11 Invivo-derived embryo pregnancy rates at Maddox Dairy from 2008 to 2018
Authors: Demetrio D. , Magalhaes A. , Oliveira M. , Santos R. , Chebel R. 
Published: December 2019

Maddox Dairy, located in Riverdale, CA, USA, is a Holstein herd that milks 3500 cows with a 305-day mature-equivalent milk production of 12 800 kg, and they have been producing high genetic animals by embryo transfer (ET) since the early 1980s. Invivo-derived embryos from Holstein donors were transferred fresh (grade 1 or 2) or frozen (grade 1), at morula (4), early blastocyst (5), or blastocyst (6) stage, to virgin heifers (VH, natural oestrus, 13-15 months old) or lactating cows (LC, Presynch-Ovsynch, 86 days in milk, first or second lactation) 6 to 9 days after oestrus. Pregnancy diagnosis was done by transrectal ultrasonography at 32-46 days in VH and by the IDEXX PAG test at 30 days in LC. June, July, August, September, and October were called critical months (first service AI conception rate drops below 44%) and compared with the other months. The data from 32 503 ETs between January 2008 and December 2018 are summarised on Table 1. Pregnancy rates (PR) are lower for LC recipients than for VH. Embryo transfers performed 7 or 8 days after oestrus had higher PR in both types of recipients and embryos, but Day 6 and 9 oestrus are also used with fair results. The season does not seem to affect PR. There is not enough difference in the combination of stage and days from oestrus for invivo-derived embryos. These numbers do not belong to a planned experiment. Several management changes during the years were made, which make it very difficult to apply statistical methods to analyse the data correctly. They are used as a tool to make decisions in an attempt to improve future results.

Table 1.Pregnancy rate (PR) of virgin heifers (top) and lactating cows (bottom)-fresh (SH) and frozen (OZ) invivo-derived embryo transfer1

Heat-months
SH-ST4
SH-ST5
SH-ST6
SH-All
OZ-ST4
OZ-ST5
OZ-ST6
OZ-All

PR%
n
PR%
n
PR%
n
PR%
n
PR%
n
PR%
n
PR%
n
PR%
n

Heifers

6 d-CM
62
934
66
243
68
69
63
1246
56
473
58
219
62
42
57
734

6 d-OM
62
1623
67
489
69
211
64
2323
56
600
55
296
48
137
55
1033

6 d-T
62
2557
67
732
69
280
63
3569
56
1073
57
515
51
179
56
1767

7 d-CM
64
1506
68
495
67
221
65
2222
60
822
62
340
63
156
61
1318

7 d-OM
66
2723
68
1021
69
510
67
4254
57
1120
59
581
57
231
58
1932

7 d-T
66
4229
68
1516
69
731
67
6476
58
1942
60
921
60
387
59
3250

8 d-CM
65
1348
64
518
67
322
65
2188
59
595
64
258
63
108
61
961

8 d-OM
66
2166
68
886
70
510
67
3562
61
770
60
364
51
130
60
1264

8 d-T
66
3514
67
1404
69
832
66
5750
60
1365
62
622
56
238
60
2225

9 d-CM
60
109
56
43
70
20
60
172
60
5
33
6
50
4
47
15

9 d-OM
58
129
63
57
60
40
60
226
63
16
50
18
75
4
58
38

9 d-T
59
238
60
100
63
60
60
398
62
21
46
24
63
8
55
53

All-CM
64
3897
66
1299
67
632
65
5828
58
1895
61
823
63
310
60
3028

All-OM
65
6641
67
2453
69
1271
66
10 365
58
2506
58
1259
53
502
58
4267

All-T
65
10 538
67
3752
69
1903
66
16 193
58
4401
60
2082
57
812
59
7295

Lactating cows

6 d-CM
54
265
48
86
50
12
53
363
38
141
31
77
50
10
36
228

6 d-OM
49
463
52
203
45
56
50
723
46
101
48
54
59
27
48
182

6 d-T
51
728
51
289
46
68
51
1086
41
242
38
131
57
37
42
410

7 d-CM
54
755
59
274
56
103
55
1137
43
928
48
450
43
192
45
1570

7 d-OM
55
914
66
367
54
109
58
1393
46
1052
45
564
47
353
46
1969

7 d-T
55
1669
63
641
55
212
57
2530
45
1980
46
1014
46
545
45
3539

8 d-CM
63
252
68
82
76
33
65
368
48
219
56
80
42
33
50
332

8 d-OM
61
257
64
161
53
47
61
466
50
191
53
77
56
16
51
284

8 d-T
62
509
65
243
63
80
63
834
49
410
55
157
47
49
50
616

All-CM
56
1272
58
442
60
148
57
1868
44
1288
47
607
43
235
45
2130

All-OM
55
1634
62
731
51
212
56
2582
47
1344
46
695
48
396
47
2435

All-T
55
2906
60
1173
55
360
57
4450
45
2632
47
1302
46
631
46
4565

1ST=stage; CM=critical months (June, July, August, September, and October); OM=other months.