On ram performance

Press, Volume CXV, Issue 33774, 21 February 1975, Page 9

On ram performance

At this time of the year there wilt be interest in discussion on the ability of rams to serve ewes.

Dr A. J. Allison, a scientist of the Invermay agricultural research centre at Mosgiel. in writing to “The Press” last year on artificial insemination .in sheep. had something 'urther to say on this subject. “Providing ewes are run in small paddocks, then rams will cover very large numbers of ewes." he said. Referring to work done by Mr K. G. Haughey while with the Ashburton Veterinary Club in the 19505, Dr Allison said that mobs of about 300 ewes (ranging from 200 to 367) had each been mated with one ram. The rams used were of varying age and breed, but mostly Romneys and Southdowns. and were required to pass a semen test before use. Mr Haughey’s 1957 and 1958 data could he summarised as follows: No. of flocks 16 22 Mean flock size (ewes) - 293 295 Mean No. of ewes mated in 18 days 205 222 Mean No. of ewes settled 161 159 In giving these results Dr Allison said Mr Haughey had stressed that the mating performance of rams would be determined in part.by the number of ewes experiencing heat, which would depend on the time of the year. Those flocks starting mating earlier would have fewer ewes mated in the first 17 or 18day cycle after the rams went out. The figures in the table were mean figures and included some low results recorded in flocks which were mated early due to some ewes not having come into heat at the start of the breeding season. The data did, however, illustrate the fact that most rams were capable of mating with 200 ewes in a 17-day period.

Often after the first of his own trials, which involved groups of rams and not single sires, as with Mr Haughey’s work, and individual ram performance recorded with the use of different coloured crayons,

Dr Allison said such comments were heard as "well that may work on the wee paddocks at Invermay.” Dr Allison said that his trial work both on and off Invermay had involved more than 10.000 ewes, all individually identified and recorded, and 140 rams. Most of the work at Invermay had been on hill paddocks of 12 to 20 acres, but after the reaction mentioned a series of field trials had been done with five farmers at. different locations in Otago, where mobs of four or five rams were run with a group of ewes corresponding to the farmer's normal ram/ewe ratio. In addition a further group was included for comparison having twite as many ewes with the same number of rams. Complete mating data were collected on ail trials and the numbers of ewes pregnant was determined. Results were:

Dr Allison said that again crayon marks indicated that rams were mating a great many more ewes than the individual farmers had thought possible. These trials were all carried out on hill country and very conclusively demonstrated that conventional ram/ewe ratios could be reassessed. As most ewes would be mated in thd first 17 days of mating, particularly in a flock mating situation, if small paddocks were at a premium they need only be used for the first cycle. While paddocks of 20 acres or less would be preferable, perhaps even more important was that they should not have deep gullies or other natural obstacles which enabled groups of animals to become physically divided from each other. However at Tara Hills high country research station near Omarama flocks had been mated at one ram per 100 ewes on hill blocks of 400 or 680 acres without reducing the proportion of older ewes mated or affecting barrenness figures a great deal. It should nevertheless be stressed that two-tooth ewes would be much more sensitive to changes in mating management than older ewes and therefore in most cases would require more rams and should not be mated in association with older ewes in a flock mating situation. If farmers were using fewer rams and were concerned that a proportion of the flock might not be mated, they could use harnesses and record the results after the end of a cycle. If low numbers of

ewes were marked then the number of rams might be increased. Further detailed observations at Invermay in 1973 might also convince readers of the enormous reproductive potential of rams, said Dr Allison. Groups of four rams were mated for four days with groups of 240 (one to 60) or 720 ewes (one to 180) and then were removed and placed in a small paddock with a number of ewes known to be in heat corresponding to the number in heat in the respective mobs — 14 or 42 ewes respectively. These ewes were mixed with the same number of animals not in heat and were all individually numbered. The rams were watched continuously for eight hours and the numbers of ewes mounted and served were recorded. Two-, tooth and older rams were) compared and each group'

of rams was recorded at both ratios. Results were:— A (4 rams to 240 ewes, 14 ewes'in heat) Group Nd. No. Total rams ewes services served each each ram ram

This showed that rams could perform quite a number of services . . . Thus: on average in eight hours rams were performing 10 to: 14 services each in the easel of a one ram to 60 ewes ratio and from 9.3 to 25.8 services each where the ratio was one to 180 ewes. Dr Allison said that if this level of activity was maintained for 17 days or one oestrus cycle then the totals would be in the range of 500 to 700 (one ram to 60 ewes) and 470 to 1300 (one to 180) services for each ram.

After an initial very high level of mating activity in the first day after joining. with the ewes, the data ■ suggested a fairly constant | level of activity thereafter, ; until at least the end of the: first oestrus cycle.

Such figures illustrated the enormous reproductive potential of rams. It was also noticeable that two-tooth rams did not increase their mating activity as much as did older rams when the number of ewes was increased. How-

ever, where detailed observations were made in a twoacre paddock it was found that some rams were affected by competition and mated few ewes. In the larger mating paddocks the numbers of ewes marked per day was much larger indicating much less effect of competition. In the “New Zealand Journal of Agriculture” Mr Dobbie. of the Ruakura animal research station, had drawn attention to the possibility of reduced ewe fertility when two-tooth rams were used over large numbers of ewes. At Invermay and in the series of field trials mentioned earlier two-tooth rams had been used with no suggestion that they were less efficient. However, if farmers were worried that ewes would not be adequately covered by a lower number of rams the use of harnesses and colour crayons could be again advocated.

Ram/ewe ratio ' % Farm normal drv 1 4/160 1’9 2 4/300 13.3 3 5/150 12.9 4 4/200 2.1 5 5/250 3.6

Ram/ewe % ratio dry 4/320 9 9 4/600 76 5/300 9.3 4/400 4.3 5/500 1.0

1 4 2-ths 6.5 12.8 9 4 2-ths 6.3 10.0 3 4 6-ths 7.8 14.0 4 4 6-ths 7.5 10.8 B (4 rams to 720 ewes, 42 ewe in heat) Group No. No. Total rams ewes services served each each ram ram 1 4 2-ths 7.3 9.3 9 4 2-ths 10.5 12.8 , 3 4 6-ths 12.8 15.5 | 4 4 6-ths 17.5 25.8