was a control group fed 1 kg pelleted diet (approx. 70 cereal grain : 30 straw) to maintain liveweight, and a group supplemented with 750 g lupin/d. The remaining treatments provided supplements of varying ME and protein content. There was an asymptotic relationship between liveweight gain and testicular growth with maximum change in testicular volume (3.4 ml/d) achieved at growth rates of approximately 200 g/d. There was no relationship between wool production (protein status) and testicular growth. INTRODUCTION Although it has been demonstrated that undernutrition of rams results in decreased testicle volume and sperm production (Parker and Thwaites 1972, Alkass et al. 1982), the specific nutritional requirements when feeding above maintenance in order to increase testicle size are not clearly defined. The data of Braden et al. (1974) indicate that high levels of dietary protein are not required to increase daily sperm production. On the other hand Oldham et al. (1978) suggested that more than half of the variation in testicle growth could be accounted for by the protein status of the animal as measured by nitrogen balance. The objective of the studies reported here was to investigate the role of protein and energy, provided as supplements to a basal maintenance diet, on the rate of testicle growth. Changes in liveweight were measured to confirm the efficiency of supplementary metabolisable energy (ME) utilization for growth and wool production was monitored as an index of protein status. MATERIALS AND METHODS A series of three experiments was conducted. The first trial started in June and terminated in August 1982 (49d). The second and third trials were carried out from October to December 1982 and from March to May 1983 respectively (both 42d). Eighteen Merino rams (six years of age) were selected Animals and feeding from the Wongan Hills Research Station culls on the basis of having sound mouths and no detectable abnormalities of the testes. All animals were dehorned and fitted with indwelling abomasal cannulae six weeks before the first experiment. During the post-operative recovery period animals were introduced to a pelleted diet containing (g/kg) : oats, 230; barley, 230; wheat, 200; oat hay, 300; and minerals and vitamins, 40. For three weeks before each experiment the animals were housed individually and fed a ration of 1 kg pellets/d. * Department of Agriculture, Jarrah Road, South Perth, W.A. 565 Animal Production in Australia Vol. 15 In basis. similar assigned from 55 all experiments animals were allocated to treatments on the same Five replicate groups, each of three rams, were formed on the basis of scrotal circumference and liveweight. Within each group animals were to experimental treatments at random. Mean initial liveweight ranged to 60 kg for all experiments. In Experiment 1 the animals were held in metabolism cages. In Experiments 2 and 3 they were held in individual pens on a slatted floor. Drinking water was freely available. Dietary treatments A basal maintenance ration of 1 kg pellets/d was fed to each animal on all experimental treatments. Two treatments were common to the three experiments: the maintenance, control diet and supplementation of this maintenance ration with 750 g lupin grain/d. These served as negative and positive controls to evaluate the responses due to the third treatment and to account for any seasonal differences in testicular growth. The 'test' treatments studied in the three experiments are summarized below. Experiment 1. The equivalent amount of protein to that consumed in 750 g lupins (236 g/d) was infused directly into the abomasum as a solution of casein. Glucose (112 g/d) was included in the infusate. Experiment lupins was vegetable (236 g/d) glucose. 2. The given in oil (60), providing The other equivalent amount of ME and protein contained in 750 g purified forms. ME was provided as (g/d); glucose (112), sodium acetate (127), and sodium propionate (64). Casein both protein and ME was infused into the abomasum with the sources of ME were mixed in the diet. Experime nt 3. Bar ley grain was fed (800 g/d 1 toprovide approximately the same ME intake and about 30 per cent of the addi tional pr,otein. Testicular volume In all experiments the scrotal circumference was measured at the point of greatest diameter at weekly intervals. In Experiment 1, estimations were also made using the comparative palpation technique described by Oldham et al. (1978). At the termination of Experiment 3 the animals were slaughtered and the volumes of each testis and epidiymis measured separately by water displacement. Liveweight Animals were weighed at weekly intervals. The relationship between liveweight change and testicular growth obtained in these experiments was compared with the data of Lindsay et al. (1976) and Oldham et al. (1978). =T= 100 cm patch This was estimated from the amount of clean wool produced from a on each side of the animals. RESULTS The feed intake and measurements of production for the three experiments are summarized in Table 1. In Experiment 1 there were significant (P < 0.05) increases in liveweight gain, scrotal circumference and wool growth as a result of supplementation of the basal diet with lupin seed. In response to an intra-abomasal infusion of casein and glucose there was a significant (P < 0.05) increase only in wool production. Testicular growth was not changed by the additional protein and glucose given via the abomasum. 566 Animal Production in Australia Vol. 15 TABLE 1 Feed intake, daily liveweight change, testicular growth and wool production measured in three experiments using 15 rams In Experiment 2 there were highly significant (P < 0.001) liveweight gain in response to supplementation with lupins and intra-abomasal infusion of mixed energy substrates and casein. production and testicular volume were increased as a result of treatments the differences were not statistically significant 0.16, respectively). increases in also to the Although wool these (P = 0.08 and In Experiment 3 there was a significant (P < 0.001) increase in liveweight gain in response to supplementation with lupins or barley. There were similar increases (P = 0.06) in scrotal circumference in animals on these supplements but wool production was increased only in animals given lupin seed. Daily liveweight change (g/d) Animal Production in Australia Vol. I5 There was a close relationship between testicular volume (Y, ml) measured at slaughter and the scrotal circumference (X, cm) given by the equation: R2 = 0.89. Y= 42.2 x - 993 The relationship between daily liveweight gain and change in testicular volume was asymptotic with maximum testicular growth achieved (3.4 ml/d) in rams gaining around 200 g/d. These data were compared with those reported by Lindsay et al. (1976), and Oldham et al. (1978) and are summarised in Fig. 1. No relationship was observed between wool production and testicular growth. In all trials there was a close relationship between the estimated amount of ME consumed and the rate of liveweight gain. DISCUSSION It appears from the data presented here that testicular growth may be closely related to the rate of liveweight change (and therefore ME intake) rather than to the protein status of the animal as monitored by wool production. This observation is consistent with the conclusions of Braden et al. (1974) who found that sperm production could be increased by additional digestible organic matter in the diet but did not in response to protein supplementation. The data of Lindsay et al. (1976) and Oldham et al. (1978) provide additional evidence for the relationship between the rates of change of liveweight and testicular volume over a wide range of liveweight change (-300 to 350 g/d). The earlier suggestion, that the high rate of testicular growth in rams given lupins, was related to the nitrogen status of these animals could have resulted from the supplement providing both protein and ME (producing significant growth responses). Grazing sheep given supplements of lupin grain appear to grow faster than animals given cereal grain. The question of whether this is due to a more balanced supply of crude protein and ME or because of the different carbohydrate composition of the two grains is currently under investigation. REFERENCES ALKASS, J.E., BRYAND, M.J. and WALTON, J.S. (1982). Anim. Prod. 2:265 (1974). Aust BRADEN, A.W.H., TURNBULL, K.E., MATTNER, P.E. and MOULE, G.R. OLDHAM, C.M., ADAMS, N.R., GHERARDI, P.B., LINDSAY, D.R. and MacKINTOSH, J.B. (1978). Aust. J. Agric Res. 29:173. PARKER, G.V. and THWAITES, C.J. (1972). Aust. J. Agric Res. 2:109. 568