GENETIC DETERMINATION OF REPRODUCTION LEVEL TRAITS IN DAIRY CATTLE BREEDING

Modern cattle selection programs are characterized by the increase of traits with a low level of genetic determination. This change is associated to a technical means of verification capabilities (automated milking systems, behavioral video surveillance systems, control of rumination process, etc.), the success of genomics when selection based on genetic markers requires additional controls over the phenotypic changes. But the basic selection remains the production economy-based selection process. Recently, more features related to reproduction and productive longevity or animal health have been included in this group. A study was carried out on the effects of genetic and environmental factors on the voluntary waiting period, the open days and milk productivity. A new feature was identified – the insemination period which was defined as the difference between the length of the open days and the waiting period. Investigations were carried out on Holstein cows (605 heads in total), the average milk yield which amounted 8777 kg. The majority of the primary information was the data of the Uniform Agri program, which analyzed using variance and correlation-regression analysis. Weak probable impact of the «father» factor on the 305-day milk yield of lactation (11.5 %), the open days (5.4 %) and the insemination period (5.2 %) was identified. A positive, reliable and weak correlation was found between lactation milk yields and service period (0.115, p ≤ 0.01.), and between service period and voluntary waiting period (0.257, p ≤ 0.01). The dependence of the length of the service period and the voluntary waiting period on paratypic factors such as the age of cow’s lactation and the month of their calving is investigated. As such, a tendency to reduce the length of the open days and the voluntary waiting period in cows with each subsequent lactation. It is found that the length of the voluntary waiting period was the largest in cows that calved in November, March, May, and the shortest – in August. At the same time, cows that had calved in March was the largest the open days, and with calving in February – the shortest. It was concluded that the possibility of using the value of the insemination period in the selection programs. The possibility of using the traits of the level of reproduction in the selection programs has been proven.

Prevalence, survival and subsequent fertility of dairy and beef cows with uterine prolapse

The aim of this study was to evaluate the prevalence of uterine prolapse in cows and assess its effects on survival and subsequent fertility. Of 33,450 calving cows considered retrospectively, 216 (0.6%) developed uterine prolapse. A higher prevalence was found in beef cows (n = 57/5,700 cows, 1%) compared to dairy cows (n = 157/27,750 cows, 0.6%). Treatment consisted of cleaning and replacing the uterus with local administration of antibiotics, and applying a harness for uterine containment. The recovery rate was 81.9% (n = 177), similar in dairy (n = 129; 81.1%) and beef (n = 48; 84.2%) cows. Of the 216 cows with uterine prolapse, 18 (8.3%) died before or immediately after treatment; 21 cows (9.7%) were voluntarily culled for economic reasons (low milk yield, low fertility, insufficient weight gain). All recovered dairy cows were artificially inseminated with semen of proven fertility after a voluntary waiting period of 50 days; the beef cows were naturally mated. Among the 172 inseminated/mated cows, 84.7% (n = 150) became pregnant (83.7% dairy cows, 87.5% beef cows), while 15.2% (n = 27) did not conceive. Recurrence of uterine prolapse at subsequent calvings was recorded in one dairy cow. Based upon the data presented here, treated cows with uterine prolapse showed high chances of survival and conception, and a low risk of recurrence.

Effect of two prostaglandin injections on days 5 and 6 in a timed AI protocol after estrus expression on pregnancy outcomes in dairy cows during cold or hot seasons of the year

The objective of this study was to test whether prostaglandin (PG) injection on day 30 postpartum (pp) and detection of estrus can affect the efficacy of injecting PG on days 5 and 6 in the timed artificial insemination (TAI) protocol on pregnancy rate in a large dairy herd in hot or cold seasons. Out of 2235 cows, 1998 received an injection of PG at 30±3 d pp and estrus was observed. Cows that displayed estrus during the estrous observation period after PG injection were classified as estrus (E), while those that did not show estrus were classified as nonestrus (NE). Cows in each group were assigned to two treatments: CO-72 (control treatment) (ECO-72 and NECO-72) (day 44 GnRH, day 51 PGF2α, day 54 GnRH+TAI) or PG–PG (EPG–PG and NEPG–PG) (day 44 GnRH, day 49 PGF2α, day 50 PGF2α, day 52 GnRH+TAI). Pregnancy was diagnosed on days 33 and 47 after artificial insemination (AI). The proportion of cows in estrus on the day of TAI was higher (P≤0.05) for cows that received two PG than for cows that received one PG. Pregnancies per AI (P/AI) on days 33 and 47 for cows inseminated during and after a voluntary waiting period in the NEPG–PG treatment had higher rates than for cows in the EPG–PG, ECO-72 and NECO-72 treatments. Moreover, P/AI were significantly (P≤0.05) affected by parity. Primiparous had higher P/AI (37.0 %) than multiparous cows (31.6 %). Cows inseminated in cold months had higher P/AI and reduced PL (35.6 % and 20.8 %) than cows inseminated in hot months (29.1 % and 30.6 %, respectively). In conclusion, treatments with PG on days 5 and 6 after the first GnRH injection increased P/AI. Estrus detection before the beginning of TAI protocol did not affect fertility. To maximize P/AI cows exhibiting heat at any time during the synchronization protocol should be inseminated.