I have spent the morning in a rabbit hole, reading such articles as:
Mir, Fernando, Fontaine, Emmanuel, Albaric, Olivier, Greer, Marty, Vannier, Florence, Schlafer, Donald H, & Fontbonne, Alain. (2013). Findings in uterine biopsies obtained by laparotomy from bitches with unexplained infertility or pregnancy loss: An observational study. Theriogenology, 79(2), 312-322.
Moxon, Rachel, Whiteside, Helen, & England, Gary C.W. (2016). Prevalence of ultrasound-determined cystic endometrial hyperplasia and the relationship with age in dogs. Theriogenology, 86(4), 976-980.
Schlafer, D. (2012). Diseases of the Canine Uterus. Reproduction in Domestic Animals, 47, 318-322.
Smith, F. O. (2006). Canine pyometra. Theriogenology, 66(3), 610-612.
Veiga, Gisele Almeida Lima, Miziara, Ricardo Henrique, Angrimani, Daniel Souza Ramos, Papa, Paula Carvalho, Cogliati, Bruno, & Vannucchi, Camila Infantosi. (2017). Cystic endometrial hyperplasia–pyometra syndrome in bitches: Identification of hemodynamic, inflammatory, and cell proliferation changes. Biology of Reproduction, 96(1), 58-69.
There were more but that gives you the flavor.
Dr. So and So says that bitches should be bred early and often because repeated heat cycles are bad for uterine health. This gives people permission to breed dogs that are basically puppies — repeatedly.
And they do. When questioned, it is often “Dr. So and So recommends it.”
It is absolutely true that the cycle of bitches can cause cumulative and subtle uterine changes, and sometimes those changes can interfere with fertility — typically at later ages. It is also true that those changes do not usually cause infertility.
In a study of 240 bitches (Maxon, Whitehead, and England, 2016), 18.3% were diagnosed with Cystic endometrial hyperplasia (CEH), which seems to be the most frequent issue caused by the repeated impact of progesterone and estrogen on the uterus in dogs. The incidence was related to age — less than seven percent of dogs under three years of age were diagnosed with CEH but the incidence increases with age to over 50%. Again, dogs with CEH can and do get pregnant.
I will spare you the details but the bottom line seems to be this — breeding a bitch early and often is not really necessary. Uterine health is not going to pot before a bitch is two or even three.
There are some very good reasons to wait — letting the dog grow up is at the top of my list but other considerations include getting the requisite health clearances on the dog and her siblings, and assessing how her parents and grandparents fare as they age.
So that is conclusion #1 from this morning’s reading of peer-reviewed articles — breeding what are essentially adolescent dogs is not necessary (I will offer a caveat that there are rare exceptions in which scary uterine change are happening — I will also note [based on the literature] that may well be an inherited thing).
The second thing I was looking for was any information on back-to-back breedings, which is what I have done with Daisy. I cannot find anything definitive except yes, a back-to-back breeding reduces the hormonally-induced changes in her uterus (pregnancy is preventive). After the reading I did this morning, however, that is just not a significant concern.
Daisy was bred back-to-back (on successive heat cycles) for four reasons. First, there were no contraindications — in other words, doing so would not be bad for Daisy. Second, someone special needs a puppy from Daisy. Third, there is a pandemic and we are home — once the pandemic is done, I will not be inclined to take four months off to create, percolate, and raise a litter. Finally Daisy is really Bethany’s dog and once the little family is in a house with a yard, Daisy will go back to Bethany and Galen; that could be as early as this summer.
None of my dogs have ever had more than two litters — four have had only one litter and some have had zero litters. We breed occasionally but my primary focus is doing things with my beloved dogs, and as all moms know — pregnancy and young ones definitely change the trajectory of life for a while.
Appropriately enough, Daisy blooms when pregnant and she is a wonderful mom. But her pregnancy is Daisy’s second — and last. Limited Edition Puppies, indeed.