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Endometritis is one of the causes associated with low reproductive efficiency in dairy cattle. This study evaluated the prevalence of subclinical endometritis (SE) in three dairy herds in Puerto Rico during both hot and cool seasons. In cows at 45±7 days post-partum, SE, defined as the presence of ≥5% of polymorphonuclear cells in samples of endometrial tissue, was determined by cytology. The overall prevalence of SE (n=101 cows) was 8.9% and no significant effects were found of breed (P=0.73), season (P=0.34), number of lactations (P=0.60), nor location (P=0.56). For Holsteins, Brown Swiss, Jersey and crossbred cows the prevalence of SE was 10.4, 18.7, 0, and 6.3%, respectively. Primiparous cows showed a value of 7.1% SE and multiparous, 10.2%. During the hot season the prevalence of SE was 6.1% versus 11.5% for the cool season. At the dairies located in Moca, Lajas and Camuy the condition was detected in 5.5%, 6.6% and 12.0% of the cows, respectively. Compared to studies conducted in other countries, the present results indicate that SE is relatively well under control in the local dairy herds studied.

The slick-hair phenotype in cattle is due to one of a series of mutations in the prolactin receptor (PRLR) that cause truncation of the C-terminal region of the protein involved in JAK2/STAT5 activation during prolactin signaling. Here we evaluated whether the inheritance of the SLICK1 allele, the first slick mutation discovered, is inherited in a fashion consistent with Hardy-Weinberg equilibrium. It was hypothesized that any deleterious effect of inheriting the allele on embryonic or fetal function would result in reduced frequency of the allele in offspring. A total of 525 Holstein and Senepol cattle produced from matings involving one or both parents with the SLICK1 allele were genotyped. The observed frequency of the SLICK1 allele (0.247) was not significantly different than the expected frequency of 0.269. These results support the idea that inheritance of the SLICK1 allele does not act in the embryo or fetus to modify its competence to complete development to term.

The efficacy of the anthelmintic albendazole (ALB), doramectin (DOR) and ivermectin (IVM) were evaluated in Holstein and Holstein crossbreed dairy heifers using the fecal egg count reduction test (FECRT). Dairy heifers (n=420; ~6 months of age; BW = 149 ± 39.6 kg) were evaluated in 21 dairy farms. All heifers were required to be on pasture and not have been exposed to anthelmintic treatment for a minimum of 3 months. At each dairy farm, a priori, groups of at least 18 heifers were randomly divided to be treated with IVM, or DOR, or ALB following manufacturer's instructions. Fecal samples were collected directly from the rectum 7 days before anthelmintic treatment (d-7), at the time of the treatment (d0), and 14 days after treatment (d14). Only heifers that had an average FEC ³ 100 eggs per gram of feces (average of FEC from day d-7 and d0) were considered in the FECRT. The FECRT was determined by the modified McMaster technique. Of the three-anthelmintic used, ALB (n=142) proved to be the most effective (P < 0.0005) with an efficacy of 67.47% ± 8.43. The efficacy of DOR and IVM did not differ (P = 0.8713). While DOR (n = 130) exhibited a efficacy of 25.50% ± 18.00, IVM (n = 148) exhibited a efficacy of -8.13% ± 19.89 due to an increase in FEC after treatment. Dairy farmers should implement integrated methods of nematode control to preserve the effectiveness of currently available anthelmintics.

To demonstrate that the Holstein cow population of Puerto Rico presents differences in hair coat characteristics, hair samples were obtained from the rump, ribs and shoulder of cows visually characterized either as short (SH) or normal haired (NH). Hair length and width were measured and correlated with the genetic potential of cows for these traits: duration of productive life, dairy conformation, pregnancy rate, milk production, milk fat, and somatic cell count (SCC). The cows henotypically identified as SH had shorter but wider hairs than NH cows. Length of hair from the rump and ribs was inversely correlated with productive life duration and directly correlated with SCC. In addition, width of the rump and rib hair was directly correlated with milk production but inversely correlated with productive life. This variability in hair coat length and width of Holstein cattle in Puerto Rico may affect productive traits. Identification of Holstein cattle with SH phenotype should continue, thus to facilitate further genetic evaluation of this trait with the goal of improving efficiency of the local dairy industry.

In search of alternative indicators of fertility in bulls, this research evaluated the effects of breed, type of cattle and age on the relative expression of the genes aromatase, pregnancy-specific beta-1-glycoprotein (PSG1), and nitric oxide synthase (NOS) In bovine semen. Sperm from Jersey, Holstein. Brahman, Brangus, Charolais, Charbray, Senepol, and Simmental bulls was collected and the extracted mRNA was analyzed for expression of the genes using real time polimerase chain reaction (RT-PCR). The relative expression of aromatase was lower (P 0.07) In sperm from Jersey bulls (0.89) than in bulls of all other breeds (average 1.01). The relative expression of PGS1 was greater (P 0.02) in sperm from dairy (1.00) than from beef bulls (0.96). Age did not affect relative expression of the genes under study. Additionally, in data from 31 bulls, expression of NOS was positively correlated with scrotal circumference (r = 0.31; P 0.08). As far as we know, these are the first results showing that the genes aromatase, PSG1 and NOS can be detected in bull sperm and may have implications as molecular markers for bull fertility.

Ivermectin (IVM) resistance of Cooperia spp. in dairy heifers from Puerto Rico was evaluated using the larval migration inhibition assay (LMIA). In eight of the farms where anthelmintic resistance had previously been evaluated using a fecal egg count reduction test (FECRT), third stage larvae (L3) were recovered from fecal cultures prior to the administration of IVM treatment. The effective concentration at which 50% of larval migration is inhibited (EC50) was determined in susceptible and resistant Cooperia spp. isolates from one farm. The susceptible and resistant isolates had an EC50 of 0.7224 uM and an EC50 of 7.0778 uM, respectively. This indicates that on average, larvae from the resistant isolate are 10X more resistant than those from the susceptible isolates. However, the LMIA was unable to discriminate consistently between susceptible and resistant larvae obtained from dairy farms evaluated. In one case, an EC50 value of 0.7263 uM, which is close to that of the susceptible isolate, did not agree with the FECR result of -136.19% documented on this farm. In two additional instances the assay was unable to discriminate between susceptible and resistant isolates. Indeed LMIA EC50 values obtained from some resistant isolates were lower than the EC50 value from susceptible isolates, whereas their FECRT results indicated that resistance to IVM was present. Possibly, the FECRT could have given a false positive for macrocyclic lactones resistance at these two farms. Therefore, more studies are needed to validate the effectiveness of the LMIA to detect anthelmintic resistance to macrocyclic lactones in Cooperia spp. larvae isolated from bovine fecal field samples.