Abstract:
THE EFFECT OF CHANGES IN THE DAILY PHOTOPERIOD ON THE SEMEN CHARACTERISTICS OF THE MERINO RAM ByD.G. FOWLER* Summary Bi-weekly observations were made on the semen characteristics of two groups of Merino rams. One group was subjected to a reversed pattern of seasonal lighting, the other to normal seasonal lighting. Highly significant (P < O=Ol ) season x treatment interactions were observed. The semen quality of the treatment rams was higher during spring 1960, and lower during autumn 1961, than the control semen. Highly significant seasonal effects present, irrespective of light treatment, indicate the effect of some other environmental influence. This is suggested to be ambient temperature. The effect of the daily photoperiod on reproductive activity has been extensively studied and is the subject of a number of reviews (Marshall 1936, 1942; Zuckerman 1952; Yeates 1954). Among the domestic species, however, the male has been relatively little studied. This communication presents results of an investigation involving the reversal of the daily photoperiod for a group of Merino rams. On September 12, 1960, twelve 1 &month-old rams were introduced to two light-controlled rooms. The reversal of the daily photoperiod commenced in Room 1 on October 3, 1960, and proceeded according to the pattern outlined in Fig. 1. In Room 2, rams were subjected to normal seasonal lighting. 16 II. MATERIALS AND METHODS I. INTRODUCTION Hours 12 of Daylight ` 0 \ \ I 0 0 8 t -am) I Treatment I I I I I --I I I t Control J F M A M J J A S 0 N- D 1960 1961 Fig. l-control and treatment light patterns. * N.S.W. Department of Agriculture, Trangie Agricultural Research Station. 58 ` TABLE 1 MEAN MONTHLY VALUES OF SEMEN CHARACTERISTICS OF TREATMENT AND CONTROL RAMS Characteristic Longevity at T 37OC in months C Percentage of T morph. normal spermatozoa C Percentage of live spermatozoa concentration of sperm/ml x lo9 No. of sptrm/ejac. x lo9 T C T C 27 Sept. 407 460 88-5 91-9 74*9 24 Oct. 183 217 29 Nov. 245 264 83 -7 54.9 3 Jan. 150 228 73.5 71*7 68.6 62-8 3-328 29220 4.914 4.828 23 Jan. 246 263 72aO 6OaO 58.6 74~6 3.124 20 Feb. 278 279 42-l 80-8 24-6 61-9 1.984 20 March 294 336 41.3 76e5 47-2 86-7 l-424 3 0079 2.275 8*617 17 April 223 244 65-l 759 34-4 77-8 2.767 3 l 574 5.144 8.836 16 May 305 217 66-4 47*9 62-3 7195 2-760 2.735 69 176 5.373 14 June 175 19 July 225 303 218 -79.0 79.9 74.2 40.0 71*0 3.460 l-875 5-143 4-843 73*6 63-5 ----57*4 4*530 3.605 9-733 8.744 s 65.3 84.5 4.648 2 -943 10.727 4.971 53-3 48-O 77-l. 3 0968 3 -780 -2.773 l-948 6,470 3 a473 T 5.289 4.551 C 2.555 2.767 ~-6.484 4,393 4.639 7*616 Semen was collected by electro-ejaculation at bi-weekly intervals, observations being made on: (a) Semen volume. (b) Initial motility, scored objectively. (c) Initial seminal pH (Universal indicator). 3eo SEMEN 2.0 VOLUME 5 4 3 MOTILITY 2 I 0i 7. 0 PH 6.0 i I I k I I I 1 I S r 6N 1960 I I D I J F M AM 1961 J 3 Fig. 2-Mean G-weekly values of semen volume, motility and pH. 60 At each second collection, observations were also made on: (d) The longevity of the spermatozoa in Ringer phosphate buffer solution at 37OC. ( e` Spermatozoa1 concentrations (Haemocytometer measurement). J (0 The percentage of live and dead spermatozoa (Blom 1950). (g) The percentage of morphologically normal and abnormal spermatozoa. III. RESULTS . The mean monthly values of percentage of live spermatozoa, percentage of morphologically normal spermatozoa, concentration of spermatozoa/ml, and sperm number, are presented in Table 1. Fig. 2 outlines the mean b&weekly values of spermatozoa motility. These characteristics show highly significant (P < 0.01) season x treatment interactions. The treatment group gave lower values of motility, percentage of morphologically normal spermatozoa, concentration/ml and sperm number, during the period February 20 till April 17, 196 1. The percentage of live spermatozoa was lowest in the treatment group during the period January 23 till June 14, 1961. Furthermore, the semen produced by the treatment rams showed a higher percentage of morphologically normal spermatozoa during November 1960, and a higher sperm number and concentration of spermatozoa/ml during the period October 24, 1960, till January 23, 1961. The mean b&weekly values of semen volume and monthly means of spermatozoa longevity are presented in Fig. 2 and Table 1 respectively. Significant (P < 0.05) treatment effects were indicated, the treatment group producing a lower volume of semen during March, April, and June 1961, and exhibiting a lower spermatozoa longevity during January 1961. Highly significant seasonal effects were present, the semen of all rams exhibiting a higher initial pH during the summer months, a higher longevity during February and March than during adjacent months, and a greatly reduced motility during February 196 1. IV. DISCUSSION These results suggest that reversal of the daily photoperiod caused a reversal of the seasonal cyclic changes in Merino ram semen quality. During spring 1960 the semen of the treatment rams gave higher values of morphologically normal spermatozoa, sperm number and concentration of sperm/ml, than control rams. Throughout the autumn months of 1961 the semen quality of the treatment rams was lower than the semen of the control rams. These results receive support from the work of Moule ( 1950), who demonstrated a marked increase in libido of Merino rams subjected to decreasing hours of daylight during the spring. Also Yeates ( 1949) provides data suggesting that the reversal of the daily photoperiod for Suffolk x Border Leicester-Cheviot rams reversed the seasonal cyclic changes in semen quality. Sapsford ( 195 1) was unable to attribute seasonal changes in Merino ram semen quality to either nutrition or environmental temperature, and suggested seasonal variation in the hours of daylight as an explanation of his results. 61 The significant seasonal efTects present, irrespective of light treatment, indicate the influence of an environmental factor other than day length. This is most likely environmental temperature, and a continuation of observations during the summer of 1961-62 will test this hypothesis. The demonstration of the influence of seasonal variation in the hours of daylight on Merino ram semen quality is the chief significance of this work. On many properties, however, housing of rams is normal practice, and consideration can be given to modification of the light environment to achieve maximum fertility of the rams at mating. V. REFERENCES E. (1950).-Nord. Vet. Med. 2: 58 . , F. H. A. (1936).-Phil. Trans. Roy. Soc. London B226. M ARSHALL , F. H. A. (1942).-Biol. Revs. Cambridge Phil. Soc. 17: 68. M OULE , G. R. (1950).-Aust. Vet. J. 26: 84-87. M OUL E, G. R. (1950).-Aust. Vet. J. 26: 148. S A P S F O R D, C. S. (1951). -Aust . J. Agric. Res. 2: 33 1-341. Y EATES , N. T. M. (1949).-J. Agric. Sci. 39: 1. YEATES, N. T. M. ( 1954) l -4`Recent progress in the Physiology of farm animals.' (J. Hammond, Ed.) Vol. I, pp 363. Z U C K E R M A N , S. (1952).-Ciba Collog. Endocrinol. 4: 23. B LOM , M ARSHALL 62